One document matched: draft-zeilenga-ldapv3bis-rfc2251-00.txt
INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Standard Track OpenLDAP Foundation
Expires: 4 January 2001 4 July 2000
LDAPv3bis Suggestions:
Lightweight Directory Access Protocol (v3)
<draft-zeilenga-ldapv3bis-rfc2251-00.txt>
Status of Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as a Standard Track document.
Distribution of this memo is unlimited. Technical discussion of this
document will take place on the IETF LDAP Extension Working Group
mailing list <ietf-ldapext@netscape.com>. Please send editorial
comments directly to the author <Kurt@OpenLDAP.org>.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft
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Copyright 2000, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
more information.
Forward
This Internet Draft suggests a number of updates to "Lightweight
Directory Access Protocol (v3)" [RFC2251]. This document is not
intended to be published as an RFC but used to identify LDAPv3bis work
items.
The remainer of this documents incorporates the substantive portion of
RFC 2251 text (less status of memo, appendices, etc). Comments and
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suggested updates to this text are inserted as inline notes prefixed
with '//'.
// Start RFC-2251 text
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.
// Note that LDAPv3 and LDAPv2 are cannot generally coexist
// in the real world due to inconsistent implementation of
// LDAPv2 (in particular, character set requirements).
- Most protocol data elements can be encoded as ordinary strings
(e.g., Distinguished Names).
- Referrals to other servers may be returned.
// s/servers/directory servers or services/
- 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
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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.
// note that this offloading is increases the complexity of clients
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.
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// This section could be moved to a separate document which more
// fully described the data model used by LDAP as well as pointing
// out differences between the LDAP and X.500 data models.
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
// suggest using DC naming to promote DNS based service location
// uid=jdoe, dc=Example, dc=COM
// as no global infrastructure exists to support geopolitical naming
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.
// a non-empty set ...
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).
// Attributes can have multiple names:
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// s/a short descriptive name/short descriptive names/
// These names are not globally unique. Suggest replace with:
// The attribute is identified by an OID (object identifier) but
// usually referred to by one of the attributes types short
// descriptive names.
The attribute type governs whether there can be more than one value of
an attribute of that type in an entry, the syntax to which the values
must conform, the kinds of matching which can be performed on values
of that attribute, and other functions.
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").
// s/bar.com/example.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.
// system and user?
// Suggest s/system and user schema/the controlling/
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.
// Does this require the server to modify the value of
// objectClass to include superclasses such that when
// entry is later returned with complete list?
Some attributes, termed operational attributes, are used by servers
for administering the directory system itself. They are not returned
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in search results unless explicitly requested by name. Attributes
// s/requested by name/requested/
// per zeilenga-ldapv3bis-opattrs I-D
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.
// The clause "will have their schema and syntax constraints
// enforced by servers" in this sentence, it implies that
// operational attributes don't have to conform to schema
// and syntax constraints. Suggest the clause be
// from this sentence and an additional sentence be added:
// "The server shall enforce schema and syntax constraints
// upon all attribute types."
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.
// s/permits all user attributes/permits all defined user attributes/
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:
- 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
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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.
// Are not all servers are required to implemented X.500(93)
// models per 3.3?
LDAP clients SHOULD NOT assume that servers implement any of the other
aspects of X.500 subschema.
// Which aspects of the X.500 subschema may clients assume servers
// implement?
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 above should be reworded such that all servers SHOULD publish
// subschema for readable entries and MUST publish subschema for
// all entries which may be updated.
// Insert formal specification for objectclass subschema here or
// in related RFC.
// Address differences between objectclass subentry and
// LDAPSubentry. Address entry (or subentry) issues.
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.
// s/MUST/SHOULD/ to allow servers to avoid naming conflicts
- 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
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type known to the server.
These are defined in [5]. Other attributes MAY be present in subschema
entries, to reflect additional supported capabilities.
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.)
// Additional information should be added clarifying how to
// locate the subschema subentry controlling an existing entry:
// by examining the subschemaSubentry attribute of the entry
// locate the subschema subentry which would control an
// newly added entry
// by examining the subschemaSubentry attribute of the entry
// at the root of the naming context.
