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Internet-Draft                                  Editor:  J. Sermersheim
Intended Category: Standard Track                           Novell, Inc
Document: draft-ietf-ldapbis-protocol-06.txt               January 2002
Obsoletes: RFC 2251


                Lightweight Directory Access Protocol (v3)


1. Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of [RFC2026].

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.
   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   Distribution of this memo is unlimited. Technical discussion of this
   document will take place on the IETF LDAP Revision Working Group
   (LDAPbis) mailing list <ietf-ldapbis@openldap.org>. Please send
   editorial comments directly to the editor <jimse@novell.com>.

Table of Contents

   1. Status of this Memo..............................................1
   2. Abstract.........................................................2
   3. Models...........................................................3
   3.1. Protocol Model.................................................3
   3.2. Data Model.....................................................4
   3.2.1. Attributes of Entries........................................4
   3.2.2. Subschema Entries and Subentries.............................6
   3.3. Relationship to X.500..........................................7
   3.4. Server-specific Data Requirements..............................7
   4. Elements of Protocol.............................................8
   4.1. Common Elements................................................8
   4.1.1. Message Envelope.............................................8
   4.1.1.1. Message ID.................................................9
   4.1.2. String Types.................................................9
   4.1.3. Distinguished Name and Relative Distinguished Name..........10
   4.1.4. Attribute Type..............................................10
   4.1.5. Attribute Description.......................................11
   4.1.5.1. Binary Option.............................................13
   4.1.6. Attribute Value.............................................13

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   4.1.7. Attribute Value Assertion...................................14
   4.1.8. Attribute...................................................14
   4.1.9. Matching Rule Identifier....................................15
   4.1.10. Result Message.............................................15
   4.1.11. Referral...................................................17
   4.1.12. Controls...................................................18
   4.2. Bind Operation................................................19
   4.2.1. Sequencing of the Bind Request..............................20
   4.2.2. Authentication and Other Security Services..................21
   4.2.3. Bind Response...............................................21
   4.3. Unbind Operation..............................................22
   4.4. Unsolicited Notification......................................22
   4.4.1. Notice of Disconnection.....................................23
   4.5. Search Operation..............................................23
   4.5.1. Search Request..............................................24
   4.5.2. Search Result...............................................27
   4.5.3. Continuation References in the Search Result................28
   4.6. Modify Operation..............................................30
   4.7. Add Operation.................................................31
   4.8. Delete Operation..............................................32
   4.9. Modify DN Operation...........................................33
   4.10. Compare Operation............................................34
   4.11. Abandon Operation............................................35
   4.12. Extended Operation...........................................35
   5. Protocol Element Encodings and Transfer.........................36
   5.1. Protocol Encoding.............................................36
   5.2. Transfer Protocols............................................36
   5.2.1. Transmission Control Protocol (TCP).........................36
   6. Implementation Guidelines.......................................37
   6.1. Server Implementations........................................37
   6.2. Client Implementations........................................37
   7. Security Considerations.........................................37
   8. Acknowledgements................................................38
   9. Bibliography....................................................38
   10. Editor's Address...............................................39
   Appendix A - Complete ASN.1 Definition.............................40
   Appendix B - Change History........................................45
   B.1 Changes made to RFC 2251:......................................45
   B.2 Changes made to draft-ietf-ldapbis-protocol-00.txt:............45
   B.3 Changes made to draft-ietf-ldapbis-protocol-01.txt:............46
   B.4 Changes made to draft-ietf-ldapbis-protocol-02.txt:............46
   B.5 Changes made to draft-ietf-ldapbis-protocol-03.txt:............48
   B.6 Changes made to draft-ietf-ldapbis-protocol-04.txt:............50
   B.7 Changes made to draft-ietf-ldapbis-protocol-05.txt:............50
   Appendix C - Outstanding Work Items................................50

2. Abstract

   The protocol described in this document is designed to provide access
   to directories supporting the [X.500] models, while not incurring the
   resource requirements of the X.500 Directory Access Protocol (DAP).
   This protocol is specifically targeted at management applications and
   browser applications that provide read/write interactive access to


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   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 [RFC2119].

   Key aspects of this version of LDAP are:

   - All protocol elements of LDAPv2 [RFC1777] are supported. The
     protocol is carried directly over TCP or other transport,
     bypassing much of the session/presentation overhead of X.500 DAP.

   - Most protocol data elements can be encoded as ordinary strings
     (e.g., Distinguished Names).

   - Referrals to other servers may be returned.

   - SASL mechanisms may be used with LDAP to provide association
     security services.

   - Attribute values and Distinguished Names have been
     internationalized through the use of the ISO 10646 character set.

   - The protocol can be extended to support new operations, and
     controls may be used to extend existing operations.

   - Schema is published in the directory to be used by clients.

3. Models

   Interest in X.500 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 LDAPv2 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.

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   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 the core protocol operations defined in this document can
   be mapped to a strict subset of the X.500(1997) directory abstract
   service, so it can be cleanly provided by the DAP. However there is
   not a one-to-one mapping between LDAP protocol operations and DAP
   operations: server implementations acting as a gateway to X.500
   directories may need to make multiple DAP requests.

3.2. Data Model

   This section provides a brief introduction to the X.500 data model,
   as used by LDAP.

   The LDAP protocol assumes there are one or more servers which jointly
   provide access to a Directory Information Tree (DIT). The tree is
   made up of entries. Entries have names: one or more attribute values
   from the entry form its relative distinguished name (RDN), which MUST
   be unique among all its siblings. The concatenation of the relative
   distinguished names of the sequence of entries from a particular
   entry to an immediate subordinate of the root of the tree forms that
   entry's Distinguished Name (DN), which is unique in the tree. An
   example of a Distinguished Name is:

   CN=Steve Kille, O=Isode Limited, C=GB

   Some servers may hold cache or shadow copies of entries, which can be
   used to answer search and comparison queries, but will return
   referrals or contact other servers if modification operations are
   requested.

   Servers that 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



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   Entries consist of a set of attributes. An attribute is a description
   (a type and zero or more options) with one or more associated values.
   The attribute type governs whether the attribute can have multiple
   values, the syntax and matching rules used to construct and compare
   values of that attribute, and other functions. Options indicate modes
   of transfer and other functions.

   An example of an attribute is "mail". There may be one or more values
   of this attribute, they must be IA5 (ASCII) strings, and they are
   case insensitive (e.g. "foo@bar.com" will match "FOO@BAR.COM").

   Schema is the collection of attribute type definitions, object class
   definitions and other information which a server uses to determine
   how to match a filter or attribute value assertion (in a compare
   operation) against the attributes of an entry, and whether to permit
   add and modify operations. The definition of schema for use with LDAP
   is given in [RFC2252] and [X.501]. Additional schema elements may be
   defined in other documents.

   Each entry MUST have an objectClass attribute. The objectClass
   attribute specifies the object classes of an entry, which along with
   the system and user schema determine the permitted attributes of an
   entry. Values of this attribute may be modified by clients, but the
   objectClass attribute cannot be removed. Servers may restrict the
   modifications of this attribute to prevent the basic structural class
   of the entry from being changed (e.g. one cannot change a person into
   a country). When creating an entry or adding an objectClass value to
   an entry, all superclasses of the named classes are implicitly added
   as well if not already present, and the client must supply values for
   any mandatory attributes of new superclasses.

   Some attributes, termed operational attributes (as defined in Section
   12.4.1 of [X.501]), are used by servers for administering the
   directory system itself. They are not returned in search results
   unless explicitly requested by name. Attributes which are not
   operational, such as "mail", will have their schema and syntax
   constraints enforced by servers, but servers will generally not make
   use of their values.

   Servers MUST NOT permit clients to add attributes to an entry unless
   those attributes are permitted by the object class definitions, the
   schema controlling that entry (specified in the subschema รป 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 [RFC2252] which permits all
   user attributes to be present in an entry.

   Entries MAY contain, among others, the following operational
   attributes, defined in [RFC2252]. 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.


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   - createTimestamp: the time this entry was added to the directory.

   - modifiersName: the Distinguished Name of the user who last
     modified this entry.

   - modifyTimestamp: the time this entry was last modified.

   - subschemaSubentry: the Distinguished Name of the subschema entry
     (or subentry) which controls the schema for this entry.

3.2.2. Subschema Entries and Subentries

   Subschema entries are used for administering information about the
   directory schema, in particular the object classes and attribute
   types supported by directory servers. A single subschema entry
   contains all schema definitions used by entries in a particular part
   of the directory tree.

   Servers which follow X.500(93) models SHOULD implement subschema
   using the X.500 subschema mechanisms, and so these subschemas are not
   ordinary entries. LDAP clients SHOULD NOT assume that servers
   implement any of the other aspects of X.500 subschema. A server which
   masters entries and permits clients to modify these entries MUST
   implement and provide access to these subschema entries, so that its
   clients may discover the attributes and object classes which are
   permitted to be present. It is strongly recommended that all other
   servers implement this as well.

   The following four attributes MUST be present in all subschema
   entries:

   - cn: this attribute MUST be used to form the RDN of the subschema
     entry.

   - objectClass: the attribute MUST have at least the values "top" and
     "subschema".

   - objectClasses: each value of this attribute specifies an object
     class known to the server.

   - attributeTypes: each value of this attribute specifies an
     attribute type known to the server.

   These are defined in [RFC2252]. 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.



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   Clients MUST only retrieve attributes from a subschema entry by
   requesting a base object search of the entry, where the search filter
   is "(objectClass=subschema)". This will allow LDAPv3 servers which
   gateway to X.500(93) to detect that subentry information is being
   requested.

3.3. Relationship to X.500

   This document defines LDAP in terms of X.500 as an X.500 access
   mechanism. An LDAP server MUST act in accordance with the X.500(1993)
   series of ITU recommendations when providing the service. However, it
   is not required that an LDAP server make use of any X.500 protocols
   in providing this service, e.g. LDAP can be mapped onto any other
   directory system so long as the X.500 data and service model as used
   in LDAP is not violated in the LDAP interface.

3.4. Server-specific Data Requirements

   An LDAP server MUST provide information about itself and other
   information that is specific to each server. This is represented as a
   group of attributes located in the root DSE (DSA-Specific Entry),
   which is named with the zero-length LDAPDN. These attributes are
   retrievable if a client performs a base object search of the root
   with filter "(objectClass=*)", however they are subject to access
   control restrictions. The root DSE MUST NOT be included if the client
   performs a subtree search starting from the root.

   Servers may allow clients to modify these attributes.

   The following attributes of the root DSE are defined in section 5 of
   [RFC2252]. 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].

   - subschemaSubentry: subschema entry (or subentry) holding the
     schema for the root DSE.

