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Internet-Draft Editor: J. Sermersheim
Intended Category: Standard Track Novell, Inc
Document: draft-ietf-ldapbis-protocol-19.txt Dec 2003
Obsoletes: RFC 2251, 2830
LDAP: The Protocol
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited. Technical discussion of this
document will take place on the IETF LDAP Revision Working Group
(LDAPbis) mailing list <ietf-ldapbis@openldap.org>. Please send
editorial comments directly to the editor <jimse@novell.com>.
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).
Table of Contents
1. Introduction....................................................2
1.1. Relationship to Obsolete Specifications.......................3
2. Conventions.....................................................3
3. Protocol Model..................................................3
4. Elements of Protocol............................................4
4.1. Common Elements...............................................4
4.1.1. Message Envelope............................................4
4.1.2. String Types................................................6
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4.1.3. Distinguished Name and Relative Distinguished Name..........6
4.1.4. Attribute Descriptions......................................7
4.1.5. Attribute Value.............................................7
4.1.6. Attribute Value Assertion...................................7
4.1.7. Attribute and PartialAttribute..............................8
4.1.8. Matching Rule Identifier....................................8
4.1.9. Result Message..............................................8
4.1.10. Referral..................................................10
4.1.11. Controls..................................................11
4.2. Bind Operation...............................................12
4.3. Unbind Operation.............................................15
4.4. Unsolicited Notification.....................................16
4.5. Search Operation.............................................17
4.6. Modify Operation.............................................25
4.7. Add Operation................................................26
4.8. Delete Operation.............................................27
4.9. Modify DN Operation..........................................28
4.10. Compare Operation...........................................29
4.11. Abandon Operation...........................................30
4.12. Extended Operation..........................................30
4.13. StartTLS Operation..........................................31
5. Protocol Element Encodings and Transfer........................33
5.1. Protocol Encoding............................................34
5.2. Transfer Protocols...........................................34
6. Security Considerations........................................34
7. Acknowledgements...............................................36
8. Normative References...........................................36
9. Informative References.........................................37
10. IANA Considerations...........................................37
11. Editor's Address..............................................38
Appendix A - LDAP Result Codes....................................39
A.1 Non-Error Result Codes........................................39
A.2 Result Codes..................................................39
Appendix B - Complete ASN.1 Definition............................43
Appendix C - Changes..............................................48
C.1 Changes made to made to RFC 2251:.............................48
C.2 Changes made to made to RFC 2830:.............................53
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.
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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 also 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.
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].
The terms "connection" and "LDAP connection" both refer to the
underlying transport protocol connection between two protocol peers.
The term "TLS connection" refers to a TLS-protected LDAP connection.
The terms "association" and "LDAP association" both refer to the
association of the LDAP connection and its current authentication and
authorization state.
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 the
operation(s), the server returns a response containing an appropriate
result code to the requesting client.
Although servers are required to return responses whenever such
responses are defined in the protocol, there is no requirement for
synchronous behavior on the part of either clients or servers.
Requests and responses for multiple operations may be exchanged
between a client and server in any order, provided the client
eventually receives a response for every request that requires one.
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The core protocol operations defined in this document can be mapped
to a subset of the X.500 (1993) Directory Abstract Service. However
there is not a one-to-one mapping between LDAP protocol 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.
4. Elements of Protocol
The LDAP protocol is described using Abstract Syntax Notation One
([ASN.1]), and is transferred using a subset of ASN.1 Basic Encoding
Rules ([BER]). Section 5.1 specifies how the protocol elements are
encoded and transferred.
In order to support future Standards Track extensions to this
protocol, extensibility is implied where it is allowed (per ASN.1).
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 LDAP 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,
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searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse,
... },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
The function of the LDAPMessage is to provide an envelope containing
common fields required in all protocol exchanges. At this time the
only common fields are the message ID and the controls.
If the server receives a PDU from the client in which the LDAPMessage
SEQUENCE tag cannot be recognized, the messageID cannot be parsed,
the tag of the protocolOp is not recognized as a request, or the
encoding structures or lengths of data fields are found to be
incorrect, then the server 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.
