Application Working Group                                      L. Howard
INTERNET-DRAFT                                             PADL Software
Expires in six months                                          M. Ansari

                                                        20 February 2005
Intended Category: Informational
Obsoletes: RFC 2307

      An Approach for Using LDAP as a Network Information Service

Status of this Memo

     This document is intended to be, after appropriate review and revi-
     sion, submitted to the RFC Editor for publication as an Experimen-
     tal document.  Distribution of this memo is unlimited.  Technical
     discussion of this document will take place on the IETF LDAP Exten-
     sions mailing list <>.  Please send editorial com-
     ments directly to the author <>.

     By submitting this Internet-Draft, I accept the provisions of Sec-
     tion 4 of RFC 3667.  By submitting this Internet-Draft, I certify
     that any applicable patent or other IPR claims of which I am aware
     have been disclosed, or will be disclosed, and any of which I
     become aware will be disclosed, in accordance with RFC 3668.

     Internet-Drafts are working documents of the Internet Engineering
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     other groups may also distribute working documents as Internet-

     Internet-Drafts are draft documents valid for a maximum of six
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     ments at any time. It is inappropriate to use Internet-Drafts as
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     The list of current Internet-Drafts can be accessed at

     The list of Internet-Draft Shadow Directories can be accessed at

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     Copyright (C) The Internet Society (2005).  All Rights Reserved.

     Please see the Full Copyright section near the end of this document
     for more information.


     This document describes a mechanism for mapping entities related to
     TCP/IP and the UNIX system into X.500 [X500] entries so that they
     may be resolved with the Lightweight Directory Access Protocol
     [RFC2251]. A set of attribute types and object classes are pro-
     posed, along with specific guidelines for interpreting them.

     The intention is to assist the deployment of LDAP as an organiza-
     tional nameservice. No proposed solutions are intended as standards
     for the Internet.  Rather, it is hoped that a general consensus
     will emerge as to the appropriate solution to such problems, lead-
     ing eventually to the adoption of standards. The proposed mechanism
     has already been implemented with some success.

1.   Background and Motivation

     The UNIX (R) operating system, and its derivatives (specifically,
     those which support TCP/IP and conform to the X/Open Single UNIX
     specification [XOPEN]) require a means of looking up entities, by
     matching them against search criteria or by enumeration. (Other
     operating systems that support TCP/IP may provide some means of
     resolving some of these entities. This schema is applicable to
     those environments also.)

     These entities include users, groups, IP services (which map names
     to IP ports and protocols, and vice versa), IP protocols (which map
     names to IP protocol numbers and vice versa), RPCs (which map names
     to ONC Remote Procedure Call [RFC1057] numbers and vice versa), NIS
     netgroups, booting information (boot parameters and MAC address
     mappings), filesystem mounts, IP hosts and networks.

     Resolution requests are made through a set of C functions, provided
     in the UNIX system's C library. For example, the UNIX system util-
     ity "ls", which enumerates the contents of a filesystem directory,
     uses the C library function getpwuid() in order to map user IDs to
     login names. Once the request is made, it is resolved using a
     "nameservice" which is supported by the client library. The name-
     service may be, at its simplest, a collection of files in the local
     filesystem which are opened and searched by the C library. Other
     common nameservices include the Network Information Service (NIS)

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     and the Domain Name System (DNS). (The latter is typically used for
     resolving hosts, services and networks.) Both these nameservices
     have the advantage of being distributed and thus permitting a com-
     mon set of entities to be shared amongst many clients.

     LDAP is a distributed, hierarchical directory service access proto-
     col which is used to access repositories of users and other net-
     work-related entities. Because LDAP is often not tightly integrated
     with the host operating system, information such as users may need
     to be kept both in LDAP and in an operating system supported name-
     service such as NIS. By using LDAP as the the primary means of
     resolving these entities, these redundancy issues are minimized and
     the scalability of LDAP can be exploited. (By comparison, NIS ser-
     vices based on flat files do not have the scalability or extensi-
     bility of LDAP or X.500.)

     The object classes and attributes defined below are suitable for
     representing the aforementioned entities in a form compatible with
     LDAP and X.500 directory services.

2.   General Issues

2.1  Terminology

     The key words "MUST", "SHOULD", and "MAY" used in this document are
     to be interpreted as described in [RFC2119].

