Network Working Group
M. Wahl
Request for Comments: 2251
Critical Angle Inc.
Category: Standards Track
T. Howes
Netscape Communications Corp.
S. Kille
Isode Limited
December 1997
Lightweight Directory Access Protocol (v3)
1. Status of this Memo
This document specifies an Internet standards track protocol
for the
Internet community, and requests discussion and suggestions
for
improvements. Please refer to the current edition
of the "Internet
Official Protocol Standards" (STD 1) for the standardization
state
and status of this protocol. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1997). All Rights Reserved.
IESG Note
This document describes a directory access protocol that
provides
both read and update access. Update access requires
secure
authentication, but this document does not mandate implementation
of
any satisfactory authentication mechanisms.
In accordance with RFC 2026, section 4.4.1, this specification
is
being approved by IESG as a Proposed Standard despite
this
limitation, for the following reasons:
a. to encourage implementation and interoperability testing
of
these protocols (with or without update
access) before they
are deployed, and
b. to encourage deployment and use of these protocols in
read-only
applications. (e.g. applications
where LDAPv3 is used as
a query language for directories which
are updated by some
secure mechanism other than LDAP), and
c. to avoid delaying the advancement and deployment of
other Internet
standards-track protocols which require
the ability to query, but
not update, LDAPv3 directory servers.
Wahl, et. al. Standards Track [Page 1]
RFC 2251
LDAPv3
December 1997
Readers are hereby warned that until mandatory authentication
mechanisms are standardized, clients and servers written
according to
this specification which make use of update functionality
are
UNLIKELY TO INTEROPERATE, or MAY INTEROPERATE ONLY IF
AUTHENTICATION
IS REDUCED TO AN UNACCEPTABLY WEAK LEVEL.
Implementors are hereby discouraged from deploying LDAPv3
clients or
servers which implement the update functionality, until
a Proposed
Standard for mandatory authentication in LDAPv3 has been
approved and
published as an RFC.
Table of Contents
1. Status of this Memo ....................................
1
Copyright Notice .......................................
1
IESG Note ..............................................
1
2. Abstract ...............................................
3
3. Models .................................................
4
3.1. Protocol Model ........................................
4
3.2. Data Model ............................................
5
3.2.1. Attributes of Entries ...............................
5
3.2.2. Subschema Entries and Subentries ....................
7
3.3. Relationship to X.500 .................................
8
3.4. Server-specific Data Requirements .....................
8
4. Elements of Protocol ...................................
9
4.1. Common Elements .......................................
9
4.1.1. Message Envelope ....................................
9
4.1.1.1. Message ID ........................................
11
4.1.2. String Types ........................................
11
4.1.3. Distinguished Name and Relative Distinguished Name
.. 11
4.1.4. Attribute Type ......................................
12
4.1.5. Attribute Description ...............................
13
4.1.5.1. Binary Option .....................................
14
4.1.6. Attribute Value .....................................
14
4.1.7. Attribute Value Assertion ...........................
15
4.1.8. Attribute ...........................................
15
4.1.9. Matching Rule Identifier ............................
15
4.1.10. Result Message .....................................
16
4.1.11. Referral ...........................................
18
4.1.12. Controls ...........................................
19
4.2. Bind Operation ........................................
20
4.2.1. Sequencing of the Bind Request ......................
21
4.2.2. Authentication and Other Security Services ..........
22
4.2.3. Bind Response .......................................
23
4.3. Unbind Operation ......................................
24
4.4. Unsolicited Notification ..............................
24
4.4.1. Notice of Disconnection .............................
24
4.5. Search Operation ......................................
25
Wahl, et. al. Standards Track [Page 2]
RFC 2251
LDAPv3
December 1997
4.5.1. Search Request ......................................
25
4.5.2. Search Result .......................................
29
4.5.3. Continuation References in the Search Result ........
31
4.5.3.1. Example ...........................................
31
4.6. Modify Operation ......................................
32
4.7. Add Operation .........................................
34
4.8. Delete Operation ......................................
35
4.9. Modify DN Operation ...................................
36
4.10. Compare Operation ....................................
37
4.11. Abandon Operation ....................................
38
4.12. Extended Operation ...................................
38
5. Protocol Element Encodings and Transfer ................
39
5.1. Mapping Onto BER-based Transport Services .............
39
5.2. Transfer Protocols ....................................
40
5.2.1. Transmission Control Protocol (TCP) .................
40
6. Implementation Guidelines ..............................
40
6.1. Server Implementations ................................
40
6.2. Client Implementations ................................
40
7. Security Considerations ................................
41
8. Acknowledgements .......................................
41
9. Bibliography ...........................................
41
10. Authors' Addresses .....................................
42
Appendix A - Complete ASN.1 Definition .....................
44
Full Copyright Statement ...................................
50
2. Abstract
The protocol described in this document is designed to
provide access
to directories supporting the X.500 models, while not
incurring the
resource requirements of the X.500 Directory Access Protocol
(DAP).
This protocol is specifically targeted at management applications
and
browser applications that provide read/write interactive
access to
directories. When used with a directory supporting the
X.500
protocols, it is intended to be a complement to the X.500
DAP.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY"
in this document
are to be interpreted as described in RFC 2119 [10].
Key aspects of this version of LDAP are:
- All protocol elements of LDAPv2 (RFC 1777) are supported.
The
protocol is carried directly over TCP or other
transport, bypassing
much of the session/presentation overhead
of X.500 DAP.
- Most protocol data elements can be encoded as ordinary
strings
(e.g., Distinguished Names).
Wahl, et. al. Standards Track [Page 3]
RFC 2251
LDAPv3
December 1997
- Referrals to other servers may be returned.
- SASL mechanisms may be used with LDAP to provide association
security services.
- Attribute values and Distinguished Names have been
internationalized through the use of the ISO
10646 character set.
- The protocol can be extended to support new operations,
and
controls may be used to extend existing operations.
- Schema is published in the directory for use by clients.
3. Models
Interest in X.500 [1] directory technologies in the Internet
has led
to efforts to reduce the high cost of entry associated
with use of
these technologies. This document continues the
efforts to define
directory protocol alternatives, updating the LDAP [2]
protocol
specification.
3.1. Protocol Model
The general model adopted by this protocol is one of clients
performing protocol operations against servers. In this
model, a
client transmits a protocol request describing the operation
to be
performed to a server. The server is then responsible
for performing
the necessary operation(s) in the directory. Upon completion
of the
operation(s), the server returns a response containing
any results or
errors to the requesting client.
In keeping with the goal of easing the costs associated
with use of
the directory, it is an objective of this protocol to
minimize the
complexity of clients so as to facilitate widespread deployment
of
applications capable of using the directory.
Note that although servers are required to return responses
whenever
such responses are defined in the protocol, there is no
requirement
for synchronous behavior on the part of either clients
or servers.
Requests and responses for multiple operations may be
exchanged
between a client and server in any order, provided the
client
eventually receives a response for every request that
requires one.
In LDAP versions 1 and 2, no provision was made for protocol
servers
returning referrals to clients. However, for improved
performance
and distribution this version of the protocol permits
servers to
return to clients referrals to other servers. This
allows servers to
offload the work of contacting other servers to progress
operations.
Wahl, et. al. Standards Track [Page 4]
RFC 2251
LDAPv3
December 1997
Note that the core protocol operations defined in this
document can
be mapped to a strict subset of the X.500(1997) directory
abstract
service, so it can be cleanly provided by the DAP.
However there is
not a one-to-one mapping between LDAP protocol operations
and DAP
operations: server implementations acting as a gateway
to X.500
directories may need to make multiple DAP requests.
3.2. Data Model
This section provides a brief introduction to the X.500
data model,
as used by LDAP.
The LDAP protocol assumes there are one or more servers
which jointly
provide access to a Directory Information Tree (DIT).
The tree is
made up of entries. Entries have names: one or more
attribute values
from the entry form its relative distinguished name (RDN),
which MUST
be unique among all its siblings. The concatenation
of the relative
distinguished names of the sequence of entries from a
particular
entry to an immediate subordinate of the root of the tree
forms that
entry's Distinguished Name (DN), which is unique in the
tree. An
example of a Distinguished Name is
CN=Steve Kille, O=Isode Limited, C=GB
Some servers may hold cache or shadow copies of entries,
which can be
used to answer search and comparison queries, but will
return
referrals or contact other servers if modification operations
are
requested.
Servers which perform caching or shadowing MUST ensure
that they do
not violate any access control constraints placed on the
data by the
originating server.
The largest collection of entries, starting at an entry
that is
mastered by a particular server, and including all its
subordinates
and their subordinates, down to the entries which are
mastered by
different servers, is termed a naming context. The
root of the DIT
is a DSA-specific Entry (DSE) and not part of any naming
context:
each server has different attribute values in the root
DSE. (DSA is
an X.500 term for the directory server).