// Additionally,
// no mechanism is obtaining necessary subschema for
// creating the entry at the root of a naming context.
// (chicken and egg problem)
// Additionally, a client MUST NOT assume the subschemaSubentry
// value applies to any entry other than the Root DSE itself.
// See notes regarding Root DSE subschemaSubentry below.
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.
// s/MUST/SHOULD/
//
// a) The above requirement is ambiguous (all X.500 rec.?)
// b) The above requirement is too limiting (disallows servers
// from using X.500(1997) recommendations)
// c) The above requirement is not necessary to ensure
// interoperability between protocol peers (per RFC 2119).
// d) This MUST takes precedence over any SHOULD or MAY in
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// this or other LDAPv3 specification.
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.
// This paragraph appears to allow variance in contraction to
// the above MUST. Suggest this section be reworded to allow
// this protocol to be used with a wide range of directory
// systems as long as the LDAP interface is not violated.
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=*)",
// which objectclass(es) are present? if no objectclass,
// then client should use an filter which always evaluates
// to true.
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.
// Many of attributes contained within the root DSE are
// operational and hence only returned if requested.
//
// Servers SHOULD support compare operations upon attributes
// of the root DSE.
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].
// naming contexts were defined above in 3.2.
- subschemaSubentry: subschema entries (or subentries) known by this
server.
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// To allow publication of location of subschema entry controlling
// root DSE itself and to conform to attribute type's syntax
// (single valued) replace above with:
// - subschemaSubentry: subschema entry (or subentry) controlling
// the root DSE.
// See note above regarding locating controlling subschema
- altServer: alternative servers in case this one is later
unavailable.
- supportedExtension: list of supported extended operations.
- supportedControl: list of supported controls.
- supportedSASLMechanisms: list of supported SASL security features.
// s/security features/mechanisms/
- 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.
// This paragraph suggests a mechanism for schema discovery
// which:
// 1) disallows discovery of the root DSE controlling schema
// 2) violates the constraints upon subschemaSubentry
// 3) is inadequate (only works if DSA has single subschema
// which applies to all entries).
//
// Suggest the above paragraph be replaced with:
//
// -- subschemaSubentry: the DN of the entry (or subentry)
// containing the subschema which controls the root DSE
// itself.
//
// Note: Clients should use the mechanism described in X.Y
// to for locating controlling subschema of other entries.
//
// (as described above).
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
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Basic Encoding Rules [11].
// typically? The protocol is transferred using the subset
// of BER known as the Data Encoding Rules. (or does this
// belong below).
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.
// or provide a root DSE.
4.1. Common Elements
This section describes the LDAPMessage envelope PDU (Protocol Data
Unit) format, as well as data type definitions which are used in the
protocol operations.
4.1.1. Message Envelope
For the purposes of protocol exchanges, all protocol operations are
encapsulated in a common envelope, the LDAPMessage, which is defined
as follows:
LDAPMessage ::= SEQUENCE {
messageID MessageID,
protocolOp CHOICE {
bindRequest BindRequest,
bindResponse BindResponse,
unbindRequest UnbindRequest,
searchRequest SearchRequest,
searchResEntry SearchResultEntry,
searchResDone SearchResultDone,
searchResRef SearchResultReference,
modifyRequest ModifyRequest,
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modifyResponse ModifyResponse,
addRequest AddRequest,
addResponse AddResponse,
delRequest DelRequest,
delResponse DelResponse,
modDNRequest ModifyDNRequest,
modDNResponse ModifyDNResponse,
compareRequest CompareRequest,
compareResponse CompareResponse,
abandonRequest AbandonRequest,
extendedReq ExtendedRequest,
extendedResp ExtendedResponse },
// Added ExtendedPartialResponse
// Add note below that this CHOICE may be extended.
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.
4.1.1.1. Message ID
All LDAPMessage envelopes encapsulating responses contain the
messageID value of the corresponding request LDAPMessage.
