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Internet-Draft Editor: J. Sermersheim
Intended Category: Standard Track Novell, Inc
Document: draft-ietf-ldapbis-protocol-13.txt Mar 2003
Obsoletes: RFC 2251
LDAP: The Protocol
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Distribution of this memo is unlimited. Technical discussion of this
document will take place on the IETF LDAP Revision Working Group
(LDAPbis) mailing list <ietf-ldapbis@openldap.org>. Please send
editorial comments directly to the editor <jimse@novell.com>.
Abstract
This document describes the protocol elements, along with their
semantics and encodings, for the Lightweight Directory Access
Protocol (LDAP). LDAP provides access to distributed directory
services that act in accordance with X.500 data and service models.
These protocol elements are based on those described in the X.500
Directory Access Protocol (DAP).
Table of Contents
1. Introduction.....................................................2
2. Conventions......................................................3
3. Protocol Model...................................................3
4. Elements of Protocol.............................................3
4.1. Common Elements................................................4
4.1.1. Message Envelope.............................................4
4.1.2. String Types.................................................6
4.1.3. Distinguished Name and Relative Distinguished Name...........6
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Lightweight Directory Access Protocol Version 3
4.1.4. Attribute Descriptions.......................................6
4.1.5. Attribute Value..............................................7
4.1.6. Attribute Value Assertion....................................7
4.1.7. Attribute....................................................7
4.1.8. Matching Rule Identifier.....................................8
4.1.9. Result Message...............................................8
4.1.10. Referral...................................................10
4.1.11. Controls...................................................11
4.2. Bind Operation................................................12
4.3. Unbind Operation..............................................14
4.4. Unsolicited Notification......................................15
4.5. Search Operation..............................................16
4.6. Modify Operation..............................................23
4.7. Add Operation.................................................24
4.8. Delete Operation..............................................25
4.9. Modify DN Operation...........................................26
4.10. Compare Operation............................................27
4.11. Abandon Operation............................................28
4.12. Extended Operation...........................................28
4.13. Start TLS Operation..........................................29
5. Protocol Element Encodings and Transfer.........................31
5.1. Protocol Encoding.............................................31
5.2. Transfer Protocols............................................31
6. Implementation Guidelines.......................................32
6.1. Server Implementations........................................32
6.2. Client Implementations........................................32
7. Security Considerations.........................................32
8. Acknowledgements................................................33
9. Normative References............................................33
10. Editor's Address...............................................34
Appendix A - LDAP Result Codes.....................................35
A.1 Non-Error Result Codes.........................................35
A.2 Error Result Codes.............................................35
A.3 Classes and Precedence of Error Result Codes...................35
Appendix C - Change History........................................46
C.1 Changes made to RFC 2251:......................................46
C.2 Changes made to draft-ietf-ldapbis-protocol-00.txt:............46
C.3 Changes made to draft-ietf-ldapbis-protocol-01.txt:............47
C.4 Changes made to draft-ietf-ldapbis-protocol-02.txt:............47
C.5 Changes made to draft-ietf-ldapbis-protocol-03.txt:............49
C.6 Changes made to draft-ietf-ldapbis-protocol-04.txt:............51
C.7 Changes made to draft-ietf-ldapbis-protocol-05.txt:............51
C.8 Changes made to draft-ietf-ldapbis-protocol-06.txt:............52
C.9 Changes made to draft-ietf-ldapbis-protocol-07.txt:............55
C.10 Changes made to draft-ietf-ldapbis-protocol-08.txt:...........55
C.11 Changes made to draft-ietf-ldapbis-protocol-09.txt:...........55
C.12 Changes made to draft-ietf-ldapbis-protocol-10.txt:...........55
C.13 Changes made to draft-ietf-ldapbis-protocol-11.txt:...........56
C.14 Changes made to draft-ietf-ldapbis-protocol-12.txt:...........56
Appendix D - Outstanding Work Items................................56
1. Introduction
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Lightweight Directory Access Protocol Version 3
The Directory is "a collection of open systems cooperating to provide
directory services" [X.500]. A Directory user, which may be a human
or other entity, accesses the Directory through a client (or
Directory User Agent (DUA)). The client, on behalf of the directory
user, interacts with one or more servers (or Directory System Agents
(DSA)). Clients interact with servers using a directory access
protocol.
This document details the protocol elements of Lightweight Directory
Access Protocol, along with their semantics. Following the
description of protocol elements, it describes the way in which the
protocol is encoded and transferred.
This document is an integral part of the LDAP Technical Specification
[Roadmap].
This document replaces RFC 2251. Appendix C holds a detailed log of
changes to RFC 2251. Prior to Working Group Last Call, this appendix
will be distilled to a summary of changes to RFC 2251.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY" in this document are
to be interpreted as described in [RFC2119].
3. Protocol Model
The general model adopted by this protocol is one of clients
performing protocol operations against servers. In this model, a
client transmits a protocol request describing the operation to be
performed to a server. The server is then responsible for performing
the necessary operation(s) in the directory. Upon completion of the
operation(s), the server returns a response containing any results or
errors to the requesting client.
Note that although servers are required to return responses whenever
such responses are defined in the protocol, there is no requirement
for synchronous behavior on the part of either clients or servers.
Requests and responses for multiple operations may be exchanged
between a client and server in any order, provided the client
eventually receives a response for every request that requires one.
Note that the core protocol operations defined in this document can
be mapped to a subset of the X.500(1997) directory abstract service.
However there is not a one-to-one mapping between LDAP protocol
operations and DAP operations. Server implementations acting as a
gateway to X.500 directories may need to make multiple DAP requests.
4. Elements of Protocol
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Lightweight Directory Access Protocol Version 3
The LDAP protocol is described using Abstract Syntax Notation 1
(ASN.1) [X.680], and is transferred using a subset of ASN.1 Basic
Encoding Rules [X.690]. Section 5.1 specifies how the protocol is
encoded and transferred.
In order to support future Standards Track extensions to this
protocol, extensibility is implied where it is allowed (per ASN.1).
In addition, ellipses (...) have been supplied in ASN.1 types that
are explicitly extensible as discussed in [LDAPIANA]. Because of the
implied extensibility, clients and servers MUST ignore trailing
SEQUENCE elements whose tags they do not recognize.
Changes to the LDAP protocol other than through the extension
mechanisms described here require a different version number. A
client indicates the version it is using as part of the bind request,
described in section 4.2. If a client has not sent a bind, the server
MUST assume the client is using version 3 or later.
Clients may determine the protocol versions a server supports by
reading the supportedLDAPVersion attribute from the root DSE
[Models]. Servers which implement version 3 or later MUST provide
this attribute.
4.1. Common Elements
This section describes the LDAPMessage envelope PDU (Protocol Data
Unit) format, as well as data type definitions, which are used in the
protocol operations.
4.1.1. Message Envelope
For the purposes of protocol exchanges, all protocol operations are
encapsulated in a common envelope, the LDAPMessage, which is defined
as follows:
LDAPMessage ::= SEQUENCE {
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
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modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse,
... },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
The function of the LDAPMessage is to provide an envelope containing
common fields required in all protocol exchanges. At this time the
only common fields are the message ID and the controls.
If the server receives a PDU from the client in which the LDAPMessage
SEQUENCE tag cannot be recognized, the messageID cannot be parsed,
the tag of the protocolOp is not recognized as a request, or the
encoding structures or lengths of data fields are found to be
incorrect, then the server MAY return the Notice of Disconnection
described in section 4.4.1, with resultCode protocolError, and MUST
immediately close the connection.
In other cases where the client or server cannot parse a PDU, it
SHOULD abruptly close the connection where further communication
(including providing notice) would be pernicious. Otherwise, server
implementations MUST return an appropriate response to the request,
with the resultCode set to protocolError.
The ASN.1 type Controls is defined in section 4.1.11.
4.1.1.1. Message ID
All LDAPMessage envelopes encapsulating responses contain the
messageID value of the corresponding request LDAPMessage.
The message ID of a request MUST have a non-zero value different from
the values of any other requests outstanding in the LDAP session of
which this message is a part. The zero value is reserved for the
unsolicited notification message.
Typical clients increment a counter for each request.
A client MUST NOT send a request with the same message ID as an
earlier request on the same connection unless it can be determined
that the server is no longer servicing the earlier request. Otherwise
the behavior is undefined. For operations that do not return
responses (unbind, abandon, and abandoned operations), the client
SHOULD assume the operation is in progress until a subsequent bind
request completes.
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4.1.2. String Types
The LDAPString is a notational convenience to indicate that, although
strings of LDAPString type encode as OCTET STRING types, the
[ISO10646] character set (a superset of Unicode) is used, encoded
following the UTF-8 algorithm [RFC2279]. Note that in the UTF-8
algorithm characters which are the same as ASCII (0x0000 through
0x007F) are represented as that same ASCII character in a single
byte. The other byte values are used to form a variable-length
encoding of an arbitrary character.
LDAPString ::= OCTET STRING -- UTF-8 encoded,
-- ISO 10646 characters
The LDAPOID is a notational convenience to indicate that the
permitted value of this string is a (UTF-8 encoded) dotted-decimal
representation of an OBJECT IDENTIFIER. Although an LDAPOID is
encoded as an OCTET STRING, values are limited to the definition of
numericoid given in Section 1.3 of [Models].
LDAPOID ::= OCTET STRING -- Constrained to numericoid [Models]
For example,
1.3.6.1.4.1.1466.1.2.3
4.1.3. Distinguished Name and Relative Distinguished Name
An LDAPDN and a RelativeLDAPDN are respectively defined to be the
representation of a distinguished-name and a relative-distinguished-
name after encoding according to the specification in [LDAPDN].
LDAPDN ::= LDAPString
-- Constrained to distinguishedName [LDAPDN]
RelativeLDAPDN ::= LDAPString
-- Constrained to name-component [LDAPDN]
4.1.4. Attribute Descriptions
The definition and encoding rules for attribute descriptions are
defined in Section 2.5 of [Models]. Briefly, an attribute description
is an attribute type and zero or more options.
AttributeDescription ::= LDAPString
-- Constrained to attributedescription
-- [Models]
An AttributeDescriptionList describes a list of 0 or more attribute
descriptions. (A list of zero elements has special significance in
the Search request.)
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AttributeDescriptionList ::= SEQUENCE OF
AttributeDescription
4.1.5. Attribute Value
A field of type AttributeValue is an OCTET STRING containing an
encoded attribute value data type. The value is encoded according to
its LDAP-specific encoding definition. The LDAP-specific encoding
definitions for different syntaxes and attribute types may be found
in other documents, and in particular [Syntaxes].
AttributeValue ::= OCTET STRING
Note that there is no defined limit on the size of this encoding;
thus protocol values may include multi-megabyte attributes (e.g.
photographs).
Attributes may be defined which have arbitrary and non-printable
syntax. Implementations MUST NOT display nor attempt to decode as
ASN.1, a value if its syntax is not known. The implementation may
attempt to discover the subschema of the source entry, and retrieve
the values of attributeTypes from it.
