draft-ietf-ldapbis-protocol-xx.txt [plain text]
Internet-Draft Editor: J. Sermersheim
Intended Category: Standard Track Novell, Inc
Document: draft-ietf-ldapbis-protocol-27.txt Oct 2004
Obsoletes: RFCs 2251, 2830, 3771
LDAP: The Protocol
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society 2004. All Rights Reserved.
Abstract
This document describes the protocol elements, along with their
semantics and encodings, of the Lightweight Directory Access Protocol
(LDAP). LDAP provides access to distributed directory services that
act in accordance with X.500 data and service models. These protocol
elements are based on those described in the X.500 Directory Access
Protocol (DAP).
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Table of Contents
1. Introduction....................................................3
1.1. Relationship to Obsolete Specifications.......................3
2. Conventions.....................................................3
3. Protocol Model..................................................4
3.1 Operation and LDAP Exchange Relationship.......................4
4. Elements of Protocol............................................5
4.1. Common Elements...............................................5
4.1.1. Message Envelope............................................5
4.1.2. String Types................................................7
4.1.3. Distinguished Name and Relative Distinguished Name..........7
4.1.4. Attribute Descriptions......................................7
4.1.5. Attribute Value.............................................8
4.1.6. Attribute Value Assertion...................................8
4.1.7. Attribute and PartialAttribute..............................9
4.1.8. Matching Rule Identifier....................................9
4.1.9. Result Message..............................................9
4.1.10. Referral..................................................11
4.1.11. Controls..................................................12
4.2. Bind Operation...............................................14
4.3. Unbind Operation.............................................17
4.4. Unsolicited Notification.....................................17
4.5. Search Operation.............................................18
4.6. Modify Operation.............................................27
4.7. Add Operation................................................28
4.8. Delete Operation.............................................29
4.9. Modify DN Operation..........................................30
4.10. Compare Operation...........................................31
4.11. Abandon Operation...........................................32
4.12. Extended Operation..........................................32
4.13. IntermediateResponse Message................................34
4.13.1. Usage with LDAP ExtendedRequest and ExtendedResponse......34
4.13.2. Usage with LDAP Request Controls..........................35
4.14. StartTLS Operation..........................................35
5. Protocol Encoding, Connection, and Transfer....................37
5.2. Protocol Encoding............................................37
5.3. Transmission Control Protocol (TCP)..........................38
6. Security Considerations........................................38
7. Acknowledgements...............................................39
8. Normative References...........................................40
9. Informative References.........................................41
10. IANA Considerations...........................................42
11. Editor's Address..............................................42
Appendix A - LDAP Result Codes....................................43
A.1 Non-Error Result Codes........................................43
A.2 Result Codes..................................................43
Appendix B - Complete ASN.1 Definition............................48
Appendix C - Changes..............................................54
C.1 Changes made to RFC 2251:.....................................54
C.2 Changes made to RFC 2830:.....................................59
C.3 Changes made to RFC 3771:.....................................59
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1. Introduction
The Directory is "a collection of open systems cooperating to provide
directory services" [X.500]. A directory user, which may be a human
or other entity, accesses the Directory through a client (or
Directory User Agent (DUA)). The client, on behalf of the directory
user, interacts with one or more servers (or Directory System Agents
(DSA)). Clients interact with servers using a directory access
protocol.
This document details the protocol elements of the Lightweight
Directory Access Protocol (LDAP), along with their semantics.
Following the description of protocol elements, it describes the way
in which the protocol elements are encoded and transferred.
1.1. Relationship to Obsolete Specifications
This document is an integral part of the LDAP Technical Specification
[Roadmap] which obsoletes the previously defined LDAP technical
specification, RFC 3377, in its entirety.
This document obsoletes all of RFC 2251 except the following:
Sections 3.2, 3.4, 4.1.3 (last paragraph), 4.1.4, 4.1.5, 4.1.5.1,
4.1.9 (last paragraph), 5.1, 6.1, and 6.2 (last paragraph) are
obsoleted by [Models].
Section 3.3 is obsoleted by [Roadmap].
Sections 4.2.1 (portions), and 4.2.2 are obsoleted by [AuthMeth].
Appendix C.1 summarizes substantive changes to the remaining
sections.
This document obsoletes RFC 2830, Sections 2 and 4 in entirety. The
remainder of RFC 2830 is obsoleted by [AuthMeth]. Appendix C.2
summarizes substantive changes to the remaining sections.
This document also obsoletes RFC 3771 in entirety.
2. Conventions
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 [Keyword].
Character names in this document use the notation for code points and
names from the Unicode Standard [Unicode]. For example, the letter
"a" may be represented as either <U+0061> or <LATIN SMALL LETTER A>.
Note: a glossary of terms used in Unicode can be found in [Glossary].
Information on the Unicode character encoding model can be found in
[CharModel].
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The term "connection" refers to the underlying transport service used
to carry the protocol exchange.
The term "LDAP exchange" refers to the layer where LDAP PDUs are
exchanged between protocol peers.
The term "TLS layer" refers to a layer inserted between the
connection and the LDAP exchange that utilizes Transport Layer
Security ([TLS]) to protect the exchange of LDAP PDUs.
The term "SASL layer" refers to a layer inserted between the
connection and the LDAP exchange that utilizes Simple Authentication
and Security Layer ([SASL]) to protect the exchange of LDAP PDUs.
See the table in Section 5 for an illustration of these four terms.
3. 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 an
operation, the server typically returns a response containing
appropriate data to the requesting client.
Protocol operations are generally independent of one another. Each
operation is processed as an atomic action, leaving the directory in
a consistent state.
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 generally may be
exchanged between a client and server in any order. If required,
synchronous behavior may be controlled by client applications.
The core protocol operations defined in this document can be mapped
to a subset of the X.500 (1993) Directory Abstract Service [X.511].
However there is not a one-to-one mapping between LDAP operations and
X.500 Directory Access Protocol (DAP) operations. Server
implementations acting as a gateway to X.500 directories may need to
make multiple DAP requests to service a single LDAP request.
3.1 Operation and LDAP Exchange Relationship
Protocol operations are tied to an LDAP exchange. When the connection
is closed, any uncompleted operations tied to the LDAP exchange are,
when possible, abandoned, and when not possible, completed without
transmission of the response. Also, when the connection is closed,
the client MUST NOT assume that any uncompleted update operations
tied to the LDAP exchange have succeeded or failed.
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4. Elements of Protocol
The protocol is described using Abstract Syntax Notation One
([ASN.1]), and is transferred using a subset of ASN.1 Basic Encoding
Rules ([BER]). Section 5 specifies how the protocol elements are
encoded and transferred.
In order to support future extensions to this protocol, extensibility
is implied where it is allowed per ASN.1 (i.e. sequence, set, choice,
and enumerated types are extensible). In addition, ellipses (...)
have been supplied in ASN.1 types that are explicitly extensible as
discussed in [LDAPIANA]. Because of the implied extensibility,
clients and servers MUST (unless otherwise specified) ignore trailing
SEQUENCE components whose tags they do not recognize.
Changes to the protocol other than through the extension mechanisms
described here require a different version number. A client indicates
the version it is using as part of the bind request, described in
Section 4.2. If a client has not sent a bind, the server MUST assume
the client is using version 3 or later.
Clients may determine the protocol versions a server supports by
reading the 'supportedLDAPVersion' attribute from the root DSE (DSA-
Specific Entry) [Models].
4.1. Common Elements
This section describes the LDAPMessage envelope Protocol Data Unit
(PDU) 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,
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addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse,
...,
intermediateResponse IntermediateResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
The ASN.1 type Controls is defined in Section 4.1.11.
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 messageID 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 SHOULD return the Notice of Disconnection
described in Section 4.4.1, with the resultCode set to protocolError,
and MUST immediately close the connection.
In other cases where the client or server cannot parse a PDU, it
SHOULD abruptly close the connection where further communication
(including providing notice) would be pernicious. Otherwise, server
implementations MUST return an appropriate response to the request,
with the resultCode set to protocolError.
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 non-zero value different from
the the messageID of any other uncompleted requests in the LDAP
exchange. The zero value is reserved for the unsolicited notification
message.
Typical clients increment a counter for each request.
A client MUST NOT send a request with the same message ID as an
earlier request in the same LDAP exchange unless it can be determined
that the server is no longer servicing the earlier request (e.g.
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after the final response is received, or a subsequent bind
completes). Otherwise the behavior is undefined. For this purpose,
note that abandon and abandoned operations do not send responses.
4.1.2. String Types
The LDAPString is a notational convenience to indicate that, although
strings of LDAPString type encode as ASN.1 OCTET STRING types, the
[ISO10646] character set (a superset of [Unicode]) is used, encoded
following the [UTF-8] algorithm. Note that Unicode characters U+0000
through U+007F are the same as ASCII 0 through 127, respectively, and
have the same single octet UTF-8 encoding. Other Unicode characters
have a multiple octet UTF-8 encoding.
LDAPString ::= OCTET STRING -- UTF-8 encoded,
-- [ISO10646] characters
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. Although an LDAPOID is
encoded as an OCTET STRING, values are limited to the definition of
<numericoid> given in Section 1.4 of [Models].
LDAPOID ::= OCTET STRING -- Constrained to <numericoid> [Models]
For example,
1.3.6.1.4.1.1466.1.2.3
4.1.3. Distinguished Name and Relative Distinguished Name
An LDAPDN is defined to be the representation of a Distinguished Name
(DN) after encoding according to the specification in [LDAPDN].
