7 Network Working Group J. Sermersheim, Ed.
8 Request for Comments: 4511 Novell, Inc.
9 Obsoletes: 2251, 2830, 3771 June 2006
10 Category: Standards Track
13 Lightweight Directory Access Protocol (LDAP): The Protocol
17 This document specifies an Internet standards track protocol for the
18 Internet community, and requests discussion and suggestions for
19 improvements. Please refer to the current edition of the "Internet
20 Official Protocol Standards" (STD 1) for the standardization state
21 and status of this protocol. Distribution of this memo is unlimited.
25 Copyright (C) The Internet Society (2006).
29 This document describes the protocol elements, along with their
30 semantics and encodings, of the Lightweight Directory Access Protocol
31 (LDAP). LDAP provides access to distributed directory services that
32 act in accordance with X.500 data and service models. These protocol
33 elements are based on those described in the X.500 Directory Access
38 1. Introduction ....................................................3
39 1.1. Relationship to Other LDAP Specifications ..................3
40 2. Conventions .....................................................3
41 3. Protocol Model ..................................................4
42 3.1. Operation and LDAP Message Layer Relationship ..............5
43 4. Elements of Protocol ............................................5
44 4.1. Common Elements ............................................5
45 4.1.1. Message Envelope ....................................6
46 4.1.2. String Types ........................................7
47 4.1.3. Distinguished Name and Relative Distinguished Name ..8
48 4.1.4. Attribute Descriptions ..............................8
49 4.1.5. Attribute Value .....................................8
50 4.1.6. Attribute Value Assertion ...........................9
51 4.1.7. Attribute and PartialAttribute ......................9
52 4.1.8. Matching Rule Identifier ...........................10
53 4.1.9. Result Message .....................................10
54 4.1.10. Referral ..........................................12
58 Sermersheim Standards Track [Page 1]
60 RFC 4511 LDAPv3 June 2006
63 4.1.11. Controls ..........................................14
64 4.2. Bind Operation ............................................16
65 4.2.1. Processing of the Bind Request .....................17
66 4.2.2. Bind Response ......................................18
67 4.3. Unbind Operation ..........................................18
68 4.4. Unsolicited Notification ..................................19
69 4.4.1. Notice of Disconnection ............................19
70 4.5. Search Operation ..........................................20
71 4.5.1. Search Request .....................................20
72 4.5.2. Search Result ......................................27
73 4.5.3. Continuation References in the Search Result .......28
74 4.6. Modify Operation ..........................................31
75 4.7. Add Operation .............................................33
76 4.8. Delete Operation ..........................................34
77 4.9. Modify DN Operation .......................................34
78 4.10. Compare Operation ........................................36
79 4.11. Abandon Operation ........................................36
80 4.12. Extended Operation .......................................37
81 4.13. IntermediateResponse Message .............................39
82 4.13.1. Usage with LDAP ExtendedRequest and
83 ExtendedResponse ..................................40
84 4.13.2. Usage with LDAP Request Controls ..................40
85 4.14. StartTLS Operation .......................................40
86 4.14.1. StartTLS Request ..................................40
87 4.14.2. StartTLS Response .................................41
88 4.14.3. Removal of the TLS Layer ..........................41
89 5. Protocol Encoding, Connection, and Transfer ....................42
90 5.1. Protocol Encoding .........................................42
91 5.2. Transmission Control Protocol (TCP) .......................43
92 5.3. Termination of the LDAP session ...........................43
93 6. Security Considerations ........................................43
94 7. Acknowledgements ...............................................45
95 8. Normative References ...........................................46
96 9. Informative References .........................................48
97 10. IANA Considerations ...........................................48
98 Appendix A. LDAP Result Codes .....................................49
99 A.1. Non-Error Result Codes ....................................49
100 A.2. Result Codes ..............................................49
101 Appendix B. Complete ASN.1 Definition .............................54
102 Appendix C. Changes ...............................................60
103 C.1. Changes Made to RFC 2251 ..................................60
104 C.2. Changes Made to RFC 2830 ..................................66
105 C.3. Changes Made to RFC 3771 ..................................66
114 Sermersheim Standards Track [Page 2]
116 RFC 4511 LDAPv3 June 2006
121 The Directory is "a collection of open systems cooperating to provide
122 directory services" [X.500]. A directory user, which may be a human
123 or other entity, accesses the Directory through a client (or
124 Directory User Agent (DUA)). The client, on behalf of the directory
125 user, interacts with one or more servers (or Directory System Agents
126 (DSA)). Clients interact with servers using a directory access
129 This document details the protocol elements of the Lightweight
130 Directory Access Protocol (LDAP), along with their semantics.
131 Following the description of protocol elements, it describes the way
132 in which the protocol elements are encoded and transferred.
134 1.1. Relationship to Other LDAP Specifications
136 This document is an integral part of the LDAP Technical Specification
137 [RFC4510], which obsoletes the previously defined LDAP technical
138 specification, RFC 3377, in its entirety.
140 This document, together with [RFC4510], [RFC4513], and [RFC4512],
141 obsoletes RFC 2251 in its entirety. Section 3.3 is obsoleted by
142 [RFC4510]. Sections 4.2.1 (portions) and 4.2.2 are obsoleted by
143 [RFC4513]. Sections 3.2, 3.4, 4.1.3 (last paragraph), 4.1.4, 4.1.5,
144 4.1.5.1, 4.1.9 (last paragraph), 5.1, 6.1, and 6.2 (last paragraph)
145 are obsoleted by [RFC4512]. The remainder of RFC 2251 is obsoleted
146 by this document. Appendix C.1 summarizes substantive changes in the
149 This document obsoletes RFC 2830, Sections 2 and 4. The remainder of
150 RFC 2830 is obsoleted by [RFC4513]. Appendix C.2 summarizes
151 substantive changes to the remaining sections.
153 This document also obsoletes RFC 3771 in entirety.
157 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
158 "SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY" in this document are
159 to be interpreted as described in [RFC2119].
161 Character names in this document use the notation for code points and
162 names from the Unicode Standard [Unicode]. For example, the letter
163 "a" may be represented as either <U+0061> or <LATIN SMALL LETTER A>.
170 Sermersheim Standards Track [Page 3]
172 RFC 4511 LDAPv3 June 2006
175 Note: a glossary of terms used in Unicode can be found in [Glossary].
176 Information on the Unicode character encoding model can be found in
179 The term "transport connection" refers to the underlying transport
180 services used to carry the protocol exchange, as well as associations
181 established by these services.
183 The term "TLS layer" refers to Transport Layer Security (TLS)
184 services used in providing security services, as well as associations
185 established by these services.
187 The term "SASL layer" refers to Simply Authentication and Security
188 Layer (SASL) services used in providing security services, as well as
189 associations established by these services.
191 The term "LDAP message layer" refers to the LDAP Message Protocol
192 Data Unit (PDU) services used in providing directory services, as
193 well as associations established by these services.
195 The term "LDAP session" refers to combined services (transport
196 connection, TLS layer, SASL layer, LDAP message layer) and their
199 See the table in Section 5 for an illustration of these four terms.
203 The general model adopted by this protocol is one of clients
204 performing protocol operations against servers. In this model, a
205 client transmits a protocol request describing the operation to be
206 performed to a server. The server is then responsible for performing
207 the necessary operation(s) in the Directory. Upon completion of an
208 operation, the server typically returns a response containing
209 appropriate data to the requesting client.
211 Protocol operations are generally independent of one another. Each
212 operation is processed as an atomic action, leaving the directory in
215 Although servers are required to return responses whenever such
216 responses are defined in the protocol, there is no requirement for
217 synchronous behavior on the part of either clients or servers.
218 Requests and responses for multiple operations generally may be
219 exchanged between a client and server in any order. If required,
220 synchronous behavior may be controlled by client applications.
226 Sermersheim Standards Track [Page 4]
228 RFC 4511 LDAPv3 June 2006
231 The core protocol operations defined in this document can be mapped
232 to a subset of the X.500 (1993) Directory Abstract Service [X.511].
233 However, there is not a one-to-one mapping between LDAP operations
234 and X.500 Directory Access Protocol (DAP) operations. Server
235 implementations acting as a gateway to X.500 directories may need to
236 make multiple DAP requests to service a single LDAP request.
238 3.1. Operation and LDAP Message Layer Relationship
240 Protocol operations are exchanged at the LDAP message layer. When
241 the transport connection is closed, any uncompleted operations at the
242 LDAP message layer are abandoned (when possible) or are completed
243 without transmission of the response (when abandoning them is not
244 possible). Also, when the transport connection is closed, the client
245 MUST NOT assume that any uncompleted update operations have succeeded
248 4. Elements of Protocol
250 The protocol is described using Abstract Syntax Notation One
251 ([ASN.1]) and is transferred using a subset of ASN.1 Basic Encoding
252 Rules ([BER]). Section 5 specifies how the protocol elements are
253 encoded and transferred.
255 In order to support future extensions to this protocol, extensibility
256 is implied where it is allowed per ASN.1 (i.e., sequence, set,
257 choice, and enumerated types are extensible). In addition, ellipses
258 (...) have been supplied in ASN.1 types that are explicitly
259 extensible as discussed in [RFC4520]. Because of the implied
260 extensibility, clients and servers MUST (unless otherwise specified)
261 ignore trailing SEQUENCE components whose tags they do not recognize.
263 Changes to the protocol other than through the extension mechanisms
264 described here require a different version number. A client
265 indicates the version it is using as part of the BindRequest,
266 described in Section 4.2. If a client has not sent a Bind, the
267 server MUST assume the client is using version 3 or later.
269 Clients may attempt to determine the protocol versions a server
270 supports by reading the 'supportedLDAPVersion' attribute from the
271 root DSE (DSA-Specific Entry) [RFC4512].
275 This section describes the LDAPMessage envelope Protocol Data Unit
276 (PDU) format, as well as data type definitions, which are used in the
282 Sermersheim Standards Track [Page 5]
284 RFC 4511 LDAPv3 June 2006
287 4.1.1. Message Envelope
289 For the purposes of protocol exchanges, all protocol operations are
290 encapsulated in a common envelope, the LDAPMessage, which is defined
293 LDAPMessage ::= SEQUENCE {
296 bindRequest BindRequest,
297 bindResponse BindResponse,
298 unbindRequest UnbindRequest,
299 searchRequest SearchRequest,
300 searchResEntry SearchResultEntry,
301 searchResDone SearchResultDone,
302 searchResRef SearchResultReference,
303 modifyRequest ModifyRequest,
304 modifyResponse ModifyResponse,
305 addRequest AddRequest,
306 addResponse AddResponse,
307 delRequest DelRequest,
308 delResponse DelResponse,
309 modDNRequest ModifyDNRequest,
310 modDNResponse ModifyDNResponse,
311 compareRequest CompareRequest,
312 compareResponse CompareResponse,
313 abandonRequest AbandonRequest,
314 extendedReq ExtendedRequest,
315 extendedResp ExtendedResponse,
317 intermediateResponse IntermediateResponse },
318 controls [0] Controls OPTIONAL }
320 MessageID ::= INTEGER (0 .. maxInt)
322 maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
324 The ASN.1 type Controls is defined in Section 4.1.11.
326 The function of the LDAPMessage is to provide an envelope containing
327 common fields required in all protocol exchanges. At this time, the
328 only common fields are the messageID and the controls.
330 If the server receives an LDAPMessage from the client in which the
331 LDAPMessage SEQUENCE tag cannot be recognized, the messageID cannot
332 be parsed, the tag of the protocolOp is not recognized as a request,
333 or the encoding structures or lengths of data fields are found to be
334 incorrect, then the server SHOULD return the Notice of Disconnection
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340 RFC 4511 LDAPv3 June 2006
343 described in Section 4.4.1, with the resultCode set to protocolError,
344 and MUST immediately terminate the LDAP session as described in
347 In other cases where the client or server cannot parse an LDAP PDU,
348 it SHOULD abruptly terminate the LDAP session (Section 5.3) where
349 further communication (including providing notice) would be
350 pernicious. Otherwise, server implementations MUST return an
351 appropriate response to the request, with the resultCode set to
356 All LDAPMessage envelopes encapsulating responses contain the
357 messageID value of the corresponding request LDAPMessage.
359 The messageID of a request MUST have a non-zero value different from
360 the messageID of any other request in progress in the same LDAP
361 session. The zero value is reserved for the unsolicited notification
364 Typical clients increment a counter for each request.
366 A client MUST NOT send a request with the same messageID as an
367 earlier request in the same LDAP session unless it can be determined
368 that the server is no longer servicing the earlier request (e.g.,
369 after the final response is received, or a subsequent Bind
370 completes). Otherwise, the behavior is undefined. For this purpose,
371 note that Abandon and successfully abandoned operations do not send
376 The LDAPString is a notational convenience to indicate that, although
377 strings of LDAPString type encode as ASN.1 OCTET STRING types, the
378 [ISO10646] character set (a superset of [Unicode]) is used, encoded
379 following the UTF-8 [RFC3629] algorithm. Note that Unicode
380 characters U+0000 through U+007F are the same as ASCII 0 through 127,
381 respectively, and have the same single octet UTF-8 encoding. Other
382 Unicode characters have a multiple octet UTF-8 encoding.
384 LDAPString ::= OCTET STRING -- UTF-8 encoded,
385 -- [ISO10646] characters
387 The LDAPOID is a notational convenience to indicate that the
388 permitted value of this string is a (UTF-8 encoded) dotted-decimal
389 representation of an OBJECT IDENTIFIER. Although an LDAPOID is
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396 RFC 4511 LDAPv3 June 2006
399 encoded as an OCTET STRING, values are limited to the definition of
400 <numericoid> given in Section 1.4 of [RFC4512].
402 LDAPOID ::= OCTET STRING -- Constrained to <numericoid>
407 1.3.6.1.4.1.1466.1.2.3
409 4.1.3. Distinguished Name and Relative Distinguished Name
411 An LDAPDN is defined to be the representation of a Distinguished Name
412 (DN) after encoding according to the specification in [RFC4514].
414 LDAPDN ::= LDAPString
415 -- Constrained to <distinguishedName> [RFC4514]
417 A RelativeLDAPDN is defined to be the representation of a Relative
418 Distinguished Name (RDN) after encoding according to the
419 specification in [RFC4514].
421 RelativeLDAPDN ::= LDAPString
422 -- Constrained to <name-component> [RFC4514]
424 4.1.4. Attribute Descriptions
426 The definition and encoding rules for attribute descriptions are
427 defined in Section 2.5 of [RFC4512]. Briefly, an attribute
428 description is an attribute type and zero or more options.
430 AttributeDescription ::= LDAPString
431 -- Constrained to <attributedescription>
434 4.1.5. Attribute Value
436 A field of type AttributeValue is an OCTET STRING containing an
437 encoded attribute value. The attribute value is encoded according to
438 the LDAP-specific encoding definition of its corresponding syntax.
