[Date Prev][Date Next]
[Chronological]
[Thread]
[Top]
Update to draft-ietf-ldapbis-protocol-01.txt
I-D Editor,
Please publish the attached I-D -- draft-ietf-ldapbis-protocol-02.txt as an update to draft-ietf-ldapbis-protocol-01.txt.
This is a working item of the LDAPBIS working group.
LDAPBIS Group,
Changes for this revision are in Appendix B and repeated here.
Changes made to draft-ietf-ldapbis-protocol-01.txt:
B.8 Section 3.4
- Reworded text surrounding subschemaSubentry to reflect that it is
a single-valued attribute that holds the schema for the root DSE.
Also noted that if the server masters entries that use differing
schema, each entry's subschemaSubentry attribute must be
interrogated. This may change as further fine-tuning is done to
the data model.
B.9 Section 4.1.12
- Specified that the criticality field is only used for requests and
not for unbind or abandon. Noted that it is ignored for all other
operations.
B.10 Section 4.2
- Noted that Server behavior is undefined when the name is a null
value, simple authentication is used, and a password is specified.
B.11 Section 4.2.(various)
- Changed "unauthenticated" to "anonymous" and "DN" and "LDAPDN" to
"name"
B.12 Section 4.2.2
- Changed "there is no authentication or encryption being performed
by a lower layer" to "the underlying transport service cannot
guarantee confidentiality"
B.13 Section 4.5.2
- Removed all mention of ExtendedResponse due to lack of
implementation.
Thanks. Jim
Internet-Draft Editor: J. Sermersheim
Intended Category: Standard Track Novell, Inc
Document: draft-ietf-ldapbis-protocol-02.txt July 2001
Obsoletes: RFC 2251
Lightweight Directory Access Protocol (v3)
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC2026].
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited. Technical discussion of this
document will take place on the IETF LDAP Revision Working Group
(LDAPbis) mailing list <ietf-ldapbis@openldap.org>. Please send
editorial comments directly to the editor <jimse@novell.com>.
Table of Contents
1. Status of this Memo..............................................1
2. Abstract.........................................................3
3. Models...........................................................4
3.1. Protocol Model.................................................4
3.2. Data Model.....................................................5
3.2.1. Attributes of Entries........................................5
3.2.2. Subschema Entries and Subentries.............................6
3.3. Relationship to X.500..........................................7
3.4. Server-specific Data Requirements..............................7
4. Elements of Protocol.............................................8
4.1. Common Elements................................................9
4.1.1. Message Envelope.............................................9
4.1.1.1. Message ID................................................10
4.1.2. String Types................................................10
4.1.3. Distinguished Name and Relative Distinguished Name..........11
4.1.4. Attribute Type..............................................11
4.1.5. Attribute Description.......................................12
4.1.5.1. Binary Option.............................................12
4.1.6. Attribute Value.............................................13
Sermersheim Internet-Draft - Expires Jan 2002 Page 1
Lightweight Directory Access Protocol Version 3
4.1.7. Attribute Value Assertion...................................13
4.1.8. Attribute...................................................14
4.1.9. Matching Rule Identifier....................................14
4.1.10. Result Message.............................................15
4.1.11. Referral...................................................16
4.1.12. Controls...................................................17
4.2. Bind Operation................................................18
4.2.1. Sequencing of the Bind Request..............................19
4.2.2. Authentication and Other Security Services..................20
4.2.3. Bind Response...............................................21
4.3. Unbind Operation..............................................22
4.4. Unsolicited Notification......................................22
4.4.1. Notice of Disconnection.....................................22
4.5. Search Operation..............................................23
4.5.1. Search Request..............................................23
4.5.2. Search Result...............................................27
4.5.3. Continuation References in the Search Result................28
4.6. Modify Operation..............................................29
4.7. Add Operation.................................................31
4.8. Delete Operation..............................................32
4.9. Modify DN Operation...........................................32
4.10. Compare Operation............................................33
4.11. Abandon Operation............................................34
4.12. Extended Operation...........................................35
5. Protocol Element Encodings and Transfer.........................35
5.1. Mapping Onto BER-based Transport Services.....................35
5.2. Transfer Protocols............................................36
5.2.1. Transmission Control Protocol (TCP).........................36
6. Implementation Guidelines.......................................36
6.1. Server Implementations........................................36
6.2. Client Implementations........................................36
7. Security Considerations.........................................37
8. Acknowledgements................................................37
9. Bibliography....................................................37
10. Editor's Address...............................................38
Appendix A - Complete ASN.1 Definition.............................40
Appendix B - Change History........................................45
B.1 Editorial......................................................45
B.2 Section 1......................................................45
B.3 Section 9......................................................45
B.4 Section 4.1.6..................................................45
B.5 Section 4.1.7..................................................45
B.6 Sections 4.2, 4.9, 4.10........................................45
B.7 Sections 4.5 and Appendix A....................................46
B.7 Section 3.4....................................................46
B.8 Section 4.1.12.................................................46
B.9 Section 4.2....................................................46
B.10 Section 4.2.(various).........................................46
B.11 Section 4.2.2.................................................46
Appendix C - Outstanding Work Items................................46
C.1 Integrate result codes draft...................................46
C.2 Section 3.1....................................................47
C.3 Section 4......................................................47
C.4 Section 4.1.1..................................................47
Sermersheim Internet-Draft - Expires Jan 2002 Page 2
Lightweight Directory Access Protocol Version 3
C.5 Section 4.1.1.1................................................47
C.6 Section 4.1.2..................................................47
C.7 Section 4.1.4..................................................47
C.8 Section 4.1.5..................................................48
C.9 Section 4.1.5.1................................................48
C.11 Section 4.1.7.................................................48
C.12 Section 4.1.8.................................................48
C.13 Section 4.1.11................................................49
C.14 Section 4.1.12................................................49
C.15 Section 4.2...................................................49
C.17 Section 4.2.2.................................................49
C.18 Section 4.2.3.................................................49
C.19 Section 4.3...................................................49
C.20 Section 4.4...................................................50
C.21 Section 4.5.1.................................................50
C.22 Section 4.5.2.................................................50
C.23 Section 4.5.3.................................................50
C.24 Section 4.5.3.1...............................................50
C.25 Section 4.6...................................................51
C.26 Section 4.7...................................................51
C.27 Section 4.10..................................................51
C.28 Section 4.11..................................................51
C.29 Section 4.12..................................................51
C.30 Section 5.1...................................................51
C.31 Section 5.2.1.................................................51
C.32 Section 6.1...................................................51
C.33 Section 7.....................................................52
2. Abstract
The protocol described in this document is designed to provide access
to directories supporting the [X.500] models, while not incurring the
resource requirements of the X.500 Directory Access Protocol (DAP).
This protocol is specifically targeted at management applications and
browser applications that provide read/write interactive access to
directories. When used with a directory supporting the X.500
protocols, it is intended to be a complement to the X.500 DAP.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY" in this document are
to be interpreted as described in [RFC2119].
Key aspects of this version of LDAP are:
- All protocol elements of LDAPv2 [RFC1777] are supported. The
protocol is carried directly over TCP or other transport,
bypassing much of the session/presentation overhead of X.500 DAP.
- Most protocol data elements can be encoded as ordinary strings
(e.g., Distinguished Names).
- Referrals to other servers may be returned.
Sermersheim Internet-Draft - Expires Jan 2002 Page 3
Lightweight Directory Access Protocol Version 3
- SASL mechanisms may be used with LDAP to provide association
security services.
- Attribute values and Distinguished Names have been
internationalized through the use of the ISO 10646 character set.
- The protocol can be extended to support new operations, and
controls may be used to extend existing operations.
- Schema is published in the directory to be used by clients.
3. Models
Interest in X.500 directory technologies in the Internet has led to
efforts to reduce the high cost of entry associated with use of these
technologies. This document continues the efforts to define directory
protocol alternatives, updating the LDAPv2 protocol specification.
3.1. Protocol Model
The general model adopted by this protocol is one of clients
performing protocol operations against servers. In this model, a
client transmits a protocol request describing the operation to be
performed to a server. The server is then responsible for performing
the necessary operation(s) in the directory. Upon completion of the
operation(s), the server returns a response containing any results or
errors to the requesting client.
In keeping with the goal of easing the costs associated with use of
the directory, it is an objective of this protocol to minimize the
complexity of clients so as to facilitate widespread deployment of
applications capable of using the directory.
Note that although servers are required to return responses whenever
such responses are defined in the protocol, there is no requirement
for synchronous behavior on the part of either clients or servers.
Requests and responses for multiple operations may be exchanged
between a client and server in any order, provided the client
eventually receives a response for every request that requires one.
In LDAP versions 1 and 2, no provision was made for protocol servers
returning referrals to clients. However, for improved performance and
distribution, this version of the protocol permits servers to return
to clients, referrals to other servers. This allows servers to
offload the work of contacting other servers to progress operations.
Note that the core protocol operations defined in this document can
be mapped to a strict subset of the X.500(1997) directory abstract
service, so it can be cleanly provided by the DAP. However there is
not a one-to-one mapping between LDAP protocol operations and DAP
operations: server implementations acting as a gateway to X.500
directories may need to make multiple DAP requests.
<Editor's Note: Sections 3.2 through 3.3 have not been updated>
Sermersheim Internet-Draft - Expires Jan 2002 Page 4
Lightweight Directory Access Protocol Version 3
3.2. Data Model
This section provides a brief introduction to the X.500 data model,
as used by LDAP.
The LDAP protocol assumes there are one or more servers which jointly
provide access to a Directory Information Tree (DIT). The tree is
made up of entries. Entries have names: one or more attribute values
from the entry form its relative distinguished name (RDN), which MUST
be unique among all its siblings. The concatenation of the relative
distinguished names of the sequence of entries from a particular
entry to an immediate subordinate of the root of the tree forms that
entry's Distinguished Name (DN), which is unique in the tree. An
example of a Distinguished Name is:
CN=Steve Kille, O=Isode Limited, C=GB
Some servers may hold cache or shadow copies of entries, which can be
used to answer search and comparison queries, but will return
referrals or contact other servers if modification operations are
requested.
Servers that perform caching or shadowing MUST ensure that they do
not violate any access control constraints placed on the data by the
originating server.
The largest collection of entries, starting at an entry that is
mastered by a particular server, and including all its subordinates
and their subordinates, down to the entries which are mastered by
different servers, is termed a naming context. The root of the DIT is
a DSA-specific Entry (DSE) and not part of any naming context: each
server has different attribute values in the root DSE. (DSA is an
X.500 term for the directory server).
3.2.1. Attributes of Entries
Entries consist of a set of attributes. An attribute is a type with
one or more associated values. The attribute type is identified by a
short descriptive name and an OID (object identifier). The attribute
type governs whether there can be more than one value of an attribute
of that type in an entry, the syntax to which the values must
conform, the kinds of matching which can be performed on values of
that attribute, and other functions.
An example of an attribute is "mail". There may be one or more values
of this attribute, they must be IA5 (ASCII) strings, and they are
case insensitive (e.g. "foo@bar.com" will match "FOO@BAR.COM").
