KITTEN WG N. Williams
Internet-Draft Sun
Intended status: Standards Track March 9, 2009
Expires: September 10, 2009
Clarifications and Extensions to the GSS-API for the Use of Channel
Bindings
draft-ietf-kitten-gssapi-channel-bindings-06.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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