439 The LDAP-specific encoding definitions for different syntaxes and
440 attribute types may be found in other documents and in particular
443 AttributeValue ::= OCTET STRING
450 Sermersheim Standards Track [Page 8]
452 RFC 4511 LDAPv3 June 2006
455 Note that there is no defined limit on the size of this encoding;
456 thus, protocol values may include multi-megabyte attribute values
459 Attribute values may be defined that have arbitrary and non-printable
460 syntax. Implementations MUST NOT display or attempt to decode an
461 attribute value if its syntax is not known. The implementation may
462 attempt to discover the subschema of the source entry and to retrieve
463 the descriptions of 'attributeTypes' from it [RFC4512].
465 Clients MUST only send attribute values in a request that are valid
466 according to the syntax defined for the attributes.
468 4.1.6. Attribute Value Assertion
470 The AttributeValueAssertion (AVA) type definition is similar to the
471 one in the X.500 Directory standards. It contains an attribute
472 description and a matching rule ([RFC4512], Section 4.1.3) assertion
473 value suitable for that type. Elements of this type are typically
474 used to assert that the value in assertionValue matches a value of an
477 AttributeValueAssertion ::= SEQUENCE {
478 attributeDesc AttributeDescription,
479 assertionValue AssertionValue }
481 AssertionValue ::= OCTET STRING
483 The syntax of the AssertionValue depends on the context of the LDAP
484 operation being performed. For example, the syntax of the EQUALITY
485 matching rule for an attribute is used when performing a Compare
486 operation. Often this is the same syntax used for values of the
487 attribute type, but in some cases the assertion syntax differs from
488 the value syntax. See objectIdentiferFirstComponentMatch in
489 [RFC4517] for an example.
491 4.1.7. Attribute and PartialAttribute
493 Attributes and partial attributes consist of an attribute description
494 and attribute values. A PartialAttribute allows zero values, while
495 Attribute requires at least one value.
497 PartialAttribute ::= SEQUENCE {
498 type AttributeDescription,
499 vals SET OF value AttributeValue }
506 Sermersheim Standards Track [Page 9]
508 RFC 4511 LDAPv3 June 2006
511 Attribute ::= PartialAttribute(WITH COMPONENTS {
513 vals (SIZE(1..MAX))})
515 No two of the attribute values may be equivalent as described by
516 Section 2.2 of [RFC4512]. The set of attribute values is unordered.
517 Implementations MUST NOT rely upon the ordering being repeatable.
519 4.1.8. Matching Rule Identifier
521 Matching rules are defined in Section 4.1.3 of [RFC4512]. A matching
522 rule is identified in the protocol by the printable representation of
523 either its <numericoid> or one of its short name descriptors
524 [RFC4512], e.g., 'caseIgnoreMatch' or '2.5.13.2'.
526 MatchingRuleId ::= LDAPString
528 4.1.9. Result Message
530 The LDAPResult is the construct used in this protocol to return
531 success or failure indications from servers to clients. To various
532 requests, servers will return responses containing the elements found
533 in LDAPResult to indicate the final status of the protocol operation
536 LDAPResult ::= SEQUENCE {
537 resultCode ENUMERATED {
541 timeLimitExceeded (3),
542 sizeLimitExceeded (4),
545 authMethodNotSupported (7),
546 strongerAuthRequired (8),
549 adminLimitExceeded (11),
550 unavailableCriticalExtension (12),
551 confidentialityRequired (13),
552 saslBindInProgress (14),
553 noSuchAttribute (16),
554 undefinedAttributeType (17),
555 inappropriateMatching (18),
556 constraintViolation (19),
557 attributeOrValueExists (20),
558 invalidAttributeSyntax (21),
562 Sermersheim Standards Track [Page 10]
564 RFC 4511 LDAPv3 June 2006
570 invalidDNSyntax (34),
571 -- 35 reserved for undefined isLeaf --
572 aliasDereferencingProblem (36),
574 inappropriateAuthentication (48),
575 invalidCredentials (49),
576 insufficientAccessRights (50),
579 unwillingToPerform (53),
582 namingViolation (64),
583 objectClassViolation (65),
584 notAllowedOnNonLeaf (66),
585 notAllowedOnRDN (67),
586 entryAlreadyExists (68),
587 objectClassModsProhibited (69),
588 -- 70 reserved for CLDAP --
589 affectsMultipleDSAs (71),
594 diagnosticMessage LDAPString,
595 referral [3] Referral OPTIONAL }
597 The resultCode enumeration is extensible as defined in Section 3.8 of
598 [RFC4520]. The meanings of the listed result codes are given in
599 Appendix A. If a server detects multiple errors for an operation,
600 only one result code is returned. The server should return the
601 result code that best indicates the nature of the error encountered.
602 Servers may return substituted result codes to prevent unauthorized
605 The diagnosticMessage field of this construct may, at the server's
606 option, be used to return a string containing a textual, human-
607 readable diagnostic message (terminal control and page formatting
608 characters should be avoided). As this diagnostic message is not
609 standardized, implementations MUST NOT rely on the values returned.
610 Diagnostic messages typically supplement the resultCode with
611 additional information. If the server chooses not to return a
612 textual diagnostic, the diagnosticMessage field MUST be empty.
618 Sermersheim Standards Track [Page 11]
620 RFC 4511 LDAPv3 June 2006
623 For certain result codes (typically, but not restricted to
624 noSuchObject, aliasProblem, invalidDNSyntax, and
625 aliasDereferencingProblem), the matchedDN field is set (subject to
626 access controls) to the name of the last entry (object or alias) used
627 in finding the target (or base) object. This will be a truncated
628 form of the provided name or, if an alias was dereferenced while
629 attempting to locate the entry, of the resulting name. Otherwise,
630 the matchedDN field is empty.
634 The referral result code indicates that the contacted server cannot
635 or will not perform the operation and that one or more other servers
636 may be able to. Reasons for this include:
638 - The target entry of the request is not held locally, but the server
639 has knowledge of its possible existence elsewhere.
641 - The operation is restricted on this server -- perhaps due to a
642 read-only copy of an entry to be modified.
644 The referral field is present in an LDAPResult if the resultCode is
645 set to referral, and it is absent with all other result codes. It
646 contains one or more references to one or more servers or services
647 that may be accessed via LDAP or other protocols. Referrals can be
648 returned in response to any operation request (except Unbind and
649 Abandon, which do not have responses). At least one URI MUST be
650 present in the Referral.
652 During a Search operation, after the baseObject is located, and
653 entries are being evaluated, the referral is not returned. Instead,
654 continuation references, described in Section 4.5.3, are returned
655 when other servers would need to be contacted to complete the
658 Referral ::= SEQUENCE SIZE (1..MAX) OF uri URI
660 URI ::= LDAPString -- limited to characters permitted in
663 If the client wishes to progress the operation, it contacts one of
664 the supported services found in the referral. If multiple URIs are
665 present, the client assumes that any supported URI may be used to
666 progress the operation.
668 Clients that follow referrals MUST ensure that they do not loop
669 between servers. They MUST NOT repeatedly contact the same server
670 for the same request with the same parameters. Some clients use a
674 Sermersheim Standards Track [Page 12]
676 RFC 4511 LDAPv3 June 2006
679 counter that is incremented each time referral handling occurs for an
680 operation, and these kinds of clients MUST be able to handle at least
681 ten nested referrals while progressing the operation.
683 A URI for a server implementing LDAP and accessible via TCP/IP (v4 or
684 v6) [RFC793][RFC791] is written as an LDAP URL according to
687 Referral values that are LDAP URLs follow these rules:
689 - If an alias was dereferenced, the <dn> part of the LDAP URL MUST be
690 present, with the new target object name.
692 - It is RECOMMENDED that the <dn> part be present to avoid ambiguity.
694 - If the <dn> part is present, the client uses this name in its next
695 request to progress the operation, and if it is not present the
696 client uses the same name as in the original request.
698 - Some servers (e.g., participating in distributed indexing) may
699 provide a different filter in a URL of a referral for a Search
702 - If the <filter> part of the LDAP URL is present, the client uses
703 this filter in its next request to progress this Search, and if it
704 is not present the client uses the same filter as it used for that
707 - For Search, it is RECOMMENDED that the <scope> part be present to
710 - If the <scope> part is missing, the scope of the original Search is
711 used by the client to progress the operation.
713 - Other aspects of the new request may be the same as or different
714 from the request that generated the referral.
716 Other kinds of URIs may be returned. The syntax and semantics of
717 such URIs is left to future specifications. Clients may ignore URIs
718 that they do not support.
720 UTF-8 encoded characters appearing in the string representation of a
721 DN, search filter, or other fields of the referral value may not be
722 legal for URIs (e.g., spaces) and MUST be escaped using the % method
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732 RFC 4511 LDAPv3 June 2006
737 Controls provide a mechanism whereby the semantics and arguments of
738 existing LDAP operations may be extended. One or more controls may
739 be attached to a single LDAP message. A control only affects the
740 semantics of the message it is attached to.
742 Controls sent by clients are termed 'request controls', and those
743 sent by servers are termed 'response controls'.
745 Controls ::= SEQUENCE OF control Control
747 Control ::= SEQUENCE {
749 criticality BOOLEAN DEFAULT FALSE,
750 controlValue OCTET STRING OPTIONAL }
752 The controlType field is the dotted-decimal representation of an
753 OBJECT IDENTIFIER that uniquely identifies the control. This
754 provides unambiguous naming of controls. Often, response control(s)
755 solicited by a request control share controlType values with the
758 The criticality field only has meaning in controls attached to
759 request messages (except UnbindRequest). For controls attached to
760 response messages and the UnbindRequest, the criticality field SHOULD
761 be FALSE, and MUST be ignored by the receiving protocol peer. A
762 value of TRUE indicates that it is unacceptable to perform the
763 operation without applying the semantics of the control.
764 Specifically, the criticality field is applied as follows:
766 - If the server does not recognize the control type, determines that
767 it is not appropriate for the operation, or is otherwise unwilling
768 to perform the operation with the control, and if the criticality
769 field is TRUE, the server MUST NOT perform the operation, and for
770 operations that have a response message, it MUST return with the
771 resultCode set to unavailableCriticalExtension.
773 - If the server does not recognize the control type, determines that
774 it is not appropriate for the operation, or is otherwise unwilling
775 to perform the operation with the control, and if the criticality
776 field is FALSE, the server MUST ignore the control.
778 - Regardless of criticality, if a control is applied to an
779 operation, it is applied consistently and impartially to the
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788 RFC 4511 LDAPv3 June 2006
791 The controlValue may contain information associated with the
792 controlType. Its format is defined by the specification of the
793 control. Implementations MUST be prepared to handle arbitrary
794 contents of the controlValue octet string, including zero bytes. It
795 is absent only if there is no value information that is associated
796 with a control of its type. When a controlValue is defined in terms
797 of ASN.1, and BER-encoded according to Section 5.1, it also follows
798 the extensibility rules in Section 4.
800 Servers list the controlType of request controls they recognize in
801 the 'supportedControl' attribute in the root DSE (Section 5.1 of
804 Controls SHOULD NOT be combined unless the semantics of the
805 combination has been specified. The semantics of control
806 combinations, if specified, are generally found in the control
807 specification most recently published. When a combination of
808 controls is encountered whose semantics are invalid, not specified
809 (or not known), the message is considered not well-formed; thus, the
810 operation fails with protocolError. Controls with a criticality of
811 FALSE may be ignored in order to arrive at a valid combination.
812 Additionally, unless order-dependent semantics are given in a
813 specification, the order of a combination of controls in the SEQUENCE
814 is ignored. Where the order is to be ignored but cannot be ignored
815 by the server, the message is considered not well-formed, and the
816 operation fails with protocolError. Again, controls with a
817 criticality of FALSE may be ignored in order to arrive at a valid
820 This document does not specify any controls. Controls may be
821 specified in other documents. Documents detailing control extensions
822 are to provide for each control:
824 - the OBJECT IDENTIFIER assigned to the control,
826 - direction as to what value the sender should provide for the
827 criticality field (note: the semantics of the criticality field are
828 defined above should not be altered by the control's
831 - whether the controlValue field is present, and if so, the format of
834 - the semantics of the control, and
836 - optionally, semantics regarding the combination of the control with
842 Sermersheim Standards Track [Page 15]
844 RFC 4511 LDAPv3 June 2006
849 The function of the Bind operation is to allow authentication
850 information to be exchanged between the client and server. The Bind
851 operation should be thought of as the "authenticate" operation.
852 Operational, authentication, and security-related semantics of this
853 operation are given in [RFC4513].
855 The Bind request is defined as follows:
857 BindRequest ::= [APPLICATION 0] SEQUENCE {
858 version INTEGER (1 .. 127),
860 authentication AuthenticationChoice }
862 AuthenticationChoice ::= CHOICE {
863 simple [0] OCTET STRING,
865 sasl [3] SaslCredentials,
868 SaslCredentials ::= SEQUENCE {
869 mechanism LDAPString,
870 credentials OCTET STRING OPTIONAL }
872 Fields of the BindRequest are:
874 - version: A version number indicating the version of the protocol to
875 be used at the LDAP message layer. This document describes version
876 3 of the protocol. There is no version negotiation. The client
877 sets this field to the version it desires. If the server does not
878 support the specified version, it MUST respond with a BindResponse
879 where the resultCode is set to protocolError.
881 - name: If not empty, the name of the Directory object that the
882 client wishes to bind as. This field may take on a null value (a
883 zero-length string) for the purposes of anonymous binds ([RFC4513],
884 Section 5.1) or when using SASL [RFC4422] authentication
885 ([RFC4513], Section 5.2). Where the server attempts to locate the
886 named object, it SHALL NOT perform alias dereferencing.
888 - authentication: Information used in authentication. This type is
889 extensible as defined in Section 3.7 of [RFC4520]. Servers that do
890 not support a choice supplied by a client return a BindResponse
891 with the resultCode set to authMethodNotSupported.
898 Sermersheim Standards Track [Page 16]
900 RFC 4511 LDAPv3 June 2006
903 Textual passwords (consisting of a character sequence with a known
904 character set and encoding) transferred to the server using the
905 simple AuthenticationChoice SHALL be transferred as UTF-8 [RFC3629]
906 encoded [Unicode]. Prior to transfer, clients SHOULD prepare text
907 passwords as "query" strings by applying the SASLprep [RFC4013]
908 profile of the stringprep [RFC3454] algorithm. Passwords
909 consisting of other data (such as random octets) MUST NOT be
910 altered. The determination of whether a password is textual is a
913 4.2.1. Processing of the Bind Request
915 Before processing a BindRequest, all uncompleted operations MUST
916 either complete or be abandoned. The server may either wait for the
917 uncompleted operations to complete, or abandon them. The server then
918 proceeds to authenticate the client in either a single-step or
919 multi-step Bind process. Each step requires the server to return a
920 BindResponse to indicate the status of authentication.
922 After sending a BindRequest, clients MUST NOT send further LDAP PDUs
923 until receiving the BindResponse. Similarly, servers SHOULD NOT
924 process or respond to requests received while processing a
927 If the client did not bind before sending a request and receives an
928 operationsError to that request, it may then send a BindRequest. If
929 this also fails or the client chooses not to bind on the existing
930 LDAP session, it may terminate the LDAP session, re-establish it, and
931 begin again by first sending a BindRequest. This will aid in
932 interoperating with servers implementing other versions of LDAP.
934 Clients may send multiple Bind requests to change the authentication
935 and/or security associations or to complete a multi-stage Bind
936 process. Authentication from earlier binds is subsequently ignored.