3.2.1. Attributes of Entries
Entries consist of a set of attributes. An attribute
is a type with
one or more associated values. The attribute type
is identified by a
short descriptive name and an OID (object identifier).
The attribute
Wahl, et. al. Standards Track [Page 5]
RFC 2251
LDAPv3
December 1997
type governs whether there can be more than one value of
an attribute
of that type in an entry, the syntax to which the values
must
conform, the kinds of matching which can be performed
on values of
that attribute, and other functions.
An example of an attribute is "mail". There may be one
or more values
of this attribute, they must be IA5 (ASCII) strings, and
they are
case insensitive (e.g. "foo@bar.com" will match "FOO@BAR.COM").
Schema is the collection of attribute type definitions,
object class
definitions and other information which a server uses
to determine
how to match a filter or attribute value assertion (in
a compare
operation) against the attributes of an entry, and whether
to permit
add and modify operations. The definition of schema
for use with
LDAP is given in [5] and [6]. Additional schema
elements may be
defined in other documents.
Each entry MUST have an objectClass attribute. The
objectClass
attribute specifies the object classes of an entry, which
along with
the system and user schema determine the permitted attributes
of an
entry. Values of this attribute may be modified
by clients, but the
objectClass attribute cannot be removed. Servers
may restrict the
modifications of this attribute to prevent the basic structural
class
of the entry from being changed (e.g. one cannot change
a person into
a country). When creating an entry or adding an
objectClass value to
an entry, all superclasses of the named classes are implicitly
added
as well if not already present, and the client must supply
values for
any mandatory attributes of new superclasses.
Some attributes, termed operational attributes, are used
by servers
for administering the directory system itself. They
are not returned
in search results unless explicitly requested by name.
Attributes
which are not operational, such as "mail", will have their
schema and
syntax constraints enforced by servers, but servers will
generally
not make use of their values.
Servers MUST NOT permit clients to add attributes to an
entry unless
those attributes are permitted by the object class definitions,
the
schema controlling that entry (specified in the subschema
- see
below), or are operational attributes known to that server
and used
for administrative purposes. Note that there is
a particular
objectClass 'extensibleObject' defined in [5] which permits
all user
attributes to be present in an entry.
Entries MAY contain, among others, the following operational
attributes, defined in [5]. These attributes are maintained
automatically by the server and are not modifiable by
clients:
Wahl, et. al. Standards Track [Page 6]
RFC 2251
LDAPv3
December 1997
- creatorsName: the Distinguished Name of the user who
added this
entry to the directory.
- createTimestamp: the time this entry was added to the directory.
- modifiersName: the Distinguished Name of the user who
last modified
this entry.
- modifyTimestamp: the time this entry was last modified.
- subschemaSubentry: the Distinguished Name of the
subschema entry
(or subentry) which controls the schema for
this entry.
3.2.2. Subschema Entries and Subentries
Subschema entries are used for administering information
about the
directory schema, in particular the object classes and
attribute
types supported by directory servers. A single subschema
entry
contains all schema definitions used by entries in a particular
part
of the directory tree.
Servers which follow X.500(93) models SHOULD implement
subschema
using the X.500 subschema mechanisms, and so these subschemas
are not
ordinary entries. LDAP clients SHOULD NOT assume
that servers
implement any of the other aspects of X.500 subschema.
A server
which masters entries and permits clients to modify these
entries
MUST implement and provide access to these subschema entries,
so that
its clients may discover the attributes and object classes
which are
permitted to be present. It is strongly recommended that
all other
servers implement this as well.
The following four attributes MUST be present in all subschema
entries:
- cn: this attribute MUST be used to form the RDN of the
subschema
entry.
- objectClass: the attribute MUST have at least the values
"top" and
"subschema".
- objectClasses: each value of this attribute specifies
an object
class known to the server.
- attributeTypes: each value of this attribute specifies
an attribute
type known to the server.
These are defined in [5]. Other attributes MAY be present
in
subschema entries, to reflect additional supported capabilities.
Wahl, et. al. Standards Track [Page 7]
RFC 2251
LDAPv3
December 1997
These include matchingRules, matchingRuleUse, dITStructureRules,
dITContentRules, nameForms and ldapSyntaxes.
Servers SHOULD provide the attributes createTimestamp and
modifyTimestamp in subschema entries, in order to allow
clients to
maintain their caches of schema information.
Clients MUST only retrieve attributes from a subschema
entry by
requesting a base object search of the entry, where the
search filter
is "(objectClass=subschema)". (This will allow LDAPv3
servers which
gateway to X.500(93) to detect that subentry information
is being
requested.)
3.3. Relationship to X.500
This document defines LDAP in terms of X.500 as an X.500
access
mechanism. An LDAP server MUST act in accordance
with the
X.500(1993) series of ITU recommendations when providing
the service.
However, it is not required that an LDAP server make use
of any X.500
protocols in providing this service, e.g. LDAP can be
mapped onto any
other directory system so long as the X.500 data and service
model as
used in LDAP is not violated in the LDAP interface.
3.4. Server-specific Data Requirements
An LDAP server MUST provide information about itself and
other
information that is specific to each server. This
is represented as
a group of attributes located in the root DSE (DSA-Specific
Entry),
which is named with the zero-length LDAPDN. These
attributes are
retrievable if a client performs a base object search
of the root
with filter "(objectClass=*)", however they are subject
to access
control restrictions. The root DSE MUST NOT be included
if the
client performs a subtree search starting from the root.
Servers may allow clients to modify these attributes.
The following attributes of the root DSE are defined in
section 5 of
[5]. Additional attributes may be defined in other
documents.
- namingContexts: naming contexts held in the server. Naming
contexts
are defined in section 17 of X.501 [6].
- subschemaSubentry: subschema entries (or subentries)
known by this
server.
- altServer: alternative servers in case this one is later
unavailable.
Wahl, et. al. Standards Track [Page 8]
RFC 2251
LDAPv3
December 1997
- supportedExtension: list of supported extended operations.
- supportedControl: list of supported controls.
- supportedSASLMechanisms: list of supported SASL security features.
- supportedLDAPVersion: LDAP versions implemented by the server.
If the server does not master entries and does not know
the locations
of schema information, the subschemaSubentry attribute
is not present
in the root DSE. If the server masters directory
entries under one
or more schema rules, there may be any number of values
of the
subschemaSubentry attribute in the root DSE.
4. Elements of Protocol
The LDAP protocol is described using Abstract Syntax Notation
1
(ASN.1) [3], and is typically transferred using a subset
of ASN.1
Basic Encoding Rules [11]. In order to support future
extensions to
this protocol, clients and servers MUST ignore elements
of SEQUENCE
encodings whose tags they do not recognize.
Note that unlike X.500, each change to the LDAP protocol
other than
through the extension mechanisms will have a different
version
number. A client will indicate the version it supports
as part of
the bind request, described in section 4.2. If a
client has not sent
a bind, the server MUST assume that version 3 is supported
in the
client (since version 2 required that the client bind
first).
Clients may determine the protocol version a server supports
by
reading the supportedLDAPVersion attribute from the root
DSE. Servers
which implement version 3 or later versions MUST provide
this
attribute. Servers which only implement version
2 may not provide
this attribute.
4.1. Common Elements
This section describes the LDAPMessage envelope PDU (Protocol
Data
Unit) format, as well as data type definitions which are
used in the
protocol operations.
4.1.1. Message Envelope
For the purposes of protocol exchanges, all protocol operations
are
encapsulated in a common envelope, the LDAPMessage, which
is defined
as follows:
LDAPMessage ::= SEQUENCE
{
Wahl, et. al. Standards Track [Page 9]
RFC 2251
LDAPv3
December 1997
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
The function of the LDAPMessage is to provide an envelope
containing
common fields required in all protocol exchanges. At this
time the
only common fields are the message ID and the controls.
If the server receives a PDU from the client in which the
LDAPMessage
SEQUENCE tag cannot be recognized, the messageID cannot
be parsed,
the tag of the protocolOp is not recognized as a request,
or the
encoding structures or lengths of data fields are found
to be
incorrect, then the server MUST return the notice of disconnection
described in section 4.4.1, with resultCode protocolError,
and
immediately close the connection. In other cases that
the server
cannot parse the request received by the client, the server
MUST
return an appropriate response to the request, with the
resultCode
set to protocolError.
If the client receives a PDU from the server which cannot
be parsed,
the client may discard the PDU, or may abruptly close
the connection.
The ASN.1 type Controls is defined in section 4.1.12.
Wahl, et. al. Standards Track [Page 10]
RFC 2251
LDAPv3
December 1997
4.1.1.1. Message ID
All LDAPMessage envelopes encapsulating responses contain
the
messageID value of the corresponding request LDAPMessage.
The message ID of a request MUST have a value different
from the
values of any other requests outstanding in the LDAP session
of which
this message is a part.
A client MUST NOT send a second request with the same message
ID as
an earlier request on the same connection if the client
has not
received the final response from the earlier request.