LDAPDN ::= LDAPString
-- Constrained to <distinguishedName> [LDAPDN]
A RelativeLDAPDN is defined to be the representation of a Relative
Distinguished Name (RDN) after encoding according to the
specification in [LDAPDN].
RelativeLDAPDN ::= LDAPString
-- Constrained to <name-component> [LDAPDN]
4.1.4. Attribute Descriptions
The definition and encoding rules for attribute descriptions are
defined in Section 2.5 of [Models]. Briefly, an attribute description
is an attribute type and zero or more options.
AttributeDescription ::= LDAPString
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-- Constrained to <attributedescription>
-- [Models]
4.1.5. Attribute Value
A field of type AttributeValue is an OCTET STRING containing an
encoded attribute value. The attribute value is encoded according to
the LDAP-specific encoding definition of its corresponding syntax.
The LDAP-specific encoding definitions for different syntaxes and
attribute types may be found in other documents and in particular
[Syntaxes].
AttributeValue ::= OCTET STRING
Note that there is no defined limit on the size of this encoding;
thus protocol values may include multi-megabyte attribute values
(e.g. photographs).
Attribute values may be defined which have arbitrary and non-
printable syntax. Implementations MUST NOT display nor attempt to
decode an attribute value if its syntax is not known. The
implementation may attempt to discover the subschema of the source
entry, and retrieve the descriptions of 'attributeTypes' from it
[Models].
Clients MUST only send attribute values in a request that are valid
according to the syntax defined for the attributes.
4.1.6. Attribute Value Assertion
The AttributeValueAssertion (AVA) type definition is similar to the
one in the X.500 Directory standards. It contains an attribute
description and a matching rule ([Models Section 4.1.3) assertion
value suitable for that type. Elements of this type are typically
used to assert that the value in assertionValue matches a value of an
attribute.
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
The syntax of the AssertionValue depends on the context of the LDAP
operation being performed. For example, the syntax of the EQUALITY
matching rule for an attribute is used when performing a Compare
operation. Often this is the same syntax used for values of the
attribute type, but in some cases the assertion syntax differs from
the value syntax. See objectIdentiferFirstComponentMatch in
[Syntaxes] for an example.
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4.1.7. Attribute and PartialAttribute
Attributes and partial attributes consist of an attribute description
and attribute values. A PartialAttribute allows zero values, while
Attribute requires at least one value.
PartialAttribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF value AttributeValue }
Attribute ::= PartialAttribute(WITH COMPONENTS {
...,
vals (SIZE(1..MAX))})
No two attribute values may be equivalent as described by Section 2.3
of [Models]. The set of attribute values is unordered.
Implementations MUST NOT rely upon the ordering being repeatable.
4.1.8. Matching Rule Identifier
Matching rules are defined in Section 4.1.3 of [Models]. A matching
rule is identified in the protocol by the printable representation of
either its <numericoid>, or one of its short name descriptors
[Models], e.g. 'caseIgnoreMatch' or '2.5.13.2'.
MatchingRuleId ::= LDAPString
4.1.9. Result Message
The LDAPResult is the construct used in this protocol to return
success or failure indications from servers to clients. To various
requests, servers will return responses of LDAPResult or responses
containing the components of 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),
adminLimitExceeded (11),
unavailableCriticalExtension (12),
confidentialityRequired (13),
saslBindInProgress (14),
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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),
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71),
-- 72-79 unused --
other (80),
... },
matchedDN LDAPDN,
diagnosticMessage LDAPString,
referral [3] Referral OPTIONAL }
The resultCode enumeration is extensible as defined in Section 3.6 of
[LDAPIANA]. The meanings of the listed result codes are given in
Appendix A. If a server detects multiple errors for an operation,
only one result code is returned. The server should return the result
code that best indicates the nature of the error encountered.
The diagnosticMessage 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) diagnostic message. As this diagnostic message is not
standardized, implementations MUST NOT rely on the values returned.
If the server chooses not to return a textual diagnostic, the
diagnosticMessage field MUST be empty.
For certain result codes (typically, but not restricted to
noSuchObject, aliasProblem, invalidDNSyntax and
aliasDereferencingProblem), the matchedDN field is set (subject to
access controls) to the name of the last entry (object or alias) used
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in finding the target (or base) object. 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].
Otherwise the matchedDN field is empty.
4.1.10. Referral
The referral result code indicates that the contacted server cannot
or will not perform the operation and that one or more other servers
may be able to. Reasons for this include:
- The target entry of the request is not held locally, but the
server has knowledge of its possible existence elsewhere.
- The operation is restricted on this server -- perhaps due to a
read-only copy of an entry to be modified.
The referral field is present in an LDAPResult if the resultCode
field value is referral, and absent with all other result codes. It
contains one or more references to one or more servers or services
that may be accessed 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 URI MUST be
present in the Referral.
During a search operation, after the baseObject is located, and
entries are being evaluated, the referral is not returned. Instead,
continuation references, described in Section 4.5.3, are returned
when other servers would need to be contacted to complete the
operation.
Referral ::= SEQUENCE SIZE (1..MAX) OF uri URI
URI ::= LDAPString -- limited to characters permitted in
-- URIs
If the client wishes to progress the operation, it MUST follow the
referral by contacting one of the supported services. If multiple
URIs are present, the client assumes that any supported URI may be
used to progress the operation.
Protocol peers that follow 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 implementations use a counter that is incremented
each time referral handling occurs for an operation, and these kinds
of implementations MUST be able to handle at least ten nested
referrals between the root and a leaf entry.
A URI for a server implementing LDAP and accessible via [TCP]/[IP]
(v4 or v6) is written as an LDAP URL according to [LDAPURL].
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When an LDAP URL is used, the following instructions are followed:
- If an alias was dereferenced, the <dn> part of the URL MUST be
present, with the new target object name. UTF-8 encoded characters
appearing in the string representation of a DN or search filter
may not be legal for URLs (e.g. spaces) and MUST be escaped using
the % method in [URI].
- It is RECOMMENDED that the <dn> part be present to avoid
ambiguity.
- 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 URL of a referral for a search
operation.
- If the <filter> part of the LDAP URL is present, 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.
- For search, it is RECOMMENDED that the <scope> part be present to
avoid ambiguity.
- If the <scope> part is missing, the scope of the original search
is used by the client to progress the operation.
- Other aspects of the new request may be the same as or different
from the request which generated the referral.
Other kinds of URIs may be returned. The syntax and semantics of such
URIs is left to future specifications. Clients may ignore URIs that
they do not support.
4.1.11. Controls
Controls provide a mechanism whereby the semantics and arguments of
existing LDAP operations may be extended. One or more controls may be
attached to a single LDAP message. A control only affects the
semantics of the message it is attached to.
Controls sent by clients are termed 'request controls' and those sent
by servers are termed 'response controls'.
Controls ::= SEQUENCE OF control Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
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The controlType field is the dotted-decimal representation of an
OBJECT IDENTIFIER which uniquely identifies the control. This
provides unambiguous naming of controls. Often, response control(s)
solicited by a request control share controlType values with the
request control.
The criticality field only has meaning in controls attached to
request messages (except unbindRequest). For controls attached to
response messages and the unbindRequest, the criticality field SHOULD
be FALSE, and MUST be ignored by the receiving protocol peer. A value
of TRUE indicates that it is unacceptable to perform the operation
without applying the semantics of the control and FALSE otherwise.
Specifically, the criticality field is applied as follows:
- Regardless of the value of the criticality field, if the server
recognizes the control type and it is appropriate for the
operation, the server is to 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 for operations that
have a response message, MUST return unavailableCriticalExtension
in the resultCode.
- If the server does not recognize the control type or it is not
appropriate for the operation, and the criticality field is FALSE,
the server MUST ignore the control.
The controlValue may contain information associated with the
controlType. Its format is defined by the specification of the
control. Implementations 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. When a controlValue is defined in terms
of ASN.1, and BER encoded according to Section 5.2, it also follows
the extensibility rules in Section 4.
Servers list the controlType of request controls they recognize in
the 'supportedControl' attribute in the root DSE (Section 5.1 of
[Models]).
Controls SHOULD NOT be combined unless the semantics of the
combination has been specified. The semantics of control
combinations, if specified, are generally found in the control
specification most recently published. When a combination of controls
is encountered whose semantics are invalid, not specified (or not
known), the message is considered to be not well-formed, thus the
operation fails with protocolError. Additionally, unless order-
dependent semantics are given in a specification, the order of a
combination of controls in the SEQUENCE is ignored. Where the order
is to be ignored but cannot be ignored by the server, the message is
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considered not well-formed and the operation fails with
protocolError.
This document does not specify any controls. Controls may be
specified in other documents. Documents detailing control extensions
are to provide for each control:
- the OBJECT IDENTIFIER assigned to the control,
- direction as to what value the sender should provide for the
criticality field (note: the semantics of the criticality field
are defined above should not be altered by the control's
specification),
- whether information is to be present in the controlValue field,
and if so, the format of the controlValue contents,
- the semantics of the control, and
- optionally, semantics regarding the combination of the control
with other controls.
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
operation should be thought of as the "authenticate" operation.
Operational, authentication, and security-related semantics of this
operation are given in [AuthMeth].
The Bind Request is defined as follows:
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 }
Fields of the Bind Request are:
- version: A version number indicating the version of the protocol
to be used for the LDAP exchange. This document describes version
3 of the protocol. There is no version negotiation. The client
sets this field to the version it desires. If the server does not
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support the specified version, it MUST respond with protocolError
in the resultCode field of the BindResponse.
- name: If not empty, 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
([AuthMeth] Section 5.1) or when using Simple Authentication and
Security Layer [SASL] authentication ([AuthMeth] Section 3.3.2).