Schema is the collection of attribute type definitions, object class
definitions and other information which a server uses to determine
how to match a filter or attribute value assertion (in a compare
operation) against the attributes of an entry, and whether to permit
add and modify operations. The definition of schema for use with LDAP
Sermersheim Internet-Draft - Expires Jan 2002 Page 5
Lightweight Directory Access Protocol Version 3
is given in [RFC2252] and [X.501]. Additional schema elements may be
defined in other documents.
Each entry MUST have an objectClass attribute. The objectClass
attribute specifies the object classes of an entry, which along with
the system and user schema determine the permitted attributes of an
entry. Values of this attribute may be modified by clients, but the
objectClass attribute cannot be removed. Servers may restrict the
modifications of this attribute to prevent the basic structural class
of the entry from being changed (e.g. one cannot change a person into
a country). When creating an entry or adding an objectClass value to
an entry, all superclasses of the named classes are implicitly added
as well if not already present, and the client must supply values for
any mandatory attributes of new superclasses.
Some attributes, termed operational attributes, are used by servers
for administering the directory system itself. They are not returned
in search results unless explicitly requested by name. Attributes
which are not operational, such as "mail", will have their schema and
syntax constraints enforced by servers, but servers will generally
not make use of their values.
Servers MUST NOT permit clients to add attributes to an entry unless
those attributes are permitted by the object class definitions, the
schema controlling that entry (specified in the subschema see
below), or are operational attributes known to that server and used
for administrative purposes. Note that there is a particular
objectClass 'extensibleObject' defined in [RFC2252] which permits all
user attributes to be present in an entry.
Entries MAY contain, among others, the following operational
attributes, defined in [RFC2252]. These attributes are maintained
automatically by the server and are not modifiable by clients:
- creatorsName: the Distinguished Name of the user who added this
entry to the directory.
- createTimestamp: the time this entry was added to the directory.
- modifiersName: the Distinguished Name of the user who last
modified this entry.
- modifyTimestamp: the time this entry was last modified.
- subschemaSubentry: the Distinguished Name of the subschema entry
(or subentry) which controls the schema for this entry.
3.2.2. Subschema Entries and Subentries
Subschema entries are used for administering information about the
directory schema, in particular the object classes and attribute
types supported by directory servers. A single subschema entry
contains all schema definitions used by entries in a particular part
of the directory tree.
Sermersheim Internet-Draft - Expires Jan 2002 Page 6
Lightweight Directory Access Protocol Version 3
Servers which follow X.500(93) models SHOULD implement subschema
using the X.500 subschema mechanisms, and so these subschemas are not
ordinary entries. LDAP clients SHOULD NOT assume that servers
implement any of the other aspects of X.500 subschema. A server which
masters entries and permits clients to modify these entries MUST
implement and provide access to these subschema entries, so that its
clients may discover the attributes and object classes which are
permitted to be present. It is strongly recommended that all other
servers implement this as well.
The following four attributes MUST be present in all subschema
entries:
- cn: this attribute MUST be used to form the RDN of the subschema
entry.
- objectClass: the attribute MUST have at least the values "top" and
"subschema".
- objectClasses: each value of this attribute specifies an object
class known to the server.
- attributeTypes: each value of this attribute specifies an
attribute type known to the server.
These are defined in [RFC2252]. Other attributes MAY be present in
subschema entries, to reflect additional supported capabilities.
These include matchingRules, matchingRuleUse, dITStructureRules,
dITContentRules, nameForms and ldapSyntaxes.
Servers SHOULD provide the attributes createTimestamp and
modifyTimestamp in subschema entries, in order to allow clients to
maintain their caches of schema information.
Clients MUST only retrieve attributes from a subschema entry by
requesting a base object search of the entry, where the search filter
is "(objectClass=subschema)". This will allow LDAPv3 servers which
gateway to X.500(93) to detect that subentry information is being
requested.
3.3. Relationship to X.500
This document defines LDAP in terms of X.500 as an X.500 access
mechanism. An LDAP server MUST act in accordance with the X.500(1993)
series of ITU recommendations when providing the service. However, it
is not required that an LDAP server make use of any X.500 protocols
in providing this service, e.g. LDAP can be mapped onto any other
directory system so long as the X.500 data and service model as used
in LDAP is not violated in the LDAP interface.
3.4. Server-specific Data Requirements
Sermersheim Internet-Draft - Expires Jan 2002 Page 7
Lightweight Directory Access Protocol Version 3
An LDAP server MUST provide information about itself and other
information that is specific to each server. This is represented as a
group of attributes located in the root DSE (DSA-Specific Entry),
which is named with the zero-length LDAPDN. These attributes are
retrievable if a client performs a base object search of the root
with filter "(objectClass=*)", however they are subject to access
control restrictions. The root DSE MUST NOT be included if the client
performs a subtree search starting from the root.
Servers may allow clients to modify these attributes.
The following attributes of the root DSE are defined in section 5 of
[RFC2252]. Additional attributes may be defined in other documents.
- namingContexts: naming contexts held in the server. Naming
contexts are defined in section 17 of [X.501].
- subschemaSubentry: subschema entry (or subentry) holding the
schema for the root DSE.
- altServer: alternative servers in case this one is later
unavailable.
- supportedExtension: list of supported extended operations.
- supportedControl: list of supported controls.
- supportedSASLMechanisms: list of supported SASL security features.
- supportedLDAPVersion: LDAP versions implemented by the server.
If the server does not master entries and does not know the locations
of schema information, the subschemaSubentry attribute is not present
in the root DSE. If the server masters directory entries under one or
more schema rules, the schema for each entry is found by reading the
subschemaSubentry attribute for that entry.
4. Elements of Protocol
The LDAP protocol is described using Abstract Syntax Notation 1
(ASN.1) [X.680], and is typically transferred using a subset of ASN.1
Basic Encoding Rules [X.690] In order to support future extensions to
this protocol, clients and servers MUST ignore elements of SEQUENCE
encodings whose tags they do not recognize.
Note that unlike X.500, each change to the LDAP protocol other than
through the extension mechanisms will have a different version
number. A client will indicate the version it supports as part of the
bind request, described in section 4.2. If a client has not sent a
bind, the server MUST assume that version 3 is supported in the
client (since version 2 required that the client bind first).
Clients may determine the protocol version a server supports by
reading the supportedLDAPVersion attribute from the root DSE. Servers
Sermersheim Internet-Draft - Expires Jan 2002 Page 8
Lightweight Directory Access Protocol Version 3
which implement version 3 or later versions MUST provide this
attribute. Servers which only implement version 2 may not provide
this attribute.
4.1. Common Elements
This section describes the LDAPMessage envelope PDU (Protocol Data
Unit) format, as well as data type definitions, which are used in the
protocol operations.
4.1.1. Message Envelope
For the purposes of protocol exchanges, all protocol operations are
encapsulated in a common envelope, the LDAPMessage, which is defined
as follows:
LDAPMessage ::= SEQUENCE {
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
The function of the LDAPMessage is to provide an envelope containing
common fields required in all protocol exchanges. At this time the
only common fields are the message ID and the controls.
If the server receives a PDU from the client in which the LDAPMessage
SEQUENCE tag cannot be recognized, the messageID cannot be parsed,
the tag of the protocolOp is not recognized as a request, or the
encoding structures or lengths of data fields are found to be
incorrect, then the server MUST return the notice of disconnection
Sermersheim Internet-Draft - Expires Jan 2002 Page 9
Lightweight Directory Access Protocol Version 3
described in section 4.4.1, with resultCode protocolError, and
immediately close the connection. In other cases that the server
cannot parse the request received by the client, the server MUST
return an appropriate response to the request, with the resultCode
set to protocolError.
If the client receives a PDU from the server, which cannot be parsed,
the client may discard the PDU, or may abruptly close the connection.
The ASN.1 type Controls is defined in section 4.1.12.
4.1.1.1. Message ID
All LDAPMessage envelopes encapsulating responses contain the
messageID value of the corresponding request LDAPMessage.
The message ID of a request MUST have a value different from the
values of any other requests outstanding in the LDAP session of which
this message is a part.
A client MUST NOT send a second request with the same message ID as
an earlier request on the same connection if the client has not
received the final response from the earlier request. Otherwise the
behavior is undefined. Typical clients increment a counter for each
request.
A client MUST NOT reuse the message id of an abandonRequest or of the
abandoned operation until it has received a response from the server
for another request invoked subsequent to the abandonRequest, as the
abandonRequest itself does not have a response.
4.1.2. String Types
The LDAPString is a notational convenience to indicate that, although
strings of LDAPString type encode as OCTET STRING types, the
[ISO10646] character set (a superset of Unicode) is used, encoded
following the UTF-8 algorithm [RFC2044]. Note that in the UTF-8
algorithm characters which are the same as ASCII (0x0000 through
0x007F) are represented as that same ASCII character in a single
byte. The other byte values are used to form a variable-length
encoding of an arbitrary character.
LDAPString ::= OCTET STRING
The LDAPOID is a notational convenience to indicate that the
permitted value of this string is a (UTF-8 encoded) dotted-decimal
representation of an OBJECT IDENTIFIER.
LDAPOID ::= OCTET STRING
For example,
1.3.6.1.4.1.1466.1.2.3
Sermersheim Internet-Draft - Expires Jan 2002 Page 10
Lightweight Directory Access Protocol Version 3
4.1.3. Distinguished Name and Relative Distinguished Name
An LDAPDN and a RelativeLDAPDN are respectively defined to be the
representation of a Distinguished Name and a Relative Distinguished
Name after encoding according to the specification in [RFC2253], such
that:
distinguished-name = name
relative-distinguished-name = name-component
where name and name-component are as defined in [RFC2253].
LDAPDN ::= LDAPString
RelativeLDAPDN ::= LDAPString
Only Attribute Types can be present in a relative distinguished name
component--the options of Attribute Descriptions (next section) MUST
NOT be used in specifying distinguished names.
4.1.4. Attribute Type
An AttributeType takes on as its value the textual string associated
with that AttributeType in its specification.
AttributeType ::= LDAPString
Each attribute type has a unique OBJECT IDENTIFIER which has been
assigned to it. This identifier may be written as decimal digits with
components separated by periods, e.g. "2.5.4.10".
A specification may also assign one or more textual names for an
attribute type. These names MUST begin with a letter, and only
contain ASCII letters, digit characters and hyphens. They are case
insensitive. These ASCII characters are identical to ISO 10646
characters whose UTF-8 encoding is a single byte between 0x00 and
0x7F.
If the server has a textual name for an attribute type, it MUST use a
textual name for attributes returned in search results. The dotted-
decimal OBJECT IDENTIFIER is only used if there is no textual name
for an attribute type.
Attribute type textual names are non-unique, as two different
specifications (neither in standards track RFCs) may choose the same
name.
A server which masters or shadows entries SHOULD list all the
attribute types it supports in the subschema entries, using the
attributeTypes attribute. Servers which support an open-ended set of
attributes SHOULD include at least the attributeTypes value for the
'objectClass' attribute. Clients MAY retrieve the attributeTypes
Sermersheim Internet-Draft - Expires Jan 2002 Page 11
Lightweight Directory Access Protocol Version 3
value from subschema entries in order to obtain the OBJECT IDENTIFIER
and other information associated with attribute types.
Some attribute type names which are used in this version of LDAP are
described in [RFC2252]. Servers may implement additional attribute
types.
