Network Working Group M. Wahl INTERNET-DRAFT Critical Angle Inc. Replaces: RFC 1777, RFC 1798 T. Howes Netscape Communications Corp. S. Kille ISODE Consortium Expires in six months from 22 October 1996 Intended Category: Standards Track Lightweight Directory Access Protocol (v3) <draft-ietf-asid-ldapv3-protocol-03.txt> Table of Contents - see end of document. 1. Status of this Memo This document is an Internet-Draft. 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." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). 2. Abstract The protocol described in this document is designed to provide access to directories supporting the X.500 models, while not incurring the resource requirements of the X.500 Directory Access Protocol (DAP). This protocol is specifically targeted at management applications and browser applications that provide read/write interactive access to directories. When used with a directory supporting the X.500 protocols, it is intended to be a complement to the X.500 DAP. Key aspects of this version of LDAP are: - All protocol elements of LDAP (RFC 1777) and CLDAP (RFC 1798) are supported. - Protocol elements are carried directly over TCP or other transport, bypassing much of the session/presentation overhead. Connectionless transport (UDP) is also supported for efficient lookup operations. - Most protocol data elements can be encoded as ordinary strings (e.g., Distinguished Names). Wahl, Howes & Kille [Page 1]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 - New features have been added, such as the abilities to retrieve attribute values in binary or search results in pages. - Important features of X.500(1993) and X.500(1997) are included. - Referrals to other servers can be returned. - The protocol can be extended to support bilaterally-defined operations. - Several session controls may be requested by the client. 3. Models Interest in X.500 [1] directory technologies in the Internet has lead 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: it updates the LDAP [2] protocol specification, adding support for new features, including some support for connecting to X.500 services that implement the 1993 or 1997 edition protocols. 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, which 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 utilizing the directory. Note that, although servers are required to return responses whenever such responses are defined in the protocol, there is no requirement for synchronous behavior on the part of either clients or servers. Requests and responses for multiple operations may be exchanged between a client and server in any order, provided the client eventually receives a response for every request that requires one. In LDAP versions 1 and 2, no provision was made for protocol servers returning referrals to clients. However, for improved performance and distribution this version of the protocol permits servers to return to clients referrals to other servers if requested. This allows servers, if requested by clients, to offload the work of contacting other servers to progress operations. Clients may also request that no referrals be returned, in which case the server must ensure that the operation is performed against the directory, or else return an error. This is the default. Wahl, Howes & Kille [Page 2]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 Note that this protocol 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 to perform extended operations. 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 values from the entry itself form its relative distinguished name (RDN), which must be unique among all its siblings. The concatenation of the relative distinguished names of the line 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 Consortium, 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. The largest collection of entries, starting an entry that is mastered by a particular server, and all its subordinates and their subordinates, down to an entry which is mastered by a different server, is termed a naming context. For example, in the following sample DIT, one server might master only the entry C=GB, and another server master both the entries O=Foo,C=US and O=Bar,C=US. Each of these entries are in a separate naming context. The root of the DIT is not an entry and not part of any naming context. (ROOT) | C=GB /------------/ \--------------\ O=Foo O=Bar 3.2.1 Attributes of Entries Entries consist of a set of attributes. An attribute is a type with one or more associated values. The attribute type, identified by a short descriptive name and an OID (object identifier), governs the maximum number of values permissible for an attribute of that type in an entry, the syntax to which the values must conform, the types of matching which can be performed on values of that attribute, and other functions. Wahl, Howes & Kille [Page 3]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 An example of an attribute is "mail". There may be one or more values of this attribute, they must be IA5 strings, and they are case insensitive (e.g. "foo@bar.com" will match "FOO@BAR.COM"). 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). A small number of attributes, termed operational attributes, are used by servers for administering the directory system itself. They are not returned in search results unless they were 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 subentry - see below), or are operational attributes known to that server and used for administrative purposes. Note that there is a particular objectClass 'extensibleObject' defined in [5] which permits all user attributes to be present in an entry. Entries contain, among others, the following operational attributes, defined in [5]. These attributes are maintained automatically by the server are not modifiable by clients: - creatorsName: the Distinguished Name of the user who added this entry to the directory. - createTimestamp: the time this entry was added to the directory. - modifiersName: the Distinguished Name of the user who last modified this entry. - modifyTimestamp: the time this entry was last modified. - subschemaSubentry: the Distinguished Name of the subschema subentry which controls the schema for this entry. - entryName: the Distinguished Name of the entry. Servers may implement other operational attributes. Servers which also make use of X.500(1993) protocols will provide support for more of the attributes defined in X.501, including administrativeRole and dseType. Some servers may permit the retrieval of subschema attributes directly from user entries. 3.2.2 Subschema Subentry A subentry is a special kind of entry which is used by servers and holds attributes for administering the directory system. Subentries are defined in clause 11.6 of X.501 [6]. Subschema subentries are used for administering information about the directory schema, in particular the object classes and attribute types supported by directory servers. Wahl, Howes & Kille [Page 4]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 A server may provide access to one or more subschema subentries to permit clients to interrogate the schema which is in force for entries in the directory. A server which masters entries and permits clients to modify these entries must implement and provide access to these subschema subentries, 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 subschema subentries as well. The following four attributes, defined in [6] with string representations in [5], must be present in all subschema subentries: - CN: this attribute must be used to form the RDN of the subschema subentry. - 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. Other operational attributes may be present in subschema subentries, in particular dseType, subtreeSpecification, ditStructureRules, nameForms, ditContentRules, matchingRules, matchingRuleUse, createTimestamp, creatorsName, modifyTimestamp, modifiersName, entryName, as described in [6]. Clients must only retrieve these attributes from a subentry by requesting them by name in a baseObject search of the subentry. 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 number 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, however they are subject to access control restrictions. They must not be included if the client performs a subtree search starting from the root. Servers in general will not allow clients to modify these attributes. Wahl, Howes & Kille [Page 5]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 The following attributes of the root DSE are defined in section 5.1.3 of [5]. Additional attributes may be defined in later documents. - administratorAddress: a URL containing address of administrator. - currentTime: the current time. - serverName: the Distinguished Name of the server. - certificationPath: the server's certificate path. - namingContexts: naming contexts held in the server. - subschemaSubentry: subschema subentries known by this server. - altServer: alternative servers in case this one is later unavailable. - supportedExtension: list of supported extended operations. - supportedControl: list of supported session controls. If the server does not master or shadow entries and does not know the locations of schema information, the subschemaSubentry attribute must not be present in the root DSE. If the server holds master or shadow copies of directory entries under one or more schema rules, there may be any number of values of the subschemaSubentry attribute in the root DSE. 4. Elements of Protocol The LDAP protocol is described using Abstract Syntax Notation 1 [3]. It is typically transferred using a subset of the Basic Encoding Rules. In order to support future extensions to this protocol, clients and servers must ignore elements of SEQUENCEs whose tags they do not recognize. Note that unlike X.500, each change to the LDAP protocol other than through the extension mechanisms will have a different version number. A client will indicate the version it supports as part of the bind request, described in section 4.1.2. If a client has not sent a bind, the server MUST assume that version 3 is supported in the client (since version 2 required that the client bind first). 