Where the server attempts to locate the named object, it SHALL NOT
perform alias dereferencing.
- authentication: information used in authentication. This type is
extensible as defined in Section 3.7 of [LDAPIANA]. Servers that
do not support a choice supplied by a client return
authMethodNotSupported in the resultCode field of the
BindResponse.
Textual passwords (consisting of a character sequence with a known
character set and encoding) transferred to the server using the
simple AuthenticationChoice SHALL be transferred as [UTF-8]
encoded [Unicode]. Prior to transfer, clients SHOULD prepare text
passwords by applying the [SASLprep] profile of the [Stringprep]
algorithm. Passwords consisting of other data (such as random
octets) MUST NOT be altered. The determination of whether a
password is textual is a local client matter.
Authorization is the decision of which access an operation has to the
directory. Among other things, the process of authorization takes as
input authentication information obtained during the bind operation
and/or other acts of authentication (such as lower layer security
services).
4.2.1. Processing of the Bind Request
Before processing a BindRequest, all uncompleted operations MUST
either complete or be abandoned. The server may either wait for the
uncompleted operations to complete, or abandon them. The server then
proceeds to authenticate the client in either a single-step, or
multi-step bind process. Each step requires the server to return a
BindResponse to indicate the status of authentication.
After sending a BindRequest, clients MUST NOT send further LDAP PDUs
until receiving the BindResponse. Similarly, servers SHOULD NOT
process or respond to requests received while processing a
BindRequest.
If the client did not bind before sending a request and receives an
operationsError to that request, it may then send a Bind Request. If
this also fails or the client chooses not to bind on the existing
LDAP exchange, it may 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.
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Clients may send multiple Bind Requests on an LDAP exchange to change
the authentication and/or security associations or to complete a
multi-stage bind process. Authentication from earlier binds is
subsequently ignored.
For some SASL authentication mechanisms, it may be necessary for the
client to invoke the BindRequest multiple times ([AuthMeth] Section
8.2). Clients MUST NOT invoke operations between two Bind Requests
made as part of a multi-stage bind.
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.
4.2.2. 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.
A successful bind operation is indicated by a BindResponse with a
resultCode set to success. Otherwise, an appropriate result code is
set in the BindResponse. For bind, the protocolError result code may
be used to indicate that the version number supplied by the client is
unsupported.
If the client receives a BindResponse where the resultCode field is
protocolError, it is to assume that the server does not support this
version of LDAP. While the client may be able proceed with another
version of this protocol (this may or may not require closing and re-
establishing the connection), how to proceed with another version of
this protocol is beyond the scope of this document. Clients which are
unable or unwilling to proceed SHOULD close the connection.
The serverSaslCreds field is 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 simple choice, or the SASL mechanism
does not require the server to return information to the client, then
this field SHALL NOT be included in the BindResponse.
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4.3. Unbind Operation
The function of the Unbind Operation is to terminate an LDAP exchange
and close the connection. The Unbind operation is not the antithesis
of the Bind operation as the name implies. The naming of these
operations is historical. The Unbind operation should be thought of
as the "quit" operation.
The Unbind Operation is defined as follows:
UnbindRequest ::= [APPLICATION 2] NULL
The Unbind Operation has no response defined. Upon transmission of
the UnbindRequest, each protocol peer is to consider the LDAP
exchange terminated, MUST cease transmission of messages to the other
peer, and MUST close the connection. Uncompleted operations are
handled as specified in Section 5.1.
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 LDAP exchange or 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 zero and protocolOp is of the extendedResp form (See
Section 4.12). The responseName field of the ExtendedResponse always
contains an LDAPOID which is unique for this notification.
One unsolicited notification (Notice of Disconnection) is defined in
this document. The specification of an unsolicited notification
consists of:
- the OBJECT IDENTIFIER assigned to the notification (to be
specified in the responseName,
- the format of the contents (if any) of the responseValue,
- the circumstances which will cause the notification to be
returned, and
- the semantics of the operation.
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. This notification is intended to assist clients in
distinguishing between an error condition and a transient network
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failure. Note that this notification is not a response to an unbind
requested by the client. Uncompleted operations are handled as
specified in Section 5.1.
The responseName is 1.3.6.1.4.1.1466.20036, the responseValue field
is absent, and the resultCode is used to indicate the reason for the
disconnection.
Upon transmission of the Notice of Disconnection, the server is to
consider the LDAP exchange terminated, MUST cease transmission of
messages to the client, and MUST close the connection.
4.5. Search Operation
The Search Operation is used to request a server to return, subject
to access controls and other restrictions, a set of entries matching
a complex search criterion. This can be used to read attributes from
a single entry, from entries immediately subordinate to 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 AttributeSelection }
AttributeSelection ::= SEQUENCE OF selector LDAPString
-- The LDAPString is constrained to
-- <attributeSelector> below
Filter ::= CHOICE {
and [0] SET OF filter Filter,
or [1] SET OF filter Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
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lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- initial and final can occur at most once
substrings SEQUENCE SIZE (1..MAX) OF substring 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 }
Fields of the Search Request are:
- baseObject: The name of the base object entry relative to which
the search is to be performed.
- scope: Specifies the scope of the search to be performed. The
semantics (as described in [X.511]) of the possible values of this
field are:
baseObject: The scope is constrained to the entry named by
baseObject.
singleLevel: The scope is constrained to the immediate
subordinates of the entry named by baseObject.
wholeSubtree: the scope is constrained to the entry named by
the baseObject, and all its subordinates.
- derefAliases: An indicator as to how alias entries (as defined in
[Models]) 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: While searching, dereference any alias entry
subordinate to the base object which is also in the search
scope. The filter is applied to the dereferenced object(s). If
the search scope is wholeSubtree, the search continues in the
subtree of any dereferenced object. Aliases in that subtree are
also dereferenced. Servers SHOULD eliminate duplicate entries
that arise due to alias dereferencing while searching.
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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.
Servers MUST detect looping while dereferencing aliases in order
to prevent denial of service attacks of this nature.
- sizeLimit: A size limit that restricts the maximum number of
entries to be returned as a result of the search. A value of zero
in this field indicates that no client-requested size limit
restrictions are in effect for the search. Servers may also
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 zero in this field
indicates that no client-requested time limit restrictions are in
effect for the search. Servers may also enforce a maximum time
limit for the search.
- typesOnly: An indicator as to whether search results are to
contain both attribute descriptions and values, or just attribute
descriptions. Setting this field to TRUE causes only attribute
descriptions (no values) to be returned. Setting this field to
FALSE causes both attribute descriptions 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.
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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 matching rule for equalityMatch filter items is defined by the
EQUALITY matching rule for the attribute type.
There SHALL be at most one 'initial', and at most one 'final' in
the 'substrings' of a SubstringFilter. If 'initial' is present, it
SHALL be the first element of 'substrings'. If 'final' is present,
it SHALL be the last element of 'substrings'.
The matching rule for AssertionValues in a substrings filter item
is defined by the SUBSTR matching rule for the attribute type.
Note that the AssertionValue in a substrings filter item conforms
to the assertion syntax of the EQUALITY matching rule for the
attribute type rather than the assertion syntax of the SUBSTR
matching rule for the attribute type. Conceptually, the entire
SubstringFilter is converted into an assertion value of the
substrings matching rule prior to applying the rule.
The matching rule for the greaterOrEqual filter item is defined by
the ORDERING and EQUALITY matching rules for the attribute type.
The matching rule for the lessOrEqual filter item is defined by
the ORDERING matching rule for the attribute type.
An approxMatch filter item evaluates to TRUE when there is a value
of the attribute or subtype for which some locally-defined
approximate matching algorithm (e.g. spelling variations, phonetic
match, etc.) returns TRUE. If an item matches for equality, it
also satisfies an approximate match. If approximate matching is
not supported for the attribute, this filter item should be
treated as an equalityMatch.
An extensibleMatch filter item is evaluated as follows:
If the matchingRule field is absent, the type field MUST be
present, and an equality match is performed for that type.
If the type field is absent and the matchingRule is present, the
matchValue is compared against all attributes in an entry which
support that matchingRule. The matchingRule determines the
syntax for the assertion value. The filter item evaluates to
TRUE if it matches 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 is invalid.
If the type field is present and the matchingRule is present,
the matchValue is compared against entry attributes of the
specified type. In this case, the matchingRule MUST be one
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suitable for use with the specified type (see [Syntaxes]),
otherwise the filter item is Undefined.
If the dnAttributes field is set to TRUE, the match is
additionally applied against all the AttributeValueAssertions in
an entry's distinguished name, and evaluates to TRUE if there is
at least one attribute in the distinguished name for which the
filter item evaluates to TRUE. The dnAttributes field is present
to alleviate the need for multiple versions of generic matching
rules (such as word matching), where one applies to entries and
another applies 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.
Examples include:
- An attribute description in an equalityMatch, substrings,
greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch
filter is not recognized by the server.
- The attribute type does not define the appropriate matching
rule.
- A MatchingRuleId in the extensibleMatch is not recognized by
the server or is not valid for the attribute type.
- The type of filtering requested is not implemented.
- The assertion value is invalid.
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
each evaluate to Undefined.
Servers MUST NOT return errors if attribute descriptions or
matching rule ids are not recognized, assertion values are
invalid, or the assertion syntax is not supported. More details of
filter processing are given in Section 7.8 of [X.511].