Clients MUST NOT send attribute values in a request that are not
valid according to the syntax defined for the attributes.
4.1.6. Attribute Value Assertion
The AttributeValueAssertion type definition is similar to the one in
the X.500 directory standards. It contains an attribute description
and a matching rule assertion value suitable for that type.
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
The syntax of the AssertionValue depends on the context of the LDAP
operation being performed. For example, the syntax of the EQUALITY
matching rule for an attribute is used when performing a Compare
operation. Often this is the same syntax used for values of the
attribute type, but in some cases the assertion syntax differs from
the value syntax. See objectIdentiferFirstComponentMatch in
[Syntaxes] for an example.
4.1.7. Attribute
An attribute consists of an attribute description and one or more
values of that attribute description. (Though attributes MUST have at
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least one value when stored, due to access control restrictions the
set may be empty when transferred from the server to the client. This
is described in section 4.5.2, concerning the PartialAttributeList
type.)
Attribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Each attribute value is distinct in the set (no duplicates). The set
of attribute values is unordered. Implementations MUST NOT reply upon
any apparent ordering being repeatable.
4.1.8. Matching Rule Identifier
Matching rules are defined in 4.1.3 of [Models]. A matching rule is
identified in the LDAP protocol by the printable representation of
either its numericoid, or one of its short name descriptors, e.g.
"caseIgnoreIA5Match" or "1.3.6.1.4.1.453.33.33".
MatchingRuleId ::= LDAPString
Servers which support matching rules for use in the extensibleMatch
search filter MUST list the matching rules they implement in
subschema entries, using the matchingRules attributes. The server
SHOULD also list there, using the matchingRuleUse attribute, the
attribute types with which each matching rule can be used. More
information is given in section 4.5 of [Syntaxes].
4.1.9. Result Message
The LDAPResult is the construct used in this protocol to return
success or failure indications from servers to clients. To various
requests, servers will return responses of LDAPResult or responses
containing the components of LDAPResult to indicate the final status
of a protocol operation request.
LDAPResult ::= SEQUENCE {
resultCode ENUMERATED {
success (0),
operationsError (1),
protocolError (2),
timeLimitExceeded (3),
sizeLimitExceeded (4),
compareFalse (5),
compareTrue (6),
authMethodNotSupported (7),
strongAuthRequired (8),
-- 9 reserved --
referral (10),
adminLimitExceeded (11),
unavailableCriticalExtension (12),
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confidentialityRequired (13),
saslBindInProgress (14),
noSuchAttribute (16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation (19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
noSuchObject (32),
aliasProblem (33),
invalidDNSyntax (34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
invalidCredentials (49),
insufficientAccessRights (50),
busy (51),
unavailable (52),
unwillingToPerform (53),
loopDetect (54),
-- 55-63 unused --
namingViolation (64),
objectClassViolation (65),
notAllowedOnNonLeaf (66),
notAllowedOnRDN (67),
entryAlreadyExists (68),
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71),
-- 72-79 unused --
other (80),
... },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
diagnosticMessage LDAPString,
referral [3] Referral OPTIONAL }
The result codes enumeration is extensible as defined in Section 3.5
of [LDAPIANA]. The meanings of the result codes are given in Appendix
A.
The diagnosticMessage field of this construct may, at the server's
option, be used to return a string containing a textual, human-
readable (terminal control and page formatting characters should be
avoided) diagnostic message. As this diagnostic message is not
standardized, implementations MUST NOT rely on the values returned.
If the server chooses not to return a textual diagnostic, the
diagnosticMessage field of the LDAPResult type MUST contain a zero
length string.
For certain result codes (typically, but not restricted to
noSuchObject, aliasProblem, invalidDNSyntax and
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aliasDereferencingProblem), the matchedDN field is set to the name of
the lowest entry (object or alias) in the directory that was matched.
If no aliases were dereferenced while attempting to locate the entry,
this will be a truncated form of the name provided, or if aliases
were dereferenced, of the resulting name, as defined in section 12.5
of [X.511]. The matchedDN field contains a zero length string with
all other result codes.
4.1.10. Referral
The referral result code indicates that the contacted server does not
hold the target entry of the request. The referral field is present
in an LDAPResult if the LDAPResult.resultCode field value is
referral, and absent with all other result codes. It contains one or
more references to one or more servers or services that may be
accessed via LDAP or other protocols. Referrals can be returned in
response to any operation request (except unbind and abandon which do
not have responses). At least one URL MUST be present in the
Referral.
During a search operation, after the baseObject is located, and
entries are being evaluated, the referral is not returned. Instead,
continuation references, described in section 4.5.3, are returned
when the search scope spans multiple naming contexts, and several
different servers would need to be contacted to complete the
operation.
Referral ::= SEQUENCE OF LDAPURL -- one or more
LDAPURL ::= LDAPString -- limited to characters permitted in
-- URLs
If the client wishes to progress the operation, it MUST follow the
referral by contacting one of the servers. If multiple URLs are
present, the client assumes that any URL may be used to progress the
operation.
URLs for servers implementing the LDAP protocol are written according
to [LDAPURL]. If an alias was dereferenced, the <dn> part of the URL
MUST be present, with the new target object name. If the <dn> part is
present, the client MUST use this name in its next request to
progress the operation, and if it is not present the client will use
the same name as in the original request. Some servers (e.g.
participating in distributed indexing) may provide a different filter
in a referral for a search operation. If the filter part of the URL
is present in an LDAPURL, the client MUST use this filter in its next
request to progress this search, and if it is not present the client
MUST use the same filter as it used for that search. Other aspects of
the new request may be the same or different as the request which
generated the referral.
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Note that UTF-8 characters appearing in a DN or search filter may not
be legal for URLs (e.g. spaces) and MUST be escaped using the %
method in [RFC2396].
Other kinds of URLs may be returned, so long as the operation could
be performed using that protocol.
4.1.11. Controls
A control is a way to specify extension information for an LDAP
message. A control only alters the semantics of the message it is
attached to.
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
The controlType field MUST be a UTF-8 encoded dotted-decimal
representation of an OBJECT IDENTIFIER which uniquely identifies the
control. This prevents conflicts between control names.
The criticality field is either TRUE or FALSE and only applies to
request messages that have a corresponding response message. For all
other messages (such as abandonRequest, unbindRequest and all
response messages), the criticality field is treated as FALSE.
If the server recognizes the control type and it is appropriate for
the operation, the server will make use of the control when
performing the operation.
If the server does not recognize the control type or it is not
appropriate for the operation, and the criticality field is TRUE, the
server MUST NOT perform the operation, and MUST instead return the
resultCode unavailableCriticalExtension.
If the control is unrecognized or inappropriate but the criticality
field is FALSE, the server MUST ignore the control.
The controlValue contains any information associated with the
control, and its format is defined for the control. Implementations
MUST be prepared to handle arbitrary contents of the controlValue
octet string, including zero bytes. It is absent only if there is no
value information which is associated with a control of its type.
This document does not specify any controls. Controls may be
specified in other documents. The specification of a control consists
of:
- the OBJECT IDENTIFIER assigned to the control,
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- whether the control is always noncritical, always critical, or
critical at the client's option,
- the format of the controlValue contents of the control,
- the semantics of the control,
- and optionally, semantics regarding the combination of the control
with other controls.
Servers list the controlType of all request controls they recognize
in the supportedControl attribute [Models] in the root DSE.
Controls should not be combined unless the semantics of the
combination has been specified. The semantics of control
combinations, if specified, are generally found in the control
specification most recently published. In the absence of combination
semantics, the behavior of the operation is undefined.
Additionally, the order of a combination of controls in the SEQUENCE
is ignored unless the control specification(s) describe(s)
combination semantics.
4.2. Bind Operation
The function of the Bind Operation is to allow authentication
information to be exchanged between the client and server. Prior to
the first BindRequest, the implied identity is anonymous. Refer to
[AuthMeth] for the authentication-related semantics of this
operation.
The Bind Request is defined as follows:
BindRequest ::= [APPLICATION 0] SEQUENCE {
version INTEGER (1 .. 127),
name LDAPDN,
authentication AuthenticationChoice }
AuthenticationChoice ::= CHOICE {
simple [0] OCTET STRING,
-- 1 and 2 reserved
sasl [3] SaslCredentials,
... }
SaslCredentials ::= SEQUENCE {
mechanism LDAPString,
credentials OCTET STRING OPTIONAL }
Parameters of the Bind Request are:
- version: A version number indicating the version of the protocol
to be used in this protocol session. This document describes
version 3 of the LDAP protocol. Note that there is no version
negotiation, and the client just sets this parameter to the
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Lightweight Directory Access Protocol Version 3
version it desires. If the server does not support the specified
version, it responds with protocolError in the resultCode field of
the BindResponse.
- name: The name of the directory object that the client wishes to
bind as. This field may take on a null value (a zero length
string) for the purposes of anonymous binds ([AuthMeth] section 7)
or when using SASL authentication ([AuthMeth] section 4.3). Server
behavior is undefined when the name is a null value, simple
authentication is used, and a password is specified. The server
SHOULD NOT perform any alias dereferencing in determining the
object to bind as.
- authentication: information used to authenticate the name, if any,
provided in the Bind Request. This type is extensible as defined
in Section 3.6 of [LDAPIANA]. Servers that do not support a choice
supplied by a client will return authMethodNotSupported in the
result code of the BindResponse.
Authorization is the use of this authentication information when
performing operations. Authorization MAY be affected by factors
outside of the LDAP Bind Request, such as lower layer security
services.
4.2.1. Processing of the Bind Request
Upon receipt of a BindRequest, the server MUST ensure there are no
outstanding operations in progress on the connection (This simplifies
server implementation). The server then proceeds to authenticate the
client in either a single-step, or multi-step bind process. Each step
requires the server to return a BindResponse to indicate the status
of authentication.
If the client did not bind before sending a request and receives an
operationsError, it may then send a Bind Request. If this also fails
or the client chooses not to bind on the existing connection, it may
close the connection, reopen it and begin again by first sending a
PDU with a Bind Request. This will aid in interoperating with servers
implementing other versions of LDAP.
Clients MAY send multiple Bind Requests on a connection to change
their credentials. Authentication from earlier binds is subsequently
ignored. A failed or abandoned Bind Operation has the effect of
leaving the connection in an anonymous state. To arrive at a known
authentication state after abandoning a bind operation, clients may
unbind, rebind, or make use of the BindResponse. If a SASL transfer
encryption or integrity mechanism has been negotiated, and that
mechanism does not support the changing of credentials from one
identity to another, then the client MUST instead establish a new
connection.
For some SASL authentication mechanisms, it may be necessary for the
client to invoke the BindRequest multiple times. This is indicated by
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the server sending a BindResponse with the resultCode set to
saslBindInProgress. This indicates that the server requires the
client to send a new bind request, with the same sasl mechanism, to
continue the authentication process. If at any stage the client
wishes to abort the bind process it MAY unbind and then drop the
underlying connection. Clients MUST NOT invoke operations between two
Bind Requests made as part of a multi-stage bind.
