6. The slapd Configuration File

Once the software has been built and installed, you are ready to configure slapd(8) for use at your site. The slapd runtime configuration is primarily accomplished through the slapd.conf(5) file, 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). This chapter describes the general format of the slapd.conf(5) configuration file, followed by a detailed description of commonly used config file directives.


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 white space, 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 white space. If an argument contains white space, 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 The access Configuration Directive section of this chapter for a summary of 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 <integer>

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 are additive. To display what numbers correspond to what kind of debugging, invoke slapd with -? or consult the table below. The possible values for <integer> are:

Table 6.1: Debugging Levels
Level Description
-1 enable all debugging
0 no debugging
1 trace function calls
2 debug packet handling
4 heavy trace debugging
8 connection management
16 print out packets sent and received
32 search filter processing
64 configuration file processing
128 access control list processing
256 stats log connections/operations/results
512 stats log entries sent
1024 print communication with shell backends
2048 print entry parsing debugging

Example:

 loglevel -1

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

Default:

 loglevel 256

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

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

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 5.2: 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. 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

6.2.3.3. 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.

6.2.3.4. 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.

6.2.3.5. 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.

6.2.3.6. 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>]

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 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. 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.

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 syncrepl replication mechanism is supported by the two primary database backends: back-bdb and back-hdb.

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

6.2.3.7. 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. The access Configuration Directive

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.

6.3.1. 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 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=.*"

6.3.2. 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 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 spoofed, the domain factor should not be avoided.

6.3.3. 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.

6.3.4. 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 file. For each entry, access controls provided in the database which holds the entry (or the first database if not held in any database) apply first, followed by the global access directives. 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.

6.3.5. 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:

        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 and every access list ends with an implicit access to * by * none directive.

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.


6.4. 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,uid 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. As this is the first database, the controls also apply to entries not held in any database (such as the Root DSE). 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