Otherwise the
behavior is undefined. Typical clients increment
a counter for each
request.
A client MUST NOT reuse the message id of an abandonRequest
or of the
abandoned operation until it has received a response from
the server
for another request invoked subsequent to the abandonRequest,
as the
abandonRequest itself does not have a response.
4.1.2. String Types
The LDAPString is a notational convenience to indicate
that, although
strings of LDAPString type encode as OCTET STRING types,
the ISO
10646 [13] character set (a superset of Unicode) is used,
encoded
following the UTF-8 algorithm [14]. Note that in the UTF-8
algorithm
characters which are the same as ASCII (0x0000 through
0x007F) are
represented as that same ASCII character in a single byte.
The other
byte values are used to form a variable-length encoding
of an
arbitrary character.
LDAPString ::= OCTET STRING
The LDAPOID is a notational convenience to indicate that
the
permitted value of this string is a (UTF-8 encoded) dotted-decimal
representation of an OBJECT IDENTIFIER.
LDAPOID ::= OCTET STRING
For example,
1.3.6.1.4.1.1466.1.2.3
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
[4], such that
Wahl, et. al. Standards Track [Page 11]
RFC 2251
LDAPv3
December 1997
<distinguished-name> ::= <name>
<relative-distinguished-name> ::= <name-component>
where <name> and <name-component> are as defined in [4].
LDAPDN ::= LDAPString
RelativeLDAPDN ::= LDAPString
Only Attribute Types can be present in a relative distinguished
name
component; the options of Attribute Descriptions (next
section) MUST
NOT be used in specifying distinguished names.
4.1.4. Attribute Type
An AttributeType takes on as its value the textual string
associated
with that AttributeType in its specification.
AttributeType ::= LDAPString
Each attribute type has a unique OBJECT IDENTIFIER which
has been
assigned to it. This identifier may be written as
decimal digits
with components separated by periods, e.g. "2.5.4.10".
A specification may also assign one or more textual names
for an
attribute type. These names MUST begin with a letter,
and only
contain ASCII letters, digit characters and hyphens.
They are case
insensitive. (These ASCII characters are identical
to ISO 10646
characters whose UTF-8 encoding is a single byte between
0x00 and
0x7F.)
If the server has a textual name for an attribute type,
it MUST use a
textual name for attributes returned in search results.
The dotted-
decimal OBJECT IDENTIFIER is only used if there is no
textual name
for an attribute type.
Attribute type textual names are non-unique, as two different
specifications (neither in standards track RFCs) may choose
the same
name.
A server which masters or shadows entries SHOULD list all
the
attribute types it supports in the subschema entries,
using the
attributeTypes attribute. Servers which support
an open-ended set of
attributes SHOULD include at least the attributeTypes
value for the
'objectClass' attribute. Clients MAY retrieve the attributeTypes
value from subschema entries in order to obtain the OBJECT
IDENTIFIER
and other information associated with attribute types.
Wahl, et. al. Standards Track [Page 12]
RFC 2251
LDAPv3
December 1997
Some attribute type names which are used in this version
of LDAP are
described in [5]. Servers may implement additional
attribute types.
4.1.5. Attribute Description
An AttributeDescription is a superset of the definition
of the
AttributeType. It has the same ASN.1 definition,
but allows
additional options to be specified. They are also
case insensitive.
AttributeDescription ::= LDAPString
A value of AttributeDescription is based on the following BNF:
<AttributeDescription> ::= <AttributeType> [ ";" <options> ]
<options> ::= <option> | <option> ";" <options>
<option> ::= <opt-char> <opt-char>*
<opt-char> ::= ASCII-equivalent letters, numbers and hyphen
Examples of valid AttributeDescription:
cn
userCertificate;binary
One option, "binary", is defined in this document.
Additional
options may be defined in IETF standards-track and experimental
RFCs.
Options beginning with "x-" are reserved for private experiments.
Any option could be associated with any AttributeType,
although not
all combinations may be supported by a server.
An AttributeDescription with one or more options is treated
as a
subtype of the attribute type without any options.
Options present
in an AttributeDescription are never mutually exclusive.
Implementations MUST generate the <options> list sorted
in ascending
order, and servers MUST treat any two AttributeDescription
with the
same AttributeType and options as equivalent. A
server will treat an
AttributeDescription with any options it does not implement
as an
unrecognized attribute type.
The data type "AttributeDescriptionList" describes a list
of 0 or
more attribute types. (A list of zero elements has
special
significance in the Search request.)
AttributeDescriptionList
::= SEQUENCE OF
AttributeDescription
Wahl, et. al. Standards Track [Page 13]
RFC 2251
LDAPv3
December 1997
4.1.5.1. Binary Option
If the "binary" option is present in an AttributeDescription,
it
overrides any string-based encoding representation defined
for that
attribute in [5]. Instead the attribute is to be transferred
as a
binary value encoded using the Basic Encoding Rules [11].
The syntax
of the binary value is an ASN.1 data type definition which
is
referenced by the "SYNTAX" part of the attribute type
definition.
The presence or absence of the "binary" option only affects
the
transfer of attribute values in protocol; servers store
any
particular attribute in a single format. If a client
requests that a
server return an attribute in the binary format, but the
server
cannot generate that format, the server MUST treat this
attribute
type as an unrecognized attribute type. Similarly,
clients MUST NOT
expect servers to return an attribute in binary format
if the client
requested that attribute by name without the binary option.
This option is intended to be used with attributes whose
syntax is a
complex ASN.1 data type, and the structure of values of
that type is
needed by clients. Examples of this kind of syntax
are "Certificate"
and "CertificateList".
4.1.6. Attribute Value
A field of type AttributeValue takes on as its value either
a string
encoding of a AttributeValue data type, or an OCTET STRING
containing
an encoded binary value, depending on whether the "binary"
option is
present in the companion AttributeDescription to this
AttributeValue.
The definition of string encodings for different syntaxes
and types
may be found in other documents, and in particular [5].
AttributeValue ::= OCTET STRING
Note that there is no defined limit on the size of this
encoding;
thus protocol values may include multi-megabyte attributes
(e.g.
photographs).
Attributes may be defined which have arbitrary and non-printable
syntax. Implementations MUST NEITHER simply display
nor attempt to
decode as ASN.1 a value if its syntax is not known.
The
implementation may attempt to discover the subschema of
the source
entry, and retrieve the values of attributeTypes from
it.
Clients MUST NOT send attribute values in a request which
are not
valid according to the syntax defined for the attributes.
Wahl, et. al. Standards Track [Page 14]
RFC 2251
LDAPv3
December 1997
4.1.7. 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
If the "binary" option is present in attributeDesc, this
signals to
the server that the assertionValue is a binary encoding
of the
assertion value.
For all the string-valued user attributes described in
[5], the
assertion value syntax is the same as the value syntax.
Clients may
use attribute values as assertion values in compare requests
and
search filters.
Note however that the assertion syntax may be different
from the
value syntax for other attributes or for non-equality
matching rules.
These may have an assertion syntax which contains only
part of the
value. See section 20.2.1.8 of X.501 [6] for examples.
4.1.8. Attribute
An attribute consists of a type and one or more values
of that type.
(Though attributes MUST have at least one value when stored,
due to
access control restrictions the set may be empty when
transferred in
protocol. This is described in section 4.5.2, concerning
the
PartialAttributeList type.)
Attribute ::= SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Each attribute value is distinct in the set (no duplicates).
The
order of attribute values within the vals set is undefined
and
implementation-dependent, and MUST NOT be relied upon.
4.1.9. Matching Rule Identifier
A matching rule is a means of expressing how a server should
compare
an AssertionValue received in a search filter with an
abstract data
value. The matching rule defines the syntax of the
assertion value
and the process to be performed in the server.
Wahl, et. al. Standards Track [Page 15]
RFC 2251
LDAPv3
December 1997
An X.501(1993) Matching Rule is identified in the LDAP
protocol by
the printable representation of its OBJECT IDENTIFIER,
either as one
of the strings given in [5], or as decimal digits with
components
separated by periods, 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 4.4 of [5].
4.1.10. Result Message
The LDAPResult is the construct used in this protocol to
return
success or failure indications from servers to clients.
In response
to various requests servers will return responses containing
fields
of type LDAPResult to indicate the final status of a protocol
operation request.
LDAPResult ::= SEQUENCE {
resultCode ENUMERATED {
success
(0),
operationsError
(1),
protocolError
(2),
timeLimitExceeded
(3),
sizeLimitExceeded
(4),
compareFalse
(5),
compareTrue
(6),
authMethodNotSupported (7),
strongAuthRequired
(8),
-- 9 reserved --
referral
(10), -- new
adminLimitExceeded
(11), -- new
unavailableCriticalExtension (12), -- new
confidentialityRequired (13), -- new
saslBindInProgress
(14), -- new
noSuchAttribute
(16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation
(19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
Wahl, et. al. Standards Track [Page 16]
RFC 2251
LDAPv3
December 1997
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), -- new
-- 72-79 unused --
other
(80) },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
errorMessage LDAPString,
referral [3] Referral OPTIONAL
}
All the result codes with the exception of success, compareFalse
and
compareTrue are to be treated as meaning the operation
could not be
completed in its entirety.
