draft-ietf-kitten-gssapi-prf-01.txt [plain text]
NETWORK WORKING GROUP N. Williams
Internet-Draft Sun
Expires: December 30, 2004 July 2004
A PRF API extension for the GSS-API
draft-ietf-kitten-gssapi-prf-01.txt
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document defines a Pseudo-Random Function (PRF) extension to the
Generic Security Service Applicatoin Programming Interface (GSS-API)
for keying application protocols given an established GSS-API
security context. The primary intended use of this function is to
key secure session layers that don't or cannot use GSS-API
per-message MIC (message integrity check) and wrap tokens for session
protection.
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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 . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Normative References . . . . . . . . . . . . . . . . . . . . . 8
5.2 Informative References . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
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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 pseudo-random function (PRF)
extension to the GSS-API.
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3. GSS_Pseudo_random()
Inputs:
o context CONTEXT handle,
o prf_in OCTET STRING,
o desired_output_len INTEGER
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_UNAVAILABLE indicates that the mechanism lacks support for
this function.
o GSS_S_FAILURE indicates failure or lack of support; the minor
status code may provide additional information.
This function applies the established 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 resulting
octet string (prf_out) of desired_output_len length.
The output string of this function MUST be a pseudo-random function
[GGM1][GGM2] of the input keyed with key material from the
established security context -- the chances of getting the same
output given different input parameters should be exponentially
small.
This function, applied to the same inputs by an initiator and
acceptor using the same established context, MUST produce the *same
results* for both, the initiator and acceptor, even if called
multiple times for the same context.
Mechanisms MAY limit the output of the PRF according, possibly in
ways related to the types of cryptographic keys available for the PRF
function, thus the prf_out output of GSS_Pseudo_random() MAY be
smaller than requested.
3.1 C-Bindings
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OM_uint32 gss_pseudo_random(
OM_uint32 *minor_status,
gss_ctx_id_t context,
const gss_buffer_t prf_in,
ssize_t desired_output_len,
gss_buffer_t prf_out
);
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4. Security Considerations
Care should be taken in properly designing a mechanism's PRF
function.
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.
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5. References
5.1 Normative References
[GGM1] Goldreich, O., Goldwasser, S. and S. Micali, "How to
Construct Random Functions", October 1986.
[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.
5.2 Informative References
[GGM2] Goldreich, O., Goldwasser, S. and S. Micali, "On the
Cryptographic Applications of Random Functions", 1985.
[RFC1750] Eastlake, D., Crocker, S. and J. Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
Author's Address
Nicolas Williams
Sun Microsystems
5300 Riata Trace Ct
Austin, TX 78727
US
EMail: Nicolas.Williams@sun.com
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