   - 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.

   - 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, the schema for each entry is found by reading the
   subschemaSubentry attribute for that entry.

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4. Elements of Protocol

   The LDAP protocol is described using Abstract Syntax Notation 1
   (ASN.1) [X.680], and is transferred using a subset of ASN.1 Basic
   Encoding Rules [X.690]. In order to support future extensions to this
   protocol, clients and servers MUST ignore elements of SEQUENCE
   encodings whose tags they do not recognize. Section 5.1 specifies how
   the protocol is encoded and transferred.

   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 or later is supported in
   the client (since version 2 required that the client bind first).

   Clients may determine the protocol versions a server supports by
   reading the supportedLDAPVersion attribute from the root DSE. Servers
   which implement version 3 or later versions MUST provide this
   attribute. Servers which only implement version 2 may not provide
   this attribute.

4.1. Common Elements

   This section describes the LDAPMessage envelope PDU (Protocol Data
   Unit) format, as well as data type definitions, which are used in the
   protocol operations.

4.1.1. Message Envelope

   For the purposes of protocol exchanges, all protocol operations are
   encapsulated in a common envelope, the LDAPMessage, which is defined
   as follows:

        LDAPMessage ::= SEQUENCE {
                messageID       MessageID,
                protocolOp      CHOICE {
                        bindRequest     BindRequest,
                        bindResponse    BindResponse,
                        unbindRequest   UnbindRequest,
                        searchRequest   SearchRequest,
                        searchResEntry  SearchResultEntry,
                        searchResDone   SearchResultDone,
                        searchResRef    SearchResultReference,
                        modifyRequest   ModifyRequest,
                        modifyResponse  ModifyResponse,
                        addRequest      AddRequest,
                        addResponse     AddResponse,
                        delRequest      DelRequest,
                        delResponse     DelResponse,
                        modDNRequest    ModifyDNRequest,
                        modDNResponse   ModifyDNResponse,
                        compareRequest  CompareRequest,

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                        compareResponse CompareResponse,
                        abandonRequest  AbandonRequest,
                        extendedReq     ExtendedRequest,
                        extendedResp    ExtendedResponse },
                controls        [0] Controls OPTIONAL }

        MessageID ::= INTEGER (0 .. maxInt)

        maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --

   The function of the LDAPMessage is to provide an envelope containing
   common fields required in all protocol exchanges. At this time the
   only common fields are the message ID and the controls.

   If the server receives a PDU from the client in which the LDAPMessage
   SEQUENCE tag cannot be recognized, the messageID cannot be parsed,
   the tag of the protocolOp is not recognized as a request, or the
   encoding structures or lengths of data fields are found to be
   incorrect, then the server MUST return the notice of disconnection
   described in section 4.4.1, with resultCode protocolError, and
   immediately close the connection. In other cases that the server
   cannot parse the request received by the client, the server MUST
   return an appropriate response to the request, with the resultCode
   set to protocolError.

   If the client receives a PDU from the server, which cannot be parsed,
   the client may discard the PDU, or may abruptly close the connection.

   The ASN.1 type Controls is defined in section 4.1.12.

4.1.1.1. Message ID

   All LDAPMessage envelopes encapsulating responses contain the
   messageID value of the corresponding request LDAPMessage.

   The message ID of a request MUST have a value different from the
   values of any other requests outstanding in the LDAP session of which
   this message is a part.

   A client MUST NOT send a second request with the same message ID as
   an earlier request on the same connection if the client has not
   received the final response from the earlier request. Otherwise the
   behavior is undefined. Typical clients increment a counter for each
   request.

   A client MUST NOT reuse the message id of an abandonRequest or of the
   abandoned operation until it has received a response from the server
   for another request invoked subsequent to the abandonRequest, as the
   abandonRequest itself does not have a response.

4.1.2. String Types

   The LDAPString is a notational convenience to indicate that, although
   strings of LDAPString type encode as OCTET STRING types, the

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   [ISO10646] character set (a superset of Unicode) is used, encoded
   following the UTF-8 algorithm [RFC2044]. Note that in the UTF-8
   algorithm characters which are the same as ASCII (0x0000 through
   0x007F) are represented as that same ASCII character in a single
   byte. The other byte values are used to form a variable-length
   encoding of an arbitrary character.

        LDAPString ::= OCTET STRING

   The LDAPOID is a notational convenience to indicate that the
   permitted value of this string is a (UTF-8 encoded) dotted-decimal
   representation of an OBJECT IDENTIFIER.

        LDAPOID ::= OCTET STRING

   A value of LDAPOID is defined by the following ABNF [RFC2234]:

        ldapOID = number *( DOT number )

        number  = ( LDIGIT *DIGIT ) / DIGIT

        DOT     = %x2E ; "."

        LDIGIT  = %x31-39 ; 1-9

        DIGIT   = %x30 / LDIGIT ; 0-9

   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 [RFC2253], such
   that:

        distinguished-name = name

        relative-distinguished-name = name-component

   where name and name-component are as defined in [RFC2253].

        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


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   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 defined by ldapOID
   in section 4.1.2.

   A specification may also assign one or more textual names for an
   attribute type. These names MUST begin with a letter, and only
   contain ASCII letters, digit characters and hyphens. They are case
   insensitive. These ASCII characters are identical to ISO 10646
   characters whose UTF-8 encoding is a single byte between 0x00 and
   0x7F.

   If the server has a textual name for an attribute type, it MUST use a
   textual name for attributes returned in search results. The dotted-
   decimal OBJECT IDENTIFIER is only used if there is no textual name
   for an attribute type.

   Attribute type textual names are non-unique, as two different
   specifications (neither in standards track RFCs) may choose the same
   name.

   A server which masters or shadows entries SHOULD list all the
   attribute types it supports in the subschema entries, using the
   attributeTypes attribute. Servers which support an open-ended set of
   attributes SHOULD include at least the attributeTypes value for the
   'objectClass' attribute. Clients MAY retrieve the attributeTypes
   value from subschema entries in order to obtain the OBJECT IDENTIFIER
   and other information associated with attribute types.

   Some attribute type names which are used in this version of LDAP are
   described in [RFC2252]. 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. The entire AttributeDescription
   is case insensitive.

        AttributeDescription ::= LDAPString

   A value of AttributeDescription is based on the following ABNF:

        attributeDescription = attributeType options

        attributeType        = AttributeType
                               ; as described in Section 4.1.4

        options              = *( SEMICOLON options )

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        option               = 1*opt-char

        opt-char             = ALPHA / DIGIT / HYPHEN

        SEMICOLON            = %x3B ; ";"

        ALPHA                = %x41-5A / %x61-7A ; A-Z / a-z

        HYPHEN               = %x2D ; "-"

   Examples of valid AttributeDescription:

        cn
        userCertificate;binary

   Not all options can be associated with attributes held in the
   directory. A server will treat an AttributeDescription with any
   options it does not implement as unrecognized. The order in which
   options appear in the list MUST NOT be used to impart any semantic
   meaning. Servers MUST treat any two AttributeDescription with the
   same AttributeType and options as equivalent.

   An attribute description that contains mutually exclusive options
   shall be treated as unrecognized. That is, "cn;binary;gser" (where
   "binary" and "gser" are mutually exclusive) is to be treated as an
   unrecognized attribute.

   There are multiple kinds of attribute description options. The LDAP
   technical specification details two kinds: tagging options (such as
   language tag options) and transfer options (such as ;binary). Other
   documents may detail other kinds.

   Tagging options can be held in the directory and are never mutually
   exclusive. An attribute with N tagging options is considered a direct
   subtype of all attributes of the same type and all but one of the N
   options. If the type has a supertype, then the attribute is also
   considered a direct subtype of the attribute of the supertype and the
   N tagging options. That is, cn;lang_de;lang_en is considered a direct
   subtype of cn;lang_de, cn;lang_en, and name;lang_de;lang_en (cn is a
   subtype of name).

   Transfer options are not held in the directory, they only affect the
   encoding used to transfer values. The absence of a transfer option
   implies the native encoding. Transfer options are mutually exclusive.
   Specifying a transfer option when requesting attributes to be
   returned in a SearchRequest causes that encoding to be used for that
   attribute and its subtypes. That is, requesting name;binary requests
   the attribute name and its subtypes (e.g., cn, sn, cn;lang_en, etc.)
   be returned using binary transfer.

   When specifying return attributes for a SearchRequest, clients SHOULD
   avoid requesting the return of attributes related to each other in
   the attribute subtyping hierarchy with different transfer encodings.

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   For example, requesting name;lang_en;binary and cn should be avoided
   as it ambiguous as to how cn;lang_en is to be transferred. In such
   cases, the server's behavior is undefined (the server can return the
   values in either, neither, or both encodings).

   Other documents may specify other kinds of options. These documents
   must detail how new kinds of options relate to tagging and transfer
   options. In particular, the document must describe how the options
   relation to the attribute subtyping hierarchy.

   One transfer 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.

   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 the native encoding representation defined for that
   attribute in [RFC2252]. Instead the attribute is to be transferred as
   a binary value encoded using the Basic Encoding Rules [X.690]. The
   syntax of the binary value is an ASN.1 data type definition, which is
   referenced by the "SYNTAX" part of the attribute type definition.

   The presence or absence of the "binary" option only affects the
   transfer of attribute values in protocol; servers store any
   particular attribute in a single format. If a client requests that a
   server return an attribute in the binary format, but the server
   cannot generate that format, the server MUST treat this attribute
   type as an unrecognized attribute type. Similarly, clients MUST NOT
   expect servers to return an attribute in binary format if the client
   requested that attribute by name without the "binary" option.

   This option is intended to be used with attributes whose syntax is a
   complex ASN.1 data type, and the structure of values of that type is
   needed by clients. Examples of this kind of syntax are "Certificate"
   and "CertificateList".

4.1.6. Attribute Value

   A field of type AttributeValue is an OCTET STRING containing an
   encoded value of an AttributeValue data type. The value is encoded
   according to its native encoding definition, unless an option
   specifying the transfer encoding is present in the companion
   AttributeDescription to the AttributeValue (e.g. "binary").



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   The native encoding definitions for different syntaxes and attribute
   types may be found in other documents, and in particular [RFC2252].

   At the time of this writing, there is only one AttributeDescription
   option used to specify transfer encoding--"binary", described in
   section 4.1.5.1.

        AttributeValue ::= OCTET STRING

   Note that there is no defined limit on the size of this encoding;
   thus protocol values may include multi-megabyte attributes (e.g.
   photographs).