- attributes: A selection list of the attributes to be returned from
each entry which matches the search filter. LDAPString values of
this field are constrained to the following Augmented Backus-Naur
Form ([ABNF]):
attributeSelector = attributedescription / selectorpecial
selectorspecial = noattrs / alluserattrs
noattrs = %x31.2E.31 ; "1.1"
alluserattrs = %x2A ; asterisk ("*")
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The <attributedescription> production is defined in Section 2.5 of
[Models].
There are three special cases which may appear in the attributes
selection list:
- an empty list with no attributes,
- a list containing "*" (with zero or more attribute
descriptions), and
- a list containing only "1.1".
An empty list requests the return of all user attributes.
A list containing "*" requests the return of all user attributes
in addition to other listed (operational) attributes.
A list containing only the OID "1.1" indicates that no attributes
are to be returned. If "1.1" is provided with other
attributeSelector values, the "1.1" attributeSelector is ignored.
This OID was chosen because it does not (and can not) correspond
to any attribute in use.
Client implementors should note that even if all user attributes
are requested, some attributes and/or attribute values of the
entry may not be included in search results due to access controls
or other restrictions. Furthermore, servers will not return
operational attributes, such as objectClasses or attributeTypes,
unless they are listed by name. Operational attributes are
described in [Models].
Attributes are returned at most once in an entry. If an attribute
description is named more than once in the list, the subsequent
names are ignored. If an attribute description in the list is not
recognized, it is ignored by the server.
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 presence 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, it must provide the
same semantics as the X.500 search operation.
4.5.2. Search Result
The results of the search operation are returned as zero or more
searchResultEntry messages, zero or more SearchResultReference
messages, followed by a single searchResultDone message.
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
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objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF
partialAttribute PartialAttribute
-- Note that the PartialAttributeList may hold zero elements.
-- This may happen when none of the attributes of an entry
-- were requested, or could be returned.
-- Note also that the partialAttribute vals set may hold zero
-- elements. This may happen when typesOnly is requested, access
-- controls prevent the return of values, or other reasons.
SearchResultReference ::= [APPLICATION 19] SEQUENCE
SIZE (1..MAX) OF uri URI
SearchResultDone ::= [APPLICATION 5] LDAPResult
Each SearchResultEntry represents an entry found during the search.
Each SearchResultReference represents an area not yet explored during
the search. The SearchResultEntry and SearchResultReference PDUs may
come in any order. Following all the SearchResultReference and
SearchResultEntry responses, the server returns a SearchResultDone
response, which contains an indication of success, or detailing any
errors that have occurred.
Each entry returned in a SearchResultEntry will contain all
appropriate attributes 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 constructed by the server and appear in a
SearchResultEntry attribute list, although they are not stored
attributes of an entry. Clients SHOULD NOT assume that all attributes
can be modified, even if permitted by access control.
If the server's schema defines short names [Models] for an attribute
type then the server SHOULD use one of those names in attribute
descriptions for that attribute type (in preference to using the
<numericoid> [Models] format of the attribute type's object
identifier). The server SHOULD NOT use the short name if that name is
known by the server to be ambiguous, or otherwise likely to cause
interoperability problems.
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 one or more non-local entries,
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 either a
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referral or noSuchObject result code (depending on the server's
knowledge of the entry named in the baseObject).
If a server holds a copy or partial copy of the subordinate naming
context [Section 5 of Models], it may use the search filter to
determine whether or not to return a SearchResultReference response.
Otherwise SearchResultReference responses are always returned when in
scope.
The SearchResultReference is of the same data type as the Referral.
A URI for a server implementing LDAP and accessible via [TCP]/[IP]
(v4 or v6) is written as an LDAP URL according to [LDAPURL].
In order to complete the search, the client issues 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 the LDAP exchange between a client and
server. The client must abandon subsequent search operations it
wishes to individually.
Clients that follow search continuation references 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 use a counter that is incremented each
time search result reference handling occurs for an operation, and
these kinds of clients MUST be able to handle at least ten nested
search result references between the root and a leaf entry.
When an LDAP URL is used, the following instructions are followed:
- The <dn> part of the URL MUST be present, with the new target
object name. The client MUST use this name when following the
reference. UTF-8 encoded characters appearing in the string
representation of a DN or search filter may not be legal for URLs
(e.g. spaces) and MUST be escaped using the % method in [URI].
- Some servers (e.g. participating in distributed indexing) may
provide a different filter in a URL of a SearchResultReference.
- If the <filter> part of the URL is present, 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.
- If the originating search scope was singleLevel, the <scope> part
of the URL will be "base".
- It is RECOMMENDED that the <scope> part be present to avoid
ambiguity.
- Other aspects of the new search request may be the same as or
different from the search request which generated the
SearchResultReference.
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- The name of an unexplored subtree in a SearchResultReference need
not be subordinate to the base object.
Other kinds of URIs may be returned. The syntax and semantics of such
URIs is left to future specifications. Clients may ignore URIs that
they do not support.
4.5.3.1. Examples
For example, suppose the contacted server (hosta) holds the entry
<DC=Example,DC=NET> and the entry <CN=Manager,DC=Example,DC=NET>. It
knows that either LDAP-capable servers (hostb) or (hostc) hold
<OU=People,DC=Example,DC=NET> (one is the master and the other server
a shadow), and that LDAP-capable server (hostd) holds the subtree
<OU=Roles,DC=Example,DC=NET>. If a wholeSubtree search of
<DC=Example,DC=NET> is requested to the contacted server, it may
return the following:
SearchResultEntry for DC=Example,DC=NET
SearchResultEntry for CN=Manager,DC=Example,DC=NET
SearchResultReference {
ldap://hostb/OU=People,DC=Example,DC=NET??sub
ldap://hostc/OU=People,DC=Example,DC=NET??sub }
SearchResultReference {
ldap://hostd/OU=Roles,DC=Example,DC=NET??sub }
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,DC=Example,DC=NET>, the server might respond as follows:
SearchResultEntry for OU=People,DC=Example,DC=NET
SearchResultReference {
ldap://hoste/OU=Managers,OU=People,DC=Example,DC=NET??sub }
SearchResultReference {
ldap://hostf/OU=Consultants,OU=People,DC=Example,DC=NET??sub }
SearchResultDone (success)
Similarly, if a singleLevel search of <DC=Example,DC=NET> is
requested to the contacted server, it may return the following:
SearchResultEntry for CN=Manager,DC=Example,DC=NET
SearchResultReference {
ldap://hostb/OU=People,DC=Example,DC=NET??base
ldap://hostc/OU=People,DC=Example,DC=NET??base }
SearchResultReference {
ldap://hostd/OU=Roles,DC=Example,DC=NET??base }
SearchResultDone (success)
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If the contacted server does not hold the base object for the search,
but has knowledge of its possible location, then it may return a
referral to the client. In this case, if the client requests a
subtree search of <DC=Example,DC=ORG> to hosta, the server returns a
SearchResultDone containing a referral.
SearchResultDone (referral) {
ldap://hostg/DC=Example,DC=ORG??sub }
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:
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
changes SEQUENCE OF change SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification PartialAttribute } }
Fields of the Modify Request are:
- object: The name of the object to be modified. The value of this
field contains the DN of the entry to be modified. The server
SHALL NOT perform any alias dereferencing in determining the
object to be modified.
- changes: A list of modifications to be performed on the entry. The
entire list of modifications MUST be performed in the order they
are listed as a single atomic operation. While individual
modifications may violate certain aspects of the directory schema
(such as the object class definition and DIT content rule), the
resulting entry after the entire list of modifications is
performed MUST conform to the requirements of the directory model
and controlling schema [Models].
- operation: Used to specify the type of modification being
performed. Each operation type acts on the following
modification. The values of this field have the following
semantics respectively:
add: add values listed to the modification attribute,
creating the attribute if necessary;
delete: delete values listed from the modification attribute,
removing the entire attribute if no values are listed, or if
all current values of the attribute are listed for deletion;
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replace: replace all existing values of the modification
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.
- modification: A PartialAttribute (which may have an empty SET
of vals) used to hold the attribute type or attribute type and
values being modified.
Upon receipt of a Modify Request, the server attempts to perform the
necessary modifications to the DIT and returns the result in a Modify
Response, defined as follows:
ModifyResponse ::= [APPLICATION 7] LDAPResult
The server will return to the client a single Modify Response
indicating either the successful completion of the DIT modification,
or the reason that the modification failed. 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. The result of the modification is indeterminate if the
Modify Response is not received (e.g. the LDA exchange is terminated
or the Modify Operation is abandoned).
The Modify Operation cannot be used to remove from an entry any of
its distinguished values, i.e. those values which form the entry's
relative distinguished name. An attempt to do so will result in the
server returning the notAllowedOnRDN result code. The Modify DN
Operation described in Section 4.9 is used to rename an entry.
Note that due to the simplifications made in LDAP, there is not a
direct mapping of the changes in an LDAP ModifyRequest onto the
changes 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 attribute Attribute
Fields of the Add Request are:
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- entry: the name of the entry to be added. The server SHALL NOT
dereference any aliases in locating the entry to be added.
- attributes: the list of attributes that, along with those from the
RDN, make up the content of the entry being added. Clients MAY or
MAY NOT include the RDN attribute in this list. Clients MUST
include the 'objectClass' attribute, and values of any mandatory
attributes of the listed object classes. Clients MUST NOT supply
NO-USER-MODIFICATION attributes such as the createTimestamp or
creatorsName attributes, since the server maintains these
automatically.
The entry named in the entry field of the AddRequest MUST NOT exist
for the AddRequest to succeed. The immediate superior (parent) of an
object or alias entry to be added MUST exist. For example, if the
client attempted to add <CN=JS,DC=Example,DC=NET>, the
<DC=Example,DC=NET> entry did not exist, and the <DC=NET> entry did
exist, then the server would return the noSuchObject result code with
the matchedDN field containing <DC=NET>.
