

NETWORK WORKING GROUP                                        N. Williams
Internet-Draft                                                       Sun
Expires: December 30, 2004                                     July 2004


                  A PRF API extension for the GSS-API
                  draft-ietf-kitten-gssapi-prf-01.txt

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.

   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 documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

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

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

   This Internet-Draft will expire on December 30, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document defines a Pseudo-Random Function (PRF) extension to the
   Generic Security Service Applicatoin Programming Interface (GSS-API)
   for keying application protocols given an established GSS-API
   security context.  The primary intended use of this function is to
   key secure session layers that don't or cannot use GSS-API
   per-message MIC (message integrity check) and wrap tokens for session
   protection.






Williams               Expires December 30, 2004                [Page 1]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


Table of Contents

   1.  Conventions used in this document  . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  GSS_Pseudo_random()  . . . . . . . . . . . . . . . . . . . . .  5
   3.1 C-Bindings . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   5.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.1 Normative References . . . . . . . . . . . . . . . . . . . . .  8
   5.2 Informative References . . . . . . . . . . . . . . . . . . . .  8
       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  8
       Intellectual Property and Copyright Statements . . . . . . . .  9







































Williams               Expires December 30, 2004                [Page 2]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


1.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].














































Williams               Expires December 30, 2004                [Page 3]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


2.  Introduction

   A need has arisen for users of the GSS-API to key applications'
   cryptographic protocols using established GSS-API security contexts.
   Such applications can use the GSS-API for authentication, but not for
   transport security (for whatever reasons), and since the GSS-API does
   not provide a method for obtaining keying material from established
   security contexts such applications cannot make effective use of the
   GSS-API.

   To address this need we define a pseudo-random function (PRF)
   extension to the GSS-API.







































Williams               Expires December 30, 2004                [Page 4]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


3.  GSS_Pseudo_random()

   Inputs:

   o  context CONTEXT handle,
   o  prf_in OCTET STRING,
   o  desired_output_len INTEGER

   Outputs:

   o  major_status INTEGER,
   o  minor_status INTEGER,
   o  prf_out OCTET STRING

   Return major_status codes:
   o  GSS_S_COMPLETE indicates no error.
   o  GSS_S_NO_CONTEXT indicates that a null context has been provided
      as input.
   o  GSS_S_CONTEXT_EXPIRED indicates that an expired context has been
      provided as input.
   o  GSS_S_UNAVAILABLE indicates that the mechanism lacks support for
      this function.
   o  GSS_S_FAILURE indicates failure or lack of support; the minor
      status code may provide additional information.

   This function applies the established context's mechanism's keyed PRF
   function to the input data (prf_in), keyed with key material
   associated with the given security context and outputs the resulting
   octet string (prf_out) of desired_output_len length.

   The output string of this function MUST be a pseudo-random function
   [GGM1][GGM2] of the input keyed with key material from the
   established security context -- the chances of getting the same
   output given different input parameters should be exponentially
   small.

   This function, applied to the same inputs by an initiator and
   acceptor using the same established context, MUST produce the *same
   results* for both, the initiator and acceptor, even if called
   multiple times for the same context.

   Mechanisms MAY limit the output of the PRF according, possibly in
   ways related to the types of cryptographic keys available for the PRF
   function, thus the prf_out output of GSS_Pseudo_random() MAY be
   smaller than requested.

3.1  C-Bindings




Williams               Expires December 30, 2004                [Page 5]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


   OM_uint32 gss_pseudo_random(
     OM_uint32			*minor_status,
     gss_ctx_id_t			context,
     const gss_buffer_t		prf_in,
     ssize_t		desired_output_len,
     gss_buffer_t		prf_out
   );












































Williams               Expires December 30, 2004                [Page 6]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


4.  Security Considerations

   Care should be taken in properly designing a mechanism's PRF
   function.

   GSS mechanisms' PRF functions should use a key derived from contexts'
   session keys and should preserve the forward security properties of
   the mechanisms' key exchanges.











































Williams               Expires December 30, 2004                [Page 7]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


5.  References

5.1  Normative References

   [GGM1]     Goldreich, O., Goldwasser, S. and S. Micali, "How to
              Construct Random Functions", October 1986.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743, January 2000.

   [RFC2744]  Wray, J., "Generic Security Service API Version 2 :
              C-bindings", RFC 2744, January 2000.

5.2  Informative References

   [GGM2]     Goldreich, O., Goldwasser, S. and S. Micali, "On the
              Cryptographic Applications of Random Functions", 1985.

   [RFC1750]  Eastlake, D., Crocker, S. and J. Schiller, "Randomness
              Recommendations for Security", RFC 1750, December 1994.


Author's Address

   Nicolas Williams
   Sun Microsystems
   5300 Riata Trace Ct
   Austin, TX  78727
   US

   EMail: Nicolas.Williams@sun.com

















Williams               Expires December 30, 2004                [Page 8]

Internet-Draft      A PRF Extension for the GSS-API            July 2004


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM 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.


Copyright Statement

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

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




Williams               Expires December 30, 2004                [Page 9]


