OpenLDAP Software 2.4 Administrator's Guide

The OpenLDAP Project <http://www.openldap.org/>
29 September 2014


Table of Contents


Preface

Copyright

Copyright 1998-2012, The OpenLDAP Foundation, All Rights Reserved.

Copyright 1992-1996, Regents of the University of Michigan, All Rights Reserved.

This document is considered a part of OpenLDAP Software. This document is subject to terms of conditions set forth in OpenLDAP Software Copyright Notices and the OpenLDAP Public License. Complete copies of the notices and associated license can be found in Appendix K and L, respectively.

Portions of OpenLDAP Software and this document may be copyright by other parties and/or subject to additional restrictions. Individual source files should be consulted for additional copyright notices.

Scope of this Document

This document provides a guide for installing OpenLDAP Software 2.4 (http://www.openldap.org/software/) on UNIX (and UNIX-like) systems. The document is aimed at experienced system administrators with basic understanding of LDAP-based directory services.

This document is meant to be used in conjunction with other OpenLDAP information resources provided with the software package and on the project's site (http://www.OpenLDAP.org/) on the World Wide Web. The site makes available a number of resources.

OpenLDAP Resources
Resource URL
Document Catalog http://www.OpenLDAP.org/doc/
Frequently Asked Questions http://www.OpenLDAP.org/faq/
Issue Tracking System http://www.OpenLDAP.org/its/
Mailing Lists http://www.OpenLDAP.org/lists/
Manual Pages http://www.OpenLDAP.org/software/man.cgi
Software Pages http://www.OpenLDAP.org/software/
Support Pages http://www.OpenLDAP.org/support/

This document is not a complete reference for OpenLDAP software; the manual pages are the definitive documentation. For best results, you should use the manual pages that were installed on your system with your version of OpenLDAP software so that you're looking at documentation that matches the code. While the OpenLDAP web site also provides the manual pages for convenience, you can not assume that they corresond to the particular version you're running.

Acknowledgments

The OpenLDAP Project is comprised of a team of volunteers. This document would not be possible without their contribution of time and energy.

The OpenLDAP Project would also like to thank the University of Michigan LDAP Team for building the foundation of LDAP software and information to which OpenLDAP Software is built upon. This document is based upon University of Michigan document: The SLAPD and SLURPD Administrators Guide.

Amendments

Suggested enhancements and corrections to this document should be submitted using the OpenLDAP Issue Tracking System (http://www.openldap.org/its/).

About this document

This document was produced using the Simple Document Format (SDF) documentation system (http://search.cpan.org/src/IANC/sdf-2.001/doc/catalog.html) developed by Ian Clatworthy. Tools for SDF are available from CPAN (http://search.cpan.org/search?query=SDF&mode=dist).


1. Introduction to OpenLDAP Directory Services

This document describes how to build, configure, and operate OpenLDAP Software to provide directory services. This includes details on how to configure and run the Standalone LDAP Daemon, slapd(8). It is intended for new and experienced administrators alike. This section provides a basic introduction to directory services and, in particular, the directory services provided by slapd(8). This introduction is only intended to provide enough information so one might get started learning about LDAP, X.500, and directory services.

1.1. What is a directory service?

A directory is a specialized database specifically designed for searching and browsing, in additional to supporting basic lookup and update functions.


Note: A directory is defined by some as merely a database optimized for read access. This definition, at best, is overly simplistic.

Directories tend to contain descriptive, attribute-based information and support sophisticated filtering capabilities. Directories generally do not support complicated transaction or roll-back schemes found in database management systems designed for handling high-volume complex updates. Directory updates are typically simple all-or-nothing changes, if they are allowed at all. Directories are generally tuned to give quick response to high-volume lookup or search operations. They may have the ability to replicate information widely in order to increase availability and reliability, while reducing response time. When directory information is replicated, temporary inconsistencies between the replicas may be okay, as long as inconsistencies are resolved in a timely manner.

There are many different ways to provide a directory service. Different methods allow different kinds of information to be stored in the directory, place different requirements on how that information can be referenced, queried and updated, how it is protected from unauthorized access, etc. Some directory services are local, providing service to a restricted context (e.g., the finger service on a single machine). Other services are global, providing service to a much broader context (e.g., the entire Internet). Global services are usually distributed, meaning that the data they contain is spread across many machines, all of which cooperate to provide the directory service. Typically a global service defines a uniform namespace which gives the same view of the data no matter where you are in relation to the data itself.

A web directory, such as provided by the Open Directory Project <http://dmoz.org>, is a good example of a directory service. These services catalog web pages and are specifically designed to support browsing and searching.

While some consider the Internet Domain Name System (DNS) is an example of a globally distributed directory service, DNS is not browseable nor searchable. It is more properly described as a globally distributed lookup service.

1.2. What is LDAP?

LDAP stands for Lightweight Directory Access Protocol. As the name suggests, it is a lightweight protocol for accessing directory services, specifically X.500-based directory services. LDAP runs over TCP/IP or other connection oriented transfer services. LDAP is an IETF Standard Track protocol and is specified in "Lightweight Directory Access Protocol (LDAP) Technical Specification Road Map" RFC4510.

This section gives an overview of LDAP from a user's perspective.

What kind of information can be stored in the directory? The LDAP information model is based on entries. An entry is a collection of attributes that has a globally-unique Distinguished Name (DN). The DN is used to refer to the entry unambiguously. Each of the entry's attributes has a type and one or more values. The types are typically mnemonic strings, like "cn" for common name, or "mail" for email address. The syntax of values depend on the attribute type. For example, a cn attribute might contain the value Babs Jensen. A mail attribute might contain the value "babs@example.com". A jpegPhoto attribute would contain a photograph in the JPEG (binary) format.

How is the information arranged? In LDAP, directory entries are arranged in a hierarchical tree-like structure. Traditionally, this structure reflected the geographic and/or organizational boundaries. Entries representing countries appear at the top of the tree. Below them are entries representing states and national organizations. Below them might be entries representing organizational units, people, printers, documents, or just about anything else you can think of. Figure 1.1 shows an example LDAP directory tree using traditional naming.

Figure 1.1: LDAP directory tree (traditional naming)

The tree may also be arranged based upon Internet domain names. This naming approach is becoming increasing popular as it allows for directory services to be located using the DNS. Figure 1.2 shows an example LDAP directory tree using domain-based naming.

Figure 1.2: LDAP directory tree (Internet naming)

In addition, LDAP allows you to control which attributes are required and allowed in an entry through the use of a special attribute called objectClass. The values of the objectClass attribute determine the schema rules the entry must obey.

How is the information referenced? An entry is referenced by its distinguished name, which is constructed by taking the name of the entry itself (called the Relative Distinguished Name or RDN) and concatenating the names of its ancestor entries. For example, the entry for Barbara Jensen in the Internet naming example above has an RDN of uid=babs and a DN of uid=babs,ou=People,dc=example,dc=com. The full DN format is described in RFC4514, "LDAP: String Representation of Distinguished Names."

How is the information accessed? LDAP defines operations for interrogating and updating the directory. Operations are provided for adding and deleting an entry from the directory, changing an existing entry, and changing the name of an entry. Most of the time, though, LDAP is used to search for information in the directory. The LDAP search operation allows some portion of the directory to be searched for entries that match some criteria specified by a search filter. Information can be requested from each entry that matches the criteria.

For example, you might want to search the entire directory subtree at and below dc=example,dc=com for people with the name Barbara Jensen, retrieving the email address of each entry found. LDAP lets you do this easily. Or you might want to search the entries directly below the st=California,c=US entry for organizations with the string Acme in their name, and that have a fax number. LDAP lets you do this too. The next section describes in more detail what you can do with LDAP and how it might be useful to you.

How is the information protected from unauthorized access? Some directory services provide no protection, allowing anyone to see the information. LDAP provides a mechanism for a client to authenticate, or prove its identity to a directory server, paving the way for rich access control to protect the information the server contains. LDAP also supports data security (integrity and confidentiality) services.

1.3. When should I use LDAP?

This is a very good question. In general, you should use a Directory server when you require data to be centrally managed, stored and accessible via standards based methods.

Some common examples found throughout the industry are, but not limited to:

There are various Distributed Schema Files that are standards based, but you can always create your own Schema Specification.

There are always new ways to use a Directory and apply LDAP principles to address certain problems, therefore there is no simple answer to this question.

If in doubt, join the general LDAP forum for non-commercial discussions and information relating to LDAP at: http://www.umich.edu/~dirsvcs/ldap/mailinglist.html and ask

1.4. When should I not use LDAP?

When you start finding yourself bending the directory to do what you require, maybe a redesign is needed. Or if you only require one application to use and manipulate your data (for discussion of LDAP vs RDBMS, please read the LDAP vs RDBMS section).

It will become obvious when LDAP is the right tool for the job.

1.5. How does LDAP work?

LDAP utilizes a client-server model. One or more LDAP servers contain the data making up the directory information tree (DIT). The client connects to servers and asks it a question. The server responds with an answer and/or with a pointer to where the client can get additional information (typically, another LDAP server). No matter which LDAP server a client connects to, it sees the same view of the directory; a name presented to one LDAP server references the same entry it would at another LDAP server. This is an important feature of a global directory service.

1.6. What about X.500?

Technically, LDAP is a directory access protocol to an X.500 directory service, the OSI directory service. Initially, LDAP clients accessed gateways to the X.500 directory service. This gateway ran LDAP between the client and gateway and X.500's Directory Access Protocol (DAP) between the gateway and the X.500 server. DAP is a heavyweight protocol that operates over a full OSI protocol stack and requires a significant amount of computing resources. LDAP is designed to operate over TCP/IP and provides most of the functionality of DAP at a much lower cost.

While LDAP is still used to access X.500 directory service via gateways, LDAP is now more commonly directly implemented in X.500 servers.

The Standalone LDAP Daemon, or slapd(8), can be viewed as a lightweight X.500 directory server. That is, it does not implement the X.500's DAP nor does it support the complete X.500 models.

If you are already running a X.500 DAP service and you want to continue to do so, you can probably stop reading this guide. This guide is all about running LDAP via slapd(8), without running X.500 DAP. If you are not running X.500 DAP, want to stop running X.500 DAP, or have no immediate plans to run X.500 DAP, read on.

It is possible to replicate data from an LDAP directory server to a X.500 DAP DSA. This requires an LDAP/DAP gateway. OpenLDAP Software does not include such a gateway.

1.7. What is the difference between LDAPv2 and LDAPv3?

LDAPv3 was developed in the late 1990's to replace LDAPv2. LDAPv3 adds the following features to LDAP:

LDAPv2 is historic (RFC3494). As most so-called LDAPv2 implementations (including slapd(8)) do not conform to the LDAPv2 technical specification, interoperability amongst implementations claiming LDAPv2 support is limited. As LDAPv2 differs significantly from LDAPv3, deploying both LDAPv2 and LDAPv3 simultaneously is quite problematic. LDAPv2 should be avoided. LDAPv2 is disabled by default.

1.8. LDAP vs RDBMS

This question is raised many times, in different forms. The most common, however, is: Why doesn't OpenLDAP drop Berkeley DB and use a relational database management system (RDBMS) instead? In general, expecting that the sophisticated algorithms implemented by commercial-grade RDBMS would make OpenLDAP be faster or somehow better and, at the same time, permitting sharing of data with other applications.

The short answer is that use of an embedded database and custom indexing system allows OpenLDAP to provide greater performance and scalability without loss of reliability. OpenLDAP uses Berkeley DB concurrent / transactional database software. This is the same software used by leading commercial directory software.

Now for the long answer. We are all confronted all the time with the choice RDBMSes vs. directories. It is a hard choice and no simple answer exists.

It is tempting to think that having a RDBMS backend to the directory solves all problems. However, it is a pig. This is because the data models are very different. Representing directory data with a relational database is going to require splitting data into multiple tables.

Think for a moment about the person objectclass. Its definition requires attribute types objectclass, sn and cn and allows attribute types userPassword, telephoneNumber, seeAlso and description. All of these attributes are multivalued, so a normalization requires putting each attribute type in a separate table.

Now you have to decide on appropriate keys for those tables. The primary key might be a combination of the DN, but this becomes rather inefficient on most database implementations.

The big problem now is that accessing data from one entry requires seeking on different disk areas. On some applications this may be OK but in many applications performance suffers.

The only attribute types that can be put in the main table entry are those that are mandatory and single-value. You may add also the optional single-valued attributes and set them to NULL or something if not present.

But wait, the entry can have multiple objectclasses and they are organized in an inheritance hierarchy. An entry of objectclass organizationalPerson now has the attributes from person plus a few others and some formerly optional attribute types are now mandatory.

What to do? Should we have different tables for the different objectclasses? This way the person would have an entry on the person table, another on organizationalPerson, etc. Or should we get rid of person and put everything on the second table?

But what do we do with a filter like (cn=*) where cn is an attribute type that appears in many, many objectclasses. Should we search all possible tables for matching entries? Not very attractive.

Once this point is reached, three approaches come to mind. One is to do full normalization so that each attribute type, no matter what, has its own separate table. The simplistic approach where the DN is part of the primary key is extremely wasteful, and calls for an approach where the entry has a unique numeric id that is used instead for the keys and a main table that maps DNs to ids. The approach, anyway, is very inefficient when several attribute types from one or more entries are requested. Such a database, though cumbersomely, can be managed from SQL applications.

The second approach is to put the whole entry as a blob in a table shared by all entries regardless of the objectclass and have additional tables that act as indices for the first table. Index tables are not database indices, but are fully managed by the LDAP server-side implementation. However, the database becomes unusable from SQL. And, thus, a fully fledged database system provides little or no advantage. The full generality of the database is unneeded. Much better to use something light and fast, like Berkeley DB.

A completely different way to see this is to give up any hopes of implementing the directory data model. In this case, LDAP is used as an access protocol to data that provides only superficially the directory data model. For instance, it may be read only or, where updates are allowed, restrictions are applied, such as making single-value attribute types that would allow for multiple values. Or the impossibility to add new objectclasses to an existing entry or remove one of those present. The restrictions span the range from allowed restrictions (that might be elsewhere the result of access control) to outright violations of the data model. It can be, however, a method to provide LDAP access to preexisting data that is used by other applications. But in the understanding that we don't really have a "directory".

Existing commercial LDAP server implementations that use a relational database are either from the first kind or the third. I don't know of any implementation that uses a relational database to do inefficiently what BDB does efficiently. For those who are interested in "third way" (exposing EXISTING data from RDBMS as LDAP tree, having some limitations compared to classic LDAP model, but making it possible to interoperate between LDAP and SQL applications):

OpenLDAP includes back-sql - the backend that makes it possible. It uses ODBC + additional metainformation about translating LDAP queries to SQL queries in your RDBMS schema, providing different levels of access - from read-only to full access depending on RDBMS you use, and your schema.

For more information on concept and limitations, see slapd-sql(5) man page, or the Backends section. There are also several examples for several RDBMSes in back-sql/rdbms_depend/* subdirectories.

1.9. What is slapd and what can it do?

slapd(8) is an LDAP directory server that runs on many different platforms. You can use it to provide a directory service of your very own. Your directory can contain pretty much anything you want to put in it. You can connect it to the global LDAP directory service, or run a service all by yourself. Some of slapd's more interesting features and capabilities include:

LDAPv3: slapd implements version 3 of Lightweight Directory Access Protocol. slapd supports LDAP over both IPv4 and IPv6 and Unix IPC.

Simple Authentication and Security Layer: slapd supports strong authentication and data security (integrity and confidentiality) services through the use of SASL. slapd's SASL implementation utilizes Cyrus SASL software which supports a number of mechanisms including DIGEST-MD5, EXTERNAL, and GSSAPI.

Transport Layer Security: slapd supports certificate-based authentication and data security (integrity and confidentiality) services through the use of TLS (or SSL). slapd's TLS implementation can utilize OpenSSL, GnuTLS, or MozNSS software.

Topology control: slapd can be configured to restrict access at the socket layer based upon network topology information. This feature utilizes TCP wrappers.

Access control: slapd provides a rich and powerful access control facility, allowing you to control access to the information in your database(s). You can control access to entries based on LDAP authorization information, IP address, domain name and other criteria. slapd supports both static and dynamic access control information.

Internationalization: slapd supports Unicode and language tags.

Choice of database backends: slapd comes with a variety of different database backends you can choose from. They include BDB, a high-performance transactional database backend; HDB, a hierarchical high-performance transactional backend; SHELL, a backend interface to arbitrary shell scripts; and PASSWD, a simple backend interface to the passwd(5) file. The BDB and HDB backends utilize Oracle Berkeley DB.

Multiple database instances: slapd can be configured to serve multiple databases at the same time. This means that a single slapd server can respond to requests for many logically different portions of the LDAP tree, using the same or different database backends.

Generic modules API: If you require even more customization, slapd lets you write your own modules easily. slapd consists of two distinct parts: a front end that handles protocol communication with LDAP clients; and modules which handle specific tasks such as database operations. Because these two pieces communicate via a well-defined C API, you can write your own customized modules which extend slapd in numerous ways. Also, a number of programmable database modules are provided. These allow you to expose external data sources to slapd using popular programming languages (Perl, shell, and SQL).

Threads: slapd is threaded for high performance. A single multi-threaded slapd process handles all incoming requests using a pool of threads. This reduces the amount of system overhead required while providing high performance.

Replication: slapd can be configured to maintain shadow copies of directory information. This single-master/multiple-slave replication scheme is vital in high-volume environments where a single slapd installation just doesn't provide the necessary availability or reliability. For extremely demanding environments where a single point of failure is not acceptable, multi-master replication is also available. slapd includes support for LDAP Sync-based replication.

Proxy Cache: slapd can be configured as a caching LDAP proxy service.

Configuration: slapd is highly configurable through a single configuration file which allows you to change just about everything you'd ever want to change. Configuration options have reasonable defaults, making your job much easier. Configuration can also be performed dynamically using LDAP itself, which greatly improves manageability.


2. A Quick-Start Guide

The following is a quick start guide to OpenLDAP Software 2.4, including the Standalone LDAP Daemon, slapd(8).

It is meant to walk you through the basic steps needed to install and configure OpenLDAP Software. It should be used in conjunction with the other chapters of this document, manual pages, and other materials provided with the distribution (e.g. the INSTALL document) or on the OpenLDAP web site (http://www.OpenLDAP.org), in particular the OpenLDAP Software FAQ (http://www.OpenLDAP.org/faq/?file=2).

If you intend to run OpenLDAP Software seriously, you should review all of this document before attempting to install the software.


Note: This quick start guide does not use strong authentication nor any integrity or confidential protection services. These services are described in other chapters of the OpenLDAP Administrator's Guide.

  1. Get the software
    You can obtain a copy of the software by following the instructions on the OpenLDAP Software download page (http://www.openldap.org/software/download/). It is recommended that new users start with the latest release.
     
  2. Unpack the distribution
    Pick a directory for the source to live under, change directory to there, and unpack the distribution using the following commands:
      gunzip -c openldap-VERSION.tgz | tar xvfB -

    then relocate yourself into the distribution directory:
      cd openldap-VERSION

    You'll have to replace VERSION with the version name of the release.
     
  3. Review documentation
    You should now review the COPYRIGHT, LICENSE, README and INSTALL documents provided with the distribution. The COPYRIGHT and LICENSE provide information on acceptable use, copying, and limitation of warranty of OpenLDAP Software.
     
    You should also review other chapters of this document. In particular, the Building and Installing OpenLDAP Software chapter of this document provides detailed information on prerequisite software and installation procedures.
     
  4. Run configure
    You will need to run the provided configure script to configure the distribution for building on your system. The configure script accepts many command line options that enable or disable optional software features. Usually the defaults are okay, but you may want to change them. To get a complete list of options that configure accepts, use the --help option:
      ./configure --help

    However, given that you are using this guide, we'll assume you are brave enough to just let configure determine what's best:
      ./configure

    Assuming configure doesn't dislike your system, you can proceed with building the software. If configure did complain, well, you'll likely need to go to the Software FAQ Installation section (http://www.openldap.org/faq/?file=8) and/or actually read the Building and Installing OpenLDAP Software chapter of this document.
     
  5. Build the software.
    The next step is to build the software. This step has two parts, first we construct dependencies and then we compile the software:
      make depend
      make

    Both makes should complete without error.
     
  6. Test the build.
    To ensure a correct build, you should run the test suite (it only takes a few minutes):
      make test

    Tests which apply to your configuration will run and they should pass. Some tests, such as the replication test, may be skipped.
     
  7. Install the software.
    You are now ready to install the software; this usually requires super-user privileges:
      su root -c 'make install'

    Everything should now be installed under /usr/local (or whatever installation prefix was used by configure).
     
  8. Edit the configuration file.
    Use your favorite editor to edit the provided slapd.conf(5) example (usually installed as /usr/local/etc/openldap/slapd.conf) to contain a BDB database definition of the form:
      database bdb
      suffix "dc=<MY-DOMAIN>,dc=<COM>"
      rootdn "cn=Manager,dc=<MY-DOMAIN>,dc=<COM>"
      rootpw secret
      directory /usr/local/var/openldap-data

    Be sure to replace <MY-DOMAIN> and <COM> with the appropriate domain components of your domain name. For example, for example.com, use:
      database bdb
      suffix "dc=example,dc=com"
      rootdn "cn=Manager,dc=example,dc=com"
      rootpw secret
      directory /usr/local/var/openldap-data

    If your domain contains additional components, such as eng.uni.edu.eu, use:
      database bdb
      suffix "dc=eng,dc=uni,dc=edu,dc=eu"
      rootdn "cn=Manager,dc=eng,dc=uni,dc=edu,dc=eu"
      rootpw secret
      directory /usr/local/var/openldap-data

    Details regarding configuring slapd(8) can be found in the slapd.conf(5) manual page and the The slapd Configuration File chapter of this document. Note that the specified directory must exist prior to starting slapd(8).
     
  9. Start SLAPD.
    You are now ready to start the Standalone LDAP Daemon, slapd(8), by running the command:
      su root -c /usr/local/libexec/slapd

    To check to see if the server is running and configured correctly, you can run a search against it with ldapsearch(1). By default, ldapsearch is installed as /usr/local/bin/ldapsearch:
      ldapsearch -x -b '' -s base '(objectclass=*)' namingContexts

    Note the use of single quotes around command parameters to prevent special characters from being interpreted by the shell. This should return:
      dn:
      namingContexts: dc=example,dc=com

    Details regarding running slapd(8) can be found in the slapd(8) manual page and the Running slapd chapter of this document.
     
  10. Add initial entries to your directory.
    You can use ldapadd(1) to add entries to your LDAP directory. ldapadd expects input in LDIF form. We'll do it in two steps:
    1. create an LDIF file
    2. run ldapadd

    Use your favorite editor and create an LDIF file that contains:
      dn: dc=<MY-DOMAIN>,dc=<COM>
      objectclass: dcObject
      objectclass: organization
      o: <MY ORGANIZATION>
      dc: <MY-DOMAIN>

      dn: cn=Manager,dc=<MY-DOMAIN>,dc=<COM>
      objectclass: organizationalRole
      cn: Manager

    Be sure to replace <MY-DOMAIN> and <COM> with the appropriate domain components of your domain name. <MY ORGANIZATION> should be replaced with the name of your organization. When you cut and paste, be sure to trim any leading and trailing whitespace from the example.
      dn: dc=example,dc=com
      objectclass: dcObject
      objectclass: organization
      o: Example Company
      dc: example

      dn: cn=Manager,dc=example,dc=com
      objectclass: organizationalRole
      cn: Manager

    Now, you may run ldapadd(1) to insert these entries into your directory.
      ldapadd -x -D "cn=Manager,dc=<MY-DOMAIN>,dc=<COM>" -W -f example.ldif

    Be sure to replace <MY-DOMAIN> and <COM> with the appropriate domain components of your domain name. You will be prompted for the "secret" specified in slapd.conf. For example, for example.com, use:
      ldapadd -x -D "cn=Manager,dc=example,dc=com" -W -f example.ldif

    where example.ldif is the file you created above.

    Additional information regarding directory creation can be found in the Database Creation and Maintenance Tools chapter of this document.
     
  11. See if it works.
    Now we're ready to verify the added entries are in your directory. You can use any LDAP client to do this, but our example uses the ldapsearch(1) tool. Remember to replace dc=example,dc=com with the correct values for your site:
      ldapsearch -x -b 'dc=example,dc=com' '(objectclass=*)'

    This command will search for and retrieve every entry in the database.

You are now ready to add more entries using ldapadd(1) or another LDAP client, experiment with various configuration options, backend arrangements, etc..

Note that by default, the slapd(8) database grants read access to everybody excepting the super-user (as specified by the rootdn configuration directive). It is highly recommended that you establish controls to restrict access to authorized users. Access controls are discussed in the Access Control chapter. You are also encouraged to read the Security Considerations, Using SASL and Using TLS sections.

The following chapters provide more detailed information on making, installing, and running slapd(8).


3. The Big Picture - Configuration Choices

This section gives a brief overview of various LDAP directory configurations, and how your Standalone LDAP Daemon slapd(8) fits in with the rest of the world.

3.1. Local Directory Service

In this configuration, you run a slapd(8) instance which provides directory service for your local domain only. It does not interact with other directory servers in any way. This configuration is shown in Figure 3.1.

Figure 3.1: Local service configuration.

Use this configuration if you are just starting out (it's the one the quick-start guide makes for you) or if you want to provide a local service and are not interested in connecting to the rest of the world. It's easy to upgrade to another configuration later if you want.

3.2. Local Directory Service with Referrals

In this configuration, you run a slapd(8) instance which provides directory service for your local domain and configure it to return referrals to other servers capable of handling requests. You may run this service (or services) yourself or use one provided to you. This configuration is shown in Figure 3.2.

Figure 3.2: Local service with referrals

Use this configuration if you want to provide local service and participate in the Global Directory, or you want to delegate responsibility for subordinate entries to another server.

3.3. Replicated Directory Service

slapd(8) includes support for LDAP Sync-based replication, called syncrepl, which may be used to maintain shadow copies of directory information on multiple directory servers. In its most basic configuration, the master is a syncrepl provider and one or more slave (or shadow) are syncrepl consumers. An example master-slave configuration is shown in figure 3.3. Multi-Master configurations are also supported.

Figure 3.3: Replicated Directory Services

This configuration can be used in conjunction with either of the first two configurations in situations where a single slapd(8) instance does not provide the required reliability or availability.

3.4. Distributed Local Directory Service

In this configuration, the local service is partitioned into smaller services, each of which may be replicated, and glued together with superior and subordinate referrals.


4. Building and Installing OpenLDAP Software

This chapter details how to build and install the OpenLDAP Software package including slapd(8), the Standalone LDAP Daemon. Building and installing OpenLDAP Software requires several steps: installing prerequisite software, configuring OpenLDAP Software itself, making, and finally installing. The following sections describe this process in detail.

4.1. Obtaining and Extracting the Software

You can obtain OpenLDAP Software from the project's download page at http://www.openldap.org/software/download/ or directly from the project's FTP service at ftp://ftp.openldap.org/pub/OpenLDAP/.

The project makes available two series of packages for general use. The project makes releases as new features and bug fixes come available. Though the project takes steps to improve stability of these releases, it is common for problems to arise only after release. The stable release is the latest release which has demonstrated stability through general use.

Users of OpenLDAP Software can choose, depending on their desire for the latest features versus demonstrated stability, the most appropriate series to install.

After downloading OpenLDAP Software, you need to extract the distribution from the compressed archive file and change your working directory to the top directory of the distribution:

You'll have to replace VERSION with the version name of the release.

You should now review the COPYRIGHT, LICENSE, README and INSTALL documents provided with the distribution. The COPYRIGHT and LICENSE provide information on acceptable use, copying, and limitation of warranty of OpenLDAP Software. The README and INSTALL documents provide detailed information on prerequisite software and installation procedures.

4.2. Prerequisite software

OpenLDAP Software relies upon a number of software packages distributed by third parties. Depending on the features you intend to use, you may have to download and install a number of additional software packages. This section details commonly needed third party software packages you might have to install. However, for an up-to-date prerequisite information, the README document should be consulted. Note that some of these third party packages may depend on additional software packages. Install each package per the installation instructions provided with it.

4.2.1. Transport Layer Security

OpenLDAP clients and servers require installation of OpenSSL, GnuTLS, or MozNSS TLS libraries to provide Transport Layer Security services. Though some operating systems may provide these libraries as part of the base system or as an optional software component, OpenSSL, GnuTLS, and Mozilla NSS often require separate installation.

OpenSSL is available from http://www.openssl.org/. GnuTLS is available from http://www.gnu.org/software/gnutls/. Mozilla NSS is available from http://developer.mozilla.org/en/NSS.

OpenLDAP Software will not be fully LDAPv3 compliant unless OpenLDAP's configure detects a usable TLS library.

4.2.2. Simple Authentication and Security Layer

OpenLDAP clients and servers require installation of Cyrus SASL libraries to provide Simple Authentication and Security Layer services. Though some operating systems may provide this library as part of the base system or as an optional software component, Cyrus SASL often requires separate installation.

Cyrus SASL is available from http://asg.web.cmu.edu/sasl/sasl-library.html. Cyrus SASL will make use of OpenSSL and Kerberos/GSSAPI libraries if preinstalled.

OpenLDAP Software will not be fully LDAPv3 compliant unless OpenLDAP's configure detects a usable Cyrus SASL installation.

4.2.3. Kerberos Authentication Service

OpenLDAP clients and servers support Kerberos authentication services. In particular, OpenLDAP supports the Kerberos V GSS-API SASL authentication mechanism known as the GSSAPI mechanism. This feature requires, in addition to Cyrus SASL libraries, either Heimdal or MIT Kerberos V libraries.

Heimdal Kerberos is available from http://www.pdc.kth.se/heimdal/. MIT Kerberos is available from http://web.mit.edu/kerberos/www/.

Use of strong authentication services, such as those provided by Kerberos, is highly recommended.

4.2.4. Database Software

OpenLDAP's slapd(8) MDB primary database backend uses the LMDB software included with the OpenLDAP source. There is no need to download any additional software to have MDB support.

OpenLDAP's slapd(8) BDB and HDB deprecated database backends require Oracle Corporation Berkeley DB. If not available at configure time, you will not be able to build slapd(8) with these primary database backends.

Your operating system may provide a supported version of Berkeley DB in the base system or as an optional software component. If not, you'll have to obtain and install it yourself.

Berkeley DB is available from Oracle Corporation's Berkeley DB download page http://www.oracle.com/technology/software/products/berkeley-db/index.html.

There are several versions available. Generally, the most recent release (with published patches) is recommended. This package is required if you wish to use the deprecated BDB or HDB database backends.


Note: Berkeley DB version 6.0.20 and later uses a software license that is incompatible with LDAP technology and should not be used with OpenLDAP.


Note: Please see Recommended OpenLDAP Software Dependency Versions for more information.

4.2.5. Threads

OpenLDAP is designed to take advantage of threads. OpenLDAP supports POSIX pthreads, Mach CThreads, and a number of other varieties. configure will complain if it cannot find a suitable thread subsystem. If this occurs, please consult the Software|Installation|Platform Hints section of the OpenLDAP FAQ http://www.openldap.org/faq/.

4.2.6. TCP Wrappers

slapd(8) supports TCP Wrappers (IP level access control filters) if preinstalled. Use of TCP Wrappers or other IP-level access filters (such as those provided by an IP-level firewall) is recommended for servers containing non-public information.

4.3. Running configure

Now you should probably run the configure script with the --help option. This will give you a list of options that you can change when building OpenLDAP. Many of the features of OpenLDAP can be enabled or disabled using this method.

        ./configure --help

The configure script also looks for certain variables on the command line and in the environment. These include:

Table 4.1: Variables
Variable Description
CC Specify alternative C Compiler
CFLAGS Specify additional compiler flags
CPPFLAGS Specify C Preprocessor flags
LDFLAGS Specify linker flags
LIBS Specify additional libraries

Now run the configure script with any desired configuration options or variables.

        ./configure [options] [variable=value ...]

As an example, let's assume that we want to install OpenLDAP with BDB backend and TCP Wrappers support. By default, BDB is enabled and TCP Wrappers is not. So, we just need to specify --enable-wrappers to include TCP Wrappers support:

        ./configure --enable-wrappers

However, this will fail to locate dependent software not installed in system directories. For example, if TCP Wrappers headers and libraries are installed in /usr/local/include and /usr/local/lib respectively, the configure script should typically be called as follows:

        ./configure --enable-wrappers \
                CPPFLAGS="-I/usr/local/include" \
                LDFLAGS="-L/usr/local/lib -Wl,-rpath,/usr/local/lib"

The configure script will normally auto-detect appropriate settings. If you have problems at this stage, consult any platform specific hints and check your configure options, if any.

4.4. Building the Software

Once you have run the configure script the last line of output should be:

        Please "make depend" to build dependencies

If the last line of output does not match, configure has failed, and you will need to review its output to determine what went wrong. You should not proceed until configure completes successfully.

To build dependencies, run:

        make depend

Now build the software, this step will actually compile OpenLDAP.

        make

You should examine the output of this command carefully to make sure everything is built correctly. Note that this command builds the LDAP libraries and associated clients as well as slapd(8).

4.5. Testing the Software

Once the software has been properly configured and successfully made, you should run the test suite to verify the build.

        make test

Tests which apply to your configuration will run and they should pass. Some tests, such as the replication test, may be skipped if not supported by your configuration.

4.6. Installing the Software

Once you have successfully tested the software, you are ready to install it. You will need to have write permission to the installation directories you specified when you ran configure. By default OpenLDAP Software is installed in /usr/local. If you changed this setting with the --prefix configure option, it will be installed in the location you provided.

Typically, the installation requires super-user privileges. From the top level OpenLDAP source directory, type:

        su root -c 'make install'

and enter the appropriate password when requested.

You should examine the output of this command carefully to make sure everything is installed correctly. You will find the configuration files for slapd(8) in /usr/local/etc/openldap by default. See the chapter Configuring slapd for additional information.


5. Configuring slapd

Once the software has been built and installed, you are ready to configure slapd(8) for use at your site.

OpenLDAP 2.3 and later have transitioned to using a dynamic runtime configuration engine, slapd-config(5). slapd-config(5)

This chapter describes the general format of the slapd-config(5) configuration system, followed by a detailed description of commonly used settings.

The older style slapd.conf(5) file is still supported, but its use is deprecated and support for it will be withdrawn in a future OpenLDAP release. Configuring slapd(8) via slapd.conf(5) is described in the next chapter.

Refer to slapd(8) for information on how to have slapd automatically convert from slapd.conf(5) to slapd-config(5).


Note: Although the slapd-config(5) system stores its configuration as (text-based) LDIF files, you should never edit any of the LDIF files directly. Configuration changes should be performed via LDAP operations, e.g. ldapadd(1), ldapdelete(1), or ldapmodify(1).


Note: You will need to continue to use the older slapd.conf(5) configuration system if your OpenLDAP installation requires the use of one or more backends or overlays that have not been updated to use the slapd-config(5) system. As of OpenLDAP 2.4.33, all of the official backends have been updated. There may be additional contributed or experimental overlays that also have not been updated.

5.1. Configuration Layout

The slapd configuration is stored as a special LDAP directory with a predefined schema and DIT. There are specific objectClasses used to carry global configuration options, schema definitions, backend and database definitions, and assorted other items. A sample config tree is shown in Figure 5.1.

Figure 5.1: Sample configuration tree.

Other objects may be part of the configuration but were omitted from the illustration for clarity.

The slapd-config configuration tree has a very specific structure. The root of the tree is named cn=config and contains global configuration settings. Additional settings are contained in separate child entries:

The usual rules for LDIF files apply to the configuration information: Comment lines beginning with a '#' character are ignored. If a line begins with a single space, it is considered a continuation of the previous line (even if the previous line is a comment) and the single leading space is removed. Entries are separated by blank lines.

The general layout of the config LDIF is as follows:

        # global configuration settings
        dn: cn=config
        objectClass: olcGlobal
        cn: config
        <global config settings>

        # schema definitions
        dn: cn=schema,cn=config
        objectClass: olcSchemaConfig
        cn: schema
        <system schema>

        dn: cn={X}core,cn=schema,cn=config
        objectClass: olcSchemaConfig
        cn: {X}core
        <core schema>

        # additional user-specified schema
        ...

        # backend definitions
        dn: olcBackend=<typeA>,cn=config
        objectClass: olcBackendConfig
        olcBackend: <typeA>
        <backend-specific settings>

        # database definitions
        dn: olcDatabase={X}<typeA>,cn=config
        objectClass: olcDatabaseConfig
        olcDatabase: {X}<typeA>
        <database-specific settings>

        # subsequent definitions and settings
        ...

Some of the entries listed above have a numeric index "{X}" in their names. While most configuration settings have an inherent ordering dependency (i.e., one setting must take effect before a subsequent one may be set), LDAP databases are inherently unordered. The numeric index is used to enforce a consistent ordering in the configuration database, so that all ordering dependencies are preserved. In most cases the index does not have to be provided; it will be automatically generated based on the order in which entries are created.

Configuration directives are specified as values of individual attributes. Most of the attributes and objectClasses used in the slapd configuration have a prefix of "olc" (OpenLDAP Configuration) in their names. Generally there is a one-to-one correspondence between the attributes and the old-style slapd.conf configuration keywords, using the keyword as the attribute name, with the "olc" prefix attached.

A configuration directive may take arguments. If so, the arguments are separated by whitespace. If an argument contains whitespace, the argument should be enclosed in double quotes "like this". In the descriptions that follow, arguments that should be replaced by actual text are shown in brackets <>.

The distribution contains an example configuration file that will be installed in the /usr/local/etc/openldap directory. A number of files containing schema definitions (attribute types and object classes) are also provided in the /usr/local/etc/openldap/schema directory.

5.2. Configuration Directives

This section details commonly used configuration directives. For a complete list, see the slapd-config(5) manual page. This section will treat the configuration directives in a top-down order, starting with the global directives in the cn=config entry. Each directive will be described along with its default value (if any) and an example of its use.

5.2.1. cn=config

Directives contained in this entry generally apply to the server as a whole. Most of them are system or connection oriented, not database related. This entry must have the olcGlobal objectClass.

5.2.1.1. olcIdleTimeout: <integer>

Specify the number of seconds to wait before forcibly closing an idle client connection. A value of 0, the default, disables this feature.

5.2.1.2. olcLogLevel: <level>

This directive specifies the level at which debugging statements and operation statistics should be syslogged (currently logged to the syslogd(8) LOG_LOCAL4 facility). You must have configured OpenLDAP --enable-debug (the default) for this to work (except for the two statistics levels, which are always enabled). Log levels may be specified as integers or by keyword. Multiple log levels may be used and the levels are additive. To display what levels correspond to what kind of debugging, invoke slapd with -d? or consult the table below. The possible values for <level> are:

Table 5.1: Debugging Levels
Level Keyword Description
-1 any enable all debugging
0   no debugging
1 (0x1 trace) trace function calls
2 (0x2 packets) debug packet handling
4 (0x4 args) heavy trace debugging
8 (0x8 conns) connection management
16 (0x10 BER) print out packets sent and received
32 (0x20 filter) search filter processing
64 (0x40 config) configuration processing
128 (0x80 ACL) access control list processing
256 (0x100 stats) stats log connections/operations/results
512 (0x200 stats2) stats log entries sent
1024 (0x400 shell) print communication with shell backends
2048 (0x800 parse) print entry parsing debugging
16384 (0x4000 sync) syncrepl consumer processing
32768 (0x8000 none) only messages that get logged whatever log level is set

The desired log level can be input as a single integer that combines the (ORed) desired levels, both in decimal or in hexadecimal notation, as a list of integers (that are ORed internally), or as a list of the names that are shown between brackets, such that

                olcLogLevel 129
                olcLogLevel 0x81
                olcLogLevel 128 1
                olcLogLevel 0x80 0x1
                olcLogLevel acl trace

are equivalent.

Examples:

 olcLogLevel -1

This will cause lots and lots of debugging information to be logged.

 olcLogLevel conns filter

Just log the connection and search filter processing.

 olcLogLevel none

Log those messages that are logged regardless of the configured loglevel. This differs from setting the log level to 0, when no logging occurs. At least the None level is required to have high priority messages logged.

Default:

 olcLogLevel stats

Basic stats logging is configured by default. However, if no olcLogLevel is defined, no logging occurs (equivalent to a 0 level).

5.2.1.3. olcReferral <URI>

This directive specifies the referral to pass back when slapd cannot find a local database to handle a request.

Example:

        olcReferral: ldap://root.openldap.org

This will refer non-local queries to the global root LDAP server at the OpenLDAP Project. Smart LDAP clients can re-ask their query at that server, but note that most of these clients are only going to know how to handle simple LDAP URLs that contain a host part and optionally a distinguished name part.

5.2.1.4. Sample Entry

dn: cn=config
objectClass: olcGlobal
cn: config
olcIdleTimeout: 30
olcLogLevel: Stats
olcReferral: ldap://root.openldap.org

5.2.2. cn=module

If support for dynamically loaded modules was enabled when configuring slapd, cn=module entries may be used to specify sets of modules to load. Module entries must have the olcModuleList objectClass.

5.2.2.1. olcModuleLoad: <filename>

Specify the name of a dynamically loadable module to load. The filename may be an absolute path name or a simple filename. Non-absolute names are searched for in the directories specified by the olcModulePath directive.

5.2.2.2. olcModulePath: <pathspec>

Specify a list of directories to search for loadable modules. Typically the path is colon-separated but this depends on the operating system.

5.2.2.3. Sample Entries

dn: cn=module{0},cn=config
objectClass: olcModuleList
cn: module{0}
olcModuleLoad: /usr/local/lib/smbk5pwd.la

dn: cn=module{1},cn=config
objectClass: olcModuleList
cn: module{1}
olcModulePath: /usr/local/lib:/usr/local/lib/slapd
olcModuleLoad: accesslog.la
olcModuleLoad: pcache.la

5.2.3. cn=schema

The cn=schema entry holds all of the schema definitions that are hard-coded in slapd. As such, the values in this entry are generated by slapd so no schema values need to be provided in the config file. The entry must still be defined though, to serve as a base for the user-defined schema to add in underneath. Schema entries must have the olcSchemaConfig objectClass.

5.2.3.1. olcAttributeTypes: <RFC4512 Attribute Type Description>

This directive defines an attribute type. Please see the Schema Specification chapter for information regarding how to use this directive.

5.2.3.2. olcObjectClasses: <RFC4512 Object Class Description>

This directive defines an object class. Please see the Schema Specification chapter for information regarding how to use this directive.

5.2.3.3. Sample Entries

dn: cn=schema,cn=config
objectClass: olcSchemaConfig
cn: schema

dn: cn=test,cn=schema,cn=config
objectClass: olcSchemaConfig
cn: test
olcAttributeTypes: ( 1.1.1
  NAME 'testAttr'
  EQUALITY integerMatch
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.27 )
olcAttributeTypes: ( 1.1.2 NAME 'testTwo' EQUALITY caseIgnoreMatch
  SUBSTR caseIgnoreSubstringsMatch SYNTAX 1.3.6.1.4.1.1466.115.121.1.44 )
olcObjectClasses: ( 1.1.3 NAME 'testObject'
  MAY ( testAttr $ testTwo ) AUXILIARY )

5.2.4. Backend-specific Directives

Backend directives apply to all database instances of the same type and, depending on the directive, may be overridden by database directives. Backend entries must have the olcBackendConfig objectClass.

5.2.4.1. olcBackend: <type>

This directive names a backend-specific configuration entry. <type> should be one of the supported backend types listed in Table 5.2.

Table 5.2: Database Backends
Types Description
bdb Berkeley DB transactional backend
config Slapd configuration backend
dnssrv DNS SRV backend
hdb Hierarchical variant of bdb backend
ldap Lightweight Directory Access Protocol (Proxy) backend
ldif Lightweight Data Interchange Format backend
meta Meta Directory backend
monitor Monitor backend
passwd Provides read-only access to passwd(5)
perl Perl Programmable backend
shell Shell (extern program) backend
sql SQL Programmable backend

Example:

        olcBackend: bdb

There are no other directives defined for this entry. Specific backend types may define additional attributes for their particular use but so far none have ever been defined. As such, these directives usually do not appear in any actual configurations.

5.2.4.2. Sample Entry

 dn: olcBackend=bdb,cn=config
 objectClass: olcBackendConfig
 olcBackend: bdb

5.2.5. Database-specific Directives

Directives in this section are supported by every type of database. Database entries must have the olcDatabaseConfig objectClass.

5.2.5.1. olcDatabase: [{<index>}]<type>

This directive names a specific database instance. The numeric {<index>} may be provided to distinguish multiple databases of the same type. Usually the index can be omitted, and slapd will generate it automatically. <type> should be one of the supported backend types listed in Table 5.2 or the frontend type.

The frontend is a special database that is used to hold database-level options that should be applied to all the other databases. Subsequent database definitions may also override some frontend settings.

The config database is also special; both the config and the frontend databases are always created implicitly even if they are not explicitly configured, and they are created before any other databases.

Example:

        olcDatabase: bdb

This marks the beginning of a new BDB database instance.

5.2.5.2. olcAccess: to <what> [ by <who> [<accesslevel>] [<control>] ]+

This directive grants access (specified by <accesslevel>) to a set of entries and/or attributes (specified by <what>) by one or more requestors (specified by <who>). See the Access Control section of this guide for basic usage.


Note: If no olcAccess directives are specified, the default access control policy, to * by * read, allows all users (both authenticated and anonymous) read access.


Note: Access controls defined in the frontend are appended to all other databases' controls.

5.2.5.3. olcReadonly { TRUE | FALSE }

This directive puts the database into "read-only" mode. Any attempts to modify the database will return an "unwilling to perform" error.

Default:

        olcReadonly: FALSE

5.2.5.4. olcRootDN: <DN>

This directive specifies the DN that is not subject to access control or administrative limit restrictions for operations on this database. The DN need not refer to an entry in this database or even in the directory. The DN may refer to a SASL identity.

Entry-based Example:

        olcRootDN: "cn=Manager,dc=example,dc=com"

SASL-based Example:

        olcRootDN: "uid=root,cn=example.com,cn=digest-md5,cn=auth"

See the SASL Authentication section for information on SASL authentication identities.

5.2.5.5. olcRootPW: <password>

This directive can be used to specify a password for the DN for the rootdn (when the rootdn is set to a DN within the database).

Example:

        olcRootPW: secret

It is also permissible to provide a hash of the password in RFC2307 form. slappasswd(8) may be used to generate the password hash.

Example:

        olcRootPW: {SSHA}ZKKuqbEKJfKSXhUbHG3fG8MDn9j1v4QN

The hash was generated using the command slappasswd -s secret.

5.2.5.6. olcSizeLimit: <integer>

This directive specifies the maximum number of entries to return from a search operation.

Default:

        olcSizeLimit: 500

See the Limits section of this guide and slapd-config(5) for more details.

5.2.5.7. olcSuffix: <dn suffix>

This directive specifies the DN suffix of queries that will be passed to this backend database. Multiple suffix lines can be given, and usually at least one is required for each database definition. (Some backend types, such as frontend and monitor use a hard-coded suffix which may not be overridden in the configuration.)

Example:

        olcSuffix: "dc=example,dc=com"

Queries with a DN ending in "dc=example,dc=com" will be passed to this backend.


Note: When the backend to pass a query to is selected, slapd looks at the suffix value(s) in each database definition in the order in which they were configured. Thus, if one database suffix is a prefix of another, it must appear after it in the configuration.

5.2.5.8. olcSyncrepl

        olcSyncrepl: rid=<replica ID>
                provider=ldap[s]://<hostname>[:port]
                [type=refreshOnly|refreshAndPersist]
                [interval=dd:hh:mm:ss]
                [retry=[<retry interval> <# of retries>]+]
                searchbase=<base DN>
                [filter=<filter str>]
                [scope=sub|one|base]
                [attrs=<attr list>]
                [attrsonly]
                [sizelimit=<limit>]
                [timelimit=<limit>]
                [schemachecking=on|off]
                [bindmethod=simple|sasl]
                [binddn=<DN>]
                [saslmech=<mech>]
                [authcid=<identity>]
                [authzid=<identity>]
                [credentials=<passwd>]
                [realm=<realm>]
                [secprops=<properties>]
                [starttls=yes|critical]
                [tls_cert=<file>]
                [tls_key=<file>]
                [tls_cacert=<file>]
                [tls_cacertdir=<path>]
                [tls_reqcert=never|allow|try|demand]
                [tls_ciphersuite=<ciphers>]
                [tls_crlcheck=none|peer|all]
                [logbase=<base DN>]
                [logfilter=<filter str>]
                [syncdata=default|accesslog|changelog]

This directive specifies the current database as a replica of the master content by establishing the current slapd(8) as a replication consumer site running a syncrepl replication engine. The master database is located at the replication provider site specified by the provider parameter. The replica database is kept up-to-date with the master content using the LDAP Content Synchronization protocol. See RFC4533 for more information on the protocol.

The rid parameter is used for identification of the current syncrepl directive within the replication consumer server, where <replica ID> uniquely identifies the syncrepl specification described by the current syncrepl directive. <replica ID> is non-negative and is no more than three decimal digits in length.