938 For some SASL authentication mechanisms, it may be necessary for the
939 client to invoke the BindRequest multiple times ([RFC4513], Section
940 5.2). Clients MUST NOT invoke operations between two Bind requests
941 made as part of a multi-stage Bind.
943 A client may abort a SASL bind negotiation by sending a BindRequest
944 with a different value in the mechanism field of SaslCredentials, or
945 an AuthenticationChoice other than sasl.
954 Sermersheim Standards Track [Page 17]
956 RFC 4511 LDAPv3 June 2006
959 If the client sends a BindRequest with the sasl mechanism field as an
960 empty string, the server MUST return a BindResponse with the
961 resultCode set to authMethodNotSupported. This will allow the client
962 to abort a negotiation if it wishes to try again with the same SASL
967 The Bind response is defined as follows.
969 BindResponse ::= [APPLICATION 1] SEQUENCE {
970 COMPONENTS OF LDAPResult,
971 serverSaslCreds [7] OCTET STRING OPTIONAL }
973 BindResponse consists simply of an indication from the server of the
974 status of the client's request for authentication.
976 A successful Bind operation is indicated by a BindResponse with a
977 resultCode set to success. Otherwise, an appropriate result code is
978 set in the BindResponse. For BindResponse, the protocolError result
979 code may be used to indicate that the version number supplied by the
980 client is unsupported.
982 If the client receives a BindResponse where the resultCode is set to
983 protocolError, it is to assume that the server does not support this
984 version of LDAP. While the client may be able proceed with another
985 version of this protocol (which may or may not require closing and
986 re-establishing the transport connection), how to proceed with
987 another version of this protocol is beyond the scope of this
988 document. Clients that are unable or unwilling to proceed SHOULD
989 terminate the LDAP session.
991 The serverSaslCreds field is used as part of a SASL-defined bind
992 mechanism to allow the client to authenticate the server to which it
993 is communicating, or to perform "challenge-response" authentication.
994 If the client bound with the simple choice, or the SASL mechanism
995 does not require the server to return information to the client, then
996 this field SHALL NOT be included in the BindResponse.
998 4.3. Unbind Operation
1000 The function of the Unbind operation is to terminate an LDAP session.
1001 The Unbind operation is not the antithesis of the Bind operation as
1002 the name implies. The naming of these operations are historical.
1003 The Unbind operation should be thought of as the "quit" operation.
1010 Sermersheim Standards Track [Page 18]
1012 RFC 4511 LDAPv3 June 2006
1015 The Unbind operation is defined as follows:
1017 UnbindRequest ::= [APPLICATION 2] NULL
1019 The client, upon transmission of the UnbindRequest, and the server,
1020 upon receipt of the UnbindRequest, are to gracefully terminate the
1021 LDAP session as described in Section 5.3. Uncompleted operations are
1022 handled as specified in Section 3.1.
1024 4.4. Unsolicited Notification
1026 An unsolicited notification is an LDAPMessage sent from the server to
1027 the client that is not in response to any LDAPMessage received by the
1028 server. It is used to signal an extraordinary condition in the
1029 server or in the LDAP session between the client and the server. The
1030 notification is of an advisory nature, and the server will not expect
1031 any response to be returned from the client.
1033 The unsolicited notification is structured as an LDAPMessage in which
1034 the messageID is zero and protocolOp is set to the extendedResp
1035 choice using the ExtendedResponse type (See Section 4.12). The
1036 responseName field of the ExtendedResponse always contains an LDAPOID
1037 that is unique for this notification.
1039 One unsolicited notification (Notice of Disconnection) is defined in
1040 this document. The specification of an unsolicited notification
1043 - the OBJECT IDENTIFIER assigned to the notification (to be specified
1044 in the responseName,
1046 - the format of the contents of the responseValue (if any),
1048 - the circumstances which will cause the notification to be sent, and
1050 - the semantics of the message.
1052 4.4.1. Notice of Disconnection
1054 This notification may be used by the server to advise the client that
1055 the server is about to terminate the LDAP session on its own
1056 initiative. This notification is intended to assist clients in
1057 distinguishing between an exceptional server condition and a
1058 transient network failure. Note that this notification is not a
1059 response to an Unbind requested by the client. Uncompleted
1060 operations are handled as specified in Section 3.1.
1066 Sermersheim Standards Track [Page 19]
1068 RFC 4511 LDAPv3 June 2006
1071 The responseName is 1.3.6.1.4.1.1466.20036, the responseValue field
1072 is absent, and the resultCode is used to indicate the reason for the
1073 disconnection. When the strongerAuthRequired resultCode is returned
1074 with this message, it indicates that the server has detected that an
1075 established security association between the client and server has
1076 unexpectedly failed or been compromised.
1078 Upon transmission of the Notice of Disconnection, the server
1079 gracefully terminates the LDAP session as described in Section 5.3.
1081 4.5. Search Operation
1083 The Search operation is used to request a server to return, subject
1084 to access controls and other restrictions, a set of entries matching
1085 a complex search criterion. This can be used to read attributes from
1086 a single entry, from entries immediately subordinate to a particular
1087 entry, or from a whole subtree of entries.
1089 4.5.1. Search Request
1091 The Search request is defined as follows:
1093 SearchRequest ::= [APPLICATION 3] SEQUENCE {
1100 derefAliases ENUMERATED {
1101 neverDerefAliases (0),
1102 derefInSearching (1),
1103 derefFindingBaseObj (2),
1105 sizeLimit INTEGER (0 .. maxInt),
1106 timeLimit INTEGER (0 .. maxInt),
1109 attributes AttributeSelection }
1111 AttributeSelection ::= SEQUENCE OF selector LDAPString
1112 -- The LDAPString is constrained to
1113 -- <attributeSelector> in Section 4.5.1.8
1116 and [0] SET SIZE (1..MAX) OF filter Filter,
1117 or [1] SET SIZE (1..MAX) OF filter Filter,
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1124 RFC 4511 LDAPv3 June 2006
1127 equalityMatch [3] AttributeValueAssertion,
1128 substrings [4] SubstringFilter,
1129 greaterOrEqual [5] AttributeValueAssertion,
1130 lessOrEqual [6] AttributeValueAssertion,
1131 present [7] AttributeDescription,
1132 approxMatch [8] AttributeValueAssertion,
1133 extensibleMatch [9] MatchingRuleAssertion,
1136 SubstringFilter ::= SEQUENCE {
1137 type AttributeDescription,
1138 substrings SEQUENCE SIZE (1..MAX) OF substring CHOICE {
1139 initial [0] AssertionValue, -- can occur at most once
1140 any [1] AssertionValue,
1141 final [2] AssertionValue } -- can occur at most once
1144 MatchingRuleAssertion ::= SEQUENCE {
1145 matchingRule [1] MatchingRuleId OPTIONAL,
1146 type [2] AttributeDescription OPTIONAL,
1147 matchValue [3] AssertionValue,
1148 dnAttributes [4] BOOLEAN DEFAULT FALSE }
1150 Note that an X.500 "list"-like operation can be emulated by the
1151 client requesting a singleLevel Search operation with a filter
1152 checking for the presence of the 'objectClass' attribute, and that an
1153 X.500 "read"-like operation can be emulated by a baseObject Search
1154 operation with the same filter. A server that provides a gateway to
1155 X.500 is not required to use the Read or List operations, although it
1156 may choose to do so, and if it does, it must provide the same
1157 semantics as the X.500 Search operation.
1159 4.5.1.1. SearchRequest.baseObject
1161 The name of the base object entry (or possibly the root) relative to
1162 which the Search is to be performed.
1164 4.5.1.2. SearchRequest.scope
1166 Specifies the scope of the Search to be performed. The semantics (as
1167 described in [X.511]) of the defined values of this field are:
1169 baseObject: The scope is constrained to the entry named by
1172 singleLevel: The scope is constrained to the immediate
1173 subordinates of the entry named by baseObject.
1178 Sermersheim Standards Track [Page 21]
1180 RFC 4511 LDAPv3 June 2006
1183 wholeSubtree: The scope is constrained to the entry named by
1184 baseObject and to all its subordinates.
1186 4.5.1.3. SearchRequest.derefAliases
1188 An indicator as to whether or not alias entries (as defined in
1189 [RFC4512]) are to be dereferenced during stages of the Search
1192 The act of dereferencing an alias includes recursively dereferencing
1193 aliases that refer to aliases.
1195 Servers MUST detect looping while dereferencing aliases in order to
1196 prevent denial-of-service attacks of this nature.
1198 The semantics of the defined values of this field are:
1200 neverDerefAliases: Do not dereference aliases in searching or in
1201 locating the base object of the Search.
1203 derefInSearching: While searching subordinates of the base object,
1204 dereference any alias within the search scope. Dereferenced
1205 objects become the vertices of further search scopes where the
1206 Search operation is also applied. If the search scope is
1207 wholeSubtree, the Search continues in the subtree(s) of any
1208 dereferenced object. If the search scope is singleLevel, the
1209 search is applied to any dereferenced objects and is not applied
1210 to their subordinates. Servers SHOULD eliminate duplicate entries
1211 that arise due to alias dereferencing while searching.
1213 derefFindingBaseObj: Dereference aliases in locating the base
1214 object of the Search, but not when searching subordinates of the
1217 derefAlways: Dereference aliases both in searching and in locating
1218 the base object of the Search.
1220 4.5.1.4. SearchRequest.sizeLimit
1222 A size limit that restricts the maximum number of entries to be
1223 returned as a result of the Search. A value of zero in this field
1224 indicates that no client-requested size limit restrictions are in
1225 effect for the Search. Servers may also enforce a maximum number of
1234 Sermersheim Standards Track [Page 22]
1236 RFC 4511 LDAPv3 June 2006
1239 4.5.1.5. SearchRequest.timeLimit
1241 A time limit that restricts the maximum time (in seconds) allowed for
1242 a Search. A value of zero in this field indicates that no client-
1243 requested time limit restrictions are in effect for the Search.
1244 Servers may also enforce a maximum time limit for the Search.
1246 4.5.1.6. SearchRequest.typesOnly
1248 An indicator as to whether Search results are to contain both
1249 attribute descriptions and values, or just attribute descriptions.
1250 Setting this field to TRUE causes only attribute descriptions (and
1251 not values) to be returned. Setting this field to FALSE causes both
1252 attribute descriptions and values to be returned.
1254 4.5.1.7. SearchRequest.filter
1256 A filter that defines the conditions that must be fulfilled in order
1257 for the Search to match a given entry.
1259 The 'and', 'or', and 'not' choices can be used to form combinations
1260 of filters. At least one filter element MUST be present in an 'and'
1261 or 'or' choice. The others match against individual attribute values
1262 of entries in the scope of the Search. (Implementor's note: the
1263 'not' filter is an example of a tagged choice in an implicitly-tagged
1264 module. In BER this is treated as if the tag were explicit.)
1266 A server MUST evaluate filters according to the three-valued logic of
1267 [X.511] (1993), Clause 7.8.1. In summary, a filter is evaluated to
1268 "TRUE", "FALSE", or "Undefined". If the filter evaluates to TRUE for
1269 a particular entry, then the attributes of that entry are returned as
1270 part of the Search result (subject to any applicable access control
1271 restrictions). If the filter evaluates to FALSE or Undefined, then
1272 the entry is ignored for the Search.
1274 A filter of the "and" choice is TRUE if all the filters in the SET OF
1275 evaluate to TRUE, FALSE if at least one filter is FALSE, and
1276 Undefined otherwise. A filter of the "or" choice is FALSE if all the
1277 filters in the SET OF evaluate to FALSE, TRUE if at least one filter
1278 is TRUE, and Undefined otherwise. A filter of the 'not' choice is
1279 TRUE if the filter being negated is FALSE, FALSE if it is TRUE, and
1280 Undefined if it is Undefined.
1282 A filter item evaluates to Undefined when the server would not be
1283 able to determine whether the assertion value matches an entry.
1290 Sermersheim Standards Track [Page 23]
1292 RFC 4511 LDAPv3 June 2006
1295 - An attribute description in an equalityMatch, substrings,
1296 greaterOrEqual, lessOrEqual, approxMatch, or extensibleMatch filter
1297 is not recognized by the server.
1299 - The attribute type does not define the appropriate matching rule.
1301 - A MatchingRuleId in the extensibleMatch is not recognized by the
1302 server or is not valid for the attribute type.
1304 - The type of filtering requested is not implemented.
1306 - The assertion value is invalid.
1308 For example, if a server did not recognize the attribute type
1309 shoeSize, the filters (shoeSize=*), (shoeSize=12), (shoeSize>=12),
1310 and (shoeSize<=12) would each evaluate to Undefined.
1312 Servers MUST NOT return errors if attribute descriptions or matching
1313 rule ids are not recognized, assertion values are invalid, or the
1314 assertion syntax is not supported. More details of filter processing
1315 are given in Clause 7.8 of [X.511].
1317 4.5.1.7.1. SearchRequest.filter.equalityMatch
1319 The matching rule for an equalityMatch filter is defined by the
1320 EQUALITY matching rule for the attribute type or subtype. The filter
1321 is TRUE when the EQUALITY rule returns TRUE as applied to the
1322 attribute or subtype and the asserted value.
1324 4.5.1.7.2. SearchRequest.filter.substrings
1326 There SHALL be at most one 'initial' and at most one 'final' in the
1327 'substrings' of a SubstringFilter. If 'initial' is present, it SHALL
1328 be the first element of 'substrings'. If 'final' is present, it
1329 SHALL be the last element of 'substrings'.
1331 The matching rule for an AssertionValue in a substrings filter item
1332 is defined by the SUBSTR matching rule for the attribute type or
1333 subtype. The filter is TRUE when the SUBSTR rule returns TRUE as
1334 applied to the attribute or subtype and the asserted value.
1336 Note that the AssertionValue in a substrings filter item conforms to
1337 the assertion syntax of the EQUALITY matching rule for the attribute
1338 type rather than to the assertion syntax of the SUBSTR matching rule
1339 for the attribute type. Conceptually, the entire SubstringFilter is
1340 converted into an assertion value of the substrings matching rule
1341 prior to applying the rule.
1346 Sermersheim Standards Track [Page 24]
1348 RFC 4511 LDAPv3 June 2006
1351 4.5.1.7.3. SearchRequest.filter.greaterOrEqual
1353 The matching rule for a greaterOrEqual filter is defined by the
1354 ORDERING matching rule for the attribute type or subtype. The filter
1355 is TRUE when the ORDERING rule returns FALSE as applied to the
1356 attribute or subtype and the asserted value.
1358 4.5.1.7.4. SearchRequest.filter.lessOrEqual
1360 The matching rules for a lessOrEqual filter are defined by the
1361 ORDERING and EQUALITY matching rules for the attribute type or
1362 subtype. The filter is TRUE when either the ORDERING or EQUALITY
1363 rule returns TRUE as applied to the attribute or subtype and the
1366 4.5.1.7.5. SearchRequest.filter.present
1368 A present filter is TRUE when there is an attribute or subtype of the
1369 specified attribute description present in an entry, FALSE when no
1370 attribute or subtype of the specified attribute description is
1371 present in an entry, and Undefined otherwise.