A client may abort a SASL bind negotiation by sending a BindRequest
with a different value in the mechanism field of SaslCredentials, or
an AuthenticationChoice other than sasl.
If the client sends a BindRequest with the sasl mechanism field as an
empty string, the server MUST return a BindResponse with
authMethodNotSupported as the resultCode. This will allow clients to
abort a negotiation if it wishes to try again with the same SASL
mechanism.
4.2.2. Bind Response
The Bind Response is defined as follows.
BindResponse ::= [APPLICATION 1] SEQUENCE {
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
BindResponse consists simply of an indication from the server of the
status of the client's request for authentication.
A successful bind operation is indicated by a BindResponse with a
resultCode set to success (0). Otherwise, an appropriate resultCode
is set in the BindResponse. For bind, the protocolError (2)
resultCode may be used to indicate that the version number supplied
by the client is unsupported.
If the server does not support the client's requested protocol
version, it MUST set the resultCode to protocolError.
If the client receives a BindResponse response where the resultCode
was protocolError, it MUST close the connection as the server will be
unwilling to accept further operations. (This is for compatibility
with earlier versions of LDAP, in which the bind was always the first
operation, and there was no negotiation.)
The serverSaslCreds are used as part of a SASL-defined bind mechanism
to allow the client to authenticate the server to which it is
communicating, or to perform "challenge-response" authentication. If
the client bound with the simple choice, or the SASL mechanism does
not require the server to return information to the client, then this
field is not to be included in the result.
4.3. Unbind Operation
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The function of the Unbind Operation is to terminate a protocol
session. The Unbind Operation is defined as follows:
UnbindRequest ::= [APPLICATION 2] NULL
The Unbind Operation has no response defined. Upon transmission of an
UnbindRequest, a protocol client MUST assume that the protocol
session is terminated. Upon receipt of an UnbindRequest, a protocol
server MUST assume that the requesting client has terminated the
session and that all outstanding requests may be discarded, and MUST
close the connection.
4.4. Unsolicited Notification
An unsolicited notification is an LDAPMessage sent from the server to
the client which is not in response to any LDAPMessage received by
the server. It is used to signal an extraordinary condition in the
server or in the connection between the client and the server. The
notification is of an advisory nature, and the server will not expect
any response to be returned from the client.
The unsolicited notification is structured as an LDAPMessage in which
the messageID is 0 and protocolOp is of the extendedResp form. The
responseName field of the ExtendedResponse is present. The LDAPOID
value MUST be unique for this notification, and not be used in any
other situation.
One unsolicited notification (Notice of Disconnection) is defined in
this document.
4.4.1. Notice of Disconnection
This notification may be used by the server to advise the client that
the server is about to close the connection due to an error
condition. Note that this notification is NOT a response to an unbind
requested by the client: the server MUST follow the procedures of
section 4.3. This notification is intended to assist clients in
distinguishing between an error condition and a transient network
failure. As with a connection close due to network failure, the
client MUST NOT assume that any outstanding requests which modified
the directory have succeeded or failed.
The responseName is 1.3.6.1.4.1.1466.20036, the response field is
absent, and the resultCode is used to indicate the reason for the
disconnection.
The following resultCode values are to be used in this notification:
- protocolError: The server has received data from the client in
which the LDAPMessage structure could not be parsed.
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- strongAuthRequired: The server has detected that an established
underlying security association protecting communication between
the client and server has unexpectedly failed or been compromised.
- unavailable: This server will stop accepting new connections and
operations on all existing connections, and be unavailable for an
extended period of time. The client may make use of an alternative
server.
After sending this notice, the server MUST close the connection.
After receiving this notice, the client MUST NOT transmit any further
on the connection, and may abruptly close the connection.
4.5. Search Operation
The Search Operation allows a client to request that a search be
performed on its behalf by a server. This can be used to read
attributes from a single entry, from entries immediately below a
particular entry, or a whole subtree of entries.
4.5.1. Search Request
The Search Request is defined as follows:
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and [0] SET SIZE (1..MAX) OF Filter,
or [1] SET SIZE (1..MAX) OF Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
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SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- at least one must be present,
-- initial and final can occur at most once
substrings SEQUENCE OF CHOICE {
initial [0] AssertionValue,
any [1] AssertionValue,
final [2] AssertionValue } }
MatchingRuleAssertion ::= SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type [2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
Parameters of the Search Request are:
- baseObject: An LDAPDN that is the base object entry relative to
which the search is to be performed.
- scope: An indicator of the scope of the search to be performed.
The semantics of the possible values of this field are identical
to the semantics of the scope field in the X.511 Search Operation.
- derefAliases: An indicator as to how alias objects (as defined in
X.501) are to be handled in searching. The semantics of the
possible values of this field are:
neverDerefAliases: do not dereference aliases in searching
or in locating the base object of the search;
derefInSearching: dereference aliases in subordinates of
the base object in searching, but not in locating the base
object of the search;
derefFindingBaseObj: dereference aliases in locating the
base object of the search, but not when searching
subordinates of the base object;
derefAlways: dereference aliases both in searching and in
locating the base object of the search.
- sizeLimit: A size limit that restricts the maximum number of
entries to be returned as a result of the search. A value of 0 in
this field indicates that no client-requested size limit
restrictions are in effect for the search. Servers may enforce a
maximum number of entries to return.
- timeLimit: A time limit that restricts the maximum time (in
seconds) allowed for a search. A value of 0 in this field
indicates that no client-requested time limit restrictions are in
effect for the search.
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- typesOnly: An indicator as to whether search results will contain
both attribute descriptions and values, or just attribute
descriptions. Setting this field to TRUE causes only attribute
descriptions (no values) to be returned. Setting this field to
FALSE causes both attribute descriptions and values to be
returned.
- filter: A filter that defines the conditions that must be
fulfilled in order for the search to match a given entry.
The 'and', 'or' and 'not' choices can be used to form combinations
of filters. At least one filter element MUST be present in an
'and' or 'or' choice. The others match against individual
attribute values of entries in the scope of the search.
(Implementor's note: the 'not' filter is an example of a tagged
choice in an implicitly-tagged module. In BER this is treated as
if the tag was explicit.)
A server MUST evaluate filters according to the three-valued logic
of X.511 (1993) section 7.8.1. In summary, a filter is evaluated
to either "TRUE", "FALSE" or "Undefined". If the filter evaluates
to TRUE for a particular entry, then the attributes of that entry
are returned as part of the search result (subject to any
applicable access control restrictions). If the filter evaluates
to FALSE or Undefined, then the entry is ignored for the search.
A filter of the "and" choice is TRUE if all the filters in the SET
OF evaluate to TRUE, FALSE if at least one filter is FALSE, and
otherwise Undefined. A filter of the "or" choice is FALSE if all
of the filters in the SET OF evaluate to FALSE, TRUE if at least
one filter is TRUE, and Undefined otherwise. A filter of the "not"
choice is TRUE if the filter being negated is FALSE, FALSE if it
is TRUE, and Undefined if it is Undefined.
The present match evaluates to TRUE where there is an attribute or
subtype of the specified attribute description present in an
entry, and FALSE otherwise (including a presence test with an
unrecognized attribute description.)
The matching rule for equalityMatch filter items is defined by the
EQUALITY matching rule for the attribute type.
The matching rule and assertion syntax for AssertionValues in a
substrings filter item is defined by the SUBSTR matching rule for
the attribute type.
The matching rule for greaterOrEqual and lessOrEqual filter items
is defined by the ORDERING matching rule for the attribute type.
The matching rule for approxMatch filter items is implementation-
defined. If approximate matching is not supported by the server,
the filter item should be treated as an equalityMatch.
The extensibleMatch is new in this version of LDAP. If the
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matchingRule field is absent, the type field MUST be present, and
the equality match is performed for that type. If the type field
is absent and matchingRule is present, the matchValue is compared
against all attributes in an entry which support that
matchingRule, and the matchingRule determines the syntax for the
assertion value (the filter item evaluates to TRUE if it matches
with at least one attribute in the entry, FALSE if it does not
match any attribute in the entry, and Undefined if the
matchingRule is not recognized or the assertionValue cannot be
parsed.) If the type field is present and matchingRule is present,
the matchingRule MUST be one permitted for use with that type,
otherwise the filter item is undefined. If the dnAttributes field
is set to TRUE, the match is applied against all the
AttributeValueAssertions in an entry's distinguished name as well,
and also evaluates to TRUE if there is at least one attribute in
the distinguished name for which the filter item evaluates to
TRUE. (Editors note: The dnAttributes field is present so that
there does not need to be multiple versions of generic matching
rules such as for word matching, one to apply to entries and
another to apply to entries and dn attributes as well).
A filter item evaluates to Undefined when the server would not be
able to determine whether the assertion value matches an entry. If
an attribute description in an equalityMatch, substrings,
greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch filter
is not recognized by the server, a matching rule id in the
extensibleMatch is not recognized by the server, the assertion
value cannot be parsed, or the type of filtering requested is not
implemented, then the filter is Undefined. Thus for example if a
server did not recognize the attribute type shoeSize, a filter of
(shoeSize=*) would evaluate to FALSE, and the filters
(shoeSize=12), (shoeSize>=12) and (shoeSize<=12) would evaluate to
Undefined.
Servers MUST NOT return errors if attribute descriptions or
matching rule ids are not recognized, or assertion values cannot
be parsed. More details of filter processing are given in section
7.8 of [X.511].
- attributes: A list of the attributes to be returned from each
entry which matches the search filter. There are two special
values which may be used: an empty list with no attributes, and
the attribute description string "*". Both of these signify that
all user attributes are to be returned. (The "*" allows the client
to request all user attributes in addition to any specified
operational attributes).
Attributes MUST be named at most once in the list, and are
returned at most once in an entry. If there are attribute
descriptions in the list which are not recognized, they are
ignored by the server.
If the client does not want any attributes returned, it can
specify a list containing only the attribute with OID "1.1". This
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OID was chosen arbitrarily and does not correspond to any
attribute in use.
Client implementors should note that even if all user attributes
are requested, some attributes of the entry may not be included in
search results due to access controls or other restrictions.
Furthermore, servers will not return operational attributes, such
as objectClasses or attributeTypes, unless they are listed by
name, since there may be extremely large number of values for
certain operational attributes. (A list of operational attributes
for use in LDAP is given in [Syntaxes].)
Note that an X.500 "list"-like operation can be emulated by the
client requesting a one-level LDAP search operation with a filter
checking for the presence of the objectClass attribute, and that an
X.500 "read"-like operation can be emulated by a base object LDAP
search operation with the same filter. A server which provides a
gateway to X.500 is not required to use the Read or List operations,
although it may choose to do so, and if it does, it must provide the
same semantics as the X.500 search operation.
4.5.2. Search Result
The results of the search attempted by the server upon receipt of a
Search Request are returned in Search Responses, which are LDAP
messages containing either SearchResultEntry, SearchResultReference,
or SearchResultDone data types.