   Attributes may be defined which have arbitrary and non-printable
   syntax. Implementations MUST NOT display nor attempt to decode as
   ASN.1, a value if its syntax is not known. The implementation may
   attempt to discover the subschema of the source entry, and retrieve
   the values of attributeTypes from it.

   Clients MUST NOT send attribute values in a request that are not
   valid according to the syntax defined for the attributes.

4.1.7. 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 an option specifying the transfer encoding is present in
   attributeDesc, the assertionValue is encoded as specified by the
   option. For example, if the "binary" option is present in the
   attributeDesc, the AssertionValue is BER encoded.

   For all the string-valued user attributes described in [RFC2252], the
   assertion value syntax is the same as the value syntax. Clients may
   use attribute values as assertion values in compare requests and
   search filters.

   Note however that the assertion syntax may be different from the
   value syntax for other attributes or for non-equality matching rules.
   These may have an assertion syntax which contains only part of the
   value. See section 20.2.1.8 of [X.501] 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

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   from the server to the client. This is described in section 4.5.2,
   concerning the PartialAttributeList type.)

        Attribute ::= SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

   Each attribute value is distinct in the set (no duplicates). The
   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 [RFC2252], or as decimal digits with
   components separated by periods, e.g. "caseIgnoreIA5Match" or
   "1.3.6.1.4.1.453.33.33".

        MatchingRuleId ::= LDAPString

   Servers which support matching rules for use in the extensibleMatch
   search filter MUST list the matching rules they implement in
   subschema entries, using the matchingRules attributes. The server
   SHOULD also list there, using the matchingRuleUse attribute, the
   attribute types with which each matching rule can be used. More
   information is given in section 4.5 of [RFC2252].

4.1.10. Result Message

   The LDAPResult is the construct used in this protocol to return
   success or failure indications from servers to clients. To various
   requests, servers will return responses of LDAPResult or responses
   containing the components of LDAPResponse 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),

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                        adminLimitExceeded           (11),
                        unavailableCriticalExtension (12),
                        confidentialityRequired      (13),
                        saslBindInProgress           (14),
                        noSuchAttribute              (16),
                        undefinedAttributeType       (17),
                        inappropriateMatching        (18),
                        constraintViolation          (19),
                        attributeOrValueExists       (20),
                        invalidAttributeSyntax       (21),
                                        -- 22-31 unused --
                        noSuchObject                 (32),
                        aliasProblem                 (33),
                        invalidDNSyntax              (34),
                        -- 35 reserved for undefined isLeaf --
                        aliasDereferencingProblem    (36),
                                        -- 37-47 unused --
                        inappropriateAuthentication  (48),
                        invalidCredentials           (49),
                        insufficientAccessRights     (50),
                        busy                         (51),
                        unavailable                  (52),
                        unwillingToPerform           (53),
                        loopDetect                   (54),
                                        -- 55-63 unused --
                        namingViolation              (64),
                        objectClassViolation         (65),
                        notAllowedOnNonLeaf          (66),
                        notAllowedOnRDN              (67),
                        entryAlreadyExists           (68),
                        objectClassModsProhibited    (69),
                                -- 70 reserved for CLDAP --
                        affectsMultipleDSAs          (71),
                                        -- 72-79 unused --
                        other                        (80) },
                        -- 81-90 reserved for APIs --
                matchedDN       LDAPDN,
                errorMessage    LDAPString,
                referral        [3] Referral OPTIONAL }

   All the result codes with the exception of success, compareFalse and
   compareTrue are to be treated as meaning the operation could not be
   completed in its entirety.

   Most of the result codes are based on problem indications from X.511
   error data types. Result codes from 16 to 21 indicate an
   AttributeProblem, codes 32, 33, 34 and 36 indicate a NameProblem,
   codes 48, 49 and 50 indicate a SecurityProblem, codes 51 to 54
   indicate a ServiceProblem, and codes 64 to 69 and 71 indicates an
   UpdateProblem.

   If a client receives a result code which is not listed above, it is
   to be treated as an unknown error condition.


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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.

   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]. The matchedDN field is to be set to a zero length string
   with all other result codes.

4.1.11. Referral

   The referral result code indicates that the contacted server does not
   hold the target entry of the request. The referral field is present
   in an LDAPResult if the LDAPResult.resultCode field value is
   referral, and absent with all other result codes. It contains one or
   more references to one or more servers or services that may be
   accessed via LDAP or other protocols. Referrals can be returned in
   response to any operation request (except unbind and abandon which do
   not have responses). At least one URL MUST be present in the
   Referral.

   The referral is not returned for a singleLevel or wholeSubtree search
   in which the search scope spans multiple naming contexts, and several
   different servers would need to be contacted to complete the
   operation. Instead, continuation references, described in section
   4.5.3, are returned.

        Referral ::= SEQUENCE OF LDAPURL  -- one or more

        LDAPURL ::= LDAPString -- limited to characters permitted in
                               -- URLs

   If the client wishes to progress the operation, it MUST follow the
   referral by contacting one of the servers. If multiple URLs are
   present, the client assumes that any URL may be used to progress the
   operation.

   URLs for servers implementing the LDAP protocol are written according
   to [RFC2255]. 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

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   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 [RFC2396].

   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 and is only used when a
   control accompanies one of the following requests: bindRequest,
   searchRequest, modifyRequest, addRequest, delRequest, modDNRequest,
   compareRequest, or extendedReq. The use of the criticality field for
   a control that is part of any other operation is ignored and treated
   as FALSE.

   If the server recognizes the control type and it is appropriate for
   the operation, the server will make use of the control when
   performing the operation.

   If the server does not recognize the control type or it is not
   appropriate for the operation, and the criticality field is TRUE, the
   server MUST NOT perform the operation, and MUST instead return the
   resultCode unavailableCriticalExtension.

   If the control is unrecognized or inappropriate but the criticality
   field is FALSE, the server MUST ignore the control.

   The controlValue contains any information associated with the
   control, and its format is defined for the control. Implementations
   MUST be prepared to handle arbitrary contents of the controlValue
   octet string, including zero bytes. It is absent only if there is no
   value information which is associated with a control of its type.


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   This document does not define any controls. Controls may be defined
   in other documents. The definition of a control consists of:

   - the OBJECT IDENTIFIER assigned to the control,

   - whether the control is always noncritical, always critical, or
     critical at the client's option,

   - the format of the controlValue contents of the control.

   Servers list the controls which they recognize in the
   supportedControl attribute in the root DSE.

4.2. Bind Operation

   The function of the Bind Operation is to allow authentication
   information to be exchanged between the client and server.

   The Bind Request is defined as follows:

        BindRequest ::= [APPLICATION 0] SEQUENCE {
                version                 INTEGER (1 .. 127),
                name                    LDAPDN,
                authentication          AuthenticationChoice }

        AuthenticationChoice ::= CHOICE {
                simple                  [0] OCTET STRING,
                                         -- 1 and 2 reserved
                sasl                    [3] SaslCredentials }

        SaslCredentials ::= SEQUENCE {
                mechanism               LDAPString,
                credentials             OCTET STRING OPTIONAL }

   Parameters of the Bind Request are:

   - version: A version number indicating the version of the protocol
     to be used in this protocol session. This document describes
     version 3 of the LDAP protocol. Note that there is no version
     negotiation, and the client just sets this parameter to the
     version it desires. If the client requests protocol version 2, a
     server that supports the version 2 protocol as described in
     [RFC1777] 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 name in the
     credentials. Server behavior is undefined when the name is a null
     value, simple authentication is used, and a password is specified.

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     Note that the server SHOULD NOT perform any alias dereferencing in
     determining the object to bind as.

   - authentication: information used to authenticate the name, if any,
     provided in the Bind Request.

   Upon receipt of a Bind Request, a protocol server will authenticate
   the requesting client, if necessary. The server will then return a
   Bind Response to the client indicating the status of the
   authentication.

   Authorization is the use of this authentication information when
   performing operations. Authorization MAY be affected by factors
   outside of the LDAP Bind request, such as lower layer security
   services.

4.2.1. Sequencing of the Bind Request

   For some SASL authentication mechanisms, it may be necessary for the
   client to invoke the BindRequest multiple times. If at any stage the
   client wishes to abort the bind process it MAY unbind and then drop
   the underlying connection. Clients MUST NOT invoke operations between
   two Bind requests made as part of a multi-stage bind.

   A client may abort a SASL bind negotiation by sending a BindRequest
   with a different value in the mechanism field of SaslCredentials, or
   an AuthenticationChoice other than sasl.

   If the client sends a BindRequest with the sasl mechanism field as an
   empty string, 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 anonymous. 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

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   integrity mechanism has been negotiated, and that mechanism does not
   support the changing of credentials from one identity to another,
   then the client MUST instead establish a new connection.

4.2.2. Authentication and Other Security Services

   The simple authentication option provides minimal authentication
   facilities, with the contents of the authentication field consisting
   only of a cleartext password. Note that the use of cleartext
   passwords is not recommended over open networks when the underlying
   transport service cannot guarantee confidentiality; see the "Security
   Considerations" section.

   If anonymous 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 name is
   also of zero length.

   The sasl choice allows for any mechanism defined for use with SASL
   [RFC2222]. 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 the
   status of the client's request for authentication.

   If the bind was successful, the resultCode will be success, otherwise
   it will be one of:

   - operationsError: server encountered an internal error.

   - protocolError: unrecognized version number or incorrect PDU
     structure.

   - authMethodNotSupported: unrecognized SASL mechanism name.

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   - 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
   to allow the client to authenticate the server to which it is
   communicating, or to perform "challenge-response" authentication. If
   the client bound with the password choice, or the SASL mechanism does
   not require the server to return information to the client, then this
   field is not to be included in the result.

4.3. Unbind Operation

   The function of the Unbind Operation is to terminate a protocol
   session. The Unbind Operation is defined as follows:

        UnbindRequest ::= [APPLICATION 2] NULL

   The Unbind Operation has no response defined. Upon transmission of an
   UnbindRequest, a protocol client may assume that the protocol session
   is terminated. Upon receipt of an UnbindRequest, a protocol server
   may assume that the requesting client has terminated the session and
   that all outstanding requests may be discarded, and may close the
   connection.

4.4. Unsolicited Notification

   An unsolicited notification is an LDAPMessage sent from the server to
   the client which is not in response to any LDAPMessage received by

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   the server. It is used to signal an extraordinary condition in the
   server or in the connection between the client and the server. The
   notification is of an advisory nature, and the server will not expect
   any response to be returned from the client.

   The unsolicited notification is structured as an LDAPMessage in which
   the messageID is 0 and protocolOp is of the extendedResp form. The
   responseName field of the ExtendedResponse is present. The LDAPOID
   value MUST be unique for this notification, and not be used in any
   other situation.