1373 4.5.1.7.6. SearchRequest.filter.approxMatch
1375 An approxMatch filter is TRUE when there is a value of the attribute
1376 type or subtype for which some locally-defined approximate matching
1377 algorithm (e.g., spelling variations, phonetic match, etc.) returns
1378 TRUE. If a value matches for equality, it also satisfies an
1379 approximate match. If approximate matching is not supported for the
1380 attribute, this filter item should be treated as an equalityMatch.
1382 4.5.1.7.7. SearchRequest.filter.extensibleMatch
1384 The fields of the extensibleMatch filter item are evaluated as
1387 - If the matchingRule field is absent, the type field MUST be
1388 present, and an equality match is performed for that type.
1390 - If the type field is absent and the matchingRule is present, the
1391 matchValue is compared against all attributes in an entry that
1392 support that matchingRule.
1394 - If the type field is present and the matchingRule is present, the
1395 matchValue is compared against the specified attribute type and its
1402 Sermersheim Standards Track [Page 25]
1404 RFC 4511 LDAPv3 June 2006
1407 - If the dnAttributes field is set to TRUE, the match is additionally
1408 applied against all the AttributeValueAssertions in an entry's
1409 distinguished name, and it evaluates to TRUE if there is at least
1410 one attribute or subtype in the distinguished name for which the
1411 filter item evaluates to TRUE. The dnAttributes field is present
1412 to alleviate the need for multiple versions of generic matching
1413 rules (such as word matching), where one applies to entries and
1414 another applies to entries and DN attributes as well.
1416 The matchingRule used for evaluation determines the syntax for the
1417 assertion value. Once the matchingRule and attribute(s) have been
1418 determined, the filter item evaluates to TRUE if it matches at least
1419 one attribute type or subtype in the entry, FALSE if it does not
1420 match any attribute type or subtype in the entry, and Undefined if
1421 the matchingRule is not recognized, the matchingRule is unsuitable
1422 for use with the specified type, or the assertionValue is invalid.
1424 4.5.1.8. SearchRequest.attributes
1426 A selection list of the attributes to be returned from each entry
1427 that matches the search filter. Attributes that are subtypes of
1428 listed attributes are implicitly included. LDAPString values of this
1429 field are constrained to the following Augmented Backus-Naur Form
1432 attributeSelector = attributedescription / selectorspecial
1434 selectorspecial = noattrs / alluserattrs
1436 noattrs = %x31.2E.31 ; "1.1"
1438 alluserattrs = %x2A ; asterisk ("*")
1440 The <attributedescription> production is defined in Section 2.5 of
1443 There are three special cases that may appear in the attributes
1446 1. An empty list with no attributes requests the return of all
1449 2. A list containing "*" (with zero or more attribute
1450 descriptions) requests the return of all user attributes in
1451 addition to other listed (operational) attributes.
1458 Sermersheim Standards Track [Page 26]
1460 RFC 4511 LDAPv3 June 2006
1463 3. A list containing only the OID "1.1" indicates that no
1464 attributes are to be returned. If "1.1" is provided with other
1465 attributeSelector values, the "1.1" attributeSelector is
1466 ignored. This OID was chosen because it does not (and can not)
1467 correspond to any attribute in use.
1469 Client implementors should note that even if all user attributes are
1470 requested, some attributes and/or attribute values of the entry may
1471 not be included in Search results due to access controls or other
1472 restrictions. Furthermore, servers will not return operational
1473 attributes, such as objectClasses or attributeTypes, unless they are
1474 listed by name. Operational attributes are described in [RFC4512].
1476 Attributes are returned at most once in an entry. If an attribute
1477 description is named more than once in the list, the subsequent names
1478 are ignored. If an attribute description in the list is not
1479 recognized, it is ignored by the server.
1481 4.5.2. Search Result
1483 The results of the Search operation are returned as zero or more
1484 SearchResultEntry and/or SearchResultReference messages, followed by
1485 a single SearchResultDone message.
1487 SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
1489 attributes PartialAttributeList }
1491 PartialAttributeList ::= SEQUENCE OF
1492 partialAttribute PartialAttribute
1494 SearchResultReference ::= [APPLICATION 19] SEQUENCE
1495 SIZE (1..MAX) OF uri URI
1497 SearchResultDone ::= [APPLICATION 5] LDAPResult
1499 Each SearchResultEntry represents an entry found during the Search.
1500 Each SearchResultReference represents an area not yet explored during
1501 the Search. The SearchResultEntry and SearchResultReference messages
1502 may come in any order. Following all the SearchResultReference and
1503 SearchResultEntry responses, the server returns a SearchResultDone
1504 response, which contains an indication of success or details any
1505 errors that have occurred.
1507 Each entry returned in a SearchResultEntry will contain all
1508 appropriate attributes as specified in the attributes field of the
1509 Search Request, subject to access control and other administrative
1510 policy. Note that the PartialAttributeList may hold zero elements.
1514 Sermersheim Standards Track [Page 27]
1516 RFC 4511 LDAPv3 June 2006
1519 This may happen when none of the attributes of an entry were
1520 requested or could be returned. Note also that the partialAttribute
1521 vals set may hold zero elements. This may happen when typesOnly is
1522 requested, access controls prevent the return of values, or other
1525 Some attributes may be constructed by the server and appear in a
1526 SearchResultEntry attribute list, although they are not stored
1527 attributes of an entry. Clients SHOULD NOT assume that all
1528 attributes can be modified, even if this is permitted by access
1531 If the server's schema defines short names [RFC4512] for an attribute
1532 type, then the server SHOULD use one of those names in attribute
1533 descriptions for that attribute type (in preference to using the
1534 <numericoid> [RFC4512] format of the attribute type's object
1535 identifier). The server SHOULD NOT use the short name if that name
1536 is known by the server to be ambiguous, or if it is otherwise likely
1537 to cause interoperability problems.
1539 4.5.3. Continuation References in the Search Result
1541 If the server was able to locate the entry referred to by the
1542 baseObject but was unable or unwilling to search one or more non-
1543 local entries, the server may return one or more
1544 SearchResultReference messages, each containing a reference to
1545 another set of servers for continuing the operation. A server MUST
1546 NOT return any SearchResultReference messages if it has not located
1547 the baseObject and thus has not searched any entries. In this case,
1548 it would return a SearchResultDone containing either a referral or
1549 noSuchObject result code (depending on the server's knowledge of the
1550 entry named in the baseObject).
1552 If a server holds a copy or partial copy of the subordinate naming
1553 context (Section 5 of [RFC4512]), it may use the search filter to
1554 determine whether or not to return a SearchResultReference response.
1555 Otherwise, SearchResultReference responses are always returned when
1558 The SearchResultReference is of the same data type as the Referral.
1560 If the client wishes to progress the Search, it issues a new Search
1561 operation for each SearchResultReference that is returned. If
1562 multiple URIs are present, the client assumes that any supported URI
1563 may be used to progress the operation.
1570 Sermersheim Standards Track [Page 28]
1572 RFC 4511 LDAPv3 June 2006
1575 Clients that follow search continuation references MUST ensure that
1576 they do not loop between servers. They MUST NOT repeatedly contact
1577 the same server for the same request with the same parameters. Some
1578 clients use a counter that is incremented each time search result
1579 reference handling occurs for an operation, and these kinds of
1580 clients MUST be able to handle at least ten nested referrals while
1581 progressing the operation.
1583 Note that the Abandon operation described in Section 4.11 applies
1584 only to a particular operation sent at the LDAP message layer between
1585 a client and server. The client must individually abandon subsequent
1586 Search operations it wishes to.
1588 A URI for a server implementing LDAP and accessible via TCP/IP (v4 or
1589 v6) [RFC793][RFC791] is written as an LDAP URL according to
1592 SearchResultReference values that are LDAP URLs follow these rules:
1594 - The <dn> part of the LDAP URL MUST be present, with the new target
1595 object name. The client uses this name when following the
1598 - Some servers (e.g., participating in distributed indexing) may
1599 provide a different filter in the LDAP URL.
1601 - If the <filter> part of the LDAP URL is present, the client uses
1602 this filter in its next request to progress this Search, and if it
1603 is not present the client uses the same filter as it used for that
1606 - If the originating search scope was singleLevel, the <scope> part
1607 of the LDAP URL will be "base".
1609 - It is RECOMMENDED that the <scope> part be present to avoid
1610 ambiguity. In the absence of a <scope> part, the scope of the
1611 original Search request is assumed.
1613 - Other aspects of the new Search request may be the same as or
1614 different from the Search request that generated the
1615 SearchResultReference.
1617 - The name of an unexplored subtree in a SearchResultReference need
1618 not be subordinate to the base object.
1620 Other kinds of URIs may be returned. The syntax and semantics of
1621 such URIs is left to future specifications. Clients may ignore URIs
1622 that they do not support.
1626 Sermersheim Standards Track [Page 29]
1628 RFC 4511 LDAPv3 June 2006
1631 UTF-8-encoded characters appearing in the string representation of a
1632 DN, search filter, or other fields of the referral value may not be
1633 legal for URIs (e.g., spaces) and MUST be escaped using the % method
1638 For example, suppose the contacted server (hosta) holds the entry
1639 <DC=Example,DC=NET> and the entry <CN=Manager,DC=Example,DC=NET>. It
1640 knows that both LDAP servers (hostb) and (hostc) hold
1641 <OU=People,DC=Example,DC=NET> (one is the master and the other server
1642 a shadow), and that LDAP-capable server (hostd) holds the subtree
1643 <OU=Roles,DC=Example,DC=NET>. If a wholeSubtree Search of
1644 <DC=Example,DC=NET> is requested to the contacted server, it may
1645 return the following:
1647 SearchResultEntry for DC=Example,DC=NET
1648 SearchResultEntry for CN=Manager,DC=Example,DC=NET
1649 SearchResultReference {
1650 ldap://hostb/OU=People,DC=Example,DC=NET??sub
1651 ldap://hostc/OU=People,DC=Example,DC=NET??sub }
1652 SearchResultReference {
1653 ldap://hostd/OU=Roles,DC=Example,DC=NET??sub }
1654 SearchResultDone (success)
1656 Client implementors should note that when following a
1657 SearchResultReference, additional SearchResultReference may be
1658 generated. Continuing the example, if the client contacted the
1659 server (hostb) and issued the Search request for the subtree
1660 <OU=People,DC=Example,DC=NET>, the server might respond as follows:
1662 SearchResultEntry for OU=People,DC=Example,DC=NET
1663 SearchResultReference {
1664 ldap://hoste/OU=Managers,OU=People,DC=Example,DC=NET??sub }
1665 SearchResultReference {
1666 ldap://hostf/OU=Consultants,OU=People,DC=Example,DC=NET??sub }
1667 SearchResultDone (success)
1669 Similarly, if a singleLevel Search of <DC=Example,DC=NET> is
1670 requested to the contacted server, it may return the following:
1672 SearchResultEntry for CN=Manager,DC=Example,DC=NET
1673 SearchResultReference {
1674 ldap://hostb/OU=People,DC=Example,DC=NET??base
1675 ldap://hostc/OU=People,DC=Example,DC=NET??base }
1676 SearchResultReference {
1677 ldap://hostd/OU=Roles,DC=Example,DC=NET??base }
1678 SearchResultDone (success)
1682 Sermersheim Standards Track [Page 30]
1684 RFC 4511 LDAPv3 June 2006
1687 If the contacted server does not hold the base object for the Search,
1688 but has knowledge of its possible location, then it may return a
1689 referral to the client. In this case, if the client requests a
1690 subtree Search of <DC=Example,DC=ORG> to hosta, the server returns a
1691 SearchResultDone containing a referral.
1693 SearchResultDone (referral) {
1694 ldap://hostg/DC=Example,DC=ORG??sub }
1696 4.6. Modify Operation
1698 The Modify operation allows a client to request that a modification
1699 of an entry be performed on its behalf by a server. The Modify
1700 Request is defined as follows:
1702 ModifyRequest ::= [APPLICATION 6] SEQUENCE {
1704 changes SEQUENCE OF change SEQUENCE {
1705 operation ENUMERATED {
1710 modification PartialAttribute } }
1712 Fields of the Modify Request are:
1714 - object: The value of this field contains the name of the entry to
1715 be modified. The server SHALL NOT perform any alias dereferencing
1716 in determining the object to be modified.
1718 - changes: A list of modifications to be performed on the entry. The
1719 entire list of modifications MUST be performed in the order they
1720 are listed as a single atomic operation. While individual
1721 modifications may violate certain aspects of the directory schema
1722 (such as the object class definition and Directory Information Tree
1723 (DIT) content rule), the resulting entry after the entire list of
1724 modifications is performed MUST conform to the requirements of the
1725 directory model and controlling schema [RFC4512].
1727 - operation: Used to specify the type of modification being
1728 performed. Each operation type acts on the following
1729 modification. The values of this field have the following
1730 semantics, respectively:
1732 add: add values listed to the modification attribute,
1733 creating the attribute if necessary.
1738 Sermersheim Standards Track [Page 31]
1740 RFC 4511 LDAPv3 June 2006
1743 delete: delete values listed from the modification attribute.
1744 If no values are listed, or if all current values of the
1745 attribute are listed, the entire attribute is removed.
1747 replace: replace all existing values of the modification
1748 attribute with the new values listed, creating the attribute
1749 if it did not already exist. A replace with no value will
1750 delete the entire attribute if it exists, and it is ignored
1751 if the attribute does not exist.
1753 - modification: A PartialAttribute (which may have an empty SET
1754 of vals) used to hold the attribute type or attribute type and
1755 values being modified.
1757 Upon receipt of a Modify Request, the server attempts to perform the
1758 necessary modifications to the DIT and returns the result in a Modify
1759 Response, defined as follows:
1761 ModifyResponse ::= [APPLICATION 7] LDAPResult
1763 The server will return to the client a single Modify Response
1764 indicating either the successful completion of the DIT modification,
1765 or the reason that the modification failed. Due to the requirement
1766 for atomicity in applying the list of modifications in the Modify
1767 Request, the client may expect that no modifications of the DIT have
1768 been performed if the Modify Response received indicates any sort of
1769 error, and that all requested modifications have been performed if
1770 the Modify Response indicates successful completion of the Modify
1771 operation. Whether or not the modification was applied cannot be
1772 determined by the client if the Modify Response was not received
1773 (e.g., the LDAP session was terminated or the Modify operation was
1776 Servers MUST ensure that entries conform to user and system schema
1777 rules or other data model constraints. The Modify operation cannot
1778 be used to remove from an entry any of its distinguished values,
1779 i.e., those values which form the entry's relative distinguished
1780 name. An attempt to do so will result in the server returning the
1781 notAllowedOnRDN result code. The Modify DN operation described in
1782 Section 4.9 is used to rename an entry.
1784 For attribute types that specify no equality matching, the rules in
1785 Section 2.5.1 of [RFC4512] are followed.
1787 Note that due to the simplifications made in LDAP, there is not a
1788 direct mapping of the changes in an LDAP ModifyRequest onto the
1789 changes of a DAP ModifyEntry operation, and different implementations
1794 Sermersheim Standards Track [Page 32]
1796 RFC 4511 LDAPv3 June 2006
1799 of LDAP-DAP gateways may use different means of representing the
1800 change. If successful, the final effect of the operations on the
1801 entry MUST be identical.