// Add:
// Unsolicited notifications, as defined in section 4.4,
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// MUST have a zero valued message ID.
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.
// s/a value/a non-zero value/
// a zero value request would generate responses which cannot
// easily be distinguished from unsolicited notifications.
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.
// This implies that a server must defer responding to requests
// received after an abandon request until after it processed
// the abandon request (or completed the operation to be
// abandon).
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
// s/byte/octet
byte values are used to form a variable-length encoding of an
// s/byte/octet
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.
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// A formal, definitive specification for the dotted-decimal
// representation should be provided here and then referenced
// as needed below and in related documents.
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
<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".
// refer to formal dotted-decimal spec.
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
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0x7F.)
// s/byte/octet/
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.
// Given that textual names are non-unique, a server MUST be allowed
// to respond with a OID of the attribute type where it's names are
// known to non-unique in the controlling subschema. OR require
// names of schema elements must be unique within a particular
// subschema.
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.
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
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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.
// s/will/MUST/
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
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.
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// nor expect the attribute to be returned in string format...
// Suggest adding: Servers SHOULD only return attributes with
// printable string representations as binary if client
// requested binary transfer.
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.
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
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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.
// Does string-valued mean a value of DirectoryString,
// PrintableString, IA5 String syntax or does it mean a value
// with any string representation? If the latter, the above
// is not true for syntaxes such attributes with equality
// rules such as objectIdentifierFirstComponentMatch.
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.
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".
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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 --
noSuchObject (32),
aliasProblem (33),
invalidDNSyntax (34),
-- 35 reserved for undefined isLeaf --
aliasDereferencingProblem (36),
-- 37-47 unused --
inappropriateAuthentication (48),
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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.
// The result codes list above other than success, compareTrue,
// compareFalse, and referral indicate an error has occurred.
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.
// Add:
// Servers SHOULD NOT generate codes 81-90 as these are reserved
// for use by historical APIs [RFC 1823]. Later API specifications
// should avoid using resultCode enumeration to represent anything
// other than a protocol result indication. API errors are not
// protocol results.
// Extensions to this protocol MAY add additional result codes.
If a client receives a result code which is not listed above, it is to
be treated as an unknown error condition.
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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,
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.
// The errorMessage field SHOULD be a zero length string if
// the resultCode does not indicate an error.
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.
// ... listed above. That is, resultCodes not listed above MAY
// allow matchedDN to be non zero length.
4.1.11. Referral
The referral error indicates that the contacted server does not hold
the target entry of the request.
// s/error/resultCode/ a referral is not an error.
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.
// Note that RFC2255 URL describe only search operations. A
// clarification to 2255 is needed to allow this use.
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
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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 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.
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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.
// s/unsupportedCriticalExtension/unavailableCriticalExtension/
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.
// s/unsupportedCriticalExtension/unavailableCriticalExtension/
If the control is unrecognized or inappropriate but the criticality
field is FALSE, the server MUST ignore the control.
The controlValue contains any information associated with the control,
and its format is defined for the control. 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
// s/bytes/octets
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.
// Add:
// Servers SHOULD avoid sending controls unless they know (by
// solicitation or other means) the client would recognize and
// make use of the control.
// Add section on ExtendedPartialResponses
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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-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.
// Last clause requires an LDAPDN when non-LDAP DN authentication
// identities are used with SASL. Should replace "when using SASL
// credentials that include the LDAPDN in the credentials" with
// "when other credentials (e.g. SaslCredentials) are provided."
- 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
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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, the server MUST return a BindResponse with
authMethodNotSupported as the resultCode. This will allow clients to
abort a negotiation if it wishes to try again with the same SASL
mechanism.
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.
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
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support the changing of credentials from one identity to another, then
the client MUST instead establish a new connection.
// s/then/then the server MUST close the connection and/
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.
// Change last sentence: The name field SHOULD also be zero length
// and, if provided, MUST be ignored by the server.
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.
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.