     For the purposes of this document, the term "nameservice" refers to
     a service, such as NIS or flat files, that is used by the operating
     system to resolve entities within a single, local naming context.
     Contrast this with a "directory service" such as LDAP, which sup-
     ports extensible schema and multiple naming contexts.

     The term "NIS-related entities" broadly refers to entities which
     are typically resolved using the Network Information Service. (NIS
     was previously known as YP.) Deploying LDAP for resolving these
     entities does not imply that NIS be used, as a gateway or other-
     wise. In particular, the host and network classes are generically
     applicable, and may be implemented on any system that wishes to use
     LDAP or X.500 for host and network resolution.

     The "DUA" (directory user agent) refers to the LDAP client querying
     these entities, such as an LDAP to NIS gateway or the C library.
     The "client" refers to the application which ultimately makes use
     of the information returned by the resolution. It is irrelevant
     whether the DUA and the client reside within the same address
     space. The act of the DUA making this information to the client is

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     termed "republishing".

     To avoid confusion, the term "login name" refers to the user's
     login name (being the value of the uid attribute) and the term
     "user ID" refers to he user's integer identification number (being
     the value of the uidNumber attribute).

     The phrases "resolving an entity" and "resolution of entities"
     refer respectively to enumerating NIS-related entities of a given
     type, and matching them against a given search criterion. One or
     more entities are returned as a result of successful "resolutions"
     (a "match" operation will only return one entity).

     The use of the term UNIX does not confer upon this schema the
     endorsement of owners of the UNIX trademark. Where necessary, the
     term "TCP/IP entity" is used to refer to protocols, services,
     hosts, and networks, and the term "UNIX entity" to its complement.
     (The former category does not mandate the host operating system
     supporting the interfaces required for resolving UNIX entities.)

     The OIDs defined below are derived from iso(1) org(3) dod(6) inter-
     net(1) directory(1) nisSchema(1).

2.2  Attributes

     The attributes and classes defined in this document are summarized

     The following attributes are defined in this document:


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     Additionally, some of the attributes defined in [RFC2256] and
     [RFC3112] are required.

2.3  Object classes

     The following object classes are defined in this document:


     Additionally, some of the classes defined in [RFC2256] are

3.   Attribute definitions

     This section contains attribute definitions to be implemented by

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     DUAs supporting this schema.

          ( NAME 'uidNumber'
            DESC 'An integer uniquely identifying a user in an
                  administrative domain'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'gidNumber'
            DESC 'An integer uniquely identifying a group in an
                  administrative domain'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'gecos'
            DESC 'The GECOS field; the common name'
            EQUALITY caseIgnoreMatch
            SUBSTRINGS caseIgnoreSubstringsMatch
            SINGLE-VALUE )

          ( NAME 'homeDirectory'
            DESC 'The absolute path to the home directory'
            EQUALITY caseExactIA5Match
            SINGLE-VALUE )

          ( NAME 'loginShell'
            DESC 'The path to the login shell'
            EQUALITY caseExactIA5Match
            SINGLE-VALUE )

          ( NAME 'shadowLastChange'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'shadowMin'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'shadowMax'
            EQUALITY integerMatch

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            SINGLE-VALUE )

          ( NAME 'shadowWarning'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'shadowInactive'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'shadowExpire'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'shadowFlag'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'memberUid'
            EQUALITY caseExactMatch
            SYNTAX )

          ( NAME 'memberNisNetgroup'
            EQUALITY caseExactMatch
            SYNTAX )

          ( NAME 'nisNetgroupTriple'
            DESC 'Netgroup triple'
            EQUALITY caseIgnoreMatch
            SUBSTRINGS caseIgnoreSubstringsMatch
            SYNTAX )

          ( NAME 'ipServicePort'
            DESC 'Service port number'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'ipServiceProtocol'
            DESC 'Service protocol name'
            EQUALITY caseIgnoreMatch
            SYNTAX )

          ( NAME 'ipProtocolNumber'

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            DESC 'IP protocol number'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'oncRpcNumber'
            DESC 'ONC RPC number'
            EQUALITY integerMatch
            SINGLE-VALUE )

          ( NAME 'ipHostNumber'
            DESC 'IPv4 addresses as a dotted decimal omitting leading
                  zeros or IPv6 addresses as defined in RFC2373'
            EQUALITY caseIgnoreIA5Match
            SYNTAX )

          ( NAME 'ipNetworkNumber'
            DESC 'IP network omitting leading zeros, eg. 192.168'
            EQUALITY caseIgnoreIA5Match
            SINGLE-VALUE )

