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Versions: 00 01 02                                                      
Application Working Group                                      L. Howard
INTERNET-DRAFT                                             PADL Software
Expires April 2003                                             M. Ansari
                                                        Sun Microsystems

                                                         27 October 2002
Intended Category: Informational
Obsoletes: RFC 2307





      An Approach for Using LDAP as a Network Information Service
                    <draft-howard-rfc2307bis-00.txt>


Status of this Memo

     This document is an Internet-Draft and is subject to all provisions
     of Section 10 of RFC2026.

     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 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 docu-
     ments at any time.  It is inappropriate to use Internet- Drafts as
     reference material or to cite them other than as "work in pro-
     gress."

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

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


Abstract

     This document describes a mechanism for mapping entities related to



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     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
     nameservice 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) 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 per-
     mitting a common 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
     network-related entities. Because LDAP is often not tightly
     integrated with the host operating system, information such as



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     users may need to be kept both in LDAP and in an operating system
     supported nameservice 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 com-
     parison, NIS services based on flat files do not have the scalabil-
     ity or extensibility 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
     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



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     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
     below.

     The following attributes are defined in this document:

             uidNumber
             gidNumber
             gecos
             homeDirectory
             loginShell
             shadowLastChange
             shadowMin
             shadowMax
             shadowWarning
             shadowInactive
             shadowExpire
             shadowFlag
             memberUid
             memberNisNetgroup
             nisNetgroupTriple
             ipServicePort
             ipServiceProtocol
             ipProtocolNumber
             oncRpcNumber
             ipHostNumber
             ipNetworkNumber
             ipNetmaskNumber
             macAddress
             bootParameter
             bootFile
             nisMapName
             nisMapEntry



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             nisPublicKey
             nisSecretKey
             nisDomain
             automountMapName
             automountKey
             automountInformation

     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:

             posixAccount
             shadowAccount
             posixGroup
             ipService
             ipProtocol
             oncRpc
             ipHost
             ipNetwork
             nisNetgroup
             nisMap
             nisObject
             ieee802Device
             bootableDevice
             nisKeyObject
             nisDomainObject
             automountMap
             automount

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


3.   Attribute definitions

     This section contains attribute definitions to be implemented by
     DUAs supporting this schema.

             ( 1.3.6.1.1.1.1.0 NAME 'uidNumber'
               DESC 'An integer uniquely identifying a user in an
                     administrative domain'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )




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             ( 1.3.6.1.1.1.1.1 NAME 'gidNumber'
               DESC 'An integer uniquely identifying a group in an
                     administrative domain'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.2 NAME 'gecos'
               DESC 'The GECOS field; the common name'
               EQUALITY caseIgnoreIA5Match
               SUBSTRINGS caseIgnoreIA5SubstringsMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.3 NAME 'homeDirectory'
               DESC 'The absolute path to the home directory'
               EQUALITY caseExactIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.4 NAME 'loginShell'
               DESC 'The path to the login shell'
               EQUALITY caseExactIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.5 NAME 'shadowLastChange'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.6 NAME 'shadowMin'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.7 NAME 'shadowMax'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.8 NAME 'shadowWarning'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.9 NAME 'shadowInactive'
               EQUALITY integerMatch



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               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.10 NAME 'shadowExpire'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.11 NAME 'shadowFlag'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.12 NAME 'memberUid'
               EQUALITY caseExactIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

             ( 1.3.6.1.1.1.1.13 NAME 'memberNisNetgroup'
               EQUALITY caseExactIA5Match
               SUBSTRINGS caseExactIA5SubstringsMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

             ( 1.3.6.1.1.1.1.14 NAME 'nisNetgroupTriple'
               DESC 'Netgroup triple'
               EQUALITY caseIgnoreIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

             ( 1.3.6.1.1.1.1.15 NAME 'ipServicePort'
               DESC 'Service port number'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.16 NAME 'ipServiceProtocol'
               DESC 'Service protocol name'
               SUP name )

             ( 1.3.6.1.1.1.1.17 NAME 'ipProtocolNumber'
               DESC 'IP protocol number'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.18 NAME 'oncRpcNumber'
               DESC 'ONC RPC number'
               EQUALITY integerMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
               SINGLE-VALUE )



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             ( 1.3.6.1.1.1.1.19 NAME 'ipHostNumber'
               DESC 'IPv4 addresses as a dotted decimal omitting leading
                     zeros or IPv6 addresses as defined in RFC2373'
               SUP name )

             ( 1.3.6.1.1.1.1.20 NAME 'ipNetworkNumber'
               DESC 'IP network as a dotted decimal, eg. 192.168,
                     omitting leading zeros'
               SUP name
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.21 NAME 'ipNetmaskNumber'
               DESC 'IP netmask as a dotted decimal, eg. 255.255.255.0,
                     omitting leading zeros'
               EQUALITY caseIgnoreIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.22 NAME 'macAddress'
               DESC 'MAC address in maximal, colon separated hex
                     notation, eg. 00:00:92:90:ee:e2'
               EQUALITY caseIgnoreIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