The provider parameter specifies the replication provider site containing the master content as an LDAP URI. The provider parameter specifies a scheme, a host and optionally a port where the provider slapd instance can be found. Either a domain name or IP address may be used for <hostname>. Examples are ldap://provider.example.com:389 or ldaps://192.168.1.1:636. If <port> is not given, the standard LDAP port number (389 or 636) is used. Note that the syncrepl uses a consumer-initiated protocol, and hence its specification is located at the consumer site, whereas the replica specification is located at the provider site. syncrepl and replica directives define two independent replication mechanisms. They do not represent the replication peers of each other.

The content of the syncrepl replica is defined using a search specification as its result set. The consumer slapd will send search requests to the provider slapd according to the search specification. The search specification includes searchbase, scope, filter, attrs, attrsonly, sizelimit, and timelimit parameters as in the normal search specification. The searchbase parameter has no default value and must always be specified. The scope defaults to sub, the filter defaults to (objectclass=*), attrs defaults to "*,+" to replicate all user and operational attributes, and attrsonly is unset by default. Both sizelimit and timelimit default to "unlimited", and only positive integers or "unlimited" may be specified.

The LDAP Content Synchronization protocol has two operation types: refreshOnly and refreshAndPersist. The operation type is specified by the type parameter. In the refreshOnly operation, the next synchronization search operation is periodically rescheduled at an interval time after each synchronization operation finishes. The interval is specified by the interval parameter. It is set to one day by default. In the refreshAndPersist operation, a synchronization search remains persistent in the provider slapd instance. Further updates to the master replica will generate searchResultEntry to the consumer slapd as the search responses to the persistent synchronization search.

If an error occurs during replication, the consumer will attempt to reconnect according to the retry parameter which is a list of the <retry interval> and <# of retries> pairs. For example, retry="60 10 300 3" lets the consumer retry every 60 seconds for the first 10 times and then retry every 300 seconds for the next three times before stop retrying. + in <# of retries> means indefinite number of retries until success.

The schema checking can be enforced at the LDAP Sync consumer site by turning on the schemachecking parameter. If it is turned on, every replicated entry will be checked for its schema as the entry is stored into the replica content. Every entry in the replica should contain those attributes required by the schema definition. If it is turned off, entries will be stored without checking schema conformance. The default is off.

The binddn parameter gives the DN to bind as for the syncrepl searches to the provider slapd. It should be a DN which has read access to the replication content in the master database.

The bindmethod is simple or sasl, depending on whether simple password-based authentication or SASL authentication is to be used when connecting to the provider slapd instance.

Simple authentication should not be used unless adequate data integrity and confidentiality protections are in place (e.g. TLS or IPsec). Simple authentication requires specification of binddn and credentials parameters.

SASL authentication is generally recommended. SASL authentication requires specification of a mechanism using the saslmech parameter. Depending on the mechanism, an authentication identity and/or credentials can be specified using authcid and credentials, respectively. The authzid parameter may be used to specify an authorization identity.

The realm parameter specifies a realm which a certain mechanisms authenticate the identity within. The secprops parameter specifies Cyrus SASL security properties.

The starttls parameter specifies use of the StartTLS extended operation to establish a TLS session before authenticating to the provider. If the critical argument is supplied, the session will be aborted if the StartTLS request fails. Otherwise the syncrepl session continues without TLS. Note that the main slapd TLS settings are not used by the syncrepl engine; by default the TLS parameters from a ldap.conf(5) configuration file will be used. TLS settings may be specified here, in which case any ldap.conf(5) settings will be completely ignored.

Rather than replicating whole entries, the consumer can query logs of data modifications. This mode of operation is referred to as delta syncrepl. In addition to the above parameters, the logbase and logfilter parameters must be set appropriately for the log that will be used. The syncdata parameter must be set to either "accesslog" if the log conforms to the slapo-accesslog(5) log format, or "changelog" if the log conforms to the obsolete changelog format. If the syncdata parameter is omitted or set to "default" then the log parameters are ignored.

The syncrepl replication mechanism is supported by the bdb and hdb backends.

See the LDAP Sync Replication chapter of this guide for more information on how to use this directive.

5.2.5.9. olcTimeLimit: <integer>

This directive specifies the maximum number of seconds (in real time) slapd will spend answering a search request. If a request is not finished in this time, a result indicating an exceeded timelimit will be returned.

Default:

        olcTimeLimit: 3600

See the Limits section of this guide and slapd-config(5) for more details.

5.2.5.10. olcUpdateref: <URL>

This directive is only applicable in a slave slapd. It specifies the URL to return to clients which submit update requests upon the replica. If specified multiple times, each URL is provided.

Example:

        olcUpdateref:   ldap://master.example.net

5.2.5.11. Sample Entries

dn: olcDatabase=frontend,cn=config
objectClass: olcDatabaseConfig
objectClass: olcFrontendConfig
olcDatabase: frontend
olcReadOnly: FALSE

dn: olcDatabase=config,cn=config
objectClass: olcDatabaseConfig
olcDatabase: config
olcRootDN: cn=Manager,dc=example,dc=com

5.2.6. BDB and HDB Database Directives

Directives in this category apply to both the BDB and the HDB database. They are used in an olcDatabase entry in addition to the generic database directives defined above. For a complete reference of BDB/HDB configuration directives, see slapd-bdb(5). In addition to the olcDatabaseConfig objectClass, BDB and HDB database entries must have the olcBdbConfig and olcHdbConfig objectClass, respectively.

5.2.6.1. olcDbDirectory: <directory>

This directive specifies the directory where the BDB files containing the database and associated indices live.

Default:

        olcDbDirectory: /usr/local/var/openldap-data

5.2.6.2. olcDbCachesize: <integer>

This directive specifies the size in entries of the in-memory cache maintained by the BDB backend database instance.

Default:

        olcDbCachesize: 1000

5.2.6.3. olcDbCheckpoint: <kbyte> <min>

This directive specifies how often to checkpoint the BDB transaction log. A checkpoint operation flushes the database buffers to disk and writes a checkpoint record in the log. The checkpoint will occur if either <kbyte> data has been written or <min> minutes have passed since the last checkpoint. Both arguments default to zero, in which case they are ignored. When the <min> argument is non-zero, an internal task will run every <min> minutes to perform the checkpoint. See the Berkeley DB reference guide for more details.

Example:

        olcDbCheckpoint: 1024 10

5.2.6.4. olcDbConfig: <DB_CONFIG setting>

This attribute specifies a configuration directive to be placed in the DB_CONFIG file of the database directory. At server startup time, if no such file exists yet, the DB_CONFIG file will be created and the settings in this attribute will be written to it. If the file exists, its contents will be read and displayed in this attribute. The attribute is multi-valued, to accommodate multiple configuration directives. No default is provided, but it is essential to use proper settings here to get the best server performance.

Any changes made to this attribute will be written to the DB_CONFIG file and will cause the database environment to be reset so the changes can take immediate effect. If the environment cache is large and has not been recently checkpointed, this reset operation may take a long time. It may be advisable to manually perform a single checkpoint using the Berkeley DB db_checkpoint utility before using LDAP Modify to change this attribute.

Example:

        olcDbConfig: set_cachesize 0 10485760 0
        olcDbConfig: set_lg_bsize 2097512
        olcDbConfig: set_lg_dir /var/tmp/bdb-log
        olcDbConfig: set_flags DB_LOG_AUTOREMOVE

In this example, the BDB cache is set to 10MB, the BDB transaction log buffer size is set to 2MB, and the transaction log files are to be stored in the /var/tmp/bdb-log directory. Also a flag is set to tell BDB to delete transaction log files as soon as their contents have been checkpointed and they are no longer needed. Without this setting the transaction log files will continue to accumulate until some other cleanup procedure removes them. See the Berkeley DB documentation for the db_archive command for details. For a complete list of Berkeley DB flags please see - http://www.oracle.com/technology/documentation/berkeley-db/db/api_c/env_set_flags.html

Ideally the BDB cache must be at least as large as the working set of the database, the log buffer size should be large enough to accommodate most transactions without overflowing, and the log directory must be on a separate physical disk from the main database files. And both the database directory and the log directory should be separate from disks used for regular system activities such as the root, boot, or swap filesystems. See the FAQ-o-Matic and the Berkeley DB documentation for more details.

5.2.6.5. olcDbNosync: { TRUE | FALSE }

This option causes on-disk database contents to not be immediately synchronized with in memory changes upon change. Setting this option to TRUE may improve performance at the expense of data integrity. This directive has the same effect as using

        olcDbConfig: set_flags DB_TXN_NOSYNC

5.2.6.6. olcDbIDLcacheSize: <integer>

Specify the size of the in-memory index cache, in index slots. The default is zero. A larger value will speed up frequent searches of indexed entries. The optimal size will depend on the data and search characteristics of the database, but using a number three times the entry cache size is a good starting point.

Example:

        olcDbIDLcacheSize: 3000

5.2.6.7. olcDbIndex: {<attrlist> | default} [pres,eq,approx,sub,none]

This directive specifies the indices to maintain for the given attribute. If only an <attrlist> is given, the default indices are maintained. The index keywords correspond to the common types of matches that may be used in an LDAP search filter.

Example:

        olcDbIndex: default pres,eq
        olcDbIndex: uid
        olcDbIndex: cn,sn pres,eq,sub
        olcDbIndex: objectClass eq

The first line sets the default set of indices to maintain to present and equality. The second line causes the default (pres,eq) set of indices to be maintained for the uid attribute type. The third line causes present, equality, and substring indices to be maintained for cn and sn attribute types. The fourth line causes an equality index for the objectClass attribute type.

There is no index keyword for inequality matches. Generally these matches do not use an index. However, some attributes do support indexing for inequality matches, based on the equality index.

A substring index can be more explicitly specified as subinitial, subany, or subfinal, corresponding to the three possible components of a substring match filter. A subinitial index only indexes substrings that appear at the beginning of an attribute value. A subfinal index only indexes substrings that appear at the end of an attribute value, while subany indexes substrings that occur anywhere in a value.

Note that by default, setting an index for an attribute also affects every subtype of that attribute. E.g., setting an equality index on the name attribute causes cn, sn, and every other attribute that inherits from name to be indexed.

By default, no indices are maintained. It is generally advised that minimally an equality index upon objectClass be maintained.

        olcDbindex: objectClass eq

Additional indices should be configured corresponding to the most common searches that are used on the database. Presence indexing should not be configured for an attribute unless the attribute occurs very rarely in the database, and presence searches on the attribute occur very frequently during normal use of the directory. Most applications don't use presence searches, so usually presence indexing is not very useful.

If this setting is changed while slapd is running, an internal task will be run to generate the changed index data. All server operations can continue as normal while the indexer does its work. If slapd is stopped before the index task completes, indexing will have to be manually completed using the slapindex tool.

5.2.6.8. olcDbLinearIndex: { TRUE | FALSE }

If this setting is TRUE slapindex will index one attribute at a time. The default settings is FALSE in which case all indexed attributes of an entry are processed at the same time. When enabled, each indexed attribute is processed individually, using multiple passes through the entire database. This option improves slapindex performance when the database size exceeds the BDB cache size. When the BDB cache is large enough, this option is not needed and will decrease performance. Also by default, slapadd performs full indexing and so a separate slapindex run is not needed. With this option, slapadd does no indexing and slapindex must be used.

5.2.6.9. olcDbMode: { <octal> | <symbolic> }

This directive specifies the file protection mode that newly created database index files should have. This can be in the form 0600 or -rw-------

Default:

        olcDbMode: 0600

5.2.6.10. olcDbSearchStack: <integer>

Specify the depth of the stack used for search filter evaluation. Search filters are evaluated on a stack to accommodate nested AND / OR clauses. An individual stack is allocated for each server thread. The depth of the stack determines how complex a filter can be evaluated without requiring any additional memory allocation. Filters that are nested deeper than the search stack depth will cause a separate stack to be allocated for that particular search operation. These separate allocations can have a major negative impact on server performance, but specifying too much stack will also consume a great deal of memory. Each search uses 512K bytes per level on a 32-bit machine, or 1024K bytes per level on a 64-bit machine. The default stack depth is 16, thus 8MB or 16MB per thread is used on 32 and 64 bit machines, respectively. Also the 512KB size of a single stack slot is set by a compile-time constant which may be changed if needed; the code must be recompiled for the change to take effect.

Default:

        olcDbSearchStack: 16

5.2.6.11. olcDbShmKey: <integer>

Specify a key for a shared memory BDB environment. By default the BDB environment uses memory mapped files. If a non-zero value is specified, it will be used as the key to identify a shared memory region that will house the environment.

Example:

        olcDbShmKey: 42

5.2.6.12. Sample Entry

dn: olcDatabase=hdb,cn=config
objectClass: olcDatabaseConfig
objectClass: olcHdbConfig
olcDatabase: hdb
olcSuffix: "dc=example,dc=com"
olcDbDirectory: /usr/local/var/openldap-data
olcDbCacheSize: 1000
olcDbCheckpoint: 1024 10
olcDbConfig: set_cachesize 0 10485760 0
olcDbConfig: set_lg_bsize 2097152
olcDbConfig: set_lg_dir /var/tmp/bdb-log
olcDbConfig: set_flags DB_LOG_AUTOREMOVE
olcDbIDLcacheSize: 3000
olcDbIndex: objectClass eq

5.3. Configuration Example

The following is an example configuration, interspersed with explanatory text. It defines two databases to handle different parts of the X.500 tree; both are BDB database instances. The line numbers shown are provided for reference only and are not included in the actual file. First, the global configuration section:

  1.    # example config file - global configuration entry
  2.    dn: cn=config
  3.    objectClass: olcGlobal
  4.    cn: config
  5.    olcReferral: ldap://root.openldap.org
  6.

Line 1 is a comment. Lines 2-4 identify this as the global configuration entry. The olcReferral: directive on line 5 means that queries not local to one of the databases defined below will be referred to the LDAP server running on the standard port (389) at the host root.openldap.org. Line 6 is a blank line, indicating the end of this entry.

  7.    # internal schema
  8.    dn: cn=schema,cn=config
  9.    objectClass: olcSchemaConfig
 10.    cn: schema
 11.

Line 7 is a comment. Lines 8-10 identify this as the root of the schema subtree. The actual schema definitions in this entry are hardcoded into slapd so no additional attributes are specified here. Line 11 is a blank line, indicating the end of this entry.

 12.    # include the core schema
 13.    include: file:///usr/local/etc/openldap/schema/core.ldif
 14.

Line 12 is a comment. Line 13 is an LDIF include directive which accesses the core schema definitions in LDIF format. Line 14 is a blank line.

Next comes the database definitions. The first database is the special frontend database whose settings are applied globally to all the other databases.

 15.    # global database parameters
 16.    dn: olcDatabase=frontend,cn=config
 17.    objectClass: olcDatabaseConfig
 18.    olcDatabase: frontend
 19.    olcAccess: to * by * read
 20.

Line 15 is a comment. Lines 16-18 identify this entry as the global database entry. Line 19 is a global access control. It applies to all entries (after any applicable database-specific access controls). Line 20 is a blank line.

The next entry defines the config backend.

 21.    # set a rootpw for the config database so we can bind.
 22.    # deny access to everyone else.
 23.    dn: olcDatabase=config,cn=config
 24.    objectClass: olcDatabaseConfig
 25.    olcDatabase: config
 26.    olcRootPW: {SSHA}XKYnrjvGT3wZFQrDD5040US592LxsdLy
 27.    olcAccess: to * by * none
 28.

Lines 21-22 are comments. Lines 23-25 identify this entry as the config database entry. Line 26 defines the super-user password for this database. (The DN defaults to "cn=config".) Line 27 denies all access to this database, so only the super-user will be able to access it. (This is already the default access on the config database. It is just listed here for illustration, and to reiterate that unless a means to authenticate as the super-user is explicitly configured, the config database will be inaccessible.)

Line 28 is a blank line.

The next entry defines a BDB backend that will handle queries for things in the "dc=example,dc=com" portion of the tree. Indices are to be maintained for several attributes, and the userPassword attribute is to be protected from unauthorized access.

 29.    # BDB definition for example.com
 30.    dn: olcDatabase=bdb,cn=config
 31.    objectClass: olcDatabaseConfig
 32.    objectClass: olcBdbConfig
 33.    olcDatabase: bdb
 34.    olcSuffix: dc=example,dc=com
 35.    olcDbDirectory: /usr/local/var/openldap-data
 36.    olcRootDN: cn=Manager,dc=example,dc=com
 37.    olcRootPW: secret
 38.    olcDbIndex: uid pres,eq
 39.    olcDbIndex: cn,sn pres,eq,approx,sub
 40.    olcDbIndex: objectClass eq
 41.    olcAccess: to attrs=userPassword
 42.      by self write
 43.      by anonymous auth
 44.      by dn.base="cn=Admin,dc=example,dc=com" write
 45.      by * none
 46.    olcAccess: to *
 47.      by self write
 48.      by dn.base="cn=Admin,dc=example,dc=com" write
 49.      by * read
 50.

Line 29 is a comment. Lines 30-33 identify this entry as a BDB database configuration entry. Line 34 specifies the DN suffix for queries to pass to this database. Line 35 specifies the directory in which the database files will live.

Lines 36 and 37 identify the database super-user entry and associated password. This entry is not subject to access control or size or time limit restrictions.

Lines 38 through 40 indicate the indices to maintain for various attributes.

Lines 41 through 49 specify access control for entries in this database. For all applicable entries, the userPassword attribute is writable by the entry itself and by the "admin" entry. It may be used for authentication/authorization purposes, but is otherwise not readable. All other attributes are writable by the entry and the "admin" entry, but may be read by all users (authenticated or not).

Line 50 is a blank line, indicating the end of this entry.

The next entry defines another BDB database. This one handles queries involving the dc=example,dc=net subtree but is managed by the same entity as the first database. Note that without line 60, the read access would be allowed due to the global access rule at line 19.

 51.    # BDB definition for example.net
 52.    dn: olcDatabase=bdb,cn=config
 53.    objectClass: olcDatabaseConfig
 54.    objectClass: olcBdbConfig
 55.    olcDatabase: bdb
 56.    olcSuffix: "dc=example,dc=net"
 57.    olcDbDirectory: /usr/local/var/openldap-data-net
 58.    olcRootDN: "cn=Manager,dc=example,dc=com"
 59.    olcDbIndex: objectClass eq
 60.    olcAccess: to * by users read

5.4. Converting old style slapd.conf(5) file to cn=config format

Before converting to the cn=config format you should make sure that the config backend is properly configured in your existing config file. While the config backend is always present inside slapd, by default it is only accessible by its rootDN, and there are no default credentials assigned so unless you explicitly configure a means to authenticate to it, it will be unusable.

If you do not already have a database config section, add something like this to the end of slapd.conf

 database config
 rootpw VerySecret


Note: Since the config backend can be used to load arbitrary code into the slapd process, it is extremely important to carefully guard whatever credentials are used to access it. Since simple passwords are vulnerable to password guessing attacks, it is usually better to omit the rootpw and only use SASL authentication for the config rootDN.

An existing slapd.conf(5) file can be converted to the new format using slaptest(8) or any of the slap tools:

        slaptest -f /usr/local/etc/openldap/slapd.conf -F /usr/local/etc/openldap/slapd.d

Test that you can access entries under cn=config using the default rootdn and the rootpw configured above:

        ldapsearch -x -D cn=config -w VerySecret -b cn=config

You can then discard the old slapd.conf(5) file. Make sure to launch slapd(8) with the -F option to specify the configuration directory if you are not using the default directory path.


Note: When converting from the slapd.conf format to slapd.d format, any included files will also be integrated into the resulting configuration database.


6. The slapd Configuration File

This chapter describes configuring slapd(8) via the slapd.conf(5) configuration file. slapd.conf(5) has been deprecated and should only be used if your site requires one of the backends that hasn't yet been updated to work with the newer slapd-config(5) system. Configuring slapd(8) via slapd-config(5) is described in the previous chapter.

The slapd.conf(5) file is normally installed in the /usr/local/etc/openldap directory. An alternate configuration file location can be specified via a command-line option to slapd(8).

6.1. Configuration File Format

The slapd.conf(5) file consists of three types of configuration information: global, backend specific, and database specific. Global information is specified first, followed by information associated with a particular backend type, which is then followed by information associated with a particular database instance. Global directives can be overridden in backend and/or database directives, and backend directives can be overridden by database directives.

Blank lines and comment lines beginning with a '#' character are ignored. If a line begins with whitespace, it is considered a continuation of the previous line (even if the previous line is a comment).

The general format of slapd.conf is as follows:

        # global configuration directives
        <global config directives>

        # backend definition
        backend <typeA>
        <backend-specific directives>

        # first database definition & config directives
        database <typeA>
        <database-specific directives>

        # second database definition & config directives
        database <typeB>
        <database-specific directives>

        # second database definition & config directives
        database <typeA>
        <database-specific directives>

        # subsequent backend & database definitions & config directives
        ...

A configuration directive may take arguments. If so, they are separated by whitespace. If an argument contains whitespace, the argument should be enclosed in double quotes "like this". If an argument contains a double quote or a backslash character `\', the character should be preceded by a backslash character `\'.

The distribution contains an example configuration file that will be installed in the /usr/local/etc/openldap directory. A number of files containing schema definitions (attribute types and object classes) are also provided in the /usr/local/etc/openldap/schema directory.

6.2. Configuration File Directives

This section details commonly used configuration directives. For a complete list, see the slapd.conf(5) manual page. This section separates the configuration file directives into global, backend-specific and data-specific categories, describing each directive and its default value (if any), and giving an example of its use.

6.2.1. Global Directives

Directives described in this section apply to all backends and databases unless specifically overridden in a backend or database definition. Arguments that should be replaced by actual text are shown in brackets <>.

6.2.1.1. access to <what> [ by <who> [<accesslevel>] [<control>] ]+

This directive grants access (specified by <accesslevel>) to a set of entries and/or attributes (specified by <what>) by one or more requestors (specified by <who>). See the Access Control section of this guide for basic usage.


Note: If no access directives are specified, the default access control policy, access to * by * read, allows all both authenticated and anonymous users read access.

6.2.1.2. attributetype <RFC4512 Attribute Type Description>

This directive defines an attribute type. Please see the Schema Specification chapter for information regarding how to use this directive.

6.2.1.3. idletimeout <integer>

Specify the number of seconds to wait before forcibly closing an idle client connection. An idletimeout of 0, the default, disables this feature.

6.2.1.4. include <filename>

This directive specifies that slapd should read additional configuration information from the given file before continuing with the next line of the current file. The included file should follow the normal slapd config file format. The file is commonly used to include files containing schema specifications.


Note: You should be careful when using this directive - there is no small limit on the number of nested include directives, and no loop detection is done.

6.2.1.5. loglevel <level>

This directive specifies the level at which debugging statements and operation statistics should be syslogged (currently logged to the syslogd(8) LOG_LOCAL4 facility). You must have configured OpenLDAP --enable-debug (the default) for this to work (except for the two statistics levels, which are always enabled). Log levels may be specified as integers or by keyword. Multiple log levels may be used and the levels are additive. To display what numbers correspond to what kind of debugging, invoke slapd with -d? or consult the table below. The possible values for <integer> are:

Table 6.1: Debugging Levels
Level Keyword Description
-1 any enable all debugging
0   no debugging
1 (0x1 trace) trace function calls
2 (0x2 packets) debug packet handling
4 (0x4 args) heavy trace debugging
8 (0x8 conns) connection management
16 (0x10 BER) print out packets sent and received
32 (0x20 filter) search filter processing
64 (0x40 config) configuration processing
128 (0x80 ACL) access control list processing
256 (0x100 stats) stats log connections/operations/results
512 (0x200 stats2) stats log entries sent
1024 (0x400 shell) print communication with shell backends
2048 (0x800 parse) print entry parsing debugging
16384 (0x4000 sync) syncrepl consumer processing
32768 (0x8000 none) only messages that get logged whatever log level is set

The desired log level can be input as a single integer that combines the (ORed) desired levels, both in decimal or in hexadecimal notation, as a list of integers (that are ORed internally), or as a list of the names that are shown between brackets, such that

                loglevel 129
                loglevel 0x81
                loglevel 128 1
                loglevel 0x80 0x1
                loglevel acl trace

are equivalent.

Examples:

 loglevel -1

This will cause lots and lots of debugging information to be logged.

 loglevel conns filter

Just log the connection and search filter processing.

 loglevel none

Log those messages that are logged regardless of the configured loglevel. This differs from setting the log level to 0, when no logging occurs. At least the None level is required to have high priority messages logged.

Default:

 loglevel stats

Basic stats logging is configured by default. However, if no loglevel is defined, no logging occurs (equivalent to a 0 level).

6.2.1.6. objectclass <RFC4512 Object Class Description>

This directive defines an object class. Please see the Schema Specification chapter for information regarding how to use this directive.

6.2.1.7. referral <URI>

This directive specifies the referral to pass back when slapd cannot find a local database to handle a request.

Example:

        referral ldap://root.openldap.org

This will refer non-local queries to the global root LDAP server at the OpenLDAP Project. Smart LDAP clients can re-ask their query at that server, but note that most of these clients are only going to know how to handle simple LDAP URLs that contain a host part and optionally a distinguished name part.

6.2.1.8. sizelimit <integer>

This directive specifies the maximum number of entries to return from a search operation.

Default:

        sizelimit 500

See the Limits section of this guide and slapd.conf(5) for more details.

6.2.1.9. timelimit <integer>

This directive specifies the maximum number of seconds (in real time) slapd will spend answering a search request. If a request is not finished in this time, a result indicating an exceeded timelimit will be returned.

Default:

        timelimit 3600

See the Limits section of this guide and slapd.conf(5) for more details.

6.2.2. General Backend Directives

Directives in this section apply only to the backend in which they are defined. They are supported by every type of backend. Backend directives apply to all databases instances of the same type and, depending on the directive, may be overridden by database directives.

6.2.2.1. backend <type>

This directive marks the beginning of a backend declaration. <type> should be one of the supported backend types listed in Table 6.2.

Table 6.2: Database Backends
Types Description
bdb Berkeley DB transactional backend
dnssrv DNS SRV backend
hdb Hierarchical variant of bdb backend
ldap Lightweight Directory Access Protocol (Proxy) backend
meta Meta Directory backend
monitor Monitor backend
passwd Provides read-only access to passwd(5)
perl Perl Programmable backend
shell Shell (extern program) backend
sql SQL Programmable backend

Example:

        backend bdb

This marks the beginning of a new BDB backend definition.

6.2.3. General Database Directives

Directives in this section apply only to the database in which they are defined. They are supported by every type of database.

6.2.3.1. database <type>

This directive marks the beginning of a database instance declaration. <type> should be one of the supported backend types listed in Table 6.2.

Example:

        database bdb

This marks the beginning of a new BDB database instance declaration.

6.2.3.2. limits <who> <limit> [<limit> [...]]

Specify time and size limits based on who initiated an operation.

See the Limits section of this guide and slapd.conf(5) for more details.

6.2.3.3. readonly { on | off }

This directive puts the database into "read-only" mode. Any attempts to modify the database will return an "unwilling to perform" error.

Default:

        readonly off

6.2.3.4. rootdn <DN>

This directive specifies the DN that is not subject to access control or administrative limit restrictions for operations on this database. The DN need not refer to an entry in this database or even in the directory. The DN may refer to a SASL identity.

Entry-based Example:

        rootdn "cn=Manager,dc=example,dc=com"

SASL-based Example:

        rootdn "uid=root,cn=example.com,cn=digest-md5,cn=auth"

See the SASL Authentication section for information on SASL authentication identities.

6.2.3.5. rootpw <password>

This directive can be used to specifies a password for the DN for the rootdn (when the rootdn is set to a DN within the database).

Example:

        rootpw secret

It is also permissible to provide hash of the password in RFC2307 form. slappasswd(8) may be used to generate the password hash.

Example:

        rootpw {SSHA}ZKKuqbEKJfKSXhUbHG3fG8MDn9j1v4QN

The hash was generated using the command slappasswd -s secret.

6.2.3.6. suffix <dn suffix>

This directive specifies the DN suffix of queries that will be passed to this backend database. Multiple suffix lines can be given, and at least one is required for each database definition.

Example:

        suffix "dc=example,dc=com"

Queries with a DN ending in "dc=example,dc=com" will be passed to this backend.


Note: When the backend to pass a query to is selected, slapd looks at the suffix line(s) in each database definition in the order they appear in the file. Thus, if one database suffix is a prefix of another, it must appear after it in the config file.

6.2.3.7. syncrepl

        syncrepl rid=<replica ID>
                provider=ldap[s]://<hostname>[:port]
                [type=refreshOnly|refreshAndPersist]
                [interval=dd:hh:mm:ss]
                [retry=[<retry interval> <# of retries>]+]
                searchbase=<base DN>
                [filter=<filter str>]
                [scope=sub|one|base]
                [attrs=<attr list>]
                [attrsonly]
                [sizelimit=<limit>]
                [timelimit=<limit>]
                [schemachecking=on|off]
                [bindmethod=simple|sasl]
                [binddn=<DN>]
                [saslmech=<mech>]
                [authcid=<identity>]
                [authzid=<identity>]
                [credentials=<passwd>]
                [realm=<realm>]
                [secprops=<properties>]
                [starttls=yes|critical]
                [tls_cert=<file>]
                [tls_key=<file>]
                [tls_cacert=<file>]
                [tls_cacertdir=<path>]
                [tls_reqcert=never|allow|try|demand]
                [tls_ciphersuite=<ciphers>]
                [tls_crlcheck=none|peer|all]
                [logbase=<base DN>]
                [logfilter=<filter str>]
                [syncdata=default|accesslog|changelog]

This directive specifies the current database as a replica of the master content by establishing the current slapd(8) as a replication consumer site running a syncrepl replication engine. The master database is located at the replication provider site specified by the provider parameter. The replica database is kept up-to-date with the master content using the LDAP Content Synchronization protocol. See RFC4533 for more information on the protocol.

The rid parameter is used for identification of the current syncrepl directive within the replication consumer server, where <replica ID> uniquely identifies the syncrepl specification described by the current syncrepl directive. <replica ID> is non-negative and is no more than three decimal digits in length.

The provider parameter specifies the replication provider site containing the master content as an LDAP URI. The provider parameter specifies a scheme, a host and optionally a port where the provider slapd instance can be found. Either a domain name or IP address may be used for <hostname>. Examples are ldap://provider.example.com:389 or ldaps://192.168.1.1:636. If <port> is not given, the standard LDAP port number (389 or 636) is used. Note that the syncrepl uses a consumer-initiated protocol, and hence its specification is located at the consumer site, whereas the replica specification is located at the provider site. syncrepl and replica directives define two independent replication mechanisms. They do not represent the replication peers of each other.

The content of the syncrepl replica is defined using a search specification as its result set. The consumer slapd will send search requests to the provider slapd according to the search specification. The search specification includes searchbase, scope, filter, attrs, attrsonly, sizelimit, and timelimit parameters as in the normal search specification. The searchbase parameter has no default value and must always be specified. The scope defaults to sub, the filter defaults to (objectclass=*), attrs defaults to "*,+" to replicate all user and operational attributes, and attrsonly is unset by default. Both sizelimit and timelimit default to "unlimited", and only positive integers or "unlimited" may be specified.

The LDAP Content Synchronization protocol has two operation types: refreshOnly and refreshAndPersist. The operation type is specified by the type parameter. In the refreshOnly operation, the next synchronization search operation is periodically rescheduled at an interval time after each synchronization operation finishes. The interval is specified by the interval parameter. It is set to one day by default. In the refreshAndPersist operation, a synchronization search remains persistent in the provider slapd instance. Further updates to the master replica will generate searchResultEntry to the consumer slapd as the search responses to the persistent synchronization search.

If an error occurs during replication, the consumer will attempt to reconnect according to the retry parameter which is a list of the <retry interval> and <# of retries> pairs. For example, retry="60 10 300 3" lets the consumer retry every 60 seconds for the first 10 times and then retry every 300 seconds for the next three times before stop retrying. + in <# of retries> means indefinite number of retries until success.

The schema checking can be enforced at the LDAP Sync consumer site by turning on the schemachecking parameter. If it is turned on, every replicated entry will be checked for its schema as the entry is stored into the replica content. Every entry in the replica should contain those attributes required by the schema definition. If it is turned off, entries will be stored without checking schema conformance. The default is off.

The binddn parameter gives the DN to bind as for the syncrepl searches to the provider slapd. It should be a DN which has read access to the replication content in the master database.

The bindmethod is simple or sasl, depending on whether simple password-based authentication or SASL authentication is to be used when connecting to the provider slapd instance.

Simple authentication should not be used unless adequate data integrity and confidentiality protections are in place (e.g. TLS or IPsec). Simple authentication requires specification of binddn and credentials parameters.

SASL authentication is generally recommended. SASL authentication requires specification of a mechanism using the saslmech parameter. Depending on the mechanism, an authentication identity and/or credentials can be specified using authcid and credentials, respectively. The authzid parameter may be used to specify an authorization identity.

The realm parameter specifies a realm which a certain mechanisms authenticate the identity within. The secprops parameter specifies Cyrus SASL security properties.

The starttls parameter specifies use of the StartTLS extended operation to establish a TLS session before authenticating to the provider. If the critical argument is supplied, the session will be aborted if the StartTLS request fails. Otherwise the syncrepl session continues without TLS. Note that the main slapd TLS settings are not used by the syncrepl engine; by default the TLS parameters from a ldap.conf(5) configuration file will be used. TLS settings may be specified here, in which case any ldap.conf(5) settings will be completely ignored.

Rather than replicating whole entries, the consumer can query logs of data modifications. This mode of operation is referred to as delta syncrepl. In addition to the above parameters, the logbase and logfilter parameters must be set appropriately for the log that will be used. The syncdata parameter must be set to either "accesslog" if the log conforms to the slapo-accesslog(5) log format, or "changelog" if the log conforms to the obsolete changelog format. If the syncdata parameter is omitted or set to "default" then the log parameters are ignored.

The syncrepl replication mechanism is supported by the bdb and hdb backends.

See the LDAP Sync Replication chapter of this guide for more information on how to use this directive.

6.2.3.8. updateref <URL>

This directive is only applicable in a slave (or shadow) slapd(8) instance. It specifies the URL to return to clients which submit update requests upon the replica. If specified multiple times, each URL is provided.

Example:

        updateref       ldap://master.example.net

6.2.4. BDB and HDB Database Directives

Directives in this category only apply to both the BDB and the HDB database. That is, they must follow a "database bdb" or "database hdb" line and come before any subsequent "backend" or "database" line. For a complete reference of BDB/HDB configuration directives, see slapd-bdb(5).

6.2.4.1. directory <directory>

This directive specifies the directory where the BDB files containing the database and associated indices live.

Default:

        directory /usr/local/var/openldap-data

6.3. Configuration File Example

The following is an example configuration file, interspersed with explanatory text. It defines two databases to handle different parts of the X.500 tree; both are BDB database instances. The line numbers shown are provided for reference only and are not included in the actual file. First, the global configuration section:

  1.    # example config file - global configuration section
  2.    include /usr/local/etc/schema/core.schema
  3.    referral ldap://root.openldap.org
  4.    access to * by * read

Line 1 is a comment. Line 2 includes another config file which contains core schema definitions. The referral directive on line 3 means that queries not local to one of the databases defined below will be referred to the LDAP server running on the standard port (389) at the host root.openldap.org.

Line 4 is a global access control. It applies to all entries (after any applicable database-specific access controls).

The next section of the configuration file defines a BDB backend that will handle queries for things in the "dc=example,dc=com" portion of the tree. The database is to be replicated to two slave slapds, one on truelies, the other on judgmentday. Indices are to be maintained for several attributes, and the userPassword attribute is to be protected from unauthorized access.

  5.    # BDB definition for the example.com
  6.    database bdb
  7.    suffix "dc=example,dc=com"
  8.    directory /usr/local/var/openldap-data
  9.    rootdn "cn=Manager,dc=example,dc=com"
 10.    rootpw secret
 11.    # indexed attribute definitions
 12.    index uid pres,eq
 13.    index cn,sn pres,eq,approx,sub
 14.    index objectClass eq
 15.    # database access control definitions
 16.    access to attrs=userPassword
 17.        by self write
 18.        by anonymous auth
 19.        by dn.base="cn=Admin,dc=example,dc=com" write
 20.        by * none
 21.    access to *
 22.        by self write
 23.        by dn.base="cn=Admin,dc=example,dc=com" write
 24.        by * read

Line 5 is a comment. The start of the database definition is marked by the database keyword on line 6. Line 7 specifies the DN suffix for queries to pass to this database. Line 8 specifies the directory in which the database files will live.

Lines 9 and 10 identify the database super-user entry and associated password. This entry is not subject to access control or size or time limit restrictions.

Lines 12 through 14 indicate the indices to maintain for various attributes.

Lines 16 through 24 specify access control for entries in this database. For all applicable entries, the userPassword attribute is writable by the entry itself and by the "admin" entry. It may be used for authentication/authorization purposes, but is otherwise not readable. All other attributes are writable by the entry and the "admin" entry, but may be read by all users (authenticated or not).

The next section of the example configuration file defines another BDB database. This one handles queries involving the dc=example,dc=net subtree but is managed by the same entity as the first database. Note that without line 39, the read access would be allowed due to the global access rule at line 4.

 33.    # BDB definition for example.net
 34.    database bdb
 35.    suffix "dc=example,dc=net"
 36.    directory /usr/local/var/openldap-data-net
 37.    rootdn "cn=Manager,dc=example,dc=com"
 38.    index objectClass eq
 39.    access to * by users read


7. Running slapd

slapd(8) is designed to be run as a standalone service. This allows the server to take advantage of caching, manage concurrency issues with underlying databases, and conserve system resources. Running from inetd(8) is NOT an option.

7.1. Command-Line Options

slapd(8) supports a number of command-line options as detailed in the manual page. This section details a few commonly used options.

        -f <filename>

This option specifies an alternate configuration file for slapd. The default is normally /usr/local/etc/openldap/slapd.conf.

        -F <slapd-config-directory>

Specifies the slapd configuration directory. The default is /usr/local/etc/openldap/slapd.d.

If both -f and -F are specified, the config file will be read and converted to config directory format and written to the specified directory. If neither option is specified, slapd will attempt to read the default config directory before trying to use the default config file. If a valid config directory exists then the default config file is ignored. All of the slap tools that use the config options observe this same behavior.

        -h <URLs>

This option specifies alternative listener configurations. The default is ldap:/// which implies LDAP over TCP on all interfaces on the default LDAP port 389. You can specify specific host-port pairs or other protocol schemes (such as ldaps:// or ldapi://).

URL Protocol Transport
ldap:/// LDAP TCP port 389
ldaps:/// LDAP over SSL TCP port 636
ldapi:/// LDAP IPC (Unix-domain socket)

For example, -h "ldaps:// ldap://127.0.0.1:666" will create two listeners: one for the (non-standard) ldaps:// scheme on all interfaces on the default ldaps:// port 636, and one for the standard ldap:// scheme on the localhost (loopback) interface on port 666. Hosts may be specified using using hostnames or IPv4 or IPv6 addresses. Port values must be numeric.

For LDAP over IPC, the pathname of the Unix-domain socket can be encoded in the URL. Note that directory separators must be URL-encoded, like any other characters that are special to URLs. Thus the socket /usr/local/var/ldapi must be encoded as

        ldapi://%2Fusr%2Flocal%2Fvar%2Fldapi

ldapi: is described in detail in Using LDAP Over IPC Mechanisms [Chu-LDAPI]

Note that the ldapi:/// transport is not widely implemented: non-OpenLDAP clients may not be able to use it.

        -n <service-name>

This option specifies the service name used for logging and other purposes. The default service name is slapd.

        -l <syslog-local-user>

This option specifies the local user for the syslog(8) facility. Values can be LOCAL0, LOCAL1, LOCAL2, ..., and LOCAL7. The default is LOCAL4. This option may not be supported on all systems.

        -u user -g group

These options specify the user and group, respectively, to run as. user can be either a user name or uid. group can be either a group name or gid.

        -r directory

This option specifies a run-time directory. slapd will chroot(2) to this directory after opening listeners but before reading any configuration files or initializing any backends.

        -d <level> | ?

This option sets the slapd debug level to <level>. When level is a `?' character, the various debugging levels are printed and slapd exits, regardless of any other options you give it. Current debugging levels are

Table 7.1: Debugging Levels
Level Keyword Description
-1 any enable all debugging
0   no debugging
1 (0x1 trace) trace function calls
2 (0x2 packets) debug packet handling
4 (0x4 args) heavy trace debugging
8 (0x8 conns) connection management
16 (0x10 BER) print out packets sent and received
32 (0x20 filter) search filter processing
64 (0x40 config) configuration processing
128 (0x80 ACL) access control list processing
256 (0x100 stats) stats log connections/operations/results
512 (0x200 stats2) stats log entries sent
1024 (0x400 shell) print communication with shell backends
2048 (0x800 parse) print entry parsing debugging
16384 (0x4000 sync) syncrepl consumer processing
32768 (0x8000 none) only messages that get logged whatever log level is set

You may enable multiple levels by specifying the debug option once for each desired level. Or, since debugging levels are additive, you can do the math yourself. That is, if you want to trace function calls and watch the config file being processed, you could set level to the sum of those two levels (in this case, -d 65). Or, you can let slapd do the math, (e.g. -d 1 -d 64). Consult <ldap_log.h> for more details.


Note: slapd must have been compiled with --enable-debug defined for any debugging information beyond the two stats levels to be available (the default).

7.2. Starting slapd

In general, slapd is run like this:

        /usr/local/libexec/slapd [<option>]*

where /usr/local/libexec is determined by configure and <option> is one of the options described above (or in slapd(8)). Unless you have specified a debugging level (including level 0), slapd will automatically fork and detach itself from its controlling terminal and run in the background.

7.3. Stopping slapd

To kill off slapd(8) safely, you should give a command like this

        kill -INT `cat /usr/local/var/slapd.pid`

where /usr/local/var is determined by configure.

Killing slapd by a more drastic method may cause information loss or database corruption.


8. Access Control

8.1. Introduction

As the directory gets populated with more and more data of varying sensitivity, controlling the kinds of access granted to the directory becomes more and more critical. For instance, the directory may contain data of a confidential nature that you may need to protect by contract or by law. Or, if using the directory to control access to other services, inappropriate access to the directory may create avenues of attack to your sites security that result in devastating damage to your assets.

Access to your directory can be configured via two methods, the first using The slapd Configuration File and the second using the slapd-config(5) format (Configuring slapd).

The default access control policy is allow read by all clients. Regardless of what access control policy is defined, the rootdn is always allowed full rights (i.e. auth, search, compare, read and write) on everything and anything.

As a consequence, it's useless (and results in a performance penalty) to explicitly list the rootdn among the <by> clauses.

The following sections will describe Access Control Lists in greater depth and follow with some examples and recommendations. See slapd.access(5) for complete details.

8.2. Access Control via Static Configuration

Access to entries and attributes is controlled by the access configuration file directive. The general form of an access line is:

    <access directive> ::= access to <what>
        [by <who> [<access>] [<control>] ]+
    <what> ::= * |
        [dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>]
        [filter=<ldapfilter>] [attrs=<attrlist>]
    <basic-style> ::= regex | exact
    <scope-style> ::= base | one | subtree | children
    <attrlist> ::= <attr> [val[.<basic-style>]=<regex>] | <attr> , <attrlist>
    <attr> ::= <attrname> | entry | children
    <who> ::= * | [anonymous | users | self
            | dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>]
        [dnattr=<attrname>]
        [group[/<objectclass>[/<attrname>][.<basic-style>]]=<regex>]
        [peername[.<basic-style>]=<regex>]
        [sockname[.<basic-style>]=<regex>]
        [domain[.<basic-style>]=<regex>]
        [sockurl[.<basic-style>]=<regex>]
        [set=<setspec>]
        [aci=<attrname>]
    <access> ::= [self]{<level>|<priv>}
    <level> ::= none | disclose | auth | compare | search | read | write | manage
    <priv> ::= {=|+|-}{m|w|r|s|c|x|d|0}+
    <control> ::= [stop | continue | break]

where the <what> part selects the entries and/or attributes to which the access applies, the <who> part specifies which entities are granted access, and the <access> part specifies the access granted. Multiple <who> <access> <control> triplets are supported, allowing many entities to be granted different access to the same set of entries and attributes. Not all of these access control options are described here; for more details see the slapd.access(5) man page.

8.2.1. What to control access to

The <what> part of an access specification determines the entries and attributes to which the access control applies. Entries are commonly selected in two ways: by DN and by filter. The following qualifiers select entries by DN:

    to *
    to dn[.<basic-style>]=<regex>
    to dn.<scope-style>=<DN>

The first form is used to select all entries. The second form may be used to select entries by matching a regular expression against the target entry's normalized DN. (The second form is not discussed further in this document.) The third form is used to select entries which are within the requested scope of DN. The <DN> is a string representation of the Distinguished Name, as described in RFC4514.

The scope can be either base, one, subtree, or children. Where base matches only the entry with provided DN, one matches the entries whose parent is the provided DN, subtree matches all entries in the subtree whose root is the provided DN, and children matches all entries under the DN (but not the entry named by the DN).

For example, if the directory contained entries named:

    0: o=suffix
    1: cn=Manager,o=suffix
    2: ou=people,o=suffix
    3: uid=kdz,ou=people,o=suffix
    4: cn=addresses,uid=kdz,ou=people,o=suffix
    5: uid=hyc,ou=people,o=suffix

Then:

Entries may also be selected using a filter:

    to filter=<ldap filter>

where <ldap filter> is a string representation of an LDAP search filter, as described in RFC4515. For example:

    to filter=(objectClass=person)

Note that entries may be selected by both DN and filter by including both qualifiers in the <what> clause.

    to dn.one="ou=people,o=suffix" filter=(objectClass=person)

Attributes within an entry are selected by including a comma-separated list of attribute names in the <what> selector:

    attrs=<attribute list>

A specific value of an attribute is selected by using a single attribute name and also using a value selector:

    attrs=<attribute> val[.<style>]=<regex>

There are two special pseudo attributes entry and children. To read (and hence return) a target entry, the subject must have read access to the target's entry attribute. To perform a search, the subject must have search access to the search base's entry attribute. To add or delete an entry, the subject must have write access to the entry's entry attribute AND must have write access to the entry's parent's children attribute. To rename an entry, the subject must have write access to entry's entry attribute AND have write access to both the old parent's and new parent's children attributes. The complete examples at the end of this section should help clear things up.

Lastly, there is a special entry selector "*" that is used to select any entry. It is used when no other <what> selector has been provided. It's equivalent to "dn=.*"

8.2.2. Who to grant access to

The <who> part identifies the entity or entities being granted access. Note that access is granted to "entities" not "entries." The following table summarizes entity specifiers:

Table 6.3: Access Entity Specifiers
Specifier Entities
* All, including anonymous and authenticated users
anonymous Anonymous (non-authenticated) users
users Authenticated users
self User associated with target entry
dn[.<basic-style>]=<regex> Users matching a regular expression
dn.<scope-style>=<DN> Users within scope of a DN

The DN specifier behaves much like <what> clause DN specifiers.

Other control factors are also supported. For example, a <who> can be restricted by an entry listed in a DN-valued attribute in the entry to which the access applies:

    dnattr=<dn-valued attribute name>

The dnattr specification is used to give access to an entry whose DN is listed in an attribute of the entry (e.g., give access to a group entry to whoever is listed as the owner of the group entry).

Some factors may not be appropriate in all environments (or any). For example, the domain factor relies on IP to domain name lookups. As these can easily be spoofed, the domain factor should be avoided.

8.2.3. The access to grant

The kind of <access> granted can be one of the following:

Table 6.4: Access Levels
Level Privileges Description
none = 0 no access
disclose = d needed for information disclosure on error
auth = dx needed to authenticate (bind)
compare = cdx needed to compare
search = scdx needed to apply search filters
read = rscdx needed to read search results
write = wrscdx needed to modify/rename
manage = mwrscdx needed to manage

Each level implies all lower levels of access. So, for example, granting someone write access to an entry also grants them read, search, compare, auth and disclose access. However, one may use the privileges specifier to grant specific permissions.

8.2.4. Access Control Evaluation

When evaluating whether some requester should be given access to an entry and/or attribute, slapd compares the entry and/or attribute to the <what> selectors given in the configuration file. For each entry, access controls provided in the database which holds the entry (or the global access directives if not held in any database) apply first, followed by the global access directives. However, when dealing with an access list, because the global access list is effectively appended to each per-database list, if the resulting list is non-empty then the access list will end with an implicit access to * by * none directive. If there are no access directives applicable to a backend, then a default read is used.

Within this priority, access directives are examined in the order in which they appear in the config file. Slapd stops with the first <what> selector that matches the entry and/or attribute. The corresponding access directive is the one slapd will use to evaluate access.

Next, slapd compares the entity requesting access to the <who> selectors within the access directive selected above in the order in which they appear. It stops with the first <who> selector that matches the requester. This determines the access the entity requesting access has to the entry and/or attribute.

Finally, slapd compares the access granted in the selected <access> clause to the access requested by the client. If it allows greater or equal access, access is granted. Otherwise, access is denied.