          ( NAME 'ipNetmaskNumber'
            DESC 'IP netmask omitting leading zeros, eg.'
            EQUALITY caseIgnoreIA5Match
            SINGLE-VALUE )

          ( NAME 'macAddress'
            DESC 'MAC address in maximal, colon separated hex
                  notation, eg. 00:00:92:90:ee:e2'
            EQUALITY caseIgnoreIA5Match
            SYNTAX )

          ( NAME 'bootParameter'
            DESC 'rpc.bootparamd parameter'
            EQUALITY caseExactIA5Match
            SYNTAX )

          ( NAME 'bootFile'
            DESC 'Boot image name'
            EQUALITY caseExactIA5Match
            SYNTAX )

          ( NAME 'nisMapName'
            DESC 'Name of a generic NIS map'
            EQUALITY caseIgnoreMatch

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            SYNTAX{64} )

          ( NAME 'nisMapEntry'
            DESC 'A generic NIS entry'
            EQUALITY caseExactMatch
            SINGLE-VALUE )

          ( NAME 'nisPublicKey'
            DESC 'NIS public key'
            EQUALITY octetStringMatch
            SINGLE-VALUE )

          ( NAME 'nisSecretKey'
            DESC 'NIS secret key'
            EQUALITY octetStringMatch
            SINGLE-VALUE )

          ( NAME 'nisDomain'
            DESC 'NIS domain'
            EQUALITY caseIgnoreIA5Match
            SYNTAX{256} )

          ( NAME 'automountMapName'
            DESC 'automount Map Name'
            EQUALITY caseExactMatch
            SINGLE-VALUE )

          ( NAME 'automountKey'
            DESC 'Automount Key value'
            EQUALITY caseExactMatch
            SINGLE-VALUE )

          ( NAME 'automountInformation'
            DESC 'Automount information'
            EQUALITY caseExactMatch
            SINGLE-VALUE )

4.   Class definitions

     This section contains class definitions to be implemented by DUAs
     supporting the schema.

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     Various schema for mail routing and delivery using LDAP directories
     have been proposed, and as such this document does not consider
     schema for representing mail aliases or distribution lists.

          ( NAME 'posixAccount' SUP top AUXILIARY
            DESC 'Abstraction of an account with POSIX attributes'
            MUST ( cn $ uid $ uidNumber $ gidNumber $ homeDirectory )
            MAY ( authPassword $ userPassword $ loginShell $ gecos $
                  description ) )

          ( NAME 'shadowAccount' SUP top AUXILIARY
            DESC 'Additional attributes for shadow passwords'
            MUST uid
            MAY ( authPassword $ userPassword $ description $
                  shadowLastChange $ shadowMin $ shadowMax $
                  shadowWarning $ shadowInactive $
                  shadowExpire $ shadowFlag ) )

          ( NAME 'posixGroup' SUP top AUXILIARY
            DESC 'Abstraction of a group of accounts'
            MUST gidNumber
            MAY ( authPassword $ userPassword $ memberUid $
                  description ) )

          ( NAME 'ipService' SUP top STRUCTURAL
            DESC 'Abstraction an Internet Protocol service.
                  Maps an IP port and protocol (such as tcp or udp)
                  to one or more names; the distinguished value of
                  the cn attribute denotes the service's canonical
            MUST ( cn $ ipServicePort $ ipServiceProtocol )
            MAY description )

          ( NAME 'ipProtocol' SUP top STRUCTURAL
            DESC 'Abstraction of an IP protocol. Maps a protocol number
                  to one or more names. The distinguished value of the cn
                  attribute denotes the protocol canonical name'
            MUST ( cn $ ipProtocolNumber )
            MAY description )

          ( NAME 'oncRpc' SUP top STRUCTURAL
            DESC 'Abstraction of an Open Network Computing (ONC)
                 [RFC1057] Remote Procedure Call (RPC) binding.
                 This class maps an ONC RPC number to a name.
                 The distinguished value of the cn attribute denotes
                 the RPC service canonical name'
            MUST ( cn $ oncRpcNumber )

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            MAY description )

          ( NAME 'ipHost' SUP top AUXILIARY
            DESC 'Abstraction of a host, an IP device. The distinguished
                  value of the cn attribute denotes the host's canonical
               name. Device SHOULD be used as a structural class'
            MUST ( cn $ ipHostNumber )
            MAY ( authPassword $ userPassword $ l $ description $ manager ) )