Server implementations SHOULD NOT restrict where entries can be
located in the Directory unless DIT structure rules are in place.
Some servers 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 add the
requested entry. 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 has been added to
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 name of the entry to be deleted.
The server SHALL NOT dereference aliases while resolving the name of
the target entry to be removed.
Only leaf entries (those with no subordinate entries) can be deleted
with this operation.
Upon receipt of a Delete Request, a server will attempt to perform
the entry removal requested and return the result in the Delete
Response defined as follows:
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DelResponse ::= [APPLICATION 11] LDAPResult
4.9. Modify DN Operation
The Modify DN Operation allows a client to change the Relative
Distinguished Name (RDN) of an entry in the Directory, and/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 {
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
Fields of the Modify DN Request are:
- entry: the name of the entry to be changed. This entry may or may
not have subordinate entries.
- newrdn: the new RDN of the entry. If the operation moves the entry
to a new superior without changing its RDN, the value of the old
RDN is supplied for this parameter.
Attribute values of the new RDN not matching any attribute value
of the entry are added to the entry and an appropriate error is
returned if this fails.
- deleteoldrdn: a boolean field 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 name of an existing object
entry which becomes the immediate superior (parent) of the
existing entry.
The server SHALL NOT dereference any aliases in locating the objects
named in entry or newSuperior.
Upon receipt of a ModifyDNRequest, a server will attempt to perform
the name change and return the result in the Modify DN Response,
defined as follows:
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
For example, if the entry named in the entry field was <cn=John
Smith,c=US>, the newrdn field was <cn=John Cougar Smith>, and the
newSuperior field 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 the
entryAlreadyExists result code.
The object named in newSuperior MUST exist. For example, if the
client attempted to add <CN=JS,DC=Example,DC=NET>, the
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<DC=Example,DC=NET> entry did not exist, and the <DC=NET> entry did
exist, then the server would return the noSuchObject result code with
the matchedDN field containing <DC=NET>.
If the deleteoldrdn field is TRUE, the attribute values forming the
old RDN but not the new RDN are deleted from the entry. If the
deleteoldrdn field is FALSE, the attribute values forming the old RDN
will be retained as non-distinguished attribute values of the entry.
The server MUST fail the operation and return an error in the result
code if the setting of the deleteoldrdn field 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
affectsMultipleDSAs result code 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 or
between naming contexts.
4.10. Compare Operation
The Compare Operation allows a client to compare an assertion value
with the values of a particular attribute in a particular entry in
the Directory. The Compare Request is defined as follows:
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
Fields of the Compare Request are:
- entry: the name of the entry to be compared. The server SHALL NOT
dereference any aliases in locating the entry to be compared.
- ava: holds the attribute value assertion to be compared.
Upon receipt of a Compare Request, a server will attempt to perform
the requested comparison and return the result in the Compare
Response, defined as follows:
CompareResponse ::= [APPLICATION 15] LDAPResult
The resultCode field is set to compareTrue, compareFalse, or an
appropriate error. compareTrue indicates that the assertion value in
the ava field matches a value of the attribute or subtype according
to the attribute's EQUALITY matching rule. compareFalse indicates
that the assertion value in the ava field and the values of the
attribute or subtype did not match. Other result codes indicate
either that the result of the comparison was Undefined (Section
4.5.1), or that some error occurred.
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Note that some directory systems may establish access controls which
permit the values of certain attributes (such as userPassword) to be
compared but not interrogated by other means.
4.11. Abandon Operation
The function of the Abandon Operation is to allow a client to request
that the server abandon an uncompleted operation. The Abandon Request
is defined as follows:
AbandonRequest ::= [APPLICATION 16] MessageID
The MessageID is that of an operation which was requested earlier in
this LDAP exchange. The abandon request itself has its own MessageID.
This is distinct from the MessageID of the earlier operation being
abandoned.
There is no response defined in the Abandon operation. Upon receipt
of an AbandonRequest, the server MAY abandon the operation identified
by the MessageID. Since the client cannot tell the difference between
a successfully abandoned operation and an uncompleted operation, the
application of the Abandon operation is limited to uses where the
client does not require an indication of its outcome.
Abandon, Bind, Unbind, and StartTLS operations cannot be abandoned.
In the event that a server receives an Abandon Request on a Search
Operation in the midst of transmitting responses 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.
The ability to abandon other (particularly update) operations is at
the discretion of the server.
Clients should 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, or are not able to be abandoned).
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
The extended operation allows additional operations to be defined for
services not already available in the protocol. For example, to add
operations to install transport layer security (see Section 4.14).
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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 extended operation consists of an extended request and an
extended response.
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
The requestName is a dotted-decimal representation of the unique
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 an
ExtendedResponse.
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
responseValue [11] OCTET STRING OPTIONAL }
The responseName is typically not required to be present as the
syntax and semantics of the response (including the format of the
responseValue) is implicitly known and associated with the request by
the messageID.
If the extended operation associated with the requestName is not
supported by the server, the server MUST NOT provide a responseName
nor a responseValue and MUST return a resultCode of protocolError.
The requestValue and responseValue fields contain any information
associated with the operation. The format of these fields is defined
by the specification of the extended operation. Implementations MUST
be prepared to handle arbitrary contents of these fields, including
zero bytes. Values that are defined in terms of ASN.1 and BER encoded
according to Section 5.2, also follow the extensibility rules in
Section 4.
Servers list the requestName of Extended Requests they recognize in
the 'supportedExtension' attribute in the root DSE (Section 5.1 of
[Models]).
Extended operations may be specified in other documents. The
specification of an extended operation consists of:
- the OBJECT IDENTIFIER assigned to the requestName,
- the OBJECT IDENTIFIER (if any) assigned to the responseName (note
that the same OBJECT IDENTIFIER my be used for both the
requestName and responseName),
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- the format of the contents of the requestValue and responseValue
(if any), and
- the semantics of the operation.
4.13. IntermediateResponse Message
While the Search operation provides a mechanism to return multiple
response messages for a single search request, other operations, by
nature, do not provide for multiple response messages.
The IntermediateResponse message provides a general mechanism for
defining single-request/multiple-response operations in LDAP. This
message is intended to be used in conjunction with the extended
operation to define new single-request/multiple-response operations
or in conjunction with a control when extending existing LDAP
operations in a way that requires them to return intermediate
response information.
It is intended that the definitions and descriptions of extended
operations and controls that make use of the IntermediateResponse
message will define the circumstances when an IntermediateResponse
message can be sent by a server and the associated meaning of an
IntermediateResponse message sent in a particular circumstance.
IntermediateResponse ::= [APPLICATION 25] SEQUENCE {
responseName [0] LDAPOID OPTIONAL,
responseValue [1] OCTET STRING OPTIONAL }
IntermediateResponse messages SHALL NOT be returned to the client
unless the client issues a request that specifically solicits their
return. This document defines two forms of solicitation: extended
operation and request control. IntermediateResponse messages are
specified in documents describing the manner in which they are
solicited (i.e. in the extended operation or request control
specification that uses them). These specifications include:
- the OBJECT IDENTIFIER (if any) assigned to the responseName,
- the format of the contents of the responseValue, and
- the semantics associated with the IntermediateResponse message.
Extensions that allow the return of multiple types of
IntermediateResponse messages SHALL identify those types using unique
responseName values (note that one of these may specify no value).
Sections 4.13.1 and 4.13.2 describe additional requirements on the
inclusion of responseName and responseValue in IntermediateResponse
messages.
4.13.1. Usage with LDAP ExtendedRequest and ExtendedResponse
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A single-request/multiple-response operation may be defined using a
single ExtendedRequest message to solicit zero or more
IntermediateResponse messages of one or more kinds followed by an
ExtendedResponse message.
4.13.2. Usage with LDAP Request Controls
A control's semantics may include the return of zero or more
IntermediateResponse messages prior to returning the final result
code for the operation. One or more kinds of IntermediateResponse
messages may be sent in response to a request control.
All IntermediateResponse messages associated with request controls
SHALL include a responseName. This requirement ensures that the
client can correctly identify the source of IntermediateResponse
messages when:
- two or more controls using IntermediateResponse messages are
included in a request for any LDAP operation or
- one or more controls using IntermediateResponse messages are
included in a request with an LDAP extended operation that uses
IntermediateResponse messages.
4.14. StartTLS Operation
The Start Transport Layer Security (StartTLS) operationĘs purpose is
to initiate installation of a TLS layer. The StartTLS operation is
defined using the extended operation mechanism described in Section
4.12.
4.14.1. StartTLS Request
A client requests TLS establishment by transmitting a StartTLS
request PDU to the server. The StartTLS request is defined in terms
of an ExtendedRequest. The requestName is "1.3.6.1.4.1.1466.20037",
and the requestValue field is always absent.
The client MUST NOT send any PDUs on this LDAP exchange following
this request until it receives a StartTLS extended response and, in
the case of a successful response, completes TLS negotiations.
Sequencing problems (particularly those detailed in Section 3.1.1 of
[AuthMeth] result in an operationsError being returned in the
resultCode.
If the server does not support TLS (whether by design or by current
configuration), it returns the protocolError resultCode as described
in Section 4.12.
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4.14.2. StartTLS Response
When a StartTLS request is made, servers supporting the operation
MUST return a StartTLS response PDU to the requestor. The
responseName, if present, is also "1.3.6.1.4.1.1466.20037". The
responseValue is absent.