4.1.5. Attribute Description
An AttributeDescription is a superset of the definition of the
AttributeType. It has the same ASN.1 definition, but allows
additional options to be specified. They are also case insensitive.
AttributeDescription ::= LDAPString
A value of AttributeDescription is based on the following BNF:
<AttributeDescription> ::= <AttributeType> [ ";" <options> ]
<options> ::= <option> | <option> ";" <options>
<option> ::= <opt-char> <opt-char>*
<opt-char> ::= ASCII-equivalent letters, numbers and hyphen
Examples of valid AttributeDescription:
cn
userCertificate;binary
One option, "binary", is defined in this document. Additional options
may be defined in IETF standards-track and experimental RFCs. Options
beginning with "x-" are reserved for private experiments. Any option
could be associated with any AttributeType, although not all
combinations may be supported by a server.
An AttributeDescription with one or more options is treated as a
subtype of the attribute type without any options. Options present in
an AttributeDescription are never mutually exclusive. Implementations
MUST generate the <options> list sorted in ascending order, and
servers MUST treat any two AttributeDescription with the same
AttributeType and options as equivalent. A server will treat an
AttributeDescription with any options it does not implement as an
unrecognized attribute type.
The data type "AttributeDescriptionList" describes a list of 0 or
more attribute types. (A list of zero elements has special
significance in the Search request.)
AttributeDescriptionList ::= SEQUENCE OF
AttributeDescription
4.1.5.1. Binary Option
Sermersheim Internet-Draft - Expires Jan 2002 Page 12
Lightweight Directory Access Protocol Version 3
If the "binary" option is present in an AttributeDescription, it
overrides any string-based encoding representation defined for that
attribute in [RFC2252]. Instead the attribute is to be transferred as
a binary value encoded using the Basic Encoding Rules [X.690]. The
syntax of the binary value is an ASN.1 data type definition which is
referenced by the "SYNTAX" part of the attribute type definition.
The presence or absence of the "binary" option only affects the
transfer of attribute values in protocol; servers store any
particular attribute in a single format. If a client requests that a
server return an attribute in the binary format, but the server
cannot generate that format, the server MUST treat this attribute
type as an unrecognized attribute type. Similarly, clients MUST NOT
expect servers to return an attribute in binary format if the client
requested that attribute by name without the "binary" option.
This option is intended to be used with attributes whose syntax is a
complex ASN.1 data type, and the structure of values of that type is
needed by clients. Examples of this kind of syntax are "Certificate"
and "CertificateList".
4.1.6. Attribute Value
A field of type AttributeValue is an OCTET STRING containing an
encoded value of an AttributeValue data type. The value is string
encoded unless an option specifying the transfer encoding is present
in the companion AttributeDescription to this AttributeValue (e.g.
"binary"). Multiple options specifying transfer encoding MUST NOT be
present.
The definition of string encodings for different syntaxes and types
may be found in other documents, and in particular [RFC2252].
At the time of this writing, there is only one AttributeDescription
option used to specify transfer encoding--"binary", described in
section 4.1.5.1.
AttributeValue ::= OCTET STRING
Note that there is no defined limit on the size of this encoding;
thus protocol values may include multi-megabyte attributes (e.g.
photographs).
Attributes may be defined which have arbitrary and non-printable
syntax. Implementations MUST NEITHER simply display nor attempt to
decode as ASN.1 a value if its syntax is not known. The
implementation may attempt to discover the subschema of the source
entry, and retrieve the values of attributeTypes from it.
Clients MUST NOT send attribute values in a request which are not
valid according to the syntax defined for the attributes.
4.1.7. Attribute Value Assertion
Sermersheim Internet-Draft - Expires Jan 2002 Page 13
Lightweight Directory Access Protocol Version 3
The AttributeValueAssertion type definition is similar to the one in
the X.500 directory standards. It contains an attribute description
and a matching rule assertion value suitable for that type.
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
If an option specifying the transfer encoding is present in
attributeDesc, the assertionValue is encoded as specified by the
option. For example, if the "binary" option is present in the
attributeDesc, the AssertionValue is BER encoded.
For all the string-valued user attributes described in [5], the
assertion value syntax is the same as the value syntax. Clients may
use attribute values as assertion values in compare requests and
search filters.
Note however that the assertion syntax may be different from the
value syntax for other attributes or for non-equality matching rules.
These may have an assertion syntax which contains only part of the
value. See section 20.2.1.8 of [X.501] for examples.
4.1.8. Attribute
An attribute consists of a type and one or more values of that type.
(Though attributes MUST have at least one value when stored, due to
access control restrictions the set may be empty when transferred in
protocol. This is described in section 4.5.2, concerning the
PartialAttributeList type.)
Attribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Each attribute value is distinct in the set (no duplicates). The
order of attribute values within the vals set is undefined and
implementation-dependent, and MUST NOT be relied upon.
4.1.9. Matching Rule Identifier
A matching rule is a means of expressing how a server should compare
an AssertionValue received in a search filter with an abstract data
value. The matching rule defines the syntax of the assertion value
and the process to be performed in the server.
An X.501 (1993) Matching Rule is identified in the LDAP protocol by
the printable representation of its OBJECT IDENTIFIER, either as one
of the strings given in [RFC2252], or as decimal digits with
components separated by periods, e.g. "caseIgnoreIA5Match" or
"1.3.6.1.4.1.453.33.33".
Sermersheim Internet-Draft - Expires Jan 2002 Page 14
Lightweight Directory Access Protocol Version 3
MatchingRuleId ::= LDAPString
Servers which support matching rules for use in the extensibleMatch
search filter MUST list the matching rules they implement in
subschema entries, using the matchingRules attributes. The server
SHOULD also list there, using the matchingRuleUse attribute, the
attribute types with which each matching rule can be used. More
information is given in section 4.4 of [RFC2252].
4.1.10. Result Message
The LDAPResult is the construct used in this protocol to return
success or failure indications from servers to clients. In response
to various requests, servers will return responses containing fields
of type LDAPResult to indicate the final status of a protocol
operation request.
LDAPResult ::= SEQUENCE {
resultCode ENUMERATED {
success (0),
operationsError (1),
protocolError (2),
timeLimitExceeded (3),
sizeLimitExceeded (4),
compareFalse (5),
compareTrue (6),
authMethodNotSupported (7),
strongAuthRequired (8),
-- 9 reserved --
referral (10), -- new
adminLimitExceeded (11), -- new
unavailableCriticalExtension (12), -- new
confidentialityRequired (13), -- new
saslBindInProgress (14), -- new
noSuchAttribute (16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation (19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
noSuchObject (32),
aliasProblem (33),
invalidDNSyntax (34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
invalidCredentials (49),
insufficientAccessRights (50),
busy (51),
unavailable (52),
unwillingToPerform (53),
loopDetect (54),
Sermersheim Internet-Draft - Expires Jan 2002 Page 15
Lightweight Directory Access Protocol Version 3
-- 55-63 unused --
namingViolation (64),
objectClassViolation (65),
notAllowedOnNonLeaf (66),
notAllowedOnRDN (67),
entryAlreadyExists (68),
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71), -- new
-- 72-79 unused --
other (80) },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
errorMessage LDAPString,
referral [3] Referral OPTIONAL }
All the result codes with the exception of success, compareFalse and
compareTrue are to be treated as meaning the operation could not be
completed in its entirety.
Most of the result codes are based on problem indications from X.511
error data types. Result codes from 16 to 21 indicate an
AttributeProblem, codes 32, 33, 34 and 36 indicate a NameProblem,
codes 48, 49 and 50 indicate a SecurityProblem, codes 51 to 54
indicate a ServiceProblem, and codes 64 to 69 and 71 indicates an
UpdateProblem.
If a client receives a result code which is not listed above, it is
to be treated as an unknown error condition.
The errorMessage field of this construct may, at the server's option,
be used to return a string containing a textual, human-readable
(terminal control and page formatting characters should be avoided)
error diagnostic. As this error diagnostic is not standardized,
implementations MUST NOT rely on the values returned. If the server
chooses not to return a textual diagnostic, the errorMessage field of
the LDAPResult type MUST contain a zero length string.
For result codes of noSuchObject, aliasProblem, invalidDNSyntax and
aliasDereferencingProblem, the matchedDN field is set to the name of
the lowest entry (object or alias) in the directory that was matched.
If no aliases were dereferenced while attempting to locate the entry,
this will be a truncated form of the name provided, or if aliases
were dereferenced, of the resulting name, as defined in section 12.5
of [X.511]. The matchedDN field is to be set to a zero length string
with all other result codes.
4.1.11. Referral
The referral result code indicates that the contacted server does not
hold the target entry of the request. The referral field is present
in an LDAPResult if the LDAPResult.resultCode field value is
referral, and absent with all other result codes. It contains a
reference to another server (or set of servers) which may be accessed
Sermersheim Internet-Draft - Expires Jan 2002 Page 16
Lightweight Directory Access Protocol Version 3
via LDAP or other protocols. Referrals can be returned in response to
any operation request (except unbind and abandon which do not have
responses). At least one URL MUST be present in the Referral.
The referral is not returned for a singleLevel or wholeSubtree search
in which the search scope spans multiple naming contexts, and several
different servers would need to be contacted to complete the
operation. Instead, continuation references, described in section
4.5.3, are returned.
Referral ::= SEQUENCE OF LDAPURL -- one or more
LDAPURL ::= LDAPString -- limited to characters permitted in
-- URLs
If the client wishes to progress the operation, it MUST follow the
referral by contacting any one of servers. All the URLs MUST be
equally capable of being used to progress the operation. (The
mechanisms for how this is achieved by multiple servers are outside
the scope of this document.)
URLs for servers implementing the LDAP protocol are written according
to [RFC2255]. If an alias was dereferenced, the <dn> part of the URL
MUST be present, with the new target object name. If the <dn> part is
present, the client MUST use this name in its next request to
progress the operation, and if it is not present the client will use
the same name as in the original request. Some servers (e.g.
participating in distributed indexing) may provide a different filter
in a referral for a search operation. If the filter part of the URL
is present in an LDAPURL, the client MUST use this filter in its next
request to progress this search, and if it is not present the client
MUST use the same filter as it used for that search. Other aspects of
the new request may be the same or different as the request which
generated the referral.
Note that UTF-8 characters appearing in a DN or search filter may not
be legal for URLs (e.g. spaces) and MUST be escaped using the %
method in [RFC2396].
Other kinds of URLs may be returned, so long as the operation could
be performed using that protocol.
4.1.12. Controls
A control is a way to specify extension information. Controls which
are sent as part of a request apply only to that request and are not
saved.
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
Sermersheim Internet-Draft - Expires Jan 2002 Page 17
Lightweight Directory Access Protocol Version 3
The controlType field MUST be a UTF-8 encoded dotted-decimal
representation of an OBJECT IDENTIFIER which uniquely identifies the
control. This prevents conflicts between control names.
The criticality field is either TRUE or FALSE and is only used when a
control accompanies one of the following requests: bindRequest,
searchRequest, modifyRequest, addRequest, delRequest, modDNRequest,
compareRequest, or extendedReq. The use of the criticality field for
a control that is part of any other operation is ignored and treated
as FALSE.
If the server recognizes the control type and it is appropriate for
the operation, the server will make use of the control when
performing the operation.