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
-- implementors should note that the PartialAttributeList may
-- have zero elements (if none of the attributes of that entry
-- were requested, or could be returned), and that the vals set
-- may also have zero elements (if types only was requested, or
-- all values were excluded from the result.)
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
-- at least one LDAPURL element must be present
SearchResultDone ::= [APPLICATION 5] LDAPResult
Upon receipt of a Search Request, a server will perform the necessary
search of the DIT.
If the LDAP session is operating over a connection-oriented transport
such as TCP, the server will return to the client a sequence of
responses in separate LDAP messages. There may be zero or more
responses containing SearchResultEntry, one for each entry found
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during the search. There may also be zero or more responses
containing SearchResultReference, one for each area not explored by
this server during the search. The SearchResultEntry and
SearchResultReference PDUs may come in any order. Following all the
SearchResultReference responses and all SearchResultEntry responses
to be returned by the server, the server will return a response
containing the SearchResultDone, which contains an indication of
success, or detailing any errors that have occurred.
Each entry returned in a SearchResultEntry will contain all
appropriate attributes as specified in the attributes field of the
Search Request. Return of attributes is subject to access control and
other administrative policy.
Some attributes may be constructed by the server and appear in a
SearchResultEntry attribute list, although they are not stored
attributes of an entry. Clients SHOULD NOT assume that all attributes
can be modified, even if permitted by access control.
If the server's schema defines a textual name for an attribute type,
it MUST use a textual name for attributes of that attribute type by
specifying one of the textual names as the value of the attribute
type. Otherwise, the server uses the object identifier for the
attribute type by specifying the object identifier, in ldapOID form,
as the value of attribute type.
4.5.3. Continuation References in the Search Result
If the server was able to locate the entry referred to by the
baseObject but was unable to search all the entries in the scope at
and under the baseObject, the server may return one or more
SearchResultReference entries, each containing a reference to another
set of servers for continuing the operation. A server MUST NOT return
any SearchResultReference if it has not located the baseObject and
thus has not searched any entries; in this case it would return a
SearchResultDone containing a referral resultCode.
If a server holds a copy or partial copy of the subordinate naming
context, it may use the search filter to determine whether or not to
return a SearchResultReference response. Otherwise
SearchResultReference responses are always returned when in scope.
The SearchResultReference is of the same data type as the Referral.
URLs for servers implementing the LDAP protocol are written according
to [LDAPURL]. The <dn> part MUST be present in the URL, with the new
target object name. The client MUST use this name in its next
request. Some servers (e.g. part of a distributed index exchange
system) may provide a different filter in the URLs of the
SearchResultReference. If the filter part of the URL is present in an
LDAP URL, the client MUST use the new filter in its next request to
progress the search, and if the filter part is absent the client will
use again the same filter. If the originating search scope was
singleLevel, the scope part of the URL will be baseObject. Other
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aspects of the new search request may be the same or different as the
search which generated the continuation references.
Other kinds of URLs may be returned so long as the operation could be
performed using that protocol.
The name of an unexplored subtree in a SearchResultReference need not
be subordinate to the base object.
In order to complete the search, the client MUST issue a new search
operation for each SearchResultReference that is returned. Note that
the abandon operation described in section 4.11 applies only to a
particular operation sent on a connection between a client and
server, and if the client has multiple outstanding search operations,
it MUST abandon each operation individually.
4.5.3.1. Example
For example, suppose the contacted server (hosta) holds the entry
"DC=Example,DC=NET" and the entry "CN=Manager,DC=Example,DC=NET". It
knows that either LDAP-capable servers (hostb) or (hostc) hold
"OU=People,DC=Example,DC=NET" (one is the master and the other server
a shadow), and that LDAP-capable server (hostd) holds the subtree
"OU=Roles,DC=Example,DC=NET". If a subtree search of
"DC=Example,DC=NET" is requested to the contacted server, it may
return the following:
SearchResultEntry for DC=Example,DC=NET
SearchResultEntry for CN=Manager,DC=Example,DC=NET
SearchResultReference {
ldap://hostb/OU=People,DC=Example,DC=NET
ldap://hostc/OU=People,DC=Example,DC=NET
}
SearchResultReference {
ldap://hostd/OU=Roles,DC=Example,DC=NET
}
SearchResultDone (success)
Client implementors should note that when following a
SearchResultReference, additional SearchResultReference may be
generated. Continuing the example, if the client contacted the server
(hostb) and issued the search for the subtree
"OU=People,DC=Example,DC=NET", the server might respond as follows:
SearchResultEntry for OU=People,DC=Example,DC=NET
SearchResultReference {
ldap://hoste/OU=Managers,OU=People,DC=Example,DC=NET
}
SearchResultReference {
ldap://hostf/OU=Consultants,OU=People,DC=Example,DC=NET
}
SearchResultDone (success)
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If the contacted server does not hold the base object for the search,
then it will return a referral to the client. For example, if the
client requests a subtree search of "DC=Example,DC=ORG" to hosta, the
server may return only a SearchResultDone containing a referral.
SearchResultDone (referral) {
ldap://hostg/DC=Example,DC=ORG??sub
}
4.6. Modify Operation
The Modify Operation allows a client to request that a modification
of an entry be performed on its behalf by a server. The Modify
Request is defined as follows:
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Modify Request are:
- object: The object to be modified. The value of this field
contains the DN of the entry to be modified. The server will not
perform any alias dereferencing in determining the object to be
modified.
- modification: A list of modifications to be performed on the
entry. The entire list of entry modifications MUST be performed in
the order they are listed, as a single atomic operation. While
individual modifications may violate the directory schema, the
resulting entry after the entire list of modifications is
performed MUST conform to the requirements of the directory
schema. The values that may be taken on by the 'operation' field
in each modification construct have the following semantics
respectively:
add: add values listed to the given attribute, creating the
attribute if necessary;
delete: delete values listed from the given attribute,
removing the entire attribute if no values are listed, or
if all current values of the attribute are listed for
deletion;
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replace: replace all existing values of the given attribute
with the new values listed, creating the attribute if it
did not already exist. A replace with no value will delete
the entire attribute if it exists, and is ignored if the
attribute does not exist.
The result of the modification attempted by the server upon receipt
of a Modify Request is returned in a Modify Response, defined as
follows:
ModifyResponse ::= [APPLICATION 7] LDAPResult
Upon receipt of a Modify Request, a server will perform the necessary
modifications to the DIT.
The server will return to the client a single Modify Response
indicating either the successful completion of the DIT modification,
or the reason that the modification failed. Note that due to the
requirement for atomicity in applying the list of modifications in
the Modify Request, the client may expect that no modifications of
the DIT have been performed if the Modify Response received indicates
any sort of error, and that all requested modifications have been
performed if the Modify Response indicates successful completion of
the Modify Operation. If the connection fails, whether the
modification occurred or not is indeterminate.
The Modify Operation cannot be used to remove from an entry any of
its distinguished values, those values which form the entry's
relative distinguished name. An attempt to do so will result in the
server returning the error notAllowedOnRDN. The Modify DN Operation
described in section 4.9 is used to rename an entry.
Note that due to the simplifications made in LDAP, there is not a
direct mapping of the modifications in an LDAP ModifyRequest onto the
EntryModifications of a DAP ModifyEntry operation, and different
implementations of LDAP-DAP gateways may use different means of
representing the change. If successful, the final effect of the
operations on the entry MUST be identical.
4.7. Add Operation
The Add Operation allows a client to request the addition of an entry
into the directory. The Add Request is defined as follows:
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Add Request are:
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- entry: the Distinguished Name of the entry to be added. Note that
the server will not dereference any aliases in locating the entry
to be added.
- attributes: the list of attributes that make up the content of the
entry being added. Clients MUST include distinguished values
(those forming the entry's own RDN) in this list, the objectClass
attribute, and values of any mandatory attributes of the listed
object classes. Clients MUST NOT supply NO-USER-MODIFICATION
attributes such as the createTimestamp or creatorsName attributes,
since the server maintains these automatically.
The entry named in the entry field of the AddRequest MUST NOT exist
for the AddRequest to succeed. The parent of the object and alias
entries to be added MUST exist. For example, if the client attempted
to add "CN=JS,DC=Example,DC=NET", the "DC=Example,DC=NET" entry did
not exist, and the "DC=NET" entry did exist, then the server would
return the error noSuchObject with the matchedDN field containing
"DC=NET". If the parent entry exists but is not in a naming context
held by the server, the server SHOULD return a referral to the server
holding the parent entry.
Server implementations SHOULD NOT restrict where entries can be
located in the directory unless DIT structure rules are in place.
Some servers MAY allow the administrator to restrict the classes of
entries which can be added to the directory.
Upon receipt of an Add Request, a server will attempt to add the
requested entry. The result of the add attempt will be returned to
the client in the Add Response, defined as follows:
AddResponse ::= [APPLICATION 9] LDAPResult
A response of success indicates that the new entry is present in the
directory.
4.8. Delete Operation
The Delete Operation allows a client to request the removal of an
entry from the directory. The Delete Request is defined as follows:
DelRequest ::= [APPLICATION 10] LDAPDN
The Delete Request consists of the Distinguished Name of the entry to
be deleted. Note that the server will not dereference aliases while
resolving the name of the target entry to be removed, and that only
leaf entries (those with no subordinate entries) can be deleted with
this operation.
The result of the delete attempted by the server upon receipt of a
Delete Request is returned in the Delete Response, defined as
follows:
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DelResponse ::= [APPLICATION 11] LDAPResult
Upon receipt of a Delete Request, a server will attempt to perform
the entry removal requested. The result of the delete attempt will be
returned to the client in the Delete Response.
4.9. Modify DN Operation
The Modify DN Operation allows a client to change the leftmost (least
significant) component of the name of an entry in the directory,
and/or to move a subtree of entries to a new location in the
directory. The Modify DN Request is defined as follows:
ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
Parameters of the Modify DN Request are:
- entry: the Distinguished Name of the entry to be changed. This
entry may or may not have subordinate entries. Note that the
server will not dereference any aliases in locating the entry to
be changed.
- newrdn: the RDN that will form the leftmost component of the new
name of the entry.
- deleteoldrdn: a boolean parameter that controls whether the old
RDN attribute values are to be retained as attributes of the
entry, or deleted from the entry.
- newSuperior: if present, this is the Distinguished Name of an
existing object entry which becomes the immediate superior of the
existing entry.
The result of the name change attempted by the server upon receipt of
a Modify DN Request is returned in the Modify DN Response, defined as
follows:
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
Upon receipt of a ModifyDNRequest, a server will attempt to perform
the name change. The result of the name change attempt will be
returned to the client in the Modify DN Response.
For example, if the entry named in the "entry" parameter was "cn=John
Smith,c=US", the newrdn parameter was "cn=John Cougar Smith", and the
newSuperior parameter was absent, then this operation would attempt
to rename the entry to be "cn=John Cougar Smith,c=US". If there was
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already an entry with that name, the operation would fail with error
code entryAlreadyExists.