The ASN.1 type Controls is defined in Section 4.1.11.
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 values of any other requests outstanding in the LDAP association
of which this message is a part. The zero value is reserved for the
unsolicited notification message.
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Typical clients increment a counter for each request.
A client MUST NOT send a request with the same message ID as an
earlier request on the same LDAP association unless it can be
determined that the server is no longer servicing the earlier
request. Otherwise the behavior is undefined. For operations that do
not return responses (unbind, abandon, and abandoned operations), the
client SHOULD assume the operation is in progress until a subsequent
bind request completes.
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 1.3 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]
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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
-- 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 attributes (e.g.
photographs).
Attributes may be defined which have arbitrary and non-printable
syntax. Implementations MUST NOT display nor attempt to decode a
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 NOT send attribute values in a request that are not
valid according to the syntax defined for the attributes.
4.1.6. Attribute Value Assertion
The AttributeValueAssertion type definition is similar to the one in
the X.500 Directory standards. It contains an attribute description
and a matching rule assertion value suitable for that type.
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
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
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the value syntax. See objectIdentiferFirstComponentMatch in
[Syntaxes] for an example.
4.1.7. Attribute and PartialAttribute
Attributes and partial attributes consist of an attribute description
and values of that attribute description. 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))})
Each attribute value is distinct in the set (no duplicates). 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 4.1.3 of [Models]. A matching rule is
identified in the LDAP protocol by the printable representation of
either its <numericoid>, or one of its short name descriptors
[Models], e.g. "caseIgnoreIA5Match" or "1.3.6.1.4.1.453.33.33".
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),
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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 --
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),
... },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
diagnosticMessage LDAPString,
referral [3] Referral OPTIONAL }
The resultCode enumeration is extensible as defined in Section 3.5 of
[LDAPIANA]. The meanings of the 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.
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For certain result codes (typically, but not restricted to
noSuchObject, aliasProblem, invalidDNSyntax and
aliasDereferencingProblem), the matchedDN field is set to the name of
the lowest entry (object or alias) in the Directory that was matched.
If no aliases were dereferenced while attempting to locate the entry,
this will be a truncated form of the name provided, or if aliases
were dereferenced, of the resulting name, as defined in Section 12.5
of [X.511]. Otherwise the matchedDN field is empty.
4.1.10. Referral
The referral result code indicates that the contacted server does not
hold the target entry of the request. The referral field is present
in an LDAPResult if the 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 the search scope spans multiple naming contexts, and several
different 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 services. If multiple URIs are
present, the client assumes that any URI may be used to progress the
operation.
Clients 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 clients use a counter that is incremented each time referral
handling occurs for an operation, and these kinds of clients 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].
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. Note that UTF-8
characters appearing in a DN or search filter may not be legal
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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 ignore URIs that they
do not support.
4.1.11. Controls
A control is a way to specify extension information for an LDAP
message. A control only alters the semantics of the message it is
attached to.
Controls ::= SEQUENCE OF control Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
The controlType field is the UTF-8 encoded dotted-decimal
representation of an OBJECT IDENTIFIER which uniquely identifies the
control, or the request control and its paired response control. This
prevents conflicts between control names.
The criticality field is either TRUE or FALSE and only applies to
request messages that have a corresponding response message. For all
other messages (such as abandonRequest, unbindRequest and all
response messages), the criticality field SHOULD be FALSE.
If the server recognizes the control type and it is appropriate for
the operation, the server will make use of the control when
performing the operation.
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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, MUST set the resultCode to unavailableCriticalExtension.
If the control is unrecognized or inappropriate but the criticality
field is FALSE, the server MUST ignore the control.
The controlValue contains any information associated with the
control. 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. controlValues that are defined in terms of ASN.1 and BER
encoded according to Section 5.1, also follow the extensibility rules
in Section 4.
Servers list the controlType of all request controls they recognize
in the supportedControl attribute [Models] in the root DSE.
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. In the absence of combination
semantics, the behavior of the operation is undefined.