Most of the result codes are based on problem indications
from X.511
error data types. Result codes from 16 to 21 indicate
an
AttributeProblem, codes 32, 33, 34 and 36 indicate a NameProblem,
codes 48, 49 and 50 indicate a SecurityProblem, codes
51 to 54
indicate a ServiceProblem, and codes 64 to 69 and 71 indicates
an
UpdateProblem.
If a client receives a result code which is not listed
above, it is
to be treated as an unknown error condition.
The errorMessage field of this construct may, at the server's
option,
be used to return a string containing a textual, human-readable
(terminal control and page formatting characters should
be avoided)
error diagnostic. As this error diagnostic is not standardized,
Wahl, et. al. Standards Track [Page 17]
RFC 2251
LDAPv3
December 1997
implementations MUST NOT rely on the values returned.
If the server
chooses not to return a textual diagnostic, the errorMessage
field of
the LDAPResult type MUST contain a zero length string.
For result codes of noSuchObject, aliasProblem, invalidDNSyntax
and
aliasDereferencingProblem, the matchedDN field is set
to the name of
the lowest entry (object or alias) in the directory that
was matched.
If no aliases were dereferenced while attempting to locate
the entry,
this will be a truncated form of the name provided, or
if aliases
were dereferenced, of the resulting name, as defined in
section 12.5
of X.511 [8]. The matchedDN field is to be set to a zero
length
string with all other result codes.
4.1.11. Referral
The referral error indicates that the contacted server
does not hold
the target entry of the request. The referral field
is present in an
LDAPResult if the LDAPResult.resultCode field value is
referral, and
absent with all other result codes. It contains
a reference to
another server (or set of servers) which may be accessed
via LDAP or
other protocols. Referrals can be returned in response
to any
operation request (except unbind and abandon which do
not have
responses). At least one URL MUST be present in the Referral.
The referral is not returned for a singleLevel or wholeSubtree
search
in which the search scope spans multiple naming contexts,
and several
different servers would need to be contacted to complete
the
operation. Instead, continuation references, described
in section
4.5.3, are returned.
Referral ::= SEQUENCE OF LDAPURL -- one or more
LDAPURL ::= LDAPString -- limited to characters permitted in URLs
If the client wishes to progress the operation, it MUST
follow the
referral by contacting any one of servers. All the
URLs MUST be
equally capable of being used to progress the operation.
(The
mechanisms for how this is achieved by multiple servers
are outside
the scope of this document.)
URLs for servers implementing the LDAP protocol are written
according
to [9]. 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
Wahl, et. al. Standards Track [Page 18]
RFC 2251
LDAPv3
December 1997
is present in an LDAPURL, the client MUST use this filter
in its next
request to progress this search, and if it is not present
the client
MUST use the same filter as it used for that search.
Other aspects
of the new request may be the same or different as the
request which
generated the referral.
Note that UTF-8 characters appearing in a DN or search
filter may not
be legal for URLs (e.g. spaces) and MUST be escaped using
the %
method in RFC 1738 [7].
Other kinds of URLs may be returned, so long as the operation
could
be performed using that protocol.
4.1.12. Controls
A control is a way to specify extension information. Controls
which
are sent as part of a request apply only to that request
and are not
saved.
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType
LDAPOID,
criticality
BOOLEAN DEFAULT FALSE,
controlValue
OCTET STRING OPTIONAL }
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.
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 and the
criticality
field is TRUE, the server MUST NOT perform the operation,
and MUST
instead return the resultCode unsupportedCriticalExtension.
If the control is not appropriate for the operation and
criticality
field is TRUE, the server MUST NOT perform the operation,
and MUST
instead return the resultCode unsupportedCriticalExtension.
If the control is unrecognized or inappropriate but the
criticality
field is FALSE, the server MUST ignore the control.
Wahl, et. al. Standards Track [Page 19]
RFC 2251
LDAPv3
December 1997
The controlValue contains any information associated with
the
control, and its format is defined for the control.
The server MUST
be prepared to handle arbitrary contents of the controlValue
octet
string, including zero bytes. It is absent only
if there is no value
information which is associated with a control of its
type.
This document does not define any controls. Controls
may be defined
in other documents. The definition of a control
consists of:
- the OBJECT IDENTIFIER assigned to the control,
- whether the control is always noncritical,
always critical, or
critical at the client's option,
- the format of the controlValue contents of the control.
Servers list the controls which they recognize in the
supportedControl attribute in the root DSE.
4.2. Bind Operation
The function of the Bind Operation is to allow authentication
information to be exchanged between the client and server.
The Bind Request is defined as follows:
BindRequest ::= [APPLICATION
0] SEQUENCE {
version
INTEGER (1 .. 127),
name
LDAPDN,
authentication AuthenticationChoice
}
AuthenticationChoice ::=
CHOICE {
simple
[0] OCTET STRING,
-- 1 and 2 reserved
sasl
[3] SaslCredentials }
SaslCredentials ::= SEQUENCE
{
mechanism
LDAPString,
credentials
OCTET STRING OPTIONAL }
Parameters of the Bind Request are:
- version: A version number indicating the version of the
protocol to
be used in this protocol session. This
document describes version
3 of the LDAP protocol. Note that there
is no version negotiation,
and the client just sets this parameter to
the version it desires.
If the client requests protocol version 2,
a server that supports
the version 2 protocol as described in [2]
will not return any v3-
Wahl, et. al. Standards Track [Page 20]
RFC 2251
LDAPv3
December 1997
specific protocol fields. (Note that
not all LDAP servers will
support protocol version 2, since they may
be unable to generate
the attribute syntaxes associated with version
2.)
- name: The name of the directory object that the client
wishes to
bind as. This field may take on a null
value (a zero length
string) for the purposes of anonymous binds,
when authentication
has been performed at a lower layer, or when
using SASL credentials
with a mechanism that includes the LDAPDN
in the credentials.
- authentication: information used to authenticate the
name, if any,
provided in the Bind Request.
Upon receipt of a Bind Request, a protocol server will
authenticate
the requesting client, if necessary. The server
will then return a
Bind Response to the client indicating the status of the
authentication.
Authorization is the use of this authentication information
when
performing operations. Authorization MAY be affected
by factors
outside of the LDAP Bind request, such as lower layer
security
services.
4.2.1. Sequencing of the Bind Request
For some SASL authentication mechanisms, it may be necessary
for the
client to invoke the BindRequest multiple times.
If at any stage the
client wishes to abort the bind process it MAY unbind
and then drop
the underlying connection. Clients MUST NOT invoke
operations
between two Bind requests made as part of a multi-stage
bind.
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, t?e server MUST return a BindResponse with
authMethodNotSupported as the resultCode. This will
allow clients to
abort a negotiation if it wishes to try again with the
same SASL
mechanism.
Unlike LDAP v2, the client need not send a Bind Request
in the first
PDU of the connection. The client may request any
operations and the
server MUST treat these as unauthenticated. If the server
requires
that the client bind before browsing or modifying the
directory, the
server MAY reject a request other than binding, unbinding
or an
extended request with the "operationsError" result.
Wahl, et. al. Standards Track [Page 21]
RFC 2251
LDAPv3
December 1997
If the client did not bind before sending a request and
receives an
operationsError, it may then send a Bind Request.
If this also fails
or the client chooses not to bind on the existing connection,
it will
close the connection, reopen it and begin again by first
sending a
PDU with a Bind Request. This will aid in interoperating
with
servers implementing other versions of LDAP.
Clients MAY send multiple bind requests on a connection
to change
their credentials. A subsequent bind process has
the effect of
abandoning all operations outstanding on the connection.
(This
simplifies server implementation.) Authentication
from earlier binds
are subsequently ignored, and so if the bind fails, the
connection
will be treated as anonymous. If a SASL transfer encryption
or
integrity mechanism has been negotiated, and that mechanism
does not
support the changing of credentials from one identity
to another,
then the client MUST instead establish a new connection.
4.2.2. Authentication and Other Security Services
The simple authentication option provides minimal authentication
facilities, with the contents of the authentication field
consisting
only of a cleartext password. Note that the use
of cleartext
passwords is not recommended over open networks when there
is no
authentication or encryption being performed by a lower
layer; see
the "Security Considerations" section.
If no authentication is to be performed, then the simple
authentication option MUST be chosen, and the password
be of zero
length. (This is often done by LDAPv2 clients.)
Typically the DN is
also of zero length.
The sasl choice allows for any mechanism defined for use
with SASL
[12]. The mechanism field contains the name of the
mechanism. The
credentials field contains the arbitrary data used for
authentication, inside an OCTET STRING wrapper.