If the server is willing and able to negotiate TLS, it returns a
success resultCode. Refer to Section 4 of [AuthMeth] for details.
If the server is otherwise unwilling or unable to perform this
operation, the server is to return an appropriate result code
indicating the nature of the problem. For example, if the TLS
subsystem is not presently available, the server may return indicate
so by returning the unavailable resultCode.
4.14.3. Removal of the TLS Layer
Two forms of TLS layer removal -- graceful and abrupt -- are
provided. These do not involve LDAP PDUs, but are preformed at the
underlying layers.
If the connection is closed, uncompleted operations are handled as
specified in Section 5.1.
4.14.3.1. Graceful Removal
Either the client or server MAY remove the TLS layer and leave the
LDAP exchange intact by sending and receiving a TLS closure alert.
The initiating protocol peer sends the TLS closure alert. If it
wishes to leave the LDAP exchange intact, it then MUST cease to send
further PDUs and MUST ignore any received LDAP PDUs until it receives
a TLS closure alert from the other peer.
Once the initiating protocol peer receives a TLS closure alert from
the other peer it MAY send and receive LDAP PDUs.
When a protocol peer receives the initial TLS closure alert, it may
choose to allow the LDAP exchange to remain intact. In this case, it
MUST immediately transmit a TLS closure alert. Following this, it MAY
send and receive LDAP PDUs.
Protocol peers MAY close the connection after sending or receiving a
TLS closure alert.
After the TLS layer has been removed, the server MUST NOT send
responses to any request message received before the TLS closure
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alert. Thus, clients wishing to receive responses to messages sent
while the TLS layer is intact MUST wait for those message responses
before sending the TLS closure alert.
4.14.3.2. Abrupt Removal
Either the client or server MAY abruptly remove the TLS layer by
closing the connection. In this circumstance, a server MAY send the
client a Notice of Disconnection before closing the connection.
5. Protocol Encoding, Connection, and Transfer
This protocol is designed to run over connection-oriented, reliable
transports, where the data stream is divided into octets (8-bit
units), with each octet and each bit being significant.
One underlying service, LDAP over TCP, is defined in Section
5.3. This service is generally applicable to applications providing
or consuming X.500-based directory services on the Internet. This
specification was generally written with the TCP mapping in mind.
Specifications detailing other mappings may encounter various
obstacles.
Implementations of LDAP over TCP MUST implement the mapping as
described in Section 5.3.
This table illustrates the relationship between the different layers
involved in an exchange between two protocol peers:
+---------------+
| LDAP exchange |
+---------------+ > LDAP PDUs
+---------------+ < data
| SASL layer |
+---------------+ > SASL-protected data
+---------------+ < data
| TLS layer |
Application +---------------+ > TLS-protected data
------------+---------------+ < data
Transport | connection |
+---------------+
5.2. Protocol Encoding
The protocol elements of LDAP SHALL be encoded for exchange using the
Basic Encoding Rules [BER] of [ASN.1] with the following
restrictions:
- Only the definite form of length encoding is used.
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- OCTET STRING values are encoded in the primitive form only.
- If the value of a BOOLEAN type is true, the encoding of the value
octet is set to hex "FF".
- If a value of a type is its default value, it is absent. Only some
BOOLEAN and INTEGER types have default values in this protocol
definition.
These restrictions are meant to ease the overhead of encoding and
decoding certain elements in BER.
These restrictions do not apply to ASN.1 types encapsulated inside of
OCTET STRING values, such as attribute values, unless otherwise
stated.
5.3. Transmission Control Protocol (TCP)
The encoded LDAPMessage PDUs are mapped directly onto the [TCP]
bytestream using the BER-based encoding described in Section 5.2. It
is recommended that server implementations running over the TCP
provide a protocol listener on the Internet Assigned Numbers
Authority (IANA)-assigned LDAP port, 389 [PortReg]. Servers may
instead provide a listener on a different port number. Clients MUST
support contacting servers on any valid TCP port.
6. Security Considerations
This version of the protocol provides facilities for simple
authentication using a cleartext password, as well as any [SASL]
mechanism. Installing SASL layers can provide integrity and other
data security services.
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.
Servers are encouraged to prevent directory modifications by clients
that have authenticated anonymously [AuthMeth].
Security considerations for authentication methods, SASL mechanisms,
and TLS are described in [AuthMeth].
It should be noted that SASL authentication exchanges do not provide
data confidentiality nor integrity protection for the version or name
fields of the bind request nor the resultCode, diagnosticMessage, or
referral fields of the bind response nor of any information contained
in controls attached to bind request or responses. Thus information
contained in these fields SHOULD NOT be relied on unless otherwise
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protected (such as by establishing protections at the transport
layer).
Server implementors should plan for the possibility of (protocol or
external) events which alter the information used to establish
security factors (e.g., credentials, authorization identities, access
controls) during the course of the LDAP exchange, and even during the
performance of a particular operation, and should take steps to avoid
insecure side effects of these changes. The ways in which these
issues are addressed are application and/or implementation specific.
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 in the cache.
Servers may return referrals or search result references which
redirect clients to peer servers. It is possible for a rogue
application to inject such referrals into the data stream in an
attempt to redirect a client to a rogue server. Clients are advised
to be aware of this, and possibly reject referrals when
confidentiality measures are not in place. Clients are advised to
reject referrals from the StartTLS operation.
The matchedDN and diagnosticMessage fields, as well as some
resultCode values (e.g., attributeOrValueExists and
entryAlreadyExists), could disclose the presence the specific data in
the directory which is subject to access and other administrative
controls. Server implementations should restrict access to protected
information equally under both normal and error conditions.
Protocol peers MUST be prepared to handle invalid and arbitrary
length protocol encodings. Invalid protocol encodings include: BER
encoding exceptions, format string and UTF-8 encoding exceptions,
overflow exceptions, integer value exceptions, and binary mode on/off
flag exceptions. The LDAPv3 PROTOS [PROTOS-LDAP] test suite provides
excellent examples of these exceptions and test cases used to
discover flaws.
7. Acknowledgements
This document is based on RFC 2251 by Mark Wahl, Tim Howes, and Steve
Kille. RFC 2251 was a product of the IETF ASID Working Group.
It is also based on RFC 2830 by Jeff Hodges, RL "Bob" Morgan, and
Mark Wahl. RFC 2830 was a product of the IETF LDAPEXT Working Group.
It is also based on RFC 3771 by Roger Harrison, and Kurt Zeilenga.
RFC 3771 was an individual submission to the IETF.
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This document is a product of the IETF LDAPBIS Working Group.
Significant contributors of technical review and content include Kurt
Zeilenga, Steven Legg, and Hallvard Furuseth.
8. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[ASN.1] ITU-T Recommendation X.680 (07/2002) | ISO/IEC 8824-1:2002
"Information Technology - Abstract Syntax Notation One
(ASN.1): Specification of basic notation"
[AuthMeth] Harrison, R., "LDAP: Authentication Methods and Connection
Level Security Mechanisms", draft-ietf-ldapbis-authmeth-
xx.txt, (a work in progress).
[BER] ITU-T Rec. X.690 (07/2002) | ISO/IEC 8825-1:2002,
"Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", 2002.
[IP] Postel, J., "Internet Protocol", STD5 and RFC 791,
September 1981
[ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC 10646-1
: 1993.
[Keyword] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[LDAPDN] Zeilenga, K., "LDAP: String Representation of
Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, (a
work in progress).
[LDAPIANA] Zeilenga, K., "IANA Considerations for LDAP", draft-ietf-
ldapbis-bcp64-xx.txt, (a work in progress).
[LDAPURL] Smith, M., "LDAP: Uniform Resource Locator", draft-ietf-
ldapbis-url-xx.txt, (a work in progress).
[Models] Zeilenga, K., "LDAP: Directory Information Models", draft-
ietf-ldapbis-models-xx.txt (a work in progress).
[Roadmap] Zeilenga, K., "LDAP: Technical Specification Road Map",
draft-ietf-ldapbis-roadmap-xx.txt (a work in progress).
[SASL] Melnikov, A., "Simple Authentication and Security Layer",
draft-ietf-sasl-rfc2222bis-xx.txt (a work in progress).
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[SASLPrep] Zeilenga, K., "Stringprep profile for user names and
passwords", draft-ietf-sasl-saslprep-xx.txt, (a work in
progress).
[StringPrep] Hoffman P. and M. Blanchet, "Preparation of
Internationalized Strings ('stringprep')", draft-hoffman-
rfc3454bis-xx.txt, a work in progress.
[Syntaxes] Legg, S., and K. Dally, "LDAP: Syntaxes and Matching
Rules", draft-ietf-ldapbis-syntaxes-xx.txt, (a work in
progress).
[TCP] Postel, J., "Transmission Control Protocol", STD7 and RFC
793, September 1981
[TLS] Dierks, T. and C. Allen. "The TLS Protocol Version 1.1",
draft-ietf-tls-rfc2246-bis-xx.txt, a work in progress.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version
3.2.0" is defined by "The Unicode Standard, Version 3.0"
(Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5),
as amended by the "Unicode Standard Annex #27: Unicode
3.1" (http://www.unicode.org/reports/tr27/) and by the
"Unicode Standard Annex #28: Unicode 3.2"
(http://www.unicode.org/reports/tr28/).
[URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD63 and RFC3629, November 2003.
[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.
[X.511] ITU-T Rec. X.511, "The Directory: Abstract Service
Definition", 1993.
9. Informative References
[Glossary] The Unicode Consortium, "Unicode Glossary",
<http://www.unicode.org/glossary/>.