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f the bind was successful, the resultCode will be success, therwise it
will be one of:
// s/^f/If/ s/therwise/otherwise/
// s/will/MAY/
// Other resultCodes, such as "other", "busy", "unwillingToPerform",
// should be allowed.
- operationsError: server encountered an internal error,
// operationsError should not be used for internal errors, use
// other instead.
- 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.)
The serverSaslCreds are used as part of a SASL-defined bind mechanism
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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
// s/password choice/simple choice/
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.
// and MAY close the connection.
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.
// and MUST close the connection.
4.4. Unsolicited Notification
An unsolicited notification is an LDAPMessage sent from the server to
the client which is not in response to any LDAPMessage received by the
server. It is used to signal an extraordinary condition in the server
or in the connection between the client and the server. The
notification is of an advisory nature, and the server will not expect
any response to be returned from the client.
// Add:
// Servers should NOT assume LDAPv3 clients understand or recognize
// implement solicited controls other than Notice of Disconnection
// defined below. Servers SHOULD avoid sending unsolicited
// notifications unless they know (by related request or other
// means) that the client can make use of the notification.
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
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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 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:
// Other result codes should be allowed, such as "busy", "other",
// "confidentialityRequired"
- 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.
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4.5.1. Search Request
The Search Request is defined as follows:
SearchRequest ::= [APPLICATION 3] SEQUENCE {
baseObject LDAPDN,
scope ENUMERATED {
baseObject (0),
singleLevel (1),
wholeSubtree (2) },
derefAliases ENUMERATED {
neverDerefAliases (0),
derefInSearching (1),
derefFindingBaseObj (2),
derefAlways (3) },
sizeLimit INTEGER (0 .. maxInt),
timeLimit INTEGER (0 .. maxInt),
typesOnly BOOLEAN,
filter Filter,
attributes AttributeDescriptionList }
Filter ::= CHOICE {
and [0] SET 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:
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- baseObject: An LDAPDN that is the base object entry relative to
which the search is to be performed.
- scope: An indicator of the scope of the search to be performed. The
semantics of the possible values of this field are identical to the
semantics of the scope field in the X.511 Search Operation.
- derefAliases: An indicator as to how alias objects (as defined in
X.501) are to be handled in searching. The semantics of the
possible values of this field are:
neverDerefAliases: do not dereference aliases in searching
or in locating the base object of the search;
derefInSearching: dereference aliases in subordinates of
the base object in searching, but not in locating the
base object of the search;
derefFindingBaseObj: dereference aliases in locating
the base object of the search, but not when searching
subordinates of the base object;
derefAlways: dereference aliases both in searching and in
locating the base object of the search.
- sizelimit: A 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.
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// one or more filter elements is inconsistent with the
// ASN.1 "SET OF", RFC1777, and X.511(93). It also
// removes the 'true' and 'false' filters created via
// empty sets.
//
// This change is believed to cause no significant protocol
// interoperability problems, but will require a minor change
// to string representation of filters. The change to the
// string representation will likely have an impact upon some
// applications.
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.
A filter of the "and" choice is TRUE if
// empty or
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
// empty or
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
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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.
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).
// merge in "+" changes from zeilenga-ldapv3bis-opattrs
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.
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If the client does not want any attributes returned, it can specify
a list containing only the attribute with OID "1.1". This OID was
chosen 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.
// s/ExtendedResponse/ExtendedPartialResponse/ or
// add ExtendedPartialResponse
SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
objectName LDAPDN,
attributes PartialAttributeList }
PartialAttributeList ::= SEQUENCE OF SEQUENCE {
type AttributeDescription,
vals SET OF AttributeValue }
-- implementors should note that the PartialAttributeList may
-- have zero elements (if none of the attributes of that entry
-- were requested, or could be returned), and that the vals set
-- may also have zero elements (if types only was requested, or
-- all values were excluded from the result.)
SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
-- at least one LDAPURL element must be present
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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.
