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Versions: 00 01 02 03 04 05 06 07 RFC 5554

KITTEN WG                                                    N. Williams
Internet-Draft                                                       Sun
Updates: rfc2743                                           April 6, 2009
(if approved)
Intended status: Standards Track
Expires: October 8, 2009


  Clarifications and Extensions to the GSS-API for the Use of Channel
                                Bindings
            draft-ietf-kitten-gssapi-channel-bindings-07.txt

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Abstract

   This document clarifies and generalizes the Generic Security Services
   Application Programming Interface (GSS-API) "channel bindings"
   facility, and imposes requirements on future GSS-API mechanisms and
   programming language bindings of the GSS-API.


Table of Contents

   1.  Conventions used in this document  . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  New Requirements for GSS-API Mechanisms  . . . . . . . . . . .  5
   4.  Generic Structure for GSS-API Channel Bindings . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11































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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].














































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2.  Introduction

   The base GSS-API v2, update 1 specification [RFC2743] provides a
   facility for channel binding (see also [RFC5056]), but its treatment
   was incomplete.  The C-bindings of the GSS-API [RFC2744] expanded a
   little on this facility in what should have been a generic way, but
   was a C-specific way, and still, the treatment of this facility was
   incomplete.

   This document clarifies the GSS-API's channel binding facility and
   generalizes the parts of it that are specified in the C-bindings
   document but which should have been generic from the first.







































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3.  New Requirements for GSS-API Mechanisms

   Given the publication of RFC5056 we now assert that all new GSS-API
   mechanisms that support channel binding MUST conform to [RFC5056].















































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4.  Generic Structure for GSS-API Channel Bindings

   The base GSS-API v2, update 1 specification [RFC2743] provides a
   facility for channel binding.  It models channel bindings as an OCTET
   STRING and leaves it to the GSS-API v2, update 1 C-Bindings
   specification to specify the structure of the contents of the channel
   bindings OCTET STRINGs.  The C-Bindings specification [RFC2744] then
   defines, in terms of C, what should have been a generic structure for
   channel bindings.  The Kerberos V GSS mechanism [RFC4121] also
   defines a method for encoding GSS channel bindings in a way that is
   independent of the C-Bindings -- otherwise the mechanism's channel
   binding facility would not be useable with other language bindings.

   In other words, the structure of GSS channel bindings given in
   [RFC2744] is actually generic, rather than specific to the C
   programming language.

   We generalize it as shown below, using the same pseudo-ASN.1 as is
   used in RFC2743.  Although the figure below is, indeed, a valid ASN.1
   [CCITT.X680.2002] type, we do not provide a full ASN.1 module as none
   is needed because no standard encoding of this structure is needed --
   the definition below is part of an abstract API, not part of a
   protocol defining bits on the wire.  GSS-API mechanisms do need to
   encode the contents of this structure, but that encoding will be
   mechanism specific (see below).

      GSS-CHANNEL-BINDINGS ::= SEQUENCE {
              initiator-address-type  INTEGER,      -- See RFC2744
              initiator-address       OCTET STRING, -- See RFC2744
              acceptor-address-type   INTEGER,      -- See RFC2744
              acceptor-address        OCTET STRING, -- See RFC2744
              application-data        OCTET STRING -- See RFC5056
      }

                Abstract GSS-API channel bindings structure

   The values for the address fields are described in [RFC2744].

   New language-specific bindings of the GSS-API SHOULD specify a
   language-specific formulation of this structure.

   Where a language binding of the GSS-API models channel bindings as
   OCTET STRINGs (or the language's equivalent), then the implementation
   MUST assume that the given bindings correspond only to the
   application-data field of GSS-CHANNEL-BINDINGS as shown above, rather
   than some encoding of GSS-CHANNEL-BINDINGS.

   As mentioned above, [RFC4121] describes an encoding of the above GSS-



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   CHANNEL-BINDINGS structure, and then hashes that encoding.  Other
   GSS-API mechanisms are free to use that encoding.

















































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5.  IANA Considerations

   There are no IANA considerations in this document.
















































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6.  Security Considerations

   For general security considerations relating to channel bindings see
   [RFC5056].

   Language bindings that use OCTET STRING (or equivalent) for channel
   bindings will not support the use of network addresses as channel
   bindings.  This should not cause any security problems, as the use of
   network addresses as channel bindings is not generally secure.
   However, it is important that "end-point channel bindings" not be
   modelled as network addresses, otherwise such channel bindings may
   not be useable with all language bindings of the GSS-API.







































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7.  References

7.1.  Normative References

   [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.

   [RFC4121]  Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
              Version 5 Generic Security Service Application Program
              Interface (GSS-API) Mechanism: Version 2", RFC 4121,
              July 2005.

   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure
              Channels", RFC 5056, November 2007.

7.2.  Informative References

   [CCITT.X680.2002]
              International International Telephone and Telegraph
              Consultative Committee, "Abstract Syntax Notation One
              (ASN.1): Specification of basic notation",
              CCITT Recommendation X.680, July 2002.























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Author's Address

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

   Email: Nicolas.Williams@sun.com










































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