The order of evaluation of access directives makes their placement in the configuration file important. If one access directive is more specific than another in terms of the entries it selects, it should appear first in the config file. Similarly, if one <who> selector is more specific than another it should come first in the access directive. The access control examples given below should help make this clear.

8.2.5. Access Control Examples

The access control facility described above is quite powerful. This section shows some examples of its use for descriptive purposes.

A simple example:

    access to * by * read

This access directive grants read access to everyone.

    access to *
        by self write
        by anonymous auth
        by * read

This directive allows the user to modify their entry, allows anonymous to authentication against these entries, and allows all others to read these entries. Note that only the first by <who> clause which matches applies. Hence, the anonymous users are granted auth, not read. The last clause could just as well have been "by users read".

It is often desirable to restrict operations based upon the level of protection in place. The following shows how security strength factors (SSF) can be used.

    access to *
        by ssf=128 self write
        by ssf=64 anonymous auth
        by ssf=64 users read

This directive allows users to modify their own entries if security protections have of strength 128 or better have been established, allows authentication access to anonymous users, and read access when 64 or better security protections have been established. If client has not establish sufficient security protections, the implicit by * none clause would be applied.

The following example shows the use of a style specifiers to select the entries by DN in two access directives where ordering is significant.

    access to dn.children="dc=example,dc=com"
         by * search
    access to dn.children="dc=com"
         by * read

Read access is granted to entries under the dc=com subtree, except for those entries under the dc=example,dc=com subtree, to which search access is granted. No access is granted to dc=com as neither access directive matches this DN. If the order of these access directives was reversed, the trailing directive would never be reached, since all entries under dc=example,dc=com are also under dc=com entries.

Also note that if no access to directive matches or no by <who> clause, access is denied. That is, every access to directive ends with an implicit by * none clause. When dealing with an access list, because the global access list is effectively appended to each per-database list, if the resulting list is non-empty then the access list will end with an implicit access to * by * none directive. If there are no access directives applicable to a backend, then a default read is used.

The next example again shows the importance of ordering, both of the access directives and the by <who> clauses. It also shows the use of an attribute selector to grant access to a specific attribute and various <who> selectors.

    access to dn.subtree="dc=example,dc=com" attrs=homePhone
        by self write
        by dn.children="dc=example,dc=com" search
        by peername.regex=IP:10\..+ read
    access to dn.subtree="dc=example,dc=com"
        by self write
        by dn.children="dc=example,dc=com" search
        by anonymous auth

This example applies to entries in the "dc=example,dc=com" subtree. To all attributes except homePhone, an entry can write to itself, entries under example.com entries can search by them, anybody else has no access (implicit by * none) excepting for authentication/authorization (which is always done anonymously). The homePhone attribute is writable by the entry, searchable by entries under example.com, readable by clients connecting from network 10, and otherwise not readable (implicit by * none). All other access is denied by the implicit access to * by * none.

Sometimes it is useful to permit a particular DN to add or remove itself from an attribute. For example, if you would like to create a group and allow people to add and remove only their own DN from the member attribute, you could accomplish it with an access directive like this:

    access to attrs=member,entry
         by dnattr=member selfwrite

The dnattr <who> selector says that the access applies to entries listed in the member attribute. The selfwrite access selector says that such members can only add or delete their own DN from the attribute, not other values. The addition of the entry attribute is required because access to the entry is required to access any of the entry's attributes.

8.3. Access Control via Dynamic Configuration

Access to slapd entries and attributes is controlled by the olcAccess attribute, whose values are a sequence of access directives. The general form of the olcAccess configuration is:

    olcAccess: <access directive>
    <access directive> ::= to <what>
        [by <who> [<access>] [<control>] ]+
    <what> ::= * |
        [dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>]
        [filter=<ldapfilter>] [attrs=<attrlist>]
    <basic-style> ::= regex | exact
    <scope-style> ::= base | one | subtree | children
    <attrlist> ::= <attr> [val[.<basic-style>]=<regex>] | <attr> , <attrlist>
    <attr> ::= <attrname> | entry | children
    <who> ::= * | [anonymous | users | self
            | dn[.<basic-style>]=<regex> | dn.<scope-style>=<DN>]
        [dnattr=<attrname>]
        [group[/<objectclass>[/<attrname>][.<basic-style>]]=<regex>]
        [peername[.<basic-style>]=<regex>]
        [sockname[.<basic-style>]=<regex>]
        [domain[.<basic-style>]=<regex>]
        [sockurl[.<basic-style>]=<regex>]
        [set=<setspec>]
        [aci=<attrname>]
    <access> ::= [self]{<level>|<priv>}
    <level> ::= none | disclose | auth | compare | search | read | write | manage
    <priv> ::= {=|+|-}{m|w|r|s|c|x|d|0}+
    <control> ::= [stop | continue | break]

where the <what> part selects the entries and/or attributes to which the access applies, the <who> part specifies which entities are granted access, and the <access> part specifies the access granted. Multiple <who> <access> <control> triplets are supported, allowing many entities to be granted different access to the same set of entries and attributes. Not all of these access control options are described here; for more details see the slapd.access(5) man page.

8.3.1. What to control access to

The <what> part of an access specification determines the entries and attributes to which the access control applies. Entries are commonly selected in two ways: by DN and by filter. The following qualifiers select entries by DN:

    to *
    to dn[.<basic-style>]=<regex>
    to dn.<scope-style>=<DN>

The first form is used to select all entries. The second form may be used to select entries by matching a regular expression against the target entry's normalized DN. (The second form is not discussed further in this document.) The third form is used to select entries which are within the requested scope of DN. The <DN> is a string representation of the Distinguished Name, as described in RFC4514.

The scope can be either base, one, subtree, or children. Where base matches only the entry with provided DN, one matches the entries whose parent is the provided DN, subtree matches all entries in the subtree whose root is the provided DN, and children matches all entries under the DN (but not the entry named by the DN).

For example, if the directory contained entries named:

    0: o=suffix
    1: cn=Manager,o=suffix
    2: ou=people,o=suffix
    3: uid=kdz,ou=people,o=suffix
    4: cn=addresses,uid=kdz,ou=people,o=suffix
    5: uid=hyc,ou=people,o=suffix

Then:

Entries may also be selected using a filter:

    to filter=<ldap filter>

where <ldap filter> is a string representation of an LDAP search filter, as described in RFC4515. For example:

    to filter=(objectClass=person)

Note that entries may be selected by both DN and filter by including both qualifiers in the <what> clause.

    to dn.one="ou=people,o=suffix" filter=(objectClass=person)

Attributes within an entry are selected by including a comma-separated list of attribute names in the <what> selector:

    attrs=<attribute list>

A specific value of an attribute is selected by using a single attribute name and also using a value selector:

    attrs=<attribute> val[.<style>]=<regex>

There are two special pseudo attributes entry and children. To read (and hence return) a target entry, the subject must have read access to the target's entry attribute. To perform a search, the subject must have search access to the search base's entry attribute. To add or delete an entry, the subject must have write access to the entry's entry attribute AND must have write access to the entry's parent's children attribute. To rename an entry, the subject must have write access to entry's entry attribute AND have write access to both the old parent's and new parent's children attributes. The complete examples at the end of this section should help clear things up.

Lastly, there is a special entry selector "*" that is used to select any entry. It is used when no other <what> selector has been provided. It's equivalent to "dn=.*"

8.3.2. Who to grant access to

The <who> part identifies the entity or entities being granted access. Note that access is granted to "entities" not "entries." The following table summarizes entity specifiers:

Table 5.3: Access Entity Specifiers
Specifier Entities
* All, including anonymous and authenticated users
anonymous Anonymous (non-authenticated) users
users Authenticated users
self User associated with target entry
dn[.<basic-style>]=<regex> Users matching a regular expression
dn.<scope-style>=<DN> Users within scope of a DN

The DN specifier behaves much like <what> clause DN specifiers.

Other control factors are also supported. For example, a <who> can be restricted by an entry listed in a DN-valued attribute in the entry to which the access applies:

    dnattr=<dn-valued attribute name>

The dnattr specification is used to give access to an entry whose DN is listed in an attribute of the entry (e.g., give access to a group entry to whoever is listed as the owner of the group entry).

Some factors may not be appropriate in all environments (or any). For example, the domain factor relies on IP to domain name lookups. As these can easily be spoofed, the domain factor should be avoided.

8.3.3. The access to grant

The kind of <access> granted can be one of the following:

Table 5.4: Access Levels
Level Privileges Description
none =0 no access
disclose =d needed for information disclosure on error
auth =dx needed to authenticate (bind)
compare =cdx needed to compare
search =scdx needed to apply search filters
read =rscdx needed to read search results
write =wrscdx needed to modify/rename
manage =mwrscdx needed to manage

Each level implies all lower levels of access. So, for example, granting someone write access to an entry also grants them read, search, compare, auth and disclose access. However, one may use the privileges specifier to grant specific permissions.

8.3.4. Access Control Evaluation

When evaluating whether some requester should be given access to an entry and/or attribute, slapd compares the entry and/or attribute to the <what> selectors given in the configuration. For each entry, access controls provided in the database which holds the entry (or the global access directives if not held in any database) apply first, followed by the global access directives (which are held in the frontend database definition). However, when dealing with an access list, because the global access list is effectively appended to each per-database list, if the resulting list is non-empty then the access list will end with an implicit access to * by * none directive. If there are no access directives applicable to a backend, then a default read is used.

Within this priority, access directives are examined in the order in which they appear in the configuration attribute. Slapd stops with the first <what> selector that matches the entry and/or attribute. The corresponding access directive is the one slapd will use to evaluate access.

Next, slapd compares the entity requesting access to the <who> selectors within the access directive selected above in the order in which they appear. It stops with the first <who> selector that matches the requester. This determines the access the entity requesting access has to the entry and/or attribute.

Finally, slapd compares the access granted in the selected <access> clause to the access requested by the client. If it allows greater or equal access, access is granted. Otherwise, access is denied.

The order of evaluation of access directives makes their placement in the configuration file important. If one access directive is more specific than another in terms of the entries it selects, it should appear first in the configuration. Similarly, if one <who> selector is more specific than another it should come first in the access directive. The access control examples given below should help make this clear.

8.3.5. Access Control Examples

The access control facility described above is quite powerful. This section shows some examples of its use for descriptive purposes.

A simple example:

    olcAccess: to * by * read

This access directive grants read access to everyone.

    olcAccess: to *
        by self write
        by anonymous auth
        by * read

This directive allows the user to modify their entry, allows anonymous to authenticate against these entries, and allows all others to read these entries. Note that only the first by <who> clause which matches applies. Hence, the anonymous users are granted auth, not read. The last clause could just as well have been "by users read".

It is often desirable to restrict operations based upon the level of protection in place. The following shows how security strength factors (SSF) can be used.

    olcAccess: to *
        by ssf=128 self write
        by ssf=64 anonymous auth
        by ssf=64 users read

This directive allows users to modify their own entries if security protections of strength 128 or better have been established, allows authentication access to anonymous users, and read access when strength 64 or better security protections have been established. If the client has not establish sufficient security protections, the implicit by * none clause would be applied.

The following example shows the use of style specifiers to select the entries by DN in two access directives where ordering is significant.

    olcAccess: to dn.children="dc=example,dc=com"
         by * search
    olcAccess: to dn.children="dc=com"
         by * read

Read access is granted to entries under the dc=com subtree, except for those entries under the dc=example,dc=com subtree, to which search access is granted. No access is granted to dc=com as neither access directive matches this DN. If the order of these access directives was reversed, the trailing directive would never be reached, since all entries under dc=example,dc=com are also under dc=com entries.

Also note that if no olcAccess: to directive matches or no by <who> clause, access is denied. When dealing with an access list, because the global access list is effectively appended to each per-database list, if the resulting list is non-empty then the access list will end with an implicit access to * by * none directive. If there are no access directives applicable to a backend, then a default read is used.

The next example again shows the importance of ordering, both of the access directives and the by <who> clauses. It also shows the use of an attribute selector to grant access to a specific attribute and various <who> selectors.

    olcAccess: to dn.subtree="dc=example,dc=com" attrs=homePhone
        by self write
        by dn.children=dc=example,dc=com" search
        by peername.regex=IP:10\..+ read
    olcAccess: to dn.subtree="dc=example,dc=com"
        by self write
        by dn.children="dc=example,dc=com" search
        by anonymous auth

This example applies to entries in the "dc=example,dc=com" subtree. To all attributes except homePhone, an entry can write to itself, entries under example.com entries can search by them, anybody else has no access (implicit by * none) excepting for authentication/authorization (which is always done anonymously). The homePhone attribute is writable by the entry, searchable by entries under example.com, readable by clients connecting from network 10, and otherwise not readable (implicit by * none). All other access is denied by the implicit access to * by * none.

Sometimes it is useful to permit a particular DN to add or remove itself from an attribute. For example, if you would like to create a group and allow people to add and remove only their own DN from the member attribute, you could accomplish it with an access directive like this:

    olcAccess: to attrs=member,entry
         by dnattr=member selfwrite

The dnattr <who> selector says that the access applies to entries listed in the member attribute. The selfwrite access selector says that such members can only add or delete their own DN from the attribute, not other values. The addition of the entry attribute is required because access to the entry is required to access any of the entry's attributes.

8.3.6. Access Control Ordering

Since the ordering of olcAccess directives is essential to their proper evaluation, but LDAP attributes normally do not preserve the ordering of their values, OpenLDAP uses a custom schema extension to maintain a fixed ordering of these values. This ordering is maintained by prepending a "{X}" numeric index to each value, similarly to the approach used for ordering the configuration entries. These index tags are maintained automatically by slapd and do not need to be specified when originally defining the values. For example, when you create the settings

    olcAccess: to attrs=member,entry
         by dnattr=member selfwrite
    olcAccess: to dn.children="dc=example,dc=com"
         by * search
    olcAccess: to dn.children="dc=com"
         by * read

when you read them back using slapcat or ldapsearch they will contain

    olcAccess: {0}to attrs=member,entry
         by dnattr=member selfwrite
    olcAccess: {1}to dn.children="dc=example,dc=com"
         by * search
    olcAccess: {2}to dn.children="dc=com"
         by * read

The numeric index may be used to specify a particular value to change when using ldapmodify to edit the access rules. This index can be used instead of (or in addition to) the actual access value. Using this numeric index is very helpful when multiple access rules are being managed.

For example, if we needed to change the second rule above to grant write access instead of search, we could try this LDIF:

    changetype: modify
    delete: olcAccess
    olcAccess: to dn.children="dc=example,dc=com" by * search
    -
    add: olcAccess
    olcAccess: to dn.children="dc=example,dc=com" by * write
    -

But this example will not guarantee that the existing values remain in their original order, so it will most likely yield a broken security configuration. Instead, the numeric index should be used:

    changetype: modify
    delete: olcAccess
    olcAccess: {1}
    -
    add: olcAccess
    olcAccess: {1}to dn.children="dc=example,dc=com" by * write
    -

This example deletes whatever rule is in value #1 of the olcAccess attribute (regardless of its value) and adds a new value that is explicitly inserted as value #1. The result will be

    olcAccess: {0}to attrs=member,entry
         by dnattr=member selfwrite
    olcAccess: {1}to dn.children="dc=example,dc=com"
         by * write
    olcAccess: {2}to dn.children="dc=com"
         by * read

which is exactly what was intended.

8.4. Access Control Common Examples

8.4.1. Basic ACLs

Generally one should start with some basic ACLs such as:

    access to attr=userPassword
        by self =xw
        by anonymous auth
        by * none


      access to *
        by self write
        by users read
        by * none

The first ACL allows users to update (but not read) their passwords, anonymous users to authenticate against this attribute, and (implicitly) denying all access to others.

The second ACL allows users full access to their entry, authenticated users read access to anything, and (implicitly) denying all access to others (in this case, anonymous users).

8.4.2. Matching Anonymous and Authenticated users

An anonymous user has a empty DN. While the dn.exact="" or dn.regex="^$" could be used, slapd(8)) offers an anonymous shorthand which should be used instead.

    access to *
      by anonymous none
      by * read

denies all access to anonymous users while granting others read.

Authenticated users have a subject DN. While dn.regex=".+" will match any authenticated user, OpenLDAP provides the users short hand which should be used instead.

    access to *
      by users read
      by * none

This ACL grants read permissions to authenticated users while denying others (i.e.: anonymous users).

8.4.3. Controlling rootdn access

You could specify the rootdn in slapd.conf(5) or slapd.d without specifying a rootpw. Then you have to add an actual directory entry with the same dn, e.g.:

    dn: cn=Manager,o=MyOrganization
    cn: Manager
    sn: Manager
    objectClass: person
    objectClass: top
    userPassword: {SSHA}someSSHAdata

Then binding as the rootdn will require a regular bind to that DN, which in turn requires auth access to that entry's DN and userPassword, and this can be restricted via ACLs. E.g.:

    access to dn.base="cn=Manager,o=MyOrganization"
      by peername.regex=127\.0\.0\.1 auth
      by peername.regex=192\.168\.0\..* auth
      by users none
      by * none

The ACLs above will only allow binding using rootdn from localhost and 192.168.0.0/24.

8.4.4. Managing access with Groups

There are a few ways to do this. One approach is illustrated here. Consider the following DIT layout:

    +-dc=example,dc=com
    +---cn=administrators,dc=example,dc=com
    +---cn=fred blogs,dc=example,dc=com

and the following group object (in LDIF format):

    dn: cn=administrators,dc=example,dc=com
    cn: administrators of this region
    objectclass: groupOfNames  (important for the group acl feature)
    member: cn=fred blogs,dc=example,dc=com
    member: cn=somebody else,dc=example,dc=com

One can then grant access to the members of this this group by adding appropriate by group clause to an access directive in slapd.conf(5). For instance,

    access to dn.children="dc=example,dc=com"
        by self write
        by group.exact="cn=Administrators,dc=example,dc=com" write
        by * auth

Like by dn clauses, one can also use expand to expand the group name based upon the regular expression matching of the target, that is, the to dn.regex). For instance,

    access to dn.regex="(.+,)?ou=People,(dc=[^,]+,dc=[^,]+)$"
             attrs=children,entry,uid
        by group.expand="cn=Managers,$2" write
        by users read
        by * auth

The above illustration assumed that the group members are to be found in the member attribute type of the groupOfNames object class. If you need to use a different group object and/or a different attribute type then use the following slapd.conf(5) (abbreviated) syntax:

    access to <what>
            by group/<objectclass>/<attributename>=<DN> <access>

For example:

    access to *
      by group/organizationalRole/roleOccupant="cn=Administrator,dc=example,dc=com" write

In this case, we have an ObjectClass organizationalRole which contains the administrator DN's in the roleOccupant attribute. For instance:

    dn: cn=Administrator,dc=example,dc=com
    cn: Administrator
    objectclass: organizationalRole
    roleOccupant: cn=Jane Doe,dc=example,dc=com


Note: the specified member attribute type MUST be of DN or NameAndOptionalUID syntax, and the specified object class SHOULD allow the attribute type.

Dynamic Groups are also supported in Access Control. Please see slapo-dynlist(5) and the Dynamic Lists overlay section.

8.4.5. Granting access to a subset of attributes

You can grant access to a set of attributes by specifying a list of attribute names in the ACL to clause. To be useful, you also need to grant access to the entry itself. Also note how children controls the ability to add, delete, and rename entries.

    # mail: self may write, authenticated users may read
    access to attrs=mail
      by self write
      by users read
      by * none

    # cn, sn: self my write, all may read
    access to attrs=cn,sn
      by self write
      by * read

    # immediate children: only self can add/delete entries under this entry
    access to attrs=children
      by self write

    # entry itself: self may write, all may read
    access to attrs=entry
      by self write
      by * read

    # other attributes: self may write, others have no access
    access to *
      by self write
      by * none

ObjectClass names may also be specified in this list, which will affect all the attributes that are required and/or allowed by that objectClass. Actually, names in attrlist that are prefixed by @ are directly treated as objectClass names. A name prefixed by ! is also treated as an objectClass, but in this case the access rule affects the attributes that are not required nor allowed by that objectClass.

8.4.6. Allowing a user write to all entries below theirs

For a setup where a user can write to its own record and to all of its children:

    access to dn.regex="(.+,)?(uid=[^,]+,o=Company)$"
       by dn.exact,expand="$2" write
       by anonymous auth

(Add more examples for above)

8.4.7. Allowing entry creation

Let's say, you have it like this:

        o=<basedn>
            ou=domains
                associatedDomain=<somedomain>
                    ou=users
                        uid=<someuserid>
                        uid=<someotheruserid>
                    ou=addressbooks
                        uid=<someuserid>
                            cn=<someone>
                            cn=<someoneelse>

and, for another domain <someotherdomain>:

        o=<basedn>
            ou=domains
                associatedDomain=<someotherdomain>
                    ou=users
                        uid=<someuserid>
                        uid=<someotheruserid>
                    ou=addressbooks
                        uid=<someotheruserid>
                            cn=<someone>
                            cn=<someoneelse>

then, if you wanted user uid=<someuserid> to ONLY create an entry for its own thing, you could write an ACL like this:

    # this rule lets users of "associatedDomain=<matcheddomain>"
    # write under "ou=addressbook,associatedDomain=<matcheddomain>,ou=domains,o=<basedn>",
    # i.e. a user can write ANY entry below its domain's address book;
    # this permission is necessary, but not sufficient, the next
    # will restrict this permission further


    access to dn.regex="^ou=addressbook,associatedDomain=([^,]+),ou=domains,o=<basedn>$" attrs=children
            by dn.regex="^uid=([^,]+),ou=users,associatedDomain=$1,ou=domains,o=<basedn>$$" write
            by * none


    # Note that above the "by" clause needs a "regex" style to make sure
    # it expands to a DN that starts with a "uid=<someuserid>" pattern
    # while substituting the associatedDomain submatch from the "what" clause.


    # This rule lets a user with "uid=<matcheduid>" of "<associatedDomain=matcheddomain>"
    # write (i.e. add, modify, delete) the entry whose DN is exactly
    # "uid=<matcheduid>,ou=addressbook,associatedDomain=<matcheddomain>,ou=domains,o=<basedn>"
    # and ANY entry as subtree of it


    access to dn.regex="^(.+,)?uid=([^,]+),ou=addressbook,associatedDomain=([^,]+),ou=domains,o=<basedn>$"
            by dn.exact,expand="uid=$2,ou=users,associatedDomain=$3,ou=domains,o=<basedn>" write
            by * none


    # Note that above the "by" clause uses the "exact" style with the "expand"
    # modifier because now the whole pattern can be rebuilt by means of the
    # submatches from the "what" clause, so a "regex" compilation and evaluation
    # is no longer required.

8.4.8. Tips for using regular expressions in Access Control

Always use dn.regex=<pattern> when you intend to use regular expression matching. dn=<pattern> alone defaults to dn.exact<pattern>.

Use (.+) instead of (.*) when you want at least one char to be matched. (.*) matches the empty string as well.

Don't use regular expressions for matches that can be done otherwise in a safer and cheaper manner. Examples:

    dn.regex=".*dc=example,dc=com"

is unsafe and expensive:

    dn.subtree="dc=example,dc=com"

to include dc=example,dc=com in the matching patterns,

    dn.children="dc=example,dc=com"

to exclude dc=example,dc=com from the matching patterns, or

    dn.onelevel="dc=example,dc=com"

to allow exactly one sublevel matches only.

Always use ^ and $ in regexes, whenever appropriate, because ou=(.+),ou=(.+),ou=addressbooks,o=basedn will match something=bla,ou=xxx,ou=yyy,ou=addressbooks,o=basedn,ou=addressbooks,o=basedn,dc=some,dc=org

Always use ([^,]+) to indicate exactly one RDN, because (.+) can include any number of RDNs; e.g. ou=(.+),dc=example,dc=com will match ou=My,o=Org,dc=example,dc=com, which might not be what you want.

Never add the rootdn to the by clauses. ACLs are not even processed for operations performed with rootdn identity (otherwise there would be no reason to define a rootdn at all).

Use shorthands. The user directive matches authenticated users and the anonymous directive matches anonymous users.

Don't use the dn.regex form for <by> clauses if all you need is scoping and/or substring replacement; use scoping styles (e.g. exact, onelevel, children or subtree) and the style modifier expand to cause substring expansion.

For instance,

    access to dn.regex=".+,dc=([^,]+),dc=([^,]+)$"
      by dn.regex="^[^,],ou=Admin,dc=$1,dc=$2$$" write

although correct, can be safely and efficiently replaced by

    access to dn.regex=".+,(dc=[^,]+,dc=[^,]+)$"
      by dn.onelevel,expand="ou=Admin,$1" write

where the regex in the <what> clause is more compact, and the one in the <by> clause is replaced by a much more efficient scoping style of onelevel with substring expansion.

8.4.9. Granting and Denying access based on security strength factors (ssf)

You can restrict access based on the security strength factor (SSF)

    access to dn="cn=example,cn=edu"
          by * ssf=256 read

0 (zero) implies no protection, 1 implies integrity protection only, 56 DES or other weak ciphers, 112 triple DES and other strong ciphers, 128 RC4, Blowfish and other modern strong ciphers.

Other possibilities:

    transport_ssf=<n>
    tls_ssf=<n>
    sasl_ssf=<n>

256 is recommended.

See slapd.conf(5) for information on ssf.

8.4.10. When things aren't working as expected

Consider this example:

    access to *
      by anonymous auth

    access to *
      by self write

    access to *
      by users read

You may think this will allow any user to login, to read everything and change his own data if he is logged in. But in this example only the login works and an ldapsearch returns no data. The Problem is that SLAPD goes through its access config line by line and stops as soon as it finds a match in the part of the access rule.(here: to *)

To get what we wanted the file has to read:

    access to *
      by anonymous auth
      by self write
      by users read

The general rule is: "special access rules first, generic access rules last"

See also slapd.access(5), loglevel 128 and slapacl(8) for debugging information.

8.5. Sets - Granting rights based on relationships

Sets are best illustrated via examples. The following sections will present a few set ACL examples in order to facilitate their understanding.

(Sets in Access Controls FAQ Entry: http://www.openldap.org/faq/data/cache/1133.html)


Note: Sets are considered experimental.

8.5.1. Groups of Groups

The OpenLDAP ACL for groups doesn't expand groups within groups, which are groups that have another group as a member. For example:

 dn: cn=sudoadm,ou=group,dc=example,dc=com
 cn: sudoadm
 objectClass: groupOfNames
 member: uid=john,ou=people,dc=example,dc=com
 member: cn=accountadm,ou=group,dc=example,dc=com

 dn: cn=accountadm,ou=group,dc=example,dc=com
 cn: accountadm
 objectClass: groupOfNames
 member: uid=mary,ou=people,dc=example,dc=com

If we use standard group ACLs with the above entries and allow members of the sudoadm group to write somewhere, mary won't be included:

 access to dn.subtree="ou=sudoers,dc=example,dc=com"
         by group.exact="cn=sudoadm,ou=group,dc=example,dc=com" write
         by * read

With sets we can make the ACL be recursive and consider group within groups. So for each member that is a group, it is further expanded:

 access to dn.subtree="ou=sudoers,dc=example,dc=com"
       by set="[cn=sudoadm,ou=group,dc=example,dc=com]/member* & user" write
       by * read

This set ACL means: take the cn=sudoadm DN, check its member attribute(s) (where the "*" means recursively) and intersect the result with the authenticated user's DN. If the result is non-empty, the ACL is considered a match and write access is granted.

The following drawing explains how this set is built:

Figure X.Y: Populating a recursive group set

First we get the uid=john DN. This entry doesn't have a member attribute, so the expansion stops here. Now we get to cn=accountadm. This one does have a member attribute, which is uid=mary. The uid=mary entry, however, doesn't have member, so we stop here again. The end comparison is:

 {"uid=john,ou=people,dc=example,dc=com","uid=mary,ou=people,dc=example,dc=com"} & user

If the authenticated user's DN is any one of those two, write access is granted. So this set will include mary in the sudoadm group and she will be allowed the write access.

8.5.2. Group ACLs without DN syntax

The traditional group ACLs, and even the previous example about recursive groups, require that the members are specified as DNs instead of just usernames.

With sets, however, it's also possible to use simple names in group ACLs, as this example will show.

Let's say we want to allow members of the sudoadm group to write to the ou=suders branch of our tree. But our group definition now is using memberUid for the group members:

 dn: cn=sudoadm,ou=group,dc=example,dc=com
 cn: sudoadm
 objectClass: posixGroup
 gidNumber: 1000
 memberUid: john

With this type of group, we can't use group ACLs. But with a set ACL we can grant the desired access:

 access to dn.subtree="ou=sudoers,dc=example,dc=com"
       by set="[cn=sudoadm,ou=group,dc=example,dc=com]/memberUid & user/uid" write
       by * read

We use a simple intersection where we compare the uid attribute of the connecting (and authenticated) user with the memberUid attributes of the group. If they match, the intersection is non-empty and the ACL will grant write access.

This drawing illustrates this set when the connecting user is authenticated as uid=john,ou=people,dc=example,dc=com:

Figure X.Y: Sets with memberUid

In this case, it's a match. If it were mary authenticating, however, she would be denied write access to ou=sudoers because her uid attribute is not listed in the group's memberUid.

8.5.3. Following references

We will now show a quite powerful example of what can be done with sets. This example tends to make OpenLDAP administrators smile after they have understood it and its implications.

Let's start with an user entry:

 dn: uid=john,ou=people,dc=example,dc=com
 uid: john
 objectClass: inetOrgPerson
 givenName: John
 sn: Smith
 cn: john
 manager: uid=mary,ou=people,dc=example,dc=com

Writing an ACL to allow the manager to update some attributes is quite simple using sets:

 access to dn.exact="uid=john,ou=people,dc=example,dc=com"
    attrs=carLicense,homePhone,mobile,pager,telephoneNumber
    by self write
    by set="this/manager & user" write
    by * read

In that set, this expands to the entry being accessed, so that this/manager expands to uid=mary,ou=people,dc=example,dc=com when john's entry is accessed. If the manager herself is accessing John's entry, the ACL will match and write access to those attributes will be granted.

So far, this same behavior can be obtained with the dnattr keyword. With sets, however, we can further enhance this ACL. Let's say we want to allow the secretary of the manager to also update these attributes. This is how we do it:

 access to dn.exact="uid=john,ou=people,dc=example,dc=com"
    attrs=carLicense,homePhone,mobile,pager,telephoneNumber
    by self write
    by set="this/manager & user" write
    by set="this/manager/secretary & user" write
    by * read

Now we need a picture to help explain what is happening here (entries shortened for clarity):

Figure X.Y: Sets jumping through entries

In this example, Jane is the secretary of Mary, which is the manager of John. This whole relationship is defined with the manager and secretary attributes, which are both of the distinguishedName syntax (i.e., full DNs). So, when the uid=john entry is being accessed, the this/manager/secretary set becomes {"uid=jane,ou=people,dc=example,dc=com"} (follow the references in the picture):

 this = [uid=john,ou=people,dc=example,dc=com]
 this/manager = \
   [uid=john,ou=people,dc=example,dc=com]/manager = uid=mary,ou=people,dc=example,dc=com
 this/manager/secretary = \
   [uid=mary,ou=people,dc=example,dc=com]/secretary = uid=jane,ou=people,dc=example,dc=com

The end result is that when Jane accesses John's entry, she will be granted write access to the specified attributes. Better yet, this will happen to any entry she accesses which has Mary as the manager.

This is all cool and nice, but perhaps gives too much power to secretaries. Maybe we need to further restrict it. For example, let's only allow executive secretaries to have this power:

 access to dn.exact="uid=john,ou=people,dc=example,dc=com"
   attrs=carLicense,homePhone,mobile,pager,telephoneNumber
   by self write
   by set="this/manager & user" write
   by set="this/manager/secretary &
           [cn=executive,ou=group,dc=example,dc=com]/member* &
           user" write
   by * read

It's almost the same ACL as before, but we now also require that the connecting user be a member of the (possibly nested) cn=executive group.


9. Limits

9.1. Introduction

It is usually desirable to limit the server resources that can be consumed by each LDAP client. OpenLDAP provides two sets of limits: a size limit, which can restrict the number of entries that a client can retrieve in a single operation, and a time limit which restricts the length of time that an operation may continue. Both types of limit can be given different values depending on who initiated the operation.

9.2. Soft and Hard limits

The server administrator can specify both soft limits and hard limits. Soft limits can be thought of as being the default limit value. Hard limits cannot be exceeded by ordinary LDAP users.

LDAP clients can specify their own size and time limits when issuing search operations. This feature has been present since the earliest version of X.500.

If the client specifies a limit then the lower of the requested value and the hard limit will become the limit for the operation.

If the client does not specify a limit then the server applies the soft limit.

Soft and Hard limits are often referred to together as administrative limits. Thus, if an LDAP client requests a search that would return more results than the limits allow it will get an adminLimitExceeded error. Note that the server will usually return some results even if the limit has been exceeded: this feature is useful to clients that just want to check for the existence of some entries without needing to see them all.

The rootdn is not subject to any limits.

9.3. Global Limits

Limits specified in the global part of the server configuration act as defaults which are used if no database has more specific limits set.

In a slapd.conf(5) configuration the keywords are sizelimit and timelimit. When using the slapd config backend, the corresponding attributes are olcSizeLimit and olcTimeLimit. The syntax of these values are the same in both cases.

The simple form sets both soft and hard limits to the same value:

   sizelimit {<integer>|unlimited}
   timelimit {<integer>|unlimited}

The default sizelimit is 500 entries and the default timelimit is 3600 seconds.

An extended form allows soft and hard limits to be set separately:

   sizelimit size[.{soft|hard|unchecked}]=<integer> [...]
   timelimit time[.{soft|hard}]=<integer> [...]

Thus, to set a soft sizelimit of 10 entries and a hard limit of 75 entries:

  sizelimit size.soft=10 size.hard=75

The unchecked keyword sets a limit on how many entries the server will examine once it has created an initial set of candidate results by using indices. This can be very important in a large directory, as a search that cannot be satisfied from an index might cause the server to examine millions of entries, therefore always make sure the correct indexes are configured.

9.4. Per-Database Limits

Each database can have its own set of limits that override the global ones. The syntax is more flexible, and it allows different limits to be applied to different entities. Note that an entity is different from an entry: the term entity is used here to indicate the ID of the person or process that has initiated the LDAP operation.

In a slapd.conf(5) configuration the keyword is limits. When using the slapd config backend, the corresponding attribute is olcLimits. The syntax of the values is the same in both cases.

   limits <who> <limit> [<limit> [...]]

The limits clause can be specified multiple times to apply different limits to different initiators. The server examines each clause in turn until it finds one that matches the ID that requested the operation. If no match is found, the global limits will be used.

9.4.1. Specify who the limits apply to

The <who> part of the limits clause can take any of these values:

Table ZZZ.ZZZ: Entity Specifiers
Specifier Entities
* All, including anonymous and authenticated users
anonymous Anonymous (non-authenticated) users
users Authenticated users
self User associated with target entry
dn[.<basic-style>]=<regex> Users matching a regular expression
dn.<scope-style>=<DN> Users within scope of a DN
group[/oc[/at]]=<pattern> Members of a group

The rules for specifying <who> are the same as those used in access-control rules.

9.4.2. Specify time limits

The syntax for time limits is

   time[.{soft|hard}]=<integer>

where integer is the number of seconds slapd will spend answering a search request.

If neither soft nor hard is specified, the value is used for both, e.g.:

   limits anonymous time=27

The value unlimited may be used to remove the hard time limit entirely, e.g.:

   limits dn.exact="cn=anyuser,dc=example,dc=org" time.hard=unlimited

9.4.3. Specifying size limits

The syntax for size limit is

   size[.{soft|hard|unchecked}]=<integer>

where <integer> is the maximum number of entries slapd will return when answering a search request.

Soft, hard, and "unchecked" limits are available, with the same meanings described for the global limits configuration above.

9.4.4. Size limits and Paged Results

If the LDAP client adds the pagedResultsControl to the search operation, the hard size limit is used by default, because the request for a specific page size is considered an explicit request for a limitation on the number of entries to be returned. However, the size limit applies to the total count of entries returned within the search, and not to a single page.

Additional size limits may be enforced for paged searches.

The size.pr limit controls the maximum page size:

   size.pr={<integer>|noEstimate|unlimited}

<integer> is the maximum page size if no explicit size is set. noEstimate has no effect in the current implementation as the server does not return an estimate of the result size anyway. unlimited indicates that no limit is applied to the maximum page size.

The size.prtotal limit controls the total number of entries that can be returned by a paged search. By default the limit is the same as the normal size.hard limit.

   size.prtotal={<integer>|unlimited|disabled}

unlimited removes the limit on the number of entries that can be returned by a paged search. disabled can be used to selectively disable paged result searches.

9.5. Example Limit Configurations

9.5.1. Simple Global Limits

This simple global configuration fragment applies size and time limits to all searches by all users except rootdn. It limits searches to 50 results and sets an overall time limit of 10 seconds.

   sizelimit 50
   timelimit 10

9.5.2. Global Hard and Soft Limits

It is sometimes useful to limit the size of result sets but to allow clients to request a higher limit where needed. This can be achieved by setting separate hard and soft limits.

   sizelimit size.soft=5 size.hard=100

To prevent clients from doing very inefficient non-indexed searches, add the unchecked limit:

   sizelimit size.soft=5 size.hard=100 size.unchecked=100

9.5.3. Giving specific users larger limits

Having set appropriate default limits in the global configuration, you may want to give certain users the ability to retrieve larger result sets. Here is a way to do that in the per-database configuration:

   limits dn.exact="cn=anyuser,dc=example,dc=org" size=100000
   limits dn.exact="cn=personnel,dc=example,dc=org" size=100000
   limits dn.exact="cn=dirsync,dc=example,dc=org" size=100000

It is generally best to avoid mentioning specific users in the server configuration. A better way is to give the higher limits to a group:

   limits group/groupOfNames/member="cn=bigwigs,dc=example,dc=org" size=100000

9.5.4. Limiting who can do paged searches

It may be required that certain applications need very large result sets that they retrieve using paged searches, but that you do not want ordinary LDAP users to use the pagedResults control. The pr and prtotal limits can help:

   limits group/groupOfNames/member="cn=dirsync,dc=example,dc=org" size.prtotal=unlimited
   limits users size.soft=5 size.hard=100 size.prtotal=disabled
   limits anonymous size.soft=2 size.hard=5 size.prtotal=disabled

9.6. Further Information

For further information please see slapd.conf(5), ldapsearch(1) and slapd.access(5)


10. Database Creation and Maintenance Tools

This section tells you how to create a slapd database from scratch, and how to do trouble shooting if you run into problems. There are two ways to create a database. First, you can create the database on-line using LDAP. With this method, you simply start up slapd and add entries using the LDAP client of your choice. This method is fine for relatively small databases (a few hundred or thousand entries, depending on your requirements). This method works for database types which support updates.

The second method of database creation is to do it off-line using special utilities provided with slapd(8). This method is best if you have many thousands of entries to create, which would take an unacceptably long time using the LDAP method, or if you want to ensure the database is not accessed while it is being created. Note that not all database types support these utilities.

10.1. Creating a database over LDAP

With this method, you use the LDAP client of your choice (e.g., the ldapadd(1)) to add entries, just like you would once the database is created. You should be sure to set the following options in the configuration file before starting slapd(8).

        suffix <dn>

As described in the General Database Directives section, this option defines which entries are to be held by this database. You should set this to the DN of the root of the subtree you are trying to create. For example:

        suffix "dc=example,dc=com"

You should be sure to specify a directory where the index files should be created:

        directory <directory>

For example:

        directory /usr/local/var/openldap-data

You need to create this directory with appropriate permissions such that slapd can write to it.

You need to configure slapd so that you can connect to it as a directory user with permission to add entries. You can configure the directory to support a special super-user or root user just for this purpose. This is done through the following two options in the database definition:

        rootdn <dn>
        rootpw <passwd>

For example:

        rootdn "cn=Manager,dc=example,dc=com"
        rootpw secret

These options specify a DN and password that can be used to authenticate as the super-user entry of the database (i.e., the entry allowed to do anything). The DN and password specified here will always work, regardless of whether the entry named actually exists or has the password given. This solves the chicken-and-egg problem of how to authenticate and add entries before any entries yet exist.

Finally, you should make sure that the database definition contains the index definitions you want:

        index {<attrlist> | default} [pres,eq,approx,sub,none]

For example, to index the cn, sn, uid and objectclass attributes, the following index directives could be used:

        index cn,sn,uid pres,eq,approx,sub
        index objectClass eq

This would create presence, equality, approximate, and substring indices for the cn, sn, and uid attributes and an equality index for the objectClass attribute. Note that not all index types are available with all attribute types. See The slapd Configuration File section for more information on this option.

Once you have configured things to your liking, start up slapd, connect with your LDAP client, and start adding entries. For example, to add an organization entry and an organizational role entry using the ldapadd tool, you could create an LDIF file called entries.ldif with the contents:

        # Organization for Example Corporation
        dn: dc=example,dc=com
        objectClass: dcObject
        objectClass: organization
        dc: example
        o: Example Corporation
        description: The Example Corporation

        # Organizational Role for Directory Manager
        dn: cn=Manager,dc=example,dc=com
        objectClass: organizationalRole
        cn: Manager
        description: Directory Manager

and then use a command like this to actually create the entry:

        ldapadd -f entries.ldif -x -D "cn=Manager,dc=example,dc=com" -w secret

The above command assumes settings provided in the above examples.

10.2. Creating a database off-line

The second method of database creation is to do it off-line, using the slapd database tools described below. This method is best if you have many thousands of entries to create, which would take an unacceptably long time to add using the LDAP method described above. These tools read the slapd configuration file and an input file containing a text representation of the entries to add. For database types which support the tools, they produce the database files directly (otherwise you must use the on-line method above). There are several important configuration options you will want to be sure and set in the config file database definition first:

        suffix <dn>

As described in the General Database Directives section, this option defines which entries are to be held by this database. You should set this to the DN of the root of the subtree you are trying to create. For example:

        suffix "dc=example,dc=com"

You should be sure to specify a directory where the index files should be created:

        directory <directory>

For example:

        directory /usr/local/var/openldap-data

Finally, you need to specify which indices you want to build. This is done by one or more index options.

        index {<attrlist> | default} [pres,eq,approx,sub,none]

For example:

        index cn,sn,uid pres,eq,approx,sub
        index objectClass eq

This would create presence, equality, approximate, and substring indices for the cn, sn, and uid attributes and an equality index for the objectClass attribute. Note that not all index types are available with all attribute types. See The slapd Configuration File section for more information on this option.

10.2.1. The slapadd program

Once you've configured things to your liking, you create the primary database and associated indices by running the slapadd(8) program:

        slapadd -l <inputfile> -f <slapdconfigfile>
                [-d <debuglevel>] [-n <integer>|-b <suffix>]

The arguments have the following meanings:

        -l <inputfile>

Specifies the LDIF input file containing the entries to add in text form (described below in the The LDIF text entry format section).

        -f <slapdconfigfile>

Specifies the slapd configuration file that tells where to create the indices, what indices to create, etc.

        -F <slapdconfdirectory>

Specifies a config directory. If both -f and -F are specified, the config file will be read and converted to config directory format and written to the specified directory. If neither option is specified, an attempt to read the default config directory will be made before trying to use the default config file. If a valid config directory exists then the default config file is ignored. If dryrun mode is also specified, no conversion will occur.

        -d <debuglevel>

Turn on debugging, as specified by <debuglevel>. The debug levels are the same as for slapd. See the Command-Line Options section in Running slapd.

        -n <databasenumber>

An optional argument that specifies which database to modify. The first database listed in the configuration file is 1, the second 2, etc. By default, the first database in the configuration file is used. Should not be used in conjunction with -b.

        -b <suffix>

An optional argument that specifies which database to modify. The provided suffix is matched against a database suffix directive to determine the database number. Should not be used in conjunction with -n.

10.2.2. The slapindex program

Sometimes it may be necessary to regenerate indices (such as after modifying slapd.conf(5)). This is possible using the slapindex(8) program. slapindex is invoked like this

        slapindex -f <slapdconfigfile>
                [-d <debuglevel>] [-n <databasenumber>|-b <suffix>]

Where the -f, -d, -n and -b options are the same as for the slapadd(1) program. slapindex rebuilds all indices based upon the current database contents.

10.2.3. The slapcat program

The slapcat program is used to dump the database to an LDIF file. This can be useful when you want to make a human-readable backup of your database or when you want to edit your database off-line. The program is invoked like this:

        slapcat -l <filename> -f <slapdconfigfile>
                [-d <debuglevel>] [-n <databasenumber>|-b <suffix>]

where -n or -b is used to select the database in the slapd.conf(5) specified using -f. The corresponding LDIF output is written to standard output or to the file specified using the -l option.

10.3. The LDIF text entry format

The LDAP Data Interchange Format (LDIF) is used to represent LDAP entries in a simple text format. This section provides a brief description of the LDIF entry format which complements ldif(5) and the technical specification RFC2849.

The basic form of an entry is:

        # comment
        dn: <distinguished name>
        <attrdesc>: <attrvalue>
        <attrdesc>: <attrvalue>

        ...

Lines starting with a '#' character are comments. An attribute description may be a simple attribute type like cn or objectClass or 1.2.3 (an OID associated with an attribute type) or may include options such as cn;lang_en_US or userCertificate;binary.

A line may be continued by starting the next line with a single space or tab character. For example:

        dn: cn=Barbara J Jensen,dc=example,dc=
         com
        cn: Barbara J
          Jensen

is equivalent to:

        dn: cn=Barbara J Jensen,dc=example,dc=com
        cn: Barbara J Jensen

Multiple attribute values are specified on separate lines. e.g.,

        cn: Barbara J Jensen
        cn: Babs Jensen

If an <attrvalue> contains non-printing characters or begins with a space, a colon (':'), or a less than ('<'), the <attrdesc> is followed by a double colon and the base64 encoding of the value. For example, the value " begins with a space" would be encoded like this:

        cn:: IGJlZ2lucyB3aXRoIGEgc3BhY2U=

You can also specify a URL containing the attribute value. For example, the following specifies the jpegPhoto value should be obtained from the file /path/to/file.jpeg.

        cn:< file:///path/to/file.jpeg

Multiple entries within the same LDIF file are separated by blank lines. Here's an example of an LDIF file containing three entries.

        # Barbara's Entry
        dn: cn=Barbara J Jensen,dc=example,dc=com
        cn: Barbara J Jensen
        cn: Babs Jensen
        objectClass: person
        sn: Jensen

        # Bjorn's Entry
        dn: cn=Bjorn J Jensen,dc=example,dc=com
        cn: Bjorn J Jensen
        cn: Bjorn Jensen
        objectClass: person
        sn: Jensen
        # Base64 encoded JPEG photo
        jpegPhoto:: /9j/4AAQSkZJRgABAAAAAQABAAD/2wBDABALD
         A4MChAODQ4SERATGCgaGBYWGDEjJR0oOjM9PDkzODdASFxOQ
         ERXRTc4UG1RV19iZ2hnPk1xeXBkeFxlZ2P/2wBDARESEhgVG

        # Jennifer's Entry
        dn: cn=Jennifer J Jensen,dc=example,dc=com
        cn: Jennifer J Jensen
        cn: Jennifer Jensen
        objectClass: person
        sn: Jensen
        # JPEG photo from file
        jpegPhoto:< file:///path/to/file.jpeg

Notice that the jpegPhoto in Bjorn's entry is base 64 encoded and the jpegPhoto in Jennifer's entry is obtained from the location indicated by the URL.


Note: Trailing spaces are not trimmed from values in an LDIF file. Nor are multiple internal spaces compressed. If you don't want them in your data, don't put them there.


11. Backends

Backends do the actual work of storing or retrieving data in response to LDAP requests. Backends may be compiled statically into slapd, or when module support is enabled, they may be dynamically loaded.

If your installation uses dynamic modules, you may need to add the relevant moduleload directives to the examples that follow. The name of the module for a backend is usually of the form:

        back_<backend name>.la

So for example, if you need to load the hdb backend, you would configure

        moduleload back_hdb.la

11.1. Berkeley DB Backends

11.1.1. Overview

The hdb backend to slapd(8) is the recommended primary backend for a normal slapd database. It uses the Oracle Berkeley DB (BDB) package to store data. It makes extensive use of indexing and caching (see the Tuning section) to speed data access.

hdb is a variant of the original bdb backend which was first written for use with BDB. hdb uses a hierarchical database layout which supports subtree renames. It is otherwise identical to the bdb behavior, and all the same configuration options apply.


Note: An hdb database needs a large idlcachesize for good search performance, typically three times the cachesize (entry cache size) or larger.


Note: The hdb backend has superseded the bdb backend, and both will soon be deprecated in favor of the new mdb backend. See below.

11.1.2. back-bdb/back-hdb Configuration

MORE LATER

11.1.3. Further Information

slapd-bdb(5)

11.2. LDAP

11.2.1. Overview

The LDAP backend to slapd(8) is not an actual database; instead it acts as a proxy to forward incoming requests to another LDAP server. While processing requests it will also chase referrals, so that referrals are fully processed instead of being returned to the slapd client.