          ( NAME 'ipNetwork' SUP top STRUCTURAL
            DESC 'Abstraction of a network. The distinguished value of
                  the cn attribute denotes the network canonical name'
            MUST ipNetworkNumber
            MAY ( cn $ ipNetmaskNumber $ l $ description $ manager ) )

          ( NAME 'nisNetgroup' SUP top STRUCTURAL
            DESC 'Abstraction of a netgroup. May refer to other netgroups'
            MUST cn
            MAY ( nisNetgroupTriple $ memberNisNetgroup $ description ) )

          ( NAME 'nisMap' SUP top STRUCTURAL
            DESC 'A generic abstraction of a NIS map'
            MUST nisMapName
            MAY description )

          ( NAME 'nisObject' SUP top STRUCTURAL
            DESC 'An entry in a NIS map'
            MUST ( cn $ nisMapEntry $ nisMapName )
            MAY description )

          ( NAME 'ieee802Device' SUP top AUXILIARY
            DESC 'A device with a MAC address; device SHOULD be
                  used as a structural class'
            MAY macAddress )

          ( NAME 'bootableDevice' SUP top AUXILIARY
            DESC 'A device with boot parameters; device SHOULD be
                  used as a structural class'
            MAY ( bootFile $ bootParameter ) )

          ( NAME 'nisKeyObject' SUP top AUXILIARY
            DESC 'An object with a public and secret key'
            MUST ( cn $ nisPublicKey $ nisSecretKey )
            MAY ( uidNumber $ description ) )

          ( NAME 'nisDomainObject' SUP top AUXILIARY
            DESC 'Associates a NIS domain with a naming context'
            MUST nisDomain )

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          ( NAME 'automountMap' SUP top STRUCTURAL
            MUST ( automountMapName )
            MAY description )

          ( NAME 'automount' SUP top STRUCTURAL
            DESC 'Automount information'
            MUST ( automountKey $ automountInformation )
            MAY description )

5.   Implementation details

5.1  Suggested resolution methods

     The preferred means of directing a client application (one using
     the shared services of the C library) to use LDAP as its informa-
     tion source for the functions listed in Appendix B is to modify the
     source code to directly query LDAP. As the source to commercial C
     libraries and applications is rarely available to the end-user, one
     could emulate a supported nameservice (such as NIS). (This is also
     an appropriate opportunity to perform caching of entries across
     process address spaces.) In the case of NIS, reference implementa-
     tions are widely available and the RPC interface is well known.

     The means by which the operating system is directed to use LDAP is
     implementation dependent. For example, some operating systems and C
     libraries support end-user extensible resolvers using dynamically
     loadable libraries and a nameservice "switch". The means in which
     the DUA locates LDAP servers is also implementation dependent.

5.2  Interpreting user and group entries

     User and group resolution is initiated by the functions prefixed by
     getpw and getgr respectively. The uid attribute contains the user's
     login name. The cn attribute, in posixGroup entries, contains the
     group's name.  This document preserves the use of the uid attribute
     even though, being a naming attribute, its syntax is case insensi-
     tive. This may cause a problem with existing deployments where
     there exist login names differing only in case. If DUAs support
     attribute mapping, a different attribute may be used to represent
     users' login names.

     The account object class provides a convenient structural class for
     posixAccount, and SHOULD be used where additional attributes are
     not required. For groups with one of more distinguished names, the
     groupOfUniqueNames object class MUST be used as a structural object
     class. For groups whose members are only login names, the namedOb-
     ject [namedObject] object class MAY be used as a structural object

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     It is suggested that uid and cn are used as the naming attribute
     for posixAccount and posixGroup entries, respectively. Group mem-
     bers may either be login names (values of memberUid) or distin-
     guished names (values of uniqueMember). In the latter case, the
     distinguished name must be mapped to one or more login names by
     examining the name's RDN or, if it is not distinguished by uid,
     performing a base search on the DN with a filter of "(object-
     class=*)". DUAs may wish to cache DN to login name mappings. The
     DUA MAY traverse nested groups.

     An account's GECOS field is preferably determined by a value of the
     gecos attribute. If no gecos attribute exists, the value of the cn
     attribute MUST be used. (The existence of the gecos attribute
     allows information embedded in the GECOS field, such as a user's
     telephone number, to be returned to the client without overloading
     the cn attribute. It also accommodates directories where the common
     name does not contain the user's full name.)

