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Network Working Group                                          L. HowardRequest for Comments: 2307                        Independent ConsultantCategory: Experimental                                        March 1998An Approach for Using LDAP as a Network Information ServiceStatus of this Memo   This memo defines an Experimental Protocol for the Internet   community.  It does not specify an Internet standard of any kind.   Discussion and suggestions for improvement are requested.   Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (1998).  All Rights Reserved.Abstract   This document describes an experimental 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 proposed, along with specific guidelines for interpreting   them.   The intention is to assist the deployment of LDAP as an   organizational 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, leading 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), NISHoward                        Experimental                      [Page 1]

RFC 2307      Using LDAP as a Network Information Service     March 1998   netgroups, booting information (boot parameters and MAC address   mappings), filesystem mounts, IP hosts and networks, andRFC822 mail   aliases.   Resolution requests are made through a set of C functions, provided   in the UNIX system's C library. For example, the UNIX system utility   "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 permitting a common set of entities to be   shared amongst many clients.   LDAP is a distributed, hierarchical directory service access protocol   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 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 comparison, NIS services   based on flat files do not have the scalability 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 Issues2.1. 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 supports   extensible schema and multiple naming contexts.Howard                        Experimental                      [Page 2]

RFC 2307      Using LDAP as a Network Information Service     March 1998   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 otherwise. 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 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)   internet(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           homeDirectoryHoward                        Experimental                      [Page 3]

RFC 2307      Using LDAP as a Network Information Service     March 1998           loginShell           shadowLastChange           shadowMin           shadowMax           shadowWarning           shadowInactive           shadowExpire           shadowFlag           memberUid           memberNisNetgroup           nisNetgroupTriple           ipServicePort           ipServiceProtocol           ipProtocolNumber           oncRpcNumber           ipHostNumber           ipNetworkNumber           ipNetmaskNumber           macAddress           bootParameter           bootFile           nisMapName           nisMapEntry   Additionally, some of the attributes defined in [RFC2256] 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   Additionally, some of the classes defined in [RFC2256] are required.Howard                        Experimental                      [Page 4]

RFC 2307      Using LDAP as a Network Information Service     March 19982.4. Syntax definitions   The following syntax definitions [RFC2252] are used by this schema.   The nisNetgroupTripleSyntax represents NIS netgroup triples:           ( nisSchema.0.0 NAME 'nisNetgroupTripleSyntax'             DESC 'NIS netgroup triple' )   Values in this syntax are represented by the following:        nisnetgrouptriple = "(" hostname "," username "," domainname ")"        hostname          = "" / "-" / keystring        username          = "" / "-" / keystring        domainname        = "" / "-" / keystring   X.500 servers may use the following representation of the above   syntax:        nisNetgroupTripleSyntax ::= SEQUENCE {         hostname  [0] IA5String OPTIONAL,         username  [1] IA5String OPTIONAL,         domainname  [2] IA5String OPTIONAL        }   The bootParameterSyntax syntax represents boot parameters:           ( nisSchema.0.1 NAME 'bootParameterSyntax'             DESC 'Boot parameter' )   where:        bootparameter     = key "=" server ":" path        key               = keystring        server            = keystring        path              = keystring   X.500 servers may use the following representation of the above   syntax:        bootParameterSyntax ::= SEQUENCE {         key     IA5String,         server  IA5String,         path    IA5String        }   Values adhering to these syntaxes are encoded as strings by LDAP   servers.Howard                        Experimental                      [Page 5]