   One unsolicited notification (Notice of Disconnection) is defined in
   this document.

4.4.1. Notice of Disconnection

   This notification may be used by the server to advise the client that
   the server is about to close the connection due to an error
   condition. Note that this notification is NOT a response to an unbind
   requested by the client: the server MUST follow the procedures of
   section 4.3. This notification is intended to assist clients in
   distinguishing between an error condition and a transient network
   failure. As with a connection close due to network failure, the
   client MUST NOT assume that any outstanding requests which modified
   the directory have succeeded or failed.

   The responseName is 1.3.6.1.4.1.1466.20036, the response field is
   absent, and the resultCode is used to indicate the reason for the
   disconnection.

   The following resultCode values are to be used in this notification:

   - protocolError: The server has received data from the client in
     which the LDAPMessage structure could not be parsed.

   - 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 SIZE (1..MAX) OF Filter,
                or              [1] SET SIZE (1..MAX) OF Filter,
                not             [2] Filter,
                equalityMatch   [3] AttributeValueAssertion,
                substrings      [4] SubstringFilter,
                greaterOrEqual  [5] AttributeValueAssertion,
                lessOrEqual     [6] AttributeValueAssertion,
                present         [7] AttributeDescription,
                approxMatch     [8] AttributeValueAssertion,
                extensibleMatch [9] MatchingRuleAssertion }

        SubstringFilter ::= SEQUENCE {
                type            AttributeDescription,
                -- at least one must be present,
                -- initial and final can occur at most once
                substrings      SEQUENCE OF CHOICE {
                        initial [0] AssertionValue,
                        any     [1] AssertionValue,
                        final   [2] AssertionValue } }

        MatchingRuleAssertion ::= SEQUENCE {
                matchingRule    [1] MatchingRuleId OPTIONAL,
                type            [2] AttributeDescription OPTIONAL,
                matchValue      [3] AssertionValue,
                dnAttributes    [4] BOOLEAN DEFAULT FALSE }

   Parameters of the Search Request are:

   - baseObject: An LDAPDN that is the base object entry relative to
     which the search is to be performed.


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   - scope: An indicator of the scope of the search to be performed.
     The semantics of the possible values of this field are identical
     to the semantics of the scope field in the X.511 Search Operation.

   - derefAliases: An indicator as to how alias objects (as defined in
     X.501) are to be handled in searching. The semantics of the
     possible values of this field are:

             neverDerefAliases: do not dereference aliases in searching
             or in locating the base object of the search;

             derefInSearching: dereference aliases in subordinates of
             the base object in searching, but not in locating the base
             object of the search;

             derefFindingBaseObj: dereference aliases in locating the
             base object of the search, but not when searching
             subordinates of the base object;

             derefAlways: dereference aliases both in searching and in
             locating the base object of the search.

   - sizeLimit: A size limit that restricts the maximum number of
     entries to be returned as a result of the search. A value of 0 in
     this field indicates that no client-requested size limit
     restrictions are in effect for the search. Servers may enforce a
     maximum number of entries to return.

   - timeLimit: A time limit that restricts the maximum time (in
     seconds) allowed for a search. A value of 0 in this field
     indicates that no client-requested time limit restrictions are in
     effect for the search.

   - typesOnly: An indicator as to whether search results will contain
     both attribute types and values, or just attribute types. Setting
     this field to TRUE causes only attribute types (no values) to be
     returned. Setting this field to FALSE causes both attribute types
     and values to be returned.

   - filter: A filter that defines the conditions that must be
     fulfilled in order for the search to match a given entry.

     The 'and', 'or' and 'not' choices can be used to form combinations
     of filters. At least one filter element MUST be present in an
     'and' or 'or' choice. The others match against individual
     attribute values of entries in the scope of the search.
     (Implementor's note: the 'not' filter is an example of a tagged
     choice in an implicitly-tagged module. In BER this is treated as
     if the tag was explicit.)

     A server MUST evaluate filters according to the three-valued logic
     of X.511 (1993) section 7.8.1. In summary, a filter is evaluated
     to either "TRUE", "FALSE" or "Undefined". If the filter evaluates
     to TRUE for a particular entry, then the attributes of that entry

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     are returned as part of the search result (subject to any
     applicable access control restrictions). If the filter evaluates
     to FALSE or Undefined, then the entry is ignored for the search.

     A filter of the "and" choice is TRUE if all the filters in the SET
     OF evaluate to TRUE, FALSE if at least one filter is FALSE, and
     otherwise Undefined. A filter of the "or" choice is FALSE if all
     of the filters in the SET OF evaluate to FALSE, TRUE if at least
     one filter is TRUE, and Undefined otherwise. A filter of the "not"
     choice is TRUE if the filter being negated is FALSE, FALSE if it
     is TRUE, and Undefined if it is Undefined.

     The present match evaluates to TRUE where there is an attribute or
     subtype of the specified attribute description present in an
     entry, and FALSE otherwise (including a presence test with an
     unrecognized attribute description.)

     The extensibleMatch is new in this version of LDAP. If the
     matchingRule field is absent, the type field MUST be present, and
     the equality match is performed for that type. If the type field
     is absent and matchingRule is present, the matchValue is compared
     against all attributes in an entry which support that
     matchingRule, and the matchingRule determines the syntax for the
     assertion value (the filter item evaluates to TRUE if it matches
     with at least one attribute in the entry, FALSE if it does not
     match any attribute in the entry, and Undefined if the
     matchingRule is not recognized or the assertionValue cannot be
     parsed.) If the type field is present and matchingRule is present,
     the matchingRule MUST be one permitted for use with that type,
     otherwise the filter item is undefined. If the dnAttributes field
     is set to TRUE, the match is applied against all the attributes in
     an entry's distinguished name as well, and also evaluates to TRUE
     if there is at least one attribute in the distinguished name for
     which the filter item evaluates to TRUE. (Editors note: The
     dnAttributes field is present so that there does not need to be
     multiple versions of generic matching rules such as for word
     matching, one to apply to entries and another to apply to entries
     and dn attributes as well).

     A filter item evaluates to Undefined when the server would not be
     able to determine whether the assertion value matches an entry. If
     an attribute description in an equalityMatch, substrings,
     greaterOrEqual, lessOrEqual, approxMatch or extensibleMatch filter
     is not recognized by the server, a matching rule id in the
     extensibleMatch is not recognized by the server, the assertion
     value cannot be parsed, or the type of filtering requested is not
     implemented, then the filter is Undefined. Thus for example if a
     server did not recognize the attribute type shoeSize, a filter of
     (shoeSize=*) would evaluate to FALSE, and the filters
     (shoeSize=12), (shoeSize>=12) and (shoeSize<=12) would evaluate to
     Undefined.

     Servers MUST NOT return errors if attribute descriptions or
     matching rule ids are not recognized, or assertion values cannot

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     be parsed. More details of filter processing are given in section
     7.8 of [X.511].

   - attributes: A list of the attributes to be returned from each
     entry which matches the search filter. There are two special
     values which may be used: an empty list with no attributes, and
     the attribute description string "*". Both of these signify that
     all user attributes are to be returned. (The "*" allows the client
     to request all user attributes in addition to specific operational
     attributes).

     Attributes MUST be named at most once in the list, and are
     returned at most once in an entry. If there are attribute
     descriptions in the list which are not recognized, they are
     ignored by the server.

     If the client does not want any attributes returned, it can
     specify a list containing only the attribute with OID "1.1". This
     OID was chosen arbitrarily and does not correspond to any
     attribute in use.

     Client implementors should note that even if all user attributes
     are requested, some attributes of the entry may not be included in
     search results due to access controls or other restrictions.
     Furthermore, servers will not return operational attributes, such
     as objectClasses or attributeTypes, unless they are listed by
     name, since there may be extremely large number of values for
     certain operational attributes. (A list of operational attributes
     for use in LDAP is given in [RFC2252].)

   Note that an X.500 "list"-like operation can be emulated by the
   client requesting a one-level LDAP search operation with a filter
   checking for the presence of the objectClass attribute, and that an
   X.500 "read"-like operation can be emulated by a base object LDAP
   search operation with the same filter. A server which provides a
   gateway to X.500 is not required to use the Read or List operations,
   although it may choose to do so, and if it does, it must provide the
   same semantics as the X.500 search operation.

4.5.2. Search Result

   The results of the search attempted by the server upon receipt of a
   Search Request are returned in Search Responses, which are LDAP
   messages containing either SearchResultEntry, SearchResultReference,
   or SearchResultDone data types.

        SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
                objectName      LDAPDN,
                attributes      PartialAttributeList }

        PartialAttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }
        -- implementors should note that the PartialAttributeList may

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        -- have zero elements (if none of the attributes of that entry
        -- were requested, or could be returned), and that the vals set
        -- may also have zero elements (if types only was requested, or
        -- all values were excluded from the result.)

        SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL
        -- at least one LDAPURL element must be present

        SearchResultDone ::= [APPLICATION 5] LDAPResult

   Upon receipt of a Search Request, a server will perform the necessary
   search of the DIT.

   If the LDAP session is operating over a connection-oriented transport
   such as TCP, the server will return to the client a sequence of
   responses in separate LDAP messages. There may be zero or more
   responses containing SearchResultEntry, one for each entry found
   during the search. There may also be zero or more responses
   containing SearchResultReference, one for each area not explored by
   this server during the search. The SearchResultEntry and
   SearchResultReference PDUs may come in any order. Following all the
   SearchResultReference responses and all SearchResultEntry responses
   to be returned by the server, the server will return a response
   containing the SearchResultDone, which contains an indication of
   success, or detailing any errors that have occurred.

   Each entry returned in a SearchResultEntry will contain all
   attributes, complete with associated values if necessary, as
   specified in the attributes field of the Search Request. Return of
   attributes is subject to access control and other administrative
   policy. Some attributes may be returned in binary format (indicated
   by the AttributeDescription in the response having the "binary"
   option present).

   Some attributes may be constructed by the server and appear in a
   SearchResultEntry attribute list, although they are not stored
   attributes of an entry. Clients MUST NOT assume that all attributes
   can be modified, even if permitted by access control.

4.5.3. Continuation References in the Search Result

   If the server was able to locate the entry referred to by the
   baseObject but was unable to search all the entries in the scope at
   and under the baseObject, the server may return one or more
   SearchResultReference entries, each containing a reference to another
   set of servers for continuing the operation. A server MUST NOT return
   any SearchResultReference if it has not located the baseObject and
   thus has not searched any entries; in this case it would return a
   SearchResultDone containing a referral resultCode.

   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.