// implies the server will not return a sequence of responses if
// a connectionless transport is used. Suggest replacing with:
// The server will return to the client a sequence of responses
// in separate LDAP messages which may be intermixed with
// responses of other requests"
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
// and all Extended{Partial}Response 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
// s/ExtendedResponse/ExtendedPartialResponse/ or add partial
returning information associated with a control requested by the
client. These may be defined in future versions of this document.
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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.
// The client SHALL treat any search continuation returned
// in response scope base search as a protocol error and SHALL
// NOT chase them.
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.
// Add:
// If the scope part of the URL is present, the client MUST use
// the new scope in its next request to progress the search and
// if the search scope part is absent the client will use subtree
// scope to complete subtree searches and base scopes to complete
// one level searches.
//
// Note: This is needed for the examples below work.
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.
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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,
// or to the same server
it MUST abandon each operation individually.
4.5.3.1. Example
// Suggest use "dc=example,dc=com" naming in examples
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
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
}
// note that these URL have implicit scope base, hence above
// change URLs without explicitly scope parts.
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
}
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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 {
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:
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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.
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
// s/delete/add or delete/
from an entry using the "delete" form of a modification, and MUST
// s/"delete"/"add" or "delete" (respectively)/
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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.
- 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.
// must not supply NO-USER-MODIFICATION attributes such as
// createTimeStamp or creatorsName. These are provided by
// servers.
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.
// unless the entry is the root entry of a naming context.
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
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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,
// unless the entry is the root entry of 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:
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
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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 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.
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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.
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
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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.
// I believe abandon operations should have responses similar to
// their X.500 counter parts. However, this cannot be added without
// rev'ing to v4.
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.
// What? The client should not expect the requested operation to
// be abandoned upon transmission. It must await a response
// subsequent request.
In the event that a server receives an Abandon Request on a Search
Operation in the midst of transmitting responses to the search, that
server MUST cease transmitting entry responses to the abandoned
request immediately, and MUST NOT send the SearchResponseDone. Of
course, the server MUST ensure that only properly encoded LDAPMessage
PDUs are transmitted.
Clients MUST NOT send abandon requests for the same operation multiple
times, and MUST also be prepared to receive results from operations it
has abandoned (since these may have been in transit when the abandon
was requested).
// Or not original request may not be abandonable
// Abandon and Unbind requests are not abandonable. Other requests,
// in particular some update operations, may not be abandonable (or
// immediately abandonable.
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.
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// StartTLS would be a better for instance.
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.
// reference dotted-decimal spec.
The requestValue is information in a form defined by that request,
encapsulated inside an OCTET STRING.
The server will respond to this with an LDAPMessage containing the
ExtendedResponse.
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
If the server does not recognize the request name, it MUST return only
the response fields from LDAPResult, containing the protocolError
result code.
// 4.xx ExtendedPartialResponses
//
// ExtendedPartialResponse PDU may be returned in response any
// ExtendedRequest specifying their use or any request with a
// control specifying their use. For example, a subtree
// control could be defined (by another document) such that
// operations normally acting upon one entry would act upon
// subtrees and specify extendedPartialResponses be used to
// return responses for each object in the subtree.
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
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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".
(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.
// using the BER-based described in section 5.1.
// s/bytestream/octet stream/
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.
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// Servers should only be required the syntaxes needed to support
// mandatory attribute types.
// Servers which support update operations MUST, and other servers
// SHOULD, support strong authentication mechanisms described in
// RFC 2829.
//
// Servers which provide access to sensitive information MUST,
// and other servers SHOULD support privacy protections such as
// those described in RFC 2829 and RFC 2830.
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.
// replace last sentence with:
// The client can retrieve the controlling subschema of an entry
// by as described in Section X.Y.
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.
// Automatic chasing of referrals poses significant privacy and
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// security concerns.
// Add consideration requiring the use of strong authentication
// to update the directory.
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.
[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.
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[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.
// End of RFC-2251 text
Additional Information
Discussions regarding these suggestions may directed to the author:
Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
or the LDAPext Working Group mailing list:
<ietf-ldapext@netscape.com>
Copyright 2000, The Internet Society. All Rights Reserved.
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are included on all such copies and derivative works. However,
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