1805 The Add operation allows a client to request the addition of an entry
1806 into the Directory. The Add Request is defined as follows:
1808 AddRequest ::= [APPLICATION 8] SEQUENCE {
1810 attributes AttributeList }
1812 AttributeList ::= SEQUENCE OF attribute Attribute
1814 Fields of the Add Request are:
1816 - entry: the name of the entry to be added. The server SHALL NOT
1817 dereference any aliases in locating the entry to be added.
1819 - attributes: the list of attributes that, along with those from the
1820 RDN, make up the content of the entry being added. Clients MAY or
1821 MAY NOT include the RDN attribute(s) in this list. Clients MUST
1822 NOT supply NO-USER-MODIFICATION attributes such as the
1823 createTimestamp or creatorsName attributes, since the server
1824 maintains these automatically.
1826 Servers MUST ensure that entries conform to user and system schema
1827 rules or other data model constraints. For attribute types that
1828 specify no equality matching, the rules in Section 2.5.1 of [RFC4512]
1829 are followed (this applies to the naming attribute in addition to any
1830 multi-valued attributes being added).
1832 The entry named in the entry field of the AddRequest MUST NOT exist
1833 for the AddRequest to succeed. The immediate superior (parent) of an
1834 object or alias entry to be added MUST exist. For example, if the
1835 client attempted to add <CN=JS,DC=Example,DC=NET>, the
1836 <DC=Example,DC=NET> entry did not exist, and the <DC=NET> entry did
1837 exist, then the server would return the noSuchObject result code with
1838 the matchedDN field containing <DC=NET>.
1840 Upon receipt of an Add Request, a server will attempt to add the
1841 requested entry. The result of the Add attempt will be returned to
1842 the client in the Add Response, defined as follows:
1844 AddResponse ::= [APPLICATION 9] LDAPResult
1850 Sermersheim Standards Track [Page 33]
1852 RFC 4511 LDAPv3 June 2006
1855 A response of success indicates that the new entry has been added to
1858 4.8. Delete Operation
1860 The Delete operation allows a client to request the removal of an
1861 entry from the Directory. The Delete Request is defined as follows:
1863 DelRequest ::= [APPLICATION 10] LDAPDN
1865 The Delete Request consists of the name of the entry to be deleted.
1866 The server SHALL NOT dereference aliases while resolving the name of
1867 the target entry to be removed.
1869 Only leaf entries (those with no subordinate entries) can be deleted
1870 with this operation.
1872 Upon receipt of a Delete Request, a server will attempt to perform
1873 the entry removal requested and return the result in the Delete
1874 Response defined as follows:
1876 DelResponse ::= [APPLICATION 11] LDAPResult
1878 4.9. Modify DN Operation
1880 The Modify DN operation allows a client to change the Relative
1881 Distinguished Name (RDN) of an entry in the Directory and/or to move
1882 a subtree of entries to a new location in the Directory. The Modify
1883 DN Request is defined as follows:
1885 ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
1887 newrdn RelativeLDAPDN,
1888 deleteoldrdn BOOLEAN,
1889 newSuperior [0] LDAPDN OPTIONAL }
1891 Fields of the Modify DN Request are:
1893 - entry: the name of the entry to be changed. This entry may or may
1894 not have subordinate entries.
1896 - newrdn: the new RDN of the entry. The value of the old RDN is
1897 supplied when moving the entry to a new superior without changing
1898 its RDN. Attribute values of the new RDN not matching any
1899 attribute value of the entry are added to the entry, and an
1900 appropriate error is returned if this fails.
1906 Sermersheim Standards Track [Page 34]
1908 RFC 4511 LDAPv3 June 2006
1911 - deleteoldrdn: a boolean field that controls whether the old RDN
1912 attribute values are to be retained as attributes of the entry or
1913 deleted from the entry.
1915 - newSuperior: if present, this is the name of an existing object
1916 entry that becomes the immediate superior (parent) of the
1919 The server SHALL NOT dereference any aliases in locating the objects
1920 named in entry or newSuperior.
1922 Upon receipt of a ModifyDNRequest, a server will attempt to perform
1923 the name change and return the result in the Modify DN Response,
1926 ModifyDNResponse ::= [APPLICATION 13] LDAPResult
1928 For example, if the entry named in the entry field was <cn=John
1929 Smith,c=US>, the newrdn field was <cn=John Cougar Smith>, and the
1930 newSuperior field was absent, then this operation would attempt to
1931 rename the entry as <cn=John Cougar Smith,c=US>. If there was
1932 already an entry with that name, the operation would fail with the
1933 entryAlreadyExists result code.
1935 Servers MUST ensure that entries conform to user and system schema
1936 rules or other data model constraints. For attribute types that
1937 specify no equality matching, the rules in Section 2.5.1 of [RFC4512]
1938 are followed (this pertains to newrdn and deleteoldrdn).
1940 The object named in newSuperior MUST exist. For example, if the
1941 client attempted to add <CN=JS,DC=Example,DC=NET>, the
1942 <DC=Example,DC=NET> entry did not exist, and the <DC=NET> entry did
1943 exist, then the server would return the noSuchObject result code with
1944 the matchedDN field containing <DC=NET>.
1946 If the deleteoldrdn field is TRUE, the attribute values forming the
1947 old RDN (but not the new RDN) are deleted from the entry. If the
1948 deleteoldrdn field is FALSE, the attribute values forming the old RDN
1949 will be retained as non-distinguished attribute values of the entry.
1951 Note that X.500 restricts the ModifyDN operation to affect only
1952 entries that are contained within a single server. If the LDAP
1953 server is mapped onto DAP, then this restriction will apply, and the
1954 affectsMultipleDSAs result code will be returned if this error
1955 occurred. In general, clients MUST NOT expect to be able to perform
1956 arbitrary movements of entries and subtrees between servers or
1957 between naming contexts.
1962 Sermersheim Standards Track [Page 35]
1964 RFC 4511 LDAPv3 June 2006
1967 4.10. Compare Operation
1969 The Compare operation allows a client to compare an assertion value
1970 with the values of a particular attribute in a particular entry in
1971 the Directory. The Compare Request is defined as follows:
1973 CompareRequest ::= [APPLICATION 14] SEQUENCE {
1975 ava AttributeValueAssertion }
1977 Fields of the Compare Request are:
1979 - entry: the name of the entry to be compared. The server SHALL NOT
1980 dereference any aliases in locating the entry to be compared.
1982 - ava: holds the attribute value assertion to be compared.
1984 Upon receipt of a Compare Request, a server will attempt to perform
1985 the requested comparison and return the result in the Compare
1986 Response, defined as follows:
1988 CompareResponse ::= [APPLICATION 15] LDAPResult
1990 The resultCode is set to compareTrue, compareFalse, or an appropriate
1991 error. compareTrue indicates that the assertion value in the ava
1992 field matches a value of the attribute or subtype according to the
1993 attribute's EQUALITY matching rule. compareFalse indicates that the
1994 assertion value in the ava field and the values of the attribute or
1995 subtype did not match. Other result codes indicate either that the
1996 result of the comparison was Undefined (Section 4.5.1.7), or that
1997 some error occurred.
1999 Note that some directory systems may establish access controls that
2000 permit the values of certain attributes (such as userPassword) to be
2001 compared but not interrogated by other means.
2003 4.11. Abandon Operation
2005 The function of the Abandon operation is to allow a client to request
2006 that the server abandon an uncompleted operation. The Abandon
2007 Request is defined as follows:
2009 AbandonRequest ::= [APPLICATION 16] MessageID
2011 The MessageID is that of an operation that was requested earlier at
2012 this LDAP message layer. The Abandon request itself has its own
2013 MessageID. This is distinct from the MessageID of the earlier
2014 operation being abandoned.
2018 Sermersheim Standards Track [Page 36]
2020 RFC 4511 LDAPv3 June 2006
2023 There is no response defined in the Abandon operation. Upon receipt
2024 of an AbandonRequest, the server MAY abandon the operation identified
2025 by the MessageID. Since the client cannot tell the difference
2026 between a successfully abandoned operation and an uncompleted
2027 operation, the application of the Abandon operation is limited to
2028 uses where the client does not require an indication of its outcome.
2030 Abandon, Bind, Unbind, and StartTLS operations cannot be abandoned.
2032 In the event that a server receives an Abandon Request on a Search
2033 operation in the midst of transmitting responses to the Search, that
2034 server MUST cease transmitting entry responses to the abandoned
2035 request immediately, and it MUST NOT send the SearchResultDone. Of
2036 course, the server MUST ensure that only properly encoded LDAPMessage
2037 PDUs are transmitted.
2039 The ability to abandon other (particularly update) operations is at
2040 the discretion of the server.
2042 Clients should not send Abandon requests for the same operation
2043 multiple times, and they MUST also be prepared to receive results
2044 from operations they have abandoned (since these might have been in
2045 transit when the Abandon was requested or might not be able to be
2048 Servers MUST discard Abandon requests for messageIDs they do not
2049 recognize, for operations that cannot be abandoned, and for
2050 operations that have already been abandoned.
2052 4.12. Extended Operation
2054 The Extended operation allows additional operations to be defined for
2055 services not already available in the protocol; for example, to Add
2056 operations to install transport layer security (see Section 4.14).
2058 The Extended operation allows clients to make requests and receive
2059 responses with predefined syntaxes and semantics. These may be
2060 defined in RFCs or be private to particular implementations.
2062 Each Extended operation consists of an Extended request and an
2065 ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
2066 requestName [0] LDAPOID,
2067 requestValue [1] OCTET STRING OPTIONAL }
2074 Sermersheim Standards Track [Page 37]
2076 RFC 4511 LDAPv3 June 2006
2079 The requestName is a dotted-decimal representation of the unique
2080 OBJECT IDENTIFIER corresponding to the request. The requestValue is
2081 information in a form defined by that request, encapsulated inside an
2084 The server will respond to this with an LDAPMessage containing an
2087 ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
2088 COMPONENTS OF LDAPResult,
2089 responseName [10] LDAPOID OPTIONAL,
2090 responseValue [11] OCTET STRING OPTIONAL }
2092 The responseName field, when present, contains an LDAPOID that is
2093 unique for this extended operation or response. This field is
2094 optional (even when the extension specification defines an LDAPOID
2095 for use in this field). The field will be absent whenever the server
2096 is unable or unwilling to determine the appropriate LDAPOID to
2097 return, for instance, when the requestName cannot be parsed or its
2098 value is not recognized.
2100 Where the requestName is not recognized, the server returns
2101 protocolError. (The server may return protocolError in other cases.)
2103 The requestValue and responseValue fields contain information
2104 associated with the operation. The format of these fields is defined
2105 by the specification of the Extended operation. Implementations MUST
2106 be prepared to handle arbitrary contents of these fields, including
2107 zero bytes. Values that are defined in terms of ASN.1 and BER-
2108 encoded according to Section 5.1 also follow the extensibility rules
2111 Servers list the requestName of Extended Requests they recognize in
2112 the 'supportedExtension' attribute in the root DSE (Section 5.1 of
2115 Extended operations may be specified in other documents. The
2116 specification of an Extended operation consists of:
2118 - the OBJECT IDENTIFIER assigned to the requestName,
2120 - the OBJECT IDENTIFIER (if any) assigned to the responseName (note
2121 that the same OBJECT IDENTIFIER may be used for both the
2122 requestName and responseName),
2130 Sermersheim Standards Track [Page 38]
2132 RFC 4511 LDAPv3 June 2006
2135 - the format of the contents of the requestValue and responseValue
2138 - the semantics of the operation.
2140 4.13. IntermediateResponse Message
2142 While the Search operation provides a mechanism to return multiple
2143 response messages for a single Search request, other operations, by
2144 nature, do not provide for multiple response messages.
2146 The IntermediateResponse message provides a general mechanism for
2147 defining single-request/multiple-response operations in LDAP. This
2148 message is intended to be used in conjunction with the Extended
2149 operation to define new single-request/multiple-response operations
2150 or in conjunction with a control when extending existing LDAP
2151 operations in a way that requires them to return Intermediate
2152 response information.
2154 It is intended that the definitions and descriptions of Extended
2155 operations and controls that make use of the IntermediateResponse
2156 message will define the circumstances when an IntermediateResponse
2157 message can be sent by a server and the associated meaning of an
2158 IntermediateResponse message sent in a particular circumstance.
2160 IntermediateResponse ::= [APPLICATION 25] SEQUENCE {
2161 responseName [0] LDAPOID OPTIONAL,
2162 responseValue [1] OCTET STRING OPTIONAL }
2164 IntermediateResponse messages SHALL NOT be returned to the client
2165 unless the client issues a request that specifically solicits their
2166 return. This document defines two forms of solicitation: Extended
2167 operation and request control. IntermediateResponse messages are
2168 specified in documents describing the manner in which they are
2169 solicited (i.e., in the Extended operation or request control
2170 specification that uses them). These specifications include:
2172 - the OBJECT IDENTIFIER (if any) assigned to the responseName,
2174 - the format of the contents of the responseValue (if any), and
2176 - the semantics associated with the IntermediateResponse message.
2178 Extensions that allow the return of multiple types of
2179 IntermediateResponse messages SHALL identify those types using unique
2180 responseName values (note that one of these may specify no value).
2186 Sermersheim Standards Track [Page 39]
2188 RFC 4511 LDAPv3 June 2006
2191 Sections 4.13.1 and 4.13.2 describe additional requirements on the
2192 inclusion of responseName and responseValue in IntermediateResponse
2195 4.13.1. Usage with LDAP ExtendedRequest and ExtendedResponse
2197 A single-request/multiple-response operation may be defined using a
2198 single ExtendedRequest message to solicit zero or more
2199 IntermediateResponse messages of one or more kinds, followed by an
2200 ExtendedResponse message.
2202 4.13.2. Usage with LDAP Request Controls
2204 A control's semantics may include the return of zero or more
2205 IntermediateResponse messages prior to returning the final result
2206 code for the operation. One or more kinds of IntermediateResponse
2207 messages may be sent in response to a request control.
2209 All IntermediateResponse messages associated with request controls
2210 SHALL include a responseName. This requirement ensures that the
2211 client can correctly identify the source of IntermediateResponse
2214 - two or more controls using IntermediateResponse messages are
2215 included in a request for any LDAP operation or
2217 - one or more controls using IntermediateResponse messages are
2218 included in a request with an LDAP Extended operation that uses
2219 IntermediateResponse messages.
2221 4.14. StartTLS Operation
2223 The Start Transport Layer Security (StartTLS) operation's purpose is
2224 to initiate installation of a TLS layer. The StartTLS operation is
2225 defined using the Extended operation mechanism described in Section
2228 4.14.1. StartTLS Request
2230 A client requests TLS establishment by transmitting a StartTLS
2231 request message to the server. The StartTLS request is defined in
2232 terms of an ExtendedRequest. The requestName is
2233 "1.3.6.1.4.1.1466.20037", and the requestValue field is always
2242 Sermersheim Standards Track [Page 40]
2244 RFC 4511 LDAPv3 June 2006
2247 The client MUST NOT send any LDAP PDUs at this LDAP message layer
2248 following this request until it receives a StartTLS Extended response
2249 and, in the case of a successful response, completes TLS
2252 Detected sequencing problems (particularly those detailed in Section
2253 3.1.1 of [RFC4513]) result in the resultCode being set to
2256 If the server does not support TLS (whether by design or by current
2257 configuration), it returns with the resultCode set to protocolError
2258 as described in Section 4.12.
