Anonymity Support for Kerberos
RFC 6112

Internet Engineering Task Force (IETF)                            L. Zhu
Request for Comments: 6112                                      P. Leach
Updates: 4120, 4121, 4556                          Microsoft Corporation
Category: Standards Track                                     S. Hartman
ISSN: 2070-1721                                        Painless Security
                                                              April 2011

                     Anonymity Support for Kerberos

Abstract

   This document defines extensions to the Kerberos protocol to allow a
   Kerberos client to securely communicate with a Kerberos application
   service without revealing its identity, or without revealing more
   than its Kerberos realm.  It also defines extensions that allow a
   Kerberos client to obtain anonymous credentials without revealing its
   identity to the Kerberos Key Distribution Center (KDC).  This
   document updates RFCs 4120, 4121, and 4556.

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/rfc6112.

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   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Zhu, et al.                  Standards Track                    [Page 1]
RFC 6112               Kerberos Anonymity Support             April 2011

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
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   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Protocol Description . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Anonymity Support in AS Exchange . . . . . . . . . . . . .  5
       4.1.1.  Anonymous PKINIT . . . . . . . . . . . . . . . . . . .  6
     4.2.  Anonymity Support in TGS Exchange  . . . . . . . . . . . .  7
     4.3.  Subsequent Exchanges and Protocol Actions Common to AS
           and TGS for Anonymity Support  . . . . . . . . . . . . . .  9
   5.  Interoperability Requirements  . . . . . . . . . . . . . . . . 10
   6.  GSS-API Implementation Notes . . . . . . . . . . . . . . . . . 10
   7.  PKINIT Client Contribution to the Ticket Session Key . . . . . 11
     7.1.  Combining Two Protocol Keys  . . . . . . . . . . . . . . . 12
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     11.2. Informative References . . . . . . . . . . . . . . . . . . 16

Zhu, et al.                  Standards Track                    [Page 2]
RFC 6112               Kerberos Anonymity Support             April 2011

1.  Introduction

   In certain situations, the Kerberos [RFC4120] client may wish to
   authenticate a server and/or protect communications without revealing