Additionally, unless order-dependent semantics are given in a
specification, the order of a combination of controls in the SEQUENCE
is ignored.
This document does not specify any controls. Controls may be
specified in other documents. The specification of a control consists
of:
- the OBJECT IDENTIFIER assigned to the control,
- whether the control is always non critical, always critical, or
optionally critical,
- whether there is information associated with the control, 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.
Authentication and security-related semantics of this operation are
given in [AuthMeth].
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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 }
Parameters of the Bind Request are:
- version: A version number indicating the version of the protocol
to be used in this protocol association. This document describes
version 3 of the LDAP protocol. Note that there is no version
negotiation. The client sets this parameter to the version it
desires. If the server does not support the specified version, it
MUST respond with protocolError in the resultCode field of the
BindResponse.
- name: The name of the Directory object that the client wishes to
bind as. This field may take on a null value (a zero length
string) for the purposes of anonymous binds ([AuthMeth] Section 7)
or when using Simple Authentication and Security Layer [SASL]
authentication ([AuthMeth] Section 4.3). Server behavior is
undefined when the name is a null value, simple authentication is
used, and a password is specified. The server SHALL NOT perform
alias dereferencing in determining the object to bind as.
- authentication: information used to authenticate the name, if any,
provided in the Bind Request. This type is extensible as defined
in Section 3.6 of [LDAPIANA]. Servers that do not support a choice
supplied by a client will return authMethodNotSupported in the
resultCode field of the BindResponse.
The simple form of an AuthenticationChoice specifies a simple
password to be used for authentication.
Textual passwords (consisting of a character sequence with a known
character set and encoding) SHALL be transferred as [UTF-8]
encoded [Unicode]. The determination of whether a password is
textual is a local client matter.
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.
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Authorization is the use of this authentication information when
performing operations. Authorization MAY be affected by factors
outside of the LDAP Bind Request, such as those provided by lower
layer security services.
4.2.1. Processing of the Bind Request
Before processing a BindResponse, all outstanding operations MUST
either complete or be abandoned. The server may either wait for the
outstanding 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.
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
connection, 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.
Clients may send multiple Bind Requests on a connection 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. This is indicated by
the server sending a BindResponse with the resultCode set to
saslBindInProgress. This indicates that the server requires the
client to send a new bind request, with the same sasl mechanism, to
continue the authentication process. If at any stage the client
wishes to abort the bind process it MAY unbind and then drop the
underlying connection. Clients MUST NOT invoke operations between two
Bind Requests made as part of a multi-stage bind.
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.
A failed Bind Operation has the effect of leaving the connection in
an anonymous state. An abandoned Bind operation also has the effect
of leaving the connection in an anonymous state when (and if) the
server processes the abandonment of the bind. Client implementers
should note that the client has no way of being sure when (or if) an
abandon request succeeds, therefore, to arrive at a known
authentication state after abandoning a bind operation, clients may
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either unbind (which results in the underlying connection being
closed) or by issuing a bind request and then examining the
BindResponse returned by the server.
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 response where the resultCode
field is protocolError, it MUST close the connection as the server
will be unwilling to accept further operations. (This is for
compatibility with earlier versions of LDAP, in which the bind was
always the first operation, and there was no negotiation.)
The serverSaslCreds are used as part of a SASL-defined bind mechanism
to allow the client to authenticate the server to which it is
communicating, or to perform "challenge-response" authentication. If
the client bound with the 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.
4.3. Unbind Operation
The function of the Unbind Operation is to terminate an LDAP
association and 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
association terminated, MUST cease transmission of messages to the
other peer, and MUST close the connection. Any outstanding operations
on the server are, when possible, abandoned, and when not possible,
completed without transmission of the response.
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4.4. Unsolicited Notification
An unsolicited notification is an LDAPMessage sent from the server to
the client which is not in response to any LDAPMessage received by
the server. It is used to signal an extraordinary condition in the
server or in the connection between the client and the server. The
notification is of an advisory nature, and the server will not expect
any response to be returned from the client.