If the deleteoldrdn parameter is TRUE, the values forming the old RDN
are deleted from the entry. If the deleteoldrdn parameter is FALSE,
the values forming the old RDN will be retained as non-distinguished
attribute values of the entry. The server may not perform the
operation and return an error code if the setting of the deleteoldrdn
parameter would cause a schema inconsistency in the entry.
Note that X.500 restricts the ModifyDN operation to only affect
entries that are contained within a single server. If the LDAP server
is mapped onto DAP, then this restriction will apply, and the
resultCode affectsMultipleDSAs will be returned if this error
occurred. In general clients MUST NOT expect to be able to perform
arbitrary movements of entries and subtrees between servers.
4.10. Compare Operation
The Compare Operation allows a client to compare an assertion
provided with an entry in the directory. The Compare Request is
defined as follows:
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
Parameters of the Compare Request are:
- entry: the name of the entry to be compared with. Note that the
server SHOULD NOT dereference any aliases in locating the entry to
be compared with.
- ava: the assertion with which an attribute in the entry is to be
compared.
The result of the compare attempted by the server upon receipt of a
Compare Request is returned in the Compare Response, defined as
follows:
CompareResponse ::= [APPLICATION 15] LDAPResult
Upon receipt of a Compare Request, a server will attempt to perform
the requested comparison using the EQUALITY matching rule for the
attribute type. The result of the comparison will be returned to the
client in the Compare Response. Note that errors and the result of
comparison are all returned in the same construct.
Note that some directory systems may establish access controls which
permit the values of certain attributes (such as userPassword) to be
compared but not interrogated by other means.
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4.11. Abandon Operation
The function of the Abandon Operation is to allow a client to request
that the server abandon an outstanding operation. The Abandon Request
is defined as follows:
AbandonRequest ::= [APPLICATION 16] MessageID
The MessageID MUST be that of an operation which was requested
earlier in this connection. The abandon request itself has its own
message id. This is distinct from the id of the earlier operation
being abandoned.
There is no response defined in the Abandon Operation. Upon
transmission of an Abandon Operation, the server MAY abandon the
operation identified by the Message ID in the Abandon Request.
Operation responses are not sent for successfully abandoned
operations. Clients can determine that an operation has been
abandoned by performing a subsequent bind operation.
Abandon and Unbind operations cannot be abandoned. The ability to
abandon other (particularly update) operations is at the discretion
of the server.
In the event that a server receives an Abandon Request on a Search
Operation in the midst of transmitting responses to the search, that
server MUST cease transmitting entry responses to the abandoned
request immediately, and MUST NOT send the SearchResponseDone. Of
course, the server MUST ensure that only properly encoded LDAPMessage
PDUs are transmitted.
Clients MUST NOT send abandon requests for the same operation
multiple times, and MUST also be prepared to receive results from
operations it has abandoned (since these may have been in transit
when the abandon was requested, or are not able to be abandoned).
Servers MUST discard abandon requests for message IDs they do not
recognize, for operations which cannot be abandoned, and for
operations which have already been abandoned.
4.12. Extended Operation
An extension mechanism has been added in this version of LDAP, in
order to allow additional operations to be defined for services not
available elsewhere in this protocol, for instance digitally signed
operations and results.
The extended operation allows clients to make requests and receive
responses with predefined syntaxes and semantics. These may be
defined in RFCs or be private to particular implementations. Each
request MUST have a unique OBJECT IDENTIFIER assigned to it.
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
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requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
The requestName is a dotted-decimal representation of the OBJECT
IDENTIFIER corresponding to the request. The requestValue is
information in a form defined by that request, encapsulated inside an
OCTET STRING.
The server will respond to this with an LDAPMessage containing the
ExtendedResponse.
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
If the server does not recognize the request name, it MUST return
only the response fields from LDAPResult, containing the
protocolError result code.
4.13. Start TLS Operation
The Start Transport Layer Security (StartTLS) operation provides the
ability to establish Transport Layer Security [RFC2246] on an LDAP
connection.
4.13.1. Start TLS Request
A client requests TLS establishment by transmitting a Start TLS
request PDU to the server. The Start TLS request is defined in terms
of an ExtendedRequest. The requestName is "1.3.6.1.4.1.1466.20037",
and the requestValue field is absent.
The client MUST NOT send any PDUs on this connection following this
request until it receives a Start TLS extended response.
4.13.2. Start TLS Response
When a Start TLS request is made, servers supporting the operation
MUST return a Start TLS response PDU to the requestor. The Start TLS
response responseName is also "1.3.6.1.4.1.1466.20037", and the
response field is absent.
The server MUST set the resultCode field to either success or one of
the other values outlined in section 4.13.2.2.
4.13.2.1. "Success" Response
If the Start TLS Response contains a resultCode of success, this
indicates that the server is willing and able to negotiate TLS. Refer
to section 5.3 of [AuthMeth] for details.
4.13.2.2. Response other than "success"
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If the ExtendedResponse contains a resultCode other than success,
this indicates that the server is unwilling or unable to negotiate
TLS.
If the Start TLS extended request was not successful, the resultCode
will be one of:
operationsError (operations sequencing incorrect; e.g. TLS already
established)
protocolError (TLS not supported or incorrect PDU structure)
referral (this server doesn't do TLS, try this one)
unavailable (e.g. some major problem with TLS, or server is
shutting down)
The server MUST return operationsError if the client violates any of
the Start TLS extended operation sequencing requirements described in
section 5.3 of [AuthMeth].
If the server does not support TLS (whether by design or by current
configuration), it MUST set the resultCode to protocolError, or to
referral. The server MUST include an actual referral value in the
LDAP Result if it returns a resultCode of referral. The client's
current session is unaffected if the server does not support TLS. The
client MAY proceed with any LDAP operation, or it MAY close the
connection.
The server MUST return unavailable if it supports TLS but cannot
establish a TLS connection for some reason, e.g. the certificate
server not responding, it cannot contact its TLS implementation, or
if the server is in process of shutting down. The client MAY retry
the StartTLS operation, or it MAY proceed with any other LDAP
operation, or it MAY close the connection.
4.13.3. Closing a TLS Connection
Two forms of TLS connection closure--graceful and abrupt--are
supported.
4.13.3.1. Graceful Closure
Either the client or server MAY terminate the TLS connection and
leave the LDAP session intact by sending a TLS closure alert.
Before sending a TLS closure alert, the client MUST either wait for
any outstanding LDAP operations to complete, or explicitly abandon
them.
After the initiator of a close has sent a TLS closure alert, it MUST
discard any TLS messages until it has received a TLS closure alert
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from the other party. It will cease to send TLS Record Protocol
PDUs, and following the receipt of the alert, MAY send and receive
LDAP PDUs.
The other party, if it receives a TLS closure alert, MUST immediately
transmit a TLS closure alert. It will subsequently cease to send TLS
Record Protocol PDUs, and MAY send and receive LDAP PDUs.
4.13.3.2. Abrupt Closure
Either the client or server MAY abruptly close the TLS connection by
dropping the underlying transfer protocol connection. In this
circumstance, a server MAY send the client a Notice of Disconnection
before dropping the underlying connection.
5. Protocol Element Encodings and Transfer
One underlying service is defined here. Clients and servers SHOULD
implement the mapping of LDAP over TCP described in 5.2.1.
5.1. Protocol Encoding
The protocol elements of LDAP are encoded for exchange using the
Basic Encoding Rules (BER) [X.690] of ASN.1 [X.680]. However, due to
the high overhead involved in using certain elements of the BER, the
following additional restrictions are placed on BER-encodings of LDAP
protocol elements:
(1) Only the definite form of length encoding will be used.
(2) OCTET STRING values will be encoded in the primitive form only.
(3) If the value of a BOOLEAN type is true, the encoding MUST have
its contents octets set to hex "FF".
(4) If a value of a type is its default value, it MUST be absent.
Only some BOOLEAN and INTEGER types have default values in this
protocol definition.
These restrictions do not apply to ASN.1 types encapsulated inside of
OCTET STRING values, such as attribute values, unless otherwise
noted.
5.2. Transfer Protocols
This protocol is designed to run over connection-oriented, reliable
transports, with all 8 bits in an octet being significant in the data
stream.
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5.2.1. Transmission Control Protocol (TCP)
The encoded LDAPMessage PDUs are mapped directly onto the TCP
bytestream using the BER-based encoding described in section 5.1. It
is recommended that server implementations running over the TCP
provide a protocol listener on the assigned port, 389. Servers may
instead provide a listener on a different port number. Clients MUST
support contacting servers on any valid TCP port.
6. Implementation Guidelines
6.1. Server Implementations
The server MUST be capable of recognizing all the mandatory attribute
type names and implement the syntaxes specified in [Syntaxes].
Servers MAY also recognize additional attribute type names.
6.2. Client Implementations
Clients that follow referrals or search continuation references MUST
ensure that they do not loop between servers. They MUST NOT
repeatedly contact the same server for the same request with the same
target entry name, scope and filter. Some clients use a counter that
is incremented each time referral handling occurs for an operation,
and these kinds of clients MUST be able to handle a DIT with at least
ten layers of naming contexts between the root and a leaf entry.
In the absence of prior agreements with servers, clients SHOULD NOT
assume that servers support any particular schemas beyond those
referenced in section 6.1. Different schemas can have different
attribute types with the same names. The client can retrieve the
subschema entries referenced by the subschemaSubentry attribute in
the entries held by the server.
7. Security Considerations
When used with a connection-oriented transport, this version of the
protocol provides facilities for simple authentication using a
cleartext password, as well as any SASL mechanism [RFC2222]. SASL
allows for integrity and privacy services to be negotiated.
It is also permitted that the server can return its credentials to
the client, if it chooses to do so.
Use of cleartext password is strongly discouraged where the
underlying transport service cannot guarantee confidentiality and may
result in disclosure of the password to unauthorized parties.
When used with SASL, it should be noted that the name field of the
BindRequest is not protected against modification. Thus if the
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distinguished name of the client (an LDAPDN) is agreed through the
negotiation of the credentials, it takes precedence over any value in
the unprotected name field.
Implementations which cache attributes and entries obtained via LDAP
MUST ensure that access controls are maintained if that information
is to be provided to multiple clients, since servers may have access
control policies which prevent the return of entries or attributes in
search results except to particular authenticated clients. For
example, caches could serve result information only to the client
whose request caused it to be in the cache.
Protocol servers may return referrals which redirect protocol clients
to peer servers. It is possible for a rogue application to inject
such referrals into the data stream in an attempt to redirect a
client to a rogue server. Protocol clients are advised to be aware of
this, and possibly reject referrals when confidentiality measures are
in place. Protocol clients are advised to ignore referrals from the
Start TLS operation.
8. Acknowledgements
This document is an update to RFC 2251, by Mark Wahl, Tim Howes, and
Steve Kille. Their work along with the input of individuals of the
IETF LDAPEXT, LDUP, LDAPBIS, and other Working Groups is gratefully
acknowledged.