2260 4.14.2. StartTLS Response
2262 When a StartTLS request is received, servers supporting the operation
2263 MUST return a StartTLS response message to the requestor. The
2264 responseName is "1.3.6.1.4.1.1466.20037" when provided (see Section
2265 4.12). The responseValue is always absent.
2267 If the server is willing and able to negotiate TLS, it returns the
2268 StartTLS response with the resultCode set to success. Upon client
2269 receipt of a successful StartTLS response, protocol peers may
2270 commence with TLS negotiation as discussed in Section 3 of [RFC4513].
2272 If the server is otherwise unwilling or unable to perform this
2273 operation, the server is to return an appropriate result code
2274 indicating the nature of the problem. For example, if the TLS
2275 subsystem is not presently available, the server may indicate this by
2276 returning with the resultCode set to unavailable. In cases where a
2277 non-success result code is returned, the LDAP session is left without
2280 4.14.3. Removal of the TLS Layer
2282 Either the client or server MAY remove the TLS layer and leave the
2283 LDAP message layer intact by sending and receiving a TLS closure
2286 The initiating protocol peer sends the TLS closure alert and MUST
2287 wait until it receives a TLS closure alert from the other peer before
2288 sending further LDAP PDUs.
2290 When a protocol peer receives the initial TLS closure alert, it may
2291 choose to allow the LDAP message layer to remain intact. In this
2292 case, it MUST immediately transmit a TLS closure alert. Following
2293 this, it MAY send and receive LDAP PDUs.
2298 Sermersheim Standards Track [Page 41]
2300 RFC 4511 LDAPv3 June 2006
2303 Protocol peers MAY terminate the LDAP session after sending or
2304 receiving a TLS closure alert.
2306 5. Protocol Encoding, Connection, and Transfer
2308 This protocol is designed to run over connection-oriented, reliable
2309 transports, where the data stream is divided into octets (8-bit
2310 units), with each octet and each bit being significant.
2312 One underlying service, LDAP over TCP, is defined in Section 5.2.
2313 This service is generally applicable to applications providing or
2314 consuming X.500-based directory services on the Internet. This
2315 specification was generally written with the TCP mapping in mind.
2316 Specifications detailing other mappings may encounter various
2319 Implementations of LDAP over TCP MUST implement the mapping as
2320 described in Section 5.2.
2322 This table illustrates the relationship among the different layers
2323 involved in an exchange between two protocol peers:
2325 +----------------------+
2326 | LDAP message layer |
2327 +----------------------+ > LDAP PDUs
2328 +----------------------+ < data
2330 +----------------------+ > SASL-protected data
2331 +----------------------+ < data
2333 Application +----------------------+ > TLS-protected data
2334 ------------+----------------------+ < data
2335 Transport | transport connection |
2336 +----------------------+
2338 5.1. Protocol Encoding
2340 The protocol elements of LDAP SHALL be encoded for exchange using the
2341 Basic Encoding Rules [BER] of [ASN.1] with the following
2344 - Only the definite form of length encoding is used.
2346 - OCTET STRING values are encoded in the primitive form only.
2348 - If the value of a BOOLEAN type is true, the encoding of the value
2349 octet is set to hex "FF".
2354 Sermersheim Standards Track [Page 42]
2356 RFC 4511 LDAPv3 June 2006
2359 - If a value of a type is its default value, it is absent. Only some
2360 BOOLEAN and INTEGER types have default values in this protocol
2363 These restrictions are meant to ease the overhead of encoding and
2364 decoding certain elements in BER.
2366 These restrictions do not apply to ASN.1 types encapsulated inside of
2367 OCTET STRING values, such as attribute values, unless otherwise
2370 5.2. Transmission Control Protocol (TCP)
2372 The encoded LDAPMessage PDUs are mapped directly onto the TCP
2373 [RFC793] bytestream using the BER-based encoding described in Section
2374 5.1. It is recommended that server implementations running over the
2375 TCP provide a protocol listener on the Internet Assigned Numbers
2376 Authority (IANA)-assigned LDAP port, 389 [PortReg]. Servers may
2377 instead provide a listener on a different port number. Clients MUST
2378 support contacting servers on any valid TCP port.
2380 5.3. Termination of the LDAP session
2382 Termination of the LDAP session is typically initiated by the client
2383 sending an UnbindRequest (Section 4.3), or by the server sending a
2384 Notice of Disconnection (Section 4.4.1). In these cases, each
2385 protocol peer gracefully terminates the LDAP session by ceasing
2386 exchanges at the LDAP message layer, tearing down any SASL layer,
2387 tearing down any TLS layer, and closing the transport connection.
2389 A protocol peer may determine that the continuation of any
2390 communication would be pernicious, and in this case, it may abruptly
2391 terminate the session by ceasing communication and closing the
2392 transport connection.
2394 In either case, when the LDAP session is terminated, uncompleted
2395 operations are handled as specified in Section 3.1.
2397 6. Security Considerations
2399 This version of the protocol provides facilities for simple
2400 authentication using a cleartext password, as well as any SASL
2401 [RFC4422] mechanism. Installing SASL and/or TLS layers can provide
2402 integrity and other data security services.
2404 It is also permitted that the server can return its credentials to
2405 the client, if it chooses to do so.
2410 Sermersheim Standards Track [Page 43]
2412 RFC 4511 LDAPv3 June 2006
2415 Use of cleartext password is strongly discouraged where the
2416 underlying transport service cannot guarantee confidentiality and may
2417 result in disclosure of the password to unauthorized parties.
2419 Servers are encouraged to prevent directory modifications by clients
2420 that have authenticated anonymously [RFC4513].
2422 Security considerations for authentication methods, SASL mechanisms,
2423 and TLS are described in [RFC4513].
2425 Note that SASL authentication exchanges do not provide data
2426 confidentiality or integrity protection for the version or name
2427 fields of the BindRequest or the resultCode, diagnosticMessage, or
2428 referral fields of the BindResponse, nor for any information
2429 contained in controls attached to Bind requests or responses. Thus,
2430 information contained in these fields SHOULD NOT be relied on unless
2431 it is otherwise protected (such as by establishing protections at the
2434 Implementors should note that various security factors (including
2435 authentication and authorization information and data security
2436 services) may change during the course of the LDAP session or even
2437 during the performance of a particular operation. For instance,
2438 credentials could expire, authorization identities or access controls
2439 could change, or the underlying security layer(s) could be replaced
2440 or terminated. Implementations should be robust in the handling of
2441 changing security factors.
2443 In some cases, it may be appropriate to continue the operation even
2444 in light of security factor changes. For instance, it may be
2445 appropriate to continue an Abandon operation regardless of the
2446 change, or to continue an operation when the change upgraded (or
2447 maintained) the security factor. In other cases, it may be
2448 appropriate to fail or alter the processing of the operation. For
2449 instance, if confidential protections were removed, it would be
2450 appropriate either to fail a request to return sensitive data or,
2451 minimally, to exclude the return of sensitive data.
2453 Implementations that cache attributes and entries obtained via LDAP
2454 MUST ensure that access controls are maintained if that information
2455 is to be provided to multiple clients, since servers may have access
2456 control policies that prevent the return of entries or attributes in
2457 Search results except to particular authenticated clients. For
2458 example, caches could serve result information only to the client
2459 whose request caused it to be in the cache.
2466 Sermersheim Standards Track [Page 44]
2468 RFC 4511 LDAPv3 June 2006
2471 Servers may return referrals or Search result references that
2472 redirect clients to peer servers. It is possible for a rogue
2473 application to inject such referrals into the data stream in an
2474 attempt to redirect a client to a rogue server. Clients are advised
2475 to be aware of this and possibly reject referrals when
2476 confidentiality measures are not in place. Clients are advised to
2477 reject referrals from the StartTLS operation.
2479 The matchedDN and diagnosticMessage fields, as well as some
2480 resultCode values (e.g., attributeOrValueExists and
2481 entryAlreadyExists), could disclose the presence or absence of
2482 specific data in the directory that is subject to access and other
2483 administrative controls. Server implementations should restrict
2484 access to protected information equally under both normal and error
2487 Protocol peers MUST be prepared to handle invalid and arbitrary-
2488 length protocol encodings. Invalid protocol encodings include: BER
2489 encoding exceptions, format string and UTF-8 encoding exceptions,
2490 overflow exceptions, integer value exceptions, and binary mode on/off
2491 flag exceptions. The LDAPv3 PROTOS [PROTOS-LDAP] test suite provides
2492 excellent examples of these exceptions and test cases used to
2495 In the event that a protocol peer senses an attack that in its nature
2496 could cause damage due to further communication at any layer in the
2497 LDAP session, the protocol peer should abruptly terminate the LDAP
2498 session as described in Section 5.3.
2502 This document is based on RFC 2251 by Mark Wahl, Tim Howes, and Steve
2503 Kille. RFC 2251 was a product of the IETF ASID Working Group.
2505 It is also based on RFC 2830 by Jeff Hodges, RL "Bob" Morgan, and
2506 Mark Wahl. RFC 2830 was a product of the IETF LDAPEXT Working Group.
2508 It is also based on RFC 3771 by Roger Harrison and Kurt Zeilenga.
2509 RFC 3771 was an individual submission to the IETF.
2511 This document is a product of the IETF LDAPBIS Working Group.
2512 Significant contributors of technical review and content include Kurt
2513 Zeilenga, Steven Legg, and Hallvard Furuseth.
2522 Sermersheim Standards Track [Page 45]
2524 RFC 4511 LDAPv3 June 2006
2527 8. Normative References
2529 [ASN.1] ITU-T Recommendation X.680 (07/2002) | ISO/IEC 8824-
2530 1:2002 "Information Technology - Abstract Syntax
2531 Notation One (ASN.1): Specification of basic notation".
2533 [BER] ITU-T Rec. X.690 (07/2002) | ISO/IEC 8825-1:2002,
2534 "Information technology - ASN.1 encoding rules:
2535 Specification of Basic Encoding Rules (BER), Canonical
2536 Encoding Rules (CER) and Distinguished Encoding Rules
2539 [ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
2540 Architecture and Basic Multilingual Plane, ISO/IEC
2543 [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
2546 [RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC
2547 793, September 1981.
2549 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
2550 Requirement Levels", BCP 14, RFC 2119, March 1997.
2552 [RFC3454] Hoffman P. and M. Blanchet, "Preparation of
2553 Internationalized Strings ('stringprep')", RFC 3454,
2556 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
2557 10646", STD 63, RFC 3629, November 2003.
2559 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
2560 "Uniform Resource Identifier (URI): Generic Syntax",
2561 STD 66, RFC 3986, January 2005.
2563 [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User
2564 Names and Passwords", RFC 4013, February 2005.
2566 [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
2567 Specifications: ABNF", RFC 4234, October 2005.
2569 [RFC4346] Dierks, T. and E. Rescorla, "The TLS Protocol Version
2570 1.1", RFC 4346, March 2006.
2572 [RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
2573 Authentication and Security Layer (SASL)", RFC 4422,
2578 Sermersheim Standards Track [Page 46]
2580 RFC 4511 LDAPv3 June 2006
2583 [RFC4510] Zeilenga, K., Ed., "Lightweight Directory Access
2584 Protocol (LDAP): Technical Specification Road Map", RFC
2587 [RFC4512] Zeilenga, K., Lightweight Directory Access Protocol
2588 (LDAP): Directory Information Models", RFC 4512, June
2591 [RFC4513] Harrison, R., Ed., "Lightweight Directory Access
2592 Protocol (LDAP): Authentication Methods and Security
2593 Mechanisms", RFC 4513, June 2006.
2595 [RFC4514] Zeilenga, K., Ed., "Lightweight Directory Access
2596 Protocol (LDAP): String Representation of Distinguished
2597 Names", RFC 4514, June 2006.
2599 [RFC4516] Smith, M., Ed. and T. Howes, "Lightweight Directory
2600 Access Protocol (LDAP): Uniform Resource Locator", RFC
2603 [RFC4517] Legg, S., Ed., "Lightweight Directory Access Protocol
2604 (LDAP): Syntaxes and Matching Rules", RFC 4517, June
2607 [RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority
2608 (IANA) Considerations for the Lightweight Directory
2609 Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
2611 [Unicode] The Unicode Consortium, "The Unicode Standard, Version
2612 3.2.0" is defined by "The Unicode Standard, Version
2613 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
2614 61633-5), as amended by the "Unicode Standard Annex
2616 (http://www.unicode.org/reports/tr27/) and by the
2617 "Unicode Standard Annex #28: Unicode 3.2"
2618 (http://www.unicode.org/reports/tr28/).
2620 [X.500] ITU-T Rec. X.500, "The Directory: Overview of Concepts,
2621 Models and Service", 1993.
2623 [X.511] ITU-T Rec. X.511, "The Directory: Abstract Service
2634 Sermersheim Standards Track [Page 47]
2636 RFC 4511 LDAPv3 June 2006
2639 9. Informative References
2641 [CharModel] Whistler, K. and M. Davis, "Unicode Technical Report
2642 #17, Character Encoding Model", UTR17,
2643 <http://www.unicode.org/unicode/reports/tr17/>, August
2646 [Glossary] The Unicode Consortium, "Unicode Glossary",
2647 <http://www.unicode.org/glossary/>.
2649 [PortReg] IANA, "Port Numbers",
2650 <http://www.iana.org/assignments/port-numbers>.
2652 [PROTOS-LDAP] University of Oulu, "PROTOS Test-Suite: c06-ldapv3"
2653 <http://www.ee.oulu.fi/research/ouspg/protos/testing/
2656 10. IANA Considerations
2658 The Internet Assigned Numbers Authority (IANA) has updated the LDAP
2659 result code registry to indicate that this document provides the
2660 definitive technical specification for result codes 0-36, 48-54, 64-
2661 70, 80-90. It is also noted that one resultCode value
2662 (strongAuthRequired) has been renamed (to strongerAuthRequired).
2664 The IANA has also updated the LDAP Protocol Mechanism registry to
2665 indicate that this document and [RFC4513] provides the definitive
2666 technical specification for the StartTLS (1.3.6.1.4.1.1466.20037)
2669 IANA has assigned LDAP Object Identifier 18 [RFC4520] to identify the
2670 ASN.1 module defined in this document.
2672 Subject: Request for LDAP Object Identifier Registration
2673 Person & email address to contact for further information:
2674 Jim Sermersheim <jimse@novell.com>
2675 Specification: RFC 4511
2676 Author/Change Controller: IESG
2678 Identifies the LDAP ASN.1 module
2690 Sermersheim Standards Track [Page 48]
2692 RFC 4511 LDAPv3 June 2006
2695 Appendix A. LDAP Result Codes
2697 This normative appendix details additional considerations regarding
2698 LDAP result codes and provides a brief, general description of each
2699 LDAP result code enumerated in Section 4.1.9.
2701 Additional result codes MAY be defined for use with extensions
2702 [RFC4520]. Client implementations SHALL treat any result code that
2703 they do not recognize as an unknown error condition.