The unsolicited notification is structured as an LDAPMessage in which
the messageID is zero and protocolOp is of the extendedResp form. 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. Note that this notification is NOT a response to an unbind
requested by the client: the server MUST follow the procedures of
Section 4.3. This notification is intended to assist clients in
distinguishing between an error condition and a transient network
failure. As with a connection close due to network failure, the
client MUST NOT assume that any outstanding requests which modified
the Directory have succeeded or failed.
The responseName is 1.3.6.1.4.1.1466.20036, the response field is
absent, and the resultCode is used to indicate the reason for the
disconnection.
The following result codes have these meanings when used in this
notification:
- protocolError: The server has received data from the client in
which the LDAPMessage structure could not be parsed.
- strongAuthRequired: The server has detected that an established
security association between the client and server has
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unexpectedly failed or been compromised, or that the server now
requires the client to authenticate using a strong(er) mechanism.
- unavailable: This server will stop accepting new connections and
operations on all existing connections, and be unavailable for an
extended period of time. The client may make use of an alternative
server.
Upon transmission of the UnbindRequest, each protocol peer is to
consider the LDAP association terminated, MUST cease transmission of
messages to the other peer, 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 selection LDAPString
-- constrained to <attributeSelection> below
Filter ::= CHOICE {
and [0] SET SIZE (1..MAX) OF filter Filter,
or [1] SET SIZE (1..MAX) OF filter Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
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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 }
Parameters 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.
oneLevel: 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 objects (as defined in
[X.501]) are to be handled in searching. The semantics of the
possible values of this field are:
neverDerefAliases: Do not dereference aliases in searching
or in locating the base object of the search.
derefInSearching: While searching, dereference any alias
object 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 detect looping in this process to prevent denial of
service attacks and duplicate entries.
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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.
- 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 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 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.
The present match evaluates to TRUE where there is an attribute or
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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.
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 MUST
conform 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. The entire SubstringFilter
is converted into an assertion value of the substrings matching
rule prior to applying the rule.
The matching rule for greaterOrEqual and lessOrEqual filter items
is defined by the ORDERING matching rule for the attribute type.
The approxMatch 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, this filter item should be treated as an equalityMatch.
An extensibleMatch 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
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
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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. If
an attribute description in an equalityMatch, substrings,
greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch filter
is not recognized by the server, a matching rule id in the
extensibleMatch is not recognized by the server, the assertion
value is invalid, or the type of filtering requested is not
implemented, then the filter is Undefined. Thus for example if a
server did not recognize the attribute type shoeSize, a filter of
(shoeSize=*) would evaluate to FALSE, and the filters
(shoeSize=12), (shoeSize>=12) and (shoeSize<=12) would evaluate to
Undefined.
Servers MUST NOT return errors if attribute descriptions or
matching rule ids are not recognized, 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 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)]:
attributeSelection = noattrs /
*( attributedescription / specialattr )
noattrs = %x31 %x2E %x31 ; "1.1"
specialattr = ASTERISK
ASTERISK = %x2A ; asterisk ("*")
<attributedescription> is defined in Section 2.5 of [Models].
There are two special values which may be used: an empty list with
no attributes, and the attribute description string "*". Both of
these signify that all user attributes are to be returned. (The
"*" allows the client to request all user attributes in addition
to any specified operational attributes). 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 MUST NOT be named more than once in the list, and are
returned at most once in an entry. If there are attribute
descriptions in the list which are not recognized, they are
ignored by the server.
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If the client does not want any attributes returned, it can
specify a list containing only the attribute with OID "1.1". This
OID was chosen because it does not (and can not) correspond to any
attribute in use.
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 {
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
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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 all the entries in the scope at
and subordinate to the baseObject, the server may return one or more
SearchResultReference entries, each containing a reference to another
set of servers for continuing the operation. A server MUST NOT return
any SearchResultReference if it has not located the baseObject and
thus has not searched any entries; in this case it would return a
SearchResultDone containing a referral result code.
If a server holds a copy or partial copy of the subordinate naming
context, 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 an association 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
referral. Note that UTF-8 characters appearing in a DN or search
filter may not be legal for URLs (e.g. spaces) and MUST be
escaped using the % method in [URI].