9. Normative References
[X.500] ITU-T Rec. X.500, "The Directory: Overview of Concepts,
Models and Service", 1993.
[Roadmap] K. Zeilenga (editor), "LDAP: Technical Specification Road
Map", draft-ietf-ldapbis-roadmap-xx.txt (a work in
progress).
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[X.680] ITU-T Recommendation X.680 (1997) | ISO/IEC 8824-1:1998
Information Technology - Abstract Syntax Notation One
(ASN.1): Specification of basic notation
[X.690] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules:
Basic, Canonical, and Distinguished Encoding Rules", 1994.
[LDAPIANA] K. Zeilenga, "IANA Considerations for LDAP", draft-ietf-
ldapbis-xx.txt (a work in progress).
[ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
Architecture and Basic Multilingual Plane, ISO/IEC 10646-1
: 1993.
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[RFC2279] Yergeau, F., "UTF-8, a transformation format of Unicode
and ISO 10646", RFC 2279, January 1998.
[Models] K. Zeilenga, "LDAP: The Models", draft-ietf-ldapbis-
models-xx.txt (a work in progress).
[LDAPDN] K. Zeilenga (editor), "LDAP: String Representation of
Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, (a
work in progress).
[Syntaxes] K. Dally (editor), "LDAP: Syntaxes", draft-ietf-ldapbis-
syntaxes-xx.txt, (a work in progress).
[X.501] ITU-T Rec. X.501, "The Directory: Models", 1993.
[X.511] ITU-T Rec. X.511, "The Directory: Abstract Service
Definition", 1993.
[RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[AuthMeth] R. Harrison (editor), "LDAP: Authentication Methods",
draft-ietf-ldapbis-authmeth-xx.txt, (a work in progress).
[RFC2222] Meyers, J., "Simple Authentication and Security Layer",
RFC 2222, October 1997.
10. Editor's Address
Jim Sermersheim
Novell, Inc.
1800 South Novell Place
Provo, Utah 84606, USA
jimse@novell.com
+1 801 861-3088
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Appendix A - LDAP Result Codes
This normative appendix details additional considerations regarding
LDAP result codes and provides a brief, general description of each
LDAP result code enumerated in Section 4.1.10.
Additional result codes MAY be defined for use with extensions.
Client implementations SHALL treat any result code which they do not
recognize as an unknown error condition.
A.1 Non-Error Result Codes
These result codes (called "non-error" result codes) do not indicate
an error condition:
success(0),
compareTrue(6),
compareFalse(7),
referral(10), and
saslBindInProgress(14).
The success(0), compareTrue(6), and compare(7) result codes indicate
successful completion (and, hence, are called to as "successful"
result codes).
The referral(10) and saslBindInProgress(14) indicate the client is
required to take additional action to complete the operation
A.2 Error Result Codes
A.3 Classes and Precedence of Error Result Codes
Result codes that indicate error conditions (and, hence, are called
"error" result codes) fall into 6 classes. The following list
specifies the precedence of error classes to be used when more than
one error is detected [X511]:
1) Name Errors (codes 32 - 34, 36)
- a problem related to a name (DN or RDN),
2) Update Errors (codes 64 - 69, 71)
- a problem related to an update operation,
3) Attribute Errors (codes 16 - 21)
- a problem related to a supplied attribute,
4) Security Errors (codes 8, 13, 48 - 50)
- a security related problem,
5) Service Problem (codes 3, 4, 7, 11, 12, 51 - 54, 80)
- a problem related to the provision of the service, and
6) Protocol Problem (codes 1, 2)
- a problem related to protocol structure or semantics.
If the server detects multiple errors simultaneously, the server
SHOULD report the error with the highest precedence.
Existing LDAP result codes are described as follows:
success (0)
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Indicates successful completion of an operation.
This result code is normally not returned by the compare
operation, see compareFalse (5) and compareTrue (6). It is
possible that a future extension mechanism would allow this
to be returned by a compare operation.
operationsError (1)
Indicates that the operation is not properly sequenced with
relation to other operations (of same or different type).
For example, this code is returned if the client attempts to
Start TLS [RFC2246] while there are other operations
outstanding or if TLS was already established.
protocolError (2)
Indicates the server received data which has incorrect
structure.
For bind operation only, the code may be resulted to indicate
the server does not support the requested protocol version.
timeLimitExceeded (3)
Indicates that the time limit specified by the client was
exceeded before the operation could be completed.
sizeLimitExceeded (4)
Indicates that the size limit specified by the client was
exceeded before the operation could be completed.
compareFalse (5)
Indicates that the operation successfully completes and the
assertion has evaluated to FALSE.
This result code is normally only returned by the compare
operation.
compareTrue (6)
Indicates that the operation successfully completes and the
assertion has evaluated to TRUE.
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This result code is normally only returned by the compare
operation.
authMethodNotSupported (7)
Indicates that the authentication method or mechanism is not
supported.
strongAuthRequired (8)
Except when returned in a Notice of Disconnect (see section
4.4.1), this indicates that the server requires the client to
authentication using a strong(er) mechanism.
referral (10)
Indicates that a referral needs to be chased to complete the
operation (see section 4.1.11).
adminLimitExceeded (11)
Indicates that an administrative limit has been exceeded.
unavailableCriticalExtension (12)
Indicates that server cannot perform a critical extension
(see section 4.1.12).
confidentialityRequired (13)
Indicates that data confidentiality protections are required.
saslBindInProgress (14)
Indicates the server requires the client to send a new bind
request, with the same SASL mechanism, to continue the
authentication process (see section 4.2).
noSuchAttribute (16)
Indicates that the named entry does not contain the specified
attribute or attribute value.
undefinedAttributeType (17)
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Indicates that a request field contains an undefined
attribute type.
inappropriateMatching (18)
Indicates that a request cannot be completed due to an
inappropriate matching.
constraintViolation (19)
Indicates that the client supplied an attribute value which
does not conform to constraints placed upon it by the data
model.
For example, this code is returned when the multiple values
are supplied to an attribute which has a SINGLE-VALUE
constraint.
attributeOrValueExists (20)
Indicates that the client supplied an attribute or value to
be added to an entry already exists.
invalidAttributeSyntax (21)
Indicates that a purported attribute value does not conform
to the syntax of the attribute.
noSuchObject (32)
Indicates that the object does not exist in the DIT.
aliasProblem (33)
Indicates that an alias problem has occurred. Typically an
alias has been dereferenced which names no object.
invalidDNSyntax (34)
Indicates that a LDAPDN or RelativeLDAPDN field (e.g. search
base, target entry, ModifyDN newrdn, etc.) of a request does
not conform to the required syntax or contains attribute
values which do not conform to the syntax of the attribute's
type.
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aliasDereferencingProblem (36)
Indicates that a problem occurred while dereferencing an
alias. Typically an alias was encountered in a situation
where it was not allowed or where access was denied.
inappropriateAuthentication (48)
Indicates the server requires the client which had attempted
to bind anonymously or without supplying credentials to
provide some form of credentials,
invalidCredentials (49)
Indicates the supplied password or SASL credentials are
invalid.
insufficientAccessRights (50)
Indicates that the client does not have sufficient access
rights to perform the operation.
busy (51)
Indicates that the server is busy.
unavailable (52)
Indicates that the server is shutting down or a subsystem
necessary to complete the operation is offline.
unwillingToPerform (53)
Indicates that the server is unwilling to perform the
operation.
loopDetect (54)
Indicates that the server has detected an internal loop.
namingViolation (64)
Indicates that the entry name violates naming restrictions.
objectClassViolation (65)
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Indicates that the entry violates object class restrictions.
notAllowedOnNonLeaf (66)
Indicates that operation is inappropriately acting upon a
non-leaf entry.
notAllowedOnRDN (67)
Indicates that the operation is inappropriately attempting to
remove a value which forms the entry's relative distinguished
name.
entryAlreadyExists (68)
Indicates that the request cannot be added fulfilled as the
entry already exists.
objectClassModsProhibited (69)
Indicates that the attempt to modify the object class(es) of
an entry objectClass attribute is prohibited.
For example, this code is returned when a when a client
attempts to modify the structural object class of an entry.
affectsMultipleDSAs (71)
Indicates that the operation cannot be completed as it
affects multiple servers (DSAs).
other (80)
Indicates the server has encountered an internal error.
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Appendix B - Complete ASN.1 Definition
This appendix is normative.
Lightweight-Directory-Access-Protocol-V3 DEFINITIONS
IMPLICIT TAGS
EXTENSIBILITY IMPLIED ::=
BEGIN
LDAPMessage ::= SEQUENCE {
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse,
... },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
LDAPString ::= OCTET STRING -- UTF-8 encoded,
-- [ISO10646] characters
LDAPOID ::= OCTET STRING -- Constrained to numericoid [Models]
LDAPDN ::= LDAPString
RelativeLDAPDN ::= LDAPString
AttributeDescription ::= LDAPString
-- Constrained to attributedescription
-- [Models]
AttributeDescriptionList ::= SEQUENCE OF
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AttributeDescription
AttributeValue ::= OCTET STRING
AttributeValueAssertion ::= SEQUENCE {
attributeDesc AttributeDescription,
assertionValue AssertionValue }
AssertionValue ::= OCTET STRING
Attribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
MatchingRuleId ::= LDAPString
LDAPResult ::= SEQUENCE {
resultCode ENUMERATED {
success (0),
operationsError (1),
protocolError (2),
timeLimitExceeded (3),
sizeLimitExceeded (4),
compareFalse (5),
compareTrue (6),
authMethodNotSupported (7),
strongAuthRequired (8),
-- 9 reserved --
referral (10),
adminLimitExceeded (11),
unavailableCriticalExtension (12),
confidentialityRequired (13),
saslBindInProgress (14),
noSuchAttribute (16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation (19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
noSuchObject (32),
aliasProblem (33),
invalidDNSyntax (34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
invalidCredentials (49),
insufficientAccessRights (50),
busy (51),
unavailable (52),
unwillingToPerform (53),
loopDetect (54),
-- 55-63 unused --
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namingViolation (64),
objectClassViolation (65),
notAllowedOnNonLeaf (66),
notAllowedOnRDN (67),
entryAlreadyExists (68),
objectClassModsProhibited (69),
-- 70 reserved for CLDAP --
affectsMultipleDSAs (71),
-- 72-79 unused --
other (80),
... },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
diagnosticMessage LDAPString,
referral [3] Referral OPTIONAL }
Referral ::= SEQUENCE OF LDAPURL
LDAPURL ::= LDAPString -- limited to characters permitted in
-- URLs
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType LDAPOID,
criticality BOOLEAN DEFAULT FALSE,
controlValue OCTET STRING OPTIONAL }
BindRequest ::= [APPLICATION 0] SEQUENCE {
version INTEGER (1 .. 127),
name LDAPDN,
authentication AuthenticationChoice }
AuthenticationChoice ::= CHOICE {
simple [0] OCTET STRING,
-- 1 and 2 reserved
sasl [3] SaslCredentials,
... }
SaslCredentials ::= SEQUENCE {
mechanism LDAPString,
credentials OCTET STRING OPTIONAL }
BindResponse ::= [APPLICATION 1] SEQUENCE {
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
UnbindRequest ::= [APPLICATION 2] NULL
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
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wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and [0] SET SIZE (1..MAX) OF Filter,
or [1] SET SIZE (1..MAX) OF Filter,
not [2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE {
type AttributeDescription,
-- at least one must be present,
-- initial and final can occur at most once
substrings SEQUENCE OF CHOICE {
initial [0] AssertionValue,
any [1] AssertionValue,
final [2] AssertionValue } }
MatchingRuleAssertion ::= SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type [2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
SearchResultDone ::= [APPLICATION 5] LDAPResult
ModifyRequest ::= [APPLICATION 6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
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operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
ModifyResponse ::= [APPLICATION 7] LDAPResult
AddRequest ::= [APPLICATION 8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
AddResponse ::= [APPLICATION 9] LDAPResult
DelRequest ::= [APPLICATION 10] LDAPDN
DelResponse ::= [APPLICATION 11] LDAPResult
ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
entry LDAPDN,
newrdn RelativeLDAPDN,
deleteoldrdn BOOLEAN,
newSuperior [0] LDAPDN OPTIONAL }
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
CompareRequest ::= [APPLICATION 14] SEQUENCE {
entry LDAPDN,
ava AttributeValueAssertion }
CompareResponse ::= [APPLICATION 15] LDAPResult
AbandonRequest ::= [APPLICATION 16] MessageID
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
END
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Appendix C - Change History
<Note to RFC editor: This section is to be removed prior to RFC
publication>
C.1 Changes made to RFC 2251:
C.1.1 Editorial
- Bibliography References: Changed all bibliography references to
use a long name form for readability.