RFC 2307      Using LDAP as a Network Information Service     March 19983. Attribute definitions   This section contains attribute definitions to be implemented by DUAs   supporting this schema.        ( nisSchema.1.0 NAME 'uidNumber'          DESC 'An integer uniquely identifying a user in an                administrative domain'          EQUALITY integerMatch SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.1 NAME 'gidNumber'          DESC 'An integer uniquely identifying a group in an                administrative domain'          EQUALITY integerMatch SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.2 NAME 'gecos'          DESC 'The GECOS field; the common name'          EQUALITY caseIgnoreIA5Match          SUBSTRINGS caseIgnoreIA5SubstringsMatch          SYNTAX 'IA5String' SINGLE-VALUE )        ( nisSchema.1.3 NAME 'homeDirectory'          DESC 'The absolute path to the home directory'          EQUALITY caseExactIA5Match          SYNTAX 'IA5String' SINGLE-VALUE )        ( nisSchema.1.4 NAME 'loginShell'          DESC 'The path to the login shell'          EQUALITY caseExactIA5Match          SYNTAX 'IA5String' SINGLE-VALUE )        ( nisSchema.1.5 NAME 'shadowLastChange'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.6 NAME 'shadowMin'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.7 NAME 'shadowMax'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.8 NAME 'shadowWarning'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.9 NAME 'shadowInactive'Howard                        Experimental                      [Page 6]

RFC 2307      Using LDAP as a Network Information Service     March 1998          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.10 NAME 'shadowExpire'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.11 NAME 'shadowFlag'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.12 NAME 'memberUid'          EQUALITY caseExactIA5Match          SUBSTRINGS caseExactIA5SubstringsMatch          SYNTAX 'IA5String' )        ( nisSchema.1.13 NAME 'memberNisNetgroup'          EQUALITY caseExactIA5Match          SUBSTRINGS caseExactIA5SubstringsMatch          SYNTAX 'IA5String' )        ( nisSchema.1.14 NAME 'nisNetgroupTriple'          DESC 'Netgroup triple'          SYNTAX 'nisNetgroupTripleSyntax' )        ( nisSchema.1.15 NAME 'ipServicePort'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.16 NAME 'ipServiceProtocol'          SUP name )        ( nisSchema.1.17 NAME 'ipProtocolNumber'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.18 NAME 'oncRpcNumber'          EQUALITY integerMatch          SYNTAX 'INTEGER' SINGLE-VALUE )        ( nisSchema.1.19 NAME 'ipHostNumber'          DESC 'IP address as a dotted decimal, eg. 192.168.1.1,                omitting leading zeros'          EQUALITY caseIgnoreIA5Match          SYNTAX 'IA5String{128}' )        ( nisSchema.1.20 NAME 'ipNetworkNumber'          DESC 'IP network as a dotted decimal, eg. 192.168,Howard                        Experimental                      [Page 7]

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 ) )Howard                        Experimental                      [Page 8]

RFC 2307      Using LDAP as a Network Information Service     March 1998        ( 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'Howard                        Experimental                      [Page 9]

RFC 2307      Using LDAP as a Network Information Service     March 1998          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 details5.1. 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.Howard                        Experimental                     [Page 10]

RFC 2307      Using LDAP as a Network Information Service     March 19985.2. 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))Howard                        Experimental                     [Page 11]

RFC 2307      Using LDAP as a Network Information Service     March 19985.3. 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/DBrWPOQQaIHoward                        Experimental                     [Page 12]

RFC 2307      Using LDAP as a Network Information Service     March 1998   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].Howard                        Experimental                     [Page 13]

RFC 2307      Using LDAP as a Network Information Service     March 1998   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 insection 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 insection 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 appropriateHoward                        Experimental                     [Page 14]

RFC 2307      Using LDAP as a Network Information Service     March 1998   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.)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 insection 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 distinguished   name. Aliases are thus any values of the distinguishing 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   A NIS server which uses LDAP instead of local files has been   developed which supports the schema defined in this document.   A reference implementation of the C library resolution code has been   written for the Free Software Foundation. It may support other C   libraries which support the Name Service Switch (NSS) or the   Information Retrieval Service (IRS).   The author has made available a freely distributable set of scripts   which parses local databases such as /etc/passwd and /etc/hosts into   a form suitable for loading into an LDAP server.Howard                        Experimental                     [Page 15]