4.1. Common Elements This section describes the LDAPMessage envelope PDU 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: Wahl, Howes & Kille [Page 6]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 LDAPMessage ::= SEQUENCE { messageID MessageID, cldapUserName LDAPDN OPTIONAL, protocolOp CHOICE { bindRequest BindRequest, bindResponse BindResponse, unbindRequest UnbindRequest, searchRequest SearchRequest, searchResEntry SearchResultEntry, searchResDone SearchResultDone, searchResRef SearchResultReference, searchResFull SearchResultFull, modifyRequest ModifyRequest, modifyResponse ModifyResponse, addRequest AddRequest, addResponse AddResponse, delRequest DelRequest, delResponse DelResponse, modDNRequest ModifyDNRequest, modDNResponse ModifyDNResponse, compareRequest CompareRequest, compareResponse CompareResponse, abandonRequest AbandonRequest, sessionRequest SessionRequest, sessionResponse SessionResponse, extendedReq ExtendedRequest, extendedResp ExtendedResponse } } 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 cldapUserName. All LDAPMessage envelopes encapsulating responses contain the messageID value of the request LDAPMessage. The message ID is required to 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 another request if the first request is outstanding. If it does so, the behavior is undefined. Typically a client will increment a counter for each request. For all requests except for search, unbind and abandon, the message ID is outstanding until the client receives the response for that operation. For a searchRequest which has not been abandoned, the message ID is outstanding until the SearchResultDone for that search is received. Wahl, Howes & Kille [Page 7]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 A client must not reuse the message id of an abandonRequest or 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. The cldapUserName identifies the requesting user for this message. It is only present for backwards compatibility with RFC 1798, if this LDAPMessage is carried in a connectionless transport protocol, such as UDP. Its significance is equivalent to a bind with a zero-length password. When the LDAP session is carried in a connection-oriented transport protocol this field must be absent. LDAPv3 client implementors must not use this field in connectionless requests, but instead concatenate a bind request with the other operations in the request. Concatenation and connectionless transport are described in section 5.1.3. 4.1.2. String Types The LDAPString is a notational convenience to indicate that, although strings of LDAPString type encode as OCTET STRING types, the ISO 10646 [15] character set (a superset of Unicode) is used, encoded following the UTF-8 algorithm [16]. Note that in the UTF-8 algorithm, characters which are the same as ASCII (0000 through 007F) 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 dotted-decimal representation of an OBJECT IDENTIFIER. LDAPOID ::= OCTET STRING For example, 1.3.6.1.4.1.1466.1.2.3 4.1.3. Distinguished Name and Relative Distinguished Name An LDAPDN and a RelativeLDAPDN are respectively defined to be the representation of a Distinguished Name and a Relative Distinguished Name after encoding according to the specification in [4], such that <distinguished-name> ::= <name> <relative-distinguished-name> ::= <name-component> where <name> and <name-component> are as defined in [4]. LDAPDN ::= LDAPString RelativeLDAPDN ::= LDAPString Only Attribute Types can be present in a relative distinguished name component; the options of Attribute Descriptions (next section) must not be used in specifying distinguished names. Wahl, Howes & Kille [Page 8]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 4.1.4. Attribute Type and Description An AttributeType takes on as its value the textual string associated with that AttributeType in its specification. This string must begin with a letter, and only contain ASCII letters and digit characters. If this string is not known, the AttributeType will take the ASCII representation of its OBJECT IDENTIFIER, as decimal digits with components separated by periods, e.g., "2.5.4.10". The attribute type strings which are used in this version of LDAP are described in [5]. They are case insensitive. AttributeType ::= LDAPString An AttributeDescription is a superset of the definition of the AttributeType. It has the same ASN.1 definition, but allows additional options to be specified. They are also case insensitive. AttributeDescription ::= LDAPString A value of AttributeDescription is based on the following BNF: <AttributeDescription> ::= <AttributeType> [ ";" <options> ] <options> ::= <option> | <option> ";" <options> <option> ::= <language-option> | <binary-option> | <dynamic-option> <language-option> ::= "lang=" <lang-code> <lang-code> ::= <printable-ascii> <binary-option> ::= "binary" <dynamic-option> ::= "dynamic" If the "binary" option is present, this overrides any string-based encoding representation defined for that attribute in [5]. Instead the attribute is to be transferred as an encoded binary value [11]. If the "lang=" option is present, this associates a natural language with values for that attribute. The binary and language options may both be present in an AttributeDescription. (The language code has no effect on the character set encoding for string representations of DirectoryString syntax values; UTF-8 is always used). If the "dynamic" option is present, this implies that the values are not permanent parts of the directory entry and may disappear unexpectedly. Wahl, Howes & Kille [Page 9]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 Examples of valid AttributeDescription: CN givenName;lang=en-US CN;lang=ja-JP-kanji CN;lang=ja-JP-romaji userCertificate;binary 1.3.6.1.4.1.1466.99.98.97;binary;dynamic An AttributeDescription with one or more options is treated as a subtype of the attribute without any options. Options are never exclusive and may be listed in any order. Not all options are applicable not every attribute, however. For example, if a client requests a "description" attribute, the server may return an attribute "description;lang=fr". However if the client requests a "description;lang=en", the server must not return "description" or "description;lang=fr", but may return "description;lang=en;dynamic". Later documents may define additional options. 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. Attribute Value A field of type AttributeValue takes on as its value either an octet string encoding of a AttributeValue data type, or an OCTET STRING containing an encoded binary value, depending on whether the "binary" option is present in the companion AttributeDescription to this AttributeValue. The definition of string encodings for different syntaxes and types may be found in companions to this document, in particular [5]. AttributeValue ::= OCTET STRING Note that there is no defined limit on the size of this encoding; thus PDUs including multi-megabyte attributes (e.g. photographs) may be returned. If the client has limited memory or storage capabilities it may wish to set the attrSizeLimit session control before invoking a search operation. Clients and server implementors should be aware that attributes whose type names they do not recognize may have an arbitrary and non-printable syntax. Implementations must not either simply display or attempt to decode as ASN.1 a value if its syntax is not known. The implementation may attempt to discover the subschema subentry and retrieve the value of attributeTypes from it. Wahl, Howes & Kille [Page 10]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 4.1.6. Attribute Value Assertion The AttributeValueAssertion type definition is similar to the one in the X.500 directory standards. It contains an attribute description and a equality matching assertion suitable for that type. AttributeValueAssertion ::= SEQUENCE { attributeDesc AttributeDescription, assertionValue AssertionValue } AssertionValue ::= OCTET STRING If the "binary" option is present in attributeDesc, this signals to the server that the assertionValue is a binary encoding of the assertion value. For all the string-valued user attributes described in [5], the assertion value syntax is the same as the value syntax. Note however that the assertion syntax may be different than the value syntax for operational attributes or for non-equality matching rules. 4.1.7. Attribute An attribute consists of a type and one or more values of that type. (Though attributes must have at least one value when stored, due to access control restrictions the set may be empty when transferred in protocol. This is described in section 4.5.2, concerning the PartialAttributeList type.) Attribute ::= SEQUENCE { type AttributeDescription, vals SET OF AttributeValue } 4.1.8. Matching Rule Identifier An X.501(1993) Matching Rule is identified in the LDAP protocol by the ASCII representation of its OBJECT IDENTIFIER, either as one of the strings given in [5], or as decimal digits with components separated by periods, e.g. "caseIgnoreIA5Match" or "1.3.6.1.4.1.453.33.33". MatchingRuleId ::= LDAPString 4.1.9. Result Message The LDAPResult is the construct used in this protocol to return success or failure indications from servers to clients. In response to various requests, servers will return responses containing fields of type LDAPResult to indicate the final status of a protocol operation request. Wahl, Howes & Kille [Page 11]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 LDAPResult ::= SEQUENCE { resultCode ENUMERATED { success (0), operationsError (1), protocolError (2), timeLimitExceeded (3), sizeLimitExceeded (4), compareFalse (5), compareTrue (6), authMethodNotSupported (7), strongAuthRequired (8), -- 9 reserved -- referral (10), -- new adminLimitExceeded (11), -- new unavailableCriticalExtension (12), -- new -- 13-15 unused -- 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), resultsTooLarge (70), -- cl only affectsMultipleDSAs (71), -- new -- 72-79 unused -- other (80) }, -- 81-90 reserved for APIs -- matchedDN LDAPDN, errorMessage LDAPString, referral [3] Referral OPTIONAL } Wahl, Howes & Kille [Page 12]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 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. If a client receives a result code which is not listed above, it is to be treated as an unknown error condition. The errorMessage field of this construct may, at the servers option, be used to return a string containing a textual, human-readable 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 resultCodes of noSuchObject, aliasProblem, invalidDNSyntax and aliasDereferencingProblem, the matchedDN field is set to the name of the lowest entry (object or alias) in the DIT that was matched. If no aliases were dereferenced while attempting to locate the entry, this will be a truncated form of the name provided. The matchedDN field is to be set to a NULL DN (a zero length string) with all other result codes. 