- Changed occurrences of "unsupportedCriticalExtension"
"unavailableCriticalExtension"
- Fixed a small number of misspellings (mostly dropped letters).
C.1.2 Section 1
- Removed IESG note.
C.1.3 Section 9
- Added references to RFCs 1823, 2234, 2829 and 2830.
C.2 Changes made to draft-ietf-ldapbis-protocol-00.txt:
C.2.1 Section 4.1.6
- In the first paragraph, clarified what the contents of an
AttributeValue are. There was confusion regarding whether or not
an AttributeValue that is BER encoded (due to the "binary" option)
is to be wrapped in an extra OCTET STRING.
- To the first paragraph, added wording that doesn't restrict other
transfer encoding specifiers from being used. The previous wording
only allowed for the string encoding and the ;binary encoding.
- To the first paragraph, added a statement restricting multiple
options that specify transfer encoding from being present. This
was never specified in the previous version and was seen as a
potential interoperability problem.
- Added a third paragraph stating that the ;binary option is
currently the only option defined that specifies the transfer
encoding. This is for completeness.
C.2.2 Section 4.1.7
- Generalized the second paragraph to read "If an option specifying
the transfer encoding is present in attributeDesc, the
AssertionValue is encoded as specified by the option...".
Previously, only the ;binary option was mentioned.
C.2.3 Sections 4.2, 4.9, 4.10
- Added alias dereferencing specifications. In the case of modDN,
followed precedent set on other update operations (... alias is
not dereferenced...) In the case of bind and compare stated that
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servers SHOULD NOT dereference aliases. Specifications were added
because they were missing from the previous version and caused
interoperability problems. Concessions were made for bind and
compare (neither should have ever allowed alias dereferencing) by
using SHOULD NOT language, due to the behavior of some existing
implementations.
C.2.4 Sections 4.5 and Appendix A
- Changed SubstringFilter.substrings.initial, any, and all from
LDAPString to AssertionValue. This was causing an incompatibility
with X.500 and confusion among other TS RFCs.
C.3 Changes made to draft-ietf-ldapbis-protocol-01.txt:
C.3.1 Section 3.4
- Reworded text surrounding subschemaSubentry to reflect that it is
a single-valued attribute that holds the schema for the root DSE.
Also noted that if the server masters entries that use differing
schema, each entry's subschemaSubentry attribute must be
interrogated. This may change as further fine-tuning is done to
the data model.
C.3.2 Section 4.1.12
- Specified that the criticality field is only used for requests and
not for unbind or abandon. Noted that it is ignored for all other
operations.
C.3.3 Section 4.2
- Noted that Server behavior is undefined when the name is a null
value, simple authentication is used, and a password is specified.
C.3.4 Section 4.2.(various)
- Changed "unauthenticated" to "anonymous" and "DN" and "LDAPDN" to
"name"
C.3.5 Section 4.2.2
- Changed "there is no authentication or encryption being performed
by a lower layer" to "the underlying transport service cannot
guarantee confidentiality"
C.3.6 Section 4.5.2
- Removed all mention of ExtendedResponse due to lack of
implementation.
C.4 Changes made to draft-ietf-ldapbis-protocol-02.txt:
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C.4.1 Section 4
- Removed "typically" from "and is typically transferred" in the
first paragraph. We know of no (and can conceive of no) case where
this isn't true.
- Added "Section 5.1 specifies how the LDAP protocol is encoded." To
the first paragraph. Added this cross reference for readability.
- Changed "version 3 " to "version 3 or later" in the second
paragraph. This was added to clarify the original intent.
- Changed "protocol version" to "protocol versions" in the third
paragraph. This attribute is multi-valued with the intent of
holding all supported versions, not just one.
C.4.2 Section 4.1.8
- Changed "when transferred in protocol" to "when transferred from
the server to the client" in the first paragraph. This is to
clarify that this behavior only happens when attributes are being
sent from the server.
C.4.3 Section 4.1.10
- Changed "servers will return responses containing fields of type
LDAPResult" to "servers will return responses of LDAPResult or
responses containing the components of LDAPResponse". This
statement was incorrect and at odds with the ASN.1. The fix here
reflects the original intent.
- Dropped '--new' from result codes ASN.1. This simplification in
comments just reduces unneeded verbiage.
C.4.4 Section 4.1.11
- Changed "It contains a reference to another server (or set of
servers)" to "It contains one or more references to one or more
servers or services" in the first paragraph. This reflects the
original intent and clarifies that the URL may point to non-LDAP
services.
C.4.5 Section 4.1.12
- Changed "The server MUST be prepared" to "Implementations MUST be
prepared" in the eighth paragraph to reflect that both client and
server implementations must be able to handle this (as both parse
controls).
C.4.6 Section 4.4
- Changed "One unsolicited notification is defined" to "One
unsolicited notification (Notice of Disconnection) is defined" in
the third paragraph. For clarity and readability.
C.4.7 Section 4.5.1
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- Changed "checking for the existence of the objectClass attribute"
to "checking for the presence of the objectClass attribute" in the
last paragraph. This was done as a measure of consistency (we use
the terms present and presence rather than exists and existence in
search filters).
C.4.8 Section 4.5.3
- Changed "outstanding search operations to different servers," to
"outstanding search operations" in the fifth paragraph as they may
be to the same server. This is a point of clarification.
C.4.9 Section 4.6
- Changed "clients MUST NOT attempt to delete" to "clients MUST NOT
attempt to add or delete" in the second to last paragraph.
- Change "using the "delete" form" to "using the "add" or "delete"
form" in the second to last paragraph.
C.4.10 Section 4.7
- Changed "Clients MUST NOT supply the createTimestamp or
creatorsName attributes, since these will be generated
automatically by the server." to "Clients MUST NOT supply NO-USER-
MODIFICATION attributes such as createTimestamp or creatorsName
attributes, since these are provided by the server." in the
definition of the attributes field. This tightens the language to
reflect the original intent and to not leave a hole in which one
could interpret the two attributes mentioned as the only non-
writable attributes.
C.4.11 Section 4.11
- Changed "has been" to "will be" in the fourth paragraph. This
clarifies that the server will (not has) abandon the operation.
C.5 Changes made to draft-ietf-ldapbis-protocol-03.txt:
C.5.1 Section 3.2.1
- Changed "An attribute is a type with one or more associated
values. The attribute type is identified by a short descriptive
name and an OID (object identifier). The attribute type governs
whether there can be more than one value of an attribute of that
type in an entry, the syntax to which the values must conform, the
kinds of matching which can be performed on values of that
attribute, and other functions." to " An attribute is a
description (a type and zero or more options) with one or more
associated values. The attribute type governs whether the
attribute can have multiple values, the syntax and matching rules
used to construct and compare values of that attribute, and other
functions. Options indicate modes of transfer and other
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functions.". This points out that an attribute consists of both
the type and options.
C.5.2 Section 4
- Changed "Section 5.1 specifies the encoding rules for the LDAP
protocol" to "Section 5.1 specifies how the protocol is encoded
and transferred."
C.5.3 Section 4.1.2
- Added ABNF for the textual representation of LDAPOID. Previously,
there was no formal BNF for this construct.
C.5.4 Section 4.1.4
- Changed "This identifier may be written as decimal digits with
components separated by periods, e.g. "2.5.4.10"" to "may be
written as defined by ldapOID in section 4.1.2" in the second
paragraph. This was done because we now have a formal BNF
definition of an oid.
C.5.5 Section 4.1.5
- Changed the BNF for AttributeDescription to ABNF. This was done
for readability and consistency (no functional changes involved).
- Changed "Options present in an AttributeDescription are never
mutually exclusive." to "Options MAY be mutually exclusive. An
AttributeDescription with mutually exclusive options is treated as
an undefined attribute type." for clarity. It is generally
understood that this is the original intent, but the wording could
be easily misinterpreted.
- Changed "Any option could be associated with any AttributeType,
although not all combinations may be supported by a server." to
"Though any option or set of options could be associated with any
AttributeType, the server support for certain combinations may be
restricted by attribute type, syntaxes, or other factors.". This
is to clarify the meaning of 'combination' (it applies both to
combination of attribute type and options, and combination of
options). It also gives examples of *why* they might be
unsupported.
C.5.6 Section 4.1.11
- Changed the wording regarding 'equally capable' referrals to "If
multiple URLs are present, the client assumes that any URL may be
used to progress the operation.". The previous language implied
that the server MUST enforce rules that it was practically
incapable of. The new language highlights the original intent--
that is, that any of the referrals may be used to progress the
operation, there is no inherent 'weighting' mechanism.
C.5.7 Section 4.5.1 and Appendix A
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- Added the comment "-- initial and final can occur at most once",
to clarify this restriction.
C.5.8 Section 5.1
- Changed heading from "Mapping Onto BER-based Transport Services"
to "Protocol Encoding".
C.5.9 Section 5.2.1
- Changed "The LDAPMessage PDUs" to "The encoded LDAPMessage PDUs"
to point out that the PDUs are encoded before being streamed to
TCP.