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- It is RECOMMENDED that the <dn> part be present to avoid
ambiguity.
- 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.
- 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 search request may be the same as or
different from the search request which generated the
SearchResultReference.
- 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 ignore URIs that they
do not support.
4.5.3.1. Example
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 subtree 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 }
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SearchResultReference {
ldap://hostf/OU=Consultants,OU=People,DC=Example,DC=NET??sub }
SearchResultDone (success)
If the contacted server does not hold the base object for the search,
then it will return a referral to the client. For example, if the
client requests a subtree search of "DC=Example,DC=ORG" to hosta, the
server may return only 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 } }
Parameters 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
schema.
- 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
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listed, or if all current values of the attribute are
listed for deletion;
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. Note that due to the
requirement for atomicity in applying the list of modifications in
the Modify Request, the client may expect that no modifications of
the DIT have been performed if the Modify Response received indicates
any sort of error, and that all requested modifications have been
performed if the Modify Response indicates successful completion of
the Modify Operation. If the association changes or the connection
fails, whether the modification occurred or not is indeterminate.
The Modify Operation cannot be used to remove from an entry any of
its distinguished values, 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
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Parameters of the Add Request are:
- entry: the name of the entry to be added. Note that the server
SHALL NOT dereference any aliases in locating the entry to be
added.
- attributes: the list of attributes that make up the content of the
entry being added. Clients MUST include distinguished values
(those forming the entry's own RDN) in this list, the objectClass
attribute, and values of any mandatory attributes of the listed
object classes. Clients MUST NOT supply 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". If the parent entry exists
but is not in a naming context held by the server, the server SHOULD
return a referral to the server holding the parent entry.
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 is present in the
Directory.
4.8. Delete Operation
The Delete Operation allows a client to request the removal of an
entry from the Directory. The Delete Request is defined as follows:
DelRequest ::= [APPLICATION 10] LDAPDN
The Delete Request consists of the 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.
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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:
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 }
Parameters of the Modify DN Request are:
- entry: the name of the entry to be changed. This entry may or may
not have subordinate entries. Note that the server SHALL NOT
dereference any aliases in locating the entry to be changed.
- newrdn: the new RDN of the entry.
- deleteoldrdn: a boolean parameter that controls whether the old
RDN attribute values are to be retained as attributes of the
entry, or deleted from the entry.
- newSuperior: if present, this is the name of an existing object
entry which becomes the immediate superior (parent) of the
existing entry.
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" parameter was "cn=John
Smith,c=US", the newrdn parameter was "cn=John Cougar Smith", and the
newSuperior parameter was absent, then this operation would attempt
to rename the entry to be "cn=John Cougar Smith,c=US". If there was
already an entry with that name, the operation would fail with 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
"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".
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If the deleteoldrdn parameter is TRUE, the values forming the old RDN
are deleted from the entry. If the deleteoldrdn parameter is FALSE,
the values forming the old RDN will be retained as non-distinguished
attribute values of the entry. The server MUST fail the operation and
return an error in the result code if the setting of the deleteoldrdn
parameter would cause a schema inconsistency in the entry.
Note that X.500 restricts the ModifyDN operation to only affect
entries that are contained within a single server. If the LDAP server
is mapped onto DAP, then this restriction will apply, and the
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
provided with an entry in the Directory. The Compare Request is
defined as follows:
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
Parameters of the Compare Request are:
- entry: the name of the entry to be compared. Note that the server
SHALL NOT dereference any aliases in locating the entry to be
compared.
- ava: the assertion with which an attribute in the entry is to be
compared.
Upon receipt of a Compare Request, a server will attempt to perform
the requested comparison using the EQUALITY matching rule for the
attribute type and return the result in the Compare Response, defined
as follows:
CompareResponse ::= [APPLICATION 15] LDAPResult
In the event that the attribute or subtype is not present in the
entry, the resultCode field is set to noSuchAttribute. If the
attribute is unknown, the resultCode is set to
undefinedAttributeType. Note that errors and the result of comparison
are all returned in the same construct.