4.1.10. Referral The referral field is present in an LDAPResult if the LDAPResult.resultCode field value is referral, and absent with all other result codes. It contains a reference to another server (or set of servers) which may be accessed via LDAP or other protocols. At least one LDAPURL must be present in the Reference. Referral ::= SEQUENCE OF LDAPURL LDAPURL ::= LDAPString -- limited to characters permitted in URLs The client may contact any of the listed URLs [14] of servers to continue the request. Each server in the list must be capable of processing the operation and presenting a consistent view of the DIT to the client. (The mechanisms for how servers achieve this are outside the scope of this document.) URLs for servers implementing the LDAP protocol are written according to [9]. If an alias was dereferenced, the dn part of the URL must be present, with the new target object name. If this is present, the client must use this name in its next request to progress this search, 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 change the filter in a referral for a search operation. If the filter part of the URL is present in an LDAPURL, the client must use this filter in its next request to progress this search, and if it is not present the client use the same filter as it used for that search. Note that UTF-8 characters appearing in a DN or search filter may not be legal for URLs (e.g. spaces) and must be escaped using the % method in RFC 1738. Wahl, Howes & Kille [Page 13]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 Other kinds of URLs may be returned so long as the operation could be performed using that protocol, and the client has indicated (in a session control) that it could support that protocol. If the client has not indicated that it is capable of handling referrals, the server must attempt to progress the referral on behalf of the client. Only if it fails to do so may it return a referral, and the URLs in this referral must be of the LDAP form. 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 } 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 should just set this parameter to the version it desires. The client may request version 2, in which case the server must implement only the protocol as described in [2], and not return any v3-specific result codes or protocol fields. - name: The name of the directory object that the client wishes to bind as. This field may take on a null value (a zero length string) for the purposes of anonymous binds, when authentication has been performed at a lower layer, or when using SASL credentials with a mechanism that includes the LDAPDN in the credentials. - authentication: information used to authenticate the name, if any, provided in the Bind Request. Upon receipt of a Bind Request, a protocol server will authenticate the requesting client, if necessary. The server will then return a Bind Response to the client indicating the status of the authentication. Wahl, Howes & Kille [Page 14]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 4.2.1. Sequencing of the Bind Request For some 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 should drop the underlying connection. Clients must not invoke operations between two Bind requests made as part of a multi-stage bind. Unlike LDAP v2, the client need not send a Bind Request in the first PDU of the connection. The client may request any operations and the server must treat these as unauthenticated (unless authentication has already occurred at a lower layer). If the server requires that the client bind first, the server must reject any request other than binding or unbinding with the "operationsError" result. If the client did not bind before sending a request and receives an operationsError, it must 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 an association to change their credentials. A subsequent bind process has the effect of abandoning all search and compare operations outstanding. Authentication or controls from earlier binds are subsequently ignored, and so if the bind fails, the connection will be treated as anonymous. Clients must resend their session controls if needed after rebinding, as session controls may be reset to defaults by servers. 4.2.2 Authentication and Other Security Services The simple authentication option provides minimal authentication facilities, with the contents of the authentication field consisting only of a cleartext password. Note that the use of cleartext passwords is not recommended over open networks when there is no authentication or encryption being performed by a lower layer; see the "Security Considerations" section. If no authentication is to be performed, or has been performed at a lower layer, then the simple authentication option should be chosen, and the password be of zero length. (This is often done by LDAPv2 clients.) The sasl choice allows for any mechanism defined for use with SASL [17] or listed in Appendix B to be used. 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. Wahl, Howes & Kille [Page 15]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 4.2.3. Bind Response The Bind Response is defined as follows. BindResponse ::= [APPLICATION 1] SEQUENCE { COMPONENTS OF LDAPResult, supportedVersion [5] INTEGER (1..127) OPTIONAL, serverURL [6] LDAPURL OPTIONAL, serverCreds [7] AuthenticationChoice OPTIONAL } A 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 protocolError authMethodNotSupported strongAuthRequired referral inappropriateAuthentication invalidCredentials unavailable unavailableCriticalExtension If the client receives a BindResponse response where the resultCode was protocolError and the supportedVersion field is absent, it must close the connection as the server will be unwilling to accept further operations. (This is for compatibility with earlier versions of LDAP.) The serverURL contains the URL of this LDAP server, if it wishes to provide an "authoritative" URL for itself. Typically this will be a URL of the "ldap:" type, indicating the official host name, and the name part of the URL will contain the encoded name of the server itself. The serverCreds 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. The supportedVersion field contains the minimum of the version supplied by the client in the BindRequest and the highest version of LDAP supported in the server. If the client and server both implement the protocol described in this document it will have the value 3. This field will be absent when responding to a version 2 or earlier client. Wahl, Howes & Kille [Page 16]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 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. All session controls will be forgotten and search result caches will be cleared when a connection closes. 4.4. Session Control Operation SessionRequest ::= [APPLICATION 17] Controls SessionResponse ::= [APPLICATION 18] SEQUENCE { COMPONENTS OF LDAPResult, unsupportedCtls [12] SEQUENCE OF LDAPString } Controls ::= SEQUENCE OF SEQUENCE { controlType LDAPString, criticality BOOLEAN DEFAULT FALSE, controlValue OCTET STRING } Session Controls are requests made by the client which affect its interaction with the server. Controls are not saved after a session unbinds or disconnects abruptly, and do not affect other sessions to this or other servers. Session controls do not affect operations which have already been requested on this connection, e.g. if the client sends a search request and subsequently sends a sessionControlRequest while the server is in the middle of sending responses, the session controls which were in force when the search operation began still apply for all the results of that search until the SearchResultDone is returned. Session controls are not cumulative, and a session request will override all session controls which were set by a previous request. If a control was set on a previous request and was not mentioned in a subsequent request, it will be reset by the server to its default value. (This permits session controls, such as supportedProtocol, to have multiple values.) If the server is not capable of setting one or more requested controls, it should set as many as possible. If any of the controls which the server could not set are marked as critical, it must return the unavailableCriticalExtension error. The controlType field must either be a string defined in this section, or a dotted-decimal representation of an OBJECT IDENTIFIER. This will aid in preventing conflicts between privately-defined control extensions. String names are case insensitive. Wahl, Howes & Kille [Page 17]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 The following controls have been defined: NAME CRITICAL? VALUE CONTAINS DEFAULT =================== ================ =============== ============= attrSizeLimit clients option integer no limit dontUseCopy clients option boolean FALSE usePartialCopy clients option boolean FALSE referringServer non-critical URL none chainingProhibited clients option boolean FALSE supportedProtocol non-critical protocol name none useAliasOnUpdate clients option boolean FALSE manageDsaIT critical boolean FALSE preferredLanguage non-critical string no preference The attrSizeLimit control may be critical or non-critical at the client's request. The value field contains either an empty string, implying no limit, or a string representation of a positive integer, e.g. "10000". The default if this control is not present is that there is no limit. The attrSizeLimit number is a size in bytes of the largest encoded value which the client is capable of processing. Servers should not return attribute values in a search response which are larger than this size. (If attribute values are excluded because of this control, the incompleteEntry attribute must be present with the value TRUE in the SearchResultEntry). The dontUseCopy control may be critical or non-critical at the client's request. The value field contains either "TRUE" or "FALSE". The default if this control is not set is "FALSE". This control only affects the Search and Compare operations. If present and set to "TRUE", servers should not make use of information from cached or shadowed copies of entries in these operations. This control overrides any setting of the usePartialCopy control. The usePartialCopy control may be critical or non-critical at the client's request. The