C.6 Changes made to draft-ietf-ldapbis-protocol-04.txt:
C.6.1 Section 4.5.1 and Appendix A
- Changed the ASN.1 for the and and or choices of Filter to have a
lower range of 1. This was an omission in the original ASN.1
C.6.2 Various
- Fixed various typo's
C.7 Changes made to draft-ietf-ldapbis-protocol-05.txt:
C.7.1 Section 3.2.1
- Added "(as defined in Section 12.4.1 of [X.501])" to the fifth
paragraph when talking about "operational attributes". This is
because the term "operational attributes" is never defined.
Alternately, we could drag a definition into the spec, for now,
I'm just pointing to the reference in X.501.
C.7.2 Section 4.1.5
- Changed "And is also case insensitive" to "The entire
AttributeDescription is case insensitive". This is to clarify
whether we're talking about the entire attribute description, or
just the options.
- Expounded on the definition of attribute description options. This
doc now specifies a difference between transfer and tagging
options and describes the semantics of each, and how and when
subtyping rules apply. Now allow options to be transmitted in any
order but disallow any ordering semantics to be implied. These
changes are the result of ongoing input from an engineering team
designed to deal with ambiguity issues surrounding attribute
options.
C.7.3 Sections 4.1.5.1 and 4.1.6
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- Refer to non "binary" transfer encodings as "native encoding"
rather than "string" encoding to clarify and avoid confusion.
C.8 Changes made to draft-ietf-ldapbis-protocol-06.txt:
C.8.1 Title
- Changed to "LDAP: The Protocol" to be consisted with other working
group documents
C.8.2 Abstract
- Moved above TOC to conform to new guidelines
- Reworded to make consistent with other WG documents.
- Moved 2119 conventions to "Conventions" section
C.8.3 Introduction
- Created to conform to new guidelines
C.8.4 Models
- Removed section. There is only one model in this document
(Protocol Model)
C.8.5 Protocol Model
- Removed antiquated paragraph: "In keeping with the goal of easing
the costs associated with use of the directory, it is an objective
of this protocol to minimize the complexity of clients so as to
facilitate widespread deployment of applications capable of using
the directory."
- Removed antiquated paragraph concerning LDAP v1 and v2 and
referrals.
C.8.6 Data Model
- Removed Section 3.2 and subsections. These have been moved to
[Models]
C.8.7 Relationship to X.500
- Removed section. It has been moved to [Roadmap]
C.8.8 Server Specific Data Requirements
- Removed section. It has been moved to [Models]
C.8.9 Elements of Protocol
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- Added "Section 5.1 specifies how the protocol is encoded and
transferred." to the end of the first paragraph for reference.
- Reworded notes about extensibility, and now talk about implied
extensibility and the use of ellipses in the ASN.1
- Removed references to LDAPv2 in third and fourth paragraphs.
C.8.10 Message ID
- Reworded second paragraph to "The message ID of a request MUST
have a non-zero value different from the values of any other
requests outstanding in the LDAP session of which this message is
a part. The zero value is reserved for the unsolicited
notification message." (Added notes about non-zero and the zero
value).
C.8.11 String Types
- Removed ABNF for LDAPOID and added "Although an LDAPOID is encoded
as an OCTET STRING, values are limited to the definition of
numericoid given in Section 1.3 of [Models]."
C.8.12 Distinguished Name and Relative Distinguished Name
- Removed ABNF and referred to [Models] and [LDAPDN] where this is
defined.
C.8.13 Attribute Type
- Removed sections. It's now in the [Models] doc.
C.8.14 Attribute Description
- Removed ABNF and aligned section with [Models]
- Moved AttributeDescriptionList here.
C.8.15 Transfer Options
- Added section and consumed much of old options language (while
aligning with [Models]
C.8.16 Binary Transfer Option
- Clarified intent regarding exactly what is to be BER encoded.
- Clarified that clients must not expect ;binary when not asking for
it (;binary, as opposed to ber encoded data).
C.8.17 Attribute
- Use the term "attribute description" in lieu of "type"
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- Clarified the fact that clients cannot rely on any apparent
ordering of attribute values.
C.8.18 LDAPResult
- To resultCode, added ellipses "..." to the enumeration to indicate
extensibility. and added a note, pointing to [LDAPIANA]
- Removed error groupings ad refer to Appendix A.
C.8.19 Bind Operation
- Added "Prior to the BindRequest, the implied identity is
anonymous. Refer to [AuthMeth] for the authentication-related
semantics of this operation." to the first paragraph.
- Added ellipses "..." to AuthenticationChoice and added a note
"This type is extensible as defined in Section 3.6 of [LDAPIANA].
Servers that do not support a choice supplied by a client will
return authMethodNotSupported in the result code of the
BindResponse."
- Simplified text regarding how the server handles unknown versions.
Removed references to LDAPv2
C.8.20 Sequencing of the Bind Request
- Aligned with [AuthMeth] In particular, paragraphs 4 and 6 were
removed, while a portion of 4 was retained (see C.8.9)
C.8.21 Authentication and other Security Service
- Section was removed. Now in [AuthMeth]
C.8.22 Continuation References in the Search Result
- Added "If the originating search scope was singleLevel, the scope
part of the URL will be baseObject."
C.8.23 Security Considerations
- Removed reference to LDAPv2
C.8.24 Result Codes
- Added as normative appendix A
C.8.25 ASN.1
- Added EXTENSIBILITY IMPLIED
- Added a number of comments holding referenced to [Models] and
[ISO10646].
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- Removed AttributeType. It is not used.
C.9 Changes made to draft-ietf-ldapbis-protocol-07.txt:
- Removed all mention of transfer encodings and the binary attribute
option
- Further alignment with [Models].
- Added extensibility ellipsis to protocol op choice
- In 4.1.1, clarified when connections may be dropped due to
malformed PDUs
- Specified which matching rules and syntaxes are used for various
filter items
C.10 Changes made to draft-ietf-ldapbis-protocol-08.txt:
C.10.1 Section 4.1.1.1:
- Clarified when it is and isn't appropriate to return an already
used message id.
C.10.2 Section 4.1.11:
- Clarified that a control only applies to the message it's attached
to.
- Explained that the criticality field is only applicable to certain
request messages.
- Added language regarding the combination of controls.
C.10.3 Section 4.11:
- Explained that Abandon and Unbind cannot be abandoned, and
illustrated how to determine whether an operation has been
abandoned.
C.11 Changes made to draft-ietf-ldapbis-protocol-09.txt:
- Fixed formatting
C.12 Changes made to draft-ietf-ldapbis-protocol-10.txt:
C.12.1 Section 4.1.4:
- Removed second paragraph as this language exists in MODELS
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C.12.2 Section 4.2.1:
- Replaced fourth paragraph. It was accidentally removed in an
earlier edit.
C.12.2 Section 4.13:
- Added section describing the StartTLS operation (moved from
authmeth)
C.13 Changes made to draft-ietf-ldapbis-protocol-11.txt:
C.13.1 Section 4.1.9
- Changed "errorMessage" to "diagnosticMessage". Simply to indicate
that the field may be non-empty even if a non-error resultCode is
present.
C.13.2 Section 4.2:
- Reconciled language in "name" definition with [AuthMeth]
C.13.3 Section 4.2.1
- Renamed to "Processing of the Bind Request", and moved some text
from 4.2 into this section.
- Rearranged paragraphs to flow better.
- Specified that (as well as failed) an abandoned bind operation
will leave the connection in an anonymous state.
C.13.4 Section 4.5.3
- Generalized the second paragraph which cited indexing and
searchreferralreferences.
C.14 Changes made to draft-ietf-ldapbis-protocol-12.txt:
- Reworked bind errors.
- General clarifications and edits
Appendix D - Outstanding Work Items
D.0 General
- Integrate notational consistency agreements WG will discuss
notation consistency. Once agreement happens, reconcile draft.
- Reconcile problems with [Models]. Section 3.2 was wholly removed.
There were some protocol semantics in that section that need to be
brought back. Specifically, there was the notion of the server
implicitly adding objectclass superclasses when a value is added.
D.1 Make result code usage consistent.
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- While there is a result code appendix, ensure it speaks of result
codes in a general sense, and only highlight specific result codes
in the context of an operation when that operation ties more
specific meanings to that result code.
D.2 Verify references.
- Many referenced documents have changed. Ensure references and
section numbers are correct.
D.3 Usage of Naming Context
- Make sure occurrences of "namingcontext" and "naming context" are
consistent with [Models]. Use in section 6.2 should be reworked.
It's layers of indirection that matter, not number of contexts.
(That is, referrals can be returned for a number of reasons (cross
reference, superior, subordinate, busy, not master, etc.)
Other uses are fine.
D.4 Review 2119 usage
D.5 Reconcile with I-D Nits
D.23 Section 4.5.3
- A server MUST NOT return any SearchResultReference if it has not
located the baseObject and thus has not searched any entries; in
this case it would return a SearchResultDone containing a referral
resultCode.
- Add "Similarly, a server MUST NOT return a SearchResultReference
when the scope of the search is baseObject. If a client receives
such a SearchResultReference it MUST interpret is as a protocol
error and MUST NOT follow it." to the first paragraph.
The technical specification doesn't have to describe how a
protocol peer should react when its partner violates an absolute.
OR return noSuchObject.
- Add "If the scope part of the LDAP URL is present, the client MUST
use the new scope in its next request to progress the search. If
the scope part is absent the client MUST use subtree scope to
complete subtree searches and base scope to complete one level
searches." to the third paragraph.
D.25 Section 4.6
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- Resolve the meaning of "and is ignored if the attribute does not
exist". See "modify: "non-existent attribute"" on the list. Not
sure if there's really an issue here. Will look at archive
D.27 Section 4.10
- Specify what happens when the attr is missing vs. attr isn't in
schema. Also what happens if there's no equality matching rule.
noSuchAttribute, undefinedAttributeType, inappropriateMatching
D.30 Section 5.1
- Add "control and extended operation values" to last paragraph. See
"LBER (BER Restrictions)" on list.
D.32 Section 6.1
- Add "that are used by those attributes" to the first paragraph.
- Add "Servers which support update operations MUST, and other
servers SHOULD, support strong authentication mechanisms described
in [RFC2829]." as a second paragraph. Likely should just say
Requirements of authentication methods, SASL mechanisms, and TLS
are described in [AUTHMETH]." (also apply to next two below)
- Add "Servers which provide access to sensitive information MUST,
and other servers SHOULD support privacy protections such as those
described in [RFC2829] and [RFC2830]." as a third paragraph.
D.33 Section 7
- Add "Servers which support update operations MUST, and other
servers SHOULD, support strong authentication mechanisms described
in [RFC2829]." as a fourth paragraph.
- Add "In order to automatically follow referrals, clients may need
to hold authentication secrets. This poses significant privacy and
security concerns and SHOULD be avoided." as a sixth paragraph.
There are concerns with "automatic" chasing regardless of which,
if any, authentication method/mechanism is used.
- Add notes regarding DoS attack found by CERT advisories.
D.34 Appendix C
- C.9. Explain why we removed ;binary, and what clients can do to
get around potential problems (likely refer to an I-D)
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or assist in its implementation may be prepared, copied, published
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