If the server does not recognize the control type or it is not
appropriate for the operation, and the criticality field is TRUE, the
server MUST NOT perform the operation, and MUST instead return the
resultCode unavailableCriticalExtension.
If the control is unrecognized or inappropriate but the criticality
field is FALSE, the server MUST ignore the control.
The controlValue contains any information associated with the
control, and its format is defined for the control. The server MUST
be prepared to handle arbitrary contents of the controlValue octet
string, including zero bytes. It is absent only if there is no value
information which is associated with a control of its type.
This document does not define any controls. Controls may be defined
in other documents. The definition of a control consists of:
- the OBJECT IDENTIFIER assigned to the control,
- whether the control is always noncritical, always critical, or
critical at the client's option,
- the format of the controlValue contents of the control.
Servers list the controls which they recognize in the
supportedControl attribute in the root DSE.
4.2. Bind Operation
The function of the Bind Operation is to allow authentication
information to be exchanged between the client and server.
The Bind Request is defined as follows:
BindRequest ::= [APPLICATION 0] SEQUENCE {
version INTEGER (1 .. 127),
name LDAPDN,
authentication AuthenticationChoice }
Sermersheim Internet-Draft - Expires Jan 2002 Page 18
Lightweight Directory Access Protocol Version 3
AuthenticationChoice ::= CHOICE {
simple [0] OCTET STRING,
-- 1 and 2 reserved
sasl [3] SaslCredentials }
SaslCredentials ::= SEQUENCE {
mechanism LDAPString,
credentials OCTET STRING OPTIONAL }
Parameters of the Bind Request are:
- version: A version number indicating the version of the protocol
to be used in this protocol session. This document describes
version 3 of the LDAP protocol. Note that there is no version
negotiation, and the client just sets this parameter to the
version it desires. If the client requests protocol version 2, a
server that supports the version 2 protocol as described in
[RFC1777] will not return any v3-specific protocol fields. (Note
that not all LDAP servers will support protocol version 2, since
they may be unable to generate the attribute syntaxes associated
with version 2.)
- name: The name of the directory object that the client wishes to
bind as. This field may take on a null value (a zero length
string) for the purposes of anonymous binds, when authentication
has been performed at a lower layer, or when using SASL
credentials with a mechanism that includes the name in the
credentials. Server behavior is undefined when the name is a null
value, simple authentication is used, and a password is specified.
Note that the server SHOULD NOT perform any alias dereferencing in
determining the object to bind as.
- authentication: information used to authenticate the name, if any,
provided in the Bind Request.
Upon receipt of a Bind Request, a protocol server will authenticate
the requesting client, if necessary. The server will then return a
Bind Response to the client indicating the status of the
authentication.
Authorization is the use of this authentication information when
performing operations. Authorization MAY be affected by factors
outside of the LDAP Bind request, such as lower layer security
services.
4.2.1. Sequencing of the Bind Request
For some SASL authentication mechanisms, it may be necessary for the
client to invoke the BindRequest multiple times. If at any stage the
client wishes to abort the bind process it MAY unbind and then drop
the underlying connection. Clients MUST NOT invoke operations between
two Bind requests made as part of a multi-stage bind.
Sermersheim Internet-Draft - Expires Jan 2002 Page 19
Lightweight Directory Access Protocol Version 3
A client may abort a SASL bind negotiation by sending a BindRequest
with a different value in the mechanism field of SaslCredentials, or
an AuthenticationChoice other than sasl.
If the client sends a BindRequest with the sasl mechanism field as an
empty string, the server MUST return a BindResponse with
authMethodNotSupported as the resultCode. This will allow clients to
abort a negotiation if it wishes to try again with the same SASL
mechanism.
Unlike LDAP v2, the client need not send a Bind Request in the first
PDU of the connection. The client may request any operations and the
server MUST treat these as anonymous. If the server requires that the
client bind before browsing or modifying the directory, the server
MAY reject a request other than binding, unbinding or an extended
request with the "operationsError" result.
If the client did not bind before sending a request and receives an
operationsError, it may then send a Bind Request. If this also fails
or the client chooses not to bind on the existing connection, it will
close the connection, reopen it and begin again by first sending a
PDU with a Bind Request. This will aid in interoperating with servers
implementing other versions of LDAP.
Clients MAY send multiple bind requests on a connection to change
their credentials. A subsequent bind process has the effect of
abandoning all operations outstanding on the connection. (This
simplifies server implementation.) Authentication from earlier binds
are subsequently ignored, and so if the bind fails, the connection
will be treated as anonymous. If a SASL transfer encryption or
integrity mechanism has been negotiated, and that mechanism does not
support the changing of credentials from one identity to another,
then the client MUST instead establish a new connection.
4.2.2. Authentication and Other Security Services
The simple authentication option provides minimal authentication
facilities, with the contents of the authentication field consisting
only of a cleartext password. Note that the use of cleartext
passwords is not recommended over open networks when the underlying
transport service cannot guarantee confidentiality; see the "Security
Considerations" section.
If anonymous authentication is to be performed, then the simple
authentication option MUST be chosen, and the password be of zero
length. (This is often done by LDAPv2 clients.) Typically the name is
also of zero length.
The sasl choice allows for any mechanism defined for use with SASL
[RFC2222]. The mechanism field contains the name of the mechanism.
The credentials field contains the arbitrary data used for
authentication, inside an OCTET STRING wrapper. Note that unlike some
Internet application protocols where SASL is used, LDAP is not text-
Sermersheim Internet-Draft - Expires Jan 2002 Page 20
Lightweight Directory Access Protocol Version 3
based, thus no base64 transformations are performed on the
credentials.
If any SASL-based integrity or confidentiality services are enabled,
they take effect following the transmission by the server and
reception by the client of the final BindResponse with resultCode
success.
The client can request that the server use authentication information
from a lower layer protocol by using the SASL EXTERNAL mechanism.
4.2.3. Bind Response
The Bind Response is defined as follows.
BindResponse ::= [APPLICATION 1] SEQUENCE {
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
BindResponse consists simply of an indication from the server of the
status of the client's request for authentication.
If the bind was successful, the resultCode will be success, otherwise
it will be one of:
- operationsError: server encountered an internal error.
- protocolError: unrecognized version number or incorrect PDU
structure.
- authMethodNotSupported: unrecognized SASL mechanism name.
- strongAuthRequired: the server requires authentication be
performed with a SASL mechanism.
- referral: this server cannot accept this bind and the client
should try another.
- saslBindInProgress: the server requires the client to send a new
bind request, with the same sasl mechanism, to continue the
authentication process.
- inappropriateAuthentication: the server requires the client which
had attempted to bind anonymously or without supplying credentials
to provide some form of credentials.
- invalidCredentials: the wrong password was supplied or the SASL
credentials could not be processed.
- unavailable: the server is shutting down.
If the server does not support the client's requested protocol
version, it MUST set the resultCode to protocolError.
Sermersheim Internet-Draft - Expires Jan 2002 Page 21
Lightweight Directory Access Protocol Version 3
If the client receives a BindResponse response where the resultCode
was protocolError, it MUST close the connection as the server will be
unwilling to accept further operations. (This is for compatibility
with earlier versions of LDAP, in which the bind was always the first
operation, and there was no negotiation.)
The serverSaslCreds are used as part of a SASL-defined bind mechanism
to allow the client to authenticate the server to which it is
communicating, or to perform "challenge-response" authentication. If
the client bound with the password choice, or the SASL mechanism does
not require the server to return information to the client, then this
field is not to be included in the result.
4.3. Unbind Operation
The function of the Unbind Operation is to terminate a protocol
session. The Unbind Operation is defined as follows:
UnbindRequest ::= [APPLICATION 2] NULL
The Unbind Operation has no response defined. Upon transmission of an
UnbindRequest, a protocol client may assume that the protocol session
is terminated. Upon receipt of an UnbindRequest, a protocol server
may assume that the requesting client has terminated the session and
that all outstanding requests may be discarded, and may close the
connection.
4.4. Unsolicited Notification
An unsolicited notification is an LDAPMessage sent from the server to
the client which is not in response to any LDAPMessage received by
the server. It is used to signal an extraordinary condition in the
server or in the connection between the client and the server. The
notification is of an advisory nature, and the server will not expect
any response to be returned from the client.
The unsolicited notification is structured as an LDAPMessage in which
the messageID is 0 and protocolOp is of the extendedResp form. The
responseName field of the ExtendedResponse is present. The LDAPOID
value MUST be unique for this notification, and not be used in any
other situation.
One unsolicited notification is defined in this document.
4.4.1. Notice of Disconnection
This notification may be used by the server to advise the client that
the server is about to close the connection due to an error
condition. Note that this notification is NOT a response to an unbind
requested by the client: the server MUST follow the procedures of
section 4.3. This notification is intended to assist clients in
distinguishing between an error condition and a transient network
failure. As with a connection close due to network failure, the
Sermersheim Internet-Draft - Expires Jan 2002 Page 22
Lightweight Directory Access Protocol Version 3
client MUST NOT assume that any outstanding requests which modified
the directory have succeeded or failed.
The responseName is 1.3.6.1.4.1.1466.20036, the response field is
absent, and the resultCode is used to indicate the reason for the
disconnection.
The following resultCode values are to be used in this notification:
- protocolError: The server has received data from the client in
which the LDAPMessage structure could not be parsed.
- strongAuthRequired: The server has detected that an established
underlying security association protecting communication between
the client and server has unexpectedly failed or been compromised.
- unavailable: This server will stop accepting new connections and
operations on all existing connections, and be unavailable for an
extended period of time. The client may make use of an alternative
server.
After sending this notice, the server MUST close the connection.
After receiving this notice, the client MUST NOT transmit any further
on the connection, and may abruptly close the connection.
4.5. Search Operation
The Search Operation allows a client to request that a search be
performed on its behalf by a server. This can be used to read
attributes from a single entry, from entries immediately below a
particular entry, or a whole subtree of entries.
4.5.1. Search Request
The Search Request is defined as follows:
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
Sermersheim Internet-Draft - Expires Jan 2002 Page 23
Lightweight Directory Access Protocol Version 3
and [0] SET OF Filter,
or [1] SET OF Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- at least one must be present
substrings SEQUENCE OF CHOICE {
initial [0] AssertionValue,
any [1] AssertionValue,
final [2] AssertionValue } }
MatchingRuleAssertion ::= SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type [2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
Parameters of the Search Request are:
- baseObject: An LDAPDN that is the base object entry relative to
which the search is to be performed.
- scope: An indicator of the scope of the search to be performed.
The semantics of the possible values of this field are identical
to the semantics of the scope field in the X.511 Search Operation.
- derefAliases: An indicator as to how alias objects (as defined in
X.501) are to be handled in searching. The semantics of the
possible values of this field are:
neverDerefAliases: do not dereference aliases in searching
or in locating the base object of the search;
derefInSearching: dereference aliases in subordinates of
the base object in searching, but not in locating the base
object of the search;
derefFindingBaseObj: dereference aliases in locating the
base object of the search, but not when searching
subordinates of the base object;
derefAlways: dereference aliases both in searching and in
locating the base object of the search.
- sizeLimit: A size limit that restricts the maximum number of
entries to be returned as a result of the search. A value of 0 in
Sermersheim Internet-Draft - Expires Jan 2002 Page 24
Lightweight Directory Access Protocol Version 3
this field indicates that no client-requested size limit
restrictions are in effect for the search. Servers may enforce a
maximum number of entries to return.