Note that some directory systems may establish access controls which
permit the values of certain attributes (such as userPassword) to be
compared but not interrogated by other means.
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4.11. Abandon Operation
The function of the Abandon Operation is to allow a client to request
that the server abandon an outstanding operation. The Abandon Request
is defined as follows:
AbandonRequest ::= [APPLICATION 16] MessageID
The MessageID MUST be that of an operation which was requested
earlier in this LDAP association. The abandon request itself has its
own message id. This is distinct from the id of the earlier operation
being abandoned.
There is no response defined in the Abandon operation. Upon receipt
of an AbandonRequest, the server MAY abandon the operation identified
by the MessageID. Operation responses are not sent for successfully
abandoned operations, thus the application of the Abandon operation
is limited to uses where the client does not require an indication of
its outcome.
Abandon and Unbind operations cannot be abandoned. The ability to
abandon other (particularly update) operations is at the discretion
of the server.
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.
Clients MUST NOT send abandon requests for the same operation
multiple times, and MUST also be prepared to receive results from
operations it has abandoned (since these may have been in transit
when the abandon was requested, 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 4.13).
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.
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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 the
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 requestName is not recognized 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 5.1, also follow the extensibility rules in
Section 4.
It is RECOMMENDED that servers list the requestName of extended
operations they support in the supportedExtension attribute [Models]
of the root DSE.
Extended operations may be specified in other documents. The
specification of an extended operation consists of:
- the OBJECT IDENTIFIER assigned to the requestName (and possibly
responseName),
- the format of the contents of the requestValue and responseValue
(if any),
- the semantics of the operation,
4.13. StartTLS Operation
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The Start Transport Layer Security (StartTLS) operation provides the
ability to establish Transport Layer Security ([TLS]) on an LDAP
connection. The StartTLS operation is defined using the extended
operation mechanism described in Section 4.12.
4.13.1. 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 connection following this
request until it receives a StartTLS extended response.
4.13.2. StartTLS Response
When a StartTLS request is made, servers supporting the operation
MUST return a StartTLS response PDU to the requestor. The StartTLS
response responseName is also "1.3.6.1.4.1.1466.20037", and the
response field is absent.
The server MUST set the resultCode field to either success or one of
the other values outlined in Section 4.13.2.2.
4.13.2.1. "Success" Response
If the StartTLS Response contains a result code of success, this
indicates that the server is willing and able to negotiate TLS. Refer
to Section 5.3 of [AuthMeth] for details.
4.13.2.2. Response other than "success"
If the ExtendedResponse contains a result code other than success,
this indicates that the server is unwilling or unable to negotiate
TLS. The following result codes have these meanings for this
operation:
- operationsError: operations sequencing incorrect; e.g. TLS is
already established.
- protocolError: TLS is not supported or incorrect PDU structure.
- unavailable: Some major problem with TLS, or the server is
shutting down.
The server MUST return operationsError if the client violates any of
the StartTLS extended operation sequencing requirements described in
Section 5.3 of [AuthMeth].
If the server does not support TLS (whether by design or by current
configuration), it MUST set the resultCode field to protocolError.
The client's current association is unaffected if the server does not
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support TLS. The client may proceed with any LDAP operation, or it
may close the connection.
The server MUST return unavailable if it supports TLS but cannot
establish a TLS connection for some reason, e.g. the certificate
server not responding, it cannot contact its TLS implementation, or
if the server is in process of shutting down. The client may retry
the StartTLS operation, or it may proceed with any other LDAP
operation, or it may close the LDAP connection.
4.13.3. Closing a TLS Connection
Two forms of TLS connection closure -- graceful and abrupt -- are
supported.
4.13.3.1. Graceful Closure
Either the client or server MAY terminate the TLS connection and
leave the LDAP connection 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 connection intact, it then MUST cease to
send further PDUs and MUST ignore any received 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 underlying LDAP connection intact. In this case,
it MUST immediately transmit a TLS closure alert. Following this, it
MAY send and receive LDAP PDUs.