     An entry of class posixAccount, posixGroup, or shadowAccount with-
     out an authPassword or userPassword attribute MUST NOT be used for
     authentication.  In this case the client SHOULD be returned a non-
     matchable password such as "x".

     If userPassword is used, its values MUST be represented by follow-
     ing syntax:

          passwordvalue   = schemeprefix encryptedpasswd
          schemeprefix    = "{" scheme "}"
          scheme          = "crypt" / "md5" / "sha" / "ssha" / altscheme
          altscheme       = "x-" keystring
          encryptedpasswd = encrypted password

     The encrypted password contains of a plaintext key hashed using the
     algorithm scheme.  If the schema is "sha", the encrypted password
     is the base64 encoding of the SHA-1 digest of the plaintext pass-

     userPassword values which do not adhere to this syntax MUST NOT be
     used for authentication. The DUA MUST iterate through the values of
     the attribute until a value matching the above syntax is found.
     Only if encryptedpassword is an empty string does the user have no
     password.  DUAs are not required to consider encryption schemes
     which the client will not recognize; in most cases, it may be suf-
     ficient to consider only "crypt".

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     DUA MAY use the authPassword attribute instead of userPassword,
     defined in [RFC3112].  The DUA MUST iterate the values of the auth-
     Password attribute until a value whose scheme is CRYPT is found.
     The DUA MAY iterate through the values of the userPassword
     attribute, using the syntax defined in RFC 2307, until a value
     whose scheme is CRYPT is found. If no conforming value is found,
     the client MUST be returned a non-matchable password such as "x".
     Authentication using schemes other than CRYPT is, although advis-
     able, beyond the scope of this document.

     Below is an example of an authPassword attribute:

          authPassword: CRYPT$X5/DBrWPOQQaI

     Below is an example of a (deprecated) userPassword attribute:

          userPassword: {CRYPT}X5/DBrWPOQQaI

     A DUA MAY utilize the attributes in the shadowAccount class to pro-
     vide shadow password service (getspnam() and getspent()). In such
     cases, the DUA MUST NOT make use of the userPassword attribute for
     getpwnam() et al, and MUST return a non-matchable password (such as
     "x") to the client instead.

5.4  Interpreting hosts and networks

     The ipHostNumber and ipNetworkNumber attributes are defined in
     preference to dNSRecord (defined in [RFC1279]), in order to sim-
     plify the DUA's role in interpreting entries in the directory. A
     dNSRecord expresses a complete resource record, including time to
     live and class data, which is extraneous to this schema.

     Additionally, the ipHost and ipNetwork classes permit a host or
     network (respectively) and all its aliases to be represented by a
     single entry in the directory. This is not necessarily possible if
     a DNS resource record is mapped directly to an LDAP entry.  Imple-
     mentations that wish to use LDAP to master DNS zone information are
     not precluded from doing so, and may simply avoid the ipHost and
     ipNetwork classes.

     This document redefines, although not exclusively, the ipNetwork
     class defined in [RFC1279], in order to achieve consistent naming
     with ipHost. The ipNetworkNumber attribute is also used in the
     siteContact object class [ROSE].

     The authPassword and userPassword attributes are included in ipHost

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     such that hosts may be treated as authentication principals. The
     treatment of these attribute and inherent caveats considered in
     section 5.2 apply here also.

     The trailing zeros in a network address MUST be omitted. CIDR-style
     network addresses (eg. 192.168.1/24) MAY be used.

     Leading zeros MUST be removed from all components of an IPv6
     address string as defined by [RFC2373], section 2.2, item 1.  The
     IPv6 address string MUST be further normalized by following the
     "::" syntax as defined in section 2.2, item 2.  In addition, "::"
     MUST be used to replace the longest string of zero bits.  If there
     are two or more longest strings of zero bits, then the first string
     MUST be replaced.  In addition, the syntax defined by [RFC2373],
     section 2.2, item 3 MUST NOT be used.  IPv4 addresses MUST be rep-
     resented by the IPv4 dotted decimal string syntax.