value field contains either "TRUE" or "FALSE". The default if this control is not set is "FALSE". This control only affects the Search and Compare operations. If the dontUsecopy control is set to "TRUE", this control is ignored. If usePartialCopy is present and set to "TRUE", then if a contacted server holds at least one attribute in a shadow or cached copy of an entry, then that entry may be used to satisfy the request, even if not all the requested attributes are in the shadowed copy. If this control is "FALSE" and dontUseCopy is also "FALSE", the server must not return attributes from an incomplete shadow copy of an entry unless none of the requested attributes or their subtypes were excluded from the shadow copy. (How servers replicate information and configure shadowing is outside the scope of this specification.) The referringServer control is always non-critical. The value field contains the URL of another server which referred an operation to this server. This control must only be present if the connection is being made only to process a referral. If the connection will be held open to handle referrals from multiple servers this control must be omitted. There is no protocol effect of this control; it is used to assist in tracing knowledge inconsistencies in the distributed directory. Wahl, Howes & Kille [Page 18]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 The chainingProhibited control may be critical or non-critical at the client's request. The value must be either "TRUE" or "FALSE". To aid interoperability with LDAPv2 clients, the default if this control is not set is "FALSE". If this control is present and set to "TRUE", the server must not contact any other servers as part of processing operations requested by this client, if it would be possible to instead return to the client a referral. If the server is a gateway to X.500, and DAP is not a supported client referral protocol (see next paragraph), the server must set the chainingProhibited service control on any DAP or DSP requests it makes. The supportedProtocol control is always non-critical. The field is a string name of a protocol which the client implements. The name of the protocol may be "ldap", "cldap", "dap", any IANA-assigned protocol name or URL mechanism, or "*" to indicate that any type of referral may be returned. If this control is present, a server must return a referral, rather than itself chain to another server using one of the indicated protocol. This control may be present multiple times in a session control if the client wishes to name multiple protocols it supports. If the supportedProtocol control is absent and the server is capable of contacting other servers, then it must not return results with referrals, as described in 4.1.10, or SearchResultContinuation, as described in 4.5.3, unless the server is not capable of contacting other servers, in which case it may return a referral or continuation containing a URL of type "LDAP". It is recommended that clients, as a minimum, support LDAP referrals, and set the supportedProtocol control to be "ldap". The useAliasOnUpdate control may be critical or non-critical at the client's request. The value must be either "TRUE" or "FALSE". To aid interoperability with LDAPv2 clients, the default if this control is not set is "FALSE". If present and set to TRUE, the server must permit alias names to be used as components of a Distinguished Name in Add, Modify and Delete operations. If the server is a gateway to X.500, it must set the useAliasOnUpdate critical extension on any DAP/DSP AddEntry, ModifyEntry and RemoveEntry requests it makes if this control is "TRUE". This control does not affect the ModifyDN operation, which only allows Distinguished Names to be provided. The manageDsaIT control is always critical. The value must be either "TRUE" or "FALSE". The default, if this control is not set, is "FALSE". This control affects the name resolution behavior of the server to permit a manager to read and modify knowledge references and other X.500 server-specific attributes. If the server is a gateway to X.500, it must set the manageDsaIT critical extension, as well as the appropriate common arguments, on any DAP/DSP requests it makes, based on this control. Wahl, Howes & Kille [Page 19]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 The preferredLanguage control is always non-critical. The use of this control and its impact on the directory will be defined in future drafts. The default if this control is not set, is that there is no preferred language. 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, or a whole subtree of entries. 4.5.1. Search Request The Search Request is defined as follows: SearchRequest ::= [APPLICATION 3] SEQUENCE { baseObject LDAPDN, scope ENUMERATED { baseObject (0), singleLevel (1), wholeSubtree (2) }, derefAliases ENUMERATED { neverDerefAliases (0), derefInSearching (1), derefFindingBaseObj (2), derefAlways (3) }, sizeLimit INTEGER (0 .. maxInt), timeLimit INTEGER (0 .. maxInt), typesOnly BOOLEAN, filter Filter, attributes AttributeDescriptionList, pageSizeLimit [0] INTEGER OPTIONAL, sortKeys [1] SortKeyList OPTIONAL, prevSearchId [2] MessageID OPTIONAL, startLocation [3] INTEGER OPTIONAL } SortKeyList ::= SEQUENCE OF SEQUENCE { attributeType AttributeType, orderingRule [0] MatchingRuleId OPTIONAL, reverseOrder [1] BOOLEAN DEFAULT FALSE } Filter ::= CHOICE { and [0] SET OF Filter, or [1] SET OF Filter, not [2] Filter, equalityMatch [3] AttributeValueAssertion, substrings [4] SubstringFilter, greaterOrEqual [5] AttributeValueAssertion, lessOrEqual [6] AttributeValueAssertion, present [7] AttributeType, approxMatch [8] AttributeValueAssertion, extensibleMatch [9] MatchingRuleAssertion } Wahl, Howes & Kille [Page 20]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 SubstringFilter ::= SEQUENCE { type AttributeDescription, -- at least one must be present substrings SEQUENCE OF CHOICE { initial [0] LDAPString, any [1] LDAPString, final [2] LDAPString } } MatchingRuleAssertion ::= SEQUENCE { matchingRule [1] MatchingRuleId OPTIONAL, type [2] AttributeType OPTIONAL, matchValue [3] AssertionValue, dnAttributes [4] BOOLEAN DEFAULT FALSE } Parameters of the Search Request are: - baseObject: An LDAPDN that is the base object entry relative to which the search is to be performed. - scope: An indicator of the scope of the search to be performed. The semantics of the possible values of this field are identical to the semantics of the scope field in the X.511 Search Operation. - derefAliases: An indicator as to how alias objects are to be 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; derefFindingBaseObject: dereference aliases in locating the base object of the search, but not when searching subordinates of the base object; derefAlways: dereference aliases both in searching and in locating the base object of the search. - sizelimit: A sizelimit that restricts the maximum number of entries to be returned as a result of the search. A value of 0 in this field indicates that no sizelimit restrictions are in effect for the search. - timelimit: A timelimit that restricts the maximum time (in seconds) allowed for a search. A value of 0 in this field indicates that no timelimit restrictions are in effect for the search. - typesOnly: An indicator as to whether search results will contain both attribute types and values, or just attribute types. Setting this field to TRUE causes only attribute types (no values) to be returned. Setting this field to FALSE causes both attribute types and values to be returned. Wahl, Howes & Kille [Page 21]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 - 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 may be used to form boolean 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. 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. If the type field is present and matchingRule is present, the matchingRule must be one permitted for use with that type. If the dnAttributes field is set to TRUE, the match is applied against all the attributes in an entry's distinguished name as well. (Editors note: The dnAttributes field is present so that there does not need to be multiple versions of generic matching rules such as wordMatch, one to apply to entries and another to apply to entries and dn attributes as well). - attributes: A list of the attributes from each entry found as a result of the search to be returned. An empty list signifies that all user attributes from each entry found in the search are to be returned, as does the special attribute description string "*". (the latter technique allows the client to request all user attributes along with selected operational attributes). If the client does not want any attributes returned, it can request only the attribute with OID "1.1". Attributes must be named at most once in the list, and are returned at most once in an entry. Client implementors should note that even if all user attributes are requested, some attributes of the entry may not be included in search results due to access control restrictions. Furthermore, servers will not return operational attributes, such as modifyRights or attributeTypes, unless they are listed by name, since there may be extremely large number of values for certain operational attributes. (A list of operational attributes for use in LDAP is given in [5].) - pageSizeLimit: if present, then if more entries are to be returned than the pageSizeLimit, the server must return only as many as this limit before returning the SearchResultDone response. If the same or fewer entries than this limit are to be returned, the server must return all the entries and the SearchResultDone response. The pageSizeLimit does not affect SearchResultReference responses, which are not counted as entries and of which any number may be returned by the server. If operating over connectionless data transport, the client must not set this field. Wahl, Howes & Kille [Page 22]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 If a pageSizeLimit was set and reached during the search, the client will be able to request more of the entries using a subsequent SearchRequest with the prevSearchId field present. It is strongly recommended that clients include the sortKeys field when including this field. - sortKeys: If this field is present, then it specifies one or more attribute types and matching rules, and the returned entries must be sorted in order based on these types. If the reverseOrder field is set to TRUE, then the entries will be