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   The SearchResultReference is of the same data type as the Referral.
   URLs for servers implementing the LDAP protocol are written according
   to [RFC2255]. The <dn> part MUST be present in the URL, with the new
   target object name. The client MUST use this name in its next
   request. Some servers (e.g. part of a distributed index exchange
   system) may provide a different filter in the URLs of the
   SearchResultReference. If the filter part of the URL is present in an
   LDAP URL, the client MUST use the new filter in its next request to
   progress the search, and if the filter part is absent the client will
   use again the same filter. Other aspects of the new search request
   may be the same or different as the search which generated the
   continuation references.
   Other kinds of URLs may be returned so long as the operation could be
   performed using that protocol.

   The name of an unexplored subtree in a SearchResultReference need not
   be subordinate to the base object.

   In order to complete the search, the client MUST issue a new search
   operation for each SearchResultReference that is returned. Note that
   the abandon operation described in section 4.11 applies only to a
   particular operation sent on a connection between a client and
   server, and if the client has multiple outstanding search operations,
   it MUST abandon each operation individually.

4.5.3.1. Example

   For example, suppose the contacted server (hosta) holds the entry
   "O=MNN,C=WW" and the entry "CN=Manager,O=MNN,C=WW". It knows that
   either LDAP-capable servers (hostb) or (hostc) hold
   "OU=People,O=MNN,C=WW" (one is the master and the other server a
   shadow), and that LDAP-capable server (hostd) holds the subtree
   "OU=Roles,O=MNN,C=WW". If a subtree search of "O=MNN,C=WW" is
   requested to the contacted server, it may return the following:

     SearchResultEntry for O=MNN,C=WW
     SearchResultEntry for CN=Manager,O=MNN,C=WW
     SearchResultReference {
       ldap://hostb/OU=People,O=MNN,C=WW
       ldap://hostc/OU=People,O=MNN,C=WW
     }
     SearchResultReference {
       ldap://hostd/OU=Roles,O=MNN,C=WW
     }
     SearchResultDone (success)

   Client implementors should note that when following a
   SearchResultReference, additional SearchResultReference may be
   generated. Continuing the example, if the client contacted the server
   (hostb) and issued the search for the subtree "OU=People,O=MNN,C=WW",
   the server might respond as follows:

     SearchResultEntry for OU=People,O=MNN,C=WW

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     SearchResultReference {
       ldap://hoste/OU=Managers,OU=People,O=MNN,C=WW
     }
     SearchResultReference {
       ldap://hostf/OU=Consultants,OU=People,O=MNN,C=WW
     }
     SearchResultDone (success)

   If the contacted server does not hold the base object for the search,
   then it will return a referral to the client. For example, if the
   client requests a subtree search of "O=XYZ,C=US" to hosta, the server
   may return only a SearchResultDone containing a referral.

     SearchResultDone (referral) {
       ldap://hostg/
     }

4.6. Modify Operation

   The Modify Operation allows a client to request that a modification
   of an entry be performed on its behalf by a server. The Modify
   Request is defined as follows:

        ModifyRequest ::= [APPLICATION 6] SEQUENCE {
                object          LDAPDN,
                modification    SEQUENCE OF SEQUENCE {
                        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 add or delete individual values of
   that attribute from an entry using the "add" or "delete" form of a
   modification, and MUST instead use the "replace" form.

   Note that due to the simplifications made in LDAP, there is not a
   direct mapping of the modifications in an LDAP ModifyRequest onto the
   EntryModifications of a DAP ModifyEntry operation, and different
   implementations of LDAP-DAP gateways may use different means of
   representing the change. If successful, the final effect of the
   operations on the entry MUST be identical.

4.7. Add Operation



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   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 NO-USER-MODIFICATION
     attributes such as the createTimestamp or creatorsName attributes,
     since the server maintains these automatically.

   The entry named in the entry field of the AddRequest MUST NOT exist
   for the AddRequest to succeed. The parent of the entry to be added
   MUST exist. For example, if the client attempted to add
   "CN=JS,O=Foo,C=US", the "O=Foo,C=US" entry did not exist, and the
   "C=US" entry did exist, then the server would return the error
   noSuchObject with the matchedDN field containing "C=US". If the
   parent entry exists but is not in a naming context held by the
   server, the server SHOULD return a referral to the server holding the
   parent entry.

   Servers implementations SHOULD NOT restrict where entries can be
   located in the directory. Some servers MAY allow the administrator to
   restrict the classes of entries which can be added to the directory.

   Upon receipt of an Add Request, a server will attempt to perform the
   add requested. The result of the add attempt will be returned to the
   client in the Add Response, defined as follows:

        AddResponse ::= [APPLICATION 9] LDAPResult

   A response of success indicates that the new entry is present in the
   directory.

4.8. Delete Operation

   The Delete Operation allows a client to request the removal of an
   entry from the directory. The Delete Request is defined as follows:

        DelRequest ::= [APPLICATION 10] LDAPDN

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   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
   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. Note that the
     server will not dereference any aliases in locating the entry to
     be changed.

   - newrdn: the RDN that will form the leftmost component of the new
     name of the entry.

   - deleteoldrdn: a boolean parameter that controls whether the old
     RDN attribute values are to be retained as attributes of the
     entry, or deleted from the entry.

   - newSuperior: if present, this is the Distinguished Name of 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



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   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.

   Note that X.500 restricts the ModifyDN operation to only affect
   entries that are contained within a single server. If the LDAP server
   is mapped onto DAP, then this restriction will apply, and the
   resultCode affectsMultipleDSAs will be returned if this error
   occurred. In general clients MUST NOT expect to be able to perform
   arbitrary movements of entries and subtrees between servers.

4.10. Compare Operation

   The Compare Operation allows a client to compare an assertion
   provided with an entry in the directory. The Compare Request is
   defined as follows:

        CompareRequest ::= [APPLICATION 14] SEQUENCE {
                entry           LDAPDN,
                ava             AttributeValueAssertion }

   Parameters of the Compare Request are:

   - entry: the name of the entry to be compared with. Note that the
     server SHOULD NOT dereference any aliases in locating the entry to
     be compared with.

   - ava: the assertion with which an attribute in the entry is to be
     compared.

   The result of the compare attempted by the server upon receipt of a
   Compare Request is returned in the Compare Response, defined as
   follows:

        CompareResponse ::= [APPLICATION 15] LDAPResult

   Upon receipt of a Compare Request, a server will attempt to perform
   the requested comparison. 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.

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   Note that some directory systems may establish access controls which
   permit the values of certain attributes (such as userPassword) to be
   compared but not read. In a search result, it may be that an
   attribute of that type would be returned, but with an empty set of
   values.

4.11. Abandon Operation

   The function of the Abandon Operation is to allow a client to request
   that the server abandon an outstanding operation. The Abandon Request
   is defined as follows:

        AbandonRequest ::= [APPLICATION 16] MessageID

   The MessageID MUST be that of an operation which was requested
   earlier in this connection.

   (The abandon request itself has its own message id. This is distinct
   from the id of the earlier operation being abandoned.)

   There is no response defined in the Abandon Operation. Upon
   transmission of an Abandon Operation, a client may expect that the
   operation identified by the Message ID in the Abandon Request will be
   abandoned. In the event that a server receives an Abandon Request on
   a Search Operation in the midst of transmitting responses to the
   search, that server MUST cease transmitting entry responses to the
   abandoned request immediately, and MUST NOT send the
   SearchResponseDone. Of course, the server MUST ensure that only
   properly encoded LDAPMessage PDUs are transmitted.

   Clients MUST NOT send abandon requests for the same operation
   multiple times, and MUST also be prepared to receive results from
   operations it has abandoned (since these may have been in transit
   when the abandon was requested).

   Servers MUST discard abandon requests for message IDs they do not
   recognize, for operations which cannot be abandoned, and for
   operations which have already been abandoned.

4.12. Extended Operation

   An extension mechanism has been added in this version of LDAP, in
   order to allow additional operations to be defined for services not
   available elsewhere in this protocol, for instance digitally signed
   operations and results.

   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,

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                requestValue     [1] OCTET STRING OPTIONAL }

   The requestName is a dotted-decimal representation of the OBJECT
   IDENTIFIER corresponding to the request. The requestValue is
   information in a form defined by that request, encapsulated inside an
   OCTET STRING.

   The server will respond to this with an LDAPMessage containing the
   ExtendedResponse.

        ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
                COMPONENTS OF LDAPResult,
                responseName     [10] LDAPOID OPTIONAL,
                response         [11] OCTET STRING OPTIONAL }

   If the server does not recognize the request name, it MUST return
   only the response fields from LDAPResult, containing the
   protocolError result code.

5. Protocol Element Encodings and Transfer

   One underlying service is defined here. Clients and servers SHOULD
   implement the mapping of LDAP over TCP described in 5.2.1.

5.1. Protocol Encoding

   The protocol elements of LDAP are encoded for exchange using the
   Basic Encoding Rules (BER) [X.690] of ASN.1 [X.680]. However, due to
   the high overhead involved in using certain elements of the BER, the
   following additional restrictions are placed on BER-encodings of LDAP
   protocol elements:

   (1) Only the definite form of length encoding will be used.

   (2) OCTET STRING values will be encoded in the primitive form only.

   (3) If the value of a BOOLEAN type is true, the encoding MUST have
       its contents octets set to hex "FF".

   (4) If a value of a type is its default value, it MUST be absent.
       Only some BOOLEAN and INTEGER types have default values in this
       protocol definition.

   These restrictions do not apply to ASN.1 types encapsulated inside of
   OCTET STRING values, such as attribute values, unless otherwise
   noted.

5.2. Transfer Protocols

   This protocol is designed to run over connection-oriented, reliable
   transports, with all 8 bits in an octet being significant in the data
   stream.

5.2.1. Transmission Control Protocol (TCP)

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   The encoded LDAPMessage PDUs are mapped directly onto the TCP
   bytestream. It is recommended that server implementations running
   over the TCP MAY provide a protocol listener on the assigned port,
   389. Servers may instead provide a listener on a different port
   number. Clients MUST support contacting servers on any valid TCP
   port.

6. Implementation Guidelines

   This document describes an Internet protocol.

6.1. Server Implementations

   The server MUST be capable of recognizing all the mandatory attribute
   type names and implement the syntaxes specified in [RFC2252]. Servers
   MAY also recognize additional attribute type names.

6.2. Client Implementations

   Clients which request referrals MUST ensure that they do not loop
   between servers. They MUST NOT repeatedly contact the same server for
   the same request with the same target entry name, scope and filter.
   Some clients may be using a counter that is incremented each time
   referral handling occurs for an operation, and these kinds of clients
   MUST be able to handle a DIT with at least ten layers of naming
   contexts between the root and a leaf entry.