     For example the following address:


     MUST be normalized as:


5.5  Interpreting other entities

     In general, a one-to-one mapping between entities and LDAP entries
     is proposed, in that each entity has exactly one representation in
     the DIT. In some cases this is not feasible; for example, a service
     which is represented in more than one protocol domain. Consider the
     following entry:

          dn: cn=domain,ou=services,dc=aja,dc=com
          objectClass: top
          objectClass: ipService
          cn: domain
          cn: nameserver
          ipServicePort: 53
          ipServiceProtocol: tcp
          ipServiceProtocol: udp

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     This entry MUST map to the following two (2) services entities:

          domain  53/tcp  nameserver
          domain  53/udp  nameserver

     While the above two entities may be represented as separate LDAP
     entities, with different distinguished names (such as
     cn=domain+ipServiceProtocol=tcp, ... and cn=domain+ipServiceProto-
     col=udp, ...) it is convenient to represent them as a single entry.
     (If a service is represented in multiple protocol domains with dif-
     ferent ports, then multiple entries are required; multivalued RDNs
     may be used to distinguish them.)

     With the exception of authPassword and userPassword values, empty
     values (consisting of a zero length string) are returned by the DUA
     to the client. The DUA MUST reject any entries which do not conform
     to the schema (missing mandatory attributes). Non-conforming
     entries SHOULD be ignored while enumerating entries.

     The nisDomainObject object class is provided to associate a NIS
     domain with a naming context. A DUA would retrieve the NIS domain
     name from a configuration file and enumerate the naming contexts
     served by an LDAP server, searching each naming context for (nisDo-
     main=%s).  The first matching entry that is found may be used as a
     search base for configuration profile information or for entries
     themselves. For example, the following example shows an association
     between the NIS domain "" and the naming context

          dn: dc=aja,dc=com
          objectClass: top
          objectClass: domain
          objectClass: nisDomainObject
          dc: aja

     The nisObject object class MAY be used as a generic means of repre-
     senting NIS entities. Its use is not encouraged; where support for
     entities not described in this schema is desired, an appropriate
     schema should be devised. Implementors are strongly advised to sup-
     port end-user extensible mappings between NIS entities and object
     classes. (Where the nisObject class is used, the nisMapName
     attribute may be used as a RDN.) The nisObject class might be used
     to represent automount information.

5.6  Canonicalizing entries with multi-valued naming attributes

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     For entities such as hosts, services, networks, protocols, and
     RPCs, where there may be one or more aliases, the respective
     entry's relative distinguished name SHOULD be used to determine the
     canonical name.  Any other values for the same attribute are used
     as aliases. For example, the service described in section 5.5 has
     the canonical name "domain" and exactly one alias, "nameserver".

     The schema in this document generally only defines one attribute
     per class which is suitable for distinguishing an entity (excluding
     any attributes with integer syntax; it is assumed that entries will
     be distinguished on name). Usually, this is the common name (cn)
     attribute.  This aids the DUA in determining the canonical name of
     an entity, as it can examine the value of the relative distin-
     guished name. Aliases are thus any values of the distinguishing
     attribute (such as cn) which do not match the canonical name of the

     In the event that a different attribute is used to distinguish the
     entry, as may be the case where these object classes are used as
     auxiliary classes, the entry's canonical name may not be present in
     the RDN. In this case, the DUA MUST choose one of the non-distin-
     guished values to represent the entity's canonical name. As the
     directory server guarantees no ordering of attribute values, it may
     not be possible to distinguish an entry deterministically. This
     ambiguity SHOULD NOT be resolved by mapping one directory entry
     into multiple entities.

6.   Implementation focus

     Gateways between NIS and LDAP have been developed by PADL Software
     and Sun Microsystems. They both support this schema.

     An open source implementation of the C library resolution code has
     been written and is available from PADL Software. It supports C
     libraries on GNU, BSD, AIX, and Solaris operating systems. PADL
     have also made available a set of scripts for migrating flat files
     into a form suitable for loading into an LDAP server.

7.   Security considerations

     The entirety of related security considerations are outside the
     scope of this document.  It is noted that making passwords
     encrypted with a widely understood hash function (such as crypt())
     available to non-privileged users is dangerous because it exposes
     them to dictionary and brute-force attacks.  This is proposed only
     for compatibility with existing UNIX system implementations. Sites

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     where security is critical SHOULD consider using a strong authenti-
     cation service for user authentication.