Sessions that explicitly Bind to the back-ldap database always create their own private connection to the remote LDAP server. Anonymous sessions will share a single anonymous connection to the remote server. For sessions bound through other mechanisms, all sessions with the same DN will share the same connection. This connection pooling strategy can enhance the proxy's efficiency by reducing the overhead of repeatedly making/breaking multiple connections.

The ldap database can also act as an information service, i.e. the identity of locally authenticated clients is asserted to the remote server, possibly in some modified form. For this purpose, the proxy binds to the remote server with some administrative identity, and, if required, authorizes the asserted identity.

It is heavily used by a lot of other Backends and Overlays.

11.2.2. back-ldap Configuration

As previously mentioned, slapd-ldap(5) is used behind the scenes by many other Backends and Overlays. Some of them merely provide a few configuration directive themselves, but have available to the administrator the whole of the slapd-ldap(5) options.

For example, the Translucent Proxy, which retrieves entries from a remote LDAP server that can be partially overridden by the defined database, has only four specific translucent- directives, but can be configured using any of the normal slapd-ldap(5) options. See {[slapo-translucent(5)}} for details.

Other Overlays allow you to tag directives in front of a normal slapd-ldap(5) directive. For example, the slapo-chain(5) overlay does this:

"There are very few chain overlay specific directives; however, directives related to the instances of the ldap backend that may be implicitly instantiated by the overlay may assume a special meaning when used in conjunction with this overlay. They are described in slapd-ldap(5), and they also need to be prefixed by chain-."

You may have also seen the slapd-ldap(5) backend used and described in the Push Based Replication section of the guide.

It should therefore be obvious that the slapd-ldap(5) backend is extremely flexible and heavily used throughout the OpenLDAP Suite.

The following is a very simple example, but already the power of the slapd-ldap(5) backend is seen by use of a uri list:

        database        ldap
        suffix          "dc=suretecsystems,dc=com"
        rootdn          "cn=slapd-ldap"
        uri             ldap://localhost/ ldap://remotehost ldap://remotehost2

The URI list is space or comma-separated. Whenever the server that responds is not the first one in the list, the list is rearranged and the responsive server is moved to the head, so that it will be first contacted the next time a connection needs be created.

This feature can be used to provide a form of load balancing when using MirrorMode replication.

11.2.3. Further Information

slapd-ldap(5)

11.3. LDIF

11.3.1. Overview

The LDIF backend to slapd(8) is a basic storage backend that stores entries in text files in LDIF format, and exploits the filesystem to create the tree structure of the database. It is intended as a cheap, low performance easy to use backend.

When using the cn=config dynamic configuration database with persistent storage, the configuration data is stored using this backend. See slapd-config(5) for more information

11.3.2. back-ldif Configuration

Like many other backends, the LDIF backend can be instantiated with very few configuration lines:

        include ./schema/core.schema

        database  ldif
        directory ./ldif
        suffix    "dc=suretecsystems,dc=com"
        rootdn    "cn=LDIF,dc=suretecsystems,dc=com"
        rootpw    LDIF

If we add the dcObject for dc=suretecsystems,dc=com, you can see how this is added behind the scenes on the file system:

   dn: dc=suretecsystems,dc=com
   objectClass: dcObject
   objectClass: organization
   dc: suretecsystems
   o: Suretec Systems Ltd

Now we add it to the directory:

   ldapadd -x -H ldap://localhost:9011 -f suretec.ldif -D "cn=LDIF,dc=suretecsystems,dc=com" -w LDIF
   adding new entry "dc=suretecsystems,dc=com"

And inside ./ldif we have:

   ls ./ldif
   dc=suretecsystems,dc=com.ldif

which again contains:

   cat ldif/dc\=suretecsystems\,dc\=com.ldif

   dn: dc=suretecsystems
   objectClass: dcObject
   objectClass: organization
   dc: suretecsystems
   o: Suretec Systems Ltd.
   structuralObjectClass: organization
   entryUUID: 2134b714-e3a1-102c-9a15-f96ee263886d
   creatorsName: cn=LDIF,dc=suretecsystems,dc=com
   createTimestamp: 20080711142643Z
   entryCSN: 20080711142643.661124Z#000000#000#000000
   modifiersName: cn=LDIF,dc=suretecsystems,dc=com
   modifyTimestamp: 20080711142643Z

This is the complete format you would get when exporting your directory using slapcat etc.

11.3.3. Further Information

slapd-ldif(5)

11.4. LMDB

11.4.1. Overview

The mdb backend to slapd(8) is the upcoming primary backend for a normal slapd database. It uses OpenLDAP's own Lightning Memory-Mapped Database (LMDB) library to store data and is intended to replace the Berkeley DB backends.

It supports indexing like the BDB backends, but it uses no caching and requires no tuning to deliver maximum search performance. Like hdb, it is also fully hierarchical and supports subtree renames in constant time.

11.4.2. back-mdb Configuration

Unlike the BDB backends, the mdb backend can be instantiated with very few configuration lines:

        include ./schema/core.schema

        database  mdb
        directory ./mdb
        suffix    "dc=suretecsystems,dc=com"
        rootdn    "cn=mdb,dc=suretecsystems,dc=com"
        rootpw    mdb
        maxsize   1073741824

In addition to the usual parameters that a minimal configuration requires, the mdb backend requires a maximum size to be set. This should be the largest that the database is ever anticipated to grow (in bytes). The filesystem must also provide enough free space to accommodate this size.

11.4.3. Further Information

slapd-mdb(5)

11.5. Metadirectory

11.5.1. Overview

The meta backend to slapd(8) performs basic LDAP proxying with respect to a set of remote LDAP servers, called "targets". The information contained in these servers can be presented as belonging to a single Directory Information Tree (DIT).

A basic knowledge of the functionality of the slapd-ldap(5) backend is recommended. This backend has been designed as an enhancement of the ldap backend. The two backends share many features (actually they also share portions of code). While the ldap backend is intended to proxy operations directed to a single server, the meta backend is mainly intended for proxying of multiple servers and possibly naming context masquerading.

These features, although useful in many scenarios, may result in excessive overhead for some applications, so its use should be carefully considered.

11.5.2. back-meta Configuration

LATER

11.5.3. Further Information

slapd-meta(5)

11.6. Monitor

11.6.1. Overview

The monitor backend to slapd(8) is not an actual database; if enabled, it is automatically generated and dynamically maintained by slapd with information about the running status of the daemon.

To inspect all monitor information, issue a subtree search with base cn=Monitor, requesting that attributes "+" and "*" are returned. The monitor backend produces mostly operational attributes, and LDAP only returns operational attributes that are explicitly requested. Requesting attribute "+" is an extension which requests all operational attributes.

See the Monitoring section.

11.6.2. back-monitor Configuration

The monitor database can be instantiated only once, i.e. only one occurrence of "database monitor" can occur in the slapd.conf(5) file. Also the suffix is automatically set to "cn=Monitor".

You can however set a rootdn and rootpw. The following is all that is needed to instantiate a monitor backend:

        include ./schema/core.schema

        database monitor
        rootdn "cn=monitoring,cn=Monitor"
        rootpw monitoring

You can also apply Access Control to this database like any other database, for example:

        access to dn.subtree="cn=Monitor"
             by dn.exact="uid=Admin,dc=my,dc=org" write
             by users read
             by * none


Note: The core.schema must be loaded for the monitor database to work.

A small example of the data returned via ldapsearch would be:

        ldapsearch -x -H ldap://localhost:9011 -b 'cn=Monitor'
        # extended LDIF
        #
        # LDAPv3
        # base <cn=Monitor> with scope subtree
        # filter: (objectclass=*)
        # requesting: ALL
        #

        # Monitor
        dn: cn=Monitor
        objectClass: monitorServer
        cn: Monitor
        description: This subtree contains monitoring/managing objects.
        description: This object contains information about this server.
        description: Most of the information is held in operational attributes, which
         must be explicitly requested.

        # Backends, Monitor
        dn: cn=Backends,cn=Monitor
        objectClass: monitorContainer
        cn: Backends
        description: This subsystem contains information about available backends.

Please see the Monitoring section for complete examples of information available via this backend.

11.6.3. Further Information

slapd-monitor(5)

11.7. Null

11.7.1. Overview

The Null backend to slapd(8) is surely the most useful part of slapd:

Inspired by the /dev/null device.

11.7.2. back-null Configuration

This has to be one of the shortest configurations you'll ever do. In order to test this, your slapd.conf file would look like:

        database null
        suffix "cn=Nothing"
        bind on

bind on means:

"Allow binds as any DN in this backend's suffix, with any password. The default is "off"."

To test this backend with ldapsearch:

        ldapsearch -x -H ldap://localhost:9011 -D "uid=none,cn=Nothing" -w testing -b 'cn=Nothing'
        # extended LDIF
        #
        # LDAPv3
        # base <cn=Nothing> with scope subtree
        # filter: (objectclass=*)
        # requesting: ALL
        #

        # search result
        search: 2
        result: 0 Success

        # numResponses: 1

11.7.3. Further Information

slapd-null(5)

11.8. Passwd

11.8.1. Overview

The PASSWD backend to slapd(8) serves up the user account information listed in the system passwd(5) file (defaulting to /etc/passwd).

This backend is provided for demonstration purposes only. The DN of each entry is "uid=<username>,<suffix>".

11.8.2. back-passwd Configuration

The configuration using slapd.conf a slightly longer, but not much. For example:

        include ./schema/core.schema

        database passwd
        suffix "cn=passwd"

Again, testing this with ldapsearch would result in something like:

        ldapsearch -x -H ldap://localhost:9011 -b 'cn=passwd'
        # extended LDIF
        #
        # LDAPv3
        # base <cn=passwd> with scope subtree
        # filter: (objectclass=*)
        # requesting: ALL
        #

        # passwd
        dn: cn=passwd
        cn: passwd
        objectClass: organizationalUnit

        # root, passwd
        dn: uid=root,cn=passwd
        objectClass: person
        objectClass: uidObject
        uid: root
        cn: root
        sn: root
        description: root

11.8.3. Further Information

slapd-passwd(5)

11.9. Perl/Shell

11.9.1. Overview

The Perl backend to slapd(8) works by embedding a perl(1) interpreter into slapd(8). Any perl database section of the configuration file slapd.conf(5) must then specify what Perl module to use. Slapd then creates a new Perl object that handles all the requests for that particular instance of the backend.

The Shell backend to slapd(8) executes external programs to implement operations, and is designed to make it easy to tie an existing database to the slapd front-end. This backend is is primarily intended to be used in prototypes.

11.9.2. back-perl/back-shell Configuration

LATER

11.9.3. Further Information

slapd-shell(5) and slapd-perl(5)

11.10. Relay

11.10.1. Overview

The primary purpose of this slapd(8) backend is to map a naming context defined in a database running in the same slapd(8) instance into a virtual naming context, with attributeType and objectClass manipulation, if required. It requires the rwm overlay.

This backend and the above mentioned overlay are experimental.

11.10.2. back-relay Configuration

LATER

11.10.3. Further Information

slapd-relay(5)

11.11. SQL

11.11.1. Overview

The primary purpose of this slapd(8) backend is to PRESENT information stored in some RDBMS as an LDAP subtree without any programming (some SQL and maybe stored procedures can't be considered programming, anyway ;).

That is, for example, when you (some ISP) have account information you use in an RDBMS, and want to use modern solutions that expect such information in LDAP (to authenticate users, make email lookups etc.). Or you want to synchronize or distribute information between different sites/applications that use RDBMSes and/or LDAP. Or whatever else...

It is NOT designed as a general-purpose backend that uses RDBMS instead of BerkeleyDB (as the standard BDB backend does), though it can be used as such with several limitations. Please see LDAP vs RDBMS for discussion.

The idea is to use some meta-information to translate LDAP queries to SQL queries, leaving relational schema untouched, so that old applications can continue using it without any modifications. This allows SQL and LDAP applications to interoperate without replication, and exchange data as needed.

The SQL backend is designed to be tunable to virtually any relational schema without having to change source (through that meta-information mentioned). Also, it uses ODBC to connect to RDBMSes, and is highly configurable for SQL dialects RDBMSes may use, so it may be used for integration and distribution of data on different RDBMSes, OSes, hosts etc., in other words, in highly heterogeneous environments.

This backend is experimental.

11.11.2. back-sql Configuration

This backend has to be one of the most abused and complex backends there is. Therefore, we will go through a simple, small example that comes with the OpenLDAP source and can be found in servers/slapd/back-sql/rdbms_depend/README

For this example we will be using PostgreSQL.

First, we add to /etc/odbc.ini a block of the form:

        [example]                        <===
        Description         = Example for OpenLDAP's back-sql
        Driver              = PostgreSQL
        Trace               = No
        Database            = example    <===
        Servername          = localhost
        UserName            = manager    <===
        Password            = secret     <===
        Port                = 5432
        ;Protocol            = 6.4
        ReadOnly            = No
        RowVersioning       = No
        ShowSystemTables    = No
        ShowOidColumn       = No
        FakeOidIndex        = No
        ConnSettings        =

The relevant information for our test setup is highlighted with '<===' on the right above.

Next, we add to /etc/odbcinst.ini a block of the form:

        [PostgreSQL]
        Description     = ODBC for PostgreSQL
        Driver          = /usr/lib/libodbcpsql.so
        Setup           = /usr/lib/libodbcpsqlS.so
        FileUsage       = 1

We will presume you know how to create a database and user in PostgreSQL and how to set a password. Also, we'll presume you can populate the 'example' database you've just created with the following files, as found in servers/slapd/back-sql/rdbms_depend/pgsql

        backsql_create.sql, testdb_create.sql, testdb_data.sql, testdb_metadata.sql

Lastly, run the test:

        [root@localhost]# cd $SOURCES/tests
        [root@localhost]# SLAPD_USE_SQL=pgsql ./run sql-test000

Briefly, you should see something like (cut short for space):

        Cleaning up test run directory leftover from previous run.
        Running ./scripts/sql-test000-read...
        running defines.sh
        Starting slapd on TCP/IP port 9011...
        Testing SQL backend read operations...
        Waiting 5 seconds for slapd to start...
        Testing correct bind... dn:cn=Mitya Kovalev,dc=example,dc=com
        Testing incorrect bind (should fail)... ldap_bind: Invalid credentials (49)

        ......

        Filtering original ldif...
        Comparing filter output...
        >>>>> Test succeeded

The test is basically readonly; this can be performed by all RDBMSes (listed above).

There is another test, sql-test900-write, which is currently enabled only for PostgreSQL and IBM db2.

Using sql-test000, files in servers/slapd/back-sql/rdbms_depend/pgsql/ and the man page, you should be set.


Note: This backend is experimental.

11.11.3. Further Information

slapd-sql(5) and servers/slapd/back-sql/rdbms_depend/README


12. Overlays

Overlays are software components that provide hooks to functions analogous to those provided by backends, which can be stacked on top of the backend calls and as callbacks on top of backend responses to alter their behavior.

Overlays may be compiled statically into slapd, or when module support is enabled, they may be dynamically loaded. Most of the overlays are only allowed to be configured on individual databases.

Some can be stacked on the frontend as well, for global use. This means that they can be executed after a request is parsed and validated, but right before the appropriate database is selected. The main purpose is to affect operations regardless of the database they will be handled by, and, in some cases, to influence the selection of the database by massaging the request DN.

Essentially, overlays represent a means to:

When using slapd.conf(5), overlays that are configured before any other databases are considered global, as mentioned above. In fact they are implicitly stacked on top of the frontend database. They can also be explicitly configured as such:

        database frontend
        overlay <overlay name>

Overlays are usually documented by separate specific man pages in section 5; the naming convention is

        slapo-<overlay name>

All distributed core overlays have a man page. Feel free to contribute to any, if you think there is anything missing in describing the behavior of the component and the implications of all the related configuration directives.

Official overlays are located in

        servers/slapd/overlays/

That directory also contains the file slapover.txt, which describes the rationale of the overlay implementation, and may serve as a guideline for the development of custom overlays.

Contribware overlays are located in

        contrib/slapd-modules/<overlay name>/

along with other types of run-time loadable components; they are officially distributed, but not maintained by the project.

All the current overlays in OpenLDAP are listed and described in detail in the following sections.

12.1. Access Logging

12.1.1. Overview

This overlay can record accesses to a given backend database on another database.

This allows all of the activity on a given database to be reviewed using arbitrary LDAP queries, instead of just logging to local flat text files. Configuration options are available for selecting a subset of operation types to log, and to automatically prune older log records from the logging database. Log records are stored with audit schema to assure their readability whether viewed as LDIF or in raw form.

It is also used for delta-syncrepl replication

12.1.2. Access Logging Configuration

The following is a basic example that implements Access Logging:

        database bdb
        suffix dc=example,dc=com
        ...
        overlay accesslog
        logdb cn=log
        logops writes reads
        logold (objectclass=person)

        database bdb
        suffix cn=log
        ...
        index reqStart eq
        access to *
          by dn.base="cn=admin,dc=example,dc=com" read

The following is an example used for delta-syncrepl replication:

        database hdb
        suffix cn=accesslog
        directory /usr/local/var/openldap-accesslog
        rootdn cn=accesslog
        index default eq
        index entryCSN,objectClass,reqEnd,reqResult,reqStart

Accesslog overlay definitions for the primary db

        database bdb
        suffix dc=example,dc=com
        ...
        overlay accesslog
        logdb cn=accesslog
        logops writes
        logsuccess TRUE
        # scan the accesslog DB every day, and purge entries older than 7 days
        logpurge 07+00:00 01+00:00

An example search result against cn=accesslog might look like:

        [ghenry@suretec ghenry]# ldapsearch -x -b cn=accesslog
        # extended LDIF
        #
        # LDAPv3
        # base <cn=accesslog> with scope subtree
        # filter: (objectclass=*)
        # requesting: ALL
        #

        # accesslog
        dn: cn=accesslog
        objectClass: auditContainer
        cn: accesslog

        # 20080110163829.000004Z, accesslog
        dn: reqStart=20080110163829.000004Z,cn=accesslog
        objectClass: auditModify
        reqStart: 20080110163829.000004Z
        reqEnd: 20080110163829.000005Z
        reqType: modify
        reqSession: 196696
        reqAuthzID: cn=admin,dc=suretecsystems,dc=com
        reqDN: uid=suretec-46022f8$,ou=Users,dc=suretecsystems,dc=com
        reqResult: 0
        reqMod: sambaPwdCanChange:- ###CENSORED###
        reqMod: sambaPwdCanChange:+ ###CENSORED###
        reqMod: sambaNTPassword:- ###CENSORED###
        reqMod: sambaNTPassword:+ ###CENSORED###
        reqMod: sambaPwdLastSet:- ###CENSORED###
        reqMod: sambaPwdLastSet:+ ###CENSORED###
        reqMod: entryCSN:= 20080110163829.095157Z#000000#000#000000
        reqMod: modifiersName:= cn=admin,dc=suretecsystems,dc=com
        reqMod: modifyTimestamp:= 20080110163829Z

        # search result
        search: 2
        result: 0 Success

        # numResponses: 3
        # numEntries: 2

12.1.3. Further Information

slapo-accesslog(5) and the delta-syncrepl replication section.

12.2. Audit Logging

The Audit Logging overlay can be used to record all changes on a given backend database to a specified log file.

12.2.1. Overview

If the need arises whereby changes need to be logged as standard LDIF, then the auditlog overlay slapo-auditlog (5) can be used. Full examples are available in the man page slapo-auditlog (5)

12.2.2. Audit Logging Configuration

If the directory is running vi slapd.d, then the following LDIF could be used to add the overlay to the overlay list in cn=config and set what file the LDIF gets logged to (adjust to suit)

       dn: olcOverlay=auditlog,olcDatabase={1}hdb,cn=config
       changetype: add
       objectClass: olcOverlayConfig
       objectClass: olcAuditLogConfig
       olcOverlay: auditlog
       olcAuditlogFile: /tmp/auditlog.ldif

In this example for testing, we are logging changes to /tmp/auditlog.ldif

A typical LDIF file created by slapo-auditlog(5) would look like:

       # add 1196797576 dc=suretecsystems,dc=com cn=admin,dc=suretecsystems,dc=com
       dn: dc=suretecsystems,dc=com
       changetype: add
       objectClass: dcObject
       objectClass: organization
       dc: suretecsystems
       o: Suretec Systems Ltd.
       structuralObjectClass: organization
       entryUUID: 1606f8f8-f06e-1029-8289-f0cc9d81e81a
       creatorsName: cn=admin,dc=suretecsystems,dc=com
       modifiersName: cn=admin,dc=suretecsystems,dc=com
       createTimestamp: 20051123130912Z
       modifyTimestamp: 20051123130912Z
       entryCSN: 20051123130912.000000Z#000001#000#000000
       auditContext: cn=accesslog
       # end add 1196797576

       # add 1196797577 dc=suretecsystems,dc=com cn=admin,dc=suretecsystems,dc=com
       dn: ou=Groups,dc=suretecsystems,dc=com
       changetype: add
       objectClass: top
       objectClass: organizationalUnit
       ou: Groups
       structuralObjectClass: organizationalUnit
       entryUUID: 160aaa2a-f06e-1029-828a-f0cc9d81e81a
       creatorsName: cn=admin,dc=suretecsystems,dc=com
       modifiersName: cn=admin,dc=suretecsystems,dc=com
       createTimestamp: 20051123130912Z
       modifyTimestamp: 20051123130912Z
       entryCSN: 20051123130912.000000Z#000002#000#000000
       # end add 1196797577

12.2.3. Further Information

slapo-auditlog(5)

12.3. Chaining

12.3.1. Overview

The chain overlay provides basic chaining capability to the underlying database.

What is chaining? It indicates the capability of a DSA to follow referrals on behalf of the client, so that distributed systems are viewed as a single virtual DSA by clients that are otherwise unable to "chase" (i.e. follow) referrals by themselves.

The chain overlay is built on top of the ldap backend; it is compiled by default when --enable-ldap.

12.3.2. Chaining Configuration

In order to demonstrate how this overlay works, we shall discuss a typical scenario which might be one master server and three Syncrepl slaves.

On each replica, add this near the top of the slapd.conf(5) file (global), before any database definitions:

        overlay                    chain
        chain-uri                  "ldap://ldapmaster.example.com"
        chain-idassert-bind        bindmethod="simple"
                                   binddn="cn=Manager,dc=example,dc=com"
                                   credentials="<secret>"
                                   mode="self"
        chain-tls                  start
        chain-return-error         TRUE

Add this below your syncrepl statement:

        updateref                  "ldap://ldapmaster.example.com/"

The chain-tls statement enables TLS from the slave to the ldap master. The DITs are exactly the same between these machines, therefore whatever user bound to the slave will also exist on the master. If that DN does not have update privileges on the master, nothing will happen.

You will need to restart the slave after these slapd.conf changes. Then, if you are using loglevel stats (256), you can monitor an ldapmodify on the slave and the master. (If you're using cn=config no restart is required.)

Now start an ldapmodify on the slave and watch the logs. You should expect something like:

        Sep  6 09:27:25 slave1 slapd[29274]: conn=11 fd=31 ACCEPT from IP=143.199.102.216:45181 (IP=143.199.102.216:389)
        Sep  6 09:27:25 slave1 slapd[29274]: conn=11 op=0 STARTTLS
        Sep  6 09:27:25 slave1 slapd[29274]: conn=11 op=0 RESULT oid= err=0 text=
        Sep  6 09:27:25 slave1 slapd[29274]: conn=11 fd=31 TLS established tls_ssf=256 ssf=256
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=1 BIND dn="uid=user1,ou=people,dc=example,dc=com" method=128
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=1 BIND dn="uid=user1,ou=People,dc=example,dc=com" mech=SIMPLE ssf=0
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=1 RESULT tag=97 err=0 text=
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=2 MOD dn="uid=user1,ou=People,dc=example,dc=com"
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=2 MOD attr=mail
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=2 RESULT tag=103 err=0 text=
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 op=3 UNBIND
        Sep  6 09:27:28 slave1 slapd[29274]: conn=11 fd=31 closed
        Sep  6 09:27:28 slave1 slapd[29274]: syncrepl_entry: LDAP_RES_SEARCH_ENTRY(LDAP_SYNC_MODIFY)
        Sep  6 09:27:28 slave1 slapd[29274]: syncrepl_entry: be_search (0)
        Sep  6 09:27:28 slave1 slapd[29274]: syncrepl_entry: uid=user1,ou=People,dc=example,dc=com
        Sep  6 09:27:28 slave1 slapd[29274]: syncrepl_entry: be_modify (0)

And on the master you will see this:

        Sep  6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 PROXYAUTHZ dn="uid=user1,ou=people,dc=example,dc=com"
        Sep  6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 MOD dn="uid=user1,ou=People,dc=example,dc=com"
        Sep  6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 MOD attr=mail
        Sep  6 09:23:57 ldapmaster slapd[2961]: conn=55902 op=3 RESULT tag=103 err=0 text=


Note: You can clearly see the PROXYAUTHZ line on the master, indicating the proper identity assertion for the update on the master. Also note the slave immediately receiving the Syncrepl update from the master.

12.3.3. Handling Chaining Errors

By default, if chaining fails, the original referral is returned to the client under the assumption that the client might want to try and follow the referral.

With the following directive however, if the chaining fails at the provider side, the actual error is returned to the client.

        chain-return-error TRUE

12.3.4. Read-Back of Chained Modifications

Occasionally, applications want to read back the data that they just wrote. If a modification requested to a shadow server was silently chained to its provider, an immediate read could result in receiving data not yet synchronized. In those cases, clients should use the dontusecopy control to ensure they are directed to the authoritative source for that piece of data.

This control usually causes a referral to the actual source of the data to be returned. However, when the slapo-chain(5) overlay is used, it intercepts the referral being returned in response to the dontusecopy control, and tries to fetch the requested data.

12.3.5. Further Information

slapo-chain(5)

12.4. Constraints

12.4.1. Overview

This overlay enforces a regular expression constraint on all values of specified attributes during an LDAP modify request that contains add or modify commands. It is used to enforce a more rigorous syntax when the underlying attribute syntax is too general.

12.4.2. Constraint Configuration

Configuration via slapd.conf(5) would look like:

        overlay constraint
        constraint_attribute mail regex ^[[:alnum:]]+@mydomain.com$
        constraint_attribute title uri
        ldap:///dc=catalog,dc=example,dc=com?title?sub?(objectClass=titleCatalog)

A specification like the above would reject any mail attribute which did not look like <alpha-numeric string>@mydomain.com.

It would also reject any title attribute whose values were not listed in the title attribute of any titleCatalog entries in the given scope.

An example for use with cn=config:

       dn: olcOverlay=constraint,olcDatabase={1}hdb,cn=config
       changetype: add
       objectClass: olcOverlayConfig
       objectClass: olcConstraintConfig
       olcOverlay: constraint
       olcConstraintAttribute: mail regex ^[[:alnum:]]+@mydomain.com$
       olcConstraintAttribute: title uri ldap:///dc=catalog,dc=example,dc=com?title?sub?(objectClass=titleCatalog)

12.4.3. Further Information

slapo-constraint(5)

12.5. Dynamic Directory Services

12.5.1. Overview

The dds overlay to slapd(8) implements dynamic objects as per RFC2589. The name dds stands for Dynamic Directory Services. It allows to define dynamic objects, characterized by the dynamicObject objectClass.

Dynamic objects have a limited lifetime, determined by a time-to-live (TTL) that can be refreshed by means of a specific refresh extended operation. This operation allows to set the Client Refresh Period (CRP), namely the period between refreshes that is required to preserve the dynamic object from expiration. The expiration time is computed by adding the requested TTL to the current time. When dynamic objects reach the end of their lifetime without being further refreshed, they are automatically deleted. There is no guarantee of immediate deletion, so clients should not count on it.

12.5.2. Dynamic Directory Service Configuration

A usage of dynamic objects might be to implement dynamic meetings; in this case, all the participants to the meeting are allowed to refresh the meeting object, but only the creator can delete it (otherwise it will be deleted when the TTL expires).

If we add the overlay to an example database, specifying a Max TTL of 1 day, a min of 10 seconds, with a default TTL of 1 hour. We'll also specify an interval of 120 (less than 60s might be too small) seconds between expiration checks and a tolerance of 5 second (lifetime of a dynamic object will be entryTtl + tolerance).

       overlay dds
       dds-max-ttl     1d
       dds-min-ttl     10s
       dds-default-ttl 1h
       dds-interval    120s
       dds-tolerance   5s

and add an index:

       entryExpireTimestamp

Creating a meeting is as simple as adding the following:

       dn: cn=OpenLDAP Documentation Meeting,ou=Meetings,dc=example,dc=com
       objectClass: groupOfNames
       objectClass: dynamicObject
       cn: OpenLDAP Documentation Meeting
       member: uid=ghenry,ou=People,dc=example,dc=com
       member: uid=hyc,ou=People,dc=example,dc=com

12.5.2.1. Dynamic Directory Service ACLs

Allow users to start a meeting and to join it; restrict refresh to the member; restrict delete to the creator:

       access to attrs=userPassword
          by self write
          by * read

       access to dn.base="ou=Meetings,dc=example,dc=com"
                 attrs=children
            by users write

       access to dn.onelevel="ou=Meetings,dc=example,dc=com"
                 attrs=entry
            by dnattr=creatorsName write
            by * read

       access to dn.onelevel="ou=Meetings,dc=example,dc=com"
                 attrs=participant
            by dnattr=creatorsName write
            by users selfwrite
            by * read

       access to dn.onelevel="ou=Meetings,dc=example,dc=com"
                 attrs=entryTtl
            by dnattr=member manage
            by * read

In simple terms, the user who created the OpenLDAP Documentation Meeting can add new attendees, refresh the meeting using (basically complete control):

       ldapexop -x -H ldap://ldaphost "refresh" "cn=OpenLDAP Documentation Meeting,ou=Meetings,dc=example,dc=com" "120" -D "uid=ghenry,ou=People,dc=example,dc=com" -W

Any user can join the meeting, but not add another attendee, but they can refresh the meeting. The ACLs above are quite straight forward to understand.

12.5.3. Further Information

slapo-dds(5)

12.6. Dynamic Groups

12.6.1. Overview

This overlay extends the Compare operation to detect members of a dynamic group. This overlay is now deprecated as all of its functions are available using the Dynamic Lists overlay.

12.6.2. Dynamic Group Configuration

12.7. Dynamic Lists

12.7.1. Overview

This overlay allows expansion of dynamic groups and lists. Instead of having the group members or list attributes hard coded, this overlay allows us to define an LDAP search whose results will make up the group or list.

12.7.2. Dynamic List Configuration

This module can behave both as a dynamic list and dynamic group, depending on the configuration. The syntax is as follows:

       overlay dynlist
       dynlist-attrset <group-oc> <URL-ad> [member-ad]

The parameters to the dynlist-attrset directive have the following meaning:

Here is an example which will allow us to have an email alias which automatically expands to all user's emails according to our LDAP filter:

In slapd.conf(5):

       overlay dynlist
       dynlist-attrset nisMailAlias labeledURI

This means that whenever an entry which has the nisMailAlias object class is retrieved, the search specified in the labeledURI attribute is performed.

Let's say we have this entry in our directory:

       cn=all,ou=aliases,dc=example,dc=com
       cn: all
       objectClass: nisMailAlias
       labeledURI: ldap:///ou=People,dc=example,dc=com?mail?one?(objectClass=inetOrgPerson)

If this entry is retrieved, the search specified in labeledURI will be performed and the results will be added to the entry just as if they have always been there. In this case, the search filter selects all entries directly under ou=People that have the inetOrgPerson object class and retrieves the mail attribute, if it exists.

This is what gets added to the entry when we have two users under ou=People that match the filter:

Figure X.Y: Dynamic List for all emails

The configuration for a dynamic group is similar. Let's see an example which would automatically populate an allusers group with all the user accounts in the directory.

In slapd.conf(5):

       include /path/to/dyngroup.schema
       ...
       overlay dynlist
       dynlist-attrset groupOfURLs labeledURI member
  1. Note: We must include the dyngroup.schema file that defines the
  2. groupOfURLs objectClass used in this example.

Let's apply it to the following entry:

       cn=allusers,ou=group,dc=example,dc=com
       cn: all
       objectClass: groupOfURLs
       labeledURI: ldap:///ou=people,dc=example,dc=com??one?(objectClass=inetOrgPerson)

The behavior is similar to the dynamic list configuration we had before: whenever an entry with the groupOfURLs object class is retrieved, the search specified in the labeledURI attribute is performed. But this time, only the distinguished names of the results are added, and as values of the member attribute.

This is what we get:

Figure X.Y: Dynamic Group for all users

Note that a side effect of this scheme of dynamic groups is that the members need to be specified as full DNs. So, if you are planning in using this for posixGroups, be sure to use RFC2307bis and some attribute which can hold distinguished names. The memberUid attribute used in the posixGroup object class can hold only names, not DNs, and is therefore not suitable for dynamic groups.

12.7.3. Further Information

slapo-dynlist(5)

12.8. Reverse Group Membership Maintenance

12.8.1. Overview

In some scenarios, it may be desirable for a client to be able to determine which groups an entry is a member of, without performing an additional search. Examples of this are applications using the DIT for access control based on group authorization.

The memberof overlay updates an attribute (by default memberOf) whenever changes occur to the membership attribute (by default member) of entries of the objectclass (by default groupOfNames) configured to trigger updates.

Thus, it provides maintenance of the list of groups an entry is a member of, when usual maintenance of groups is done by modifying the members on the group entry.

12.8.2. Member Of Configuration

The typical use of this overlay requires just enabling the overlay for a specific database. For example, with the following minimal slapd.conf:

        include /usr/share/openldap/schema/core.schema
        include /usr/share/openldap/schema/cosine.schema

        authz-regexp "gidNumber=0\\\+uidNumber=0,cn=peercred,cn=external,cn=auth"
                "cn=Manager,dc=example,dc=com"
        database        bdb
        suffix          "dc=example,dc=com"
        rootdn          "cn=Manager,dc=example,dc=com"
        rootpw          secret
        directory       /var/lib/ldap2.4
        checkpoint 256 5
        index   objectClass   eq
        index   uid           eq,sub

        overlay memberof

adding the following ldif:

        cat memberof.ldif
        dn: dc=example,dc=com
        objectclass: domain
        dc: example

        dn: ou=Group,dc=example,dc=com
        objectclass: organizationalUnit
        ou: Group

        dn: ou=People,dc=example,dc=com
        objectclass: organizationalUnit
        ou: People

        dn: uid=test1,ou=People,dc=example,dc=com
        objectclass: account
        uid: test1

        dn: cn=testgroup,ou=Group,dc=example,dc=com
        objectclass: groupOfNames
        cn: testgroup
        member: uid=test1,ou=People,dc=example,dc=com

Results in the following output from a search on the test1 user:

 # ldapsearch -LL -Y EXTERNAL -H ldapi:/// "(uid=test1)" -b dc=example,dc=com memberOf
 SASL/EXTERNAL authentication started
 SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
 SASL SSF: 0
 version: 1

 dn: uid=test1,ou=People,dc=example,dc=com
 memberOf: cn=testgroup,ou=Group,dc=example,dc=com

Note that the memberOf attribute is an operational attribute, so it must be requested explicitly.

12.8.3. Further Information

slapo-memberof(5)

12.9. The Proxy Cache Engine

LDAP servers typically hold one or more subtrees of a DIT. Replica (or shadow) servers hold shadow copies of entries held by one or more master servers. Changes are propagated from the master server to replica (slave) servers using LDAP Sync replication. An LDAP cache is a special type of replica which holds entries corresponding to search filters instead of subtrees.

12.9.1. Overview

The proxy cache extension of slapd is designed to improve the responsiveness of the ldap and meta backends. It handles a search request (query) by first determining whether it is contained in any cached search filter. Contained requests are answered from the proxy cache's local database. Other requests are passed on to the underlying ldap or meta backend and processed as usual.

E.g. (shoesize>=9) is contained in (shoesize>=8) and (sn=Richardson) is contained in (sn=Richards*)

Correct matching rules and syntaxes are used while comparing assertions for query containment. To simplify the query containment problem, a list of cacheable "templates" (defined below) is specified at configuration time. A query is cached or answered only if it belongs to one of these templates. The entries corresponding to cached queries are stored in the proxy cache local database while its associated meta information (filter, scope, base, attributes) is stored in main memory.

A template is a prototype for generating LDAP search requests. Templates are described by a prototype search filter and a list of attributes which are required in queries generated from the template. The representation for prototype filter is similar to RFC4515, except that the assertion values are missing. Examples of prototype filters are: (sn=),(&(sn=)(givenname=)) which are instantiated by search filters (sn=Doe) and (&(sn=Doe)(givenname=John)) respectively.

The cache replacement policy removes the least recently used (LRU) query and entries belonging to only that query. Queries are allowed a maximum time to live (TTL) in the cache thus providing weak consistency. A background task periodically checks the cache for expired queries and removes them.

The Proxy Cache paper (http://www.openldap.org/pub/kapurva/proxycaching.pdf) provides design and implementation details.

12.9.2. Proxy Cache Configuration

The cache configuration specific directives described below must appear after a overlay pcache directive within a "database meta" or "database ldap" section of the server's slapd.conf(5) file.

12.9.2.1. Setting cache parameters

 pcache <DB> <maxentries> <nattrsets> <entrylimit> <period>

This directive enables proxy caching and sets general cache parameters. The <DB> parameter specifies which underlying database is to be used to hold cached entries. It should be set to bdb or hdb. The <maxentries> parameter specifies the total number of entries which may be held in the cache. The <nattrsets> parameter specifies the total number of attribute sets (as specified by the pcacheAttrset directive) that may be defined. The <entrylimit> parameter specifies the maximum number of entries in a cacheable query. The <period> specifies the consistency check period (in seconds). In each period, queries with expired TTLs are removed.

12.9.2.2. Defining attribute sets

 pcacheAttrset <index> <attrs...>

Used to associate a set of attributes to an index. Each attribute set is associated with an index number from 0 to <numattrsets>-1. These indices are used by the pcacheTemplate directive to define cacheable templates.

12.9.2.3. Specifying cacheable templates

 pcacheTemplate <prototype_string> <attrset_index> <TTL>

Specifies a cacheable template and the "time to live" (in sec) <TTL> for queries belonging to the template. A template is described by its prototype filter string and set of required attributes identified by <attrset_index>.

12.9.2.4. Example for slapd.conf

An example slapd.conf(5) database section for a caching server which proxies for the "dc=example,dc=com" subtree held at server ldap.example.com.

        database        ldap
        suffix          "dc=example,dc=com"
        rootdn          "dc=example,dc=com"
        uri             ldap://ldap.example.com/
        overlay pcache
        pcache         hdb 100000 1 1000 100
        pcacheAttrset  0 mail postaladdress telephonenumber
        pcacheTemplate (sn=) 0 3600
        pcacheTemplate (&(sn=)(givenName=)) 0 3600
        pcacheTemplate (&(departmentNumber=)(secretary=*)) 0 3600

        cachesize 20
        directory ./testrun/db.2.a
        index       objectClass eq
        index       cn,sn,uid,mail  pres,eq,sub

12.9.2.5. Example for slapd-config

The same example as a LDIF file for back-config for a caching server which proxies for the "dc=example,dc=com" subtree held at server ldap.example.com.

   dn: olcDatabase={2}ldap,cn=config
   objectClass: olcDatabaseConfig
   objectClass: olcLDAPConfig
   olcDatabase: {2}ldap
   olcSuffix: dc=example,dc=com
   olcRootDN: dc=example,dc=com
   olcDbURI: "ldap://ldap.example.com"

   dn: olcOverlay={0}pcache,olcDatabase={2}ldap,cn=config
   objectClass: olcOverlayConfig
   objectClass: olcPcacheConfig
   olcOverlay: {0}pcache
   olcPcache: hdb 100000 1 1000 100
   olcPcacheAttrset: 0 mail postalAddress telephoneNumber
   olcPcacheTemplate: "(sn=)" 0 3600 0 0 0
   olcPcacheTemplate: "(&(sn=)(givenName=))" 0 3600 0 0 0
   olcPcacheTemplate: "(&(departmentNumber=)(secretary=))" 0 3600

   dn: olcDatabase={0}hdb,olcOverlay={0}pcache,olcDatabase={2}ldap,cn=config
   objectClass: olcHdbConfig
   objectClass: olcPcacheDatabase
   olcDatabase: {0}hdb
   olcDbDirectory: ./testrun/db.2.a
   olcDbCacheSize: 20
   olcDbIndex: objectClass eq
   olcDbIndex: cn,sn,uid,mail  pres,eq,sub
12.9.2.5.1. Cacheable Queries

A LDAP search query is cacheable when its filter matches one of the templates as defined in the "pcacheTemplate" statements and when it references only the attributes specified in the corresponding attribute set. In the example above the attribute set number 0 defines that only the attributes: mail postaladdress telephonenumber are cached for the following pcacheTemplates.

12.9.2.5.2. Examples:
        Filter: (&(sn=Richard*)(givenName=jack))
        Attrs: mail telephoneNumber

is cacheable, because it matches the template (&(sn=)(givenName=)) and its attributes are contained in pcacheAttrset 0.

        Filter: (&(sn=Richard*)(telephoneNumber))
        Attrs: givenName

is not cacheable, because the filter does not match the template, nor is the attribute givenName stored in the cache

        Filter: (|(sn=Richard*)(givenName=jack))
        Attrs: mail telephoneNumber

is not cacheable, because the filter does not match the template ( logical OR "|" condition instead of logical AND "&" )

12.9.3. Further Information

slapo-pcache(5)

12.10. Password Policies

12.10.1. Overview

This overlay follows the specifications contained in the draft RFC titled draft-behera-ldap-password-policy-09. While the draft itself is expired, it has been implemented in several directory servers, including slapd. Nonetheless, it is important to note that it is a draft, meaning that it is subject to change and is a work-in-progress.

The key abilities of the password policy overlay are as follows:

12.10.2. Password Policy Configuration

Instantiate the module in the database where it will be used, after adding the new ppolicy schema and loading the ppolicy module. The following example shows the ppolicy module being added to the database that handles the naming context "dc=example,dc=com". In this example we are also specifying the DN of a policy object to use if none other is specified in a user's object.

       database bdb
       suffix "dc=example,dc=com"
       [...additional database configuration directives go here...]

       overlay ppolicy
       ppolicy_default "cn=default,ou=policies,dc=example,dc=com"

Now we need a container for the policy objects. In our example the password policy objects are going to be placed in a section of the tree called "ou=policies,dc=example,dc=com":

       dn: ou=policies,dc=example,dc=com
       objectClass: organizationalUnit
       objectClass: top
       ou: policies

The default policy object that we are creating defines the following policies:

The actual policy would be:

       dn: cn=default,ou=policies,dc=example,dc=com
       cn: default
       objectClass: pwdPolicy
       objectClass: person
       objectClass: top
       pwdAllowUserChange: TRUE
       pwdAttribute: userPassword
       pwdCheckQuality: 2
       pwdExpireWarning: 600
       pwdFailureCountInterval: 30
       pwdGraceAuthNLimit: 5
       pwdInHistory: 5
       pwdLockout: TRUE
       pwdLockoutDuration: 0
       pwdMaxAge: 0
       pwdMaxFailure: 5
       pwdMinAge: 0
       pwdMinLength: 5
       pwdMustChange: FALSE
       pwdSafeModify: FALSE
       sn: dummy value

You can create additional policy objects as needed.

There are two ways password policy can be applied to individual objects:

1. The pwdPolicySubentry in a user's object - If a user's object has a pwdPolicySubEntry attribute specifying the DN of a policy object, then the policy defined by that object is applied.

2. Default password policy - If there is no specific pwdPolicySubentry set for an object, and the password policy module was configured with the DN of a default policy object and if that object exists, then the policy defined in that object is applied.

Please see slapo-ppolicy(5) for complete explanations of features and discussion of "Password Management Issues" at http://www.symas.com/blog/?page_id=66

12.10.3. Further Information

slapo-ppolicy(5)

12.11. Referential Integrity

12.11.1. Overview

This overlay can be used with a backend database such as slapd-bdb(5) to maintain the cohesiveness of a schema which utilizes reference attributes.

Whenever a modrdn or delete is performed, that is, when an entry's DN is renamed or an entry is removed, the server will search the directory for references to this DN (in selected attributes: see below) and update them accordingly. If it was a delete operation, the reference is deleted. If it was a modrdn operation, then the reference is updated with the new DN.

For example, a very common administration task is to maintain group membership lists, specially when users are removed from the directory. When an user account is deleted or renamed, all groups this user is a member of have to be updated. LDAP administrators usually have scripts for that. But we can use the refint overlay to automate this task. In this example, if the user is removed from the directory, the overlay will take care to remove the user from all the groups he/she was a member of. No more scripting for this.

12.11.2. Referential Integrity Configuration

The configuration for this overlay is as follows:

       overlay refint
       refint_attributes <attribute [attribute ...]>
       refint_nothing <string>

To illustrate this overlay, we will use the group membership scenario.

In slapd.conf:

       overlay refint
       refint_attributes member
       refint_nothing "cn=admin,dc=example,dc=com"

This configuration tells the overlay to maintain the referential integrity of the member attribute. This attribute is used in the groupOfNames object class which always needs a member, so we add the refint_nothing directive to fill in the group with a standard member should all the members vanish.

If we have the following group membership, the refint overlay will automatically remove john from the group if his entry is removed from the directory:

Figure X.Y: Maintaining referential integrity in groups

Notice that if we rename (modrdn) the john entry to, say, jsmith, the refint overlay will also rename the reference in the member attribute, so the group membership stays correct.

If we removed all users from the directory who are a member of this group, then the end result would be a single member in the group: cn=admin,dc=example,dc=com. This is the refint_nothing parameter kicking into action so that the schema is not violated.

The rootdn must be set for the database as refint runs as the rootdn to gain access to make its updates. The rootpw does not need to be set.

12.11.3. Further Information

slapo-refint(5)

12.12. Return Code

12.12.1. Overview

This overlay is useful to test the behavior of clients when server-generated erroneous and/or unusual responses occur, for example; error codes, referrals, excessive response times and so on.

This would be classed as a debugging tool whilst developing client software or additional Overlays.

For detailed information, please see the slapo-retcode(5) man page.

12.12.2. Return Code Configuration

The retcode overlay utilizes the "return code" schema described in the man page. This schema is specifically designed for use with this overlay and is not intended to be used otherwise.


Note: The necessary schema is loaded automatically by the overlay.

An example configuration might be:

       overlay         retcode
       retcode-parent  "ou=RetCodes,dc=example,dc=com"
       include         ./retcode.conf

       retcode-item    "cn=Unsolicited"                0x00 unsolicited="0"
       retcode-item    "cn=Notice of Disconnect"       0x00 unsolicited="1.3.6.1.4.1.1466.20036"
       retcode-item    "cn=Pre-disconnect"             0x34 flags="pre-disconnect"
       retcode-item    "cn=Post-disconnect"            0x34 flags="post-disconnect"


Note: retcode.conf can be found in the openldap source at: tests/data/retcode.conf

An excerpt of a retcode.conf would be something like:

       retcode-item    "cn=success"                            0x00

       retcode-item    "cn=success w/ delay"                   0x00    sleeptime=2

       retcode-item    "cn=operationsError"                    0x01
       retcode-item    "cn=protocolError"                      0x02
       retcode-item    "cn=timeLimitExceeded"                  0x03    op=search
       retcode-item    "cn=sizeLimitExceeded"                  0x04    op=search
       retcode-item    "cn=compareFalse"                       0x05    op=compare
       retcode-item    "cn=compareTrue"                        0x06    op=compare
       retcode-item    "cn=authMethodNotSupported"             0x07
       retcode-item    "cn=strongAuthNotSupported"             0x07    text="same as authMethodNotSupported"
       retcode-item    "cn=strongAuthRequired"                 0x08
       retcode-item    "cn=strongerAuthRequired"               0x08    text="same as strongAuthRequired"

Please see tests/data/retcode.conf for a complete retcode.conf

12.12.3. Further Information

slapo-retcode(5)

12.13. Rewrite/Remap

12.13.1. Overview

It performs basic DN/data rewrite and objectClass/attributeType mapping. Its usage is mostly intended to provide virtual views of existing data either remotely, in conjunction with the proxy backend described in slapd-ldap(5), or locally, in conjunction with the relay backend described in slapd-relay(5).

This overlay is extremely configurable and advanced, therefore recommended reading is the slapo-rwm(5) man page.

12.13.2. Rewrite/Remap Configuration

12.13.3. Further Information

slapo-rwm(5)

12.14. Sync Provider

12.14.1. Overview

This overlay implements the provider-side support for the LDAP Content Synchronization (RFC4533) as well as syncrepl replication support, including persistent search functionality.

12.14.2. Sync Provider Configuration

There is very little configuration needed for this overlay, in fact for many situations merely loading the overlay will suffice.

However, because the overlay creates a contextCSN attribute in the root entry of the database which is updated for every write operation performed against the database and only updated in memory, it is recommended to configure a checkpoint so that the contextCSN is written into the underlying database to minimize recovery time after an unclean shutdown:

       overlay syncprov
       syncprov-checkpoint 100 10

For every 100 operations or 10 minutes, which ever is sooner, the contextCSN will be checkpointed.

