rfc2307.txt

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   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 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 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.





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7. Security Considerations

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



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   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.






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   [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: [e-mail]






































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A. 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.






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   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.





















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Full 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
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   The limited permissions granted above are perpetual and will not be
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   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
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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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