- timeLimit: A time limit that restricts the maximum time (in
seconds) allowed for a search. A value of 0 in this field
indicates that no client-requested time limit restrictions are in
effect for the search.
- typesOnly: An indicator as to whether search results will contain
both attribute types and values, or just attribute types. Setting
this field to TRUE causes only attribute types (no values) to be
returned. Setting this field to FALSE causes both attribute types
and values to be returned.
- filter: A filter that defines the conditions that must be
fulfilled in order for the search to match a given entry.
The 'and', 'or' and 'not' choices can be used to form combinations
of filters. At least one filter element MUST be present in an
'and' or 'or' choice. The others match against individual
attribute values of entries in the scope of the search.
(Implementor's note: the 'not' filter is an example of a tagged
choice in an implicitly-tagged module. In BER this is treated as
if the tag was explicit.)
A server MUST evaluate filters according to the three-valued logic
of X.511 (1993) section 7.8.1. In summary, a filter is evaluated
to either "TRUE", "FALSE" or "Undefined". If the filter evaluates
to TRUE for a particular entry, then the attributes of that entry
are returned as part of the search result (subject to any
applicable access control restrictions). If the filter evaluates
to FALSE or Undefined, then the entry is ignored for the search.
A filter of the "and" choice is TRUE if all the filters in the SET
OF evaluate to TRUE, FALSE if at least one filter is FALSE, and
otherwise Undefined. A filter of the "or" choice is FALSE if all
of the filters in the SET OF evaluate to FALSE, TRUE if at least
one filter is TRUE, and Undefined otherwise. A filter of the "not"
choice is TRUE if the filter being negated is FALSE, FALSE if it
is TRUE, and Undefined if it is Undefined.
The present match evaluates to TRUE where there is an attribute or
subtype of the specified attribute description present in an
entry, and FALSE otherwise (including a presence test with an
unrecognized attribute description.)
The extensibleMatch is new in this version of LDAP. If the
matchingRule field is absent, the type field MUST be present, and
the equality match is performed for that type. If the type field
is absent and matchingRule is present, the matchValue is compared
against all attributes in an entry which support that
matchingRule, and the matchingRule determines the syntax for the
assertion value (the filter item evaluates to TRUE if it matches
Sermersheim Internet-Draft - Expires Jan 2002 Page 25
Lightweight Directory Access Protocol Version 3
with at least one attribute in the entry, FALSE if it does not
match any attribute in the entry, and Undefined if the
matchingRule is not recognized or the assertionValue cannot be
parsed.) If the type field is present and matchingRule is present,
the matchingRule MUST be one permitted for use with that type,
otherwise the filter item is undefined. If the dnAttributes field
is set to TRUE, the match is applied against all the attributes in
an entry's distinguished name as well, and also evaluates to TRUE
if there is at least one attribute in the distinguished name for
which the filter item evaluates to TRUE. (Editors note: The
dnAttributes field is present so that there does not need to be
multiple versions of generic matching rules such as for word
matching, one to apply to entries and another to apply to entries
and dn attributes as well).
A filter item evaluates to Undefined when the server would not be
able to determine whether the assertion value matches an entry. If
an attribute description in an equalityMatch, substrings,
greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch filter
is not recognized by the server, a matching rule id in the
extensibleMatch is not recognized by the server, the assertion
value cannot be parsed, or the type of filtering requested is not
implemented, then the filter is Undefined. Thus for example if a
server did not recognize the attribute type shoeSize, a filter of
(shoeSize=*) would evaluate to FALSE, and the filters
(shoeSize=12), (shoeSize>=12) and (shoeSize<=12) would evaluate to
Undefined.
Servers MUST NOT return errors if attribute descriptions or
matching rule ids are not recognized, or assertion values cannot
be parsed. More details of filter processing are given in section
7.8 of [X.511].
- attributes: A list of the attributes to be returned from each
entry which matches the search filter. There are two special
values which may be used: an empty list with no attributes, and
the attribute description string "*". Both of these signify that
all user attributes are to be returned. (The "*" allows the
client to request all user attributes in addition to specific
operational attributes).
Attributes MUST be named at most once in the list, and are
returned at most once in an entry. If there are attribute
descriptions in the list which are not recognized, they are
ignored by the server.
If the client does not want any attributes returned, it can
specify a list containing only the attribute with OID "1.1". This
OID was chosen arbitrarily and does not correspond to any
attribute in use.
Client implementors should note that even if all user attributes
are requested, some attributes of the entry may not be included in
search results due to access controls or other restrictions.
Sermersheim Internet-Draft - Expires Jan 2002 Page 26
Lightweight Directory Access Protocol Version 3
Furthermore, servers will not return operational attributes, such
as objectClasses or attributeTypes, unless they are listed by
name, since there may be extremely large number of values for
certain operational attributes. (A list of operational attributes
for use in LDAP is given in [RFC2252].)
Note that an X.500 "list"-like operation can be emulated by the
client requesting a one-level LDAP search operation with a filter
checking for the existence of the objectClass attribute, and that an
X.500 "read"-like operation can be emulated by a base object LDAP
search operation with the same filter. A server which provides a
gateway to X.500 is not required to use the Read or List operations,
although it may choose to do so, and if it does must provide the same
semantics as the X.500 search operation.
4.5.2. Search Result
The results of the search attempted by the server upon receipt of a
Search Request are returned in Search Responses, which are LDAP
messages containing either SearchResultEntry, SearchResultReference,
or SearchResultDone data types.
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
-- implementors should note that the PartialAttributeList may
-- have zero elements (if none of the attributes of that entry
-- were requested, or could be returned), and that the vals set
-- may also have zero elements (if types only was requested, or
-- all values were excluded from the result.)
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
-- at least one LDAPURL element must be present
SearchResultDone ::= [APPLICATION 5] LDAPResult
Upon receipt of a Search Request, a server will perform the necessary
search of the DIT.
If the LDAP session is operating over a connection-oriented transport
such as TCP, the server will return to the client a sequence of
responses in separate LDAP messages. There may be zero or more
responses containing SearchResultEntry, one for each entry found
during the search. There may also be zero or more responses
containing SearchResultReference, one for each area not explored by
this server during the search. The SearchResultEntry and
SearchResultReference PDUs may come in any order. Following all the
SearchResultReference responses and all SearchResultEntry responses
to be returned by the server, the server will return a response
Sermersheim Internet-Draft - Expires Jan 2002 Page 27
Lightweight Directory Access Protocol Version 3
containing the SearchResultDone, which contains an indication of
success, or detailing any errors that have occurred.
Each entry returned in a SearchResultEntry will contain all
attributes, complete with associated values if necessary, as
specified in the attributes field of the Search Request. Return of
attributes is subject to access control and other administrative
policy. Some attributes may be returned in binary format (indicated
by the AttributeDescription in the response having the "binary"
option present).
Some attributes may be constructed by the server and appear in a
SearchResultEntry attribute list, although they are not stored
attributes of an entry. Clients MUST NOT assume that all attributes
can be modified, even if permitted by access control.
4.5.3. Continuation References in the Search Result
If the server was able to locate the entry referred to by the
baseObject but was unable to search all the entries in the scope at
and under the baseObject, the server may return one or more
SearchResultReference entries, each containing a reference to another
set of servers for continuing the operation. A server MUST NOT return
any SearchResultReference if it has not located the baseObject and
thus has not searched any entries; in this case it would return a
SearchResultDone containing a referral resultCode.
In the absence of indexing information provided to a server from
servers holding subordinate naming contexts, SearchResultReference
responses are not affected by search filters and are always returned
when in scope.
The SearchResultReference is of the same data type as the Referral.
URLs for servers implementing the LDAP protocol are written according
to [RFC2255]. The <dn> part MUST be present in the URL, with the new
target object name. The client MUST use this name in its next
request. Some servers (e.g. part of a distributed index exchange
system) may provide a different filter in the URLs of the
SearchResultReference. If the filter part of the URL is present in an
LDAP URL, the client MUST use the new filter in its next request to
progress the search, and if the filter part is absent the client will
use again the same filter. Other aspects of the new search request
may be the same or different as the search which generated the
continuation references.
Other kinds of URLs may be returned so long as the operation could be
performed using that protocol.
The name of an unexplored subtree in a SearchResultReference need not
be subordinate to the base object.
In order to complete the search, the client MUST issue a new search
operation for each SearchResultReference that is returned. Note that
the abandon operation described in section 4.11 applies only to a
particular operation sent on a connection between a client and
Sermersheim Internet-Draft - Expires Jan 2002 Page 28
Lightweight Directory Access Protocol Version 3
server, and if the client has multiple outstanding search operations
to different servers, it MUST abandon each operation individually.
4.5.3.1. Example
For example, suppose the contacted server (hosta) holds the entry
"O=MNN,C=WW" and the entry "CN=Manager,O=MNN,C=WW". It knows that
either LDAP-capable servers (hostb) or (hostc) hold
"OU=People,O=MNN,C=WW" (one is the master and the other server a
shadow), and that LDAP-capable server (hostd) holds the subtree
"OU=Roles,O=MNN,C=WW". If a subtree search of "O=MNN,C=WW" is
requested to the contacted server, it may return the following:
SearchResultEntry for O=MNN,C=WW
SearchResultEntry for CN=Manager,O=MNN,C=WW
SearchResultReference {
ldap://hostb/OU=People,O=MNN,C=WW
ldap://hostc/OU=People,O=MNN,C=WW
}
SearchResultReference {
ldap://hostd/OU=Roles,O=MNN,C=WW
}
SearchResultDone (success)
Client implementors should note that when following a
SearchResultReference, additional SearchResultReference may be
generated. Continuing the example, if the client contacted the server
(hostb) and issued the search for the subtree "OU=People,O=MNN,C=WW",
the server might respond as follows:
SearchResultEntry for OU=People,O=MNN,C=WW
SearchResultReference {
ldap://hoste/OU=Managers,OU=People,O=MNN,C=WW
}
SearchResultReference {
ldap://hostf/OU=Consultants,OU=People,O=MNN,C=WW
}
SearchResultDone (success)
If the contacted server does not hold the base object for the search,
then it will return a referral to the client. For example, if the
client requests a subtree search of "O=XYZ,C=US" to hosta, the server
may return only a SearchResultDone containing a referral.
SearchResultDone (referral) {
ldap://hostg/
}
4.6. Modify Operation
The Modify Operation allows a client to request that a modification
of an entry be performed on its behalf by a server. The Modify
Request is defined as follows:
Sermersheim Internet-Draft - Expires Jan 2002 Page 29
Lightweight Directory Access Protocol Version 3
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Modify Request are:
- object: The object to be modified. The value of this field
contains the DN of the entry to be modified. The server will not
perform any alias dereferencing in determining the object to be
modified.
- modification: A list of modifications to be performed on the
entry. The entire list of entry modifications MUST be performed in
the order they are listed, as a single atomic operation. While
individual modifications may violate the directory schema, the
resulting entry after the entire list of modifications is
performed MUST conform to the requirements of the directory
schema. The values that may be taken on by the 'operation' field
in each modification construct have the following semantics
respectively:
add: add values listed to the given attribute, creating the
attribute if necessary;
delete: delete values listed from the given attribute,
removing the entire attribute if no values are listed, or
if all current values of the attribute are listed for
deletion;
replace: replace all existing values of the given attribute
with the new values listed, creating the attribute if it
did not already exist. A replace with no value will delete
the entire attribute if it exists, and is ignored if the
attribute does not exist.