   In the absence of prior agreements with servers, clients SHOULD NOT
   assume that servers support any particular schemas beyond those
   referenced in section 6.1. Different schemas can have different
   attribute types with the same names. The client can retrieve the
   subschema entries referenced by the subschemaSubentry attribute in
   the server's root DSE or in entries held by the server.

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 [RFC2222]. SASL allows for integrity and
   privacy services to be negotiated.

   It is also permitted that the server can return its credentials to
   the client, if it chooses to do so.

   Use of cleartext password is strongly discouraged where the
   underlying transport service cannot guarantee confidentiality and may
   result in disclosure of the password to unauthorized parties.

   When used with SASL, it should be noted that the name field of the
   BindRequest is not protected against modification. Thus if the
   distinguished name of the client (an LDAPDN) is agreed through the


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   negotiation of the credentials, it takes precedence over any value in
   the unprotected name field.

   Implementations which cache attributes and entries obtained via LDAP
   MUST ensure that access controls are maintained if that information
   is to be provided to multiple clients, since servers may have access
   control policies which prevent the return of entries or attributes in
   search results except to particular authenticated clients. For
   example, caches could serve result information only to the client
   whose request caused it to be in the cache.

8. Acknowledgements

   This document is an update to RFC 2251, by Mark Wahl, Tim Howes, and
   Steve Kille. Their work along with the input of individuals of the
   IETF LDAPEXT, LDUP, LDAPBIS, and other Working Groups is gratefully
   acknowledged.

9. Bibliography

   [ISO10646] Universal Multiple-Octet Coded Character Set (UCS) -
             Architecture and Basic Multilingual Plane, ISO/IEC 10646-1
             : 1993.

   [X.500]   ITU-T Rec. X.500, "The Directory: Overview of Concepts,
             Models and Service", 1993.

   [X.501]   ITU-T Rec. X.501, "The Directory: Models", 1993.

   [X.511]   ITU-T Rec. X.511, "The Directory: Abstract Service
             Definition", 1993.

   [X.680]   ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1) -
             Specification of Basic Notation", 1994.

   [X.690]   ITU-T Rec. X.690, "Specification of ASN.1 encoding rules:
             Basic, Canonical, and Distinguished Encoding Rules", 1994.

   [RFC1777] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory
             Access Protocol", RFC 1777, March 1995.

   [RFC1823] Howes, T., and M. Smith, "The LDAP Application Program
             Interface", RFC 1823, August 1995.

   [RFC2044] Yergeau, F., "UTF-8, a transformation format of Unicode
             and ISO 10646", RFC 2044, October 1996.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", RFC 2119, March 1997.

   [RFC2222] Meyers, J., "Simple Authentication and Security Layer",
             RFC 2222, October 1997.



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              Lightweight Directory Access Protocol Version 3

   [RFC2234] Crocker, D., and P. Overell, "Augmented BNF for Syntax
             Specifications: ABNF", RFC 2234, November 1997.

   [RFC2252] Wahl, M., Coulbeck, A., Howes, T., and S. Kille,
             "Lightweight Directory Access Protocol (v3): Attribute
             Syntax Definitions", RFC 2252, December 1997.

   [RFC2253] Kille, S., Wahl, M., and T. Howes, "Lightweight Directory
             Access Protocol (v3): UTF-8 String Representation of
             Distinguished Names", RFC 2253, December 1997.

   [RFC2255] Howes, T., and M. Smith, "The LDAP URL Format", RFC 2255,
             December 1997.

   [RFC2396] Berners-Lee, T., Fielding, R., and L. Masinter Uniform
             Resource Identifiers (URI): Generic Syntax", RFC 2396,
             August 1998.

   [RFC2829] Wahl, M., Alvestrand, H., Hodges, J., and R. Morgan,
             "Authentication Methods for LDAP", RFC 2829, May 2000

   [RFC2830] Hodges, J., Morgan, R., and M. Wahl "Lightweight Directory
             Access Protocol (v3): Extension for Transport Layer
             Security", RFC 2830, May 2000

10. Editor's Address

   Jim Sermersheim
   Novell, Inc.
   1800 South Novell Place
   Provo, Utah 84606, USA
   jimse@novell.com
   +1 801 861-3088






















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              Lightweight Directory Access Protocol Version 3

Appendix A - Complete ASN.1 Definition

        Lightweight-Directory-Access-Protocol-V3 DEFINITIONS
        IMPLICIT TAGS ::=

        BEGIN

        LDAPMessage ::= SEQUENCE {
                messageID       MessageID,
                protocolOp      CHOICE {
                        bindRequest     BindRequest,
                        bindResponse    BindResponse,
                        unbindRequest   UnbindRequest,
                        searchRequest   SearchRequest,
                        searchResEntry  SearchResultEntry,
                        searchResDone   SearchResultDone,
                        searchResRef    SearchResultReference,
                        modifyRequest   ModifyRequest,
                        modifyResponse  ModifyResponse,
                        addRequest      AddRequest,
                        addResponse     AddResponse,
                        delRequest      DelRequest,
                        delResponse     DelResponse,
                        modDNRequest    ModifyDNRequest,
                        modDNResponse   ModifyDNResponse,
                        compareRequest  CompareRequest,
                        compareResponse CompareResponse,
                        abandonRequest  AbandonRequest,
                        extendedReq     ExtendedRequest,
                        extendedResp    ExtendedResponse },
                 controls       [0] Controls OPTIONAL }

        MessageID ::= INTEGER (0 .. maxInt)

        maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --

        LDAPString ::= OCTET STRING

        LDAPOID ::= OCTET STRING

        LDAPDN ::= LDAPString

        RelativeLDAPDN ::= LDAPString

        AttributeType ::= LDAPString

        AttributeDescription ::= LDAPString

        AttributeDescriptionList ::= SEQUENCE OF
                AttributeDescription

        AttributeValue ::= OCTET STRING

        AttributeValueAssertion ::= SEQUENCE {

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                attributeDesc   AttributeDescription,
                assertionValue  AssertionValue }

        AssertionValue ::= OCTET STRING

        Attribute ::= SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        MatchingRuleId ::= LDAPString

        LDAPResult ::= SEQUENCE {
                resultCode      ENUMERATED {
                             success                      (0),
                             operationsError              (1),
                             protocolError                (2),
                             timeLimitExceeded            (3),
                             sizeLimitExceeded            (4),
                             compareFalse                 (5),
                             compareTrue                  (6),
                             authMethodNotSupported       (7),
                             strongAuthRequired           (8),
                                        -- 9 reserved --
                             referral                     (10),
                             adminLimitExceeded           (11),
                             unavailableCriticalExtension (12),
                             confidentialityRequired      (13),
                             saslBindInProgress           (14),
                             noSuchAttribute              (16),
                             undefinedAttributeType       (17),
                             inappropriateMatching        (18),
                             constraintViolation          (19),
                             attributeOrValueExists       (20),
                             invalidAttributeSyntax       (21),
                                        -- 22-31 unused --
                             noSuchObject                 (32),
                             aliasProblem                 (33),
                             invalidDNSyntax              (34),
                             -- 35 reserved for undefined isLeaf --
                             aliasDereferencingProblem    (36),
                                        -- 37-47 unused --
                             inappropriateAuthentication  (48),
                             invalidCredentials           (49),
                             insufficientAccessRights     (50),
                             busy                         (51),
                             unavailable                  (52),
                             unwillingToPerform           (53),
                             loopDetect                   (54),
                                        -- 55-63 unused --
                             namingViolation              (64),
                             objectClassViolation         (65),
                             notAllowedOnNonLeaf          (66),
                             notAllowedOnRDN              (67),
                             entryAlreadyExists           (68),

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                             objectClassModsProhibited    (69),
                                        -- 70 reserved for CLDAP --
                             affectsMultipleDSAs          (71),
                                        -- 72-79 unused --
                             other                        (80) },
                             -- 81-90 reserved for APIs --
                matchedDN       LDAPDN,
                errorMessage    LDAPString,
                referral        [3] Referral OPTIONAL }

        Referral ::= SEQUENCE OF LDAPURL

        LDAPURL ::= LDAPString -- limited to characters permitted in
                               -- URLs

        Controls ::= SEQUENCE OF Control

        Control ::= SEQUENCE {
                controlType             LDAPOID,
                criticality             BOOLEAN DEFAULT FALSE,
                controlValue            OCTET STRING OPTIONAL }

        BindRequest ::= [APPLICATION 0] SEQUENCE {
                version                 INTEGER (1 .. 127),
                name                    LDAPDN,
                authentication          AuthenticationChoice }

        AuthenticationChoice ::= CHOICE {
                simple                  [0] OCTET STRING,
                                         -- 1 and 2 reserved
                sasl                    [3] SaslCredentials }

        SaslCredentials ::= SEQUENCE {
                mechanism               LDAPString,
                credentials             OCTET STRING OPTIONAL }

        BindResponse ::= [APPLICATION 1] SEQUENCE {
             COMPONENTS OF LDAPResult,
             serverSaslCreds    [7] OCTET STRING OPTIONAL }

        UnbindRequest ::= [APPLICATION 2] NULL

        SearchRequest ::= [APPLICATION 3] SEQUENCE {
                baseObject      LDAPDN,
                scope           ENUMERATED {
                        baseObject              (0),
                        singleLevel             (1),
                        wholeSubtree            (2) },
                derefAliases    ENUMERATED {
                        neverDerefAliases       (0),
                        derefInSearching        (1),
                        derefFindingBaseObj     (2),
                        derefAlways             (3) },
                sizeLimit       INTEGER (0 .. maxInt),

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                timeLimit       INTEGER (0 .. maxInt),
                typesOnly       BOOLEAN,
                filter          Filter,
                attributes      AttributeDescriptionList }

        Filter ::= CHOICE {
                and             [0] SET SIZE (1..MAX) OF Filter,
                or              [1] SET SIZE (1..MAX) OF Filter,
                not             [2] Filter,
                equalityMatch   [3] AttributeValueAssertion,
                substrings      [4] SubstringFilter,
                greaterOrEqual  [5] AttributeValueAssertion,
                lessOrEqual     [6] AttributeValueAssertion,
                present         [7] AttributeDescription,
                approxMatch     [8] AttributeValueAssertion,
                extensibleMatch [9] MatchingRuleAssertion }

        SubstringFilter ::= SEQUENCE {
                type            AttributeDescription,
                -- at least one must be present,
                -- initial and final can occur at most once
                substrings      SEQUENCE OF CHOICE {
                        initial [0] AssertionValue,
                        any     [1] AssertionValue,
                        final   [2] AssertionValue } }