Protocol peers MAY drop the underlying LDAP connection after sending
or receiving a TLS closure alert.
After the TLS connection has been closed, the server MUST NOT send
responses to any request message received before the TLS closure.
Thus, clients wishing to receive responses to messages sent while the
TLS connection is intact MUST wait for those message responses before
sending the TLS closure alert.
4.13.3.2. Abrupt Closure
Either the client or server MAY abruptly close the TLS connection by
dropping the underlying transfer protocol connection. In this
circumstance, a server MAY send the client a Notice of Disconnection
before dropping the underlying LDAP connection.
5. Protocol Element Encodings and Transfer
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One underlying service, LDAP over TCP, is defined here. This service
is generally applicable to applications providing or consuming X.500-
based directory services on the Internet.
Implementations of LDAP over TCP MUST implement the mapping as
described in Section 5.2.1
5.1. 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:
(1) Only the definite form of length encoding is used.
(2) OCTET STRING values are encoded in the primitive form only.
(3) If the value of a BOOLEAN type is true, the encoding of the
value octet is set to hex "FF".
(4) 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.
5.2. Transfer Protocols
This protocol is designed to run over connection-oriented, reliable
transports, with all 8 bits in an octet being significant in the data
stream.
5.2.1. Transmission Control Protocol (TCP)
The encoded LDAPMessage PDUs are mapped directly onto the [TCP]
bytestream using the BER-based encoding described in Section 5.1. It
is recommended that server implementations running over the TCP
provide a protocol listener on the assigned port, 389. Servers may
instead provide a listener on a different port number. Clients MUST
support contacting servers on any valid TCP port.
6. Security Considerations
This version of the protocol provides facilities for simple
authentication using a cleartext password, as well as any [SASL]
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mechanism. SASL allows for integrity and privacy services to be
negotiated.
It is also permitted that the server can return its credentials to
the client, if it chooses to do so.
Use of cleartext password is strongly discouraged where the
underlying transport service cannot guarantee confidentiality and may
result in disclosure of the password to unauthorized parties.
Servers are encouraged to prevent directory modifications by clients
that have authenticated anonymously [AuthMeth].
Requirements of 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
protected (such as by establishing protections at the transport
layer).
Server implementors should plan for the possibility of an identity
associated with an LDAP connection being deleted, renamed, or
modified, and take appropriate actions to prevent insecure side
effects. Likewise, server implementors should plan for the
possibility of an associated identity's credentials becoming invalid,
or an identities privileges being changed. The way 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.
Protocol servers may return referrals which redirect protocol 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. Protocol clients are advised to be aware of
this, and possibly reject referrals when confidentiality measures are
not in place. Protocol clients are advised to reject referrals from
the StartTLS operation.
Protocol peers MUST be prepared to handle invalid and arbitrary
length protocol encodings. A number of LDAP security advisories are
available through [CERT].
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7. Acknowledgements
This document updates RFC 2251 by Mark Wahl, Tim Howes, and Steve
Kille. It also updates RFC 2830 by Jeff Hodges, RL "Bob" Morgan, and
Mark Wahl. Their work along with the input of individuals of the IETF
ASID, LDAPEXT, LDUP, LDAPBIS, and other Working Groups is gratefully
acknowledged.
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).
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[SASL] Melnikov, A., "Simple Authentication and Security Layer",
draft-ietf-sasl-rfc2222bis-xx.txt (a work in progress).
[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 Unicode
and ISO 10646", STD63 and RFC3629.
[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
[CERT] the CERT(R) Center, (http://www.cert.org)
10. IANA Considerations
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It is requested that the Internet Assigned Numbers Authority (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 4.1.10.
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),
compareTrue (6),
compareFalse (7),
referral (10), and
saslBindInProgress (14).
The success, compareTrue, and compare 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
compareTrue (5) and compareFalse (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 [RFC2246] while there are other operations
outstanding or if TLS was already established.
protocolError (2)
Indicates the server received data which has incorrect
structure.
For bind operation only, this code is also used to indicate
that the server does not support the requested protocol
version.
timeLimitExceeded (3)
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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.