The result of the modify attempted by the server upon receipt of a
Modify Request is returned in a Modify Response, defined as follows:
ModifyResponse ::= [APPLICATION 7] LDAPResult
Upon receipt of a Modify Request, a server will perform the necessary
modifications to the DIT.
The server will return to the client a single Modify Response
indicating either the successful completion of the DIT modification,
Sermersheim Internet-Draft - Expires Jan 2002 Page 30
Lightweight Directory Access Protocol Version 3
or the reason that the modification failed. Note that due to the
requirement for atomicity in applying the list of modifications in
the Modify Request, the client may expect that no modifications of
the DIT have been performed if the Modify Response received indicates
any sort of error, and that all requested modifications have been
performed if the Modify Response indicates successful completion of
the Modify Operation. If the connection fails, whether the
modification occurred or not is indeterminate.
The Modify Operation cannot be used to remove from an entry any of
its distinguished values, those values which form the entry's
relative distinguished name. An attempt to do so will result in the
server returning the error notAllowedOnRDN. The Modify DN Operation
described in section 4.9 is used to rename an entry.
If an equality match filter has not been defined for an attribute
type, clients MUST NOT attempt to delete individual values of that
attribute from an entry using the "delete" form of a modification,
and MUST instead use the "replace" form.
Note that due to the simplifications made in LDAP, there is not a
direct mapping of the modifications in an LDAP ModifyRequest onto the
EntryModifications of a DAP ModifyEntry operation, and different
implementations of LDAP-DAP gateways may use different means of
representing the change. If successful, the final effect of the
operations on the entry MUST be identical.
4.7. Add Operation
The Add Operation allows a client to request the addition of an entry
into the directory. The Add Request is defined as follows:
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Add Request are:
- entry: the Distinguished Name of the entry to be added. Note that
the server will not dereference any aliases in locating the entry
to be added.
- attributes: the list of attributes that make up the content of the
entry being added. Clients MUST include distinguished values
(those forming the entry's own RDN) in this list, the objectClass
attribute, and values of any mandatory attributes of the listed
object classes. Clients MUST NOT supply the createTimestamp or
creatorsName attributes, since these will be generated
automatically by the server.
Sermersheim Internet-Draft - Expires Jan 2002 Page 31
Lightweight Directory Access Protocol Version 3
The entry named in the entry field of the AddRequest MUST NOT exist
for the AddRequest to succeed. The parent of the entry to be added
MUST exist. For example, if the client attempted to add
"CN=JS,O=Foo,C=US", the "O=Foo,C=US" entry did not exist, and the
"C=US" entry did exist, then the server would return the error
noSuchObject with the matchedDN field containing "C=US". If the
parent entry exists but is not in a naming context held by the
server, the server SHOULD return a referral to the server holding the
parent entry.
Servers implementations SHOULD NOT restrict where entries can be
located in the directory. Some servers MAY allow the administrator to
restrict the classes of entries which can be added to the directory.
Upon receipt of an Add Request, a server will attempt to perform the
add requested. The result of the add attempt will be returned to the
client in the Add Response, defined as follows:
AddResponse ::= [APPLICATION 9] LDAPResult
A response of success indicates that the new entry is present in the
directory.
4.8. Delete Operation
The Delete Operation allows a client to request the removal of an
entry from the directory. The Delete Request is defined as follows:
DelRequest ::= [APPLICATION 10] LDAPDN
The Delete Request consists of the Distinguished Name of the entry to
be deleted. Note that the server will not dereference aliases while
resolving the name of the target entry to be removed, and that only
leaf entries (those with no subordinate entries) can be deleted with
this operation.
The result of the delete attempted by the server upon receipt of a
Delete Request is returned in the Delete Response, defined as
follows:
DelResponse ::= [APPLICATION 11] LDAPResult
Upon receipt of a Delete Request, a server will attempt to perform
the entry removal requested. The result of the delete attempt will be
returned to the client in the Delete Response.
4.9. Modify DN Operation
The Modify DN Operation allows a client to change the leftmost (least
significant) component of the name of an entry in the directory, or
to move a subtree of entries to a new location in the directory. The
Modify DN Request is defined as follows:
ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
Sermersheim Internet-Draft - Expires Jan 2002 Page 32
Lightweight Directory Access Protocol Version 3
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
Parameters of the Modify DN Request are:
- entry: the Distinguished Name of the entry to be changed. This
entry may or may not have subordinate entries. Note that the
server will not dereference any aliases in locating the entry to
be changed.
- newrdn: the RDN that will form the leftmost component of the new
name of the entry.
- deleteoldrdn: a boolean parameter that controls whether the old
RDN attribute values are to be retained as attributes of the
entry, or deleted from the entry.
- newSuperior: if present, this is the Distinguished Name of the
entry which becomes the immediate superior of the existing entry.
The result of the name change attempted by the server upon receipt of
a Modify DN Request is returned in the Modify DN Response, defined as
follows:
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
Upon receipt of a ModifyDNRequest, a server will attempt to perform
the name change. The result of the name change attempt will be
returned to the client in the Modify DN Response.
For example, if the entry named in the "entry" parameter was "cn=John
Smith,c=US", the newrdn parameter was "cn=John Cougar Smith", and the
newSuperior parameter was absent, then this operation would attempt
to rename the entry to be "cn=John Cougar Smith,c=US". If there was
already an entry with that name, the operation would fail with error
code entryAlreadyExists.
If the deleteoldrdn parameter is TRUE, the values forming the old RDN
are deleted from the entry. If the deleteoldrdn parameter is FALSE,
the values forming the old RDN will be retained as non-distinguished
attribute values of the entry. The server may not perform the
operation and return an error code if the setting of the deleteoldrdn
parameter would cause a schema inconsistency in the entry.
Note that X.500 restricts the ModifyDN operation to only affect
entries that are contained within a single server. If the LDAP server
is mapped onto DAP, then this restriction will apply, and the
resultCode affectsMultipleDSAs will be returned if this error
occurred. In general clients MUST NOT expect to be able to perform
arbitrary movements of entries and subtrees between servers.
4.10. Compare Operation
Sermersheim Internet-Draft - Expires Jan 2002 Page 33
Lightweight Directory Access Protocol Version 3
The Compare Operation allows a client to compare an assertion
provided with an entry in the directory. The Compare Request is
defined as follows:
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
Parameters of the Compare Request are:
- entry: the name of the entry to be compared with. Note that the
server SHOULD NOT dereference any aliases in locating the entry to
be compared with.
- ava: the assertion with which an attribute in the entry is to be
compared.
The result of the compare attempted by the server upon receipt of a
Compare Request is returned in the Compare Response, defined as
follows:
CompareResponse ::= [APPLICATION 15] LDAPResult
Upon receipt of a Compare Request, a server will attempt to perform
the requested comparison. The result of the comparison will be
returned to the client in the Compare Response. Note that errors and
the result of comparison are all returned in the same construct.
Note that some directory systems may establish access controls which
permit the values of certain attributes (such as userPassword) to be
compared but not read. In a search result, it may be that an
attribute of that type would be returned, but with an empty set of
values.
4.11. Abandon Operation
The function of the Abandon Operation is to allow a client to request
that the server abandon an outstanding operation. The Abandon Request
is defined as follows:
AbandonRequest ::= [APPLICATION 16] MessageID
The MessageID MUST be that of a an operation which was requested
earlier in this connection.
(The abandon request itself has its own message id. This is distinct
from the id of the earlier operation being abandoned.)
There is no response defined in the Abandon Operation. Upon
transmission of an Abandon Operation, a client may expect that the
operation identified by the Message ID in the Abandon Request has
been abandoned. In the event that a server receives an Abandon
Request on a Search Operation in the midst of transmitting responses
Sermersheim Internet-Draft - Expires Jan 2002 Page 34
Lightweight Directory Access Protocol Version 3
to the search, that server MUST cease transmitting entry responses to
the abandoned request immediately, and MUST NOT send the
SearchResponseDone. Of course, the server MUST ensure that only
properly encoded LDAPMessage PDUs are transmitted.
Clients MUST NOT send abandon requests for the same operation
multiple times, and MUST also be prepared to receive results from
operations it has abandoned (since these may have been in transit
when the abandon was requested).
Servers MUST discard abandon requests for message IDs they do not
recognize, for operations which cannot be abandoned, and for
operations which have already been abandoned.
4.12. Extended Operation
An extension mechanism has been added in this version of LDAP, in
order to allow additional operations to be defined for services not
available elsewhere in this protocol, for instance digitally signed
operations and results.
The extended operation allows clients to make requests and receive
responses with predefined syntaxes and semantics. These may be
defined in RFCs or be private to particular implementations. Each
request MUST have a unique OBJECT IDENTIFIER assigned to it.
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
The requestName is a dotted-decimal representation of the OBJECT
IDENTIFIER corresponding to the request. The requestValue is
information in a form defined by that request, encapsulated inside an
OCTET STRING.
The server will respond to this with an LDAPMessage containing the
ExtendedResponse.
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
If the server does not recognize the request name, it MUST return
only the response fields from LDAPResult, containing the
protocolError result code.
5. Protocol Element Encodings and Transfer
One underlying service is defined here. Clients and servers SHOULD
implement the mapping of LDAP over TCP described in 5.2.1.
5.1. Mapping Onto BER-based Transport Services
Sermersheim Internet-Draft - Expires Jan 2002 Page 35
Lightweight Directory Access Protocol Version 3
The protocol elements of LDAP are encoded for exchange using the
Basic Encoding Rules (BER) [X.690] of ASN.1 [X.680]. However, due to
the high overhead involved in using certain elements of the BER, the
following additional restrictions are placed on BER-encodings of LDAP
protocol elements:
(1) Only the definite form of length encoding will be used.
(2) OCTET STRING values will be encoded in the primitive form only.
(3) If the value of a BOOLEAN type is true, the encoding MUST have
its contents octets set to hex "FF".
(4) If a value of a type is its default value, it MUST be absent.
Only some BOOLEAN and INTEGER types have default values in this
protocol definition.
These restrictions do not apply to ASN.1 types encapsulated inside of
OCTET STRING values, such as attribute values, unless otherwise
noted.
5.2. Transfer Protocols
This protocol is designed to run over connection-oriented, reliable
transports, with all 8 bits in an octet being significant in the data
stream.
5.2.1. Transmission Control Protocol (TCP)
The LDAPMessage PDUs are mapped directly onto the TCP bytestream. It
is recommended that server implementations running over the TCP MAY
provide a protocol listener on the assigned port, 389. Servers may
instead provide a listener on a different port number. Clients MUST
support contacting servers on any valid TCP port.
6. Implementation Guidelines
This document describes an Internet protocol.
6.1. Server Implementations
The server MUST be capable of recognizing all the mandatory attribute
type names and implement the syntaxes specified in [RFC2252. Servers
MAY also recognize additional attribute type names.