presented in reverse sorted order. Only if the server does not recognize any of the attribute types, the ordering rule associated with an attribute type is not applicable, or none of the attributes in the search responses are of these types, then the sortKeys field is not used and result entries are returned in random order. If the server does not support sorting with the requested attributes or matching rules, then it must return only protocolError (which is what an LDAPv2 server would return), undefinedAttributeType or inappropriateMatching and no searchResultEntry or searchResultReference responses. If the sortKeys field is absent, there is no defined order for returning entries in a search result. - prevSearchId: If this field is present, this informs the server that, with possibly the exception of the value of the startLocation field, this request is identical to a searchRequest made previously on this association. If the server does not recognize this as the message id of a previous search operation, it must silently ignore this field and perform this search as normal. The client must ensure that all fields, other than startLocation, are the same as in the earlier search, otherwise the contents of the entries returned from this search are not defined. If clients are performing the same search more than twice on an association, then the prevSearchId field of all but the first search must contain the messageID of that first search. - startLocation: this field may be present if the pageSizeLimit is present. After filtering and selecting the entries to be returned in a search, the server will discard this many entries before starting to return SearchResultEntry responses. Thus setting startLocation 0 is the same as not including a startLocation field. If the client sends a value of startLocation which is larger than the number of entries in the result, the server will only return any of the SearchResultReference responses, and then the SearchResultDone response. (The server should indicate in the SearchResultDone a value of totalCount which the client may use to make a better choice of startLocation in a subsequent search). The startLocation does not affect SearchResultReference responses, which are not counted as entries. Wahl, Howes & Kille [Page 23]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 It is strongly recommended that clients include the sortKeys field when including this field. If the client includes the attribute type name 'modifyRights' in the search request attribute type list when performing a baseObject search, then the server may return the modifyRights attribute as part of the response attributes for that entry. The value of this attribute is described in section 6.2.2.1 of [5], and corresponds to the X.511(93) ModifyRights field of the ReadResponse. Note that an X.500 "list"-like operation can be emulated by the client requesting a one-level LDAP search operation with a filter checking for the existence of the objectClass attribute, and that an X.500 "read"-like operation can be emulated by a base object LDAP search operation with the same filter. A server which provides a gateway to X.500 is not required to use the Read or List operations, although it may choose to do so. If the search filter includes an equality match of the objectClass attribute and the value "subentry", then if the server is converting to an X.500 protocol, the subentries service control must be set. Thus clients must not search for both subentries and ordinary entries with a single 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, SearchResultDone or SearchResultFull data types. SearchResultEntry ::= [APPLICATION 4] SEQUENCE { objectName LDAPDN, attributes PartialAttributeList } PartialAttributeList ::= SEQUENCE OF SEQUENCE { type AttributeDescription, vals SET OF AttributeValue } -- implementors should note that the PartialAttributeList may have -- zero elements (if none of the attributes of that entry were -- requested, or could be returned), and that the vals set may also -- have zero elements (if types only was requested, or all the values -- exceeded the attribute size limit or were excluded because of -- access control). SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL -- at least one LDAPURL element must be present SearchResultDone ::= [APPLICATION 5] SEQUENCE { COMPONENTS OF LDAPResult, totalCount [8] INTEGER OPTIONAL } Wahl, Howes & Kille [Page 24]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 SearchResultFull ::= SEQUENCE OF CHOICE { entry SearchResultEntry, reference SearchResultReference, resultCode SearchResultDone } 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 SearchResultReferences may come in any order. Following all the SearchResultReference responses and all SearchResultEntry responses up to a pageSizeLimit (if any), the server will return a response containing the SearchResultDone, which contains an indication of success, or detailing any errors that have occurred. If the LDAP session is operating over a connectionless transport such as UDP, the server will return to the client only one response to the search, an LDAPMessage containing a SearchResultFull data type. All (if any) but the last element of the SEQUENCE OF must be of the SearchResultEntry or SearchResultReference types, and the last must be of the SearchResultDone type. The SearchResultFull is never returned over a connection-oriented transport. 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), or in a language-specific subtype (indicated by the AttributeDescription in the response having the language option present). The following are not strictly attributes of an entry (or a subentry), but may appear in the result list if requested. - entryName. This operational attribute is maintained by the server and appears to be present in each entry. The value of this attribute is the distinguished name of the entry from which it is read. It is expected that the client would request and the server would return this attribute in binary. - modifyRights. Each value is the encoding of an element of modifyRights. The attribute is specific to the particular search operation and the requestor, and must not be cached or replicated. Wahl, Howes & Kille [Page 25]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 - incompleteEntry. This attribute's value is TRUE if one or more attributes are not present in the PartialAttributeList, because their size would have exceeded the attribute size limit, or if a partial shadow copy of the entry was used to satisfy the request and some requested attributes are not returned. It is never set just because typesOnly was set to TRUE, or because a requested attribute was not actually present in the entry. - fromEntry. The server may return this attribute's value as FALSE if it is known that the search is based upon a shadow or cached copy of the entry, and may return it as TRUE if the server masters the entry. In a SearchResultEntry, as an encoding optimization, the value of the objectName LDAPDN may have a trailing '*' character to refer to the baseObject of the corresponding searchRequest. For example, if the baseObject is specified as "o=UofM, c=US", then the following objectName LDAPDNs in a response would have the indicated meanings objectName returned actual LDAPDN denoted ____________________________________________________ "*" "o=UofM, c=US" "cn=Babs Jensen, *" "cn=Babs Jensen, o=UofM, c=US" If the pageSizeLimit field was present, the server may indicate the total number of entries which could have matched the search filter in the field totalCount of the SearchResultDone. The total count would be the same or greater than the number of SearchResultEntry responses returned at this time. If it is greater, then the server did not return all the responses because the pageSizeLimit was reached. This field is not affected by any requested startLocation field. Client implementors should note that subsequent search requests with the same fields may return a different value for totalCount if the DIT is being modified by other users. The totalCount field must be absent if the pageSizeLimit field was not included in the request. Servers should not return the resultCode sizeLimitExceeded merely because a pageSizeLimit was reached. 4.5.3. Continuation References in the Search Result If the server was able to locate the entry referred to by the baseObject but was unable to search all the entries in the scope at and under the baseObject, the server may return one or more SearchResultReference, each containing a reference to another set of servers for continuing the operation. The server must return at most one SearchResultReference for a new subordinate base object with a particular scope and filter. A server must not return a 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. Wahl, Howes & Kille [Page 26]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 The SearchResultReference is of the same data type as the Referral. A URL in a SearchResultReference may only be included if the client has indicated (in the session controls) that it is able to handle that protocol. If the client has not indicated any protocols which the server could use to return in a SearchResultReference, the server must itself process the entire search. If the server could not contact all other servers, it may return one or more SearchResultReference for unexplored subtrees, and must indicate also that only partial results were returned by setting the resultCode in the SearchResultDone to be something other than success, such as timeLimitExceeded. URLs for servers implementing the LDAP protocol are written according to [9]. The dn part must be present in the URL, with the new target object name. The client must use this name in its next request. Some servers (e.g. participating in distributed indexing) may change the filter. If the filter part of the URL is present in an LDAP URL, the client must use this filter in its next request to progress this search, and if the filter is absent the client will use the same filter as it used for that search. Other kinds of URLs may be returned so long as the operation could be performed using that protocol, and the client has indicated (in a session control) that it is able to handle that protocol. The name of an unexplored subtree in a SearchResultReference need not be subordinate to the base object if an alias was dereferenced, however it must not be a prefix of the base object, otherwise the client will loop. (Client implementations must detect loops; see section 6.2.) Note: the "X.500 Non-Specific Subordinate Reference" is not permitted in LDAP. Servers must not return multiple SearchResultReference for the same subtree, and any one of (not all of) the servers listed in a SearchResultReference may be contacted to perform the entire search in a particular subtree. 