A Pseudo-Random Function (PRF) for the Kerberos V Generic Security Service Application Program Interface (GSS-API) Mechanism
RFC 7802

Document Type RFC - Proposed Standard (March 2016; No errata)
Obsoletes RFC 4402
Last updated 2018-12-20
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Internet Engineering Task Force (IETF)                          S. Emery
Request for Comments: 7802                                        Oracle
Obsoletes: 4402                                              N. Williams
Category: Standards Track                                   Cryptonector
ISSN: 2070-1721                                               March 2016

   A Pseudo-Random Function (PRF) for the Kerberos V Generic Security
       Service Application Program Interface (GSS-API) Mechanism

Abstract

   This document defines the Pseudo-Random Function (PRF) for the
   Kerberos V mechanism for the Generic Security Service Application
   Program Interface (GSS-API), based on the PRF defined for the
   Kerberos V cryptographic framework, for keying application protocols
   given an established Kerberos V GSS-API security context.

   This document obsoletes RFC 4402 and reclassifies that document as
   Historic.  RFC 4402 starts the PRF+ counter at 1; however, a number
   of implementations start the counter at 0.  As a result, the original
   specification would not be interoperable with existing
   implementations.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7802.

Emery & Williams             Standards Track                    [Page 1]
RFC 7802              A PRF for the Kerberos V Mech           March 2016

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   3.  Kerberos V GSS Mechanism PRF  . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Appendix A.  Test Vectors . . . . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   This document specifies the Kerberos V GSS-API mechanism's [RFC4121]
   pseudo-random function corresponding to [RFC4401].  The function is a
   "PRF+" style construction.  For more information, see [RFC4401],
   [RFC2743], [RFC2744], and [RFC4121].

   This document obsoletes RFC 4402 and reclassifies that document as
   Historic.  RFC 4402 starts the PRF+ counter at 1; however, a number
   of implementations start the counter at 0.  As a result, the original
   specification would not be interoperable with existing
   implementations.

2.  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].

Emery & Williams             Standards Track                    [Page 2]
RFC 7802              A PRF for the Kerberos V Mech           March 2016

3.  Kerberos V GSS Mechanism PRF

   The GSS-API PRF [RFC4401] function for the Kerberos V mechanism
   [RFC4121] shall be the output of a PRF+ function based on the
   encryption type's PRF function keyed with the negotiated session key
   of the security context corresponding to the 'prf_key' input
   parameter of GSS_Pseudo_random().

   This PRF+ MUST be keyed with the key indicated by the 'prf_key' input
   parameter as follows:

   o  GSS_C_PRF_KEY_FULL -- use the sub-session key asserted by the
      acceptor (if any exists), or the sub-session asserted by the
      initiator (if any exists), or the Ticket's session key.

   o  GSS_C_PRF_KEY_PARTIAL -- use the sub-session key asserted by the
      initiator (if any exists) or the Ticket's session key.

   The PRF+ function is a simple counter-based extension of the Kerberos
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