        MatchingRuleAssertion ::= SEQUENCE {
                matchingRule    [1] MatchingRuleId OPTIONAL,
                type            [2] AttributeDescription OPTIONAL,
                matchValue      [3] AssertionValue,
                dnAttributes    [4] BOOLEAN DEFAULT FALSE }

        SearchResultEntry ::= [APPLICATION 4] SEQUENCE {
                objectName      LDAPDN,
                attributes      PartialAttributeList }

        PartialAttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL

        SearchResultDone ::= [APPLICATION 5] LDAPResult

        ModifyRequest ::= [APPLICATION 6] SEQUENCE {
                object          LDAPDN,
                modification    SEQUENCE OF SEQUENCE {
                        operation       ENUMERATED {
                                                add     (0),
                                                delete  (1),
                                                replace (2) },
                        modification    AttributeTypeAndValues } }

        AttributeTypeAndValues ::= SEQUENCE {

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                type    AttributeDescription,
                vals    SET OF AttributeValue }

        ModifyResponse ::= [APPLICATION 7] LDAPResult

        AddRequest ::= [APPLICATION 8] SEQUENCE {
                entry           LDAPDN,
                attributes      AttributeList }

        AttributeList ::= SEQUENCE OF SEQUENCE {
                type    AttributeDescription,
                vals    SET OF AttributeValue }

        AddResponse ::= [APPLICATION 9] LDAPResult

        DelRequest ::= [APPLICATION 10] LDAPDN

        DelResponse ::= [APPLICATION 11] LDAPResult

        ModifyDNRequest ::= [APPLICATION 12] SEQUENCE {
                entry           LDAPDN,
                newrdn          RelativeLDAPDN,
                deleteoldrdn    BOOLEAN,
                newSuperior     [0] LDAPDN OPTIONAL }

        ModifyDNResponse ::= [APPLICATION 13] LDAPResult

        CompareRequest ::= [APPLICATION 14] SEQUENCE {
                entry           LDAPDN,
                ava             AttributeValueAssertion }

        CompareResponse ::= [APPLICATION 15] LDAPResult

        AbandonRequest ::= [APPLICATION 16] MessageID

        ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
                requestName      [0] LDAPOID,
                requestValue     [1] OCTET STRING OPTIONAL }

        ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
                COMPONENTS OF LDAPResult,
                responseName     [10] LDAPOID OPTIONAL,
                response         [11] OCTET STRING OPTIONAL }

        END










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Appendix B - Change History

B.1 Changes made to RFC 2251:

B.1.1 Editorial

   - Bibliography References: Changed all bibliography references to
     use a long name form for readability.
   - Changed occurrences of "unsupportedCriticalExtension"
     "unavailableCriticalExtension"
   - Fixed a small number of misspellings (mostly dropped letters).

B.1.2 Section 1

   - Removed IESG note.

B.1.3 Section 9

   - Added references to RFCs 1823, 2234, 2829 and 2830.


B.2 Changes made to draft-ietf-ldapbis-protocol-00.txt:

B.2.1 Section 4.1.6

   - In the first paragraph, clarified what the contents of an
     AttributeValue are. There was confusion regarding whether or not
     an AttributeValue that is BER encoded (due to the "binary" option)
     is to be wrapped in an extra OCTET STRING.
   - To the first paragraph, added wording that doesn't restrict other
     transfer encoding specifiers from being used. The previous wording
     only allowed for the string encoding and the ;binary encoding.
   - To the first paragraph, added a statement restricting multiple
     options that specify transfer encoding from being present. This
     was never specified in the previous version and was seen as a
     potential interoperability problem.
   - Added a third paragraph stating that the ;binary option is
     currently the only option defined that specifies the transfer
     encoding. This is for completeness.

B.2.2 Section 4.1.7

   - Generalized the second paragraph to read "If an option specifying
     the transfer encoding is present in attributeDesc, the
     AssertionValue is encoded as specified by the option...".
     Previously, only the ;binary option was mentioned.

B.2.3 Sections 4.2, 4.9, 4.10

   - Added alias dereferencing specifications. In the case of modDN,
     followed precedent set on other update operations (... alias is
     not dereferenced...) In the case of bind and compare stated that
     servers SHOULD NOT dereference aliases. Specifications were added
     because they were missing from the previous version and caused

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     interoperability problems. Concessions were made for bind and
     compare (neither should have ever allowed alias dereferencing) by
     using SHOULD NOT language, due to the behavior of some existing
     implementations.

B.2.4 Sections 4.5 and Appendix A

   - Changed SubstringFilter.substrings.initial, any, and all from
     LDAPString to AssertionValue. This was causing an incompatibility
     with X.500 and confusion among other TS RFCs.


B.3 Changes made to draft-ietf-ldapbis-protocol-01.txt:

B.3.1 Section 3.4

   - Reworded text surrounding subschemaSubentry to reflect that it is
     a single-valued attribute that holds the schema for the root DSE.
     Also noted that if the server masters entries that use differing
     schema, each entry's subschemaSubentry attribute must be
     interrogated. This may change as further fine-tuning is done to
     the data model.

B.3.2 Section 4.1.12

   - Specified that the criticality field is only used for requests and
     not for unbind or abandon. Noted that it is ignored for all other
     operations.

B.3.3 Section 4.2

   - Noted that Server behavior is undefined when the name is a null
     value, simple authentication is used, and a password is specified.

B.3.4 Section 4.2.(various)

   - Changed "unauthenticated" to "anonymous" and "DN" and "LDAPDN" to
     "name"

B.3.5 Section 4.2.2

   - Changed "there is no authentication or encryption being performed
     by a lower layer" to "the underlying transport service cannot
     guarantee confidentiality"

B.3.6 Section 4.5.2

   - Removed all mention of ExtendedResponse due to lack of
     implementation.

B.4 Changes made to draft-ietf-ldapbis-protocol-02.txt:

B.4.1 Section 4


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   - Removed "typically" from "and is typically transferred" in the
     first paragraph. We know of no (and can conceive of no) case where
     this isn't true.
   - Added "Section 5.1 specifies how the LDAP protocol is encoded." To
     the first paragraph. Added this cross reference for readability.
   - Changed "version 3 " to "version 3 or later" in the second
     paragraph. This was added to clarify the original intent.
   - Changed "protocol version" to "protocol versions" in the third
     paragraph. This attribute is multi-valued with the intent of
     holding all supported versions, not just one.

B.4.2 Section 4.1.8

   - Changed "when transferred in protocol" to "when transferred from
     the server to the client" in the first paragraph. This is to
     clarify that this behavior only happens when attributes are being
     sent from the server.

B.4.3 Section 4.1.10

   - Changed "servers will return responses containing fields of type
     LDAPResult" to "servers will return responses of LDAPResult or
     responses containing the components of LDAPResponse". This
     statement was incorrect and at odds with the ASN.1. The fix here
     reflects the original intent.
   - Dropped '--new' from result codes ASN.1. This simplification in
     comments just reduces unneeded verbiage.

B.4.4 Section 4.1.11

   - Changed "It contains a reference to another server (or set of
     servers)" to "It contains one or more references to one or more
     servers or services" in the first paragraph. This reflects the
     original intent and clarifies that the URL may point to non-LDAP
     services.

B.4.5 Section 4.1.12

   - Changed "The server MUST be prepared" to "Implementations MUST be
     prepared" in the eighth paragraph to reflect that both client and
     server implementations must be able to handle this (as both parse
     controls).

B.4.6 Section 4.4

   - Changed "One unsolicited notification is defined" to "One
     unsolicited notification (Notice of Disconnection) is defined" in
     the third paragraph. For clarity and readability.

B.4.7 Section 4.5.1

   - Changed "checking for the existence of the objectClass attribute"
     to "checking for the presence of the objectClass attribute" in the
     last paragraph. This was done as a measure of consistency (we use

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     the terms present and presence rather than exists and existence in
     search filters).

B.4.8 Section 4.5.3

   - Changed "outstanding search operations to different servers," to
     "outstanding search operations" in the fifth paragraph as they may
     be to the same server. This is a point of clarification.

B.4.9 Section 4.6

   - Changed "clients MUST NOT attempt to delete" to "clients MUST NOT
     attempt to add or delete" in the second to last paragraph.
   - Change "using the "delete" form" to "using the "add" or "delete"
     form" in the second to last paragraph.

B.4.10 Section 4.7

   - Changed "Clients MUST NOT supply the createTimestamp or
     creatorsName attributes, since these will be generated
     automatically by the server." to "Clients MUST NOT supply NO-USER-
     MODIFICATION attributes such as createTimestamp or creatorsName
     attributes, since these are provided by the server." in the
     definition of the attributes field. This tightens the language to
     reflect the original intent and to not leave a hole in which one
     could interpret the two attributes mentioned as the only non-
     writable attributes.

B.4.11 Section 4.11

   - Changed "has been" to "will be" in the fourth paragraph. This
     clarifies that the server will (not has) abandon the operation.


B.5 Changes made to draft-ietf-ldapbis-protocol-03.txt:

B.5.1 Section 3.2.1

   - Changed "An attribute is a type with one or more associated
     values. The attribute type is identified by a short descriptive
     name and an OID (object identifier). The attribute type governs
     whether there can be more than one value of an attribute of that
     type in an entry, the syntax to which the values must conform, the
     kinds of matching which can be performed on values of that
     attribute, and other functions." to " An attribute is a
     description (a type and zero or more options) with one or more
     associated values. The attribute type governs whether the
     attribute can have multiple values, the syntax and matching rules
     used to construct and compare values of that attribute, and other
     functions. Options indicate modes of transfer and other
     functions.". This points out that an attribute consists of both
     the type and options.

B.5.2 Section 4

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   -  Changed "Section 5.1 specifies the encoding rules for the LDAP
     protocol" to "Section 5.1 specifies how the protocol is encoded
     and transferred."

B.5.3 Section 4.1.2

   - Added ABNF for the textual representation of LDAPOID. Previously,
     there was no formal BNF for this construct.

B.5.4 Section 4.1.4

   - Changed "This identifier may be written as decimal digits with
     components separated by periods, e.g. "2.5.4.10"" to "may be
     written as defined by ldapOID in section 4.1.2" in the second
     paragraph. This was done because we now have a formal BNF
     definition of an oid.