6.2. Client Implementations
Clients which request referrals MUST ensure that they do not loop
between servers. They MUST NOT repeatedly contact the same server for
the same request with the same target entry name, scope and filter.
Some clients may be using a counter that is incremented each time
referral handling occurs for an operation, and these kinds of clients
MUST be able to handle a DIT with at least ten layers of naming
contexts between the root and a leaf entry.
Sermersheim Internet-Draft - Expires Jan 2002 Page 36
Lightweight Directory Access Protocol Version 3
In the absence of prior agreements with servers, clients SHOULD NOT
assume that servers support any particular schemas beyond those
referenced in section 6.1. Different schemas can have different
attribute types with the same names. The client can retrieve the
subschema entries referenced by the subschemaSubentry attribute in
the server's root DSE or in entries held by the server.
7. Security Considerations
When used with a connection-oriented transport, this version of the
protocol provides facilities for the LDAP v2 authentication
mechanism, simple authentication using a cleartext password, as well
as any SASL mechanism [RFC2222]. SASL allows for integrity and
privacy services to be negotiated.
It is also permitted that the server can return its credentials to
the client, if it chooses to do so.
Use of cleartext password is strongly discouraged where the
underlying transport service cannot guarantee confidentiality and may
result in disclosure of the password to unauthorized parties.
When used with SASL, it should be noted that the name field of the
BindRequest is not protected against modification. Thus if the
distinguished name of the client (an LDAPDN) is agreed through the
negotiation of the credentials, it takes precedence over any value in
the unprotected name field.
Implementations which cache attributes and entries obtained via LDAP
MUST ensure that access controls are maintained if that information
is to be provided to multiple clients, since servers may have access
control policies which prevent the return of entries or attributes in
search results except to particular authenticated clients. For
example, caches could serve result information only to the client
whose request caused it to be cache.
8. Acknowledgements
This document is an update to RFC 2251, by Mark Wahl, Tim Howes, and
Steve Kille. Their work along with the input of individuals of the
IETF LDAPEXT, LDUP, LDAPBIS, and other Working Groups is gratefully
acknowledged.
9. Bibliography
[ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC 10646-1
: 1993.
[X.500] ITU-T Rec. X.500, "The Directory: Overview of Concepts,
Models and Service", 1993.
[X.501] ITU-T Rec. X.501, "The Directory: Models", 1993.
Sermersheim Internet-Draft - Expires Jan 2002 Page 37
Lightweight Directory Access Protocol Version 3
[X.511] ITU-T Rec. X.511, "The Directory: Abstract Service
Definition", 1993.
[X.680] ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1) -
Specification of Basic Notation", 1994.
[X.690] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules:
Basic, Canonical, and Distinguished Encoding Rules", 1994.
[RFC1777] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory
Access Protocol", RFC 1777, March 1995.
[RFC1823] Howes, T., and M. Smith, "The LDAP Application Program
Interface", RFC 1823, August 1995.
[RFC2044] Yergeau, F., "UTF-8, a transformation format of Unicode
and ISO 10646", RFC 2044, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC2222] Meyers, J., "Simple Authentication and Security Layer",
RFC 2222, October 1997.
[RFC2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2252] Wahl, M., Coulbeck, A., Howes, T., and S. Kille,
"Lightweight Directory Access Protocol (v3): Attribute
Syntax Definitions", RFC 2252, December 1997.
[RFC2253] Kille, S., Wahl, M., and T. Howes, "Lightweight Directory
Access Protocol (v3): UTF-8 String Representation of
Distinguished Names", RFC 2253, December 1997.
[RFC2255] Howes, T., and M. Smith, "The LDAP URL Format", RFC 2255,
December 1997.
[RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[RFC2829] Wahl, M., Alvestrand, H., Hodges, J., and R. Morgan,
"Authentication Methods for LDAP", RFC 2829, May 2000
[RFC2830] Hodges, J., Morgan, R., and M. Wahl "Lightweight Directory
Access Protocol (v3): Extension for Transport Layer
Security", RFC 2830, May 2000
10. Editor's Address
Jim Sermersheim
Novell, Inc.
Sermersheim Internet-Draft - Expires Jan 2002 Page 38
Lightweight Directory Access Protocol Version 3
1800 South Novell Place
Provo, Utah 84606, USA
jimse@novell.com
+1 801 861-3088
Sermersheim Internet-Draft - Expires Jan 2002 Page 39
Lightweight Directory Access Protocol Version 3
Appendix A - Complete ASN.1 Definition
Lightweight-Directory-Access-Protocol-V3 DEFINITIONS
IMPLICIT TAGS ::=
BEGIN
LDAPMessage ::= SEQUENCE {
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
LDAPString ::= OCTET STRING
LDAPOID ::= OCTET STRING
LDAPDN ::= LDAPString
RelativeLDAPDN ::= LDAPString
AttributeType ::= LDAPString
AttributeDescription ::= LDAPString
AttributeDescriptionList ::= SEQUENCE OF
AttributeDescription
AttributeValue ::= OCTET STRING
AttributeValueAssertion ::= SEQUENCE {
Sermersheim Internet-Draft - Expires Jan 2002 Page 40
Lightweight Directory Access Protocol Version 3
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
Attribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
MatchingRuleId ::= LDAPString
LDAPResult ::= SEQUENCE {
resultCode ENUMERATED {
success (0),
operationsError (1),
protocolError (2),
timeLimitExceeded (3),
sizeLimitExceeded (4),
compareFalse (5),
compareTrue (6),
authMethodNotSupported (7),
strongAuthRequired (8),
-- 9 reserved --
referral (10), -- new
adminLimitExceeded (11), -- new
unavailableCriticalExtension (12), -- new
confidentialityRequired (13), -- new
saslBindInProgress (14), -- new
noSuchAttribute (16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation (19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
noSuchObject (32),
aliasProblem (33),
invalidDNSyntax (34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
invalidCredentials (49),
insufficientAccessRights (50),
busy (51),
unavailable (52),
unwillingToPerform (53),
loopDetect (54),
-- 55-63 unused --
namingViolation (64),
objectClassViolation (65),
notAllowedOnNonLeaf (66),
notAllowedOnRDN (67),
entryAlreadyExists (68),
Sermersheim Internet-Draft - Expires Jan 2002 Page 41
Lightweight Directory Access Protocol Version 3
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71), -- new
-- 72-79 unused --
other (80) },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
errorMessage LDAPString,
referral [3] Referral OPTIONAL }
Referral ::= SEQUENCE OF LDAPURL
LDAPURL ::= LDAPString -- limited to characters permitted in
-- URLs
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
BindRequest ::= [APPLICATION 0] SEQUENCE {
version INTEGER (1 .. 127),
name LDAPDN,
authentication AuthenticationChoice }
AuthenticationChoice ::= CHOICE {
simple [0] OCTET STRING,
-- 1 and 2 reserved
sasl [3] SaslCredentials }
SaslCredentials ::= SEQUENCE {
mechanism LDAPString,
credentials OCTET STRING OPTIONAL }
BindResponse ::= [APPLICATION 1] SEQUENCE {
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
UnbindRequest ::= [APPLICATION 2] NULL
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
Sermersheim Internet-Draft - Expires Jan 2002 Page 42
Lightweight Directory Access Protocol Version 3
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and [0] SET OF Filter,
or [1] SET OF Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- at least one must be present
substrings SEQUENCE OF CHOICE {
initial [0] AssertionValue,
any [1] AssertionValue,
final [2] AssertionValue } }
MatchingRuleAssertion ::= SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type [2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
SearchResultDone ::= [APPLICATION 5] LDAPResult
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::= SEQUENCE {
type AttributeDescription,
Sermersheim Internet-Draft - Expires Jan 2002 Page 43
Lightweight Directory Access Protocol Version 3
vals SET OF AttributeValue }
ModifyResponse ::= [APPLICATION 7] LDAPResult
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
AddResponse ::= [APPLICATION 9] LDAPResult
DelRequest ::= [APPLICATION 10] LDAPDN
DelResponse ::= [APPLICATION 11] LDAPResult
ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
CompareResponse ::= [APPLICATION 15] LDAPResult
AbandonRequest ::= [APPLICATION 16] MessageID
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
END
Sermersheim Internet-Draft - Expires Jan 2002 Page 44
Lightweight Directory Access Protocol Version 3
Appendix B - Change History
Changes made to RFC 2251:
B.1 Editorial
- Bibliography References: Changed all bibliography references to
use a long name form for readability.
- Changed occurrences of "unsupportedCriticalExtension"
"unavailableCriticalExtension"
- Fixed a small number of misspellings (mostly dropped letters).
B.2 Section 1
- Removed IESG note.
B.3 Section 9
- Added references to RFCs 1823, 2234, 2829 and 2830.
Changes made to draft-ietf-ldapbis-protocol-00.txt:
B.4 Section 4.1.6
- In the first paragraph, clarified what the contents of an
AttributeValue are. There was confusion regarding whether or not
an AttributeValue that is BER encoded (due to the "binary" option)
is to be wrapped in an extra OCTET STRING.
- To the first paragraph, added wording that doesn't restrict other
transfer encoding specifiers from being used. The previous wording
only allowed for the string encoding and the ;binary encoding.
- To the first paragraph, added a statement restricting multiple
options that specify transfer encoding from being present. This
was never specified in the previous version and was seen as a
potential interoperability problem.
- Added a third paragraph stating that the ;binary option is
currently the only option defined that specifies the transfer
encoding. This is for completeness.
B.5 Section 4.1.7
- Generalized the second paragraph to read "If an option specifying
the transfer encoding is present in attributeDesc, the
AssertionValue is encoded as specified by the option...".
Previously, only the ;binary option was mentioned.
B.6 Sections 4.2, 4.9, 4.10
- Added alias dereferencing specifications. In the case of modDN,
followed precedent set on other update operations (... alias is
not dereferenced...) In the case of bind and compare stated that
servers SHOULD NOT dereference aliases. Specifications were added
because they were missing from the previous version and caused
Sermersheim Internet-Draft - Expires Jan 2002 Page 45
Lightweight Directory Access Protocol Version 3
interoperability problems. Concessions were made for bind and
compare (neither should have ever allowed alias dereferencing) by
using SHOULD NOT language, due to the behavior of some existing
implementations.
B.7 Sections 4.5 and Appendix A
- Changed SubstringFilter.substrings.initial, any, and all from
LDAPString to AssertionValue. This was causing an incompatibility
with X.500 and confusion among other TS RFCs.
Changes made to draft-ietf-ldapbis-protocol-01.txt:
B.8 Section 3.4
- Reworded text surrounding subschemaSubentry to reflect that it is
a single-valued attribute that holds the schema for the root DSE.
Also noted that if the server masters entries that use differing
schema, each entry's subschemaSubentry attribute must be
interrogated. This may change as further fine-tuning is done to
the data model.
B.9 Section 4.1.12
- Specified that the criticality field is only used for requests and
not for unbind or abandon. Noted that it is ignored for all other
operations.
B.10 Section 4.2
- Noted that Server behavior is undefined when the name is a null
value, simple authentication is used, and a password is specified.
B.11 Section 4.2.(various)
- Changed "unauthenticated" to "anonymous" and "DN" and "LDAPDN" to
"name"
B.12 Section 4.2.2
- Changed "there is no authentication or encryption being performed
by a lower layer" to "the underlying transport service cannot
guarantee confidentiality"
B.13 Section 4.5.2
- Removed all mention of ExtendedResponse due to lack of
implementation.