Note that unlike
some Internet application protocols where SASL is used,
LDAP is not
text-based, thus no base64 transformations are performed
on the
credentials.
If any SASL-based integrity or confidentiality services
are enabled,
they take effect following the transmission by the server
and
reception by the client of the final BindResponse with
resultCode
success.
The client can request that the server use authentication
information
from a lower layer protocol by using the SASL EXTERNAL
mechanism.
Wahl, et. al. Standards Track [Page 22]
RFC 2251
LDAPv3
December 1997
4.2.3. Bind Response
The Bind Response is defined as follows.
BindResponse ::= [APPLICATION
1] SEQUENCE {
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
BindResponse consists simply of an indication from
the server of he
status of the client's request for authentication.
f the bind was successful, the resultCode will be success,
therwise
it will be one of:
- operationsError: server encountered an internal error,
- protocolError: unrecognized version number or incorrect
PDU
structure,
- authMethodNotSupported: unrecognized SASL mechanism name,
- strongAuthRequired: the server requires authentication
be
performed with a SASL mechanism,
- referral: this server cannot accept this bind and the
client
should try another,
- saslBindInProgress: the server requires the client to
send a
new bind request, with the same sasl mechanism,
to continue the
authentication process,
- inappropriateAuthentication: the server requires the
client
which had attempted to bind anonymously or
without supplying
credentials to provide some form of credentials,
- invalidCredentials: the wrong password was supplied or
the SASL
credentials could not be processed,
- unavailable: the server is shutting down.
If the server does not support the client's requested protocol
version, it MUST set the resultCode to protocolError.
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.)
Wahl, et. al. Standards Track [Page 23]
RFC 2251
LDAPv3
December 1997
The serverSaslCreds are used as part of a SASL-defined
bind mechanism
to allow the client to authenticate the server to which
it is
communicating, or to perform "challenge-response" authentication.
If
the client bound with the password choice, or the SASL
mechanism does
not require the server to return information to the client,
then this
field is not to be included in the result.
4.3. Unbind Operation
The function of the Unbind Operation is to terminate a
protocol
session. The Unbind Operation is defined as follows:
UnbindRequest ::= [APPLICATION 2] NULL
The Unbind Operation has no response defined. Upon transmission
of an
UnbindRequest, a protocol client may assume that the protocol
session
is terminated. Upon receipt of an UnbindRequest, a protocol
server
may assume that the requesting client has terminated the
session and
that all outstanding requests may be discarded, and may
close the
connection.
4.4. Unsolicited Notification
An unsolicited notification is an LDAPMessage sent from
the server to
the client which is not in response to any LDAPMessage
received by
the server. It is used to signal an extraordinary condition
in the
server or in the connection between the client and the
server. The
notification is of an advisory nature, and the server
will not expect
any response to be returned from the client.
The unsolicited notification is structured as an LDAPMessage
in which
the messageID is 0 and protocolOp is of the extendedResp
form. The
responseName field of the ExtendedResponse is present.
The LDAPOID
value MUST be unique for this notification, and not be
used in any
other situation.
One unsolicited notification is defined in this document.
4.4.1. Notice of Disconnection
This notification may be used by the server to advise the
client that
the server is about to close the connection due to an
error
condition. Note that this notification is NOT a
response to an
unbind requested by the client: the server MUST follow
the procedures
of section 4.3. This notification is intended to assist
clients in
distinguishing between an error condition and a transient
network
Wahl, et. al.
Standards Track
[Page 24]
RFC 2251
LDAPv3
December 1997
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.
- 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),
Wahl, et. al. Standards Track [Page 25]
RFC 2251
LDAPv3
December 1997
derefAlways
(3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and
[0] SET OF Filter,
or
[1] SET OF Filter,
not
[2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE
{
type
AttributeDescription,
-- at least one must be present
substrings SEQUENCE OF CHOICE {
initial [0] LDAPString,
any [1] LDAPString,
final [2] LDAPString } }
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;
Wahl, et. al. Standards Track [Page 26]
RFC 2251
LDAPv3
December 1997
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 sizelimit 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 sizelimit
restrictions are
in effect for the search. Servers may
enforce a maximum number of
entries to return.
- timelimit: A timelimit that restricts the maximum time
(in seconds)
allowed for a search. A value of 0 in this
field indicates that no
client-requested timelimit restrictions are
in effect for the
search.
- typesOnly: An indicator as to whether search results
will contain
both attribute types and values, or just attribute
types. Setting
this field to TRUE causes only attribute types
(no values) to be
returned. Setting this field to FALSE
causes both attribute types
and values to be returned.
- filter: A filter that defines the conditions that must
be fulfilled
in order for the search to match a given entry.
The 'and', 'or' and 'not' choices can be used
to form combinations of
filters. At least one filter element MUST
be present in an 'and' or
'or' choice. The others match against
individual attribute values of
entries in the scope of the search.
(Implementor's note: the 'not'
filter is an example of a tagged choice in
an implicitly-tagged
module. In BER this is treated as if
the tag was explicit.)
A server MUST evaluate filters according to
the three-valued logic
of X.511(93) 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.
Wahl, et. al. Standards Track [Page 27]
RFC 2251
LDAPv3
December 1997
A filter of the "and" choice is TRUE if all
the filters in the SET
OF evaluate to TRUE, FALSE if at least one
filter is FALSE, and
otherwise Undefined. A filter of the
"or" choice is FALSE if all
of the filters in the SET OF evaluate to FALSE,
TRUE if at least
one filter is TRUE, and Undefined otherwise.
A filter of the "not"
choice is TRUE if the filter being negated
is FALSE, FALSE if it is
TRUE, and Undefined if it is Undefined.
The present match evaluates to TRUE where there
is an attribute or
subtype of the specified attribute description
present in an entry,
and FALSE otherwise (including a presence
test with an unrecognized
attribute description.)
The extensibleMatch is new in this version
of LDAP. If the
matchingRule field is absent, the type field
MUST be present, and
the equality match is performed for that type.
If the type field is
absent and matchingRule is present, the matchValue
is compared
against all attributes in an entry which support
that matchingRule,
and the matchingRule determines the syntax
for the assertion value
(the filter item evaluates to TRUE if it matches
with at least
one attribute in the entry, FALSE if it does
not match any attribute
in the entry, and Undefined if the matchingRule
is not recognized
or the assertionValue cannot be parsed.)
If the type field is
present and matchingRule is present, the matchingRule
MUST be one
permitted for use with that type, otherwise
the filter item is
undefined. If the dnAttributes field
is set to TRUE, the match is
applied against all the attributes in an entry's
distinguished name
as well, and also evaluates to TRUE if there
is at least one
attribute in the distinguished name for which
the filter item
evaluates to TRUE. (Editors note: The
dnAttributes field is present
so that there does not need to be multiple
versions of generic
matching rules such as for word matching,
one to apply to entries
and another to apply to entries and dn attributes
as well).
A filter item evaluates to Undefined when the
server would not
be able to determine whether the assertion
value matches an
entry. If an attribute description in
an equalityMatch, substrings,
greaterOrEqual, lessOrEqual, approxMatch or
extensibleMatch
filter is not recognized by the server, a
matching rule id in the
extensibleMatch is not recognized by the server,
the assertion
value cannot be parsed, or the type of filtering
requested is not
implemented, then the filter is Undefined.
Thus for example if a
server did not recognize the attribute type
shoeSize, a filter of
(shoeSize=*) would evaluate to FALSE, and
the filters (shoeSize=12),
(shoeSize>=12) and (shoeSize<=12) would
evaluate to Undefined.
Wahl, et. al. Standards Track [Page 28]
RFC 2251
LDAPv3
December 1997
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
[8].
- attributes: A list of the attributes to be returned from
each entry
which matches the search filter. There are
two special values which
may be used: an empty list with no attributes,
and the attribute
description string "*". Both of these
signify that all user
attributes are to be returned. (The
"*" allows the client to
request all user attributes in addition to
specific operational
attributes).
Attributes MUST be named at most once in the
list, and are returned
at most once in an entry. If there
are attribute descriptions in
the list which are not recognized, they are
ignored by the server.
If the client does not want any attributes
returned, it can specify
a list containing only the attribute with
OID "1.1". This OID was
chosen arbitrarily and does not correspond
to any attribute in use.
Client implementors should note that even if
all user attributes are
requested, some attributes of the entry may
not be included in
search results due to access control 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 [5].)
Note that an X.500 "list"-like operation can be emulated
by the client
requesting a one-level LDAP search operation with a filter
checking
for the existence of the objectClass attribute, and that
an X.500
"read"-like operation can be emulated by a base object
LDAP search
operation with the same filter. A server which provides
a gateway to
X.500 is not required to use the Read or List operations,
although it
may choose to do so, and if it does must provide the same
semantics
as the X.500 search operation.
4.5.2. Search Result
The results of the search attempted by the server upon
receipt of a
Search Request are returned in Search Responses, which
are LDAP
messages containing either SearchResultEntry, SearchResultReference,
ExtendedResponse or SearchResultDone data types.