[CharModel] Whistler, K. and M. Davis, "Unicode Technical Report
#17, Character Encoding Model", UTR17,
<http://www.unicode.org/unicode/reports/tr17/>, August
2000.
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[PROTOS-LDAP] University of Oulu, "PROTOS Test-Suite: c06-ldapv3"
<http://www.ee.oulu.fi/research/ouspg/protos/testing/c06/l
dapv3/>
[PortReg] IANA, "Port Numbers",
http://www.iana.org/assignments/port-numbers
10. IANA Considerations
It is requested that the Internet Assigned Numbers Authority (IANA)
update the LDAP result code registry to indicate that this document
provides the definitive technical specification for result codes 0-
36, 48-54, 64-70, 80-90.
It is requested that the IANA update the LDAP Protocol Mechanism
registry to indicate that this document and [AuthMeth] provides the
definitive technical specification for the StartTLS
(1.3.6.1.4.1.1466.20037) extended operation.
It is requested that the IANA update the occurrence of "RFC XXXX" in
Appendix B with this RFC number at publication.
11. Editor's Address
Jim Sermersheim
Novell, Inc.
1800 South Novell Place
Provo, Utah 84606, USA
jimse@novell.com
+1 801 861-3088
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Appendix A - LDAP Result Codes
This normative appendix details additional considerations regarding
LDAP result codes and provides a brief, general description of each
LDAP result code enumerated in Section 4.1.9.
Additional result codes MAY be defined for use with extensions
[LDAPIANA]. Client implementations SHALL treat any result code which
they do not recognize as an unknown error condition.
A.1 Non-Error Result Codes
These result codes (called "non-error" result codes) do not indicate
an error condition:
success (0),
compareFalse (5),
compareTrue (6),
referral (10), and
saslBindInProgress (14).
The success, compareTrue, and compareFalse result codes indicate
successful completion (and, hence, are referred to as "successful"
result codes).
The referral and saslBindInProgress result codes indicate the client
is required to take additional action to complete the operation.
A.2 Result Codes
Existing LDAP result codes are described as follows:
success (0)
Indicates the successful completion of an operation. Note:
this code is not used with the compare operation. See
compareFalse (5) and compareTrue (6).
operationsError (1)
Indicates that the operation is not properly sequenced with
relation to other operations (of same or different type).
For example, this code is returned if the client attempts to
StartTLS [TLS] while there are other uncompleted operations
or if a TLS layer was already installed.
protocolError (2)
Indicates the server received data which is not well-formed.
For bind operation only, this code is also used to indicate
that the server does not support the requested protocol
version.
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For extended operations only, this code indicates that the
server does not support (by design or configuration) the
extended operation associated with the requestName.
For request operations specifying multiple controls, this may
be used to indicate that the server cannot ignore the order
of the controls as specified, or that the combination of the
specified controls is invalid or unspecified.
timeLimitExceeded (3)
Indicates that the time limit specified by the client was
exceeded before the operation could be completed.
sizeLimitExceeded (4)
Indicates that the size limit specified by the client was
exceeded before the operation could be completed.
compareFalse (5)
Indicates that the compare operation has successfully
completed and the assertion has evaluated to FALSE or
Undefined.
compareTrue (6)
Indicates that the compare operation has successfully
completed and the assertion has evaluated to TRUE.
authMethodNotSupported (7)
Indicates that the authentication method or mechanism is not
supported.
strongAuthRequired (8)
Indicates that the server has detected that an established
security association between the client and server has
unexpectedly failed or been compromised, or that the server
now requires the client to authenticate using a strong(er)
mechanism.
referral (10)
Indicates that a referral needs to be chased to complete the
operation (see Section 4.1.10).
adminLimitExceeded (11)
Indicates that an administrative limit has been exceeded.
unavailableCriticalExtension (12)
Indicates a critical control is unrecognized (see Section
4.1.11).
confidentialityRequired (13)
Indicates that data confidentiality protections are required.
saslBindInProgress (14)
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Indicates the server requires the client to send a new bind
request, with the same SASL mechanism, to continue the
authentication process (see Section 4.2).
noSuchAttribute (16)
Indicates that the named entry does not contain the specified
attribute or attribute value.
undefinedAttributeType (17)
Indicates that a request field contains an unrecognized
attribute description.
inappropriateMatching (18)
Indicates that an attempt was made (e.g. in an assertion) to
use a matching rule not defined for the attribute type
concerned.
constraintViolation (19)
Indicates that the client supplied an attribute value which
does not conform to the constraints placed upon it by the
data model.
For example, this code is returned when multiple values are
supplied to an attribute which has a SINGLE-VALUE constraint.
attributeOrValueExists (20)
Indicates that the client supplied an attribute or value to
be added to an entry, but the attribute or value already
exists.
invalidAttributeSyntax (21)
Indicates that a purported attribute value does not conform
to the syntax of the attribute.
noSuchObject (32)
Indicates that the object does not exist in the DIT.
aliasProblem (33)
Indicates that an alias problem has occurred. For example,
the code may used to indicate an alias has been dereferenced
which names no object.
invalidDNSyntax (34)
Indicates that an LDAPDN or RelativeLDAPDN field (e.g. search
base, target entry, ModifyDN newrdn, etc.) of a request does
not conform to the required syntax or contains attribute
values which do not conform to the syntax of the attribute's
type.
aliasDereferencingProblem (36)
Indicates that a problem occurred while dereferencing an
alias. Typically an alias was encountered in a situation
where it was not allowed or where access was denied.
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inappropriateAuthentication (48)
Indicates the server requires the client which had attempted
to bind anonymously or without supplying credentials to
provide some form of credentials.
invalidCredentials (49)
Indicates that the provided credentials (e.g. the user's name
and password) are invalid.
insufficientAccessRights (50)
Indicates that the client does not have sufficient access
rights to perform the operation.
busy (51)
Indicates that the server is too busy to service the
operation.
unavailable (52)
Indicates that the server is shutting down or a subsystem
necessary to complete the operation is offline.
unwillingToPerform (53)
Indicates that the server is unwilling to perform the
operation.
loopDetect (54)
Indicates that the server has detected an internal loop (e.g.
while dereferencing aliases or chaining an operation).
namingViolation (64)
Indicates that the entry's name violates naming restrictions.
objectClassViolation (65)
Indicates that the entry violates object class restrictions.
notAllowedOnNonLeaf (66)
Indicates that the operation is inappropriately acting upon a
non-leaf entry.
notAllowedOnRDN (67)
Indicates that the operation is inappropriately attempting to
remove a value which forms the entry's relative distinguished
name.
entryAlreadyExists (68)
Indicates that the request cannot be fulfilled (added, moved,
or renamed) as the target entry already exists.
objectClassModsProhibited (69)
Indicates that an attempt to modify the object class(es) of
an entry's 'objectClass' attribute is prohibited.
For example, this code is returned when a client attempts to
modify the structural object class of an entry.
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affectsMultipleDSAs (71)
Indicates that the operation cannot be performed as it would
affect multiple servers (DSAs).
other (80)
Indicates the server has encountered an internal error.
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Appendix B - Complete ASN.1 Definition
This appendix is normative.
Lightweight-Directory-Access-Protocol-V3
-- Copyright (C) The Internet Society (2004). This version of
-- this ASN.1 module is part of RFC XXXX; see the RFC itself
-- for full legal notices.
DEFINITIONS
IMPLICIT TAGS
EXTENSIBILITY IMPLIED ::=
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,
...,
intermediateResponse IntermediateResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
LDAPString ::= OCTET STRING -- UTF-8 encoded,
-- [ISO10646] characters
LDAPOID ::= OCTET STRING -- Constrained to <numericoid> [Models]
LDAPDN ::= LDAPString -- Constrained to <distinguishedName>
-- [LDAPDN]
RelativeLDAPDN ::= LDAPString -- Constrained to <name-component>
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-- [LDAPDN]
AttributeDescription ::= LDAPString
-- Constrained to <attributedescription>
-- [Models]
AttributeValue ::= OCTET STRING
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
PartialAttribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF value AttributeValue }
Attribute ::= PartialAttribute(WITH COMPONENTS {
...,
vals (SIZE(1..MAX))})
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),
adminLimitExceeded (11),
unavailableCriticalExtension (12),
confidentialityRequired (13),
saslBindInProgress (14),
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 --
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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),
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71),
-- 72-79 unused --
other (80),
... },
matchedDN LDAPDN,
diagnosticMessage LDAPString,
referral [3] Referral OPTIONAL }
Referral ::= SEQUENCE SIZE (1..MAX) OF uri URI
URI ::= LDAPString -- limited to characters permitted in
-- URIs
Controls ::= SEQUENCE OF control 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 }
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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),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeSelection }
AttributeSelection ::= SEQUENCE OF selector LDAPString
-- The LDAPString is constrained to
-- <attributeSelection> in Section 4.5.1
Filter ::= CHOICE {
and [0] SET OF filter Filter,
or [1] SET OF filter 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,
-- initial and final can occur at most once
substrings SEQUENCE SIZE (1..MAX) OF substring 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 }
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PartialAttributeList ::= SEQUENCE OF
partialAttribute PartialAttribute
SearchResultReference ::= [APPLICATION 19] SEQUENCE
SIZE (1..MAX) OF uri URI
SearchResultDone ::= [APPLICATION 5] LDAPResult
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
changes SEQUENCE OF change SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification PartialAttribute } }
ModifyResponse ::= [APPLICATION 7] LDAPResult
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF attribute Attribute
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,
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responseValue [11] OCTET STRING OPTIONAL }
IntermediateResponse ::= [APPLICATION 25] SEQUENCE {
responseName [0] LDAPOID OPTIONAL,
responseValue [1] OCTET STRING OPTIONAL }
END
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Appendix C - Changes
This appendix is non-normative.