Appendix C - Outstanding Work Items
C.1 Integrate result codes draft.
Sermersheim Internet-Draft - Expires Jan 2002 Page 46
Lightweight Directory Access Protocol Version 3
- The result codes draft should be reconciled with this draft.
Operation-specific instructions will reside with operations while
the error-specific sections will be added as an appendix.
C.2 Section 3.1
- Add "This also increases the complexity of clients in this
version." to fourth paragraph.
C.3 Section 4
- Remove "typically" from "and is typically transferred" in the
first paragraph.
- Change "MUST ignore elements of SEQUENCE encodings whose tags they
do not recognize" to "MUST ignore tagged elements of SEQUENCE
encodings that they do not recognize" in the first paragraph.
- Add "See Section 5.1 for information on mapping the LDAP protocol
to BER." to the first paragraph.
- Change "version 3 " to "version 3 or later" in the second
paragraph.
- Change "protocol version" to "protocol versions" in the third
paragraph.
- Change "version 2 may not provide this attribute." to "version 2
MAY NOT provide this attribute, or a root DSE." in the third
paragraph.
C.4 Section 4.1.1
- Change "the client may discard the PDU, or may abruptly close the
connection." to "the client MAY discard the PDU, or MAY abruptly
close the connection." in the fourth paragraph.
C.5 Section 4.1.1.1
- Add "If an unsolicited notification as described in section 4.4 is
sent from a server, the messageID value MUST be zero." to first
paragraph.
- Change "MUST have a value different" to "MUST have a non-zero
value different" in the second paragraph.
- Remove "or of the abandoned operation until it has received a
response from the server for another request invoked subsequent to
the abandonRequest," from the fourth paragraph as this imposes
synchronous behavior on the server.
C.6 Section 4.1.2
- Add ABNF for the textual representation of LDAPOID.
C.7 Section 4.1.4
- Change "This identifier may be written as decimal digits with
components separated by periods, e.g. "2.5.4.10"" to "may be
written as defined by ldapOID in section 4.1.2" in the second
paragraph.
Sermersheim Internet-Draft - Expires Jan 2002 Page 47
Lightweight Directory Access Protocol Version 3
- Add "Note that due to the restriction above, and due to this
allowance, servers MUST ensure that, within a controlling
subschema, no two attributes be named the same." to the fifth
paragraph.
- Resolve issue on list with the subject "Attribute Type character
set".
C.8 Section 4.1.5
- Change "A server may treat" to "A server MUST treat" in the second
to last paragraph.
- Change "A server MUST treat an AttributeDescription with any
options it does not implement as an unrecognized attribute type."
to "A server MUST treat an AttributeDescription with any options
it does not implement or support as an unrecognized attribute
type." in the second to last paragraph.
- Clarify the statement "An AttributeDescription with one or more
options is treated as a subtype of the attribute type without any
options". There is an unresolved thread titles "RFC 2596
questions" on the ietf-ldapext list regarding this.
C.9 Section 4.1.5.1
- Add "Servers SHOULD only return attributes with printable string
representations as binary when clients request binary transfer."
to the second paragraph.
- Clarify whether the "binary" attribute type option is to be
treated as a subtype.
C.10 Section 4.1.6
- Change "containing an encoded value of an AttributeValue data
type" to "containing an encoded attribute value data type"
C.11 Section 4.1.7
- Change "For all the string-valued user attributes described in
[5], the assertion value syntax is the same as the value syntax."
to "The assertion value syntax for all attributes using human-
readable syntaxes as described in [RFC2252] is the same as the
value syntax unless otherwise noted (an example being
objectIdentifierFirstComponentMatch)." in the third paragraph.
- Find out what the last sentence in third paragraph means (Clients
may use attributes...)
- Add a fourth paragraph: "Servers SHOULD NOT generate codes 81-90
as these are reserved for use by historical APIs [RFC 1823].
Later API specifications SHOULD avoid using the resultCode
enumeration to represent anything other than a protocol result
indication."
C.12 Section 4.1.8
- Change "when transferred in protocol" to "when transferred from
the server to the client" in the first paragraph.
Sermersheim Internet-Draft - Expires Jan 2002 Page 48
Lightweight Directory Access Protocol Version 3
C.12.1 Section 4.1.10
- Change "servers will return responses containing fields of type
LDAPResult" to "servers will return responses of LDAPResult or
responses containing the components of LDAPResponse"
- Drop '--new' from result codes.
C.13 Section 4.1.11
- Resolve the intent of "All the URLs MUST be equally capable of
being used to progress the operation" This is being discussed as
"Following referrals" on the list.
- Change "The referral error" to "The referral result code" in the
first paragraph.
- Change "It contains a reference to another server (or set of
servers)" to "It contains one or more references to one or more
servers or services" in the first paragraph.
- Add "after locating the target entry" to the first paragraph.
C.14 Section 4.1.12
- Change "The server MUST be prepared" to "The client and server
MUST be prepared" in the eighth paragraph
- Specify whether or not servers are to advertise the OIDs of known
response controls.
C.15 Section 4.2
- Change "LDAPDN" to "identity" in the definition of the name field.
- Rework definition of the name field to enumerate empty password and
name combinations. <Needs more work following discussion on list>
C.17 Section 4.2.2
- Add "as the authentication identity" to second paragraph.
C.18 Section 4.2.3
- Change "If the bind was successful, the resultCode will be
success, otherwise it will be one of" to "If the bind was
successful, the resultCode will be success, otherwise it MAY be
one of" in the third paragraph. <May need further refinement when
reconciled with resultCode draft>.
- Change "operationsError" to "other" as a result code.
- Change "If the client bound with the password choice" to "If the
client bound with the simple choice" in the last paragraph.
C.19 Section 4.3
- Change "a protocol client may assume that the protocol session is
terminated and MAY close the connection." to "a protocol client
MUST assume that the protocol session is terminated and MAY close
the connection." in the second paragraph.
Sermersheim Internet-Draft - Expires Jan 2002 Page 49
Lightweight Directory Access Protocol Version 3
- Change "a protocol server may assume" to "a protocol server MUST
assume" in the second paragraph.
- Change "and may close the connection" to "and MUST close the
connection" in the second paragraph.
C.20 Section 4.4
- Change "One unsolicited notification is defined" to "One
unsolicited notification (Notice of Disconnection) is defined" in
the third paragraph.
- Add "other than Notice of Disconnection" in the third paragraph.
- Add "Servers SHOULD NOT assume LDAPv3 clients understand or
recognize unsolicited notifications or unsolicited controls other
than Notice of Disconnection defined below. Servers SHOULD avoid
sending unsolicited notifications unless they know (by related
request or other means) that the client can make use of the
notification." as a fourth paragraph.
C.21 Section 4.5.1
- Make sure the use of "subordinates" in the derefInSearching
definition is correct. See "derefInSearching" on list.
- Change "checking for the existence of the objectClass attribute"
to "checking for the presence of the objectClass attribute" in the
last paragraph.
C.22 Section 4.5.2
- Change "Following all the SearchResultReference responses and all
SearchResultEntry responses to be returned by the server" to
"Following all the SearchResultReference responses,
SearchResultEntry responses, and ExtendedResponses to be returned
by the server" in the third paragraph.
- Add "associated with a search operation" to the sixth paragraph.
- Same problem as in C.5.
C.23 Section 4.5.3
- Add "Similarly, a server MUST NOT return a SearchResultReference
when the scope of the search is baseObject. If a client receives
such a SearchResultReference it MUST interpret is as a protocol
error and MUST NOT follow it." to the first paragraph.
- Add "If the scope part of the LDAP URL is present, the client MUST
use the new scope in its next request to progress the search. If
the scope part is absent the client MUST use subtree scope to
complete subtree searches and base scope to complete one level
searches." to the third paragraph.
- Remove "different" from "outstanding search operations to
different servers," in the fifth paragraph as they may be to the
same server.
C.24 Section 4.5.3.1
- Change examples to use dc naming.
Sermersheim Internet-Draft - Expires Jan 2002 Page 50
Lightweight Directory Access Protocol Version 3
C.25 Section 4.6
- Resolve the meaning of "and is ignored if the attribute does not
exist". See "modify: "non-existent attribute"" on the list.
- Change "clients MUST NOT attempt to delete" to "clients MUST NOT
attempt to add or delete" in the second to last paragraph.
- Change "using the "delete" form" to "using the "add" or "delete"
form" in the second to last paragraph.
C.26 Section 4.7
- Change "Clients MUST NOT supply the createTimestamp or
creatorsName attributes, since these will be generated
automatically by the server." to "Clients MUST NOT supply NO-USER-
MODIFICATION attributes such as createTimestamp or creatorsName
attributes, since these are provided by the server." in the
definition of the attributes field.
- Change examples to use dc naming.
- Clarify the paragraph that talks about structure rules. See
"discussing structure rules" on the list.
C.27 Section 4.10
- Specify what happens when the attr is missing vs. attr isn't in
schema. Also what happens if there's no equality matching rule.
C.28 Section 4.11
- Change "has been" to "will be" in the fourth paragraph.
- Change "(since these may have been in transit when the abandon was
requested)." to "(since these may either have been in transit when
the abandon was requested, or are not able to be abandoned)." in
the fifth paragraph.
- Add "Abandon and Unbind operations are not able to be abandoned.
Other operations, in particular update operations, or operations
that have been chained, may not be abandonable (or immediately
abandonable)." as the sixth paragraph.
C.29 Section 4.12
- Change "digitally signed operations and results" to "for instance
StartTLS [RFC2830]"
C.30 Section 5.1
- Add "control and extended operation values" to last paragraph. See
"LBER (BER Restrictions)" on list.
C.31 Section 5.2.1
- Add "using the BER-based described in section 5.1".
C.32 Section 6.1
Sermersheim Internet-Draft - Expires Jan 2002 Page 51
Lightweight Directory Access Protocol Version 3
- Add "that are used by those attributes" to the first paragraph.
- Add "Servers which support update operations MUST, and other
servers SHOULD, support strong authentication mechanisms described
in [RFC2829]." as a second paragraph.
- Add "Servers which provide access to sensitive information MUST,
and other servers SHOULD support privacy protections such as those
described in [RFC2829] and [RFC2830]." as a third paragraph.
C.33 Section 7
- Add "Servers which support update operations MUST, and other
servers SHOULD, support strong authentication mechanisms described
in [RFC2829]." as a fourth paragraph.
- Add "In order to automatically follow referrals, clients may need
to hold authentication secrets. This poses significant privacy and
security concerns and SHOULD be avoided." as a sixth paragraph.
- Add "This document provides a mechanism which clients may use to
discover operational attributes. Those relying on security by
obscurity should implement appropriate access controls to
restricts access to operational attributes per local policy." as
an eighth paragraph.
- Add "This document provides a mechanism which clients may use to
discover operational attributes. Those relying on security by
obscurity should implement appropriate access controls to
restricts access to operational attributes per local policy." as
an eighth paragraph.
Sermersheim Internet-Draft - Expires Jan 2002 Page 52
Lightweight Directory Access Protocol Version 3
Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Sermersheim Internet-Draft - Expires Jan 2002 Page 53