B.5.5 Section 4.1.5

   - Changed the BNF for AttributeDescription to ABNF. This was done
     for readability and consistency (no functional changes involved).
   - Changed "Options present in an AttributeDescription are never
     mutually exclusive." to "Options MAY be mutually exclusive. An
     AttributeDescription with mutually exclusive options is treated as
     an undefined attribute type." for clarity. It is generally
     understood that this is the original intent, but the wording could
     be easily misinterpreted.
   - Changed "Any option could be associated with any AttributeType,
     although not all combinations may be supported by a server." to
     "Though any option or set of options could be associated with any
     AttributeType, the server support for certain combinations may be
     restricted by attribute type, syntaxes, or other factors.". This
     is to clarify the meaning of 'combination' (it applies both to
     combination of attribute type and options, and combination of
     options). It also gives examples of *why* they might be
     unsupported.

B.5.6 Section 4.1.11

   - Changed the wording regarding 'equally capable' referrals to "If
     multiple URLs are present, the client assumes that any URL may be
     used to progress the operation.". The previous language implied
     that the server MUST enforce rules that it was practically
     incapable of. The new language highlights the original intent--
     that is, that any of the referrals may be used to progress the
     operation, there is no inherent 'weighting' mechanism.

B.5.7 Section 4.5.1 and Appendix A

   - Added the comment "-- initial and final can occur at most once",
     to clarify this restriction.

B.5.8 Section 5.1

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   - Changed heading from "Mapping Onto BER-based Transport Services"
     to "Protocol Encoding".

B.5.9 Section 5.2.1

   - Changed "The LDAPMessage PDUs" to "The encoded LDAPMessage PDUs"
     to point out that the PDUs are encoded before being streamed to
     TCP.

B.6 Changes made to draft-ietf-ldapbis-protocol-04.txt:

B.6.1 Section 4.5.1 and Appendix A

   - Changed the ASN.1 for the and and or choices of Filter to have a
     lower range of 1. This was an omission in the original ASN.1

B.6.2 Various

   - Fixed various typo's

B.7 Changes made to draft-ietf-ldapbis-protocol-05.txt:

B.7.1 Section 3.2.1

   - Added "(as defined in Section 12.4.1 of [X.501])" to the fifth
     paragraph when talking about "operational attributes". This is
     because the term "operational attributes" is never defined.
     Alternately, we could drag a definition into the spec, for now,
     I'm just pointing to the reference in X.501.

B.7.2 Section 4.1.5

   - Changed "And is also case insensitive" to "The entire
     AttributeDescription is case insensitive". This is to clarify
     whether we're talking about the entire attribute description, or
     just the options.

   - Expounded on the definition of attribute description options. This
     doc now specifies a difference between transfer and tagging
     options and describes the semantics of each, and how and when
     subtyping rules apply. Now allow options to be transmitted in any
     order but disallow any ordering semantics to be implied. These
     changes are the result of ongoing input from an engineering team
     designed to deal with ambiguity issues surrounding attribute
     options.

B.7.3 Sections 4.1.5.1 and 4.1.6

   - Refer to non "binary" transfer encodings as "native encoding"
     rather than "string" encoding to clarify and avoid confusion.


Appendix C - Outstanding Work Items

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C.1 Integrate result codes draft.

   - The result codes draft should be reconciled with this draft.
     Operation-specific instructions will reside with operations while
     the error-specific sections will be added as an appendix.

C.2 Section 3.1

   - Add "This also increases the complexity of clients in this
     version." to fourth paragraph.

C.3 Section 4

   - Change "MUST ignore elements of SEQUENCE encodings whose tags they
     do not recognize" to "MUST ignore tagged elements of SEQUENCE
     encodings that they do not recognize" in the first paragraph.
   - Change "version 2 may not provide this attribute." to "version 2
     MAY NOT provide this attribute, or a root DSE." in the third
     paragraph.

C.4 Section 4.1.1

   - Change "the client may discard the PDU, or may abruptly close the
     connection." to "the client MAY discard the PDU, or MAY abruptly
     close the connection." in the fourth paragraph.

C.5 Section 4.1.1.1

   - Add "If an unsolicited notification as described in section 4.4 is
     sent from a server, the messageID value MUST be zero." to first
     paragraph.
   - Change "MUST have a value different" to "MUST have a non-zero
     value different" in the second paragraph.
   - Remove "or of the abandoned operation until it has received a
     response from the server for another request invoked subsequent to
     the abandonRequest," from the fourth paragraph as this imposes
     synchronous behavior on the server.

C.7 Section 4.1.4

   - Add "Note that due to the restriction above, and due to this
     allowance, servers MUST ensure that, within a controlling
     subschema, no two attributes be named the same." to the fifth
     paragraph.
   - Resolve issue on list with the subject "Attribute Type character
     set".

C.8 Section 4.1.5

   - Change "A server may treat" to "A server MUST treat" in the second
     to last paragraph.
   - Change "A server MUST treat an AttributeDescription with any
     options it does not implement as an unrecognized attribute type."

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     to "A server MUST treat an AttributeDescription with any options
     it does not implement or support as an unrecognized attribute
     type." in the second to last paragraph.
   - Clarify the statement "An AttributeDescription with one or more
     options is treated as a subtype of the attribute type without any
     options". There is an unresolved thread titles "RFC 2596
     questions" on the ietf-ldapext list regarding this.

C.9 Section 4.1.5.1

   - Add "Servers SHOULD only return attributes with printable string
     representations as binary when clients request binary transfer."
     to the second paragraph.
   - Clarify whether the "binary" attribute type option is to be
     treated as a subtype.

C.10 Section 4.1.6

   - Change "containing an encoded value of an AttributeValue data
     type" to "containing an encoded attribute value data type"

C.11 Section 4.1.7

   - Change "For all the string-valued user attributes described in
     [5], the assertion value syntax is the same as the value syntax."
     to "The assertion value syntax for all attributes using human-
     readable syntaxes as described in [RFC2252] is the same as the
     value syntax unless otherwise noted (an example being
     objectIdentifierFirstComponentMatch)." in the third paragraph.
   - Find out what the last sentence in third paragraph means (Clients
     may use attributes...)
   - Add a fourth paragraph: "Servers SHOULD NOT generate codes 81-90
     as these are reserved for use by historical APIs [RFC 1823]. Later
     API specifications SHOULD avoid using the resultCode enumeration
     to represent anything other than a protocol result indication."

C.13 Section 4.1.11

   - Add "after locating the target entry" to the first paragraph.

C.14 Section 4.1.12

   - Specify whether or not servers are to advertise the OIDs of known
     response controls.

C.15 Section 4.2

   - Change "LDAPDN" to "identity" in the definition of the name field.
   - Rework definition of the name field to enumerate empty password and
    name combinations. <Needs more work following discussion on list>

C.17 Section 4.2.2

   - Add "as the authentication identity" to second paragraph.

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C.18 Section 4.2.3

   - Change "If the bind was successful, the resultCode will be
     success, otherwise it will be one of" to "If the bind was
     successful, the resultCode will be success, otherwise it MAY be
     one of" in the third paragraph. <May need further refinement when
     reconciled with resultCode draft>.
   - Change "operationsError" to "other" as a result code.
   - Change "If the client bound with the password choice" to "If the
     client bound with the simple choice" in the last paragraph.

C.19 Section 4.3

   - Change "a protocol client may assume that the protocol session is
     terminated and MAY close the connection." to "a protocol client
     MUST assume that the protocol session is terminated and MAY close
     the connection." in the second paragraph.
   - Change "a protocol server may assume" to "a protocol server MUST
     assume" in the second paragraph.
   - Change "and may close the connection" to "and MUST close the
     connection" in the second paragraph.

C.20 Section 4.4

   - Add "Servers SHOULD NOT assume LDAPv3 clients understand or
     recognize unsolicited notifications or unsolicited 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." as a fourth paragraph.

C.21 Section 4.5.1

   - Make sure the use of "subordinates" in the derefInSearching
     definition is correct. See "derefInSearching" on list.

C.22 Section 4.5.2

   - Add "associated with a search operation" to the sixth paragraph.
   - Same problem as in C.5.

C.23 Section 4.5.3

   - Add "Similarly, a server MUST NOT return a SearchResultReference
     when the scope of the search is baseObject. If a client receives
     such a SearchResultReference it MUST interpret is as a protocol
     error and MUST NOT follow it." to the first paragraph.
   - Add "If the scope part of the LDAP URL is present, the client MUST
     use the new scope in its next request to progress the search. If
     the scope part is absent the client MUST use subtree scope to
     complete subtree searches and base scope to complete one level
     searches." to the third paragraph.


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C.24 Section 4.5.3.1

   - Change examples to use dc naming.

C.25 Section 4.6

   - Resolve the meaning of "and is ignored if the attribute does not
     exist". See "modify: "non-existent attribute"" on the list.

C.26 Section 4.7

   - Change examples to use dc naming.
   - Clarify the paragraph that talks about structure rules. See
     "discussing structure rules" on the list.

C.27 Section 4.10

   - Specify what happens when the attr is missing vs. attr isn't in
     schema. Also what happens if there's no equality matching rule.

C.28 Section 4.11

   - Change "(since these may have been in transit when the abandon was
     requested)." to "(since these may either have been in transit when
     the abandon was requested, or are not able to be abandoned)." in
     the fifth paragraph.
   - Add "Abandon and Unbind operations are not able to be abandoned.
     Other operations, in particular update operations, or operations
     that have been chained, may not be abandonable (or immediately
     abandonable)." as the sixth paragraph.

C.29 Section 4.12

   - Change "digitally signed operations and results" to "for instance
     StartTLS [RFC2830]"

C.30 Section 5.1

   - Add "control and extended operation values" to last paragraph. See
     "LBER (BER Restrictions)" on list.

C.31 Section 5.2.1

   - Add "using the BER-based described in section 5.1".

C.32 Section 6.1

   - Add "that are used by those attributes" to the first paragraph.
   - Add "Servers which support update operations MUST, and other
     servers SHOULD, support strong authentication mechanisms described
     in [RFC2829]." as a second paragraph.
   - Add "Servers which provide access to sensitive information MUST,
     and other servers SHOULD support privacy protections such as those
     described in [RFC2829] and [RFC2830]." as a third paragraph.

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C.33 Section 7

   - Add "Servers which support update operations MUST, and other
     servers SHOULD, support strong authentication mechanisms described
     in [RFC2829]." as a fourth paragraph.
   - Add "In order to automatically follow referrals, clients may need
     to hold authentication secrets. This poses significant privacy and
     security concerns and SHOULD be avoided." as a sixth paragraph.
   - Add "This document provides a mechanism which clients may use to
     discover operational attributes. Those relying on security by
     obscurity should implement appropriate access controls to
     restricts access to operational attributes per local policy." as
     an eighth paragraph.
   - Add "This document provides a mechanism which clients may use to
     discover operational attributes. Those relying on security by
     obscurity should implement appropriate access controls to
     restricts access to operational attributes per local policy." as
     an eighth paragraph.




































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