This appendix summarizes substantive changes made to RFC 2251 and RFC
2830.
C.1 Changes made to RFC 2251:
This section summarizes the substantive changes made to Sections 1,
2, 3.1, and 4 through the remainder of RFC 2251. Readers should
consult [Models] and [AuthMeth] for summaries of changes to other
sections.
C.1.1 Section 1
- Removed IESG note. Post publication of RFC 2251, mandatory LDAP
authentication mechanisms have been standardized which are
sufficient to remove this note. See [AuthMeth] for authentication
mechanisms.
C.1.2 Section 3.1 and others
- Removed notes giving history between LDAP v1, v2 and v3. Instead,
added sufficient language so that this document can stand on its
own.
C.1.3 Section 4
- Clarified where the extensibility features of ASN.1 apply to the
protocol. This change also affected various ASN.1 types.
- Removed the requirement that servers which implement version 3 or
later MUST provide the 'supportedLDAPVersion' attribute. This
statement provided no interoperability advantages.
C.1.4 Section 4.1.1
- There was a mandatory requirement for the server to return a
Notice of Disconnection and drop the connection when a PDU is
malformed in a certain way. This has been clarified such that the
server SHOULD return the Notice of Disconnection, and MUST drop
the connection.
C.1.5 Section 4.1.1.1
- Clarified that the messageID of requests MUST be non-zero.
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- Clarified when it is and isn't appropriate to return an already
used message id. RFC 2251 accidentally imposed synchronous server
behavior in its wording of this.
C.1.6 Section 4.1.2
- Stated that LDAPOID is constrained to <numericoid> from [Models].
C.1.7 Section 4.1.5.1 and others
- Removed the Binary Option from the specification. There are
numerous interoperability problems associated with this method of
alternate attribute type encoding. Work to specify a suitable
replacement is ongoing.
C.1.8 Section 4.1.8
- Combined the definitions of PartialAttribute and Attribute here,
and defined Attribute in terms of PartialAttribute.
C.1.9 Section 4.1.10
- Renamed "errorMessage" to "diagnosticMessage" as it is allowed to
be sent for non-error results.
- Moved some language into Appendix A, and refer the reader there.
- Allowed matchedDN to be present for other result codes than those
listed in RFC 2251.
C.1.10 Section 4.1.11
- Defined referrals in terms of URIs rather than URLs.
- Removed the requirement that all referral URIs MUST be equally
capable of progressing the operation. The statement was ambiguous
and provided no instructions on how to carry it out.
- Added the requirement that clients MUST NOT loop between servers.
- Clarified the instructions for using LDAPURLs in referrals, and in
doing so added a recommendation that the scope part be present.
C.1.11 Section 4.1.12
- Specified how control values defined in terms of ASN.1 are to be
encoded.
- Noted that the criticality field is only applied to request
messages (except unbindRequest), and must be ignored when present
on response messages and unbindRequest.
- Added language regarding combinations of controls and the ordering
of controls on a message.
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- Specified that when the semantics of the combination of controls
is undefined or unknown, it results in a protocolError.
- Changed "The server MUST be prepared" to "Implementations MUST be
prepared" in the eighth paragraph to reflect that both client and
server implementations must be able to handle this (as both parse
controls).
C.1.12 Section 4.2
- Mandated that servers return protocolError when the version is not
supported.
- Clarified behavior when the simple authentication is used, the
name is empty and the password is non-empty.
- Required servers to not dereference aliases for bind. This was
added for consistency with other operations and to help ensure
data consistency.
- Required that textual passwords be transferred as UTF-8 encoded
Unicode, and added recommendations on string preparation. This was
to help ensure interoperability of passwords being sent from
different clients.
C.1.13 Section 4.2.1
- This section was largely reorganized for readability and language
was added to clarify the authentication state of failed and
abandoned bind operations.
- Removed: "If a SASL transfer encryption or integrity mechanism has
been negotiated, that mechanism does not support the changing of
credentials from one identity to another, then the client MUST
instead establish a new connection."
Each SASL negotiation is, generally, independent of other SASL
negotiations. If there were dependencies between multiple
negotiations of a particular mechanism, the mechanism technical
specification should detail how applications are to deal with
them. LDAP should not require any special handling. And if an LDAP
client had used such a mechanism, it would have the option of
using another mechanism.
- Dropped MUST imperative in paragraph 3 to align with [Keywords].
- Mandated that clients not send non-bind operations while a bind is
in progress, and suggested that servers not process them if they
are received. This is needed to ensure proper sequencing of the
bind in relationship to other operations.
C.1.14 Section 4.2.3
- Moved most error-related text to Appendix A, and added text
regarding certain errors used in conjunction with the bind
operation.
- Prohibited the server from specifying serverSaslCreds when not
appropriate.
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C.1.15 Section 4.3
- Required both peers to cease transmission and close the LDAP
exchange for the unbind operation.
C.1.16 Section 4.4
- Added instructions for future specifications of Unsolicited
Notifications.
C.1.17 Section 4.5.1
- SearchRequest attributes is now defined as an AttributeSelection
type rather than AttributeDescriptionList, and an ABNF is
provided.
- SearchRequest attributes may contain duplicate attribute
descriptions. This was previously prohibited. Now servers are
instructed to ignore subsequent names when they are duplicated.
This was relaxed in order to allow different short names and also
OIDs to be requested for an attribute.
- The Filter choice SubstringFilter substrings type is now defined
with a lower bound of 1.
- The SubstringFilter substrings 'initial, 'any', and 'final' types
are now AssertionValue rather than LDAPString. Also, added
imperatives stating that 'initial' (if present) must be listed
first, and 'final' (if present) must be listed last.
- Clarified the semantics of the derefAliases choices.
- Added instructions for equalityMatch, substrings, greaterOrEqual,
lessOrEqual, and approxMatch.
C.1.18 Section 4.5.2
- Recommended that servers not use attribute short names when it
knows they are ambiguous or may cause interoperability problems.
- Removed all mention of ExtendedResponse due to lack of
implementation.
C.1.19 Section 4.5.3
- Made changes similar to those made to Section 4.1.11.
C.1.20 Section 4.5.3.1
- Fixed examples to adhere to changes made to Section 4.5.3.
C.1.21 Section 4.6
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- Removed restriction that required an EQUALITY matching rule in
order to perform value delete modifications. It is sufficiently
documented that in absence of an equality matching rule, octet
equality is used.
- Replaced AttributeTypeAndValues with Attribute as they are
equivalent.
- Clarified what type of modification changes might temporarily
violate schema.
C.1.22 Section 4.7
- Aligned Add operation with X.511 in that the attributes of the RDN
are used in conjunction with the listed attributes to create the
entry. Previously, Add required that the distinguished values be
present in the listed attributes.
C.1.23 Section 4.9
- Required servers to not dereference aliases for modify DN. This
was added for consistency with other operations and to help ensure
data consistency.
- Allow modify DN to fail when moving between naming contexts.
- Specified what happens when the attributes of the newrdn are no
present on the entry.
C.1.24 Section 4.10
- Clarified that compareFalse means that the compare took place and
the result is false. There was confusion which lead people to
believe that an Undefined match resulted in compareFalse.
- Required servers to not dereference aliases for compare. This was
added for consistency with other operations and to help ensure
data consistency.
C.1.25 Section 4.11
- Explained that since abandon returns no response, clients should
not use it if they need to know the outcome.
- Specified that Abandon and Unbind cannot be abandoned.
C.1.26 Section 4.12
- Specified how values of extended operations defined in terms of
ASN.1 are to be encoded.
- Added instructions on what extended operation specifications
consist of.
- Added a recommendation that servers advertise supported extended
operations.
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C.1.27 Section 5.2
- Moved referral-specific instructions into referral-related
sections.
C.1.28 Section 7
- Reworded notes regarding SASL not protecting certain aspects of
the LDAP bind PDU.
- Noted that Servers are encouraged to prevent directory
modifications by clients that have authenticated anonymously
[AuthMeth].
- Added a note regarding the scenario where an identity is changed
(deleted, privileges or credentials modified, etc.).
- Warned against following referrals that may have been injected in
the data stream.
- Noted that servers should protect information equally, whether in
an error condition or not, and mentioned specifically; matchedDN,
diagnosticMessage, and resultCodes.
- Added a note regarding malformed and long encodings.
C.1.29 Appendix A
- Added "EXTENSIBILITY IMPLIED" to ASN.1 definition.
- Removed AttributeType. It is not used.
C.2 Changes made to RFC 2830:
This section summarizes the substantive changes made to Sections of
RFC 2830. Readers should consult [AuthMeth] for summaries of changes
to other sections.
C.2.1 Section 2.3
- Removed wording indicating that referrals can be returned from
StartTLS
- Removed requirement that only a narrow set of result codes can be
returned. Some result codes are required in certain scenarios, but
any other may be returned if appropriate.
C.2.1 Section 4.13.3.1
- Reworded most of this section and added the requirement that after
the TLS connection has been closed, the server MUST NOT send
responses to any request message received before the TLS closure.
C.3 Changes made to RFC 3771:
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- In general, all technical language was transferred in whole.
Supporting and background language seen as redundant due to its
presence in this document was omitted.
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this standard. Please address the information to the IETF at ietf-
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This document and the information contained herein are provided on an
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INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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Copyright Statement
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except as set forth therein, the authors retain all their rights.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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