2705 The descriptions provided here do not fully account for result code
2706 substitutions used to prevent unauthorized disclosures (such as
2707 substitution of noSuchObject for insufficientAccessRights, or
2708 invalidCredentials for insufficientAccessRights).
2710 A.1. Non-Error Result Codes
2712 These result codes (called "non-error" result codes) do not indicate
2719 saslBindInProgress (14).
2721 The success, compareTrue, and compareFalse result codes indicate
2722 successful completion (and, hence, are referred to as "successful"
2725 The referral and saslBindInProgress result codes indicate the client
2726 needs to take additional action to complete the operation.
2730 Existing LDAP result codes are described as follows:
2733 Indicates the successful completion of an operation. Note:
2734 this code is not used with the Compare operation. See
2735 compareFalse (5) and compareTrue (6).
2746 Sermersheim Standards Track [Page 49]
2748 RFC 4511 LDAPv3 June 2006
2752 Indicates that the operation is not properly sequenced with
2753 relation to other operations (of same or different type).
2755 For example, this code is returned if the client attempts to
2756 StartTLS [RFC4346] while there are other uncompleted operations
2757 or if a TLS layer was already installed.
2760 Indicates the server received data that is not well-formed.
2762 For Bind operation only, this code is also used to indicate
2763 that the server does not support the requested protocol
2766 For Extended operations only, this code is also used to
2767 indicate that the server does not support (by design or
2768 configuration) the Extended operation associated with the
2771 For request operations specifying multiple controls, this may
2772 be used to indicate that the server cannot ignore the order
2773 of the controls as specified, or that the combination of the
2774 specified controls is invalid or unspecified.
2776 timeLimitExceeded (3)
2777 Indicates that the time limit specified by the client was
2778 exceeded before the operation could be completed.
2780 sizeLimitExceeded (4)
2781 Indicates that the size limit specified by the client was
2782 exceeded before the operation could be completed.
2785 Indicates that the Compare operation has successfully
2786 completed and the assertion has evaluated to FALSE or
2790 Indicates that the Compare operation has successfully
2791 completed and the assertion has evaluated to TRUE.
2793 authMethodNotSupported (7)
2794 Indicates that the authentication method or mechanism is not
2802 Sermersheim Standards Track [Page 50]
2804 RFC 4511 LDAPv3 June 2006
2807 strongerAuthRequired (8)
2808 Indicates the server requires strong(er) authentication in
2809 order to complete the operation.
2811 When used with the Notice of Disconnection operation, this
2812 code indicates that the server has detected that an
2813 established security association between the client and
2814 server has unexpectedly failed or been compromised.
2817 Indicates that a referral needs to be chased to complete the
2818 operation (see Section 4.1.10).
2820 adminLimitExceeded (11)
2821 Indicates that an administrative limit has been exceeded.
2823 unavailableCriticalExtension (12)
2824 Indicates a critical control is unrecognized (see Section
2827 confidentialityRequired (13)
2828 Indicates that data confidentiality protections are required.
2830 saslBindInProgress (14)
2831 Indicates the server requires the client to send a new bind
2832 request, with the same SASL mechanism, to continue the
2833 authentication process (see Section 4.2).
2835 noSuchAttribute (16)
2836 Indicates that the named entry does not contain the specified
2837 attribute or attribute value.
2839 undefinedAttributeType (17)
2840 Indicates that a request field contains an unrecognized
2841 attribute description.
2843 inappropriateMatching (18)
2844 Indicates that an attempt was made (e.g., in an assertion) to
2845 use a matching rule not defined for the attribute type
2848 constraintViolation (19)
2849 Indicates that the client supplied an attribute value that
2850 does not conform to the constraints placed upon it by the
2853 For example, this code is returned when multiple values are
2854 supplied to an attribute that has a SINGLE-VALUE constraint.
2858 Sermersheim Standards Track [Page 51]
2860 RFC 4511 LDAPv3 June 2006
2863 attributeOrValueExists (20)
2864 Indicates that the client supplied an attribute or value to
2865 be added to an entry, but the attribute or value already
2868 invalidAttributeSyntax (21)
2869 Indicates that a purported attribute value does not conform
2870 to the syntax of the attribute.
2873 Indicates that the object does not exist in the DIT.
2876 Indicates that an alias problem has occurred. For example,
2877 the code may used to indicate an alias has been dereferenced
2878 that names no object.
2880 invalidDNSyntax (34)
2881 Indicates that an LDAPDN or RelativeLDAPDN field (e.g., search
2882 base, target entry, ModifyDN newrdn, etc.) of a request does
2883 not conform to the required syntax or contains attribute
2884 values that do not conform to the syntax of the attribute's
2887 aliasDereferencingProblem (36)
2888 Indicates that a problem occurred while dereferencing an
2889 alias. Typically, an alias was encountered in a situation
2890 where it was not allowed or where access was denied.
2892 inappropriateAuthentication (48)
2893 Indicates the server requires the client that had attempted
2894 to bind anonymously or without supplying credentials to
2895 provide some form of credentials.
2897 invalidCredentials (49)
2898 Indicates that the provided credentials (e.g., the user's name
2899 and password) are invalid.
2901 insufficientAccessRights (50)
2902 Indicates that the client does not have sufficient access
2903 rights to perform the operation.
2906 Indicates that the server is too busy to service the
2914 Sermersheim Standards Track [Page 52]
2916 RFC 4511 LDAPv3 June 2006
2920 Indicates that the server is shutting down or a subsystem
2921 necessary to complete the operation is offline.
2923 unwillingToPerform (53)
2924 Indicates that the server is unwilling to perform the
2928 Indicates that the server has detected an internal loop (e.g.,
2929 while dereferencing aliases or chaining an operation).
2931 namingViolation (64)
2932 Indicates that the entry's name violates naming restrictions.
2934 objectClassViolation (65)
2935 Indicates that the entry violates object class restrictions.
2937 notAllowedOnNonLeaf (66)
2938 Indicates that the operation is inappropriately acting upon a
2941 notAllowedOnRDN (67)
2942 Indicates that the operation is inappropriately attempting to
2943 remove a value that forms the entry's relative distinguished
2946 entryAlreadyExists (68)
2947 Indicates that the request cannot be fulfilled (added, moved,
2948 or renamed) as the target entry already exists.
2950 objectClassModsProhibited (69)
2951 Indicates that an attempt to modify the object class(es) of
2952 an entry's 'objectClass' attribute is prohibited.
2954 For example, this code is returned when a client attempts to
2955 modify the structural object class of an entry.
2957 affectsMultipleDSAs (71)
2958 Indicates that the operation cannot be performed as it would
2959 affect multiple servers (DSAs).
2962 Indicates the server has encountered an internal error.
2970 Sermersheim Standards Track [Page 53]
2972 RFC 4511 LDAPv3 June 2006
2975 Appendix B. Complete ASN.1 Definition
2977 This appendix is normative.
2979 Lightweight-Directory-Access-Protocol-V3 {1 3 6 1 1 18}
2980 -- Copyright (C) The Internet Society (2006). This version of
2981 -- this ASN.1 module is part of RFC 4511; see the RFC itself
2982 -- for full legal notices.
2985 EXTENSIBILITY IMPLIED ::=
2989 LDAPMessage ::= SEQUENCE {
2990 messageID MessageID,
2992 bindRequest BindRequest,
2993 bindResponse BindResponse,
2994 unbindRequest UnbindRequest,
2995 searchRequest SearchRequest,
2996 searchResEntry SearchResultEntry,
2997 searchResDone SearchResultDone,
2998 searchResRef SearchResultReference,
2999 modifyRequest ModifyRequest,
3000 modifyResponse ModifyResponse,
3001 addRequest AddRequest,
3002 addResponse AddResponse,
3003 delRequest DelRequest,
3004 delResponse DelResponse,
3005 modDNRequest ModifyDNRequest,
3006 modDNResponse ModifyDNResponse,
3007 compareRequest CompareRequest,
3008 compareResponse CompareResponse,
3009 abandonRequest AbandonRequest,
3010 extendedReq ExtendedRequest,
3011 extendedResp ExtendedResponse,
3013 intermediateResponse IntermediateResponse },
3014 controls [0] Controls OPTIONAL }
3016 MessageID ::= INTEGER (0 .. maxInt)
3018 maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
3020 LDAPString ::= OCTET STRING -- UTF-8 encoded,
3021 -- [ISO10646] characters
3026 Sermersheim Standards Track [Page 54]
3028 RFC 4511 LDAPv3 June 2006
3031 LDAPOID ::= OCTET STRING -- Constrained to <numericoid>
3034 LDAPDN ::= LDAPString -- Constrained to <distinguishedName>
3037 RelativeLDAPDN ::= LDAPString -- Constrained to <name-component>
3040 AttributeDescription ::= LDAPString
3041 -- Constrained to <attributedescription>
3044 AttributeValue ::= OCTET STRING
3046 AttributeValueAssertion ::= SEQUENCE {
3047 attributeDesc AttributeDescription,
3048 assertionValue AssertionValue }
3050 AssertionValue ::= OCTET STRING
3052 PartialAttribute ::= SEQUENCE {
3053 type AttributeDescription,
3054 vals SET OF value AttributeValue }
3056 Attribute ::= PartialAttribute(WITH COMPONENTS {
3058 vals (SIZE(1..MAX))})
3060 MatchingRuleId ::= LDAPString
3062 LDAPResult ::= SEQUENCE {
3063 resultCode ENUMERATED {
3065 operationsError (1),
3067 timeLimitExceeded (3),
3068 sizeLimitExceeded (4),
3071 authMethodNotSupported (7),
3072 strongerAuthRequired (8),
3075 adminLimitExceeded (11),
3076 unavailableCriticalExtension (12),
3077 confidentialityRequired (13),
3078 saslBindInProgress (14),
3082 Sermersheim Standards Track [Page 55]
3084 RFC 4511 LDAPv3 June 2006
3087 noSuchAttribute (16),
3088 undefinedAttributeType (17),
3089 inappropriateMatching (18),
3090 constraintViolation (19),
3091 attributeOrValueExists (20),
3092 invalidAttributeSyntax (21),
3096 invalidDNSyntax (34),
3097 -- 35 reserved for undefined isLeaf --
3098 aliasDereferencingProblem (36),
3100 inappropriateAuthentication (48),
3101 invalidCredentials (49),
3102 insufficientAccessRights (50),
3105 unwillingToPerform (53),
3108 namingViolation (64),
3109 objectClassViolation (65),
3110 notAllowedOnNonLeaf (66),
3111 notAllowedOnRDN (67),
3112 entryAlreadyExists (68),
3113 objectClassModsProhibited (69),
3114 -- 70 reserved for CLDAP --
3115 affectsMultipleDSAs (71),
3120 diagnosticMessage LDAPString,
3121 referral [3] Referral OPTIONAL }
3123 Referral ::= SEQUENCE SIZE (1..MAX) OF uri URI
3125 URI ::= LDAPString -- limited to characters permitted in
3128 Controls ::= SEQUENCE OF control Control
3130 Control ::= SEQUENCE {
3131 controlType LDAPOID,
3132 criticality BOOLEAN DEFAULT FALSE,
3133 controlValue OCTET STRING OPTIONAL }
3138 Sermersheim Standards Track [Page 56]
3140 RFC 4511 LDAPv3 June 2006
3143 BindRequest ::= [APPLICATION 0] SEQUENCE {
3144 version INTEGER (1 .. 127),
3146 authentication AuthenticationChoice }
3148 AuthenticationChoice ::= CHOICE {
3149 simple [0] OCTET STRING,
3151 sasl [3] SaslCredentials,
3154 SaslCredentials ::= SEQUENCE {
3155 mechanism LDAPString,
3156 credentials OCTET STRING OPTIONAL }
3158 BindResponse ::= [APPLICATION 1] SEQUENCE {
3159 COMPONENTS OF LDAPResult,
3160 serverSaslCreds [7] OCTET STRING OPTIONAL }
3162 UnbindRequest ::= [APPLICATION 2] NULL
3164 SearchRequest ::= [APPLICATION 3] SEQUENCE {
3171 derefAliases ENUMERATED {
3172 neverDerefAliases (0),
3173 derefInSearching (1),
3174 derefFindingBaseObj (2),
3176 sizeLimit INTEGER (0 .. maxInt),
3177 timeLimit INTEGER (0 .. maxInt),
3180 attributes AttributeSelection }
3182 AttributeSelection ::= SEQUENCE OF selector LDAPString
3183 -- The LDAPString is constrained to
3184 -- <attributeSelector> in Section 4.5.1.8
3187 and [0] SET SIZE (1..MAX) OF filter Filter,
3188 or [1] SET SIZE (1..MAX) OF filter Filter,
3190 equalityMatch [3] AttributeValueAssertion,
3194 Sermersheim Standards Track [Page 57]
3196 RFC 4511 LDAPv3 June 2006
3199 substrings [4] SubstringFilter,
3200 greaterOrEqual [5] AttributeValueAssertion,
3201 lessOrEqual [6] AttributeValueAssertion,
3202 present [7] AttributeDescription,
3203 approxMatch [8] AttributeValueAssertion,
3204 extensibleMatch [9] MatchingRuleAssertion,
3207 SubstringFilter ::= SEQUENCE {
3208 type AttributeDescription,
3209 substrings SEQUENCE SIZE (1..MAX) OF substring CHOICE {
3210 initial [0] AssertionValue, -- can occur at most once
3211 any [1] AssertionValue,
3212 final [2] AssertionValue } -- can occur at most once
3215 MatchingRuleAssertion ::= SEQUENCE {
3216 matchingRule [1] MatchingRuleId OPTIONAL,
3217 type [2] AttributeDescription OPTIONAL,
3218 matchValue [3] AssertionValue,
3219 dnAttributes [4] BOOLEAN DEFAULT FALSE }
3221 SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
3223 attributes PartialAttributeList }
3225 PartialAttributeList ::= SEQUENCE OF
3226 partialAttribute PartialAttribute
3228 SearchResultReference ::= [APPLICATION 19] SEQUENCE
3229 SIZE (1..MAX) OF uri URI
3231 SearchResultDone ::= [APPLICATION 5] LDAPResult
3233 ModifyRequest ::= [APPLICATION 6] SEQUENCE {
3235 changes SEQUENCE OF change SEQUENCE {
3236 operation ENUMERATED {
3241 modification PartialAttribute } }
3243 ModifyResponse ::= [APPLICATION 7] LDAPResult
3250 Sermersheim Standards Track [Page 58]
3252 RFC 4511 LDAPv3 June 2006
3255 AddRequest ::= [APPLICATION 8] SEQUENCE {
3257 attributes AttributeList }
3259 AttributeList ::= SEQUENCE OF attribute Attribute
3261 AddResponse ::= [APPLICATION 9] LDAPResult
3263 DelRequest ::= [APPLICATION 10] LDAPDN
3265 DelResponse ::= [APPLICATION 11] LDAPResult
3267 ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
3269 newrdn RelativeLDAPDN,
3270 deleteoldrdn BOOLEAN,
3271 newSuperior [0] LDAPDN OPTIONAL }
3273 ModifyDNResponse ::= [APPLICATION 13] LDAPResult
3275 CompareRequest ::= [APPLICATION 14] SEQUENCE {
3277 ava AttributeValueAssertion }
3279 CompareResponse ::= [APPLICATION 15] LDAPResult
3281 AbandonRequest ::= [APPLICATION 16] MessageID
3283 ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
3284 requestName [0] LDAPOID,
3285 requestValue [1] OCTET STRING OPTIONAL }
3287 ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
3288 COMPONENTS OF LDAPResult,
3289 responseName [10] LDAPOID OPTIONAL,
3290 responseValue [11] OCTET STRING OPTIONAL }
3292 IntermediateResponse ::= [APPLICATION 25] SEQUENCE {
3293 responseName [0] LDAPOID OPTIONAL,
3294 responseValue [1] OCTET STRING OPTIONAL }
3306 Sermersheim Standards Track [Page 59]
3308 RFC 4511 LDAPv3 June 2006
3313 This appendix is non-normative.
3315 This appendix summarizes substantive changes made to RFC 2251, RFC
3318 C.1. Changes Made to RFC 2251
3320 This section summarizes the substantive changes made to Sections 1,
3321 2, 3.1, and 4, and the remainder of RFC 2251. Readers should
3322 consult [RFC4512] and [RFC4513] for summaries of changes to other
3325 C.1.1. Section 1 (Status of this Memo)
3327 - Removed IESG note. Post publication of RFC 2251, mandatory LDAP
3328 authentication mechanisms have been standardized which are
3329 sufficient to remove this note. See [RFC4513] for authentication
3332 C.1.2. Section 3.1 (Protocol Model) and others
3334 - Removed notes giving history between LDAP v1, v2, and v3. Instead,
3335 added sufficient language so that this document can stand on its
3338 C.1.3. Section 4 (Elements of Protocol)
3340 - Clarified where the extensibility features of ASN.1 apply to the
3341 protocol. This change affected various ASN.1 types by the
3342 inclusion of ellipses (...) to certain elements.