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 in which chainingProhibited is set and referrals are permitted, and the filter is objectClass=*, the server may return the following responses: Wahl, Howes & Kille [Page 27]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 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 (entries = 2) Client implementors should note that when following a SearchResultReference, additional SearchResultReference may be generated. Continuing the example, if the client contacted the server (hostb) and issued the search for the subtree "OU=People,O=MNN,C=WW", the server might respond as follows: SearchResultEntry for OU=People,O=MNN,C=WW SearchResultReference { ldap://hoste/OU=Managers,OU=People,O=MNN,C=WW } SearchResultReference { ldap://hostf/OU=Consultants,OU=People,O=MNN,C=WW } 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 unless the useAliasOnUpdate session control is set to TRUE. Wahl, Howes & Kille [Page 28]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 - A list of modifications to be performed on the entry to be modified. The entire list of entry modifications must be performed in the order they are listed, as a single atomic operation. While individual modifications may violate the directory schema, the resulting entry after the entire list of modifications is performed must conform to the requirements of the directory schema. The values that may be taken on by the 'operation' field in each modification construct have the following semantics respectively: add: add values listed to the given attribute, creating the attribute if necessary; delete: delete values listed from the given attribute, removing the entire attribute if no values are listed, or if all current values of the attribute are listed for deletion; replace: replace all existing values of the given attribute with the new values listed, creating the attribute if it did not already exist. A replace with no value will delete the entire attribute. 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. 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 a DAP ModifyEntry operation, and different implementations of LDAP-DAP gateways may use different means of representing the change. The final effect of the operations on the entry will be identical. Wahl, Howes & Kille [Page 29]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 4.7. Add Operation The Add Operation allows a client to request the addition of an entry into the directory. The Add Request is defined as follows: AddRequest ::= [APPLICATION 8] SEQUENCE { entry LDAPDN, attributes AttributeList } AttributeList ::= SEQUENCE OF SEQUENCE { type AttributeDescription, vals SET OF AttributeValue } Parameters of the Add Request are: - entry: the Distinguished Name of the entry to be added. Note that all components of the name except for the last RDN component must exist for the add to succeed. Note also that the server will not dereference any aliases in locating the entry to be added (unless the useAliasOnUpdate session control is TRUE), and that there are never any entries subordinate to an alias entry. - attributes: the list of attributes that make up the content of the entry being added. Clients must included distinguished values in this list. The result of the add attempted by the server upon receipt of a Add Request is returned in the Add Response, defined as follows: AddResponse ::= [APPLICATION 9] LDAPResult 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. 4.8. Delete Operation The Delete Operation allows a client to request the removal of an entry from the directory. The Delete Request is defined as follows: DelRequest ::= [APPLICATION 10] LDAPDN The Delete Request consists of the Distinguished Name of the entry to be deleted. Note that the server will not dereference aliases while resolving the name of the target entry to be removed, unless the useAliasOnUpdate session control is TRUE. 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 Wahl, Howes & Kille [Page 30]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 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. Note that only leaf objects (with no subordinates) may be deleted with this operation. 4.9. Modify DN Operation The Modify DN Operation allows a client to change the last 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 name of the entry to be changed. - newrdn: the RDN that will form the last component of the new name. - deleteoldrdn: a boolean parameter that controls whether the old RDN attribute values is to be retained as attributes of the entry, or deleted from the entry. - newSuperior: if present, this is the name of the entry which becomes the immediate superior of the existing entry. The result of the name change attempted by the server upon receipt of a Modify DN Request is returned in the Modify DN Response, defined as follows: ModifyDNResponse ::= [APPLICATION 13] LDAPResult Upon receipt of a ModifyDNRequest, a server will attempt to perform the name change. The result of the name change attempt will be returned to the client in the Modify DN Response. The attributes that make up the old RDN are deleted from the entry, or kept, depending on the setting of the deleteoldrdn parameter. 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. In general clients must not expect to be able to perform arbitrary movements of entries and subtrees. Wahl, Howes & Kille [Page 31]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 4.10. Compare Operation The Compare Operation allows a client to compare an assertion provided with an entry in the directory. The Compare Request is defined as follows: CompareRequest ::= [APPLICATION 14] SEQUENCE { entry LDAPDN, ava AttributeValueAssertion } Parameters of the Compare Request are: - entry: the name of the entry to be compared with. - ava: the assertion with which an attribute in the entry is to be compared. The result of the compare attempted by the server upon receipt of a Compare Request is returned in the Compare Response, defined as follows: CompareResponse ::= [APPLICATION 15] SEQUENCE { COMPONENTS OF LDAPResult, matchedSubtype [9] AttributeDescription OPTIONAL } When the resultCode is compareTrue the matchedSubtype field is permitted to contain the name of the attribute whose value matched the ava in the Compare operation. Servers which do not implement attribute hierarchies will omit this element. Upon receipt of a Compare Request, a server will attempt to perform the requested comparison. The result of the comparison will be returned to the client in the Compare Response. Note that errors and the result of comparison are all returned in the same construct. Note that some directory systems may establish access controls which permit the values of certain attributes (such as userPassword) to be compared but not read. In a search result, it may be that an attribute of that type would be returned, but with an empty set of values. 4.11. Abandon Operation The function of the Abandon Operation is to allow a client to request that the server abandon an outstanding operation. The Abandon Request is defined as follows: AbandonRequest ::= [APPLICATION 16] MessageID The MessageID must be that of a Search or Compare operation which was requested earlier during this association. Other types of operations cannot be abandoned. (The abandon request itself has its own message id. This is distinct from the id of the earlier operation being abandoned.) Wahl, Howes & Kille [Page 32]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 There is no response defined in the Abandon Operation. Upon transmission of an Abandon Operation, a client may expect that the operation identified by the Message ID in the Abandon Request has been abandoned. In the event that a server receives an Abandon Request on a Search Operation in the midst of transmitting responses to the search, that server must cease transmitting entry responses to the abandoned request immediately. Of course, the server must ensure that only properly encoded LDAPMessages are transmitted. Clients must not send abandon requests for the same operation multiple times. Servers must discard abandon requests for message ids it does not recognize, for operations which cannot be abandoned, and for operations which have already been abandoned. 4.12. Extended Operation It may be desirable in some communities to define additional operations for services not available in this protocol, for instance digitally signed operations and results. Thus an extension mechanism has been added in this version of LDAP. 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 operation must have a unique OBJECT IDENTIFIER assigned to it. ExtendedRequest ::= [APPLICATION 23] SEQUENCE { requestName [0] LDAPOID, requestValue [1] OCTET STRING } 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 operation name, it must return only the standard response fields, containing the protocolError result code. 5. Protocol Element Encodings and Transfer Four underlying services are defined here. At a minimum, clients and servers must implement the mapping of LDAP over TCP described in 5.1.1. Wahl, Howes & Kille [Page 33]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 5.1. Mapping Onto BER-based Transport Services This protocol is designed to run over connection-oriented, reliable transports, with all 8 bits in an octet being significant in the data stream. The protocol elements of LDAP are encoded for exchange using the Basic Encoding Rules (BER) [11] of ASN.1 [3]. However, due to the high overhead involved in using certain elements of the BER, the following additional restrictions are placed on BER-encodings of LDAP protocol elements: (1) Only the definite form of length encoding will be used. (2) OCTET STRINGs 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 STRINGs, such as attribute values, unless otherwise noted. 5.1.1. Transmission Control Protocol (TCP) The LDAPMessage PDUs are mapped directly onto the TCP bytestream. Server implementations running over the TCP should provide a protocol listener on the assigned port, 389. 