SearchResultEntry ::= [APPLICATION
4] SEQUENCE {
objectName LDAPDN,
Wahl, et. al. Standards Track [Page 29]
RFC 2251
LDAPv3
December 1997
attributes PartialAttributeList }
PartialAttributeList ::=
SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
-- implementors should note
that the PartialAttributeList may
-- have zero elements (if
none of the attributes of that entry
-- were requested, or could
be returned), and that the vals set
-- may also have zero elements
(if types only was requested, or
-- all values were excluded
from the result.)
SearchResultReference ::=
[APPLICATION 19] SEQUENCE OF LDAPURL
-- at least one LDAPURL
element must be present
SearchResultDone ::= [APPLICATION 5] LDAPResult
Upon receipt of a Search Request, a server will perform
the necessary
search of the DIT.
If the LDAP session is operating over a connection-oriented
transport
such as TCP, the server will return to the client a sequence
of
responses in separate LDAP messages. There may be
zero or more
responses containing SearchResultEntry, one for each entry
found
during the search. There may also be zero or more
responses
containing SearchResultReference, one for each area not
explored by
this server during the search. The SearchResultEntry
and
SearchResultReference PDUs may come in any order. Following
all the
SearchResultReference responses and all SearchResultEntry
responses
to be returned by the server, the server will return a
response
containing the SearchResultDone, which contains an indication
of
success, or detailing any errors that have occurred.
Each entry returned in a SearchResultEntry will contain
all
attributes, complete with associated values if necessary,
as
specified in the attributes field of the Search Request.
Return of
attributes is subject to access control and other administrative
policy. Some attributes may be returned in binary
format (indicated
by the AttributeDescription in the response having the
binary option
present).
Some attributes may be constructed by the server and appear
in a
SearchResultEntry attribute list, although they are not
stored
attributes of an entry. Clients MUST NOT assume that all
attributes
can be modified, even if permitted by access control.
LDAPMessage responses of the ExtendedResponse form are
reserved for
returning information associated with a control requested
by the
client. These may be defined in future versions
of this document.
Wahl, et. al. Standards Track [Page 30]
RFC 2251
LDAPv3
December 1997
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, each containing a reference to
another set of
servers for continuing the operation. A server MUST
NOT return any
SearchResultReference if it has not located the baseObject
and
thus has not searched any entries; in this case it would
return a
SearchResultDone containing a referral resultCode.
In the absence of indexing information provided to a server
from
servers holding subordinate naming contexts, SearchResultReference
responses are not affected by search filters and are always
returned
when in scope.
The SearchResultReference is of the same data type as the
Referral.
URLs for servers implementing the LDAP protocol are written
according
to [9]. The <dn> part MUST be present in the
URL, with the new target
object name. The client MUST use this name in its
next request.
Some servers (e.g. part of a distributed index exchange
system) may
provide a different filter in the URLs of the SearchResultReference.
If the filter part of the URL is present in an LDAP URL,
the client
MUST use the new filter in its next request to progress
the search,
and if the filter part is absent the client will use again
the same
filter. Other aspects of the new search request
may be the same or
different as the search which generated the continuation
references.
Other kinds of URLs may be returned so long as the operation
could be
performed using that protocol.
The name of an unexplored subtree in a SearchResultReference
need not
be subordinate to the base object.
In order to complete the search, the client MUST issue
a new search
operation for each SearchResultReference that is returned.
Note that
the abandon operation described in section 4.11 applies
only to a
particular operation sent on a connection between a client
and server,
and if the client has multiple outstanding search operations
to
different servers, it MUST abandon each operation individually.
4.5.3.1. Example
For example, suppose the contacted server (hosta) holds
the entry
"O=MNN,C=WW" and the entry "CN=Manager,O=MNN,C=WW".
It knows that
either LDAP-capable servers (hostb) or (hostc) hold
"OU=People,O=MNN,C=WW" (one is the master and the other
server a
Wahl, et. al. Standards Track [Page 31]
RFC 2251
LDAPv3
December 1997
shadow), and that LDAP-capable server (hostd) holds the
subtree
"OU=Roles,O=MNN,C=WW". If a subtree search of "O=MNN,C=WW"
is
requested to the contacted server, it may return the following:
SearchResultEntry for O=MNN,C=WW
SearchResultEntry for CN=Manager,O=MNN,C=WW
SearchResultReference {
ldap://hostb/OU=People,O=MNN,C=WW
ldap://hostc/OU=People,O=MNN,C=WW
}
SearchResultReference {
ldap://hostd/OU=Roles,O=MNN,C=WW
}
SearchResultDone (success)
Client implementors should note that when following a
SearchResultReference, additional SearchResultReference
may be
generated. Continuing the example, if the client
contacted the
server (hostb) and issued the search for the subtree
"OU=People,O=MNN,C=WW", the server might respond as follows:
SearchResultEntry for OU=People,O=MNN,C=WW
SearchResultReference {
ldap://hoste/OU=Managers,OU=People,O=MNN,C=WW
}
SearchResultReference {
ldap://hostf/OU=Consultants,OU=People,O=MNN,C=WW
}
SearchResultDone (success)
If the contacted server does not hold the base object for
the search,
then it will return a referral to the client. For
example, if the
client requests a subtree search of "O=XYZ,C=US" to hosta,
the server
may return only a SearchResultDone containing a referral.
SearchResultDone (referral) {
ldap://hostg/
}
4.6. Modify Operation
The Modify Operation allows a client to request that a
modification
of an entry be performed on its behalf by a server.
The Modify
Request is defined as follows:
ModifyRequest ::= [APPLICATION
6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
Wahl, et. al. Standards Track [Page 32]
RFC 2251
LDAPv3
December 1997
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::=
SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Modify Request are:
- object: The object to be modified. The value of this
field contains
the DN of the entry to be modified.
The server will not perform
any alias dereferencing in determining the
object to be modified.
- modification: A list of modifications to be performed
on the entry.
The entire list of entry modifications MUST
be performed
in the order they are listed, as a single
atomic operation. While
individual modifications may violate the directory
schema, the
resulting entry after the entire list of modifications
is performed
MUST conform to the requirements of the directory
schema. The
values that may be taken on by the 'operation'
field in each
modification construct have the following
semantics respectively:
add: add values listed to the given attribute, creating
the attribute if necessary;
delete: delete values listed from the given attribute,
removing the entire attribute if no values are listed, or
if all current values of the attribute are listed for
deletion;
replace: replace all existing values of the given attribute
with the new values listed, creating the attribute if it
did not already exist. A replace with no value will delete
the entire attribute if it exists, and is ignored if the
attribute does not exist.
The result of the modify attempted by the server upon receipt
of a
Modify Request is returned in a Modify Response, defined
as follows:
ModifyResponse ::= [APPLICATION 7] LDAPResult
Upon receipt of a Modify Request, a server will perform
the necessary
modifications to the DIT.
Wahl, et. al. Standards Track [Page 33]
RFC 2251
LDAPv3
December 1997
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.
If an equality match filter has not been defined for an
attribute type,
clients MUST NOT attempt to delete individual values of
that attribute
from an entry using the "delete" form of a modification,
and MUST
instead use the "replace" form.
Note that due to the simplifications made in LDAP, there
is not a
direct mapping of the modifications in an LDAP ModifyRequest
onto the
EntryModifications of a DAP ModifyEntry operation, and
different
implementations of LDAP-DAP gateways may use different
means of
representing the change. If successful, the final
effect of the
operations on the entry MUST be identical.
4.7. Add Operation
The Add Operation allows a client to request the addition
of an entry
into the directory. The Add Request is defined as follows:
AddRequest ::= [APPLICATION
8] SEQUENCE {
entry LDAPDN,
attributes AttributeList }
AttributeList ::= SEQUENCE
OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
Parameters of the Add Request are:
- entry: the Distinguished Name of the entry to be added.
Note that
the server will not dereference any aliases
in locating the entry
to be added.
Wahl, et. al. Standards Track [Page 34]
RFC 2251
LDAPv3
December 1997
- attributes: the list of attributes that make up the content
of the
entry being added. Clients MUST include
distinguished values
(those forming the entry's own RDN) in this
list, the objectClass
attribute, and values of any mandatory attributes
of the listed
object classes. Clients MUST NOT supply
the createTimestamp or
creatorsName attributes, since these will
be generated
automatically by the server.
The entry named in the entry field of the AddRequest MUST
NOT exist
for the AddRequest to succeed. The parent of the
entry to be added
MUST exist. For example, if the client attempted
to add
"CN=JS,O=Foo,C=US", the "O=Foo,C=US" entry did not exist,
and the
"C=US" entry did exist, then the server would return the
error
noSuchObject with the matchedDN field containing "C=US".
If the
parent entry exists but is not in a naming context held
by the
server, the server SHOULD return a referral to the server
holding the
parent entry.
