rfc3112.txt

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   user/password authentication.

3.2. SHA1 scheme

   The SHA1 [SHA1] scheme name is "SHA1".

   The authValue is the base64 encoding of a SHA1 digest of the
   concatenation the user password and the salt.  The base64 encoding of
   the salt is provided in the authInfo field.  The salt MUST be at
   least 64 bits long.  Implementations of this scheme MUST support
   salts up to 128 bits in length.

   Example:
      Given a user "joe" who's password is "mary" and a salt of "salt",
      the authInfo field would be the base64 encoding of "salt" and the
      authValue field would be the base64 encoding of the SHA1 digest of
      "marysalt".

   A match against an asserted password and an attribute value of this
   scheme SHALL be true if and only if the SHA1 digest of concatenation
   of the asserted value and the salt is equal to the SHA1 digest
   contained in AuthValue.  The match SHALL be undefined if the server
   is unable to complete the equality test for any reason.  Otherwise
   the match SHALL be false.



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RFC 3112          LDAP Authentication Password Schema           May 2001


   Values of this scheme SHOULD only be used to implement simple
   user/password authentication.

4. Implementation Issues

   For all implementations of this specification:

      Servers MAY restrict which schemes are used in conjunction with a
      particular authentication process but SHOULD use all values of
      selected schemes.  If the asserted password matches any of the
      stored values, the asserted password SHOULD be considered valid.
      Servers MAY use other authentication storage mechanisms, such as
      userPassword or an external password store, in conjunction with
      authPassword to support the authentication process.

      Servers that support simple bind MUST support the SHA1 scheme and
      SHOULD support the MD5 scheme.

      Servers SHOULD NOT publish values of authPassword nor allow
      operations which expose authPassword values or AuthPasswordMatch
      assertions to unless confidentiality protection is in place.

      Clients SHOULD NOT initiate operations which provide or request
      values of authPassword or make authPasswordMatch assertions unless
      confidentiality protection is in place.

      Clients SHOULD NOT assume that a successful AuthPasswordMatch,
      whether by compare or search, is sufficient to gain directory
      access.  The bind operation MUST be used to authenticate to the
      directory.

5. Security Considerations

   This document describes how authentication information may be stored
   in a directory.  Authentication information MUST be adequately
   protected as unintended disclosure will allow attackers to gain
   immediate access to the directory as described by [RFC2829].

   As flaws may be discovered in the hashing algorithm or with a
   particular implementation of the algorithm or values could be subject
   to various attacks if exposed, values of AuthPassword SHOULD be
   protected as if they were clear text passwords.  When values are
   transferred, privacy protections, such as IPSEC or TLS, SHOULD be in
   place.

   Clients SHOULD use strong authentication mechanisms [RFC2829].





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RFC 3112          LDAP Authentication Password Schema           May 2001


   AuthPasswordMatch matching rule allows applications to test the
   validity of a user password and, hence, may be used to mount an
   attack.  Servers SHOULD take appropriate measures to protect the
   directory from such attacks.

   Some password schemes may require CPU intensive operations.  Servers
   SHOULD take appropriate measures to protect against Denial of Service
   attacks.

   AuthPassword does not restrict an authentication identity to a single
   password.  An attacker who gains write access to this attribute may
   store additional values without disabling the user's true
   password(s).  Use of policy aware clients and servers is RECOMMENDED.

   The level of protection offered against various attacks differ from
   scheme to scheme.  It is RECOMMENDED that servers support scheme
   selection as a configuration item.  This allows for a scheme to be
   easily disabled if a significant security flaw is discovered.

6. Acknowledgment

   This document borrows from a number of IETF documents and is based
   upon input from the IETF LDAPext working group.

7. Bibliography

   [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
             April 1992

   [RFC2219] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2234] Crocker, D., Editor, P. Overell, "Augmented BNF for Syntax
             Specifications: ABNF", RFC 2234, November 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.

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

   [RFC2307] Howard, L., "An Approach for Using LDAP as a Network
             Information Service", RFC 2307, March 1998.




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RFC 3112          LDAP Authentication Password Schema           May 2001


   [RFC2829] Wahl, M., Alvestrand, H., Hodges, J. and R. Morgan,
             "Authentication Methods for LDAP", RFC 2829, June 2000.

   [RFC3062] Zeilenga, K., "LDAP Password Modify Extended Operation",
             RFC 3062, February 2001.

   [SHA1]    NIST, FIPS PUB 180-1: Secure Hash Standard, April 1995.

8. Author's Address

   Kurt D. Zeilenga
   OpenLDAP Foundation

   EMail: [e-mail]





































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RFC 3112          LDAP Authentication Password Schema           May 2001


9.  Full Copyright Statement

   Copyright (C) The Internet Society (2001).  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.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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