rfc2307.txt

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RFC 2307      Using LDAP as a Network Information Service     March 1998


                omitting leading zeros'
          EQUALITY caseIgnoreIA5Match
          SYNTAX 'IA5String{128}' SINGLE-VALUE )

        ( nisSchema.1.21 NAME 'ipNetmaskNumber'
          DESC 'IP netmask as a dotted decimal, eg. 255.255.255.0,
                omitting leading zeros'
          EQUALITY caseIgnoreIA5Match
          SYNTAX 'IA5String{128}' SINGLE-VALUE )

        ( nisSchema.1.22 NAME 'macAddress'
          DESC 'MAC address in maximal, colon separated hex
                notation, eg. 00:00:92:90:ee:e2'
          EQUALITY caseIgnoreIA5Match
          SYNTAX 'IA5String{128}' )

        ( nisSchema.1.23 NAME 'bootParameter'
          DESC 'rpc.bootparamd parameter'
          SYNTAX 'bootParameterSyntax' )

        ( nisSchema.1.24 NAME 'bootFile'
          DESC 'Boot image name'
          EQUALITY caseExactIA5Match
          SYNTAX 'IA5String' )

        ( nisSchema.1.26 NAME 'nisMapName'
          SUP name )

        ( nisSchema.1.27 NAME 'nisMapEntry'
          EQUALITY caseExactIA5Match
          SUBSTRINGS caseExactIA5SubstringsMatch
          SYNTAX 'IA5String{1024}' SINGLE-VALUE )

4. Class definitions

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

   The rfc822MailGroup object class MAY be used to represent a mail
   group for the purpose of alias expansion. Several alternative schemes
   for mail routing and delivery using LDAP directories, which are
   outside the scope of this document.

        ( nisSchema.2.0 NAME 'posixAccount' SUP top AUXILIARY
          DESC 'Abstraction of an account with POSIX attributes'
          MUST ( cn $ uid $ uidNumber $ gidNumber $ homeDirectory )
          MAY ( userPassword $ loginShell $ gecos $ description ) )




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        ( nisSchema.2.1 NAME 'shadowAccount' SUP top AUXILIARY
          DESC 'Additional attributes for shadow passwords'
          MUST uid
          MAY ( userPassword $ shadowLastChange $ shadowMin
                shadowMax $ shadowWarning $ shadowInactive $
                shadowExpire $ shadowFlag $ description ) )

        ( nisSchema.2.2 NAME 'posixGroup' SUP top STRUCTURAL
          DESC 'Abstraction of a group of accounts'
          MUST ( cn $ gidNumber )
          MAY ( userPassword $ memberUid $ description ) )

        ( nisSchema.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 ) )

        ( nisSchema.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 $ description )
          MAY description )

        ( nisSchema.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 $ description )
          MAY description )

        ( nisSchema.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 ( l $ description $ manager ) )

        ( nisSchema.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 ( cn $ ipNetworkNumber )
          MAY ( ipNetmaskNumber $ l $ description $ manager ) )

        ( nisSchema.2.8 NAME 'nisNetgroup' SUP top STRUCTURAL
          DESC 'Abstraction of a netgroup. May refer to other netgroups'
          MUST cn
          MAY ( nisNetgroupTriple $ memberNisNetgroup $ description ) )

        ( nisSchema.2.09 NAME 'nisMap' SUP top STRUCTURAL
          DESC 'A generic abstraction of a NIS map'
          MUST nisMapName
          MAY description )

        ( nisSchema.2.10 NAME 'nisObject' SUP top STRUCTURAL
          DESC 'An entry in a NIS map'
          MUST ( cn $ nisMapEntry $ nisMapName )
          MAY description )

        ( nisSchema.2.11 NAME 'ieee802Device' SUP top AUXILIARY
          DESC 'A device with a MAC address; device SHOULD be
                used as a structural class'
          MAY macAddress )

        ( nisSchema.2.12 NAME 'bootableDevice' SUP top AUXILIARY
          DESC 'A device with boot parameters; device SHOULD be
                used as a structural class'
          MAY ( bootFile $ bootParameter ) )

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 information
   source for the functions listed in 5.2 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 implementations 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.




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5.2. 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))
        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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5.3. 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.

   The account object class provides a convenient structural class for
   posixAccount, and SHOULD be used where additional attributes are not
   required.

   It is suggested that uid and cn are used as the RDN attribute type
   for posixAccount and posixGroup entries, respectively.

   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
   a userPassword attribute MUST NOT be used for authentication. The
   client should be returned a non-matchable password such as "x".

   userPassword values MUST be represented by following syntax:

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

   The encrypted password contains of a plaintext key hashed using the
   algorithm scheme.

   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 sufficient to
   consider only "crypt".

   Below is an example of a userPassword attribute:

                    userPassword: {crypt}X5/DBrWPOQQaI



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   A future standard may specify LDAP v3 attribute descriptions to
   represent hashed userPasswords, as noted below. This schema MUST NOT
   be used with LDAP v2 DUAs and DSAs.

        attributetype           = attributename sep attributeoption
        attributename           = "userPassword"
        sep                     = ";"
        attributeoption         = schemeclass "-" scheme
        schemeclass             = "hash" / altschemeclass
        scheme                  = "crypt" / "md5" / "sha" / altscheme
        altschemeclass          = "x-" keystring
        altscheme               = keystring


   Below is an example of a userPassword attribute, represented with an
   LDAP v3 attribute description:

           userPassword;hash-crypt: X5/DBrWPOQQaI


   A DUA MAY utilise the attributes in the shadowAccount class to
   provide 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 simplify
   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.
   Implementations 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].





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

   Hosts with IPv6 addresses MUST be written in their "preferred" form
   as defined in section 2.2.1 of [RFC1884], such that all components of
   the address are indicated and leading zeros are omitted. This
   provides a consistent means of resolving ipHosts by address.

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, dc=aja, dc=com
           cn: domain
           cn: nameserver
           objectClass: top
           objectClass: ipService
           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.)

   With the exception of userPassword values, which are parsed according
   to the syntax considered in section 5.2, any 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 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 appropriate



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