Servers implementations SHOULD NOT restrict where entries
can be
located in the directory. Some servers MAY allow
the administrator
to restrict the classes of entries which can be added
to the
directory.
Upon receipt of an Add Request, a server will attempt to
perform the
add requested. The result of the add attempt will
be returned to the
client in the Add Response, defined as follows:
AddResponse ::= [APPLICATION 9] LDAPResult
A response of success indicates that the new entry is present
in the
directory.
4.8. Delete Operation
The Delete Operation allows a client to request the removal
of an
entry from the directory. The Delete Request is defined
as follows:
DelRequest ::= [APPLICATION 10] LDAPDN
The Delete Request consists of the Distinguished Name of
the entry to
be deleted. Note that the server will not dereference
aliases while
resolving the name of the target entry to be removed,
and that only
leaf entries (those with no subordinate entries) can be
deleted with
this operation.
The result of the delete attempted by the server upon receipt
of a
Delete Request is returned in the Delete Response, defined
as
follows:
Wahl, et. al. Standards Track [Page 35]
RFC 2251
LDAPv3
December 1997
DelResponse ::= [APPLICATION 11] LDAPResult
Upon receipt of a Delete Request, a server will attempt
to perform
the entry removal requested. The result of the delete
attempt will be
returned to the client in the Delete Response.
4.9. Modify DN Operation
The Modify DN Operation allows a client to change the leftmost
(least
significant) component of the name of an entry in the
directory, or
to move a subtree of entries to a new location in the
directory. The
Modify DN Request is defined as follows:
ModifyDNRequest ::= [APPLICATION
12] SEQUENCE {
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.
- newrdn: the RDN that will form the leftmost component
of the new
name of the entry.
- deleteoldrdn: a boolean parameter that controls whether
the old RDN
attribute values are to be retained as attributes
of the entry, or
deleted from the entry.
- newSuperior: if present, this is the Distinguished Name
of the entry
which becomes the immediate superior of the
existing entry.
The result of the name change attempted by the server upon
receipt of
a Modify DN Request is returned in the Modify DN Response,
defined
as follows:
ModifyDNResponse ::= [APPLICATION 13] LDAPResult
Upon receipt of a ModifyDNRequest, a server will attempt
to
perform the name change. The result of the name change
attempt will
be returned to the client in the Modify DN Response.
For example, if the entry named in the "entry" parameter
was
"cn=John Smith,c=US", the newrdn parameter was "cn=John
Cougar Smith",
and the newSuperior parameter was absent, then this operation
would
Wahl, et. al. Standards Track [Page 36]
RFC 2251
LDAPv3
December 1997
attempt to rename the entry to be "cn=John Cougar Smith,c=US".
If
there was already an entry with that name, the operation
would fail
with error code entryAlreadyExists.
If the deleteoldrdn parameter is TRUE, the values forming
the old
RDN are deleted from the entry. If the deleteoldrdn
parameter is
FALSE, the values forming the old RDN will be retained
as
non-distinguished attribute values of the entry.
The server may
not perform the operation and return an error code if
the setting of
the deleteoldrdn parameter would cause a schema inconsistency
in the
entry.
Note that X.500 restricts the ModifyDN operation to only
affect
entries that are contained within a single server.
If the LDAP
server is mapped onto DAP, then this restriction will
apply, and the
resultCode affectsMultipleDSAs will be returned if this
error
occurred. In general clients MUST NOT expect to
be able to perform
arbitrary movements of entries and subtrees between servers.
4.10. Compare Operation
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.
- ava: the assertion with which an attribute in the entry
is to be
compared.
The result of the compare attempted by the server upon
receipt of a
Compare Request is returned in the Compare Response, defined
as
follows:
CompareResponse ::= [APPLICATION 15] LDAPResult
Upon receipt of a Compare Request, a server will attempt
to perform
the requested comparison. The result of the comparison
will be
returned to the client in the Compare Response. Note that
errors and
the result of comparison are all returned in the same
construct.
Wahl, et. al. Standards Track [Page 37]
RFC 2251
LDAPv3
December 1997
Note that some directory systems may establish access controls
which
permit the values of certain attributes (such as userPassword)
to be
compared but not read. In a search result, it may
be that an
attribute of that type would be returned, but with an
empty set of
values.
4.11. Abandon Operation
The function of the Abandon Operation is to allow a client
to request
that the server abandon an outstanding operation.
The Abandon
Request is defined as follows:
AbandonRequest ::= [APPLICATION 16] MessageID
The MessageID MUST be that of a an operation which was
requested
earlier in this connection.
(The abandon request itself has its own message id.
This is distinct
from the id of the earlier operation being abandoned.)
There is no response defined in the Abandon Operation.
Upon
transmission of an Abandon Operation, a client may expect
that the
operation identified by the Message ID in the Abandon
Request has
been abandoned. In the event that a server receives an
Abandon
Request on a Search Operation in the midst of transmitting
responses
to the search, that server MUST cease transmitting entry
responses to
the abandoned request immediately, and MUST NOT send the
SearchResponseDone. Of course, the server MUST ensure
that only
properly encoded LDAPMessage PDUs are transmitted.
Clients MUST NOT send abandon requests for the same operation
multiple times, and MUST also be prepared to receive results
from
operations it has abandoned (since these may have been
in transit
when the abandon was requested).
Servers MUST discard abandon requests for message IDs they
do not
recognize, for operations which cannot be abandoned, and
for
operations which have already been abandoned.
4.12. Extended Operation
An extension mechanism has been added in this version of
LDAP, in
order to allow additional operations to be defined for
services not
available elsewhere in this protocol, for instance digitally
signed
operations and results.
Wahl, et. al. Standards Track [Page 38]
RFC 2251
LDAPv3
December 1997
The extended operation allows clients to make requests
and receive
responses with predefined syntaxes and semantics.
These may be
defined in RFCs or be private to particular implementations.
Each
request MUST have a unique OBJECT IDENTIFIER assigned
to it.
ExtendedRequest ::= [APPLICATION
23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
The requestName is a dotted-decimal representation of the
OBJECT
IDENTIFIER corresponding to the request. The requestValue
is
information in a form defined by that request, encapsulated
inside an
OCTET STRING.
The server will respond to this with an LDAPMessage containing
the
ExtendedResponse.
ExtendedResponse ::= [APPLICATION
24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING
OPTIONAL }
If the server does not recognize the request name, it MUST
return
only the response fields from LDAPResult, containing the
protocolError result code.
5. Protocol Element Encodings and Transfer
One underlying service is defined here. Clients and
servers SHOULD
implement the mapping of LDAP over TCP described in 5.2.1.
5.1. Mapping Onto BER-based Transport Services
The protocol elements of LDAP are encoded for exchange
using the
Basic Encoding Rules (BER) [11] of ASN.1 [3]. 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".
Wahl, et. al. Standards Track [Page 39]
RFC 2251
LDAPv3
December 1997
(4) If a value of a type is its default value, it MUST
be absent.
Only some BOOLEAN and INTEGER
types have default values in this
protocol definition.
These restrictions do not apply to ASN.1 types encapsulated
inside of
OCTET STRING values, such as attribute values, unless
otherwise
noted.
5.2. Transfer Protocols
This protocol is designed to run over connection-oriented,
reliable
transports, with all 8 bits in an octet being significant
in the data
stream.
5.2.1. Transmission Control Protocol (TCP)
The LDAPMessage PDUs are mapped directly onto the TCP bytestream.
It
is recommended that server implementations running over
the TCP MAY
provide a protocol listener on the assigned port, 389.
Servers may
instead provide a listener on a different port number.
Clients MUST
support contacting servers on any valid TCP port.
6. Implementation Guidelines
This document describes an Internet protocol.
6.1. Server Implementations
The server MUST be capable of recognizing all the mandatory
attribute
type names and implement the syntaxes specified in [5].
Servers MAY
also recognize additional attribute type names.
6.2. Client Implementations
Clients which request referrals MUST ensure that they do
not loop
between servers. They MUST NOT repeatedly contact the
same server for
the same request with the same target entry name, scope
and filter.
Some clients may be using a counter that is incremented
each time
referral handling occurs for an operation, and these kinds
of clients
MUST be able to handle a DIT with at least ten layers
of naming
contexts between the root and a leaf entry.
In the absence of prior agreements with servers, clients
SHOULD NOT
assume that servers support any particular schemas beyond
those
referenced in section 6.1. Different schemas can have
different
attribute types with the same names. The client
can retrieve the
subschema entries referenced by the subschemaSubentry
attribute in
the server's root DSE or in entries held by the server.
Wahl, et. al. Standards Track [Page 40]
RFC 2251
LDAPv3
December 1997
7. Security Considerations
When used with a connection-oriented transport, this version
of the
protocol provides facilities for the LDAP v2 authentication
mechanism, simple authentication using a cleartext password,
as well
as any SASL mechanism [12]. SASL allows for integrity
and privacy
services to be negotiated.