3343 - Removed the requirement that servers that implement version 3 or
3344 later MUST provide the 'supportedLDAPVersion' attribute. This
3345 statement provided no interoperability advantages.
3347 C.1.4. Section 4.1.1 (Message Envelope)
3349 - There was a mandatory requirement for the server to return a
3350 Notice of Disconnection and drop the transport connection when a
3351 PDU is malformed in a certain way. This has been updated such that
3352 the server SHOULD return the Notice of Disconnection, and it MUST
3353 terminate the LDAP Session.
3355 C.1.5. Section 4.1.1.1 (Message ID)
3357 - Required that the messageID of requests MUST be non-zero as the
3358 zero is reserved for Notice of Disconnection.
3362 Sermersheim Standards Track [Page 60]
3364 RFC 4511 LDAPv3 June 2006
3367 - Specified when it is and isn't appropriate to return an already
3368 used messageID. RFC 2251 accidentally imposed synchronous server
3369 behavior in its wording of this.
3371 C.1.6. Section 4.1.2 (String Types)
3373 - Stated that LDAPOID is constrained to <numericoid> from [RFC4512].
3375 C.1.7. Section 4.1.5.1 (Binary Option) and others
3377 - Removed the Binary Option from the specification. There are
3378 numerous interoperability problems associated with this method of
3379 alternate attribute type encoding. Work to specify a suitable
3380 replacement is ongoing.
3382 C.1.8. Section 4.1.8 (Attribute)
3384 - Combined the definitions of PartialAttribute and Attribute here,
3385 and defined Attribute in terms of PartialAttribute.
3387 C.1.9. Section 4.1.10 (Result Message)
3389 - Renamed "errorMessage" to "diagnosticMessage" as it is allowed to
3390 be sent for non-error results.
3391 - Moved some language into Appendix A, and referred the reader there.
3392 - Allowed matchedDN to be present for other result codes than those
3394 - Renamed the code "strongAuthRequired" to "strongerAuthRequired" to
3395 clarify that this code may often be returned to indicate that a
3396 stronger authentication is needed to perform a given operation.
3398 C.1.10. Section 4.1.11 (Referral)
3400 - Defined referrals in terms of URIs rather than URLs.
3401 - Removed the requirement that all referral URIs MUST be equally
3402 capable of progressing the operation. The statement was ambiguous
3403 and provided no instructions on how to carry it out.
3404 - Added the requirement that clients MUST NOT loop between servers.
3405 - Clarified the instructions for using LDAPURLs in referrals, and in
3406 doing so added a recommendation that the scope part be present.
3407 - Removed imperatives which required clients to use URLs in specific
3408 ways to progress an operation. These did nothing for
3418 Sermersheim Standards Track [Page 61]
3420 RFC 4511 LDAPv3 June 2006
3423 C.1.11. Section 4.1.12 (Controls)
3425 - Specified how control values defined in terms of ASN.1 are to be
3427 - Noted that the criticality field is only applied to request
3428 messages (except UnbindRequest), and must be ignored when present
3429 on response messages and UnbindRequest.
3430 - Specified that non-critical controls may be ignored at the
3431 server's discretion. There was confusion in the original wording
3432 which led some to believe that recognized controls may not be
3433 ignored as long as they were associated with a proper request.
3434 - Added language regarding combinations of controls and the ordering
3435 of controls on a message.
3436 - Specified that when the semantics of the combination of controls
3437 is undefined or unknown, it results in a protocolError.
3438 - Changed "The server MUST be prepared" to "Implementations MUST be
3439 prepared" in paragraph 8 to reflect that both client and server
3440 implementations must be able to handle this (as both parse
3443 C.1.12. Section 4.2 (Bind Operation)
3445 - Mandated that servers return protocolError when the version is not
3447 - Disambiguated behavior when the simple authentication is used, the
3448 name is empty, and the password is non-empty.
3449 - Required servers to not dereference aliases for Bind. This was
3450 added for consistency with other operations and to help ensure
3452 - Required that textual passwords be transferred as UTF-8 encoded
3453 Unicode, and added recommendations on string preparation. This was
3454 to help ensure interoperability of passwords being sent from
3457 C.1.13. Section 4.2.1 (Sequencing of the Bind Request)
3459 - This section was largely reorganized for readability, and language
3460 was added to clarify the authentication state of failed and
3461 abandoned Bind operations.
3462 - Removed: "If a SASL transfer encryption or integrity mechanism has
3463 been negotiated, that mechanism does not support the changing of
3464 credentials from one identity to another, then the client MUST
3465 instead establish a new connection."
3466 If there are dependencies between multiple negotiations of a
3467 particular SASL mechanism, the technical specification for that
3468 SASL mechanism details how applications are to deal with them.
3469 LDAP should not require any special handling.
3470 - Dropped MUST imperative in paragraph 3 to align with [RFC2119].
3474 Sermersheim Standards Track [Page 62]
3476 RFC 4511 LDAPv3 June 2006
3479 - Mandated that clients not send non-Bind operations while a Bind is
3480 in progress, and suggested that servers not process them if they
3481 are received. This is needed to ensure proper sequencing of the
3482 Bind in relationship to other operations.
3484 C.1.14. Section 4.2.3 (Bind Response)
3486 - Moved most error-related text to Appendix A, and added text
3487 regarding certain errors used in conjunction with the Bind
3489 - Prohibited the server from specifying serverSaslCreds when not
3492 C.1.15. Section 4.3 (Unbind Operation)
3494 - Specified that both peers are to cease transmission and terminate
3495 the LDAP session for the Unbind operation.
3497 C.1.16. Section 4.4 (Unsolicited Notification)
3499 - Added instructions for future specifications of Unsolicited
3502 C.1.17. Section 4.5.1 (Search Request)
3504 - SearchRequest attributes is now defined as an AttributeSelection
3505 type rather than AttributeDescriptionList, and an ABNF is
3507 - SearchRequest attributes may contain duplicate attribute
3508 descriptions. This was previously prohibited. Now servers are
3509 instructed to ignore subsequent names when they are duplicated.
3510 This was relaxed in order to allow different short names and also
3511 OIDs to be requested for an attribute.
3512 - The present search filter now evaluates to Undefined when the
3513 specified attribute is not known to the server. It used to
3514 evaluate to FALSE, which caused behavior inconsistent with what
3515 most would expect, especially when the 'not' operator was used.
3516 - The Filter choice SubstringFilter substrings type is now defined
3517 with a lower bound of 1.
3518 - The SubstringFilter substrings 'initial, 'any', and 'final' types
3519 are now AssertionValue rather than LDAPString. Also, added
3520 imperatives stating that 'initial' (if present) must be listed
3521 first, and 'final' (if present) must be listed last.
3522 - Disambiguated the semantics of the derefAliases choices. There was
3523 question as to whether derefInSearching applied to the base object
3524 in a wholeSubtree Search.
3525 - Added instructions for equalityMatch, substrings, greaterOrEqual,
3526 lessOrEqual, and approxMatch.
3530 Sermersheim Standards Track [Page 63]
3532 RFC 4511 LDAPv3 June 2006
3536 C.1.18. Section 4.5.2 (Search Result)
3538 - Recommended that servers not use attribute short names when it
3539 knows they are ambiguous or may cause interoperability problems.
3540 - Removed all mention of ExtendedResponse due to lack of
3543 C.1.19. Section 4.5.3 (Continuation References in the Search Result)
3545 - Made changes similar to those made to Section 4.1.11.
3547 C.1.20. Section 4.5.3.1 (Example)
3549 - Fixed examples to adhere to changes made to Section 4.5.3.
3551 C.1.21. Section 4.6 (Modify Operation)
3553 - Replaced AttributeTypeAndValues with Attribute as they are
3555 - Specified the types of modification changes that might
3556 temporarily violate schema. Some readers were under the impression
3557 that any temporary schema violation was allowed.
3559 C.1.22. Section 4.7 (Add Operation)
3561 - Aligned Add operation with X.511 in that the attributes of the RDN
3562 are used in conjunction with the listed attributes to create the
3563 entry. Previously, Add required that the distinguished values be
3564 present in the listed attributes.
3565 - Removed requirement that the objectClass attribute MUST be
3566 specified as some DSE types do not require this attribute.
3567 Instead, generic wording was added, requiring the added entry to
3568 adhere to the data model.
3569 - Removed recommendation regarding placement of objects. This is
3570 covered in the data model document.
3572 C.1.23. Section 4.9 (Modify DN Operation)
3574 - Required servers to not dereference aliases for Modify DN. This
3575 was added for consistency with other operations and to help ensure
3577 - Allow Modify DN to fail when moving between naming contexts.
3578 - Specified what happens when the attributes of the newrdn are not
3579 present on the entry.
3586 Sermersheim Standards Track [Page 64]
3588 RFC 4511 LDAPv3 June 2006
3591 C.1.24. Section 4.10 (Compare Operation)
3593 - Specified that compareFalse means that the Compare took place and
3594 the result is false. There was confusion that led people to
3595 believe that an Undefined match resulted in compareFalse.
3596 - Required servers to not dereference aliases for Compare. This was
3597 added for consistency with other operations and to help ensure
3600 C.1.25. Section 4.11 (Abandon Operation)
3602 - Explained that since Abandon returns no response, clients should
3603 not use it if they need to know the outcome.
3604 - Specified that Abandon and Unbind cannot be abandoned.
3606 C.1.26. Section 4.12 (Extended Operation)
3608 - Specified how values of Extended operations defined in terms of
3609 ASN.1 are to be encoded.
3610 - Added instructions on what Extended operation specifications
3612 - Added a recommendation that servers advertise supported Extended
3615 C.1.27. Section 5.2 (Transfer Protocols)
3617 - Moved referral-specific instructions into referral-related
3620 C.1.28. Section 7 (Security Considerations)
3622 - Reworded notes regarding SASL not protecting certain aspects of
3623 the LDAP Bind messages.
3624 - Noted that Servers are encouraged to prevent directory
3625 modifications by clients that have authenticated anonymously
3627 - Added a note regarding the possibility of changes to security
3628 factors (authentication, authorization, and data confidentiality).
3629 - Warned against following referrals that may have been injected in
3631 - Noted that servers should protect information equally, whether in
3632 an error condition or not, and mentioned matchedDN,
3633 diagnosticMessage, and resultCodes specifically.
3634 - Added a note regarding malformed and long encodings.
3642 Sermersheim Standards Track [Page 65]
3644 RFC 4511 LDAPv3 June 2006
3647 C.1.29. Appendix A (Complete ASN.1 Definition)
3649 - Added "EXTENSIBILITY IMPLIED" to ASN.1 definition.
3650 - Removed AttributeType. It is not used.
3652 C.2. Changes Made to RFC 2830
3654 This section summarizes the substantive changes made to Sections of
3655 RFC 2830. Readers should consult [RFC4513] for summaries of changes
3658 C.2.1. Section 2.3 (Response other than "success")
3660 - Removed wording indicating that referrals can be returned from
3662 - Removed requirement that only a narrow set of result codes can be
3663 returned. Some result codes are required in certain scenarios, but
3664 any other may be returned if appropriate.
3665 - Removed requirement that the ExtendedResponse.responseName MUST be
3666 present. There are circumstances where this is impossible, and
3667 requiring this is at odds with language in Section 4.12.
3669 C.2.1. Section 4 (Closing a TLS Connection)
3671 - Reworded most of this section to align with definitions of the
3672 LDAP protocol layers.
3673 - Removed instructions on abrupt closure as this is covered in other
3674 areas of the document (specifically, Section 5.3)
3676 C.3. Changes Made to RFC 3771
3678 - Rewrote to fit into this document. In general, semantics were
3679 preserved. Supporting and background language seen as redundant
3680 due to its presence in this document was omitted.
3682 - Specified that Intermediate responses to a request may be of
3683 different types, and one of the response types may be specified to
3684 have no response value.
3698 Sermersheim Standards Track [Page 66]
3700 RFC 4511 LDAPv3 June 2006
3707 1800 South Novell Place
3708 Provo, Utah 84606, USA
3710 Phone: +1 801 861-3088
3711 EMail: jimse@novell.com
3754 Sermersheim Standards Track [Page 67]
3756 RFC 4511 LDAPv3 June 2006
3759 Full Copyright Statement
3761 Copyright (C) The Internet Society (2006).
3763 This document is subject to the rights, licenses and restrictions
3764 contained in BCP 78, and except as set forth therein, the authors
3765 retain all their rights.
3767 This document and the information contained herein are provided on an
3768 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
3769 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
3770 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
3771 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
3772 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
3773 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
3775 Intellectual Property
3777 The IETF takes no position regarding the validity or scope of any
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3779 pertain to the implementation or use of the technology described in
3780 this document or the extent to which any license under such rights
3781 might or might not be available; nor does it represent that it has
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3783 on the procedures with respect to rights in RFC documents can be
3784 found in BCP 78 and BCP 79.
3786 Copies of IPR disclosures made to the IETF Secretariat and any
3787 assurances of licenses to be made available, or the result of an
3788 attempt made to obtain a general license or permission for the use of
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3791 http://www.ietf.org/ipr.
3793 The IETF invites any interested party to bring to its attention any
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3802 Administrative Support Activity (IASA).
3810 Sermersheim Standards Track [Page 68]
projects / openldap / blob