The four configuration directives available are syncprov-checkpoint, syncprov-sessionlog, syncprov-nopresent and syncprov-reloadhint which are covered in the man page discussing various other scenarios where this overlay can be used.

12.14.3. Further Information

The slapo-syncprov(5) man page and the Configuring the different replication types section

12.15. Translucent Proxy

12.15.1. Overview

This overlay can be used with a backend database such as slapd-bdb(5) to create a "translucent proxy".

Entries retrieved from a remote LDAP server may have some or all attributes overridden, or new attributes added, by entries in the local database before being presented to the client.

A search operation is first populated with entries from the remote LDAP server, the attributes of which are then overridden with any attributes defined in the local database. Local overrides may be populated with the add, modify, and modrdn operations, the use of which is restricted to the root user of the translucent local database.

A compare operation will perform a comparison with attributes defined in the local database record (if any) before any comparison is made with data in the remote database.

12.15.2. Translucent Proxy Configuration

There are various options available with this overlay, but for this example we will demonstrate adding new attributes to a remote entry and also searching against these newly added local attributes. For more information about overriding remote entries and search configuration, please see slapo-translucent(5)


Note: The Translucent Proxy overlay will disable schema checking in the local database, so that an entry consisting of overlay attributes need not adhere to the complete schema.

First we configure the overlay in the normal manner:

       include     /usr/local/etc/openldap/schema/core.schema
       include     /usr/local/etc/openldap/schema/cosine.schema
       include     /usr/local/etc/openldap/schema/nis.schema
       include     /usr/local/etc/openldap/schema/inetorgperson.schema

       pidfile     ./slapd.pid
       argsfile    ./slapd.args

       database    bdb
       suffix      "dc=suretecsystems,dc=com"
       rootdn      "cn=trans,dc=suretecsystems,dc=com"
       rootpw      secret
       directory   ./openldap-data

       index       objectClass eq

       overlay     translucent
       translucent_local carLicense

       uri         ldap://192.168.X.X:389
       lastmod     off
       acl-bind    binddn="cn=admin,dc=suretecsystems,dc=com" credentials="blahblah"

You will notice the overlay directive and a directive to say what attribute we want to be able to search against in the local database. We must also load the ldap backend which will connect to the remote directory server.

Now we take an example LDAP group:

       # itsupport, Groups, suretecsystems.com
       dn: cn=itsupport,ou=Groups,dc=suretecsystems,dc=com
       objectClass: posixGroup
       objectClass: sambaGroupMapping
       cn: itsupport
       gidNumber: 1000
       sambaSID: S-1-5-21-XXX
       sambaGroupType: 2
       displayName: itsupport
       memberUid: ghenry
       memberUid: joebloggs

and create an LDIF file we can use to add our data to the local database, using some pretty strange choices of new attributes for demonstration purposes:

       [ghenry@suretec test_configs]$ cat test-translucent-add.ldif
       dn: cn=itsupport,ou=Groups,dc=suretecsystems,dc=com
       businessCategory: frontend-override
       carLicense: LIVID
       employeeType: special
       departmentNumber: 9999999
       roomNumber: 41L-535

Searching against the proxy gives:

       [ghenry@suretec test_configs]$ ldapsearch -x -H ldap://127.0.0.1:9001 "(cn=itsupport)"
       # itsupport, Groups, OxObjects, suretecsystems.com
       dn: cn=itsupport,ou=Groups,ou=OxObjects,dc=suretecsystems,dc=com
       objectClass: posixGroup
       objectClass: sambaGroupMapping
       cn: itsupport
       gidNumber: 1003
       SAMBASID: S-1-5-21-XXX
       SAMBAGROUPTYPE: 2
       displayName: itsupport
       memberUid: ghenry
       memberUid: joebloggs
       roomNumber: 41L-535
       departmentNumber: 9999999
       employeeType: special
       carLicense: LIVID
       businessCategory: frontend-override

Here we can see that the 5 new attributes are added to the remote entry before being returned to the our client.

Because we have configured a local attribute to search against:

       overlay     translucent
       translucent_local carLicense

we can also search for that to return the completely fabricated entry:

       ldapsearch -x -H ldap://127.0.0.1:9001 (carLicense=LIVID)

This is an extremely feature because you can then extend a remote directory server locally and also search against the local entries.


Note: Because the translucent overlay does not perform any DN rewrites, the local and remote database instances must have the same suffix. Other configurations will probably fail with No Such Object and other errors

12.15.3. Further Information

slapo-translucent(5)

12.16. Attribute Uniqueness

12.16.1. Overview

This overlay can be used with a backend database such as slapd-bdb(5) to enforce the uniqueness of some or all attributes within a subtree.

12.16.2. Attribute Uniqueness Configuration

This overlay is only effective on new data from the point the overlay is enabled. To check uniqueness for existing data, you can export and import your data again via the LDAP Add operation, which will not be suitable for large amounts of data, unlike slapcat.

For the following example, if uniqueness were enforced for the mail attribute, the subtree would be searched for any other records which also have a mail attribute containing the same value presented with an add, modify or modrdn operation which are unique within the configured scope. If any are found, the request is rejected.


Note: If no attributes are specified, for example ldap:///??sub?, then the URI applies to all non-operational attributes. However, the keyword ignore can be specified to exclude certain non-operational attributes.

To search at the base dn of the current backend database ensuring uniqueness of the mail attribute, we simply add the following configuration:

       overlay unique
       unique_uri ldap:///?mail?sub?

For an existing entry of:

       dn: cn=gavin,dc=suretecsystems,dc=com
       objectClass: top
       objectClass: inetorgperson
       cn: gavin
       sn: henry
       mail: ghenry@suretecsystems.com

and we then try to add a new entry of:

       dn: cn=robert,dc=suretecsystems,dc=com
       objectClass: top
       objectClass: inetorgperson
       cn: robert
       sn: jones
       mail: ghenry@suretecsystems.com

would result in an error like so:

       adding new entry "cn=robert,dc=example,dc=com"
       ldap_add: Constraint violation (19)
               additional info: some attributes not unique

The overlay can have multiple URIs specified within a domain, allowing complex selections of objects and also have multiple unique_uri statements or olcUniqueURI attributes which will create independent domains.

For more information and details about the strict and ignore keywords, please see the slapo-unique(5) man page.

12.16.3. Further Information

slapo-unique(5)

12.17. Value Sorting

12.17.1. Overview

The Value Sorting overlay can be used with a backend database to sort the values of specific multi-valued attributes within a subtree. The sorting occurs whenever the attributes are returned in a search response.

12.17.2. Value Sorting Configuration

Sorting can be specified in ascending or descending order, using either numeric or alphanumeric sort methods. Additionally, a "weighted" sort can be specified, which uses a numeric weight prepended to the attribute values.

The weighted sort is always performed in ascending order, but may be combined with the other methods for values that all have equal weights. The weight is specified by prepending an integer weight {<weight>} in front of each value of the attribute for which weighted sorting is desired. This weighting factor is stripped off and never returned in search results.

Here are a few examples:

       loglevel    sync stats

       database    hdb
       suffix      "dc=suretecsystems,dc=com"
       directory   /usr/local/var/openldap-data

       ......

       overlay valsort
       valsort-attr memberUid ou=Groups,dc=suretecsystems,dc=com alpha-ascend

For example, ascend:

       # sharedemail, Groups, suretecsystems.com
       dn: cn=sharedemail,ou=Groups,dc=suretecsystems,dc=com
       objectClass: posixGroup
       objectClass: top
       cn: sharedemail
       gidNumber: 517
       memberUid: admin
       memberUid: dovecot
       memberUid: laura
       memberUid: suretec

For weighted, we change our data to:

       # sharedemail, Groups, suretecsystems.com
       dn: cn=sharedemail,ou=Groups,dc=suretecsystems,dc=com
       objectClass: posixGroup
       objectClass: top
       cn: sharedemail
       gidNumber: 517
       memberUid: {4}admin
       memberUid: {2}dovecot
       memberUid: {1}laura
       memberUid: {3}suretec

and change the config to:

       overlay valsort
       valsort-attr memberUid ou=Groups,dc=suretecsystems,dc=com weighted

Searching now results in:

       # sharedemail, Groups, OxObjects, suretecsystems.com
       dn: cn=sharedemail,ou=Groups,ou=OxObjects,dc=suretecsystems,dc=com
       objectClass: posixGroup
       objectClass: top
       cn: sharedemail
       gidNumber: 517
       memberUid: laura
       memberUid: dovecot
       memberUid: suretec
       memberUid: admin

12.17.3. Further Information

slapo-valsort(5)

12.18. Overlay Stacking

12.18.1. Overview

Overlays can be stacked, which means that more than one overlay can be instantiated for each database, or for the frontend. As a consequence, each overlays function is called, if defined, when overlay execution is invoked. Multiple overlays are executed in reverse order (as a stack) with respect to their definition in slapd.conf (5), or with respect to their ordering in the config database, as documented in slapd-config (5).

12.18.2. Example Scenarios

12.18.2.1. Samba


13. Schema Specification

This chapter describes how to extend the user schema used by slapd(8). The chapter assumes the reader is familiar with the LDAP/X.500 information model.

The first section, Distributed Schema Files details optional schema definitions provided in the distribution and where to obtain other definitions. The second section, Extending Schema, details how to define new schema items.

This chapter does not discuss how to extend system schema used by slapd(8) as this requires source code modification. System schema includes all operational attribute types or any object class which allows or requires an operational attribute (directly or indirectly).

13.1. Distributed Schema Files

OpenLDAP Software is distributed with a set of schema specifications for your use. Each set is defined in a file suitable for inclusion (using the include directive) in your slapd.conf(5) file. These schema files are normally installed in the /usr/local/etc/openldap/schema directory.

Table 8.1: Provided Schema Specifications
File Description
core.schema OpenLDAP core (required)
cosine.schema Cosine and Internet X.500 (useful)
inetorgperson.schema InetOrgPerson (useful)
misc.schema Assorted (experimental)
nis.schema Network Information Services (FYI)
openldap.schema OpenLDAP Project (experimental)

To use any of these schema files, you only need to include the desired file in the global definitions portion of your slapd.conf(5) file. For example:

        # include schema
        include /usr/local/etc/openldap/schema/core.schema
        include /usr/local/etc/openldap/schema/cosine.schema
        include /usr/local/etc/openldap/schema/inetorgperson.schema

Additional files may be available. Please consult the OpenLDAP FAQ (http://www.openldap.org/faq/).


Note: You should not modify any of the schema items defined in provided files.

13.2. Extending Schema

Schema used by slapd(8) may be extended to support additional syntaxes, matching rules, attribute types, and object classes. This chapter details how to add user application attribute types and object classes using the syntaxes and matching rules already supported by slapd. slapd can also be extended to support additional syntaxes, matching rules and system schema, but this requires some programming and hence is not discussed here.

There are five steps to defining new schema:

  1. obtain Object Identifier
  2. choose a name prefix
  3. create local schema file
  4. define custom attribute types (if necessary)
  5. define custom object classes

13.2.1. Object Identifiers

Each schema element is identified by a globally unique Object Identifier (OID). OIDs are also used to identify other objects. They are commonly found in protocols described by ASN.1. In particular, they are heavily used by the Simple Network Management Protocol (SNMP). As OIDs are hierarchical, your organization can obtain one OID and branch it as needed. For example, if your organization were assigned OID 1.1, you could branch the tree as follows:

Table 8.2: Example OID hierarchy
OID Assignment
1.1 Organization's OID
1.1.1 SNMP Elements
1.1.2 LDAP Elements
1.1.2.1 AttributeTypes
1.1.2.1.1 x-my-Attribute
1.1.2.2 ObjectClasses
1.1.2.2.1 x-my-ObjectClass

You are, of course, free to design a hierarchy suitable to your organizational needs under your organization's OID. No matter what hierarchy you choose, you should maintain a registry of assignments you make. This can be a simple flat file or something more sophisticated such as the OpenLDAP OID Registry (http://www.openldap.org/faq/index.cgi?file=197).

For more information about Object Identifiers (and a listing service) see http://www.alvestrand.no/objectid/.

To obtain a registered OID at no cost, apply for a OID under the Internet Assigned Numbers Authority (ORG:IANA) maintained Private Enterprise arc. Any private enterprise (organization) may request a Private Enterprise Number (PEN) to be assigned under this arc. Just fill out the IANA form at http://pen.iana.org/pen/PenApplication.page and your official PEN will be sent to you usually within a few days. Your base OID will be something like 1.3.6.1.4.1.X where X is an integer.


Note: PENs obtained using this form may be used for any purpose including identifying LDAP schema elements.

Alternatively, OID name space may be available from a national authority (e.g., ANSI, BSI).

13.2.2. Naming Elements

In addition to assigning a unique object identifier to each schema element, you should provide at least one textual name for each element. Names should be registered with the IANA or prefixed with "x-" to place in the "private use" name space.

The name should be both descriptive and not likely to clash with names of other schema elements. In particular, any name you choose should not clash with present or future Standard Track names (this is assured if you registered names or use names beginning with "x-").

It is noted that you can obtain your own registered name prefix so as to avoid having to register your names individually. See RFC4520 for details.

In the examples below, we have used a short prefix 'x-my-'. Such a short prefix would only be suitable for a very large, global organization. In general, we recommend something like 'x-de-Firm-' (German company) or 'x-com-Example' (elements associated with organization associated with example.com).

13.2.3. Local schema file

The objectclass and attributeTypes configuration file directives can be used to define schema rules on entries in the directory. It is customary to create a file to contain definitions of your custom schema items. We recommend you create a file local.schema in /usr/local/etc/openldap/schema/local.schema and then include this file in your slapd.conf(5) file immediately after other schema include directives.

        # include schema
        include /usr/local/etc/openldap/schema/core.schema
        include /usr/local/etc/openldap/schema/cosine.schema
        include /usr/local/etc/openldap/schema/inetorgperson.schema
        # include local schema
        include /usr/local/etc/openldap/schema/local.schema

13.2.4. Attribute Type Specification

The attributetype directive is used to define a new attribute type. The directive uses the same Attribute Type Description (as defined in RFC4512) used by the attributeTypes attribute found in the subschema subentry, e.g.:

        attributetype <RFC4512 Attribute Type Description>

where Attribute Type Description is defined by the following ABNF:

      AttributeTypeDescription = "(" whsp
            numericoid whsp              ; AttributeType identifier
          [ "NAME" qdescrs ]             ; name used in AttributeType
          [ "DESC" qdstring ]            ; description
          [ "OBSOLETE" whsp ]
          [ "SUP" woid ]                 ; derived from this other
                                         ; AttributeType
          [ "EQUALITY" woid              ; Matching Rule name
          [ "ORDERING" woid              ; Matching Rule name
          [ "SUBSTR" woid ]              ; Matching Rule name
          [ "SYNTAX" whsp noidlen whsp ] ; Syntax OID
          [ "SINGLE-VALUE" whsp ]        ; default multi-valued
          [ "COLLECTIVE" whsp ]          ; default not collective
          [ "NO-USER-MODIFICATION" whsp ]; default user modifiable
          [ "USAGE" whsp AttributeUsage ]; default userApplications
          whsp ")"

      AttributeUsage =
          "userApplications"     /
          "directoryOperation"   /
          "distributedOperation" / ; DSA-shared
          "dSAOperation"          ; DSA-specific, value depends on server

where whsp is a space (' '), numericoid is a globally unique OID in dotted-decimal form (e.g. 1.1.0), qdescrs is one or more names, woid is either the name or OID optionally followed by a length specifier (e.g {10}).

For example, the attribute types name and cn are defined in core.schema as:

        attributeType ( 2.5.4.41 NAME 'name'
                DESC 'name(s) associated with the object'
                EQUALITY caseIgnoreMatch
                SUBSTR caseIgnoreSubstringsMatch
                SYNTAX 1.3.6.1.4.1.1466.115.121.1.15{32768} )
        attributeType ( 2.5.4.3 NAME ( 'cn' 'commonName' )
                DESC 'common name(s) assciated with the object'
                SUP name )

Notice that each defines the attribute's OID, provides a short name, and a brief description. Each name is an alias for the OID. slapd(8) returns the first listed name when returning results.

The first attribute, name, holds values of directoryString (UTF-8 encoded Unicode) syntax. The syntax is specified by OID (1.3.6.1.4.1.1466.115.121.1.15 identifies the directoryString syntax). A length recommendation of 32768 is specified. Servers should support values of this length, but may support longer values. The field does NOT specify a size constraint, so is ignored on servers (such as slapd) which don't impose such size limits. In addition, the equality and substring matching uses case ignore rules. Below are tables listing commonly used syntax and matching rules (slapd(8) supports these and many more).

Table 8.3: Commonly Used Syntaxes
Name OID Description
boolean 1.3.6.1.4.1.1466.115.121.1.7 boolean value
directoryString 1.3.6.1.4.1.1466.115.121.1.15 Unicode (UTF-8) string
distinguishedName 1.3.6.1.4.1.1466.115.121.1.12 LDAP DN
integer 1.3.6.1.4.1.1466.115.121.1.27 integer
numericString 1.3.6.1.4.1.1466.115.121.1.36 numeric string
OID 1.3.6.1.4.1.1466.115.121.1.38 object identifier
octetString 1.3.6.1.4.1.1466.115.121.1.40 arbitrary octets

Table 8.4: Commonly Used Matching Rules
Name Type Description
booleanMatch equality boolean
caseIgnoreMatch equality case insensitive, space insensitive
caseIgnoreOrderingMatch ordering case insensitive, space insensitive
caseIgnoreSubstringsMatch substrings case insensitive, space insensitive
caseExactMatch equality case sensitive, space insensitive
caseExactOrderingMatch ordering case sensitive, space insensitive
caseExactSubstringsMatch substrings case sensitive, space insensitive
distinguishedNameMatch equality distinguished name
integerMatch equality integer
integerOrderingMatch ordering integer
numericStringMatch equality numerical
numericStringOrderingMatch ordering numerical
numericStringSubstringsMatch substrings numerical
octetStringMatch equality octet string
octetStringOrderingMatch ordering octet string
octetStringSubstringsMatch ordering octet st ring
objectIdentiferMatch equality object identifier

The second attribute, cn, is a subtype of name hence it inherits the syntax, matching rules, and usage of name. commonName is an alternative name.

Neither attribute is restricted to a single value. Both are meant for usage by user applications. Neither is obsolete nor collective.

The following subsections provide a couple of examples.

13.2.4.1. x-my-UniqueName

Many organizations maintain a single unique name for each user. Though one could use displayName (RFC2798), this attribute is really meant to be controlled by the user, not the organization. We could just copy the definition of displayName from inetorgperson.schema and replace the OID, name, and description, e.g:

        attributetype ( 1.1.2.1.1 NAME 'x-my-UniqueName'
                DESC 'unique name with my organization'
                EQUALITY caseIgnoreMatch
                SUBSTR caseIgnoreSubstringsMatch
                SYNTAX 1.3.6.1.4.1.1466.115.121.1.15
                SINGLE-VALUE )

However, if we want this name to be used in name assertions, e.g. (name=*Jane*), the attribute could alternatively be defined as a subtype of name, e.g.:

        attributetype ( 1.1.2.1.1 NAME 'x-my-UniqueName'
                DESC 'unique name with my organization'
                SUP name )

13.2.4.2. x-my-Photo

Many organizations maintain a photo of each each user. A x-my-Photo attribute type could be defined to hold a photo. Of course, one could use just use jpegPhoto (RFC2798) (or a subtype) to hold the photo. However, you can only do this if the photo is in JPEG File Interchange Format. Alternatively, an attribute type which uses the Octet String syntax can be defined, e.g.:

        attributetype ( 1.1.2.1.2 NAME 'x-my-Photo'
                DESC 'a photo (application defined format)'
                SYNTAX 1.3.6.1.4.1.1466.115.121.1.40
                SINGLE-VALUE )

In this case, the syntax doesn't specify the format of the photo. It's assumed (maybe incorrectly) that all applications accessing this attribute agree on the handling of values.

If you wanted to support multiple photo formats, you could define a separate attribute type for each format, prefix the photo with some typing information, or describe the value using ASN.1 and use the ;binary transfer option.

Another alternative is for the attribute to hold a URI pointing to the photo. You can model such an attribute after labeledURI (RFC2079) or simply create a subtype, e.g.:

        attributetype ( 1.1.2.1.3 NAME 'x-my-PhotoURI'
                DESC 'URI and optional label referring to a photo'
                SUP labeledURI )

13.2.5. Object Class Specification

The objectclasses directive is used to define a new object class. The directive uses the same Object Class Description (as defined in RFC4512) used by the objectClasses attribute found in the subschema subentry, e.g.:

        objectclass <RFC4512 Object Class Description>

where Object Class Description is defined by the following ABNF:

        ObjectClassDescription = "(" whsp
                numericoid whsp      ; ObjectClass identifier
                [ "NAME" qdescrs ]
                [ "DESC" qdstring ]
                [ "OBSOLETE" whsp ]
                [ "SUP" oids ]       ; Superior ObjectClasses
                [ ( "ABSTRACT" / "STRUCTURAL" / "AUXILIARY" ) whsp ]
                        ; default structural
                [ "MUST" oids ]      ; AttributeTypes
                [ "MAY" oids ]       ; AttributeTypes
                whsp ")"

where whsp is a space (' '), numericoid is a globally unique OID in dotted-decimal form (e.g. 1.1.0), qdescrs is one or more names, and oids is one or more names and/or OIDs.

13.2.5.1. x-my-PhotoObject

To define an auxiliary object class which allows x-my-Photo to be added to any existing entry.

        objectclass ( 1.1.2.2.1 NAME 'x-my-PhotoObject'
                DESC 'mixin x-my-Photo'
                AUXILIARY
                MAY x-my-Photo )

13.2.5.2. x-my-Person

If your organization would like have a private structural object class to instantiate users, you can subclass one of the existing person classes, such as inetOrgPerson (RFC2798), and add any additional attributes which you desire.

        objectclass ( 1.1.2.2.2 NAME 'x-my-Person'
                DESC 'my person'
                SUP inetOrgPerson
                MUST ( x-my-UniqueName $ givenName )
                MAY x-my-Photo )

The object class inherits the required/allowed attribute types of inetOrgPerson but requires x-my-UniqueName and givenName and allows x-my-Photo.

13.2.6. OID Macros

To ease the management and use of OIDs, slapd(8) supports Object Identifier macros. The objectIdentifier directive is used to equate a macro (name) with a OID. The OID may possibly be derived from a previously defined OID macro. The slapd.conf(5) syntax is:

        objectIdentifier <name> { <oid> | <name>[:<suffix>] }

The following demonstrates definition of a set of OID macros and their use in defining schema elements:

        objectIdentifier myOID  1.1
        objectIdentifier mySNMP myOID:1
        objectIdentifier myLDAP myOID:2
        objectIdentifier myAttributeType        myLDAP:1
        objectIdentifier myObjectClass  myLDAP:2
        attributetype ( myAttributeType:3 NAME 'x-my-PhotoURI'
                DESC 'URI and optional label referring to a photo'
                SUP labeledURI )
        objectclass ( myObjectClass:1 NAME 'x-my-PhotoObject'
                DESC 'mixin x-my-Photo'
                AUXILIARY
                MAY x-my-Photo )


14. Security Considerations

OpenLDAP Software is designed to run in a wide variety of computing environments from tightly-controlled closed networks to the global Internet. Hence, OpenLDAP Software supports many different security mechanisms. This chapter describes these mechanisms and discusses security considerations for using OpenLDAP Software.

14.1. Network Security

14.1.1. Selective Listening

By default, slapd(8) will listen on both the IPv4 and IPv6 "any" addresses. It is often desirable to have slapd listen on select address/port pairs. For example, listening only on the IPv4 address 127.0.0.1 will disallow remote access to the directory server. E.g.:

        slapd -h ldap://127.0.0.1

While the server can be configured to listen on a particular interface address, this doesn't necessarily restrict access to the server to only those networks accessible via that interface. To selective restrict remote access, it is recommend that an IP Firewall be used to restrict access.

See Command-line Options and slapd(8) for more information.

14.1.2. IP Firewall

IP firewall capabilities of the server system can be used to restrict access based upon the client's IP address and/or network interface used to communicate with the client.

Generally, slapd(8) listens on port 389/tcp for ldap:// sessions and port 636/tcp for ldaps://) sessions. slapd(8) may be configured to listen on other ports.

As specifics of how to configure IP firewall are dependent on the particular kind of IP firewall used, no examples are provided here. See the document associated with your IP firewall.

14.1.3. TCP Wrappers

slapd(8) supports TCP Wrappers. TCP Wrappers provide a rule-based access control system for controlling TCP/IP access to the server. For example, the host_options(5) rule:

        slapd: 10.0.0.0/255.0.0.0 127.0.0.1 : ALLOW
        slapd: ALL : DENY

allows only incoming connections from the private network 10.0.0.0 and localhost (127.0.0.1) to access the directory service.


Note: IP addresses are used as slapd(8) is not normally configured to perform reverse lookups.

It is noted that TCP wrappers require the connection to be accepted. As significant processing is required just to deny a connection, it is generally advised that IP firewall protection be used instead of TCP wrappers.

See hosts_access(5) for more information on TCP wrapper rules.

14.2. Data Integrity and Confidentiality Protection

Transport Layer Security (TLS) can be used to provide data integrity and confidentiality protection. OpenLDAP supports negotiation of TLS (SSL) via both StartTLS and ldaps://. See the Using TLS chapter for more information. StartTLS is the standard track mechanism.

A number of Simple Authentication and Security Layer (SASL) mechanisms, such as DIGEST-MD5 and GSSAPI, also provide data integrity and confidentiality protection. See the Using SASL chapter for more information.

14.2.1. Security Strength Factors

The server uses Security Strength Factors (SSF) to indicate the relative strength of protection. A SSF of zero (0) indicates no protections are in place. A SSF of one (1) indicates integrity protection are in place. A SSF greater than one (>1) roughly correlates to the effective encryption key length. For example, DES is 56, 3DES is 112, and AES 128, 192, or 256.

A number of administrative controls rely on SSFs associated with TLS and SASL protection in place on an LDAP session.

security controls disallow operations when appropriate protections are not in place. For example:

        security ssf=1 update_ssf=112

requires integrity protection for all operations and encryption protection, 3DES equivalent, for update operations (e.g. add, delete, modify, etc.). See slapd.conf(5) for details.

For fine-grained control, SSFs may be used in access controls. See the Access Control section for more information.

14.3. Authentication Methods

14.3.1. "simple" method

The LDAP "simple" method has three modes of operation:

Anonymous access is requested by providing no name and no password to the "simple" bind operation. Unauthenticated access is requested by providing a name but no password. Authenticated access is requested by providing a valid name and password.

An anonymous bind results in an anonymous authorization association. Anonymous bind mechanism is enabled by default, but can be disabled by specifying "disallow bind_anon" in slapd.conf(5).


Note: Disabling the anonymous bind mechanism does not prevent anonymous access to the directory. To require authentication to access the directory, one should instead specify "require authc".

An unauthenticated bind also results in an anonymous authorization association. Unauthenticated bind mechanism is disabled by default, but can be enabled by specifying "allow bind_anon_cred" in slapd.conf(5). As a number of LDAP applications mistakenly generate unauthenticated bind request when authenticated access was intended (that is, they do not ensure a password was provided), this mechanism should generally remain disabled.

A successful user/password authenticated bind results in a user authorization identity, the provided name, being associated with the session. User/password authenticated bind is enabled by default. However, as this mechanism itself offers no eavesdropping protection (e.g., the password is set in the clear), it is recommended that it be used only in tightly controlled systems or when the LDAP session is protected by other means (e.g., TLS, IPsec). Where the administrator relies on TLS to protect the password, it is recommended that unprotected authentication be disabled. This is done using the security directive's simple_bind option, which provides fine grain control over the level of confidential protection to require for simple user/password authentication. E.g., using security simple_bind=56 would require simple binds to use encryption of DES equivalent or better.

The user/password authenticated bind mechanism can be completely disabled by setting "disallow bind_simple".


Note: An unsuccessful bind always results in the session having an anonymous authorization association.

14.3.2. SASL method

The LDAP SASL method allows the use of any SASL authentication mechanism. The Using SASL section discusses the use of SASL.

14.4. Password Storage

LDAP passwords are normally stored in the userPassword attribute. RFC4519 specifies that passwords are not stored in encrypted (or hashed) form. This allows a wide range of password-based authentication mechanisms, such as DIGEST-MD5 to be used. This is also the most interoperable storage scheme.

However, it may be desirable to store a hash of password instead. slapd(8) supports a variety of storage schemes for the administrator to choose from.


Note: Values of password attributes, regardless of storage scheme used, should be protected as if they were clear text. Hashed passwords are subject to dictionary attacks and brute-force attacks.

The userPassword attribute is allowed to have more than one value, and it is possible for each value to be stored in a different form. During authentication, slapd will iterate through the values until it finds one that matches the offered password or until it runs out of values to inspect. The storage scheme is stored as a prefix on the value, so a hashed password using the Salted SHA1 (SSHA) scheme looks like:

 userPassword: {SSHA}DkMTwBl+a/3DQTxCYEApdUtNXGgdUac3

The advantage of hashed passwords is that an attacker which discovers the hash does not have direct access to the actual password. Unfortunately, as dictionary and brute force attacks are generally quite easy for attackers to successfully mount, this advantage is marginal at best (this is why all modern Unix systems use shadow password files).

The disadvantages of hashed storage is that they are non-standard, may cause interoperability problem, and generally preclude the use of stronger than Simple (or SASL/PLAIN) password-based authentication mechanisms such as DIGEST-MD5.

14.4.1. SSHA password storage scheme

This is the salted version of the SHA scheme. It is believed to be the most secure password storage scheme supported by slapd.

These values represent the same password:

 userPassword: {SSHA}DkMTwBl+a/3DQTxCYEApdUtNXGgdUac3
 userPassword: {SSHA}d0Q0626PSH9VUld7yWpR0k6BlpQmtczb

14.4.2. CRYPT password storage scheme

This scheme uses the operating system's crypt(3) hash function. It normally produces the traditional Unix-style 13 character hash, but on systems with glibc2 it can also generate the more secure 34-byte MD5 hash.

 userPassword: {CRYPT}aUihad99hmev6
 userPassword: {CRYPT}$1$czBJdDqS$TmkzUAb836oMxg/BmIwN.1

The advantage of the CRYPT scheme is that passwords can be transferred to or from an existing Unix password file without having to know the cleartext form. Both forms of crypt include salt so they have some resistance to dictionary attacks.


Note: Since this scheme uses the operating system's crypt(3) hash function, it is therefore operating system specific.

14.4.3. MD5 password storage scheme

This scheme simply takes the MD5 hash of the password and stores it in base64 encoded form:

 userPassword: {MD5}Xr4ilOzQ4PCOq3aQ0qbuaQ==

Although safer than cleartext storage, this is not a very secure scheme. The MD5 algorithm is fast, and because there is no salt the scheme is vulnerable to a dictionary attack.

14.4.4. SMD5 password storage scheme

This improves on the basic MD5 scheme by adding salt (random data which means that there are many possible representations of a given plaintext password). For example, both of these values represent the same password:

 userPassword: {SMD5}4QWGWZpj9GCmfuqEvm8HtZhZS6E=
 userPassword: {SMD5}g2/J/7D5EO6+oPdklp5p8YtNFk4=

14.4.5. SHA password storage scheme

Like the MD5 scheme, this simply feeds the password through an SHA hash process. SHA is thought to be more secure than MD5, but the lack of salt leaves the scheme exposed to dictionary attacks.

 userPassword: {SHA}5en6G6MezRroT3XKqkdPOmY/BfQ=

14.4.6. SASL password storage scheme

This is not really a password storage scheme at all. It uses the value of the userPassword attribute to delegate password verification to another process. See below for more information.


Note: This is not the same as using SASL to authenticate the LDAP session.

14.5. Pass-Through authentication

Since OpenLDAP 2.0 slapd has had the ability to delegate password verification to a separate process. This uses the sasl_checkpass(3) function so it can use any back-end server that Cyrus SASL supports for checking passwords. The choice is very wide, as one option is to use saslauthd(8) which in turn can use local files, Kerberos, an IMAP server, another LDAP server, or anything supported by the PAM mechanism.

The server must be built with the --enable-spasswd configuration option to enable pass-through authentication.


Note: This is not the same as using a SASL mechanism to authenticate the LDAP session.

Pass-Through authentication works only with plaintext passwords, as used in the "simple bind" and "SASL PLAIN" authentication mechanisms.}}

Pass-Through authentication is selective: it only affects users whose userPassword attribute has a value marked with the "{SASL}" scheme. The format of the attribute is:

 userPassword: {SASL}username@realm

The username and realm are passed to the SASL authentication mechanism and are used to identify the account whose password is to be verified. This allows arbitrary mapping between entries in OpenLDAP and accounts known to the backend authentication service.

It would be wise to use access control to prevent users from changing their passwords through LDAP where they have pass-through authentication enabled.

14.5.1. Configuring slapd to use an authentication provider

Where an entry has a "{SASL}" password value, OpenLDAP delegates the whole process of validating that entry's password to Cyrus SASL. All the configuration is therefore done in SASL config files.

The first file to be considered is confusingly named slapd.conf and is typically found in the SASL library directory, often /usr/lib/sasl2/slapd.conf This file governs the use of SASL when talking LDAP to slapd as well as the use of SASL backends for pass-through authentication. See options.html in the Cyrus SASL docs for full details. Here is a simple example for a server that will use saslauthd to verify passwords:

 mech_list: plain
 pwcheck_method: saslauthd
 saslauthd_path: /var/run/sasl2/mux

14.5.2. Configuring saslauthd

saslauthd is capable of using many different authentication services: see saslauthd(8) for details. A common requirement is to delegate some or all authentication to another LDAP server. Here is a sample saslauthd.conf that uses Microsoft Active Directory (AD):

 ldap_servers: ldap://dc1.example.com/ ldap://dc2.example.com/

 ldap_search_base: cn=Users,DC=ad,DC=example,DC=com
 ldap_filter: (userPrincipalName=%u)

 ldap_bind_dn: cn=saslauthd,cn=Users,DC=ad,DC=example,DC=com
 ldap_password: secret

In this case, saslauthd is run with the ldap authentication mechanism and is set to combine the SASL realm with the login name:

 saslauthd -a ldap -r

This means that the "username@realm" string from the userPassword attribute ends up being used to search AD for "userPrincipalName=username@realm" - the password is then verified by attempting to bind to AD using the entry found by the search and the password supplied by the LDAP client.

14.5.3. Testing pass-through authentication

It is usually best to start with the back-end authentication provider and work through saslauthd and slapd towards the LDAP client.

In the AD example above, first check that the DN and password that saslauthd will use when it connects to AD are valid:

 ldapsearch -x -H ldap://dc1.example.com/ \
      -D cn=saslauthd,cn=Users,DC=ad,DC=example,DC=com \
      -w secret \
      -b '' \
      -s base

Next check that a sample AD user can be found:

 ldapsearch -x -H ldap://dc1.example.com/ \
      -D cn=saslauthd,cn=Users,DC=ad,DC=example,DC=com \
      -w secret \
      -b cn=Users,DC=ad,DC=example,DC=com \
      "(userPrincipalName=user@ad.example.com)"

Check that the user can bind to AD:

 ldapsearch -x -H ldap://dc1.example.com/ \
      -D cn=user,cn=Users,DC=ad,DC=example,DC=com \
      -w userpassword \
      -b cn=user,cn=Users,DC=ad,DC=example,DC=com \
      -s base \
        "(objectclass=*)"

If all that works then saslauthd should be able to do the same:

 testsaslauthd -u user@ad.example.com -p userpassword
 testsaslauthd -u user@ad.example.com -p wrongpassword

Now put the magic token into an entry in OpenLDAP:

 userPassword: {SASL}user@ad.example.com

It should now be possible to bind to OpenLDAP using the DN of that entry and the password of the AD user.


15. Using SASL

OpenLDAP clients and servers are capable of authenticating via the Simple Authentication and Security Layer (SASL) framework, which is detailed in RFC4422. This chapter describes how to make use of SASL in OpenLDAP.

There are several industry standard authentication mechanisms that can be used with SASL, including GSSAPI for Kerberos V, DIGEST-MD5, and PLAIN and EXTERNAL for use with Transport Layer Security (TLS).

The standard client tools provided with OpenLDAP Software, such as ldapsearch(1) and ldapmodify(1), will by default attempt to authenticate the user to the LDAP directory server using SASL. Basic authentication service can be set up by the LDAP administrator with a few steps, allowing users to be authenticated to the slapd server as their LDAP entry. With a few extra steps, some users and services can be allowed to exploit SASL's proxy authorization feature, allowing them to authenticate themselves and then switch their identity to that of another user or service.

This chapter assumes you have read Cyrus SASL for System Administrators, provided with the Cyrus SASL package (in doc/sysadmin.html) and have a working Cyrus SASL installation. You should use the Cyrus SASL sample_client and sample_server to test your SASL installation before attempting to make use of it with OpenLDAP Software.

Note that in the following text the term user is used to describe a person or application entity who is connecting to the LDAP server via an LDAP client, such as ldapsearch(1). That is, the term user not only applies to both an individual using an LDAP client, but to an application entity which issues LDAP client operations without direct user control. For example, an e-mail server which uses LDAP operations to access information held in an LDAP server is an application entity.

15.1. SASL Security Considerations

SASL offers many different authentication mechanisms. This section briefly outlines security considerations.

Some mechanisms, such as PLAIN and LOGIN, offer no greater security over LDAP simple authentication. Like LDAP simple authentication, such mechanisms should not be used unless you have adequate security protections in place. It is recommended that these mechanisms be used only in conjunction with Transport Layer Security (TLS). Use of PLAIN and LOGIN are not discussed further in this document.

The DIGEST-MD5 mechanism is the mandatory-to-implement authentication mechanism for LDAPv3. Though DIGEST-MD5 is not a strong authentication mechanism in comparison with trusted third party authentication systems (such as Kerberos or public key systems), it does offer significant protections against a number of attacks. Unlike the CRAM-MD5 mechanism, it prevents chosen plaintext attacks. DIGEST-MD5 is favored over the use of plaintext password mechanisms. The CRAM-MD5 mechanism is deprecated in favor of DIGEST-MD5. Use of DIGEST-MD5 is discussed below.

The GSSAPI mechanism utilizes GSS-API Kerberos V to provide secure authentication services. The KERBEROS_V4 mechanism is available for those using Kerberos IV. Kerberos is viewed as a secure, distributed authentication system suitable for both small and large enterprises. Use of GSSAPI and KERBEROS_V4 are discussed below.

The EXTERNAL mechanism utilizes authentication services provided by lower level network services such as Transport Layer Security (TLS). When used in conjunction with TLS X.509-based public key technology, EXTERNAL offers strong authentication. TLS is discussed in the Using TLS chapter.

EXTERNAL can also be used with the ldapi:/// transport, as Unix-domain sockets can report the UID and GID of the client process.

There are other strong authentication mechanisms to choose from, including OTP (one time passwords) and SRP (secure remote passwords). These mechanisms are not discussed in this document.

15.2. SASL Authentication

Getting basic SASL authentication running involves a few steps. The first step configures your slapd server environment so that it can communicate with client programs using the security system in place at your site. This usually involves setting up a service key, a public key, or other form of secret. The second step concerns mapping authentication identities to LDAP DN's, which depends on how entries are laid out in your directory. An explanation of the first step will be given in the next section using Kerberos V4 as an example mechanism. The steps necessary for your site's authentication mechanism will be similar, but a guide to every mechanism available under SASL is beyond the scope of this chapter. The second step is described in the section Mapping Authentication Identities.

15.2.1. GSSAPI

This section describes the use of the SASL GSSAPI mechanism and Kerberos V with OpenLDAP. It will be assumed that you have Kerberos V deployed, you are familiar with the operation of the system, and that your users are trained in its use. This section also assumes you have familiarized yourself with the use of the GSSAPI mechanism by reading Configuring GSSAPI and Cyrus SASL (provided with Cyrus SASL in the doc/gssapi file) and successfully experimented with the Cyrus provided sample_server and sample_client applications. General information about Kerberos is available at http://web.mit.edu/kerberos/www/.

To use the GSSAPI mechanism with slapd(8) one must create a service key with a principal for ldap service within the realm for the host on which the service runs. For example, if you run slapd on directory.example.com and your realm is EXAMPLE.COM, you need to create a service key with the principal:

        ldap/directory.example.com@EXAMPLE.COM

When slapd(8) runs, it must have access to this key. This is generally done by placing the key into a keytab file, /etc/krb5.keytab. See your Kerberos and Cyrus SASL documentation for information regarding keytab location settings.

To use the GSSAPI mechanism to authenticate to the directory, the user obtains a Ticket Granting Ticket (TGT) prior to running the LDAP client. When using OpenLDAP client tools, the user may mandate use of the GSSAPI mechanism by specifying -Y GSSAPI as a command option.

For the purposes of authentication and authorization, slapd(8) associates an authentication request DN of the form:

        uid=<primary[/instance]>,cn=<realm>,cn=gssapi,cn=auth

Continuing our example, a user with the Kerberos principal kurt@EXAMPLE.COM would have the associated DN:

        uid=kurt,cn=example.com,cn=gssapi,cn=auth

and the principal ursula/admin@FOREIGN.REALM would have the associated DN:

        uid=ursula/admin,cn=foreign.realm,cn=gssapi,cn=auth

The authentication request DN can be used directly ACLs and groupOfNames "member" attributes, since it is of legitimate LDAP DN format. Or alternatively, the authentication DN could be mapped before use. See the section Mapping Authentication Identities for details.

15.2.2. KERBEROS_V4

This section describes the use of the SASL KERBEROS_V4 mechanism with OpenLDAP. It will be assumed that you are familiar with the workings of the Kerberos IV security system, and that your site has Kerberos IV deployed. Your users should be familiar with authentication policy, how to receive credentials in a Kerberos ticket cache, and how to refresh expired credentials.


Note: KERBEROS_V4 and Kerberos IV are deprecated in favor of GSSAPI and Kerberos V.

Client programs will need to be able to obtain a session key for use when connecting to your LDAP server. This allows the LDAP server to know the identity of the user, and allows the client to know it is connecting to a legitimate server. If encryption layers are to be used, the session key can also be used to help negotiate that option.

The slapd server runs the service called "ldap", and the server will require a srvtab file with a service key. SASL aware client programs will be obtaining an "ldap" service ticket with the user's ticket granting ticket (TGT), with the instance of the ticket matching the hostname of the OpenLDAP server. For example, if your realm is named EXAMPLE.COM and the slapd server is running on the host named directory.example.com, the /etc/srvtab file on the server will have a service key

        ldap.directory@EXAMPLE.COM

When an LDAP client is authenticating a user to the directory using the KERBEROS_IV mechanism, it will request a session key for that same principal, either from the ticket cache or by obtaining a new one from the Kerberos server. This will require the TGT to be available and valid in the cache as well. If it is not present or has expired, the client may print out the message:

        ldap_sasl_interactive_bind_s: Local error

When the service ticket is obtained, it will be passed to the LDAP server as proof of the user's identity. The server will extract the identity and realm out of the service ticket using SASL library calls, and convert them into an authentication request DN of the form

        uid=<username>,cn=<realm>,cn=<mechanism>,cn=auth

So in our above example, if the user's name were "adamson", the authentication request DN would be:

        uid=adamsom,cn=example.com,cn=kerberos_v4,cn=auth

This authentication request DN can be used directly ACLs or, alternatively, mapped prior to use. See the section Mapping Authentication Identities for details.

15.2.3. DIGEST-MD5

This section describes the use of the SASL DIGEST-MD5 mechanism using secrets stored either in the directory itself or in Cyrus SASL's own database. DIGEST-MD5 relies on the client and the server sharing a "secret", usually a password. The server generates a challenge and the client a response proving that it knows the shared secret. This is much more secure than simply sending the secret over the wire.

Cyrus SASL supports several shared-secret mechanisms. To do this, it needs access to the plaintext password (unlike mechanisms which pass plaintext passwords over the wire, where the server can store a hashed version of the password).

The server's copy of the shared-secret may be stored in Cyrus SASL's own sasldb database, in an external system accessed via saslauthd, or in LDAP database itself. In either case it is very important to apply file access controls and LDAP access controls to prevent exposure of the passwords. The configuration and commands discussed in this section assume the use of Cyrus SASL 2.1.

To use secrets stored in sasldb, simply add users with the saslpasswd2 command:

       saslpasswd2 -c <username>

The passwords for such users must be managed with the saslpasswd2 command.

To use secrets stored in the LDAP directory, place plaintext passwords in the userPassword attribute. It will be necessary to add an option to slapd.conf to make sure that passwords set using the LDAP Password Modify Operation are stored in plaintext:

       password-hash   {CLEARTEXT}

Passwords stored in this way can be managed either with ldappasswd(1) or by simply modifying the userPassword attribute. Regardless of where the passwords are stored, a mapping will be needed from authentication request DN to user's DN.

The DIGEST-MD5 mechanism produces authentication IDs of the form:

        uid=<username>,cn=<realm>,cn=digest-md5,cn=auth

If the default realm is used, the realm name is omitted from the ID, giving:

        uid=<username>,cn=digest-md5,cn=auth

See Mapping Authentication Identities below for information on optional mapping of identities.

With suitable mappings in place, users can specify SASL IDs when performing LDAP operations, and the password stored in sasldb or in the directory itself will be used to verify the authentication. For example, the user identified by the directory entry:

       dn: cn=Andrew Findlay+uid=u000997,dc=example,dc=com
       objectclass: inetOrgPerson
       objectclass: person
       sn: Findlay
       uid: u000997
       userPassword: secret

can issue commands of the form:

       ldapsearch -Y DIGEST-MD5 -U u000997 ...


Note: in each of the above cases, no authorization identity (e.g. -X) was provided. Unless you are attempting SASL Proxy Authorization, no authorization identity should be specified. The server will infer an authorization identity from authentication identity (as described below).

15.2.4. EXTERNAL

The SASL EXTERNAL mechanism makes use of an authentication performed by a lower-level protocol: usually TLS or Unix IPC

Each transport protocol returns Authentication Identities in its own format:

15.2.4.1. TLS Authentication Identity Format

This is the Subject DN from the client-side certificate. Note that DNs are displayed differently by LDAP and by X.509, so a certificate issued to

        C=gb, O=The Example Organisation, CN=A Person

will produce an authentication identity of:

        cn=A Person,o=The Example Organisation,c=gb

Note that you must set a suitable value for TLSVerifyClient to make the server request the use of a client-side certificate. Without this, the SASL EXTERNAL mechanism will not be offered. Refer to the Using TLS chapter for details.

15.2.4.2. IPC (ldapi:///) Identity Format

This is formed from the Unix UID and GID of the client process:

        gidNumber=<number>+uidNumber=<number>,cn=peercred,cn=external,cn=auth

Thus, a client process running as root will be:

        gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth

15.2.5. Mapping Authentication Identities

The authentication mechanism in the slapd server will use SASL library calls to obtain the authenticated user's "username", based on whatever underlying authentication mechanism was used. This username is in the namespace of the authentication mechanism, and not in the normal LDAP namespace. As stated in the sections above, that username is reformatted into an authentication request DN of the form

        uid=<username>,cn=<realm>,cn=<mechanism>,cn=auth

or

        uid=<username>,cn=<mechanism>,cn=auth

depending on whether or not <mechanism> employs the concept of "realms". Note also that the realm part will be omitted if the default realm was used in the authentication.

The ldapwhoami(1) command may be used to determine the identity associated with the user. It is very useful for determining proper function of mappings.

It is not intended that you should add LDAP entries of the above form to your LDAP database. Chances are you have an LDAP entry for each of the persons that will be authenticating to LDAP, laid out in your directory tree, and the tree does not start at cn=auth. But if your site has a clear mapping between the "username" and an LDAP entry for the person, you will be able to configure your LDAP server to automatically map a authentication request DN to the user's authentication DN.


Note: it is not required that the authentication request DN nor the user's authentication DN resulting from the mapping refer to an entry held in the directory. However, additional capabilities become available (see below).

The LDAP administrator will need to tell the slapd server how to map an authentication request DN to a user's authentication DN. This is done by adding one or more authz-regexp directives to the slapd.conf(5) file. This directive takes two arguments:

        authz-regexp   <search pattern>   <replacement pattern>

The authentication request DN is compared to the search pattern using the regular expression functions regcomp() and regexec(), and if it matches, it is rewritten as the replacement pattern. If there are multiple authz-regexp directives, only the first whose search pattern matches the authentication identity is used. The string that is output from the replacement pattern should be the authentication DN of the user or an LDAP URL. If replacement string produces a DN, the entry named by this DN need not be held by this server. If the replace string produces an LDAP URL, that LDAP URL must evaluate to one and only one entry held by this server.

The search pattern can contain any of the regular expression characters listed in regexec(3C). The main characters of note are dot ".", asterisk "*", and the open and close parenthesis "(" and ")". Essentially, the dot matches any character, the asterisk allows zero or more repeats of the immediately preceding character or pattern, and terms in parenthesis are remembered for the replacement pattern.