             ( 1.3.6.1.1.1.1.23 NAME 'bootParameter'
               DESC 'rpc.bootparamd parameter'
               EQUALITY caseExactIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

             ( 1.3.6.1.1.1.1.24 NAME 'bootFile'
               DESC 'Boot image name'
               EQUALITY caseExactIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )

             ( 1.3.6.1.1.1.1.26 NAME 'nisMapName'
               DESC 'Name of a A generic NIS map'
               SUP name )

             ( 1.3.6.1.1.1.1.27 NAME 'nisMapEntry'
               DESC 'A generic NIS entry'
               EQUALITY caseExactIA5Match
               SUBSTRINGS caseExactIA5SubstringsMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
               SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.28 NAME 'nisPublicKey'
               DESC 'NIS public key'
               EQUALITY octetStringMatch



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               SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.29 NAME 'nisSecretKey'
               DESC 'NIS secret key'
               EQUALITY octetStringMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.40 SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.30 NAME 'nisDomain'
               DESC 'NIS domain'
               EQUALITY caseIgnoreIA5Match
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26)

             ( 1.3.6.1.1.1.1.31 NAME 'automountMapName'
               DESC 'automount Map Name'
               EQUALITY caseExactIA5Match
               SUBSTR caseExactIA5SubstringsMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.32 NAME 'automountKey'
               DESC 'Automount Key value'
               EQUALITY caseExactIA5Match
               SUBSTR caseExactIA5SubstringsMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )

             ( 1.3.6.1.1.1.1.33 NAME 'automountInformation'
               DESC 'Automount information'
               EQUALITY caseExactIA5Match
               SUBSTR caseExactIA5SubstringsMatch
               SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )


4.   Class definitions

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

     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.


             ( 1.3.6.1.1.1.2.0 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 ) )

             ( 1.3.6.1.1.1.2.1 NAME 'shadowAccount' SUP top AUXILIARY



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

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

             ( 1.3.6.1.1.1.2.3 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
                     name'
               MUST ( cn $ ipServicePort $ ipServiceProtocol )
               MAY description )

             ( 1.3.6.1.1.1.2.4 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's canonical name'
               MUST ( cn $ ipProtocolNumber )
               MAY description )

             ( 1.3.6.1.1.1.2.5 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's canonical name'
               MUST ( cn $ oncRpcNumber )
               MAY description )

             ( 1.3.6.1.1.1.2.6 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 ) )

             ( 1.3.6.1.1.1.2.7 NAME 'ipNetwork' SUP top STRUCTURAL
               DESC 'Abstraction of a network. The distinguished value of
                     the cn attribute denotes the network's canonical name'



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               MUST ipNetworkNumber
               MAY ( cn $ ipNetmaskNumber $ l $ description $ manager ) )

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

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

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

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

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

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

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

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

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


5.   Implementation details



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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 (non-naming) 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
     class.

     It is suggested that uid and cn are used as the naming attribute
     for posixAccount and posixGroup entries, respectively. Group
     members may either be login names (values of memberUid) or dis-
     tinguished 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
     "(objectclass=*)". DUAs may wish to cache DN to login name map-
     pings. The DUA MAY traverse nested groups.




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     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
     without 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-
     word.

     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".

     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 attri-
     bute, 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:




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             authPassword: CRYPT$X5/DBrWPOQQaI


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

             userPassword: {CRYPT}X5/DBrWPOQQaI


     A DUA MAY utilise 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
     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



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     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
     represented by the IPv4 dotted decimal string syntax.

     For example the following address:

             1080:0000:0:0:08:800:200C:417A
             FF01:0:0:0:0:0:0:0101
             0:0:0:0:0:0:0:0001
             0:0:0:0:0:0:0:0

     MUST be normalized as:

             1080::8:800:200C:417A
             FF01::101
             0::1
             ::

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

     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+ipServiceProtocol=udp, ...) it is convenient to represent
     them as a single entry. (If a service is represented in multiple
     protocol domains with different ports, then multiple entries are
     required; multivalued RDNs may be used to distinguish them.)



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     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
     (nisDomain=%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 "nis.aja.com" and the naming
     context "dc=aja,dc=com":

             dn: dc=aja,dc=com
             objectClass: top
             objectClass: domain
             objectClass: nisDomainObject
             dc: aja
             nisDomain: nis.aja.com


     The nisObject object class MAY be used as a generic means of
     representing NIS entities. Its use is not encouraged; where support
     for entities not described in this schema is desired, an appropri-
     ate schema should be devised. Implementors are strongly advised to
     support 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

     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



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     distinguished name. Aliases are thus any values of the distinguish-
     ing attribute (such as cn) which do not match the canonical name of
     the entity.

     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-
     distinguished 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 com-
     patibility with existing UNIX system implementations. Sites where
     security is critical SHOULD consider using a strong authentication
     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
     enforce.