     Alternatively, the encrypted password could be made available only
     to a subset of privileged DUAs, which would provide "shadow" pass-
     word service to client applications. This may be difficult to

     Because the schema represents operating system-level entities,
     access to these entities SHOULD be granted on a discretionary
     basis. (There is little point in restricting access to data which
     will be republished without restriction, however.) It is particu-
     larly important that only administrators can modify entries defined
     in this schema, with the exception of allowing a principal to
     change their password (which may be done on behalf of the user by a
     client bound as a superior principal, such that password restric-
     tions may be enforced). For example, if a user were allowed to
     change the value of their uidNumber attribute, they could subvert
     security by equivalencing their account with the superuser account.

     A subtree of the DIT which is to be republished by a DUA (such as a
     NIS gateway) SHOULD be within the same administrative domain that
     the republishing DUA represents. (For example, principals outside
     an organization, while conceivably part of the DIT, should not be
     considered with the same degree of authority as those within the

     Finally, care should be exercised with integer attributes of a sen-
     sitive nature (particularly the uidNumber and gidNumber attributes)
     which contain zero-length values. DUAs MAY treat such values as
     corresponding to the "nobody" or "nogroup" user and group, respec-

8.   Acknowledgements

     Thanks to Bob Joslin of the Hewlett Packard Company, and to all
     those that helped with this document's predecessor, RFC 2307.

     UNIX is a registered trademark of The Open Group.

9.   References

          Sun Microsystems, Inc., "RPC: Remote Procedure Call: Protocol
          Specification Version 2", RFC 1057, June 1988.

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          S. Kille, "X.500 and Domains", RFC 1279, November 1991.

          R. Hinden, S. Deering, "IP Version 6 Addressing Architecture",
          RFC 2373, July 1998.

          S. Bradner, "Key Words for use in RFCs to Indicate Requirement
          Levels", RFC 2119, March 1997.

          M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
          Protocol (v3)", RFC 2251, December 1997.

          M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Direc-
          tory Access Protocol (v3): Attribute Syntax Definitions", RFC
          2252, December 1997.

          T. Howes, "The String Representation of LDAP Search Filters",
          RFC 2254, December 1997.

          M. Wahl, "A Summary of the X.500(96) User Schema for use with
          LDAPv3", RFC 2256, December 1997.

          K. Zeilenga, "LDAP Authentication Password Schema", RFC 3112,
          May 2001.

          M. T. Rose, "The Little Black Book: Mail Bonding with OSI
          Directory Services", ISBN 0-13-683210-5, Prentice-Hall, Inc.,

          "Information Processing Systems - Open Systems Interconnection
          - The Directory: Overview of Concepts, Models and Service",
          ISO/IEC JTC 1/SC21, International Standard 9594-1, 1988.

          ISO/IEC 9945-1:1990, Information Technology - Portable Operat-
          ing Systems Interface (POSIX) - Part 1: Systems Application
          Programming Interface (API) [C Language]


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          L. Howard, "A Structural Object Class for Arbitrary Auxiliary
          Object Classes", INTERNET-DRAFT <draft-howard-namedOb-
          ject-02.txt>, July 2002.

10.  Authors' Address

     Luke Howard
     PADL Software Pty. Ltd.
     PO Box 59
     Central Park, Vic 3145

     Morteza Ansari
     Infoblox Inc.
     475 Potrero Avenue
     Sunnyvale, CA 94085
     Phone: +1 408 716 4344

A.   Example entries

     The examples described in this section are provided to illustrate
     the schema described in this draft. They are not meant to be

     The following entry is an example of the posixAccount class:

          dn: uid=lester,ou=people,dc=aja,dc=com
          objectClass: top
          objectClass: account
          objectClass: posixAccount
          uid: lester
          cn: Lester the Nightfly
          gecos: Lester
          uidNumber: 10
          gidNumber: 10
          loginShell: /bin/csh
          userPassword: {crypt}$X5/DBrWPOQQaI
          homeDirectory: /home/lester

     This corresponds the UNIX system password file entry:


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     The following entry is an example of the ipHost class:

          objectClass: top
          objectClass: device
          objectClass: ipHost
          objectClass: bootableDevice
          objectClass: ieee802Device
          macAddress: 00:00:92:90:ee:e2
          bootFile: mach

     This entry represents the host canonically, also
     known as The Ethernet address and four boot parameters
     are also specified.

     An example of the nisNetgroup class:

          dn: cn=nightfly,ou=netgroup,dc=aja,dc=com
          objectClass: top
          objectClass: nisNetgroup
          cn: nightfly
          nisNetgroupTriple: (charlemagne,peg,
          nisNetgroupTriple: (lester,-,)
          memberNisNetgroup: kamakiriad

     This entry represents the netgroup nightfly, which contains two
     triples (the user charlemagne, the host peg, and the domain; and, the user lester, no host, and any domain) and
     one netgroup (kamakiriad).