It is also permitted that the server can return its credentials
to
the client, if it chooses to do so.
Use of cleartext password is strongly discouraged where
the
underlying transport service cannot guarantee confidentiality
and may
result in disclosure of the password to unauthorized parties.
When used with SASL, it should be noted that the name field
of the
BindRequest is not protected against modification.
Thus if the
distinguished name of the client (an LDAPDN) is agreed
through the
negotiation of the credentials, it takes precedence over
any value in
the unprotected name field.
Implementations which cache attributes and entries obtained
via LDAP
MUST ensure that access controls are maintained if that
information
is to be provided to multiple clients, since servers may
have access
control policies which prevent the return of entries or
attributes in
search results except to particular authenticated clients.
For
example, caches could serve result information only to
the client
whose request caused it to be cache.
8. Acknowledgements
This document is an update to RFC 1777, by Wengyik Yeong,
Tim Howes,
and Steve Kille. Design ideas included in this document
are based on
those discussed in ASID and other IETF Working Groups.
The
contributions of individuals in these working groups is
gratefully
acknowledged.
9. Bibliography
[1] ITU-T Rec. X.500, "The Directory: Overview of Concepts,
Models
and Service", 1993.
[2] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory
Access
Protocol", RFC 1777, March 1995.
[3] ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1)
-
Specification of Basic Notation",
1994.
Wahl, et. al. Standards Track [Page 41]
RFC 2251
LDAPv3
December 1997
[4] Kille, S., Wahl, M., and T. Howes, "Lightweight Directory
Access
Protocol (v3): UTF-8 String Representation
of Distinguished
Names", RFC 2253, December 1997.
[5] Wahl, M., Coulbeck, A., Howes, T., and S. Kille, "Lightweight
Directory Access Protocol (v3):
Attribute Syntax Definitions",
RFC 2252, December 1997.
[6] ITU-T Rec. X.501, "The Directory: Models", 1993.
[7] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
Resource Locators (URL)",
RFC 1738, December 1994.
[8] ITU-T Rec. X.511, "The Directory: Abstract Service
Definition",
1993.
[9] Howes, T., and M. Smith, "The LDAP URL Format", RFC
2255,
December 1997.
[10] Bradner, S., "Key words for use in RFCs to Indicate
Requirement
Levels", RFC 2119, March
1997.
[11] ITU-T Rec. X.690, "Specification of ASN.1 encoding
rules: Basic,
Canonical, and Distinguished
Encoding Rules", 1994.
[12] Meyers, J., "Simple Authentication and Security Layer",
RFC 2222, October 1997.
[13] Universal Multiple-Octet Coded Character Set (UCS)
-
Architecture and Basic Multilingual
Plane, ISO/IEC 10646-1 :
1993.
[14] Yergeau, F., "UTF-8, a transformation format of Unicode
and ISO
10646", RFC 2044, October
1996.
10. Authors' Addresses
Mark Wahl
Critical Angle Inc.
4815 W Braker Lane #502-385
Austin, TX 78759
USA
Phone: +1 512 372-3160
EMail: M.Wahl@critical-angle.com
Wahl, et. al. Standards Track [Page 42]
RFC 2251
LDAPv3
December 1997
Tim Howes
Netscape Communications Corp.
501 E. Middlefield Rd., MS MV068
Mountain View, CA 94043
USA
Phone: +1 650 937-3419
EMail: howes@netscape.com
Steve Kille
Isode Limited
The Dome, The Square
Richmond
TW9 1DT
UK
Phone: +44-181-332-9091
EMail: S.Kille@isode.com
Wahl, et. al. Standards Track [Page 43]
RFC 2251
LDAPv3
December 1997
Appendix A - Complete ASN.1 Definition
Lightweight-Directory-Access-Protocol-V3
DEFINITIONS
IMPLICIT TAGS ::=
BEGIN
LDAPMessage ::= SEQUENCE
{
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse },
controls [0] Controls OPTIONAL }
MessageID ::= INTEGER (0 .. maxInt)
maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --
LDAPString ::= OCTET STRING
LDAPOID ::= OCTET STRING
LDAPDN ::= LDAPString
RelativeLDAPDN ::= LDAPString
AttributeType ::= LDAPString
AttributeDescription ::=
LDAPString
Wahl, et. al. Standards Track [Page 44]
RFC 2251
LDAPv3
December 1997
AttributeDescriptionList
::= SEQUENCE OF
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), -- new
adminLimitExceeded
(11), -- new
unavailableCriticalExtension (12), -- new
confidentialityRequired (13), -- new
saslBindInProgress
(14), -- new
noSuchAttribute
(16),
undefinedAttributeType (17),
inappropriateMatching (18),
constraintViolation
(19),
attributeOrValueExists (20),
invalidAttributeSyntax (21),
-- 22-31 unused --
noSuchObject
(32),
aliasProblem
(33),
invalidDNSyntax
(34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
Wahl, et. al. Standards Track [Page 45]
RFC 2251
LDAPv3
December 1997
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), -- new
-- 72-79 unused --
other
(80) },
-- 81-90 reserved for APIs --
matchedDN LDAPDN,
errorMessage LDAPString,
referral [3] Referral OPTIONAL
}
Referral ::= SEQUENCE OF LDAPURL
LDAPURL ::= LDAPString -- limited to characters permitted in URLs
Controls ::= SEQUENCE OF Control
Control ::= SEQUENCE {
controlType
LDAPOID,
criticality
BOOLEAN DEFAULT FALSE,
controlValue
OCTET STRING OPTIONAL }
BindRequest ::= [APPLICATION
0] SEQUENCE {
version
INTEGER (1 .. 127),
name
LDAPDN,
authentication AuthenticationChoice
}
AuthenticationChoice ::=
CHOICE {
simple
[0] OCTET STRING,
-- 1 and 2 reserved
sasl
[3] SaslCredentials }
SaslCredentials ::= SEQUENCE
{
mechanism
LDAPString,
credentials
OCTET STRING OPTIONAL }
BindResponse ::= [APPLICATION
1] SEQUENCE {
Wahl, et. al. Standards Track [Page 46]
RFC 2251
LDAPv3
December 1997
COMPONENTS OF LDAPResult,
serverSaslCreds [7] OCTET STRING OPTIONAL }
UnbindRequest ::= [APPLICATION 2] NULL
SearchRequest ::= [APPLICATION
3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED
{
baseObject
(0),
singleLevel
(1),
wholeSubtree
(2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways
(3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and
[0] SET OF Filter,
or
[1] SET OF Filter,
not
[2] Filter,
equalityMatch [3] AttributeValueAssertion,
substrings [4] SubstringFilter,
greaterOrEqual [5] AttributeValueAssertion,
lessOrEqual [6] AttributeValueAssertion,
present [7] AttributeDescription,
approxMatch [8] AttributeValueAssertion,
extensibleMatch [9] MatchingRuleAssertion }
SubstringFilter ::= SEQUENCE
{
type
AttributeDescription,
-- at least one must be present
substrings SEQUENCE OF CHOICE {
initial [0] LDAPString,
any [1] LDAPString,
final [2] LDAPString } }
MatchingRuleAssertion ::=
SEQUENCE {
matchingRule [1] MatchingRuleId OPTIONAL,
type
[2] AttributeDescription OPTIONAL,
matchValue [3] AssertionValue,
dnAttributes [4] BOOLEAN DEFAULT FALSE }
Wahl, et. al. Standards Track [Page 47]
RFC 2251
LDAPv3
December 1997
SearchResultEntry ::= [APPLICATION
4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::=
SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
SearchResultDone ::= [APPLICATION 5] LDAPResult
ModifyRequest ::= [APPLICATION
6] SEQUENCE {
object LDAPDN,
modification SEQUENCE OF SEQUENCE {
operation ENUMERATED {
add (0),
delete (1),
replace (2) },
modification AttributeTypeAndValues } }
AttributeTypeAndValues ::=
SEQUENCE {
type AttributeDescription,
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
Wahl, et. al. Standards Track [Page 48]
RFC 2251
LDAPv3
December 1997
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
Wahl, et. al. Standards Track [Page 49]
RFC 2251
LDAPv3
December 1997
Full Copyright Statement
Copyright (C) The Internet Society (1997). All Rights Reserved.
This document and translations of it may be copied and
furnished to
others, and derivative works that comment on or otherwise
explain it
or assist in its implementation may be prepared, copied,
published
and distributed, in whole or in part, without restriction
of any
kind, provided that the above copyright notice and this
paragraph are
included on all such copies and derivative works.
However, this
document itself may not be modified in any way, such as
by removing
the copyright notice or references to the Internet Society
or other
Internet organizations, except as needed for the purpose
of
developing Internet standards in which case the procedures
for
copyrights defined in the Internet Standards process must
be
followed, or as required to translate it into languages
other than
English.
The limited permissions granted above are perpetual and
will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided
on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Wahl, et. al.
Standards Track
[Page 50]