The replacement pattern will produce either a DN or URL referring to the user. Anything from the authentication request DN that matched a string in parenthesis in the search pattern is stored in the variable "$1". That variable "$1" can appear in the replacement pattern, and will be replaced by the string from the authentication request DN. If there were multiple sets of parentheses in the search pattern, the variables $2, $3, etc are used.

15.2.6. Direct Mapping

Where possible, direct mapping of the authentication request DN to the user's DN is generally recommended. Aside from avoiding the expense of searching for the user's DN, it allows mapping to DNs which refer to entries not held by this server.

Suppose the authentication request DN is written as:

        uid=adamson,cn=example.com,cn=gssapi,cn=auth

and the user's actual LDAP entry is:

        uid=adamson,ou=people,dc=example,dc=com

then the following authz-regexp directive in slapd.conf(5) would provide for direct mapping.

        authz-regexp
          uid=([^,]*),cn=example.com,cn=gssapi,cn=auth
          uid=$1,ou=people,dc=example,dc=com

An even more lenient rule could be written as

        authz-regexp
          uid=([^,]*),cn=[^,]*,cn=auth
          uid=$1,ou=people,dc=example,dc=com

Be careful about setting the search pattern too leniently, however, since it may mistakenly allow persons to become authenticated as a DN to which they should not have access. It is better to write several strict directives than one lenient directive which has security holes. If there is only one authentication mechanism in place at your site, and zero or one realms in use, you might be able to map between authentication identities and LDAP DN's with a single authz-regexp directive.

Don't forget to allow for the case where the realm is omitted as well as the case with an explicitly specified realm. This may well require a separate authz-regexp directive for each case, with the explicit-realm entry being listed first.

15.2.7. Search-based mappings

There are a number of cases where mapping to a LDAP URL may be appropriate. For instance, some sites may have person objects located in multiple areas of the LDAP tree, such as if there were an ou=accounting tree and an ou=engineering tree, with persons interspersed between them. Or, maybe the desired mapping must be based upon information in the user's information. Consider the need to map the above authentication request DN to user whose entry is as follows:

        dn: cn=Mark Adamson,ou=People,dc=Example,dc=COM
        objectclass: person
        cn: Mark Adamson
        uid: adamson

The information in the authentication request DN is insufficient to allow the user's DN to be directly derived, instead the user's DN must be searched for. For these situations, a replacement pattern which produces a LDAP URL can be used in the authz-regexp directives. This URL will then be used to perform an internal search of the LDAP database to find the person's authentication DN.

An LDAP URL, similar to other URL's, is of the form

        ldap://<host>/<base>?<attrs>?<scope>?<filter>

This contains all of the elements necessary to perform an LDAP search: the name of the server <host>, the LDAP DN search base <base>, the LDAP attributes to retrieve <attrs>, the search scope <scope> which is one of the three options "base", "one", or "sub", and lastly an LDAP search filter <filter>. Since the search is for an LDAP DN within the current server, the <host> portion should be empty. The <attrs> field is also ignored since only the DN is of concern. These two elements are left in the format of the URL to maintain the clarity of what information goes where in the string.

Suppose that the person in the example from above did in fact have an authentication username of "adamson" and that information was kept in the attribute "uid" in their LDAP entry. The authz-regexp directive might be written as

        authz-regexp
          uid=([^,]*),cn=example.com,cn=gssapi,cn=auth
          ldap:///ou=people,dc=example,dc=com??one?(uid=$1)

This will initiate an internal search of the LDAP database inside the slapd server. If the search returns exactly one entry, it is accepted as being the DN of the user. If there are more than one entries returned, or if there are zero entries returned, the authentication fails and the user's connection is left bound as the authentication request DN.

The attributes that are used in the search filter <filter> in the URL should be indexed to allow faster searching. If they are not, the authentication step alone can take uncomfortably long periods, and users may assume the server is down.

A more complex site might have several realms in use, each mapping to a different subtree in the directory. These can be handled with statements of the form:

        # Match Engineering realm
        authz-regexp
           uid=([^,]*),cn=engineering.example.com,cn=digest-md5,cn=auth
           ldap:///dc=eng,dc=example,dc=com??one?(&(uid=$1)(objectClass=person))

        # Match Accounting realm
        authz-regexp
           uid=([^,].*),cn=accounting.example.com,cn=digest-md5,cn=auth
           ldap:///dc=accounting,dc=example,dc=com??one?(&(uid=$1)(objectClass=person))

        # Default realm is customers.example.com
        authz-regexp
           uid=([^,]*),cn=digest-md5,cn=auth
           ldap:///dc=customers,dc=example,dc=com??one?(&(uid=$1)(objectClass=person))

Note that the explicitly-named realms are handled first, to avoid the realm name becoming part of the UID. Also note the use of scope and filters to limit matching to desirable entries.

Note as well that authz-regexp internal search are subject to access controls. Specifically, the authentication identity must have auth access.

See slapd.conf(5) for more detailed information.

15.3. SASL Proxy Authorization

The SASL offers a feature known as proxy authorization, which allows an authenticated user to request that they act on the behalf of another user. This step occurs after the user has obtained an authentication DN, and involves sending an authorization identity to the server. The server will then make a decision on whether or not to allow the authorization to occur. If it is allowed, the user's LDAP connection is switched to have a binding DN derived from the authorization identity, and the LDAP session proceeds with the access of the new authorization DN.

The decision to allow an authorization to proceed depends on the rules and policies of the site where LDAP is running, and thus cannot be made by SASL alone. The SASL library leaves it up to the server to make the decision. The LDAP administrator sets the guidelines of who can authorize to what identity by adding information into the LDAP database entries. By default, the authorization features are disabled, and must be explicitly configured by the LDAP administrator before use.

15.3.1. Uses of Proxy Authorization

This sort of service is useful when one entity needs to act on the behalf of many other users. For example, users may be directed to a web page to make changes to their personal information in their LDAP entry. The users authenticate to the web server to establish their identity, but the web server CGI cannot authenticate to the LDAP server as that user to make changes for them. Instead, the web server authenticates itself to the LDAP server as a service identity, say,

        cn=WebUpdate,dc=example,dc=com

and then it will SASL authorize to the DN of the user. Once so authorized, the CGI makes changes to the LDAP entry of the user, and as far as the slapd server can tell for its ACLs, it is the user themself on the other end of the connection. The user could have connected to the LDAP server directly and authenticated as themself, but that would require the user to have more knowledge of LDAP clients, knowledge which the web page provides in an easier format.

Proxy authorization can also be used to limit access to an account that has greater access to the database. Such an account, perhaps even the root DN specified in slapd.conf(5), can have a strict list of people who can authorize to that DN. Changes to the LDAP database could then be only allowed by that DN, and in order to become that DN, users must first authenticate as one of the persons on the list. This allows for better auditing of who made changes to the LDAP database. If people were allowed to authenticate directly to the privileged account, possibly through the rootpw slapd.conf(5) directive or through a userPassword attribute, then auditing becomes more difficult.

Note that after a successful proxy authorization, the original authentication DN of the LDAP connection is overwritten by the new DN from the authorization request. If a service program is able to authenticate itself as its own authentication DN and then authorize to other DN's, and it is planning on switching to several different identities during one LDAP session, it will need to authenticate itself each time before authorizing to another DN (or use a different proxy authorization mechanism). The slapd server does not keep record of the service program's ability to switch to other DN's. On authentication mechanisms like Kerberos this will not require multiple connections being made to the Kerberos server, since the user's TGT and "ldap" session key are valid for multiple uses for the several hours of the ticket lifetime.

15.3.2. SASL Authorization Identities

The SASL authorization identity is sent to the LDAP server via the -X switch for ldapsearch(1) and other tools, or in the *authzid parameter to the lutil_sasl_defaults() call. The identity can be in one of two forms, either

        u:<username>

or

        dn:<dn>

In the first form, the <username> is from the same namespace as the authentication identities above. It is the user's username as it is referred to by the underlying authentication mechanism. Authorization identities of this form are converted into a DN format by the same function that the authentication process used, producing an authorization request DN of the form

        uid=<username>,cn=<realm>,cn=<mechanism>,cn=auth

That authorization request DN is then run through the same authz-regexp process to convert it into a legitimate authorization DN from the database. If it cannot be converted due to a failed search from an LDAP URL, the authorization request fails with "inappropriate access". Otherwise, the DN string is now a legitimate authorization DN ready to undergo approval.

If the authorization identity was provided in the second form, with a "dn:" prefix, the string after the prefix is already in authorization DN form, ready to undergo approval.

15.3.3. Proxy Authorization Rules

Once slapd has the authorization DN, the actual approval process begins. There are two attributes that the LDAP administrator can put into LDAP entries to allow authorization:

        authzTo
        authzFrom

Both can be multivalued. The authzTo attribute is a source rule, and it is placed into the entry associated with the authentication DN to tell what authorization DNs the authenticated DN is allowed to assume. The second attribute is a destination rule, and it is placed into the entry associated with the requested authorization DN to tell which authenticated DNs may assume it.

The choice of which authorization policy attribute to use is up to the administrator. Source rules are checked first in the person's authentication DN entry, and if none of the authzTo rules specify the authorization is permitted, the authzFrom rules in the authorization DN entry are then checked. If neither case specifies that the request be honored, the request is denied. Since the default behavior is to deny authorization requests, rules only specify that a request be allowed; there are no negative rules telling what authorizations to deny.

The value(s) in the two attributes are of the same form as the output of the replacement pattern of a authz-regexp directive: either a DN or an LDAP URL. For example, if a authzTo value is a DN, that DN is one the authenticated user can authorize to. On the other hand, if the authzTo value is an LDAP URL, the URL is used as an internal search of the LDAP database, and the authenticated user can become ANY DN returned by the search. If an LDAP entry looked like:

        dn: cn=WebUpdate,dc=example,dc=com
        authzTo: ldap:///dc=example,dc=com??sub?(objectclass=person)

then any user who authenticated as cn=WebUpdate,dc=example,dc=com could authorize to any other LDAP entry under the search base dc=example,dc=com which has an objectClass of Person.

15.3.3.1. Notes on Proxy Authorization Rules

An LDAP URL in a authzTo or authzFrom attribute will return a set of DNs. Each DN returned will be checked. Searches which return a large set can cause the authorization process to take an uncomfortably long time. Also, searches should be performed on attributes that have been indexed by slapd.

To help produce more sweeping rules for authzFrom and authzTo, the values of these attributes are allowed to be DNs with regular expression characters in them. This means a source rule like

        authzTo: dn.regex:^uid=[^,]*,dc=example,dc=com$

would allow that authenticated user to authorize to any DN that matches the regular expression pattern given. This regular expression comparison can be evaluated much faster than an LDAP search for (uid=*).

Also note that the values in an authorization rule must be one of the two forms: an LDAP URL or a DN (with or without regular expression characters). Anything that does not begin with "ldap://" is taken as a DN. It is not permissible to enter another authorization identity of the form "u:<username>" as an authorization rule.

15.3.3.2. Policy Configuration

The decision of which type of rules to use, authzFrom or authzTo, will depend on the site's situation. For example, if the set of people who may become a given identity can easily be written as a search filter, then a single destination rule could be written. If the set of people is not easily defined by a search filter, and the set of people is small, it may be better to write a source rule in the entries of each of those people who should be allowed to perform the proxy authorization.

By default, processing of proxy authorization rules is disabled. The authz-policy directive must be set in the slapd.conf(5) file to enable authorization. This directive can be set to none for no rules (the default), to for source rules, from for destination rules, or both for both source and destination rules.

Source rules are extremely powerful. If ordinary users have access to write the authzTo attribute in their own entries, then they can write rules that would allow them to authorize as anyone else. As such, when using source rules, the authzTo attribute should be protected with an ACL that only allows privileged users to set its values.


16. Using TLS

OpenLDAP clients and servers are capable of using the Transport Layer Security (TLS) framework to provide integrity and confidentiality protections and to support LDAP authentication using the SASL EXTERNAL mechanism. TLS is defined in RFC4346.


Note: For generating certifcates, please reference http://www.openldap.org/faq/data/cache/185.html

16.1. TLS Certificates

TLS uses X.509 certificates to carry client and server identities. All servers are required to have valid certificates, whereas client certificates are optional. Clients must have a valid certificate in order to authenticate via SASL EXTERNAL. For more information on creating and managing certificates, see the OpenSSL, GnuTLS, or MozNSS documentation, depending on which TLS implementation libraries you are using.

16.1.1. Server Certificates

The DN of a server certificate must use the CN attribute to name the server, and the CN must carry the server's fully qualified domain name. Additional alias names and wildcards may be present in the subjectAltName certificate extension. More details on server certificate names are in RFC4513.

16.1.2. Client Certificates

The DN of a client certificate can be used directly as an authentication DN. Since X.509 is a part of the X.500 standard and LDAP is also based on X.500, both use the same DN formats and generally the DN in a user's X.509 certificate should be identical to the DN of their LDAP entry. However, sometimes the DNs may not be exactly the same, and so the mapping facility described in Mapping Authentication Identities can be applied to these DNs as well.

16.2. TLS Configuration

After obtaining the required certificates, a number of options must be configured on both the client and the server to enable TLS and make use of the certificates. At a minimum, the clients must be configured with the name of the file containing all of the Certificate Authority (CA) certificates it will trust. The server must be configured with the CA certificates and also its own server certificate and private key.

Typically a single CA will have issued the server certificate and all of the trusted client certificates, so the server only needs to trust that one signing CA. However, a client may wish to connect to a variety of secure servers managed by different organizations, with server certificates generated by many different CAs. As such, a client is likely to need a list of many different trusted CAs in its configuration.

16.2.1. Server Configuration

The configuration directives for slapd belong in the global directives section of slapd.conf(5).

16.2.1.1. TLSCACertificateFile <filename>

This directive specifies the PEM-format file containing certificates for the CA's that slapd will trust. The certificate for the CA that signed the server certificate must be included among these certificates. If the signing CA was not a top-level (root) CA, certificates for the entire sequence of CA's from the signing CA to the top-level CA should be present. Multiple certificates are simply appended to the file; the order is not significant.

16.2.1.2. TLSCACertificatePath <path>

This directive specifies the path of a directory that contains individual CA certificates in separate files. In addition, this directory must be specially managed using the OpenSSL c_rehash utility. When using this feature, the OpenSSL library will attempt to locate certificate files based on a hash of their name and serial number. The c_rehash utility is used to generate symbolic links with the hashed names that point to the actual certificate files. As such, this option can only be used with a filesystem that actually supports symbolic links. In general, it is simpler to use the TLSCACertificateFile directive instead.

When using Mozilla NSS, this directive can be used to specify the path of the directory containing the NSS certificate and key database files. The certutil command can be used to add a CA certificate:

        certutil -d <path> -A -n "name of CA cert" -t CT,, -a -i /path/to/cacertfile.pem

16.2.1.3. TLSCertificateFile <filename>

This directive specifies the file that contains the slapd server certificate. Certificates are generally public information and require no special protection.

When using Mozilla NSS, if using a cert/key database (specified with TLSCACertificatePath), this directive specifies the name of the certificate to use:

       TLSCertificateFile Server-Cert
       TLSCertificateFile my hardware device:Server-Cert
       certutil -d /path/to/certdbdir -L

16.2.1.4. TLSCertificateKeyFile <filename>

This directive specifies the file that contains the private key that matches the certificate stored in the TLSCertificateFile file. Private keys themselves are sensitive data and are usually password encrypted for protection. However, the current implementation doesn't support encrypted keys so the key must not be encrypted and the file itself must be protected carefully.

When using Mozilla NSS, this directive specifies the name of a file that contains the password for the key for the certificate specified with TLSCertificateFile. The modutil command can be used to turn off password protection for the cert/key database. For example, if TLSCACertificatePath specifes /etc/openldap/certdb as the location of the cert/key database, use modutil to change the password to the empty string:

        modutil -dbdir /etc/openldap/certdb -changepw 'NSS Certificate DB'

16.2.1.5. TLSCipherSuite <cipher-suite-spec>

This directive configures what ciphers will be accepted and the preference order. <cipher-suite-spec> should be a cipher specification for OpenSSL. You can use the command

        openssl ciphers -v ALL

to obtain a verbose list of available cipher specifications.

Besides the individual cipher names, the specifiers HIGH, MEDIUM, LOW, EXPORT, and EXPORT40 may be helpful, along with TLSv1, SSLv3, and SSLv2.

To obtain the list of ciphers in GnuTLS use:

        gnutls-cli -l

When using Mozilla NSS, the OpenSSL cipher suite specifications are used and translated into the format used internally by Mozilla NSS. There isn't an easy way to list the cipher suites from the command line. The authoritative list is in the source code for Mozilla NSS in the file sslinfo.c in the structure

       static const SSLCipherSuiteInfo suiteInfo[]

16.2.1.6. TLSRandFile <filename>

This directive specifies the file to obtain random bits from when /dev/urandom is not available. If the system provides /dev/urandom then this option is not needed, otherwise a source of random data must be configured. Some systems (e.g. Linux) provide /dev/urandom by default, while others (e.g. Solaris) require the installation of a patch to provide it, and others may not support it at all. In the latter case, EGD or PRNGD should be installed, and this directive should specify the name of the EGD/PRNGD socket. The environment variable RANDFILE can also be used to specify the filename. Also, in the absence of these options, the .rnd file in the slapd user's home directory may be used if it exists. To use the .rnd file, just create the file and copy a few hundred bytes of arbitrary data into the file. The file is only used to provide a seed for the pseudo-random number generator, and it doesn't need very much data to work.

This directive is ignored with GnuTLS and Mozilla NSS.

16.2.1.7. TLSEphemeralDHParamFile <filename>

This directive specifies the file that contains parameters for Diffie-Hellman ephemeral key exchange. This is required in order to use a DSA certificate on the server side (i.e. TLSCertificateKeyFile points to a DSA key). Multiple sets of parameters can be included in the file; all of them will be processed. Parameters can be generated using the following command

        openssl dhparam [-dsaparam] -out <filename> <numbits>

This directive is ignored with GnuTLS and Mozilla NSS.

16.2.1.8. TLSVerifyClient { never | allow | try | demand }

This directive specifies what checks to perform on client certificates in an incoming TLS session, if any. This option is set to never by default, in which case the server never asks the client for a certificate. With a setting of allow the server will ask for a client certificate; if none is provided the session proceeds normally. If a certificate is provided but the server is unable to verify it, the certificate is ignored and the session proceeds normally, as if no certificate had been provided. With a setting of try the certificate is requested, and if none is provided, the session proceeds normally. If a certificate is provided and it cannot be verified, the session is immediately terminated. With a setting of demand the certificate is requested and a valid certificate must be provided, otherwise the session is immediately terminated.


Note: The server must request a client certificate in order to use the SASL EXTERNAL authentication mechanism with a TLS session. As such, a non-default TLSVerifyClient setting must be configured before SASL EXTERNAL authentication may be attempted, and the SASL EXTERNAL mechanism will only be offered to the client if a valid client certificate was received.

16.2.2. Client Configuration

Most of the client configuration directives parallel the server directives. The names of the directives are different, and they go into ldap.conf(5) instead of slapd.conf(5), but their functionality is mostly the same. Also, while most of these options may be configured on a system-wide basis, they may all be overridden by individual users in their .ldaprc files.

The LDAP Start TLS operation is used in LDAP to initiate TLS negotiation. All OpenLDAP command line tools support a -Z and -ZZ flag to indicate whether a Start TLS operation is to be issued. The latter flag indicates that the tool is to cease processing if TLS cannot be started while the former allows the command to continue.

In LDAPv2 environments, TLS is normally started using the LDAP Secure URI scheme (ldaps://) instead of the normal LDAP URI scheme (ldap://). OpenLDAP command line tools allow either scheme to used with the -H flag and with the URI ldap.conf(5) option.

16.2.2.1. TLS_CACERT <filename>

This is equivalent to the server's TLSCACertificateFile option. As noted in the TLS Configuration section, a client typically may need to know about more CAs than a server, but otherwise the same considerations apply.

16.2.2.2. TLS_CACERTDIR <path>

This is equivalent to the server's TLSCACertificatePath option. The specified directory must be managed with the OpenSSL c_rehash utility as well. If using Mozilla NSS, <path> may contain a cert/key database.

16.2.2.3. TLS_CERT <filename>

This directive specifies the file that contains the client certificate. This is a user-only directive and can only be specified in a user's .ldaprc file.

When using Mozilla NSS, if using a cert/key database (specified with TLS_CACERTDIR), this directive specifies the name of the certificate to use:

       TLS_CERT Certificate for Sam Carter
       TLS_CERT my hardware device:Certificate for Sam Carter
       certutil -d /path/to/certdbdir -L

16.2.2.4. TLS_KEY <filename>

This directive specifies the file that contains the private key that matches the certificate stored in the TLS_CERT file. The same constraints mentioned for TLSCertificateKeyFile apply here. This is also a user-only directive.

16.2.2.5. TLS_RANDFILE <filename>

This directive is the same as the server's TLSRandFile option.

16.2.2.6. TLS_REQCERT { never | allow | try | demand }

This directive is equivalent to the server's TLSVerifyClient option. However, for clients the default value is demand and there generally is no good reason to change this setting.


17. Constructing a Distributed Directory Service

For many sites, running one or more slapd(8) that hold an entire subtree of data is sufficient. But often it is desirable to have one slapd refer to other directory services for a certain part of the tree (which may or may not be running slapd).

slapd supports subordinate and superior knowledge information. Subordinate knowledge information is held in referral objects (RFC3296).

17.1. Subordinate Knowledge Information

Subordinate knowledge information may be provided to delegate a subtree. Subordinate knowledge information is maintained in the directory as a special referral object at the delegate point. The referral object acts as a delegation point, gluing two services together. This mechanism allows for hierarchical directory services to be constructed.

A referral object has a structural object class of referral and has the same Distinguished Name as the delegated subtree. Generally, the referral object will also provide the auxiliary object class extensibleObject. This allows the entry to contain appropriate Relative Distinguished Name values. This is best demonstrated by example.

If the server a.example.net holds dc=example,dc=net and wished to delegate the subtree ou=subtree,dc=example,dc=net to another server b.example.net, the following named referral object would be added to a.example.net:

        dn: dc=subtree,dc=example,dc=net
        objectClass: referral
        objectClass: extensibleObject
        dc: subtree
        ref: ldap://b.example.net/dc=subtree,dc=example,dc=net

The server uses this information to generate referrals and search continuations to subordinate servers.

For those familiar with X.500, a named referral object is similar to an X.500 knowledge reference held in a subr DSE.

17.2. Superior Knowledge Information

Superior knowledge information may be specified using the referral directive. The value is a list of URIs referring to superior directory services. For servers without immediate superiors, such as for a.example.net in the example above, the server can be configured to use a directory service with global knowledge, such as the OpenLDAP Root Service (http://www.openldap.org/faq/index.cgi?file=393).

        referral        ldap://root.openldap.org/

However, as a.example.net is the immediate superior to b.example.net, b.example.net would be configured as follows:

        referral        ldap://a.example.net/

The server uses this information to generate referrals for operations acting upon entries not within or subordinate to any of the naming contexts held by the server.

For those familiar with X.500, this use of the ref attribute is similar to an X.500 knowledge reference held in a Supr DSE.

17.3. The ManageDsaIT Control

Adding, modifying, and deleting referral objects is generally done using ldapmodify(1) or similar tools which support the ManageDsaIT control. The ManageDsaIT control informs the server that you intend to manage the referral object as a regular entry. This keeps the server from sending a referral result for requests which interrogate or update referral objects.

The ManageDsaIT control should not be specified when managing regular entries.

The -M option of ldapmodify(1) (and other tools) enables ManageDsaIT. For example:

        ldapmodify -M -f referral.ldif -x -D "cn=Manager,dc=example,dc=net" -W

or with ldapsearch(1):

        ldapsearch -M -b "dc=example,dc=net" -x "(objectclass=referral)" '*' ref


Note: the ref attribute is operational and must be explicitly requested when desired in search results.


Note: the use of referrals to construct a Distributed Directory Service is extremely clumsy and not well supported by common clients. If an existing installation has already been built using referrals, the use of the chain overlay to hide the referrals will greatly improve the usability of the Directory system. A better approach would be to use explicitly defined local and proxy databases in subordinate configurations to provide a seamless view of the Distributed Directory.


Note: LDAP operations, even subtree searches, normally access only one database. That can be changed by gluing databases together with the subordinate/olcSubordinate keyword. Please see slapd.conf(5) and slapd-config(5).


18. Replication

Replicated directories are a fundamental requirement for delivering a resilient enterprise deployment.

OpenLDAP has various configuration options for creating a replicated directory. In previous releases, replication was discussed in terms of a master server and some number of slave servers. A master accepted directory updates from other clients, and a slave only accepted updates from a (single) master. The replication structure was rigidly defined and any particular database could only fulfill a single role, either master or slave.

As OpenLDAP now supports a wide variety of replication topologies, these terms have been deprecated in favor of provider and consumer: A provider replicates directory updates to consumers; consumers receive replication updates from providers. Unlike the rigidly defined master/slave relationships, provider/consumer roles are quite fluid: replication updates received in a consumer can be further propagated by that consumer to other servers, so a consumer can also act simultaneously as a provider. Also, a consumer need not be an actual LDAP server; it may be just an LDAP client.

The following sections will describe the replication technology and discuss the various replication options that are available.

18.1. Replication Technology

18.1.1. LDAP Sync Replication

The LDAP Sync Replication engine, syncrepl for short, is a consumer-side replication engine that enables the consumer LDAP server to maintain a shadow copy of a DIT fragment. A syncrepl engine resides at the consumer and executes as one of the slapd(8) threads. It creates and maintains a consumer replica by connecting to the replication provider to perform the initial DIT content load followed either by periodic content polling or by timely updates upon content changes.

Syncrepl uses the LDAP Content Synchronization protocol (or LDAP Sync for short) as the replica synchronization protocol. LDAP Sync provides a stateful replication which supports both pull-based and push-based synchronization and does not mandate the use of a history store. In pull-based replication the consumer periodically polls the provider for updates. In push-based replication the consumer listens for updates that are sent by the provider in realtime. Since the protocol does not require a history store, the provider does not need to maintain any log of updates it has received (Note that the syncrepl engine is extensible and additional replication protocols may be supported in the future.).

Syncrepl keeps track of the status of the replication content by maintaining and exchanging synchronization cookies. Because the syncrepl consumer and provider maintain their content status, the consumer can poll the provider content to perform incremental synchronization by asking for the entries required to make the consumer replica up-to-date with the provider content. Syncrepl also enables convenient management of replicas by maintaining replica status. The consumer replica can be constructed from a consumer-side or a provider-side backup at any synchronization status. Syncrepl can automatically resynchronize the consumer replica up-to-date with the current provider content.

Syncrepl supports both pull-based and push-based synchronization. In its basic refreshOnly synchronization mode, the provider uses pull-based synchronization where the consumer servers need not be tracked and no history information is maintained. The information required for the provider to process periodic polling requests is contained in the synchronization cookie of the request itself. To optimize the pull-based synchronization, syncrepl utilizes the present phase of the LDAP Sync protocol as well as its delete phase, instead of falling back on frequent full reloads. To further optimize the pull-based synchronization, the provider can maintain a per-scope session log as a history store. In its refreshAndPersist mode of synchronization, the provider uses a push-based synchronization. The provider keeps track of the consumer servers that have requested a persistent search and sends them necessary updates as the provider replication content gets modified.

With syncrepl, a consumer server can create a replica without changing the provider's configurations and without restarting the provider server, if the consumer server has appropriate access privileges for the DIT fragment to be replicated. The consumer server can stop the replication also without the need for provider-side changes and restart.

Syncrepl supports partial, sparse, and fractional replications. The shadow DIT fragment is defined by a general search criteria consisting of base, scope, filter, and attribute list. The replica content is also subject to the access privileges of the bind identity of the syncrepl replication connection.

18.1.1.1. The LDAP Content Synchronization Protocol

The LDAP Sync protocol allows a client to maintain a synchronized copy of a DIT fragment. The LDAP Sync operation is defined as a set of controls and other protocol elements which extend the LDAP search operation. This section introduces the LDAP Content Sync protocol only briefly. For more information, refer to RFC4533.

The LDAP Sync protocol supports both polling and listening for changes by defining two respective synchronization operations: refreshOnly and refreshAndPersist. Polling is implemented by the refreshOnly operation. The consumer polls the provider using an LDAP Search request with an LDAP Sync control attached. The consumer copy is synchronized to the provider copy at the time of polling using the information returned in the search. The provider finishes the search operation by returning SearchResultDone at the end of the search operation as in the normal search. Listening is implemented by the refreshAndPersist operation. As the name implies, it begins with a search, like refreshOnly. Instead of finishing the search after returning all entries currently matching the search criteria, the synchronization search remains persistent in the provider. Subsequent updates to the synchronization content in the provider cause additional entry updates to be sent to the consumer.

The refreshOnly operation and the refresh stage of the refreshAndPersist operation can be performed with a present phase or a delete phase.

In the present phase, the provider sends the consumer the entries updated within the search scope since the last synchronization. The provider sends all requested attributes, be they changed or not, of the updated entries. For each unchanged entry which remains in the scope, the provider sends a present message consisting only of the name of the entry and the synchronization control representing state present. The present message does not contain any attributes of the entry. After the consumer receives all update and present entries, it can reliably determine the new consumer copy by adding the entries added to the provider, by replacing the entries modified at the provider, and by deleting entries in the consumer copy which have not been updated nor specified as being present at the provider.

The transmission of the updated entries in the delete phase is the same as in the present phase. The provider sends all the requested attributes of the entries updated within the search scope since the last synchronization to the consumer. In the delete phase, however, the provider sends a delete message for each entry deleted from the search scope, instead of sending present messages. The delete message consists only of the name of the entry and the synchronization control representing state delete. The new consumer copy can be determined by adding, modifying, and removing entries according to the synchronization control attached to the SearchResultEntry message.

In the case that the LDAP Sync provider maintains a history store and can determine which entries are scoped out of the consumer copy since the last synchronization time, the provider can use the delete phase. If the provider does not maintain any history store, cannot determine the scoped-out entries from the history store, or the history store does not cover the outdated synchronization state of the consumer, the provider should use the present phase. The use of the present phase is much more efficient than a full content reload in terms of the synchronization traffic. To reduce the synchronization traffic further, the LDAP Sync protocol also provides several optimizations such as the transmission of the normalized entryUUIDs and the transmission of multiple entryUUIDs in a single syncIdSet message.

At the end of the refreshOnly synchronization, the provider sends a synchronization cookie to the consumer as a state indicator of the consumer copy after the synchronization is completed. The consumer will present the received cookie when it requests the next incremental synchronization to the provider.

When refreshAndPersist synchronization is used, the provider sends a synchronization cookie at the end of the refresh stage by sending a Sync Info message with refreshDone=TRUE. It also sends a synchronization cookie by attaching it to SearchResultEntry messages generated in the persist stage of the synchronization search. During the persist stage, the provider can also send a Sync Info message containing the synchronization cookie at any time the provider wants to update the consumer-side state indicator.

In the LDAP Sync protocol, entries are uniquely identified by the entryUUID attribute value. It can function as a reliable identifier of the entry. The DN of the entry, on the other hand, can be changed over time and hence cannot be considered as the reliable identifier. The entryUUID is attached to each SearchResultEntry or SearchResultReference as a part of the synchronization control.

18.1.1.2. Syncrepl Details

The syncrepl engine utilizes both the refreshOnly and the refreshAndPersist operations of the LDAP Sync protocol. If a syncrepl specification is included in a database definition, slapd(8) launches a syncrepl engine as a slapd(8) thread and schedules its execution. If the refreshOnly operation is specified, the syncrepl engine will be rescheduled at the interval time after a synchronization operation is completed. If the refreshAndPersist operation is specified, the engine will remain active and process the persistent synchronization messages from the provider.

The syncrepl engine utilizes both the present phase and the delete phase of the refresh synchronization. It is possible to configure a session log in the provider which stores the entryUUIDs of a finite number of entries deleted from a database. Multiple replicas share the same session log. The syncrepl engine uses the delete phase if the session log is present and the state of the consumer server is recent enough that no session log entries are truncated after the last synchronization of the client. The syncrepl engine uses the present phase if no session log is configured for the replication content or if the consumer replica is too outdated to be covered by the session log. The current design of the session log store is memory based, so the information contained in the session log is not persistent over multiple provider invocations. It is not currently supported to access the session log store by using LDAP operations. It is also not currently supported to impose access control to the session log.

As a further optimization, even in the case the synchronization search is not associated with any session log, no entries will be transmitted to the consumer server when there has been no update in the replication context.

The syncrepl engine, which is a consumer-side replication engine, can work with any backends. The LDAP Sync provider can be configured as an overlay on any backend, but works best with the back-bdb or back-hdb backend.

The LDAP Sync provider maintains a contextCSN for each database as the current synchronization state indicator of the provider content. It is the largest entryCSN in the provider context such that no transactions for an entry having smaller entryCSN value remains outstanding. The contextCSN could not just be set to the largest issued entryCSN because entryCSN is obtained before a transaction starts and transactions are not committed in the issue order.

The provider stores the contextCSN of a context in the contextCSN attribute of the context suffix entry. The attribute is not written to the database after every update operation though; instead it is maintained primarily in memory. At database start time the provider reads the last saved contextCSN into memory and uses the in-memory copy exclusively thereafter. By default, changes to the contextCSN as a result of database updates will not be written to the database until the server is cleanly shut down. A checkpoint facility exists to cause the contextCSN to be written out more frequently if desired.

Note that at startup time, if the provider is unable to read a contextCSN from the suffix entry, it will scan the entire database to determine the value, and this scan may take quite a long time on a large database. When a contextCSN value is read, the database will still be scanned for any entryCSN values greater than it, to make sure the contextCSN value truly reflects the greatest committed entryCSN in the database. On databases which support inequality indexing, setting an eq index on the entryCSN attribute and configuring contextCSN checkpoints will greatly speed up this scanning step.

If no contextCSN can be determined by reading and scanning the database, a new value will be generated. Also, if scanning the database yielded a greater entryCSN than was previously recorded in the suffix entry's contextCSN attribute, a checkpoint will be immediately written with the new value.

The consumer also stores its replica state, which is the provider's contextCSN received as a synchronization cookie, in the contextCSN attribute of the suffix entry. The replica state maintained by a consumer server is used as the synchronization state indicator when it performs subsequent incremental synchronization with the provider server. It is also used as a provider-side synchronization state indicator when it functions as a secondary provider server in a cascading replication configuration. Since the consumer and provider state information are maintained in the same location within their respective databases, any consumer can be promoted to a provider (and vice versa) without any special actions.

Because a general search filter can be used in the syncrepl specification, some entries in the context may be omitted from the synchronization content. The syncrepl engine creates a glue entry to fill in the holes in the replica context if any part of the replica content is subordinate to the holes. The glue entries will not be returned in the search result unless ManageDsaIT control is provided.

Also as a consequence of the search filter used in the syncrepl specification, it is possible for a modification to remove an entry from the replication scope even though the entry has not been deleted on the provider. Logically the entry must be deleted on the consumer but in refreshOnly mode the provider cannot detect and propagate this change without the use of the session log on the provider.

For configuration, please see the Syncrepl section.

18.2. Deployment Alternatives

While the LDAP Sync specification only defines a narrow scope for replication, the OpenLDAP implementation is extremely flexible and supports a variety of operating modes to handle other scenarios not explicitly addressed in the spec.

18.2.1. Delta-syncrepl replication

LDAP Sync replication is an object-based replication mechanism. When any attribute value in a replicated object is changed on the provider, each consumer fetches and processes the complete changed object, including both the changed and unchanged attribute values during replication. One advantage of this approach is that when multiple changes occur to a single object, the precise sequence of those changes need not be preserved; only the final state of the entry is significant. But this approach may have drawbacks when the usage pattern involves single changes to multiple objects.

For example, suppose you have a database consisting of 102,400 objects of 1 KB each. Further, suppose you routinely run a batch job to change the value of a single two-byte attribute value that appears in each of the 102,400 objects on the master. Not counting LDAP and TCP/IP protocol overhead, each time you run this job each consumer will transfer and process 100 MB of data to process 200KB of changes!

99.98% of the data that is transmitted and processed in a case like this will be redundant, since it represents values that did not change. This is a waste of valuable transmission and processing bandwidth and can cause an unacceptable replication backlog to develop. While this situation is extreme, it serves to demonstrate a very real problem that is encountered in some LDAP deployments.

Delta-syncrepl, a changelog-based variant of syncrepl, is designed to address situations like the one described above. Delta-syncrepl works by maintaining a changelog of a selectable depth in a separate database on the provider. The replication consumer checks the changelog for the changes it needs and, as long as the changelog contains the needed changes, the consumer fetches the changes from the changelog and applies them to its database. If, however, a replica is too far out of sync (or completely empty), conventional syncrepl is used to bring it up to date and replication then switches back to the delta-syncrepl mode.


Note: since the database state is stored in both the changelog DB and the main DB on the provider, it is important to backup/restore both the changelog DB and the main DB using slapcat/slapadd when restoring a DB or copying it to another machine.

For configuration, please see the Delta-syncrepl section.

18.2.2. N-Way Multi-Master replication

Multi-Master replication is a replication technique using Syncrepl to replicate data to multiple provider ("Master") Directory servers.

18.2.2.1. Valid Arguments for Multi-Master replication

18.2.2.2. Invalid Arguments for Multi-Master replication

(These are often claimed to be advantages of Multi-Master replication but those claims are false):

18.2.2.3. Arguments against Multi-Master replication

For configuration, please see the N-Way Multi-Master section below

18.2.3. MirrorMode replication

MirrorMode is a hybrid configuration that provides all of the consistency guarantees of single-master replication, while also providing the high availability of multi-master. In MirrorMode two providers are set up to replicate from each other (as a multi-master configuration), but an external frontend is employed to direct all writes to only one of the two servers. The second provider will only be used for writes if the first provider crashes, at which point the frontend will switch to directing all writes to the second provider. When a crashed provider is repaired and restarted it will automatically catch up to any changes on the running provider and resync.

18.2.3.1. Arguments for MirrorMode

18.2.3.2. Arguments against MirrorMode

For configuration, please see the MirrorMode section below

18.2.4. Syncrepl Proxy Mode

While the LDAP Sync protocol supports both pull- and push-based replication, the push mode (refreshAndPersist) must still be initiated from the consumer before the provider can begin pushing changes. In some network configurations, particularly where firewalls restrict the direction in which connections can be made, a provider-initiated push mode may be needed.

This mode can be configured with the aid of the LDAP Backend (Backends and slapd-ldap(8)). Instead of running the syncrepl engine on the actual consumer, a slapd-ldap proxy is set up near (or collocated with) the provider that points to the consumer, and the syncrepl engine runs on the proxy.

For configuration, please see the Syncrepl Proxy section.

18.2.4.1. Replacing Slurpd

The old slurpd mechanism only operated in provider-initiated push mode. Slurpd replication was deprecated in favor of Syncrepl replication and has been completely removed from OpenLDAP 2.4.

The slurpd daemon was the original replication mechanism inherited from UMich's LDAP and operated in push mode: the master pushed changes to the slaves. It was replaced for many reasons, in brief:

Syncrepl has none of those weaknesses:

18.3. Configuring the different replication types

18.3.1. Syncrepl

18.3.1.1. Syncrepl configuration

Because syncrepl is a consumer-side replication engine, the syncrepl specification is defined in slapd.conf(5) of the consumer server, not in the provider server's configuration file. The initial loading of the replica content can be performed either by starting the syncrepl engine with no synchronization cookie or by populating the consumer replica by loading an LDIF file dumped as a backup at the provider.

When loading from a backup, it is not required to perform the initial loading from the up-to-date backup of the provider content. The syncrepl engine will automatically synchronize the initial consumer replica to the current provider content. As a result, it is not required to stop the provider server in order to avoid the replica inconsistency caused by the updates to the provider content during the content backup and loading process.

When replicating a large scale directory, especially in a bandwidth constrained environment, it is advised to load the consumer replica from a backup instead of performing a full initial load using syncrepl.

18.3.1.2. Set up the provider slapd

The provider is implemented as an overlay, so the overlay itself must first be configured in slapd.conf(5) before it can be used. The provider has only two configuration directives, for setting checkpoints on the contextCSN and for configuring the session log. Because the LDAP Sync search is subject to access control, proper access control privileges should be set up for the replicated content.

The contextCSN checkpoint is configured by the

        syncprov-checkpoint <ops> <minutes>

directive. Checkpoints are only tested after successful write operations. If <ops> operations or more than <minutes> time has passed since the last checkpoint, a new checkpoint is performed.

The session log is configured by the

        syncprov-sessionlog <size>

directive, where <size> is the maximum number of session log entries the session log can record. When a session log is configured, it is automatically used for all LDAP Sync searches within the database.

Note that using the session log requires searching on the entryUUID attribute. Setting an eq index on this attribute will greatly benefit the performance of the session log on the provider.

A more complete example of the slapd.conf(5) content is thus:

        database bdb
        suffix dc=Example,dc=com
        rootdn dc=Example,dc=com
        directory /var/ldap/db
        index objectclass,entryCSN,entryUUID eq

        overlay syncprov
        syncprov-checkpoint 100 10
        syncprov-sessionlog 100

18.3.1.3. Set up the consumer slapd

The syncrepl replication is specified in the database section of slapd.conf(5) for the replica context. The syncrepl engine is backend independent and the directive can be defined with any database type.

        database hdb
        suffix dc=Example,dc=com
        rootdn dc=Example,dc=com
        directory /var/ldap/db
        index objectclass,entryCSN,entryUUID eq

        syncrepl rid=123
                provider=ldap://provider.example.com:389
                type=refreshOnly
                interval=01:00:00:00
                searchbase="dc=example,dc=com"
                filter="(objectClass=organizationalPerson)"
                scope=sub
                attrs="cn,sn,ou,telephoneNumber,title,l"
                schemachecking=off
                bindmethod=simple
                binddn="cn=syncuser,dc=example,dc=com"
                credentials=secret

In this example, the consumer will connect to the provider slapd(8) at port 389 of ldap://provider.example.com to perform a polling (refreshOnly) mode of synchronization once a day. It will bind as cn=syncuser,dc=example,dc=com using simple authentication with password "secret". Note that the access control privilege of cn=syncuser,dc=example,dc=com should be set appropriately in the provider to retrieve the desired replication content. Also the search limits must be high enough on the provider to allow the syncuser to retrieve a complete copy of the requested content. The consumer uses the rootdn to write to its database so it always has full permissions to write all content.

The synchronization search in the above example will search for the entries whose objectClass is organizationalPerson in the entire subtree rooted at dc=example,dc=com. The requested attributes are cn, sn, ou, telephoneNumber, title, and l. The schema checking is turned off, so that the consumer slapd(8) will not enforce entry schema checking when it processes updates from the provider slapd(8).

For more detailed information on the syncrepl directive, see the syncrepl section of The slapd Configuration File chapter of this admin guide.

18.3.1.4. Start the provider and the consumer slapd

The provider slapd(8) is not required to be restarted. contextCSN is automatically generated as needed: it might be originally contained in the LDIF file, generated by slapadd (8), generated upon changes in the context, or generated when the first LDAP Sync search arrives at the provider. If an LDIF file is being loaded which did not previously contain the contextCSN, the -w option should be used with slapadd (8) to cause it to be generated. This will allow the server to startup a little quicker the first time it runs.

When starting a consumer slapd(8), it is possible to provide a synchronization cookie as the -c cookie command line option in order to start the synchronization from a specific state. The cookie is a comma separated list of name=value pairs. Currently supported syncrepl cookie fields are csn=<csn> and rid=<rid>. <csn> represents the current synchronization state of the consumer replica. <rid> identifies a consumer replica locally within the consumer server. It is used to relate the cookie to the syncrepl definition in slapd.conf(5) which has the matching replica identifier. The <rid> must have no more than 3 decimal digits. The command line cookie overrides the synchronization cookie stored in the consumer replica database.

18.3.2. Delta-syncrepl

18.3.2.1. Delta-syncrepl Provider configuration

Setting up delta-syncrepl requires configuration changes on both the master and replica servers:

     # Give the replica DN unlimited read access.  This ACL needs to be
     # merged with other ACL statements, and/or moved within the scope
     # of a database.  The "by * break" portion causes evaluation of
     # subsequent rules.  See slapd.access(5) for details.
     access to *
        by dn.base="cn=replicator,dc=symas,dc=com" read
        by * break

     # Set the module path location
     modulepath /opt/symas/lib/openldap

     # Load the hdb backend
     moduleload back_hdb.la

     # Load the accesslog overlay
     moduleload accesslog.la

     #Load the syncprov overlay
     moduleload syncprov.la

     # Accesslog database definitions
     database hdb
     suffix cn=accesslog
     directory /db/accesslog
     rootdn cn=accesslog
     index default eq
     index entryCSN,objectClass,reqEnd,reqResult,reqStart

     overlay syncprov
     syncprov-nopresent TRUE
     syncprov-reloadhint TRUE

     # Let the replica DN have limitless searches
     limits dn.exact="cn=replicator,dc=symas,dc=com" time.soft=unlimited time.hard=unlimited size.soft=unlimited size.hard=unlimited

     # Primary database definitions
     database hdb
     suffix "dc=symas,dc=com"
     rootdn "cn=manager,dc=symas,dc=com"

     ## Whatever other configuration options are desired

     # syncprov specific indexing
     index entryCSN eq
     index entryUUID eq

     # syncrepl Provider for primary db
     overlay syncprov
     syncprov-checkpoint 1000 60

     # accesslog overlay definitions for primary db
     overlay accesslog
     logdb cn=accesslog
     logops writes
     logsuccess TRUE
     # scan the accesslog DB every day, and purge entries older than 7 days
     logpurge 07+00:00 01+00:00

     # Let the replica DN have limitless searches
     limits dn.exact="cn=replicator,dc=symas,dc=com" time.soft=unlimited time.hard=unlimited size.soft=unlimited size.hard=unlimited

For more information, always consult the relevant man pages (slapo-accesslog(5) and slapd.conf(5))

18.3.2.2. Delta-syncrepl Consumer configuration

     # Replica database configuration
     database hdb
     suffix "dc=symas,dc=com"
     rootdn "cn=manager,dc=symas,dc=com"

     ## Whatever other configuration bits for the replica, like indexing
     ## that you want

     # syncrepl specific indices
     index entryUUID eq

     # syncrepl directives
     syncrepl  rid=0
               provider=ldap://ldapmaster.symas.com:389
               bindmethod=simple
               binddn="cn=replicator,dc=symas,dc=com"
               credentials=secret
               searchbase="dc=symas,dc=com"
               logbase="cn=accesslog"
               logfilter="(&(objectClass=auditWriteObject)(reqResult=0))"
               schemachecking=on
               type=refreshAndPersist
               retry="60 +"
               syncdata=accesslog

     # Refer updates to the master
     updateref               ldap://ldapmaster.symas.com

The above configuration assumes that you have a replicator identity defined in your database that can be used to bind to the provider. In addition, all of the databases (primary, replica, and the accesslog storage database) should also have properly tuned DB_CONFIG files that meet your needs.

18.3.3. N-Way Multi-Master

For the following example we will be using 3 Master nodes. Keeping in line with test050-syncrepl-multimaster of the OpenLDAP test suite, we will be configuring slapd(8) via cn=config

This sets up the config database:

     dn: cn=config
     objectClass: olcGlobal
     cn: config
     olcServerID: 1

     dn: olcDatabase={0}config,cn=config
     objectClass: olcDatabaseConfig
     olcDatabase: {0}config
     olcRootPW: secret

second and third servers will have a different olcServerID obviously:

     dn: cn=config
     objectClass: olcGlobal
     cn: config
     olcServerID: 2

     dn: olcDatabase={0}config,cn=config
     objectClass: olcDatabaseConfig
     olcDatabase: {0}config
     olcRootPW: secret

This sets up syncrepl as a provider (since these are all masters):

     dn: cn=module,cn=config
     objectClass: olcModuleList
     cn: module
     olcModulePath: /usr/local/libexec/openldap
     olcModuleLoad: syncprov.la

Now we setup the first Master Node (replace $URI1, $URI2 and $URI3 etc. with your actual ldap urls):

     dn: cn=config
     changetype: modify
     replace: olcServerID
     olcServerID: 1 $URI1
     olcServerID: 2 $URI2
     olcServerID: 3 $URI3

     dn: olcOverlay=syncprov,olcDatabase={0}config,cn=config
     changetype: add
     objectClass: olcOverlayConfig
     objectClass: olcSyncProvConfig
     olcOverlay: syncprov

     dn: olcDatabase={0}config,cn=config
     changetype: modify
     add: olcSyncRepl
     olcSyncRepl: rid=001 provider=$URI1 binddn="cn=config" bindmethod=simple
       credentials=secret searchbase="cn=config" type=refreshAndPersist
       retry="5 5 300 5" timeout=1
     olcSyncRepl: rid=002 provider=$URI2 binddn="cn=config" bindmethod=simple
       credentials=secret searchbase="cn=config" type=refreshAndPersist
       retry="5 5 300 5" timeout=1
     olcSyncRepl: rid=003 provider=$URI3 binddn="cn=config" bindmethod=simple
       credentials=secret searchbase="cn=config" type=refreshAndPersist
       retry="5 5 300 5" timeout=1
     -
     add: olcMirrorMode
     olcMirrorMode: TRUE

Now start up the Master and a consumer/s, also add the above LDIF to the first consumer, second consumer etc. It will then replicate cn=config. You now have N-Way Multimaster on the config database.