     Finally, an example of the nisObject class:

          dn: nisMapName=tracks,dc=dunes,dc=aja,dc=com
          objectClass: top
          objectClass: nisMap
          nisMapName: tracks

          dn: cn=Maxine,nisMapName=tracks,dc=dunes,dc=aja,dc=com
          objectClass: top
          objectClass: nisObject
          cn: Maxine
          nisMapName: tracks

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          nisMapEntry: Nightfly$4

     This entry represents the NIS map tracks, and a single map entry.

B.   Affected library functions

     The following functions are typically found in the C libraries of
     most UNIX and POSIX compliant systems. An LDAP search filter
     [RFC2254] which may be used to satisfy the function call is
     included alongside each function name. Parameters are denoted by %s
     and %d for string and integer arguments, respectively. Long lines
     are broken.

          getpwnam()         (&(objectClass=posixAccount)(uid=%s))
          getpwuid()         (&(objectClass=posixAccount)(uidNumber=%d))
          getpwent()         (objectClass=posixAccount)
          getspnam()         (&(objectClass=shadowAccount)(uid=%s))
          getspent()         (objectClass=shadowAccount)

          getgrnam()         (&(objectClass=posixGroup)(cn=%s))
          getgrgid()         (&(objectClass=posixGroup)(gidNumber=%d))
          getgrent()         (objectClass=posixGroup)

          getservbyname()    (&(objectClass=ipService)(cn=%s)
          getservbyport()    (&(objectClass=ipService)(ipServicePort=%d)
          getservent()       (objectClass=ipService)

          getrpcbyname()     (&(objectClass=oncRpc)(cn=%s))
          getrpcbynumber()   (&(objectClass=oncRpc)(oncRpcNumber=%d))
          getrpcent()        (objectClass=oncRpc)

          getprotobyname()   (&(objectClass=ipProtocol)(cn=%s))
          getprotobynumber() (&(objectClass=ipProtocol)(ipProtocolNumber=%d))
          getprotoent()      (objectClass=ipProtocol)

          gethostbyname()    (&(objectClass=ipHost)(cn=%s))
          gethostbyaddr()    (&(objectClass=ipHost)(ipHostNumber=%s))
          gethostent()       (objectClass=ipHost)

          getnetbyname()     (&(objectClass=ipNetwork)(cn=%s))
          getnetbyaddr()     (&(objectClass=ipNetwork)(ipNetworkNumber=%s))
          getnetent()        (objectClass=ipNetwork)

          setnetgrent()      (&(objectClass=nisNetgroup)(cn=%s))

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          getpublickey()     (&(objectClass=nisKeyObject)(...))

C.   Suggested DIT structure

     The cn attribute is typically used to name entities. The ipHostNum-
     ber, ipNetworkNumber, and ipServiceProtocol attributes are also
     naming attributes, such that multi-valued RDNs may be used to dis-
     tinguish between, for example, different interfaces of a multi-
     homed host.

     The following DIT structure MAY be used for deploying this schema.
     It is not required that DC-naming be used, but it is encouraged.

     Naming context                        ObjectClass
     ou=people,dc=...                      posixAccount
     ou=group,dc=...                       posixGroup
     ou=services,dc=...                    ipService
     ou=protocols,dc=...                   ipProtocol
     ou=rpc,dc=...                         oncRpc
     ou=hosts,dc=...                       ipHost
     ou=ethers,dc=...                      ieee802Device
     ou=networks,dc=...                    ipNetwork
     ou=netgroup,dc=...                    nisNetgroup
     nisMapName=...,dc=...                 nisObject
     automountMapName=...,dc=...           automountMap

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     Copies of IPR disclosures made to the IETF Secretariat and any
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     fication can be obtained from the IETF on-line IPR repository at

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     The IETF invites any interested party to bring to its attention any
     copyrights, patents or patent applications, or other proprietary
     rights that may cover technology that may be required to implement
     this standard.  Please address the information to the IETF at ietf-

Full Copyright Statement

     Copyright (C) The Internet Society (2005).  This document is sub-
     ject to the rights, licenses and restrictions contained in BCP 78,
     and except as set forth therein, the authors retain all their

     This document and the information contained herein are provided on

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