RFC 2307      Using LDAP as a Network Information Service     March 19987. 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 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" password   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 particularly   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 restrictions 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   sensitive 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,   respectively.8. Acknowledgements   Thanks to Leif Hedstrom of Netscape Communications Corporation,   Michael Grant and Rosanna Lee of Sun Microsystems Inc., Ed Reed of   Novell Inc., and Mark Wahl of Critical Angle Inc. for their valuable   contributions to the development of this schema. Thanks to Andrew   Josey of The Open Group for clarifying the use of the UNIX trademark,   and to Tim Howes and Peter J. Cherny for their support.Howard                        Experimental                     [Page 16]

RFC 2307      Using LDAP as a Network Information Service     March 1998   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]        Kille, S., "X.500 and Domains",RFC 1279, November 1991.   [RFC1884]        Hinden, R., and S. Deering, "IP Version 6 Addressing        Architecture",RFC 1884, December 1995.   [RFC2119]        Bradner, S., "Key Words for use in RFCs to Indicate Requirement        Levels",BCP 14,RFC 2119, March 1997.   [RFC2251]        Wahl, M., Howes, T., and S. Kille, "Lightweight Directory Access        Protocol (v3)",RFC 2251, December 1997.   [RFC2252]        Wahl, M., Coulbeck, A., Howes, T., and S. Kille, "Lightweight        Directory Access Protocol (v3): Attribute Syntax Definitions",RFC 2252, December 1997.   [RFC2254]        Howes, T., "The String Representation of LDAP Search Filters",RFC 2254, December 1997.   [RFC2256]        Wahl, M., "A Summary of the X.500(96) User Schema for use with        LDAPv3",RFC 2256, December 1997.   [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.Howard                        Experimental                     [Page 17]

RFC 2307      Using LDAP as a Network Information Service     March 1998   [XOPEN]        ISO/IEC 9945-1:1990, Information Technology - Portable Operating        Systems Interface (POSIX) - Part 1: Systems Application        Programming Interface (API) [C Language]10. Author's Address   Luke Howard   PO Box 59   Central Park Vic 3145   Australia   EMail: lukeh@xedoc.comHoward                        Experimental                     [Page 18]

RFC 2307      Using LDAP as a Network Information Service     March 1998A. Example entries   The examples described in this section are provided to illustrate the   schema described in this memo. They are not meant to be exhaustive.   The following entry is an example of the posixAccount class:           dn: uid=lester, dc=aja, dc=com           objectClass: top           objectClass: account           objectClass: posixAccount           uid: lester           cn: Lester the Nightfly           userPassword: {crypt}X5/DBrWPOQQaI           gecos: Lester           loginShell: /bin/csh           uidNumber: 10           gidNumber: 10           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=peg.aja.com, dc=aja, dc=com           objectClass: top           objectClass: device           objectClass: ipHost           objectClass: bootableDevice           objectClass: ieee802Device           cn: peg.aja.com           cn: www.aja.com           ipHostNumber: 10.0.0.1           macAddress: 00:00:92:90:ee:e2           bootFile: mach           bootParameter: root=fs:/nfsroot/peg           bootParameter: swap=fs:/nfsswap/peg           bootParameter: dump=fs:/nfsdump/peg   This entry represents the host canonically peg.aja.com, also known as   www.aja.com. The Ethernet address and four boot parameters are also   specified.Howard                        Experimental                     [Page 19]

RFC 2307      Using LDAP as a Network Information Service     March 1998   An example of the nisNetgroup class:           dn: cn=nightfly, dc=aja, dc=com           objectClass: top           objectClass: nisNetgroup           cn: nightfly           nisNetgroupTriple: (charlemagne,peg,dunes.aja.com)           nisNetgroupTriple: (lester,-,)           memberNisNetgroup: kamakiriad   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.Howard                        Experimental                     [Page 20]

RFC 2307      Using LDAP as a Network Information Service     March 1998Full Copyright Statement   Copyright (C) The Internet Society (1998).  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, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, 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 procedures 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.Howard                        Experimental                     [Page 21]