draft-williams-gssapi-prf-00.txt [plain text]
NETWORK WORKING GROUP N. Williams
Internet-Draft Sun
Expires: December 30, 2004 S. Hartman
MIT
July 2004
A PRF API extension for the GSS-API
draft-williams-gssapi-prf-00.txt
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Abstract
This document defines a Pseudo-Random Function (PRF) extension to the
GSS-API for keying application protocols given an established GSS-API
security context.
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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 . . . . . . . . . . . . . . . . . . . 6
5. Normative . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . 8
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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
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 PRF extension to the GSS-API.
At this point EAP may be the primary consumer of this extension.
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3. GSS_Pseudo_random()
Inputs:
o context CONTEXT handle,
o prf_in OCTET STRING
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_FAILURE indicates failure or lack of support; the minor
status code may provide additional information.
This function applies the 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 result (prf_out).
3.1 C-Bindings
OM_uint32 gss_pseudo_random(
OM_uint32 *minor_status,
gss_ctx_id_t context,
const gss_buffer_t prf_in,
gss_buffer_t prf_out
);
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4. Security Considerations
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.
Care should be taken in properly designing a mechanism's PRF
function. Cryptographic hash functions which do not provide strong
collision resistance should not be used, except through HMAC.
GSS mechanisms' PRF functions may output fewer octets than the
application may need, therefore GSS-API applications that use
GSS_Pseudo_random() may require a "PRF+" construction based on
GSS_Pseudo_random().
[Question: Should GSS_Pseudo_random() have an input roughly
corresponding to the "key usage" used for key derivation in Kerberos
V?]
5 Normative
[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.
Authors' Addresses
Nicolas Williams
Sun Microsystems
5300 Riata Trace Ct
Austin, TX 78727
US
EMail: Nicolas.Williams@sun.com
Sam Hartman
Massachussets Institute of Technology
...
..., MA ...
US
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EMail: hartmans@mit.edu
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Acknowledgment
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