We still have to replicate the actual data, not just the config, so add to the master (all active and configured consumers/masters will pull down this config, as they are all syncing). Also, replace all ${} variables with whatever is applicable to your setup:

     dn: olcDatabase={1}$BACKEND,cn=config
     objectClass: olcDatabaseConfig
     objectClass: olc${BACKEND}Config
     olcDatabase: {1}$BACKEND
     olcSuffix: $BASEDN
     olcDbDirectory: ./db
     olcRootDN: $MANAGERDN
     olcRootPW: $PASSWD
     olcLimits: dn.exact="$MANAGERDN" time.soft=unlimited time.hard=unlimited size.soft=unlimited size.hard=unlimited
     olcSyncRepl: rid=004 provider=$URI1 binddn="$MANAGERDN" bindmethod=simple
       credentials=$PASSWD searchbase="$BASEDN" type=refreshOnly
       interval=00:00:00:10 retry="5 5 300 5" timeout=1
     olcSyncRepl: rid=005 provider=$URI2 binddn="$MANAGERDN" bindmethod=simple
       credentials=$PASSWD searchbase="$BASEDN" type=refreshOnly
       interval=00:00:00:10 retry="5 5 300 5" timeout=1
     olcSyncRepl: rid=006 provider=$URI3 binddn="$MANAGERDN" bindmethod=simple
       credentials=$PASSWD searchbase="$BASEDN" type=refreshOnly
       interval=00:00:00:10 retry="5 5 300 5" timeout=1
     olcMirrorMode: TRUE

     dn: olcOverlay=syncprov,olcDatabase={1}${BACKEND},cn=config
     changetype: add
     objectClass: olcOverlayConfig
     objectClass: olcSyncProvConfig
     olcOverlay: syncprov


Note: All of your servers' clocks must be tightly synchronized using e.g. NTP http://www.ntp.org/, atomic clock, or some other reliable time reference.


Note: As stated in slapd-config(5), URLs specified in olcSyncRepl directives are the URLs of the servers from which to replicate. These must exactly match the URLs slapd listens on (-h in Command-Line Options). Otherwise slapd may attempt to replicate from itself, causing a loop.

18.3.4. MirrorMode

MirrorMode configuration is actually very easy. If you have ever setup a normal slapd syncrepl provider, then the only change is the following two directives:

       mirrormode  on
       serverID    1


Note: You need to make sure that the serverID of each mirror node is different and add it as a global configuration option.

18.3.4.1. Mirror Node Configuration

The first step is to configure the syncrepl provider the same as in the Set up the provider slapd section.

Here's a specific cut down example using LDAP Sync Replication in refreshAndPersist mode:

MirrorMode node 1:

       # Global section
       serverID    1
       # database section

       # syncrepl directive
       syncrepl      rid=001
                     provider=ldap://ldap-sid2.example.com
                     bindmethod=simple
                     binddn="cn=mirrormode,dc=example,dc=com"
                     credentials=mirrormode
                     searchbase="dc=example,dc=com"
                     schemachecking=on
                     type=refreshAndPersist
                     retry="60 +"

       mirrormode on

MirrorMode node 2:

       # Global section
       serverID    2
       # database section

       # syncrepl directive
       syncrepl      rid=001
                     provider=ldap://ldap-sid1.example.com
                     bindmethod=simple
                     binddn="cn=mirrormode,dc=example,dc=com"
                     credentials=mirrormode
                     searchbase="dc=example,dc=com"
                     schemachecking=on
                     type=refreshAndPersist
                     retry="60 +"

       mirrormode on

It's simple really; each MirrorMode node is setup exactly the same, except that the serverID is unique, and each consumer is pointed to the other server.

18.3.4.1.1. Failover Configuration

There are generally 2 choices for this; 1. Hardware proxies/load-balancing or dedicated proxy software, 2. using a Back-LDAP proxy as a syncrepl provider

A typical enterprise example might be:

Figure X.Y: MirrorMode in a Dual Data Center Configuration

18.3.4.1.2. Normal Consumer Configuration

This is exactly the same as the Set up the consumer slapd section. It can either setup in normal syncrepl replication mode, or in delta-syncrepl replication mode.

18.3.4.2. MirrorMode Summary

You will now have a directory architecture that provides all of the consistency guarantees of single-master replication, while also providing the high availability of multi-master replication.

18.3.5. Syncrepl Proxy

Figure X.Y: Replacing slurpd

The following example is for a self-contained push-based replication solution:

        #######################################################################
        # Standard OpenLDAP Master/Provider
        #######################################################################

        include     /usr/local/etc/openldap/schema/core.schema
        include     /usr/local/etc/openldap/schema/cosine.schema
        include     /usr/local/etc/openldap/schema/nis.schema
        include     /usr/local/etc/openldap/schema/inetorgperson.schema

        include     /usr/local/etc/openldap/slapd.acl

        modulepath  /usr/local/libexec/openldap
        moduleload  back_hdb.la
        moduleload  syncprov.la
        moduleload  back_monitor.la
        moduleload  back_ldap.la

        pidfile     /usr/local/var/slapd.pid
        argsfile    /usr/local/var/slapd.args

        loglevel    sync stats

        database    hdb
        suffix      "dc=suretecsystems,dc=com"
        directory   /usr/local/var/openldap-data

        checkpoint      1024 5
        cachesize       10000
        idlcachesize    10000

        index       objectClass eq
        # rest of indexes
        index       default     sub

        rootdn          "cn=admin,dc=suretecsystems,dc=com"
        rootpw          testing

        # syncprov specific indexing
        index entryCSN eq
        index entryUUID eq

        # syncrepl Provider for primary db
        overlay syncprov
        syncprov-checkpoint 1000 60

        # Let the replica DN have limitless searches
        limits dn.exact="cn=replicator,dc=suretecsystems,dc=com" time.soft=unlimited time.hard=unlimited size.soft=unlimited size.hard=unlimited

        database    monitor

        database    config
        rootpw          testing

        ##############################################################################
        # Consumer Proxy that pulls in data via Syncrepl and pushes out via slapd-ldap
        ##############################################################################

        database        ldap
        # ignore conflicts with other databases, as we need to push out to same suffix
        hidden              on
        suffix          "dc=suretecsystems,dc=com"
        rootdn          "cn=slapd-ldap"
        uri             ldap://localhost:9012/

        lastmod         on

        # We don't need any access to this DSA
        restrict        all

        acl-bind        bindmethod=simple
                        binddn="cn=replicator,dc=suretecsystems,dc=com"
                        credentials=testing

        syncrepl        rid=001
                        provider=ldap://localhost:9011/
                        binddn="cn=replicator,dc=suretecsystems,dc=com"
                        bindmethod=simple
                        credentials=testing
                        searchbase="dc=suretecsystems,dc=com"
                        type=refreshAndPersist
                        retry="5 5 300 5"

        overlay         syncprov

A replica configuration for this type of setup could be:

        #######################################################################
        # Standard OpenLDAP Slave without Syncrepl
        #######################################################################

        include     /usr/local/etc/openldap/schema/core.schema
        include     /usr/local/etc/openldap/schema/cosine.schema
        include     /usr/local/etc/openldap/schema/nis.schema
        include     /usr/local/etc/openldap/schema/inetorgperson.schema

        include     /usr/local/etc/openldap/slapd.acl

        modulepath  /usr/local/libexec/openldap
        moduleload  back_hdb.la
        moduleload  syncprov.la
        moduleload  back_monitor.la
        moduleload  back_ldap.la

        pidfile     /usr/local/var/slapd.pid
        argsfile    /usr/local/var/slapd.args

        loglevel    sync stats

        database    hdb
        suffix      "dc=suretecsystems,dc=com"
        directory   /usr/local/var/openldap-slave/data

        checkpoint      1024 5
        cachesize       10000
        idlcachesize    10000

        index       objectClass eq
        # rest of indexes
        index       default     sub

        rootdn          "cn=admin,dc=suretecsystems,dc=com"
        rootpw          testing

        # Let the replica DN have limitless searches
        limits dn.exact="cn=replicator,dc=suretecsystems,dc=com" time.soft=unlimited time.hard=unlimited size.soft=unlimited size.hard=unlimited

        updatedn "cn=replicator,dc=suretecsystems,dc=com"

        # Refer updates to the master
        updateref   ldap://localhost:9011

        database    monitor

        database    config
        rootpw          testing

You can see we use the updatedn directive here and example ACLs (usr/local/etc/openldap/slapd.acl) for this could be:

        # Give the replica DN unlimited read access.  This ACL may need to be
        # merged with other ACL statements.

        access to *
             by dn.base="cn=replicator,dc=suretecsystems,dc=com" write
             by * break

        access to dn.base=""
                by * read

        access to dn.base="cn=Subschema"
                by * read

        access to dn.subtree="cn=Monitor"
            by dn.exact="uid=admin,dc=suretecsystems,dc=com" write
            by users read
            by * none

        access to *
                by self write
                by * read

In order to support more replicas, just add more database ldap sections and increment the syncrepl rid number accordingly.


Note: You must populate the Master and Slave directories with the same data, unlike when using normal Syncrepl

If you do not have access to modify the master directory configuration you can configure a standalone ldap proxy, which might look like:

Figure X.Y: Replacing slurpd with a standalone version

The following configuration is an example of a standalone LDAP Proxy:

        include     /usr/local/etc/openldap/schema/core.schema
        include     /usr/local/etc/openldap/schema/cosine.schema
        include     /usr/local/etc/openldap/schema/nis.schema
        include     /usr/local/etc/openldap/schema/inetorgperson.schema

        include     /usr/local/etc/openldap/slapd.acl

        modulepath  /usr/local/libexec/openldap
        moduleload  syncprov.la
        moduleload  back_ldap.la

        ##############################################################################
        # Consumer Proxy that pulls in data via Syncrepl and pushes out via slapd-ldap
        ##############################################################################

        database        ldap
        # ignore conflicts with other databases, as we need to push out to same suffix
        hidden              on
        suffix          "dc=suretecsystems,dc=com"
        rootdn          "cn=slapd-ldap"
        uri             ldap://localhost:9012/

        lastmod         on

        # We don't need any access to this DSA
        restrict        all

        acl-bind        bindmethod=simple
                        binddn="cn=replicator,dc=suretecsystems,dc=com"
                        credentials=testing

        syncrepl        rid=001
                        provider=ldap://localhost:9011/
                        binddn="cn=replicator,dc=suretecsystems,dc=com"
                        bindmethod=simple
                        credentials=testing
                        searchbase="dc=suretecsystems,dc=com"
                        type=refreshAndPersist
                        retry="5 5 300 5"

        overlay         syncprov

As you can see, you can let your imagination go wild using Syncrepl and slapd-ldap(8) tailoring your replication to fit your specific network topology.


19. Maintenance

System Administration is all about maintenance, so it is only fair that we discuss how to correctly maintain an OpenLDAP deployment.

19.1. Directory Backups

Backup strategies largely depend on the amount of change in the database and how much of that change an administrator might be willing to lose in a catastrophic failure. There are two basic methods that can be used:

1. Backup the Berkeley database itself and periodically back up the transaction log files:

Berkeley DB produces transaction logs that can be used to reconstruct changes from a given point in time. For example, if an administrator were willing to only lose one hour's worth of changes, they could take down the server in the middle of the night, copy the Berkeley database files offsite, and bring the server back online. Then, on an hourly basis, they could force a database checkpoint, capture the log files that have been generated in the past hour, and copy them offsite. The accumulated log files, in combination with the previous database backup, could be used with db_recover to reconstruct the database up to the time the last collection of log files was copied offsite. This method affords good protection, with minimal space overhead.

2. Periodically run slapcat and back up the LDIF file:

Slapcat can be run while slapd is active. However, one runs the risk of an inconsistent database- not from the point of slapd, but from the point of the applications using LDAP. For example, if a provisioning application performed tasks that consisted of several LDAP operations, and the slapcat took place concurrently with those operations, then there might be inconsistencies in the LDAP database from the point of view of that provisioning application and applications that depended on it. One must, therefore, be convinced something like that won't happen. One way to do that would be to put the database in read-only mode while performing the slapcat. The other disadvantage of this approach is that the generated LDIF files can be rather large and the accumulation of the day's backups could add up to a substantial amount of space.

You can use slapcat(8) to generate an LDIF file for each of your slapd(8) back-bdb or back-hdb databases.

    slapcat -f slapd.conf -b "dc=example,dc=com"

For back-bdb and back-hdb, this command may be ran while slapd(8) is running.

MORE on actual Berkeley DB backups later covering db_recover etc.

19.2. Berkeley DB Logs

Berkeley DB log files grow, and the administrator has to deal with it. The procedure is known as log file archival or log file rotation.


Note: The actual log file rotation is handled by the Berkeley DB engine.

Logs of current transactions need to be stored into files so that the database can be recovered in the event of an application crash. Administrators can change the size limit of a single log file (by default 10MB), and have old log files removed automatically, by setting up DB environment (see below). The reason Berkeley DB never deletes any log files by default is that the administrator may wish to backup the log files before removal to make database recovery possible even after a catastrophic failure, such as file system corruption.

Log file names are log.XXXXXXXXXX (X is a digit). By default the log files are located in the BDB backend directory. The db_archive tool knows what log files are used in current transactions, and what are not. Administrators can move unused log files to a backup media, and delete them. To have them removed automatically, place set_flags DB_LOG_AUTOREMOVE directive in DB_CONFIG.


Note: If the log files are removed automatically, recovery after a catastrophic failure is likely to be impossible.

The files with names __db.001, __db.002, etc are just shared memory regions (or whatever). These ARE NOT 'logs', they must be left alone. Don't be afraid of them, they do not grow like logs do.

To understand the db_archive interface, the reader should refer to chapter 9 of the Berkeley DB guide. In particular, the following chapters are recommended:

Advanced installations can use special environment settings to fine-tune some Berkeley DB options (change the log file limit, etc). This can be done by using the DB_CONFIG file. This magic file can be created in BDB backend directory set up by slapd.conf(5). More information on this file can be found in File naming chapter. Specific directives can be found in C Interface, look for DB_ENV->set_XXXX calls.


Note: options set in DB_CONFIG file override options set by OpenLDAP. Use them with extreme caution. Do not use them unless You know what You are doing.

The advantages of DB_CONFIG usage can be the following:

To figure out the best-practice BDB backup scenario, the reader is highly recommended to read the whole Chapter 9: Berkeley DB Transactional Data Store Applications. This chapter is a set of small pages with examples in C language. Non-programming people can skip these examples without loss of knowledge.

19.3. Checkpointing

MORE/TIDY

If you put "checkpoint 1024 5" in slapd.conf (to checkpoint after 1024kb or 5 minutes, for example), this does not checkpoint every 5 minutes as you may think. The explanation from Howard is:

'In OpenLDAP 2.1 and 2.2 the checkpoint directive acts as follows - *when there is a write operation*, and more than <check> minutes have occurred since the last checkpoint, perform the checkpoint. If more than <check> minutes pass after a write without any other write operations occurring, no checkpoint is performed, so it's possible to lose the last write that occurred.''

In other words, a write operation occurring less than "check" minutes after the last checkpoint will not be checkpointed until the next write occurs after "check" minutes have passed since the checkpoint.

This has been modified in 2.3 to indeed checkpoint every so often; in the meantime a workaround is to invoke "db_checkpoint" from a cron script every so often, say 5 minutes.

19.4. Migration

The simplest steps needed to migrate between versions or upgrade, depending on your deployment type are:

  1. Stop the current server when convenient
     
  2. slapcat the current data out
     
  3. Clear out the current data directory (/usr/local/var/openldap-data/) leaving DB_CONFIG in place
     
  4. Perform the software upgrades
     
  5. slapadd the exported data back into the directory
     
  6. Start the server

Obviously this doesn't cater for any complicated deployments like MirrorMode or N-Way Multi-Master, but following the above sections and using either commercial support or community support should help. Also check the Troubleshooting section.


20. Monitoring

slapd(8) supports an optional LDAP monitoring interface you can use to obtain information regarding the current state of your slapd instance. For instance, the interface allows you to determine how many clients are connected to the server currently. The monitoring information is provided by a specialized backend, the monitor backend. A manual page, slapd-monitor(5) is available.

When the monitoring interface is enabled, LDAP clients may be used to access information provided by the monitor backend, subject to access and other controls.

When enabled, the monitor backend dynamically generates and returns objects in response to search requests in the cn=Monitor subtree. Each object contains information about a particular aspect of the server. The information is held in a combination of user applications and operational attributes. This information can be access with ldapsearch(1), with any general-purpose LDAP browser, or with specialized monitoring tools. The Accessing Monitoring Information section provides a brief tutorial on how to use ldapsearch(1) to access monitoring information, while the Monitor information section details monitoring information base and its organization.

While support for the monitor backend is included in default builds of slapd(8), this support requires some configuration to become active. This may be done using either cn=config or slapd.conf(5). The former is discussed in the Monitor configuration via cn=config section of this of this chapter. The latter is discussed in the Monitor configuration via slapd.conf(5) section of this chapter. These sections assume monitor backend is built into slapd (e.g., --enable-monitor=yes, the default). If the monitor backend was built as a module (e.g., --enable-monitor=mod, this module must loaded. Loading of modules is discussed in the Configuring slapd and The slapd Configuration File chapters.

20.1. Monitor configuration via cn=config(5)

This section has yet to be written.

20.2. Monitor configuration via slapd.conf(5)

Configuration of the slapd.conf(5) to support LDAP monitoring is quite simple.

First, ensure core.schema schema configuration file is included by your slapd.conf(5) file. The monitor backend requires it.

Second, instantiate the monitor backend by adding a database monitor directive below your existing database sections. For instance:

        database monitor

Lastly, add additional global or database directives as needed.

Like most other database backends, the monitor backend does honor slapd(8) access and other administrative controls. As some monitor information may be sensitive, it is generally recommend access to cn=monitor be restricted to directory administrators and their monitoring agents. Adding an access directive immediately below the database monitor directive is a clear and effective approach for controlling access. For instance, the addition of the following access directive immediately below the database monitor directive restricts access to monitoring information to the specified directory manager.

        access to *
                by dn.exact="cn=Manager,dc=example,dc=com
                by * none

More information on slapd(8) access controls, see The access Control Directive section of the The slapd Configuration File chapter and slapd.access(5).

After restarting slapd(8), you are ready to start exploring the monitoring information provided in cn=config as discussed in the Accessing Monitoring Information section of this chapter.

One can verify slapd(8) is properly configured to provide monitoring information by attempting to read the cn=monitor object. For instance, if the following ldapsearch(1) command returns the cn=monitor object (with, as requested, no attributes), it's working.

        ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
                -b 'cn=Monitor' -s base 1.1

Note that unlike general purpose database backends, the database suffix is hardcoded. It's always cn=Monitor. So no suffix directive should be provided. Also note that general purpose database backends, the monitor backend cannot be instantiated multiple times. That is, there can only be one (or zero) occurrences of database monitor in the server's configuration.

20.3. Accessing Monitoring Information

As previously discussed, when enabled, the monitor backend dynamically generates and returns objects in response to search requests in the cn=Monitor subtree. Each object contains information about a particular aspect of the server. The information is held in a combination of user applications and operational attributes. This information can be access with ldapsearch(1), with any general-purpose LDAP browser, or with specialized monitoring tools.

This section provides a provides a brief tutorial on how to use ldapsearch(1) to access monitoring information.

To inspect any particular monitor object, one performs search operation on the object with a baseObject scope and a (objectClass=*) filter. As the monitoring information is contained in a combination of user applications and operational attributes, the return all user applications attributes (e.g., '*') and all operational attributes (e.g., '+') should be requested. For instance, to read the cn=Monitor object itself, the ldapsearch(1) command (modified to fit your configuration) can be used:

        ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
                -b 'cn=Monitor' -s base '(objectClass=*)' '*' '+'

When run against your server, this should produce output similar to:

        dn: cn=Monitor
        objectClass: monitorServer
        structuralObjectClass: monitorServer
        cn: Monitor
        creatorsName:
        modifiersName:
        createTimestamp: 20061208223558Z
        modifyTimestamp: 20061208223558Z
        description: This subtree contains monitoring/managing objects.
        description: This object contains information about this server.
        description: Most of the information is held in operational attributes, which
         must be explicitly requested.
        monitoredInfo: OpenLDAP: slapd 2.4 (Dec  7 2006 17:30:29)
        entryDN: cn=Monitor
        subschemaSubentry: cn=Subschema
        hasSubordinates: TRUE

To reduce the number of uninteresting attributes returned, one can be more selective when requesting which attributes are to be returned. For instance, one could request the return of all attributes allowed by the monitorServer object class (e.g., @objectClass) instead of all user and all operational attributes:

        ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
                -b 'cn=Monitor' -s base '(objectClass=*)' '@monitorServer'

This limits the output as follows:

        dn: cn=Monitor
        objectClass: monitorServer
        cn: Monitor
        description: This subtree contains monitoring/managing objects.
        description: This object contains information about this server.
        description: Most of the information is held in operational attributes, which
         must be explicitly requested.
        monitoredInfo: OpenLDAP: slapd 2.X (Dec  7 2006 17:30:29)

To return the names of all the monitoring objects, one performs a search of cn=Monitor with subtree scope and (objectClass=*) filter and requesting no attributes (e.g., 1.1) be returned.

        ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W -b 'cn=Monitor' -s sub 1.1

If you run this command you will discover that there are many objects in the cn=Monitor subtree. The following section describes some of the commonly available monitoring objects.

20.4. Monitor Information

The monitor backend provides a wealth of information useful for monitoring the slapd(8) contained in set of monitor objects. Each object contains information about a particular aspect of the server, such as a backends, a connection, or a thread. Some objects serve as containers for other objects and used to construct a hierarchy of objects.

In this hierarchy, the most superior object is {cn=Monitor}. While this object primarily serves as a container for other objects, most of which are containers, this object provides information about this server. In particular, it provides the slapd(8) version string. Example:

        dn: cn=Monitor
        monitoredInfo: OpenLDAP: slapd 2.X (Dec  7 2006 17:30:29)


Note: Examples in this section (and its subsections) have been trimmed to show only key information.

20.4.1. Backends

The cn=Backends,cn=Monitor object, itself, provides a list of available backends. The list of available backends all builtin backends, as well as backends loaded by modules. For example:

        dn: cn=Backends,cn=Monitor
        monitoredInfo: config
        monitoredInfo: ldif
        monitoredInfo: monitor
        monitoredInfo: bdb
        monitoredInfo: hdb

This indicates the config, ldif, monitor, bdb, and hdb backends are available.

The cn=Backends,cn=Monitor object is also a container for available backend objects. Each available backend object contains information about a particular backend. For example:

        dn: cn=Backend 0,cn=Backends,cn=Monitor
        monitoredInfo: config
        monitorRuntimeConfig: TRUE
        supportedControl: 2.16.840.1.113730.3.4.2
        seeAlso: cn=Database 0,cn=Databases,cn=Monitor

        dn: cn=Backend 1,cn=Backends,cn=Monitor
        monitoredInfo: ldif
        monitorRuntimeConfig: TRUE
        supportedControl: 2.16.840.1.113730.3.4.2

        dn: cn=Backend 2,cn=Backends,cn=Monitor
        monitoredInfo: monitor
        monitorRuntimeConfig: TRUE
        supportedControl: 2.16.840.1.113730.3.4.2
        seeAlso: cn=Database 2,cn=Databases,cn=Monitor

        dn: cn=Backend 3,cn=Backends,cn=Monitor
        monitoredInfo: bdb
        monitorRuntimeConfig: TRUE
        supportedControl: 1.3.6.1.1.12
        supportedControl: 2.16.840.1.113730.3.4.2
        supportedControl: 1.3.6.1.4.1.4203.666.5.2
        supportedControl: 1.2.840.113556.1.4.319
        supportedControl: 1.3.6.1.1.13.1
        supportedControl: 1.3.6.1.1.13.2
        supportedControl: 1.3.6.1.4.1.4203.1.10.1
        supportedControl: 1.2.840.113556.1.4.1413
        supportedControl: 1.3.6.1.4.1.4203.666.11.7.2
        seeAlso: cn=Database 1,cn=Databases,cn=Monitor

        dn: cn=Backend 4,cn=Backends,cn=Monitor
        monitoredInfo: hdb
        monitorRuntimeConfig: TRUE
        supportedControl: 1.3.6.1.1.12
        supportedControl: 2.16.840.1.113730.3.4.2
        supportedControl: 1.3.6.1.4.1.4203.666.5.2
        supportedControl: 1.2.840.113556.1.4.319
        supportedControl: 1.3.6.1.1.13.1
        supportedControl: 1.3.6.1.1.13.2
        supportedControl: 1.3.6.1.4.1.4203.1.10.1
        supportedControl: 1.2.840.113556.1.4.1413
        supportedControl: 1.3.6.1.4.1.4203.666.11.7.2

For each of these objects, monitorInfo indicates which backend the information in the object is about. For instance, the cn=Backend 3,cn=Backends,cn=Monitor object contains (in the example) information about the bdb backend.

Attribute Description
monitoredInfo Name of backend
supportedControl supported LDAP control extensions
seeAlso Database objects of instances of this backend

20.4.2. Connections

The main entry is empty; it should contain some statistics on the number of connections.

Dynamic child entries are created for each open connection, with stats on the activity on that connection (the format will be detailed later). There are two special child entries that show the number of total and current connections respectively.

For example:

Total Connections:

   dn: cn=Total,cn=Connections,cn=Monitor
   structuralObjectClass: monitorCounterObject
   monitorCounter: 4
   entryDN: cn=Total,cn=Connections,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

Current Connections:

   dn: cn=Current,cn=Connections,cn=Monitor
   structuralObjectClass: monitorCounterObject
   monitorCounter: 2
   entryDN: cn=Current,cn=Connections,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

20.4.3. Databases

The main entry contains the naming context of each configured database; the child entries contain, for each database, the type and the naming context.

For example:

   dn: cn=Database 2,cn=Databases,cn=Monitor
   structuralObjectClass: monitoredObject
   monitoredInfo: monitor
   monitorIsShadow: FALSE
   monitorContext: cn=Monitor
   readOnly: FALSE
   entryDN: cn=Database 2,cn=Databases,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

20.4.4. Listener

It contains the description of the devices the server is currently listening on:

   dn: cn=Listener 0,cn=Listeners,cn=Monitor
   structuralObjectClass: monitoredObject
   monitorConnectionLocalAddress: IP=0.0.0.0:389
   entryDN: cn=Listener 0,cn=Listeners,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

20.4.5. Log

It contains the currently active log items. The Log subsystem allows user modify operations on the description attribute, whose values MUST be in the list of admittable log switches:

   Trace
   Packets
   Args
   Conns
   BER
   Filter
   Config
   ACL
   Stats
   Stats2
   Shell
   Parse
   Sync

These values can be added, replaced or deleted; they affect what messages are sent to the syslog device. Custom values could be added by custom modules.

20.4.6. Operations

It shows some statistics on the operations performed by the server:

   Initiated
   Completed

and for each operation type, i.e.:

   Bind
   Unbind
   Add
   Delete
   Modrdn
   Modify
   Compare
   Search
   Abandon
   Extended

There are too many types to list example here, so please try for yourself using Monitor search example

20.4.7. Overlays

The main entry contains the type of overlays available at run-time; the child entries, for each overlay, contain the type of the overlay.

It should also contain the modules that have been loaded if dynamic overlays are enabled:

   # Overlays, Monitor
   dn: cn=Overlays,cn=Monitor
   structuralObjectClass: monitorContainer
   monitoredInfo: syncprov
   monitoredInfo: accesslog
   monitoredInfo: glue
   entryDN: cn=Overlays,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: TRUE

20.4.8. SASL

Currently empty.

20.4.9. Statistics

It shows some statistics on the data sent by the server:

   Bytes
   PDU
   Entries
   Referrals

e.g.

   # Entries, Statistics, Monitor
   dn: cn=Entries,cn=Statistics,cn=Monitor
   structuralObjectClass: monitorCounterObject
   monitorCounter: 612248
   entryDN: cn=Entries,cn=Statistics,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

20.4.10. Threads

It contains the maximum number of threads enabled at startup and the current backload.

e.g.

   # Max, Threads, Monitor
   dn: cn=Max,cn=Threads,cn=Monitor
   structuralObjectClass: monitoredObject
   monitoredInfo: 16
   entryDN: cn=Max,cn=Threads,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

20.4.11. Time

It contains two child entries with the start time and the current time of the server.

e.g.

Start time:

   dn: cn=Start,cn=Time,cn=Monitor
   structuralObjectClass: monitoredObject
   monitorTimestamp: 20061205124040Z
   entryDN: cn=Start,cn=Time,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

Current time:

   dn: cn=Current,cn=Time,cn=Monitor
   structuralObjectClass: monitoredObject
   monitorTimestamp: 20061207120624Z
   entryDN: cn=Current,cn=Time,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

20.4.12. TLS

Currently empty.

20.4.13. Waiters

It contains the number of current read waiters.

e.g.

Read waiters:

   dn: cn=Read,cn=Waiters,cn=Monitor
   structuralObjectClass: monitorCounterObject
   monitorCounter: 7
   entryDN: cn=Read,cn=Waiters,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

Write waiters:

   dn: cn=Write,cn=Waiters,cn=Monitor
   structuralObjectClass: monitorCounterObject
   monitorCounter: 0
   entryDN: cn=Write,cn=Waiters,cn=Monitor
   subschemaSubentry: cn=Subschema
   hasSubordinates: FALSE

Add new monitored things here and discuss, referencing man pages and present examples


21. Tuning

This is perhaps one of the most important chapters in the guide, because if you have not tuned slapd(8) correctly or grasped how to design your directory and environment, you can expect very poor performance.

Reading, understanding and experimenting using the instructions and information in the following sections, will enable you to fully understand how to tailor your directory server to your specific requirements.

It should be noted that the following information has been collected over time from our community based FAQ. So obviously the benefit of this real world experience and advice should be of great value to the reader.

21.1. Performance Factors

Various factors can play a part in how your directory performs on your chosen hardware and environment. We will attempt to discuss these here.

21.1.1. Memory

Scale your cache to use available memory and increase system memory if you can.

See Caching for BDB cache tuning hints. Note that LMDB uses no cache of its own and has no tuning options, so the Caching section can be ignored when using LMDB.

21.1.2. Disks

Use fast filesystems, and conduct your own testing to see which filesystem types perform best with your workload. (On our own Linux testing, EXT2 and JFS tend to provide better write performance than everything else, including newer filesystems like EXT4, BTRFS, etc.)

Use fast subsystems. Put each database and logs on separate disks (for BDB this is configurable via DB_CONFIG):

       # Data Directory
       set_data_dir /data/db

       # Transaction Log settings
       set_lg_dir /logs

21.1.3. Network Topology

http://www.openldap.org/faq/data/cache/363.html

Drawing here.

21.1.4. Directory Layout Design

Reference to other sections and good/bad drawing here.

21.1.5. Expected Usage

Discussion.

21.2. Indexes

21.2.1. Understanding how a search works

If you're searching on a filter that has been indexed, then the search reads the index and pulls exactly the entries that are referenced by the index. If the filter term has not been indexed, then the search must read every single entry in the target scope and test to see if each entry matches the filter. Obviously indexing can save a lot of work when it's used correctly.

21.2.2. What to index

You should create indices to match the actual filter terms used in search queries.

        index cn,sn,givenname,mail eq

Each attribute index can be tuned further by selecting the set of index types to generate. For example, substring and approximate search for organizations (o) may make little sense (and isn't like done very often). And searching for userPassword likely makes no sense what so ever.

General rule: don't go overboard with indexes. Unused indexes must be maintained and hence can only slow things down.

See slapd.conf(8) and slapdindex(8) for more information

21.2.3. Presence indexing

If your client application uses presence filters and if the target attribute exists on the majority of entries in your target scope, then all of those entries are going to be read anyway, because they are valid members of the result set. In a subtree where 100% of the entries are going to contain the same attributes, the presence index does absolutely NOTHING to benefit the search, because 100% of the entries match that presence filter.

So the resource cost of generating the index is a complete waste of CPU time, disk, and memory. Don't do it unless you know that it will be used, and that the attribute in question occurs very infrequently in the target data.

Almost no applications use presence filters in their search queries. Presence indexing is pointless when the target attribute exists on the majority of entries in the database. In most LDAP deployments, presence indexing should not be done, it's just wasted overhead.

See the Logging section below on what to watch our for if you have a frequently searched for attribute that is unindexed.

21.3. Logging

21.3.1. What log level to use

The default of loglevel stats (256) is really the best bet. There's a corollary to this when problems *do* arise, don't try to trace them using syslog. Use the debug flag instead, and capture slapd's stderr output. syslog is too slow for debug tracing, and it's inherently lossy - it will throw away messages when it can't keep up.

Contrary to popular belief, loglevel 0 is not ideal for production as you won't be able to track when problems first arise.

21.3.2. What to watch out for

The most common message you'll see that you should pay attention to is:

       "<= bdb_equality_candidates: (foo) index_param failed (18)"

That means that some application tried to use an equality filter (foo=<somevalue>) and attribute foo does not have an equality index. If you see a lot of these messages, you should add the index. If you see one every month or so, it may be acceptable to ignore it.

The default syslog level is stats (256) which logs the basic parameters of each request; it usually produces 1-3 lines of output. On Solaris and systems that only provide synchronous syslog, you may want to turn it off completely, but usually you want to leave it enabled so that you'll be able to see index messages whenever they arise. On Linux you can configure syslogd to run asynchronously, in which case the performance hit for moderate syslog traffic pretty much disappears.

21.3.3. Improving throughput

You can improve logging performance on some systems by configuring syslog not to sync the file system with every write (man syslogd/syslog.conf). In Linux, you can prepend the log file name with a "-" in syslog.conf. For example, if you are using the default LOCAL4 logging you could try:

       # LDAP logs
       LOCAL4.*         -/var/log/ldap

For syslog-ng, add or modify the following line in syslog-ng.conf:

       options { sync(n); };

where n is the number of lines which will be buffered before a write.

21.4. Caching

We all know what caching is, don't we?

In brief, "A cache is a block of memory for temporary storage of data likely to be used again" - http://en.wikipedia.org/wiki/Cache

There are 3 types of caches, BerkeleyDB's own cache, slapd(8) entry cache and IDL (IDL) cache.

21.4.1. Berkeley DB Cache

There are two ways to tune for the BDB cachesize:

(a) BDB cache size necessary to load the database via slapadd in optimal time

(b) BDB cache size necessary to have a high performing running slapd once the data is loaded

For (a), the optimal cachesize is the size of the entire database. If you already have the database loaded, this is simply a

       du -c -h *.bdb

in the directory containing the OpenLDAP (/usr/local/var/openldap-data) data.

For (b), the optimal cachesize is just the size of the id2entry.bdb file, plus about 10% for growth.

The tuning of DB_CONFIG should be done for each BDB type database instantiated (back-bdb, back-hdb).

Note that while the BDB cache is just raw chunks of memory and configured as a memory size, the slapd(8) entry cache holds parsed entries, and the size of each entry is variable.

There is also an IDL cache which is used for Index Data Lookups. If you can fit all of your database into slapd's entry cache, and all of your index lookups fit in the IDL cache, that will provide the maximum throughput.

If not, but you can fit the entire database into the BDB cache, then you should do that and shrink the slapd entry cache as appropriate.

Failing that, you should balance the BDB cache against the entry cache.

It is worth noting that it is not absolutely necessary to configure a BerkeleyDB cache equal in size to your entire database. All that you need is a cache that's large enough for your "working set."

That means, large enough to hold all of the most frequently accessed data, plus a few less-frequently accessed items.

For more information, please see: http://www.oracle.com/technology/documentation/berkeley-db/db/ref/am_conf/cachesize.html

21.4.1.1. Calculating Cachesize

The back-bdb database lives in two main files, dn2id.bdb and id2entry.bdb. These are B-tree databases. We have never documented the back-bdb internal layout before, because it didn't seem like something anyone should have to worry about, nor was it necessarily cast in stone. But here's how it works today, in OpenLDAP 2.4.

A B-tree is a balanced tree; it stores data in its leaf nodes and bookkeeping data in its interior nodes (If you don't know what tree data structures look like in general, Google for some references, because that's getting far too elementary for the purposes of this discussion).

For decent performance, you need enough cache memory to contain all the nodes along the path from the root of the tree down to the particular data item you're accessing. That's enough cache for a single search. For the general case, you want enough cache to contain all the internal nodes in the database.

       db_stat -d

will tell you how many internal pages are present in a database. You should check this number for both dn2id and id2entry.

Also note that id2entry always uses 16KB per "page", while dn2id uses whatever the underlying filesystem uses, typically 4 or 8KB. To avoid thrashing, your cache must be at least as large as the number of internal pages in both the dn2id and id2entry databases, plus some extra space to accommodate the actual leaf data pages.

For example, in my OpenLDAP 2.4 test database, I have an input LDIF file that's about 360MB. With the back-hdb backend this creates a dn2id.bdb that's 68MB, and an id2entry that's 800MB. db_stat tells me that dn2id uses 4KB pages, has 433 internal pages, and 6378 leaf pages. The id2entry uses 16KB pages, has 52 internal pages, and 45912 leaf pages. In order to efficiently retrieve any single entry in this database, the cache should be at least

       (433+1) * 4KB + (52+1) * 16KB in size: 1736KB + 848KB =~ 2.5MB.

This doesn't take into account other library overhead, so this is even lower than the barest minimum. The default cache size, when nothing is configured, is only 256KB.

This 2.5MB number also doesn't take indexing into account. Each indexed attribute results in another database file. Earlier versions of OpenLDAP kept these index databases in Hash format, but from OpenLDAP 2.2 onward the index databases are in B-tree format so the same procedure can be used to calculate the necessary amount of cache for each index database.

For example, if your only index is for the objectClass attribute and db_stat reveals that objectClass.bdb has 339 internal pages and uses 4096 byte pages, the additional cache needed for just this attribute index is

       (339+1) * 4KB =~ 1.3MB.

With only this index enabled, I'd figure at least a 4MB cache for this backend. (Of course you're using a single cache shared among all of the database files, so the cache pages will most likely get used for something other than what you accounted for, but this gives you a fighting chance.)

With this 4MB cache I can slapcat this entire database on my 1.3GHz PIII in 1 minute, 40 seconds. With the cache doubled to 8MB, it still takes the same 1:40s. Once you've got enough cache to fit the B-tree internal pages, increasing it further won't have any effect until the cache really is large enough to hold 100% of the data pages. I don't have enough free RAM to hold all the 800MB id2entry data, so 4MB is good enough.

With back-bdb and back-hdb you can use "db_stat -m" to check how well the database cache is performing.

For more information on db_stat: http://www.oracle.com/technology/documentation/berkeley-db/db/utility/db_stat.html

21.4.2. slapd(8) Entry Cache (cachesize)

The slapd(8) entry cache operates on decoded entries. The rationale - entries in the entry cache can be used directly, giving the fastest response. If an entry isn't in the entry cache but can be extracted from the BDB page cache, that will avoid an I/O but it will still require parsing, so this will be slower.

If the entry is in neither cache then BDB will have to flush some of its current cached pages and bring in the needed pages, resulting in a couple of expensive I/Os as well as parsing.

The most optimal value is of course, the entire number of entries in the database. However, most directory servers don't consistently serve out their entire database, so setting this to a lesser number that more closely matches the believed working set of data is sufficient. This is the second most important parameter for the DB.

As far as balancing the entry cache vs the BDB cache - parsed entries in memory are generally about twice as large as they are on disk.

As we have already mentioned, not having a proper database cache size will cause performance issues. These issues are not an indication of corruption occurring in the database. It is merely the fact that the cache is thrashing itself that causes performance/response time to slowdown.

21.4.3. IDL Cache (idlcachesize)

Each IDL holds the search results from a given query, so the IDL cache will end up holding the most frequently requested search results. For back-bdb, it is generally recommended to match the "cachesize" setting. For back-hdb, it is generally recommended to be 3x"cachesize".

{NOTE: The idlcachesize setting directly affects search performance}

21.5. slapd(8) Threads

slapd(8) can process requests via a configurable number of threads, which in turn affects the in/out rate of connections.

This value should generally be a function of the number of "real" cores on the system, for example on a server with 2 CPUs with one core each, set this to 8, or 4 threads per real core. This is a "read" maximized value. The more threads that are configured per core, the slower slapd(8) responds for "read" operations. On the flip side, it appears to handle write operations faster in a heavy write/low read scenario.

The upper bound for good read performance appears to be 16 threads (which also happens to be the default setting).


22. Troubleshooting

If you're having trouble using OpenLDAP, get onto the OpenLDAP-Software mailing list, or:

Chances are the problem has been solved and explained in detail many times before.

22.1. User or Software errors?

More often than not, an error is caused by a configuration problem or a misunderstanding of what you are trying to implement and/or achieve.

We will now attempt to discuss common user errors.

22.2. Checklist

The following checklist can help track down your problem. Please try to use if before posting to the list, or in the rare circumstances of reporting a bug.

  1. Use the slaptest tool to verify configurations before starting slapd
     
  2. Verify that slapd is listening to the specified port(s) (389 and 636, generally) before trying the ldapsearch
     
  3. Can you issue an ldapsearch?
     
  4. If not, have you enabled complex ACLs without fully understanding them?
     
  5. Do you have a system wide LDAP setting pointing to the wrong LDAP Directory?
     
  6. Are you using TLS?
     
  7. Have your certificates expired?

22.3. OpenLDAP Bugs

Sometimes you may encounter an actual OpenLDAP bug, in which case please visit our Issue Tracking system http://www.openldap.org/its/ and report it. However, make sure it's not already a known bug or a common user problem.


Note: Our Issue Tracking system is NOT for OpenLDAP Support, please join our mailing Lists: http://www.openldap.org/lists/ for that.

The information you should provide in your bug report is discussed in our FAQ-O-MATIC at http://www.openldap.org/faq/data/cache/59.html

22.4. 3rd party software error

The OpenLDAP Project only supports OpenLDAP software.

You may however seek commercial support (http://www.openldap.org/support/) or join the general LDAP forum for non-commercial discussions and information relating to LDAP at: http://www.umich.edu/~dirsvcs/ldap/mailinglist.html

22.5. How to contact the OpenLDAP Project

22.6. How to present your problem

22.7. Debugging slapd(8)

After reading through the above sections and before e-mailing the OpenLDAP lists, you might want to try out some of the following to track down the cause of your problems:

22.8. Commercial Support

The firms listed at http://www.openldap.org/support/ offer technical support services catering to OpenLDAP community.

The listing of any given firm should not be viewed as an endorsement or recommendation of any kind, nor as otherwise indicating there exists a business relationship or an affiliation between any listed firm and the OpenLDAP Foundation or the OpenLDAP Project or its contributors.


A. Changes Since Previous Release

The following sections attempt to summarize the new features and changes in OpenLDAP software since the 2.3.x release and the OpenLDAP Admin Guide.

A.1. New Guide Sections

In order to make the Admin Guide more thorough and cover the majority of questions asked on the OpenLDAP mailing lists and scenarios discussed there, we have added the following new sections:

Also, the table of contents is now 3 levels deep to ease navigation.

A.2. New Features and Enhancements in 2.4

A.2.1. Better cn=config functionality

There is a new slapd-config(5) manpage for the cn=config backend. The original design called for auto-renaming of config entries when you insert or delete entries with ordered names, but that was not implemented in 2.3. It is now in 2.4. This means, e.g., if you have

   olcDatabase={1}bdb,cn=config
   olcSuffix: dc=example,dc=com

and you want to add a new subordinate, now you can ldapadd:

   olcDatabase={1}bdb,cn=config
   olcSuffix: dc=foo,dc=example,dc=com

This will insert a new BDB database in slot 1 and bump all following databases down one, so the original BDB database will now be named:

   olcDatabase={2}bdb,cn=config
   olcSuffix: dc=example,dc=com

A.2.2. Better cn=schema functionality

In 2.3 you were only able to add new schema elements, not delete or modify existing elements. In 2.4 you can modify schema at will. (Except for the hardcoded system schema, of course.)

A.2.3. More sophisticated Syncrepl configurations

The original implementation of Syncrepl in OpenLDAP 2.2 was intended to support multiple consumers within the same database, but that feature never worked and was removed from OpenLDAP 2.3; you could only configure a single consumer in any database.

In 2.4 you can configure multiple consumers in a single database. The configuration possibilities here are quite complex and numerous. You can configure consumers over arbitrary subtrees of a database (disjoint or overlapping). Any portion of the database may in turn be provided to other consumers using the Syncprov overlay. The Syncprov overlay works with any number of consumers over a single database or over arbitrarily many glued databases.

A.2.4. N-Way Multimaster Replication

As a consequence of the work to support multiple consumer contexts, the syncrepl system now supports full N-Way multimaster replication with entry-level conflict resolution. There are some important constraints, of course: In order to maintain consistent results across all servers, you must maintain tightly synchronized clocks across all participating servers (e.g., you must use NTP on all servers).

The entryCSNs used for replication now record timestamps with microsecond resolution, instead of just seconds. The delta-syncrepl code has not been updated to support multimaster usage yet, that will come later in the 2.4 cycle.

A.2.5. Replicating slapd Configuration (syncrepl and cn=config)

Syncrepl was explicitly disabled on cn=config in 2.3. It is now fully supported in 2.4; you can use syncrepl to replicate an entire server configuration from one server to arbitrarily many other servers. It's possible to clone an entire running slapd using just a small (less than 10 lines) seed configuration, or you can just replicate the schema subtrees, etc. Tests 049 and 050 in the test suite provide working examples of these capabilities.

A.2.6. Push-Mode Replication

In 2.3 you could configure syncrepl as a full push-mode replicator by using it in conjunction with a back-ldap pointed at the target server. But because the back-ldap database needs to have a suffix corresponding to the target's suffix, you could only configure one instance per slapd.

In 2.4 you can define a database to be "hidden", which means that its suffix is ignored when checking for name collisions, and the database will never be used to answer requests received by the frontend. Using this "hidden" database feature allows you to configure multiple databases with the same suffix, allowing you to set up multiple back-ldap instances for pushing replication of a single database to multiple targets. There may be other uses for hidden databases as well (e.g., using a syncrepl consumer to maintain a *local* mirror of a database on a separate filesystem).

A.2.7. More extensive TLS configuration control

In 2.3, the TLS configuration in slapd was only used by the slapd listeners. For outbound connections used by e.g. back-ldap or syncrepl their TLS parameters came from the system's ldap.conf file.

In 2.4 all of these sessions inherit their settings from the main slapd configuration, but settings can be individually overridden on a per-config-item basis. This is particularly helpful if you use certificate-based authentication and need to use a different client certificate for different destinations.

A.2.8. Performance enhancements

Too many to list. Some notable changes - ldapadd used to be a couple of orders of magnitude slower than "slapadd -q". It's now at worst only about half the speed of slapadd -q. Some comparisons of all the 2.x OpenLDAP releases are available at http://www.openldap.org/pub/hyc/scale2007.pdf

That compared 2.0.27, 2.1.30, 2.2.30, 2.3.33, and CVS HEAD). Toward the latter end of the "Cached Search Performance" chart it gets hard to see the difference because the run times are so small, but the new code is about 25% faster than 2.3, which was about 20% faster than 2.2, which was about 100% faster than 2.1, which was about 100% faster than 2.0, in that particular search scenario. That test basically searched a 1.3GB DB of 380836 entries (all in the slapd entry cache) in under 1 second. i.e., on a 2.4GHz CPU with DDR400 ECC/Registered RAM we can search over 500 thousand entries per second. The search was on an unindexed attribute using a filter that would not match any entry, forcing slapd to examine every entry in the DB, testing the filter for a match.

Essentially the slapd entry cache in back-bdb/back-hdb is so efficient the search processing time is almost invisible; the runtime is limited only by the memory bandwidth of the machine. (The search data rate corresponds to about 3.5GB/sec; the memory bandwidth on the machine is only about 4GB/sec due to ECC and register latency.)

A.2.9. New overlays

A.2.10. New features in existing Overlays

A.2.11. New features in slapd

A.2.12. New features in libldap

A.2.13. New clients, tools and tool enhancements

A.2.14. New build options

A.3. Obsolete Features Removed From 2.4

These features were strongly deprecated in 2.3 and removed in 2.4.

A.3.1. Slurpd

Please read the Replication section as to why this is no longer in OpenLDAP

A.3.2. back-ldbm

back-ldbm was both slow and unreliable. Its byzantine indexing code was prone to spontaneous corruption, as were the underlying database libraries that were commonly used (e.g. GDBM or NDBM). back-bdb and back-hdb are superior in every aspect, with simplified indexing to avoid index corruption, fine-grained locking for greater concurrency, hierarchical caching for greater performance, streamlined on-disk format for greater efficiency and portability, and full transaction support for greater reliability.