     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



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     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
     organization.)

     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-
     tively.


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

     [RFC1057]
          Sun Microsystems, Inc., "RPC: Remote Procedure Call: Protocol
          Specification Version 2", RFC 1057, June 1988.

     [RFC1279]
          S. Kille, "X.500 and Domains", RFC 1279, November 1991.

     [RFC2373]
          R. Hinden, S. Deering, "IP Version 6 Addressing Architecture",
          RFC 2373, July 1998.

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

     [RFC2251]
          M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access



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          Protocol (v3)", RFC 2251, December 1997.

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

     [RFC2254]
          T. Howes, "The String Representation of LDAP Search Filters",
          RFC 2254, December 1997.

     [RFC2256]
          M. Wahl, "A Summary of the X.500(96) User Schema for use with
          LDAPv3", RFC 2256, December 1997.

     [RFC3112]
          K. Zeilenga, "LDAP Authentication Password Schema", RFC 3112,
          May 2001.

     [ROSE]
          M. T. Rose, "The Little Black Book: Mail Bonding with OSI
          Directory Services", ISBN 0-13-683210-5, Prentice-Hall, Inc.,
          1992.

     [X500]
          "Information Processing Systems - Open Systems Interconnection
          - The Directory: Overview of Concepts, Models and Service",
          ISO/IEC JTC 1/SC21, International Standard 9594-1, 1988.

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

     [namedObject]
          L. Howard, "A Structural Object Class for Arbitrary Auxiliary
          Object Classes", INTERNET-DRAFT <draft-howard-namedObject-
          01.txt>, July 2002.


10.  Authors' Address


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



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        EMail: lukeh@padl.com

        Morteza Ansari
        Sun Microsystems, Inc.
        17 Network Circle, UMPK17-203
        Menlo Park, CA 94205
        USA
        Phone: +1 650 786-6178
        EMail: morteza.ansari@sun.com



11.  Full Copyright Statement

     Copyright (C) The Internet Society (2002).  All Rights Reserved.

     This document and translations of it may be copied and furnished to
     others, and derivative works that comment on or otherwise explain
     it or assist in its implementation may be prepared, copied, pub-
     lished and distributed, in whole or in part, without restriction of
     any kind, provided that the above copyright notice and this para-
     graph are included on all such copies and derivative works.  How-
     ever, this document itself may not be modified in any way, such as
     by removing the copyright notice or references to the Internet
     Society or other Internet organizations, except as needed for the
     purpose of developing Internet standards in which case the pro-
     cedures for copyrights defined in the Internet Standards process
     must be followed, or as required to translate it into languages
     other than English.

     The limited permissions granted above are perpetual and will not be
     revoked by the Internet Society or its successors or assigns.

     This document and the information contained herein is provided on
     an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
     ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
     IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
     THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
     WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


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
     exhaustive.

     The following entry is an example of the posixAccount class:



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             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:

             lester:X5/DBrWPOQQaI:10:10:Lester:/home/lester:/bin/sh

     The following entry is an example of the ipHost class:

             dn: cn=josie.aja.com,ou=hosts,dc=aja,dc=com
             objectClass: top
             objectClass: device
             objectClass: ipHost
             objectClass: bootableDevice
             objectClass: ieee802Device
             cn: josie.aja.com
             cn: www.aja.com
             ipHostNumber: 10.0.0.1
             macAddress: 00:00:92:90:ee:e2
             bootFile: mach
             bootParameter: root=dan.aja.com:/nfsroot/peg
             bootParameter: swap=dan.aja.com:/nfsswap/peg
             bootParameter: dump=dan.aja.com:/nfsdump/peg

     This entry represents the host canonically josie.aja.com, also
     known as www.aja.com. 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,dunes.aja.com)
             nisNetgroupTriple: (lester,-,)
             memberNisNetgroup: kamakiriad



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     This entry represents the netgroup nightfly, which contains two
     triples (the user charlemagne, the host peg, and the domain
     dunes.aja.com; 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
             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)
                                 (ipServiceProtocol=%s))
             getservbyport()    (&(objectClass=ipService)(ipServicePort=%d)
                                  (ipServiceProtocol=%s))
             getservent()       (objectClass=ipService)

             getrpcbyname()     (&(objectClass=oncRpc)(cn=%s))



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             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))

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



C.   Suggested DIT structure

     The cn attribute is typically used to name entities. The ipHost-
     Number, 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
                                              shadowAcount
        ou=group,dc=...                       posixGroup
        ou=services,dc=...                    ipService
        ou=protocols,dc=...                   ipProtocol
        ou=rpc,dc=...                         oncRpc
        ou=hosts,dc=...                       ipHost
        ou=ethers,dc=...                      ieee802Device
                                              bootableDevice
        ou=networks,dc=...                    ipNetwork
        ou=netgroup,dc=...                    nisNetgroup
        nisMapName=...,dc=...                 nisObject
        automountMapName=...,dc=...           automountMap




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