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 4.1.11).
adminLimitExceeded (11)
Indicates that an administrative limit has been exceeded.
unavailableCriticalExtension (12)
Indicates that the server is unable or unwilling to perform a
critical extension (see Section 4.1.12).
confidentialityRequired (13)
Indicates that data confidentiality protections are required.
saslBindInProgress (14)
Indicates the server requires the client to send a new bind
request, with the same SASL mechanism, to continue the
authentication process (see 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)
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Indicates that an attempt was made, e.g. in a filter, 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.
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)
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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.
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.
affectsMultipleDSAs (71)
Indicates that the operation cannot be completed as it
affects 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 (2003). 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,
... },
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
RelativeLDAPDN ::= LDAPString
AttributeDescription ::= LDAPString
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-- 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 --
inappropriateAuthentication (48),
invalidCredentials (49),
insufficientAccessRights (50),
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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),
... },
-- 81-90 reserved for APIs --
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 }
UnbindRequest ::= [APPLICATION 2] NULL
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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 selection LDAPString
Filter ::= CHOICE {
and [0] SET SIZE (1..MAX) OF filter Filter,
or [1] SET SIZE (1..MAX) 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 }
PartialAttributeList ::= SEQUENCE OF
partialAttribute PartialAttribute
SearchResultReference ::= [APPLICATION 19] SEQUENCE
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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,
responseValue [11] 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 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
- 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 4.1.6
- Removed references to the "binary" encoding as it has been removed
from the specification.
C.1.9 Section 4.1.7
- Removed references to the "binary" encoding as it has been removed
from the specification.
C.1.10 Section 4.1.8
- Combined the definitions of PartialAttribute and Attribute here,
and defined Attribute in terms of PartialAttribute.
C.1.11 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.1.12 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.
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C.1.13 Section 4.1.12
- Specified how control values defined in terms of ASN.1 are to be
encoded.
- Added language regarding combinations of controls on a message.
- 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.1.14 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.1.15 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].
C.1.16 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.1.17 Section 4.3
- Required both peers to cease transmission and close the connection
for the unbind operation.
C.1.18 Section 4.4
- Added instructions for future specifications of Unsolicited
Notifications.
C.1.19 Section 4.5.1
- SearchRequest attributes is now defined as an AttributeSelection
type rather than AttributeDescriptionList.
- The Filter choices 'and' and 'or', and the SubstringFilter
substrings types are now defined with a lower bound of 1.
- The SubstringFilter substrings 'initial, 'any', and 'final' types
are now AssertionValue rather than LDAPString.
- Clarified the semantics of the derefAliases choices.
- Added instructions for equalityMatch, substrings, greaterOrEqual,
lessOrEqual, and approxMatch.
C.1.20 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.1.21 Section 4.5.3
- Made changes similar to those made to Section 4.1.11.
C.1.22 Section 4.5.3.1
- Fixed examples to adhere to changes made to Section 4.5.3.
C.1.23 Section 4.6
- Removed restriction that required an equality match filter 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.
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- Clarified what type of modification changes might temporarily
violate schema.
C.1.24 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.
C.1.25 Section 4.10
- Clarified the semantics of Compare when the attribute is not
present and when it is unknown.
- Required servers to not dereference aliases for compare. This was
added for consistency with other operations and to help ensure
data consistency.
C.1.26 Section 4.11
- Explained that since abandon returns no response, clients hould
not use it if they need to know the outcome.
- Specified that Abandon and Unbind cannot be abandoned.
C.1.27 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.
C.1.28 Section 5.2
- Moved referral-specific instructions into referral-related
sections.
C.1.29 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.).
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- Warned against following referrals that may have been injected in
the data stream.
- Added a note regarding malformed and long encodings.
C.1.30 Appendix A
- Added "EXTESIBILITY IMPLIED" to ASN.1 definition.
- Removed AttributeType. It is not used.
C.2 Changes made to 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
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.
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Intellectual Property Rights
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
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The limited permissions granted above are perpetual and will not be
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This document and the information contained herein is provided on an
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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