B. Upgrading from 2.3.x

The following sections attempt to document the steps you will need to take in order to upgrade from the latest 2.3.x OpenLDAP version.

The normal upgrade procedure, as discussed in the Maintenance section, should of course still be followed prior to doing any of this.

B.1. cn=config olc* attributes

Quite a few olc* attributes have now become obsolete, if you see in your logs entries like below, just remove them from the relevant ldif file.

           olcReplicationInterval: value #0: <olcReplicationInterval> keyword is obsolete (ignored)

B.2. ACLs: searches require privileges on the search base

Search operations now require "search" privileges on the "entry" pseudo-attribute of the search base. While upgrading from 2.3.x, make sure your ACLs grant such privileges to all desired search bases.

For example, assuming you have the following ACL:

           access to dn.sub="ou=people,dc=example,dc=com" by * search

Searches using a base of "dc=example,dc=com" will only be allowed if you add the following ACL:

           access to dn.base="dc=example,dc=com" attrs=entry by * search


Note: The slapd.access(5) man page states that this requirement was introduced with OpenLDAP 2.3. However, it is the default behavior only since 2.4.

ADD MORE HERE


C. Common errors encountered when using OpenLDAP Software

The following sections attempt to summarize the most common causes of LDAP errors when using OpenLDAP

C.1. Common causes of LDAP errors

C.1.1. ldap_*: Can't contact LDAP server

The Can't contact LDAP server error is usually returned when the LDAP server cannot be contacted. This may occur for many reasons:

      telnet <host> <port>

replacing <host> and <port> with the hostname and the port the server is supposed to listen on.

C.1.2. ldap_*: No such object

The no such object error is generally returned when the target DN of the operation cannot be located. This section details reasons common to all operations. You should also look for answers specific to the operation (as indicated in the error message).

The most common reason for this error is non-existence of the named object. First, check for typos.

Also note that, by default, a new directory server holds no objects (except for a few system entries). So, if you are setting up a new directory server and get this message, it may simply be that you have yet to add the object you are trying to locate.

The error commonly occurs because a DN was not specified and a default was not properly configured.

If you have a suffix specified in slapd.conf eg.

      suffix "dc=example,dc=com"

You should use

      ldapsearch -b 'dc=example,dc=com' '(cn=jane*)'

to tell it where to start the search.

The -b should be specified for all LDAP commands unless you have an ldap.conf(5) default configured.

See ldapsearch(1), ldapmodify(1)

Also, slapadd(8) and its ancillary programs are very strict about the syntax of the LDIF file.

Some liberties in the LDIF file may result in an apparently successful creation of the database, but accessing some parts of it may be difficult.

One known common error in database creation is putting a blank line before the first entry in the LDIF file. There must be no leading blank lines in the LDIF file.

It is generally recommended that ldapadd(1) be used instead of slapadd(8) when adding new entries your directory. slapadd(8) should be used to bulk load entries known to be valid.

Another cause of this message is a referral ({SECT:Constructing a Distributed Directory Service}}) entry to an unpopulated directory.

Either remove the referral, or add a single record with the referral base DN to the empty directory.

This error may also occur when slapd is unable to access the contents of its database because of file permission problems. For instance, on a Red Hat Linux system, slapd runs as user 'ldap'. When slapadd is run as root to create a database from scratch, the contents of /var/lib/ldap are created with user and group root and with permission 600, making the contents inaccessible to the slapd server.

C.1.3. ldap_*: Can't chase referral

This is caused by the line

      referral        ldap://root.openldap.org

In slapd.conf, it was provided as an example for how to use referrals in the original file. However if your machine is not permanently connected to the Internet, it will fail to find the server, and hence produce an error message.

To resolve, just place a # in front of line and restart slapd or point it to an available ldap server.

See also: ldapadd(1), ldapmodify(1) and slapd.conf(5)

C.1.4. ldap_*: server is unwilling to perform

slapd will return an unwilling to perform error if the backend holding the target entry does not support the given operation.

The password backend is only willing to perform searches. It will return an unwilling to perform error for all other operations.

The shell backend is configurable and may support a limited subset of operations. Check for other errors indicating a shortage of resources required by the directory server. i.e. you may have a full disk etc

C.1.5. ldap_*: Insufficient access

This error occurs when server denies the operation due to insufficient access. This is usually caused by binding to a DN with insufficient privileges (or binding anonymously) to perform the operation.

You can bind as the rootdn/rootpw specified in slapd.conf(5) to gain full access. Otherwise, you must bind to an entry which has been granted the appropriate rights through access controls.

C.1.6. ldap_*: Invalid DN syntax

The target (or other) DN of the operation is invalid. This implies that either the string representation of the DN is not in the required form, one of the types in the attribute value assertions is not defined, or one of the values in the attribute value assertions does not conform to the appropriate syntax.

C.1.7. ldap_*: Referral hop limit exceeded

This error generally occurs when the client chases a referral which refers itself back to a server it already contacted. The server responds as it did before and the client loops. This loop is detected when the hop limit is exceeded.

This is most often caused through misconfiguration of the server's default referral. The default referral should not be itself:

That is, on ldap://myldap/ the default referral should not be ldap://myldap/ (or any hostname/ip which is equivalent to myldap).

C.1.8. ldap_*: operations error

In some versions of slapd(8), operationsError was returned instead of other.

C.1.9. ldap_*: other error

The other result code indicates an internal error has occurred. While the additional information provided with the result code might provide some hint as to the problem, often one will need to consult the server's log files.

C.1.10. ldap_add/modify: Invalid syntax

This error is reported when a value of an attribute does not conform to syntax restrictions. Additional information is commonly provided stating which value of which attribute was found to be invalid. Double check this value and other values (the server will only report the first error it finds).

Common causes include:

For certain syntax, like OBJECT IDENTIFIER (OID), this error can indicate that the OID descriptor (a "short name") provided is unrecognized. For instance, this error is returned if the objectClass value provided is unrecognized.

C.1.11. ldap_add/modify: Object class violation

This error is returned with the entry to be added or the entry as modified violates the object class schema rules. Normally additional information is returned the error detailing the violation. Some of these are detailed below.

Violations related to the entry's attributes:

      Attribute not allowed

A provided attribute is not allowed by the entry's object class(es).

      Missing required attribute

An attribute required by the entry's object class(es) was not provided.

Violations related to the entry's class(es):

      Entry has no objectClass attribute

The entry did not state which object classes it belonged to.

      Unrecognized objectClass

One (or more) of the listed objectClass values is not recognized.

      No structural object class provided

None of the listed objectClass values is structural.

      Invalid structural object class chain

Two or more structural objectClass values are not in same structural object class chain.

      Structural object class modification

Modify operation attempts to change the structural class of the entry.

      Instanstantiation of abstract objectClass.

An abstract class is not subordinate to any listed structural or auxiliary class.

      Invalid structural object class

Other structural object class problem.

      No structuralObjectClass operational attribute

This is commonly returned when a shadow server is provided an entry which does not contain the structuralObjectClass operational attribute.

Note that the above error messages as well as the above answer assumes basic knowledge of LDAP/X.500 schema.

C.1.12. ldap_add: No such object

The "ldap_add: No such object" error is commonly returned if parent of the entry being added does not exist. Add the parent entry first...

For example, if you are adding "cn=bob,dc=domain,dc=com" and you get:

      ldap_add: No such object

The entry "dc=domain,dc=com" likely doesn't exist. You can use ldapsearch to see if does exist:

      ldapsearch -b 'dc=domain,dc=com' -s base '(objectclass=*)'

If it doesn't, add it. See A Quick-Start Guide for assistance.


Note: if the entry being added is the same as database suffix, it's parent isn't required. i.e.: if your suffix is "dc=domain,dc=com", "dc=com" doesn't need to exist to add "dc=domain,dc=com".

This error will also occur if you try to add any entry that the server is not configured to hold.

For example, if your database suffix is "dc=domain,dc=com" and you attempt to add "dc=domain2,dc=com", "dc=com", "dc=domain,dc=org", "o=domain,c=us", or an other DN in the "dc=domain,dc=com" subtree, the server will return a "No such object" (or referral) error.

slapd(8) will generally return "no global superior knowledge" as additional information indicating its return noSuchObject instead of a referral as the server is not configured with knowledge of a global superior server.

C.1.13. ldap add: invalid structural object class chain

This particular error refers to the rule about STRUCTURAL objectclasses, which states that an object is of one STRUCTURAL class, the structural class of the object. The object is said to belong to this class, zero or more auxiliaries classes, and their super classes.

While all of these classes are commonly listed in the objectClass attribute of the entry, one of these classes is the structural object class of the entry. Thus, it is OK for an objectClass attribute to contain inetOrgPerson, organizationalPerson, and person because they inherit one from another to form a single super class chain. That is, inetOrgPerson SUPs organizationPerson SUPs person. On the other hand, it is invalid for both inetOrgPerson and account to be listed in objectClass as inetOrgPerson and account are not part of the same super class chain (unless some other class is also listed with is a subclass of both).

To resolve this problem, one must determine which class will better serve structural object class for the entry, adding this class to the objectClass attribute (if not already present), and remove any other structural class from the entry's objectClass attribute which is not a super class of the structural object class.

Which object class is better depends on the particulars of the situation. One generally should consult the documentation for the applications one is using for help in making the determination.

C.1.14. ldap_add: no structuralObjectClass operational attribute

ldapadd(1) may error:

      adding new entry "uid=XXX,ou=People,o=campus,c=ru"
        ldap_add: Internal (implementation specific) error (80)
           additional info: no structuralObjectClass operational attribute

when slapd(8) cannot determine, based upon the contents of the objectClass attribute, what the structural class of the object should be.

C.1.15. ldap_add/modify/rename: Naming violation

OpenLDAP's slapd checks for naming attributes and distinguished values consistency, according to RFC 4512.

Naming attributes are those attributeTypes that appear in an entry's RDN; distinguished values are the values of the naming attributes that appear in an entry's RDN, e.g, in

      cn=Someone+mail=someone@example.com,dc=example,dc=com

the naming attributes are cn and mail, and the distinguished values are Someone and someone@example.com.

OpenLDAP's slapd checks for consistency when:

Possible causes of error are:

                dn: dc=example,dc=com
                objectClass: organization
                o: Example
                # note: "dc: example" is missing
                dn: dc=example,dc=com
                objectClass: domain
                dc: foobar
                # note: "dc" is present, but the value is not "example"

In any case, make sure that the attributeType definition for the naming attributes contains an appropriate EQUALITY field; or that of the superior, if they are defined based on a superior attributeType (look at the SUP field). See RFC 4512 for details.

C.1.16. ldap_add/delete/modify/rename: no global superior knowledge

If the target entry name places is not within any of the databases the server is configured to hold and the server has no knowledge of a global superior, the server will indicate it is unwilling to perform the operation and provide the text "no global superior knowledge" as additional text.

Likely the entry name is incorrect, or the server is not properly configured to hold the named entry, or, in distributed directory environments, a default referral was not configured.

C.1.17. ldap_bind: Insufficient access

Current versions of slapd(8) requires that clients have authentication permission to attribute types used for authentication purposes before accessing them to perform the bind operation. As all bind operations are done anonymously (regardless of previous bind success), the auth access must be granted to anonymous.

In the example ACL below grants the following access:

All other access is denied.

        access to attr=userPassword
          by self =w
          by anonymous auth
        access *
          by self write
          by users read

C.1.18. ldap_bind: Invalid credentials

The error usually occurs when the credentials (password) provided does not match the userPassword held in entry you are binding to.

The error can also occur when the bind DN specified is not known to the server.

Check both! In addition to the cases mentioned above you should check if the server denied access to userPassword on selected parts of the directory. In fact, slapd always returns "Invalid credentials" in case of failed bind, regardless of the failure reason, since other return codes could reveal the validity of the user's name.

To debug access rules defined in slapd.conf, add "ACL" to log level.

C.1.19. ldap_bind: Protocol error

There error is generally occurs when the LDAP version requested by the client is not supported by the server.

The OpenLDAP Software 2.x server, by default, only accepts version 3 LDAP Bind requests but can be configured to accept a version 2 LDAP Bind request.


Note: The 2.x server expects LDAPv3 [RFC4510] to be used when the client requests version 3 and expects a limited LDAPv3 variant (basically, LDAPv3 syntax and semantics in an LDAPv2 PDUs) to be used when version 2 is expected.

This variant is also sometimes referred to as LDAPv2+, but differs from the U-Mich LDAP variant in a number of ways.

C.1.20. ldap_modify: cannot modify object class

This message is commonly returned when attempting to modify the objectClass attribute in a manner inconsistent with the LDAP/X.500 information model. In particular, it commonly occurs when one tries to change the structure of the object from one class to another, for instance, trying to change an 'apple' into a 'pear' or a 'fruit' into a 'pear'.

Such changes are disallowed by the slapd(8) in accordance with LDAP and X.500 restrictions.

C.1.21. ldap_sasl_interactive_bind_s: ...

If you intended to bind using a DN and password and get an error from ldap_sasl_interactive_bind_s, you likely forgot to provide a '-x' option to the command. By default, SASL authentication is used. '-x' is necessary to select "simple" authentication.

C.1.22. ldap_sasl_interactive_bind_s: No such Object

This indicates that LDAP SASL authentication function could not read the Root DSE. The error will occur when the server doesn't provide a root DSE. This may be due to access controls.

C.1.23. ldap_sasl_interactive_bind_s: No such attribute

This indicates that LDAP SASL authentication function could read the Root DSE but it contained no supportedSASLMechanism attribute.

The supportedSASLmechanism attribute lists mechanisms currently available. The list may be empty because none of the supported mechanisms are currently available. For example, EXTERNAL is listed only if the client has established its identity by authenticating at a lower level (e.g. TLS).


Note: the attribute may not be visible due to access controls


Note: SASL bind is the default for all OpenLDAP tools, e.g. ldapsearch(1), ldapmodify(1). To force use of "simple" bind, use the "-x" option. Use of "simple" bind is not recommended unless one has adequate confidentiality protection in place (e.g. TLS/SSL, IPSEC).

C.1.24. ldap_sasl_interactive_bind_s: Unknown authentication method

This indicates that none of the SASL authentication supported by the server are supported by the client, or that they are too weak or otherwise inappropriate for use by the client. Note that the default security options disallows the use of certain mechanisms such as ANONYMOUS and PLAIN (without TLS).


Note: SASL bind is the default for all OpenLDAP tools. To force use of "simple" bind, use the "-x" option. Use of "simple" bind is not recommended unless one has adequate confidentiality protection in place (e.g. TLS/SSL, IPSEC).

C.1.25. ldap_sasl_interactive_bind_s: Local error (82)

Apparently not having forward and reverse DNS entries for the LDAP server can result in this error.

C.1.26. ldap_search: Partial results and referral received

This error is returned with the server responses to an LDAPv2 search query with both results (zero or more matched entries) and references (referrals to other servers). See also: ldapsearch(1).

If the updatedn on the replica does not exist, a referral will be returned. It may do this as well if the ACL needs tweaking.

C.1.27. ldap_start_tls: Operations error

ldapsearch(1) and other tools will return

        ldap_start_tls: Operations error (1)
              additional info: TLS already started

When the user (though command line options and/or ldap.conf(5)) has requested TLS (SSL) be started twice. For instance, when specifying both "-H ldaps://server.do.main" and "-ZZ".

C.2. Other Errors

C.2.1. ber_get_next on fd X failed errno=34 (Numerical result out of range)

This slapd error generally indicates that the client sent a message that exceeded an administrative limit. See sockbuf_max_incoming and sockbuf_max_incoming_auth configuration directives in slapd.conf(5).

C.2.2. ber_get_next on fd X failed errno=11 (Resource temporarily unavailable)

This message is not indicative of abnormal behavior or error. It simply means that expected data is not yet available from the resource, in this context, a network socket. slapd(8) will process the data once it does becomes available.

C.2.3. daemon: socket() failed errno=97 (Address family not supported)

This message indicates that the operating system does not support one of the (protocol) address families which slapd(8) was configured to support. Most commonly, this occurs when slapd(8) was configured to support IPv6 yet the operating system kernel wasn't. In such cases, the message can be ignored.

C.2.4. GSSAPI: gss_acquire_cred: Miscellaneous failure; Permission denied;

This message means that slapd is not running as root and, thus, it cannot get its Kerberos 5 key from the keytab, usually file /etc/krb5.keytab.

A keytab file is used to store keys that are to be used by services or daemons that are started at boot time. It is very important that these secrets are kept beyond reach of intruders.

That's why the default keytab file is owned by root and protected from being read by others. Do not mess with these permissions, build a different keytab file for slapd instead, and make sure it is owned by the user that slapd runs as.

To do this, start kadmin, and enter the following commands:

     addprinc -randkey ldap/ldap.example.com@EXAMPLE.COM
     ktadd -k /etc/openldap/ldap.keytab ldap/ldap.example.com@EXAMPLE.COM

Then, on the shell, do:

     chown ldap:ldap /etc/openldap/ldap.keytab
     chmod 600 /etc/openldap/ldap.keytab

Now you have to tell slapd (well, actually tell the gssapi library in Kerberos 5 that is invoked by Cyrus SASL) where to find the new keytab. You do this by setting the environment variable KRB5_KTNAME like this:

     export KRB5_KTNAME="FILE:/etc/openldap/ldap.keytab"

Set that environment variable on the slapd start script (Red Hat users might find /etc/sysconfig/ldap a perfect place).

This only works if you are using MIT kerberos. It doesn't work with Heimdal, for instance.

In Heimdal there is a function gsskrb5_register_acceptor_identity() that sets the path of the keytab file you want to use. In Cyrus SASL 2 you can add

    keytab: /path/to/file

to your application's SASL config file to use this feature. This only works with Heimdal.

C.2.5. access from unknown denied

This related to TCP wrappers. See hosts_access(5) for more information. in the log file: "access from unknown denied" This related to TCP wrappers. See hosts_access(5) for more information. for example: add the line "slapd: .hosts.you.want.to.allow" in /etc/hosts.allow to get rid of the error.

C.2.6. ldap_read: want=# error=Resource temporarily unavailable

This message occurs normally. It means that pending data is not yet available from the resource, a network socket. slapd(8) will process the data once it becomes available.

C.2.7. `make test' fails

Some times, `make test' fails at the very first test with an obscure message like

    make test
    make[1]: Entering directory `/ldap_files/openldap-2.4.6/tests'
    make[2]: Entering directory `/ldap_files/openldap-2.4.6/tests'
    Initiating LDAP tests for BDB...
    Cleaning up test run directory leftover from previous run.
     Running ./scripts/all...
    >>>>> Executing all LDAP tests for bdb
    >>>>> Starting test000-rootdse ...
    running defines.sh
    Starting slapd on TCP/IP port 9011...
    Using ldapsearch to retrieve the root DSE...
    Waiting 5 seconds for slapd to start...
    ./scripts/test000-rootdse: line 40: 10607 Segmentation fault $SLAPD -f $CONF1 -h $URI1 -d $LVL $TIMING >$LOG1 2>&1
    Waiting 5 seconds for slapd to start...
    Waiting 5 seconds for slapd to start...
    Waiting 5 seconds for slapd to start...
    Waiting 5 seconds for slapd to start...
    Waiting 5 seconds for slapd to start...
    ./scripts/test000-rootdse: kill: (10607) - No such pid
    ldap_sasl_bind_s: Can't contact LDAP server (-1)
    >>>>> Test failed
    >>>>> ./scripts/test000-rootdse failed (exit 1)
    make[2]: *** [bdb-yes] Error 1
    make[2]: Leaving directory `/ldap_files/openldap-2.4.6/tests'
    make[1]: *** [test] Error 2
    make[1]: Leaving directory `/ldap_files/openldap-2.4.6/tests'
    make: *** [test] Error 2

or so. Usually, the five lines

Waiting 5 seconds for slapd to start...

indicate that slapd didn't start at all.

In tests/testrun/slapd.1.log there is a full log of what slapd wrote while trying to start. The log level can be increased by setting the environment variable SLAPD_DEBUG to the corresponding value; see loglevel in slapd.conf(5) for the meaning of log levels.

A typical reason for this behavior is a runtime link problem, i.e. slapd cannot find some dynamic libraries it was linked against. Try running ldd(1) on slapd (for those architectures that support runtime linking).

There might well be other reasons; the contents of the log file should help clarifying them.

Tests that fire up multiple instances of slapd typically log to tests/testrun/slapd.<n>.log, with a distinct <n> for each instance of slapd; list tests/testrun/ for possible values of <n>.

C.2.8. ldap_*: Internal (implementation specific) error (80) - additional info: entry index delete failed

This seems to be related with wrong ownership of the BDB's dir (/var/lib/ldap) and files. The files must be owned by the user that slapd runs as.

    chown -R ldap:ldap /var/lib/ldap

fixes it in Debian

C.2.9. ldap_sasl_interactive_bind_s: Can't contact LDAP server (-1)

Using SASL, when a client contacts LDAP server, the slapd service dies immediately and client gets an error :

     SASL/GSSAPI authentication started ldap_sasl_interactive_bind_s: Can't contact LDAP server (-1)

Then check the slapd service, it stopped.

This may come from incompatible of using different versions of BerkeleyDB for installing of SASL and installing of OpenLDAP. The problem arises in case of using multiple version of BerkeleyDB. Solution: - Check which version of BerkeleyDB when install Cyrus SASL.

Reinstall OpenLDAP with the version of BerkeleyDB above.


D. Recommended OpenLDAP Software Dependency Versions

This appendix details the recommended versions of the software that OpenLDAP depends on.

Please read the Prerequisite software section for more information on the following software dependencies.

D.1. Dependency Versions

Table 8.5: OpenLDAP Software Dependency Versions
Feature Software Version
 Transport Layer Security:    
   OpenSSL 0.9.7+
   GnuTLS 2.12.0
   MozNSS 3.12.9
 Simple Authentication and Security Layer  Cyrus SASL 2.1.21+
 Kerberos Authentication Service:    
   Heimdal Version
   MIT Kerberos Version
Database Software  Berkeley DB: 5.3
    Note: It is highly recommended to apply the patches from Oracle for a given release.
Threads:    
  POSIX pthreads Version
  Mach CThreads Version
TCP Wrappers Name Version


E. Real World OpenLDAP Deployments and Examples

Examples and discussions


F. OpenLDAP Software Contributions

The following sections attempt to summarize the various contributions in OpenLDAP software, as found in openldap_src/contrib

F.1. Client APIs

Intro and discuss

F.1.1. ldapc++

Intro and discuss

F.1.2. ldaptcl

Intro and discuss

F.2. Overlays

F.2.1. acl

Plugins that implement access rules. Currently only posixGroup, which implements access control based on posixGroup membership.

F.2.2. addpartial

Treat Add requests as Modify requests if the entry exists.

F.2.3. allop

Return operational attributes for root DSE even when not requested, since some clients expect this.

F.2.4. autogroup

Automated updates of group memberships.

F.2.5. comp_match

Component Matching rules (RFC 3687).

F.2.6. denyop

Deny selected operations, returning unwillingToPerform.

F.2.7. dsaschema

Permit loading DSA-specific schema, including operational attrs.

F.2.8. lastmod

Track the time of the last write operation to a database.

F.2.9. nops

Remove null operations, e.g. changing a value to same as before.

F.2.10. nssov

Handle NSS lookup requests through a local Unix Domain socket.

F.2.11. passwd

Support additional password mechanisms.

F.2.12. proxyOld

Proxy Authorization compatibility with obsolete internet-draft.

F.2.13. smbk5pwd

Make the PasswordModify Extended Operation update Kerberos keys and Samba password hashes as well as userPassword.

F.2.14. trace

Trace overlay invocation.

F.2.15. usn

Maintain usnCreated and usnChanged attrs similar to Microsoft AD.

F.3. Tools

Intro and discuss

F.3.1. Statistic Logging

statslog

F.4. SLAPI Plugins

Intro and discuss

F.4.1. addrdnvalues

More


G. Configuration File Examples

G.1. slapd.conf

G.2. ldap.conf

G.3. a-n-other.conf


H. LDAP Result Codes

For the purposes of this guide, we have incorporated the standard LDAP result codes from Appendix A. LDAP Result Codes of RFC4511, a copy of which can be found in doc/rfc of the OpenLDAP source code.

We have expanded the description of each error in relation to the OpenLDAP toolsets. LDAP extensions may introduce extension-specific result codes, which are not part of RFC4511. OpenLDAP returns the result codes related to extensions it implements. Their meaning is documented in the extension they are related to.

H.1. Non-Error Result Codes

These result codes (called "non-error" result codes) do not indicate an error condition:

        success (0),
        compareFalse (5),
        compareTrue (6),
        referral (10), and
        saslBindInProgress (14).

The success, compareTrue, and compareFalse result codes indicate successful completion (and, hence, are referred to as "successful" result codes).

The referral and saslBindInProgress result codes indicate the client needs to take additional action to complete the operation.

H.2. Result Codes

Existing LDAP result codes are described as follows:

H.3. success (0)

Indicates the successful completion of an operation.


Note: this code is not used with the Compare operation. See compareFalse (5) and compareTrue (6).

H.4. operationsError (1)

Indicates that the operation is not properly sequenced with relation to other operations (of same or different type).

For example, this code is returned if the client attempts to StartTLS (RFC4511 Section 4.14) while there are other uncompleted operations or if a TLS layer was already installed.

H.5. protocolError (2)

Indicates the server received data that is not well-formed.

For Bind operation only, this code is also used to indicate that the server does not support the requested protocol version.

For Extended operations only, this code is also used to indicate that the server does not support (by design or configuration) the Extended operation associated with the requestName.

For request operations specifying multiple controls, this may be used to indicate that the server cannot ignore the order of the controls as specified, or that the combination of the specified controls is invalid or unspecified.

H.6. timeLimitExceeded (3)

Indicates that the time limit specified by the client was exceeded before the operation could be completed.

H.7. sizeLimitExceeded (4)

Indicates that the size limit specified by the client was exceeded before the operation could be completed.

H.8. compareFalse (5)

Indicates that the Compare operation has successfully completed and the assertion has evaluated to FALSE or Undefined.

H.9. compareTrue (6)

Indicates that the Compare operation has successfully completed and the assertion has evaluated to TRUE.

H.10. authMethodNotSupported (7)

Indicates that the authentication method or mechanism is not supported.

H.11. strongerAuthRequired (8)

Indicates the server requires strong(er) authentication in order to complete the operation.

When used with the Notice of Disconnection operation, this code indicates that the server has detected that an established security association between the client and server has unexpectedly failed or been compromised.

H.12. referral (10)

Indicates that a referral needs to be chased to complete the operation (see RFC4511 Section 4.1.10).

H.13. adminLimitExceeded (11)

Indicates that an administrative limit has been exceeded.

H.14. unavailableCriticalExtension (12)

Indicates a critical control is unrecognized (see RFC4511 Section 4.1.11).

H.15. confidentialityRequired (13)

Indicates that data confidentiality protections are required.

H.16. saslBindInProgress (14)

Indicates the server requires the client to send a new bind request, with the same SASL mechanism, to continue the authentication process (see RFC4511 Section 4.2).

H.17. noSuchAttribute (16)

Indicates that the named entry does not contain the specified attribute or attribute value.

H.18. undefinedAttributeType (17)

Indicates that a request field contains an unrecognized attribute description.

H.19. inappropriateMatching (18)

Indicates that an attempt was made (e.g., in an assertion) to use a matching rule not defined for the attribute type concerned.

H.20. constraintViolation (19)

Indicates that the client supplied an attribute value that does not conform to the constraints placed upon it by the data model.

For example, this code is returned when multiple values are supplied to an attribute that has a SINGLE-VALUE constraint.

H.21. attributeOrValueExists (20)

Indicates that the client supplied an attribute or value to be added to an entry, but the attribute or value already exists.

H.22. invalidAttributeSyntax (21)

Indicates that a purported attribute value does not conform to the syntax of the attribute.

H.23. noSuchObject (32)

Indicates that the object does not exist in the DIT.

H.24. aliasProblem (33)

Indicates that an alias problem has occurred. For example, the code may used to indicate an alias has been dereferenced that names no object.

H.25. invalidDNSyntax (34)

Indicates that an LDAPDN or RelativeLDAPDN field (e.g., search base, target entry, ModifyDN newrdn, etc.) of a request does not conform to the required syntax or contains attribute values that do not conform to the syntax of the attribute's type.

H.26. aliasDereferencingProblem (36)

Indicates that a problem occurred while dereferencing an alias. Typically, an alias was encountered in a situation where it was not allowed or where access was denied.

H.27. inappropriateAuthentication (48)

Indicates the server requires the client that had attempted to bind anonymously or without supplying credentials to provide some form of credentials.

H.28. invalidCredentials (49)

Indicates that the provided credentials (e.g., the user's name and password) are invalid.

H.29. insufficientAccessRights (50)

Indicates that the client does not have sufficient access rights to perform the operation.

H.30. busy (51)

Indicates that the server is too busy to service the operation.

H.31. unavailable (52)

Indicates that the server is shutting down or a subsystem necessary to complete the operation is offline.

H.32. unwillingToPerform (53)

Indicates that the server is unwilling to perform the operation.

H.33. loopDetect (54)

Indicates that the server has detected an internal loop (e.g., while dereferencing aliases or chaining an operation).

H.34. namingViolation (64)

Indicates that the entry's name violates naming restrictions.

H.35. objectClassViolation (65)

Indicates that the entry violates object class restrictions.

H.36. notAllowedOnNonLeaf (66)

Indicates that the operation is inappropriately acting upon a non-leaf entry.

H.37. notAllowedOnRDN (67)

Indicates that the operation is inappropriately attempting to remove a value that forms the entry's relative distinguished name.

H.38. entryAlreadyExists (68)

Indicates that the request cannot be fulfilled (added, moved, or renamed) as the target entry already exists.

H.39. objectClassModsProhibited (69)

Indicates that an attempt to modify the object class(es) of an entry's 'objectClass' attribute is prohibited.

For example, this code is returned when a client attempts to modify the structural object class of an entry.

H.40. affectsMultipleDSAs (71)

Indicates that the operation cannot be performed as it would affect multiple servers (DSAs).

H.41. other (80)

Indicates the server has encountered an internal error.


I. Glossary

I.1. Terms

Term Definition
3DES Triple DES
ABNF Augmented Backus-Naur Form
ACDF Access Control Decision Function
ACE ASCII Compatible Encoding
ASCII American Standard Code for Information Interchange
ACID Atomicity, Consistency, Isolation, and Durability
ACI Access Control Information
ACL Access Control List
AES Advance Encryption Standard
ABI Application Binary Interface
API Application Program Interface
ASN.1 Abstract Syntax Notation - One
AVA Attribute Value Assertion
AuthcDN Authentication DN
AuthcId Authentication Identity
AuthzDN Authorization DN
AuthzId Authorization Identity
BCP Best Current Practice
BDB Berkeley DB (Backend)
BER Basic Encoding Rules
BNF Backus-Naur Form
C The C Programming Language
CA Certificate Authority
CER Canonical Encoding Rules
CLDAP Connection-less LDAP
CN Common Name
CRAM-MD5 SASL MD5 Challenge/Response Authentication Mechanism
CRL Certificate Revocation List
DAP Directory Access Protocol
DC Domain Component
DER Distinguished Encoding Rules
DES Data Encryption Standard
DIB Directory Information Base
DIGEST-MD5 SASL Digest MD5 Authentication Mechanism
DISP Directory Information Shadowing Protocol
DIT Directory Information Tree
DNS Domain Name System
DN Distinguished Name
DOP Directory Operational Binding Management Protocol
DSAIT DSA Information Tree
DSA Directory System Agent
DSE DSA-specific Entry
DSP Directory System Protocol
DS Draft Standard
DUA Directory User Agent
EXTERNAL SASL External Authentication Mechanism
FAQ Frequently Asked Questions
FTP File Transfer Protocol
FYI For Your Information
GSER Generic String Encoding Rules
GSS-API Generic Security Service Application Program Interface
GSSAPI SASL Kerberos V GSS-API Authentication Mechanism
HDB Hierarchical Database (Backend)
I-D Internet-Draft
IA5 International Alphabet 5
IDNA Internationalized Domain Names in Applications
IDN Internationalized Domain Name
ID Identifier
IDL Index Data Lookups
IP Internet Protocol
IPC Inter-process communication
IPsec Internet Protocol Security
IPv4 Internet Protocol, version 4
IPv6 Internet Protocol, version 6
ITS Issue Tracking System
JPEG Joint Photographic Experts Group
Kerberos Kerberos Authentication Service
LBER Lightweight BER
LDAP Lightweight Directory Access Protocol
LDAP Sync LDAP Content Synchronization
LDAPv3 LDAP, version 3
LDIF LDAP Data Interchange Format
LMDB Lightning Memory-Mapped Database
MD5 Message Digest 5
MDB Memory-Mapped Database (Backend)
MIB Management Information Base
MODDN Modify DN
MODRDN Modify RDN
NSSR Non-specific Subordinate Reference
OID Object Identifier
OSI Open Systems Interconnect
OTP One Time Password
PDU Protocol Data Unit
PEM Privacy Enhanced eMail
PEN Private Enterprise Number
PKCS Public Key Cryptosystem
PKI Public Key Infrastructure
PKIX Public Key Infrastructure (X.509)
PLAIN SASL Plaintext Password Authentication Mechanism
POSIX Portable Operating System Interface
PS Proposed Standard
RDN Relative Distinguished Name
RFC Request for Comments
RPC Remote Procedure Call
RXER Robust XML Encoding Rules
SASL Simple Authentication and Security Layer
SDF Simple Document Format
SDSE Shadowed DSE
SHA1 Secure Hash Algorithm 1
SLAPD Standalone LDAP Daemon
SLURPD Standalone LDAP Update Replication Daemon
SMTP Simple Mail Transfer Protocol
SNMP Simple Network Management Protocol
SQL Structured Query Language
SRP Secure Remote Password
SSF Security Strength Factor
SSL Secure Socket Layer
STD Internet Standard
TCP Transmission Control Protocol
TLS Transport Layer Security
UCS Universal Multiple-Octet Coded Character Set
UDP User Datagram Protocol
UID User Identifier
Unicode The Unicode Standard
UNIX Unix
URI Uniform Resource Identifier
URL Uniform Resource Locator
URN Uniform Resource Name
UTF-8 8-bit UCS/Unicode Transformation Format
UTR Unicode Technical Report
UUID Universally Unique Identifier
WWW World Wide Web
X.500 X.500 Directory Services
X.509 X.509 Public Key and Attribute Certificate Frameworks
XED XML Enabled Directory
XER XML Encoding Rules
XML Extensible Markup Language
syncrepl LDAP Sync-based Replication

I.2. Related Organizations

Name Long Jump
ANSI American National Standards Institute http://www.ansi.org/
BSI British Standards Institute http://www.bsi-global.com/
COSINE Co-operation and Open Systems Interconnection in Europe  
CPAN Comprehensive Perl Archive Network http://cpan.org/
Cyrus Project Cyrus http://cyrusimap.web.cmu.edu/
FSF Free Software Foundation http://www.fsf.org/
GNU GNU Not Unix Project http://www.gnu.org/
IAB Internet Architecture Board http://www.iab.org/
IANA Internet Assigned Numbers Authority http://www.iana.org/
IEEE Institute of Electrical and Electronics Engineers http://www.ieee.org
IESG Internet Engineering Steering Group http://www.ietf.org/iesg/
IETF Internet Engineering Task Force http://www.ietf.org/
IRTF Internet Research Task Force http://www.irtf.org/
ISO International Standards Organisation http://www.iso.org/
ISOC Internet Society http://www.isoc.org/
ITU International Telephone Union http://www.itu.int/
OLF OpenLDAP Foundation http://www.openldap.org/foundation/
OLP OpenLDAP Project http://www.openldap.org/project/
OpenSSL OpenSSL Project http://www.openssl.org/
RFC Editor RFC Editor http://www.rfc-editor.org/
Oracle Oracle Corporation http://www.oracle.com/
UM University of Michigan http://www.umich.edu/
UMLDAP University of Michigan LDAP Team http://www.umich.edu/~dirsvcs/ldap/ldap.html

I.3. Related Products

Name Jump
SDF http://search.cpan.org/src/IANC/sdf-2.001/doc/catalog.html
Berkeley DB http://www.oracle.com/database/berkeley-db/db/index.html
Cyrus http://cyrusimap.web.cmu.edu/generalinfo.html
Cyrus SASL http://asg.web.cmu.edu/sasl/sasl-library.html
Git http://git-scm.com/
GNU http://www.gnu.org/software/
GnuTLS http://www.gnu.org/software/gnutls/
Heimdal http://www.pdc.kth.se/heimdal/
JLDAP http://www.openldap.org/jldap/
MIT Kerberos http://web.mit.edu/kerberos/www/
MozNSS http://developer.mozilla.org/en/NSS
OpenLDAP http://www.openldap.org/
OpenLDAP FAQ http://www.openldap.org/faq/
OpenLDAP ITS http://www.openldap.org/its/
OpenLDAP Software http://www.openldap.org/software/
OpenSSL http://www.openssl.org/
Perl http://www.perl.org/
UMLDAP http://www.umich.edu/~dirsvcs/ldap/ldap.html

I.4. References

Reference Document Status Jump
UM-GUIDE The SLAPD and SLURPD Administrators Guide O http://www.umich.edu/~dirsvcs/ldap/doc/guides/slapd/guide.pdf
RFC2079 Definition of an X.500 Attribute Type and an Object Class to Hold Uniform Resource Identifers PS http://www.rfc-editor.org/rfc/rfc2079.txt
RFC2296 Use of Language Codes in LDAP PS http://www.rfc-editor.org/rfc/rfc2296.txt
RFC2307 An Approach for Using LDAP as a Network Information Service X http://www.rfc-editor.org/rfc/rfc2307.txt
RFC2589 Lightweight Directory Access Protocol (v3): Extensions for Dynamic Directory Services PS http://www.rfc-editor.org/rfc/rfc2589.txt
RFC2798 Definition of the inetOrgPerson LDAP Object Class I http://www.rfc-editor.org/rfc/rfc2798.txt
RFC2831 Using Digest Authentication as a SASL Mechanism PS http://www.rfc-editor.org/rfc/rfc2831.txt
RFC2849 The LDAP Data Interchange Format PS http://www.rfc-editor.org/rfc/rfc2849.txt
RFC3088 OpenLDAP Root Service X http://www.rfc-editor.org/rfc/rfc3088.txt
RFC3296 Named Subordinate References in LDAP PS http://www.rfc-editor.org/rfc/rfc3296.txt
RFC3384 Lightweight Directory Access Protocol (version 3) Replication Requirements I http://www.rfc-editor.org/rfc/rfc3384.txt
RFC3494 Lightweight Directory Access Protocol version 2 (LDAPv2) to Historic Status I http://www.rfc-editor.org/rfc/rfc3494.txt
RFC4013 SASLprep: Stringprep Profile for User Names and Passwords PS http://www.rfc-editor.org/rfc/rfc4013.txt
RFC4346 The Transport Layer Security (TLS) Protocol, Version 1.1 PS http://www.rfc-editor.org/rfc/rfc4346.txt
RFC4422 Simple Authentication and Security Layer (SASL) PS http://www.rfc-editor.org/rfc/rfc4422.txt
RFC4510 Lightweight Directory Access Protocol (LDAP): Technical Specification Roadmap PS http://www.rfc-editor.org/rfc/rfc4510.txt
RFC4511 Lightweight Directory Access Protocol (LDAP): The Protocol PS http://www.rfc-editor.org/rfc/rfc4511.txt
RFC4512 Lightweight Directory Access Protocol (LDAP): Directory Information Models PS http://www.rfc-editor.org/rfc/rfc4512.txt
RFC4513 Lightweight Directory Access Protocol (LDAP): Authentication Methods and Security Mechanisms PS http://www.rfc-editor.org/rfc/rfc4513.txt
RFC4514 Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names PS http://www.rfc-editor.org/rfc/rfc4514.txt
RFC4515 Lightweight Directory Access Protocol (LDAP): String Representation of Search Filters PS http://www.rfc-editor.org/rfc/rfc4515.txt
RFC4516 Lightweight Directory Access Protocol (LDAP): Uniform Resource Locator PS http://www.rfc-editor.org/rfc/rfc4516.txt
RFC4517 Lightweight Directory Access Protocol (LDAP): Syntaxes and Matching Rules PS http://www.rfc-editor.org/rfc/rfc4517.txt
RFC4518 Lightweight Directory Access Protocol (LDAP): Internationalized String Preparation PS http://www.rfc-editor.org/rfc/rfc4518.txt
RFC4519 Lightweight Directory Access Protocol (LDAP): Schema for User Applications PS http://www.rfc-editor.org/rfc/rfc4519.txt
RFC4520 IANA Considerations for LDAP BCP http://www.rfc-editor.org/rfc/rfc4520.txt
RFC4533 The Lightweight Directory Access Protocol (LDAP) Content Synchronization Operation X http://www.rfc-editor.org/rfc/rfc4533.txt
Chu-LDAPI Using LDAP Over IPC Mechanisms ID http://tools.ietf.org/html/draft-chu-ldap-ldapi-00


J. Generic configure Instructions

Basic Installation
==================

   These are generic installation instructions.

   The `configure' shell script attempts to guess correct values for
various system-dependent variables used during compilation.  It uses
those values to create a `Makefile' in each directory of the package.
It may also create one or more `.h' files containing system-dependent
definitions.  Finally, it creates a shell script `config.status' that
you can run in the future to recreate the current configuration, a file
`config.cache' that saves the results of its tests to speed up
reconfiguring, and a file `config.log' containing compiler output
(useful mainly for debugging `configure').

   If you need to do unusual things to compile the package, please try
to figure out how `configure' could check whether to do them, and mail
diffs or instructions to the address given in the `README' so they can
be considered for the next release.  If at some point `config.cache'
contains results you don't want to keep, you may remove or edit it.

   The file `configure.in' is used to create `configure' by a program
called `autoconf'.  You only need `configure.in' if you want to change
it or regenerate `configure' using a newer version of `autoconf'.

The simplest way to compile this package is:

  1. `cd' to the directory containing the package's source code and type
     `./configure' to configure the package for your system.  If you're
     using `csh' on an old version of System V, you might need to type
     `sh ./configure' instead to prevent `csh' from trying to execute
     `configure' itself.

     Running `configure' takes awhile.  While running, it prints some
     messages telling which features it is checking for.

  2. Type `make' to compile the package.

  3. Optionally, type `make check' to run any self-tests that come with
     the package.

  4. Type `make install' to install the programs and any data files and
     documentation.

  5. You can remove the program binaries and object files from the
     source code directory by typing `make clean'.  To also remove the
     files that `configure' created (so you can compile the package for
     a different kind of computer), type `make distclean'.  There is
     also a `make maintainer-clean' target, but that is intended mainly
     for the package's developers.  If you use it, you may have to get
     all sorts of other programs in order to regenerate files that came
     with the distribution.

Compilers and Options
=====================

   Some systems require unusual options for compilation or linking that
the `configure' script does not know about.  You can give `configure'
initial values for variables by setting them in the environment.  Using
a Bourne-compatible shell, you can do that on the command line like
this:
     CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure

Or on systems that have the `env' program, you can do it like this:
     env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure

Compiling For Multiple Architectures
====================================

   You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory.  To do this, you must use a version of `make' that
supports the `VPATH' variable, such as GNU `make'.  `cd' to the
directory where you want the object files and executables to go and run
the `configure' script.  `configure' automatically checks for the
source code in the directory that `configure' is in and in `..'.

   If you have to use a `make' that does not supports the `VPATH'
variable, you have to compile the package for one architecture at a time
in the source code directory.  After you have installed the package for
one architecture, use `make distclean' before reconfiguring for another
architecture.

Installation Names
==================

   By default, `make install' will install the package's files in
`/usr/local/bin', `/usr/local/man', etc.  You can specify an
installation prefix other than `/usr/local' by giving `configure' the
option `--prefix=PATH'.

   You can specify separate installation prefixes for
architecture-specific files and architecture-independent files.  If you
give `configure' the option `--exec-prefix=PATH', the package will use
PATH as the prefix for installing programs and libraries.
Documentation and other data files will still use the regular prefix.

   In addition, if you use an unusual directory layout you can give
options like `--bindir=PATH' to specify different values for particular
kinds of files.  Run `configure --help' for a list of the directories
you can set and what kinds of files go in them.

   If the package supports it, you can cause programs to be installed
with an extra prefix or suffix on their names by giving `configure' the
option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.

Optional Features
=================

   Some packages pay attention to `--enable-FEATURE' options to
`configure', where FEATURE indicates an optional part of the package.
They may also pay attention to `--with-PACKAGE' options, where PACKAGE
is something like `gnu-as' or `x' (for the X Window System).  The
`README' should mention any `--enable-' and `--with-' options that the
package recognizes.

   For packages that use the X Window System, `configure' can usually
find the X include and library files automatically, but if it doesn't,
you can use the `configure' options `--x-includes=DIR' and
`--x-libraries=DIR' to specify their locations.

Specifying the System Type
==========================

   There may be some features `configure' can not figure out
automatically, but needs to determine by the type of host the package
will run on.  Usually `configure' can figure that out, but if it prints
a message saying it can not guess the host type, give it the
`--host=TYPE' option.  TYPE can either be a short name for the system
type, such as `sun4', or a canonical name with three fields:
     CPU-COMPANY-SYSTEM

See the file `config.sub' for the possible values of each field.  If
`config.sub' isn't included in this package, then this package doesn't
need to know the host type.

   If you are building compiler tools for cross-compiling, you can also
use the `--target=TYPE' option to select the type of system they will
produce code for and the `--build=TYPE' option to select the type of
system on which you are compiling the package.

Sharing Defaults
================

   If you want to set default values for `configure' scripts to share,
you can create a site shell script called `config.site' that gives
default values for variables like `CC', `cache_file', and `prefix'.
`configure' looks for `PREFIX/share/config.site' if it exists, then
`PREFIX/etc/config.site' if it exists.  Or, you can set the
`CONFIG_SITE' environment variable to the location of the site script.
A warning: not all `configure' scripts look for a site script.

Operation Controls
==================

   `configure' recognizes the following options to control how it
operates.

`--cache-file=FILE'
     Use and save the results of the tests in FILE instead of
     `./config.cache'.  Set FILE to `/dev/null' to disable caching, for
     debugging `configure'.

`--help'
     Print a summary of the options to `configure', and exit.

`--quiet'
`--silent'
`-q'
     Do not print messages saying which checks are being made.  To
     suppress all normal output, redirect it to `/dev/null' (any error
     messages will still be shown).

`--srcdir=DIR'
     Look for the package's source code in directory DIR.  Usually
     `configure' can determine that directory automatically.

`--version'
     Print the version of Autoconf used to generate the `configure'
     script, and exit.

`configure' also accepts some other, not widely useful, options.


K. OpenLDAP Software Copyright Notices

K.1. OpenLDAP Copyright Notice

Copyright 1998-2012 The OpenLDAP Foundation.
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted only as authorized by the OpenLDAP Public License.

A copy of this license is available in file LICENSE in the top-level directory of the distribution or, alternatively, at <http://www.OpenLDAP.org/license.html>.

OpenLDAP is a registered trademark of the OpenLDAP Foundation.

Individual files and/or contributed packages may be copyright by other parties and their use subject to additional restrictions.

This work is derived from the University of Michigan LDAP v3.3 distribution. Information concerning this software is available at <http://www.umich.edu/~dirsvcs/ldap/ldap.html>.

This work also contains materials derived from public sources.

Additional information about OpenLDAP software can be obtained at <http://www.OpenLDAP.org/>.

K.2. Additional Copyright Notices

Portions Copyright 1998-2012 Kurt D. Zeilenga.
Portions Copyright 1998-2006 Net Boolean Incorporated.
Portions Copyright 2001-2006 IBM Corporation.
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted only as authorized by the OpenLDAP Public License.

Portions Copyright 1999-2008 Howard Y.H. Chu.
Portions Copyright 1999-2008 Symas Corporation.
Portions Copyright 1998-2003 Hallvard B. Furuseth.
Portions Copyright 2007-2011 Gavin Henry.
Portions Copyright 2007-2011 Suretec Systems Limited.
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that this notice is preserved. The names of the copyright holders may not be used to endorse or promote products derived from this software without their specific prior written permission. This software is provided ``as is'' without express or implied warranty.

K.3. University of Michigan Copyright Notice

Portions Copyright 1992-1996 Regents of the University of Michigan.
All rights reserved.

Redistribution and use in source and binary forms are permitted provided that this notice is preserved and that due credit is given to the University of Michigan at Ann Arbor. The name of the University may not be used to endorse or promote products derived from this software without specific prior written permission. This software is provided ``as is'' without express or implied warranty.


L. OpenLDAP Public License

The OpenLDAP Public License
  Version 2.8, 17 August 2003

Redistribution and use of this software and associated documentation
("Software"), with or without modification, are permitted provided
that the following conditions are met:

1. Redistributions in source form must retain copyright statements
   and notices,

2. Redistributions in binary form must reproduce applicable copyright
   statements and notices, this list of conditions, and the following
   disclaimer in the documentation and/or other materials provided
   with the distribution, and

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