5.1.2. Connection Oriented Transport Service (COTS) The connection is established. No special use of T-Connect is made. Each LDAPMessage PDU is mapped directly onto T-Data. 5.1.3. User Datagram Protocol (UDP) The LDAPMessage PDUs are mapped directly onto UDP datagrams. A datagram may contain one or more concatenated requests. Only one response datagram is returned, containing all the responses concatenated together. The only operations which the client may request are sessionRequest, searchRequest, compareRequest and extendedReq. The server may return sessionResponse, searchResFull, compareResponse and extendedResp. If any of the requests in an incoming datagram generates an error (a result other than success, compareTrue or compareFalse), the server should ignore any following requests in that datagram. Server implementations running over the UDP should provide a protocol listener on the assigned port, 389. Wahl, Howes & Kille [Page 34]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 5.1.4. Secure Socket Layer over TCP (SSL) LDAP is an application protocol which may be carried inside of an Secure Sockets Layer connection [8]. After establishing the SSL connection over TCP, the LDAPMessage PDUs are mapped directly onto the bytestream. Server implementations running over SSL/TCP should provide a protocol listener on the assigned port for LDAP-SSL, port 636. Note: it is expected that future versions of this document may reference an IETF specification for equivalent transport layer security services, should one become available. 6. Implementation Guidelines 6.1. Server Implementations The server must be capable of recognizing all the mandatory attribute type names and implement the syntaxes specified in [5]. Servers may also recognize additional attribute type names. 6.2. Client Implementations 6.2.1. CLDAP Retry For simple lookup applications using the connectionless transport protocol UDP, use of a retry algorithm with multiple servers similar to that commonly used in DNS stub resolver implementations is recommended. The location of a CLDAP server or servers may be better specified using IP addresses (simple or broadcast) rather than names that must first be looked up in another directory such as DNS. 6.2.2. Loop Detection Clients which request referrals must ensure that they do not loop between servers. They must not progress a referral or reference in a subtree search where the new name is a superior of the name requested. They must not repeatedly contact the same server twice with the same target entry name. Some clients may be using a counter that is incremented each time referral handling is handled for an operation, and these kind of clients must be able to handle a DIT with up to ten layers of naming contexts between the root and a leaf entry. 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 [17]. It is also permitted that the server can return its credentials to the client, if it chooses to do so. Wahl, Howes & Kille [Page 35]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 This document also defines a mapping of LDAP over the Secure Sockets Layer (SSL), which can provide strong authentication, integrity and privacy of the connection. Use of cleartext password is strongly discouraged where the underlying transport service cannot guarantee confidentiality. A password hashing mechanism is given in Appendix B. When used with SASL, it should be noted that the name field of the BindRequest is not protected against modification. Thus if there is a client name (LDAPDN) agreed through the negotiation of the credentials, it must take precedence over any value in the unprotected name field. When used with the connectionless transport, no security services are available. There has been some discussion about the desirability of authentication with connectionless LDAP requests. This might take the form of a clear text password (which would go against the current IAB drive to remove such things from protocols) or some arbitrary credentials. It is felt that, in general, authentication would incur sufficient overhead to negate the advantages of the connectionless basis of LDAP. If an application requires authenticated access to the directory then connectionless LDAP is not an appropriate protocol. 8. Acknowledgements This document is an update to RFC 1777, by Wengyik Yeong, Tim Howes, and Steve Kille. It also includes material from RFC 1798, by Alan Young. Design ideas included in this document are based on those discussed in ASID and other IETF Working Groups. The contributions of individuals in these working groups is gratefully acknowledged. 9. Bibliography [1] ITU-T Rec. X.500, "The Directory: Overview of Concepts, Models and Service", 1993. [2] W. Yeong, T. Howes, S. Kille, "Lightweight Directory Access Protocol", RFC 1777, March 1995. [3] ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1) - Specification of Basic Notation", 1994. [4] S. Kille, M. Wahl, "A UTF-8 String Representation of Distinguished Names", INTERNET-DRAFT <draft-ietf-asid-ldapv3-dn-00.txt>. [5] M. Wahl, A. Coulbeck, T. Howes, S. Kille, W. Yeong, C. Robbins, "Lightweight X.500 Directory Access Protocol Standard and Pilot Attribute Definitions", INTERNET-DRAFT <draft-ietf-asid-ldapv3-attributes-02.txt>, August 1996. [6] ITU-T Rec. X.501, "The Directory: Models", 1993. [7] ITU-T Rec. X.520, "The Directory: Selected Attribute Types", 1993. Wahl, Howes & Kille [Page 36]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 [8] A. Freier, P. Karlton, P. Kocher, "The SSL Protocol Version 3.0", INTERNET-DRAFT <draft-freier-ssl-version3-01.txt>, March 1996. [9] T. Howes, M. Smith, "An LDAP URL Format", RFC 1959, June 1996. [10] ITU-T Rec. X.518, "The Directory: Procedures for Distributed Operation", 1993. [11] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules: Basic, Canonical, and Distinguished Encoding Rules", 1994. [12] ITU-T Rec. X.509, "The Directory: Authentication Framework", 1993. [13] ITU-T Rec. X.511, "The Directory: Abstract Service Definition", 1993. [14] T. Berners-Lee, L. Masinter, M. McCahill, "Uniform Resource Locators (URL)", RFC 1738, Dec. 1994. [15] Universal Multiple-Octet Coded Character Set (UCS) - Architecture and Basic Multilingual Plane, ISO/IEC 10646-1 : 1993. [16] M. Davis, UTF-8, (WG2 N1036) DAM for ISO/IEC 10646-1. [17] J. Meyers, "Simple Authentication and Security Layer", INTERNET-DRAFT <draft-myers-auth-sasl-04.txt>, July 1996. 10. Authors' Address Mark Wahl Critical Angle Inc. 4815 W Braker Lane #502-385 Austin, TX 78759 USA EMail: M.Wahl@critical-angle.com Tim Howes Netscape Communications Corp. 501 E. Middlefield Rd. Mountain View, CA 94043 USA Phone: +1 415 254-1900 EMail: howes@netscape.com Wahl, Howes & Kille [Page 37]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 Steve Kille ISODE Consortium The Dome, The Square Richmond TW9 1DT UK Phone: +44-181-332-9091 EMail: S.Kille@isode.com Appendix A - Complete ASN.1 Definition Lightweight-Directory-Access-Protocol-V3 DEFINITIONS IMPLICIT TAGS ::= BEGIN LDAPMessage ::= SEQUENCE { messageID MessageID, cldapUserName LDAPDN OPTIONAL, protocolOp CHOICE { bindRequest BindRequest, bindResponse BindResponse, unbindRequest UnbindRequest, searchRequest SearchRequest, searchResEntry SearchResultEntry, searchResDone SearchResultDone, searchResRef SearchResultReference, searchResFull SearchResultFull, modifyRequest ModifyRequest, modifyResponse ModifyResponse, addRequest AddRequest, addResponse AddResponse, delRequest DelRequest, delResponse DelResponse, modDNRequest ModifyDNRequest, modDNResponse ModifyDNResponse, compareRequest CompareRequest, compareResponse CompareResponse, abandonRequest AbandonRequest, sessionRequest SessionRequest, sessionResponse SessionResponse, extendedReq ExtendedRequest, extendedResp ExtendedResponse } } MessageID ::= INTEGER (0 .. maxInt) maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) -- LDAPString ::= OCTET STRING LDAPOID ::= OCTET STRING Wahl, Howes & Kille [Page 38]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 LDAPDN ::= LDAPString RelativeLDAPDN ::= LDAPString AttributeType ::= LDAPString AttributeDescription ::= LDAPString AttributeDescriptionList ::= SEQUENCE OF AttributeDescription AttributeValue ::= OCTET STRING AttributeValueAssertion ::= SEQUENCE { attributeDesc AttributeDescription, assertionValue AssertionValue } AssertionValue ::= OCTET STRING Attribute ::= SEQUENCE { type AttributeDescription, vals SET OF AttributeValue } MatchingRuleId ::= LDAPString Wahl, Howes & Kille [Page 39]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 LDAPResult ::= SEQUENCE { resultCode ENUMERATED { success (0), operationsError (1), protocolError (2), timeLimitExceeded (3), sizeLimitExceeded (4), compareFalse (5), compareTrue (6), authMethodNotSupported (7), strongAuthRequired (8), -- 9 reserved -- referral (10), -- new adminLimitExceeded (11), -- new unavailableCriticalExtension (12), -- new -- 13-15 unused -- 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), resultsTooLarge (70), -- cl only affectsMultipleDSAs (71), -- new -- 72-79 unused -- other (80) }, -- 81-90 reserved for APIs -- matchedDN LDAPDN, errorMessage LDAPString, referral [3] Referral OPTIONAL } Referral ::= SEQUENCE OF LDAPURL Wahl, Howes & Kille [Page 40]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 LDAPURL ::= LDAPString -- limited to characters permitted in URLs 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 } BindResponse ::= [APPLICATION 1] SEQUENCE { COMPONENTS OF LDAPResult, supportedVersion [5] INTEGER (1..127) OPTIONAL, serverURL [6] LDAPURL OPTIONAL, serverCreds [7] AuthenticationChoice OPTIONAL } UnbindRequest ::= [APPLICATION 2] NULL SessionRequest ::= [APPLICATION 17] Controls SessionResponse ::= [APPLICATION 18] SEQUENCE { COMPONENTS OF LDAPResult, unsupportedCtls [12] SEQUENCE OF LDAPString } Controls ::= SEQUENCE OF SEQUENCE { controlType LDAPString, criticality BOOLEAN DEFAULT FALSE, controlValue OCTET STRING } 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, pageSizeLimit [0] INTEGER OPTIONAL, sortKeys [1] SortKeyList OPTIONAL, prevSearchId [2] MessageID OPTIONAL, startLocation [3] INTEGER OPTIONAL } Wahl, Howes & Kille [Page 41]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 SortKeyList ::= SEQUENCE OF SEQUENCE { attributeType AttributeType, orderingRule [0] MatchingRuleId OPTIONAL, reverseOrder [1] BOOLEAN DEFAULT FALSE } Filter ::= CHOICE { and [0] SET OF Filter, or [1] SET OF Filter, not [2] Filter, equalityMatch [3] AttributeValueAssertion, substrings [4] SubstringFilter, greaterOrEqual [5] AttributeValueAssertion, lessOrEqual [6] AttributeValueAssertion, present [7] AttributeType, approxMatch [8] AttributeValueAssertion, extensibleMatch [9] MatchingRuleAssertion } SubstringFilter ::= SEQUENCE { type AttributeDescription, -- at least one must be present substrings SEQUENCE OF CHOICE { initial [0] LDAPString, any [1] LDAPString, final [2] LDAPString } } MatchingRuleAssertion ::= SEQUENCE { matchingRule [1] MatchingRuleId OPTIONAL, type [2] AttributeType 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 } -- implementors should note that the PartialAttributeList may have -- zero elements (if none of the attributes of that entry were -- requested, or could be returned), and that the vals set may also -- have zero elements (if types only was requested, or all the values -- exceeded the attribute size limit or were excluded because of -- access control). SearchResultReference ::= [APPLICATION 19] SEQUENCE OF LDAPURL -- at least one LDAPURL element must be present SearchResultDone ::= [APPLICATION 5] SEQUENCE { COMPONENTS OF LDAPResult, totalCount [8] INTEGER OPTIONAL } Wahl, Howes & Kille [Page 42]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 SearchResultFull ::= SEQUENCE OF CHOICE { entry SearchResultEntry, reference SearchResultReference, resultCode SearchResultDone } ModifyRequest ::= [APPLICATION 6] SEQUENCE { object LDAPDN, modification SEQUENCE OF SEQUENCE { operation ENUMERATED { add (0), delete (1), replace (2) }, modification AttributeTypeAndValues } } AttributeTypeAndValues ::= SEQUENCE { type AttributeDescription, vals SET OF AttributeValue } ModifyResponse ::= [APPLICATION 7] LDAPResult AddRequest ::= [APPLICATION 8] SEQUENCE { entry LDAPDN, attributes AttributeList } AttributeList ::= SEQUENCE OF SEQUENCE { type AttributeDescription, vals SET OF AttributeValue } AddResponse ::= [APPLICATION 9] LDAPResult DelRequest ::= [APPLICATION 10] LDAPDN DelResponse ::= [APPLICATION 11] LDAPResult ModifyDNRequest ::= [APPLICATION 12] SEQUENCE { entry LDAPDN, newrdn RelativeLDAPDN, deleteoldrdn BOOLEAN, newSuperior [0] LDAPDN OPTIONAL } ModifyDNResponse ::= [APPLICATION 13] LDAPResult CompareRequest ::= [APPLICATION 14] SEQUENCE { entry LDAPDN, ava AttributeValueAssertion } CompareResponse ::= [APPLICATION 15] SEQUENCE { COMPONENTS OF LDAPResult, matchedSubtype [9] AttributeDescription OPTIONAL } AbandonRequest ::= [APPLICATION 16] MessageID ExtendedRequest ::= [APPLICATION 23] SEQUENCE { requestName [0] LDAPOID, requestValue [1] OCTET STRING } Wahl, Howes & Kille [Page 43]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 ExtendedResponse ::= [APPLICATION 24] SEQUENCE { COMPONENTS OF LDAPResult, responseName [10] LDAPOID OPTIONAL, response [11] OCTET STRING OPTIONAL } -- not part of LDAP core protocol, see Appendix B -- ProtectedPassword ::= SEQUENCE { time1 [0] UTCTime OPTIONAL, time2 [1] UTCTime OPTIONAL, random1 [2] BIT STRING OPTIONAL, random2 [3] BIT STRING OPTIONAL, algorithmIdentifier [4] LDAPOID, encipheredPassword [5] BIT STRING } StrongCredentials ::= SEQUENCE { certification-path [0] AF.CertificationPath OPTIONAL, bind-token [1] DAS.Token } END Appendix B - X.500 Authentication Mechanisms This Appendix defines two SASL authentication mechanisms which may be used with LDAP. These mechanisms are only for authentication, they have no effect on the protocol encodings and are not designed to provide integrity or confidentiality services. If an implementation supports these elements, then the following additional encoding restrictions apply to these elements: - BIT STRING values are to be encoded in primitive form only. Unused bits in the final octet of the encoding of a BIT STRING value, if there are any, should always be set to zero. - UTC Times must be encoded with the "Z" suffix, not as a local time. The client may include one of these mechanisms and its credential in the BindRequest. The server will return a BindResponse of either: - success, and the serverCreds field absent, implying that the server successfully authenticated the client but is not returning any authentication information about the server, - success, and the serverCreds field present, with the same mechanism as that requested by the client, and the credentials of the server itself, - any of the resultCodes listen in 4.2.3, with the serverCreds field absent, indicating that the server did not successfully authenticate the client or another problem occurred. Wahl, Howes & Kille [Page 44]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 B.1. X.511-Protected The "X.511-Protected" authentication mechanism allows a hash of the password, combined optionally with the current time and random numbers, to be sent to or returned from the server. The protected field contains the hash value. This prevents a password from being carried in the clear. The mechanism field is set to the string "X.511-Protected", and the credentials field contain the DER encoding of a value of the following ASN.1 type: ProtectedPassword ::= SEQUENCE { time1 [0] UTCTime OPTIONAL, time2 [1] UTCTime OPTIONAL, random1 [2] BIT STRING OPTIONAL, random2 [3] BIT STRING OPTIONAL, algorithmIdentifier [4] LDAPOID, encipheredPassword [5] BIT STRING } The use of the time1, time2, random1, random2 and encryptedPassword fields are as defined in ITU-T Rec. X.509 [12] and the functional profile for X.500 for the environment in which this authentication mechanism is to be used. The name field of the BindRequest must be a nonempty string when this mechanism is being used to authenticate the client. Note that this security mechanism is not intended to protect against attackers modifying the bind name field or other protocol elements. B.2. X.511-Strong Strong authentication to the directory can be accomplished using the "X.511-Strong". The mechanism field is set to the string "X.511-Strong", and the credentials field set to a DER-encoding of a value of the following ASN.1 type: StrongCredentials ::= SEQUENCE { certification-path [0] AF.CertificationPath OPTIONAL, bind-token [1] DAS.Token } The ASN.1 type "CertificationPath" is defined in [12], and the ASN.1 type "Token" is defined in [13]. When the credentials are being used to authenticate the client, it is recommended that the certification-path field be present, which will contain minimally the client's certificate. If the certification-path field is supplied, then the name field of the BindRequest must be an empty string, and the server will obtain the name of the client from the subject field of the certification-path userCertificate. Wahl, Howes & Kille [Page 45]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 It is recommended for interoperability that if the server's or client's certificates contain RSA public keys, the PKCS md5WithRSAEncryption (1.2.840.113549.1.1.4) algorithm should be used. Table of Contents 1. Status of this Memo .................................... 1 2. Abstract ............................................... 1 3. Models ................................................. 2 3.1. Protocol Model ........................................ 2 3.2. Data Model ............................................ 3 3.2.1 Attributes of Entries ................................ 3 3.2.2 Subschema Subentry ................................... 4 3.3. Relationship to X.500 ................................. 5 3.4. Server-specific Data Requirements ..................... 5 4. Elements of Protocol ................................... 6 4.1. Common Elements ....................................... 6 4.1.1. Message Envelope .................................... 6 4.1.2. String Types ........................................ 8 4.1.3. Distinguished Name and Relative Distinguished Name .. 8 4.1.4. Attribute Type and Description ...................... 9 4.1.5. Attribute Value ..................................... 10 4.1.6. Attribute Value Assertion ........................... 11 4.1.7. Attribute ........................................... 11 4.1.8. Matching Rule Identifier ............................ 11 4.1.9. Result Message ...................................... 11 4.1.10. Referral ........................................... 13 4.2. Bind Operation ....................................... 14 4.2.1. Sequencing of the Bind Request ...................... 15 4.2.2 Authentication and Other Security Services ........... 15 4.2.3. Bind Response ....................................... 16 4.3. Unbind Operation ..................................... 17 4.4. Session Control Operation ............................ 17 4.5. Search Operation ..................................... 20 4.5.1. Search Request ...................................... 20 4.5.2. Search Result ....................................... 24 4.5.3. Continuation References in the Search Result ........ 26 4.5.3.1. Example ........................................... 27 4.6. Modify Operation ..................................... 28 4.7. Add Operation ........................................ 30 4.8. Delete Operation ..................................... 30 4.9. Modify DN Operation .................................. 31 4.10. Compare Operation ................................... 32 4.11. Abandon Operation ................................... 32 4.12. Extended Operation .................................. 33 5. Protocol Element Encodings and Transfer ................ 33 5.1. Mapping Onto BER-based Transport Services ............ 34 5.1.1. Transmission Control Protocol (TCP) ................ 34 5.1.2. Connection Oriented Transport Service (COTS) ....... 34 5.1.3. User Datagram Protocol (UDP) ....................... 34 5.1.4. Secure Socket Layer over TCP (SSL) ................. 35 6. Implementation Guidelines .............................. 35 6.1. Server Implementations ............................... 35 Wahl, Howes & Kille [Page 46]
INTERNET-DRAFT Lightweight Directory Access Protocol (v3) October 1996 6.2. Client Implementations ............................... 35 6.2.1. CLDAP Retry ......................................... 35 6.2.2. Loop Detection ...................................... 35 7. Security Considerations ................................ 35 8. Acknowledgements ....................................... 36 9. Bibliography ........................................... 36 10. Authors' Address ...................................... 37 Appendix A - Complete ASN.1 Definition ..................... 38 Appendix B - X.500 Authentication Mechanisms ............... 44 B.1. X.511-Protected ....................................... 45 B.2. X.511-Strong .......................................... 45 <draft-ietf-asid-ldapv3-protocol-03.txt> Expires: April 5, 1997 [Page 47]
