3 NETWORK WORKING GROUP N. Williams
5 Expires: December 30, 2004 July 2004
8 A PRF API extension for the GSS-API
9 draft-ietf-kitten-gssapi-prf-01.txt
13 By submitting this Internet-Draft, I certify that any applicable
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34 This Internet-Draft will expire on December 30, 2004.
38 Copyright (C) The Internet Society (2004). All Rights Reserved.
42 This document defines a Pseudo-Random Function (PRF) extension to the
43 Generic Security Service Applicatoin Programming Interface (GSS-API)
44 for keying application protocols given an established GSS-API
45 security context. The primary intended use of this function is to
46 key secure session layers that don't or cannot use GSS-API
47 per-message MIC (message integrity check) and wrap tokens for session
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62 1. Conventions used in this document . . . . . . . . . . . . . . 3
63 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
64 3. GSS_Pseudo_random() . . . . . . . . . . . . . . . . . . . . . 5
65 3.1 C-Bindings . . . . . . . . . . . . . . . . . . . . . . . . . . 5
66 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
67 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
68 5.1 Normative References . . . . . . . . . . . . . . . . . . . . . 8
69 5.2 Informative References . . . . . . . . . . . . . . . . . . . . 8
70 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
71 Intellectual Property and Copyright Statements . . . . . . . . 9
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116 1. Conventions used in this document
118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
120 document are to be interpreted as described in [RFC2119].
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174 A need has arisen for users of the GSS-API to key applications'
175 cryptographic protocols using established GSS-API security contexts.
176 Such applications can use the GSS-API for authentication, but not for
177 transport security (for whatever reasons), and since the GSS-API does
178 not provide a method for obtaining keying material from established
179 security contexts such applications cannot make effective use of the
182 To address this need we define a pseudo-random function (PRF)
183 extension to the GSS-API.
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228 3. GSS_Pseudo_random()
232 o context CONTEXT handle,
233 o prf_in OCTET STRING,
234 o desired_output_len INTEGER
238 o major_status INTEGER,
239 o minor_status INTEGER,
240 o prf_out OCTET STRING
242 Return major_status codes:
243 o GSS_S_COMPLETE indicates no error.
244 o GSS_S_NO_CONTEXT indicates that a null context has been provided
246 o GSS_S_CONTEXT_EXPIRED indicates that an expired context has been
248 o GSS_S_UNAVAILABLE indicates that the mechanism lacks support for
250 o GSS_S_FAILURE indicates failure or lack of support; the minor
251 status code may provide additional information.
253 This function applies the established context's mechanism's keyed PRF
254 function to the input data (prf_in), keyed with key material
255 associated with the given security context and outputs the resulting
256 octet string (prf_out) of desired_output_len length.
258 The output string of this function MUST be a pseudo-random function
259 [GGM1][GGM2] of the input keyed with key material from the
260 established security context -- the chances of getting the same
261 output given different input parameters should be exponentially
264 This function, applied to the same inputs by an initiator and
265 acceptor using the same established context, MUST produce the *same
266 results* for both, the initiator and acceptor, even if called
267 multiple times for the same context.
269 Mechanisms MAY limit the output of the PRF according, possibly in
270 ways related to the types of cryptographic keys available for the PRF
271 function, thus the prf_out output of GSS_Pseudo_random() MAY be
272 smaller than requested.
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284 OM_uint32 gss_pseudo_random(
285 OM_uint32 *minor_status,
286 gss_ctx_id_t context,
287 const gss_buffer_t prf_in,
288 ssize_t desired_output_len,
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340 4. Security Considerations
342 Care should be taken in properly designing a mechanism's PRF
345 GSS mechanisms' PRF functions should use a key derived from contexts'
346 session keys and should preserve the forward security properties of
347 the mechanisms' key exchanges.
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398 5.1 Normative References
400 [GGM1] Goldreich, O., Goldwasser, S. and S. Micali, "How to
401 Construct Random Functions", October 1986.
403 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
404 Requirement Levels", BCP 14, RFC 2119, March 1997.
406 [RFC2743] Linn, J., "Generic Security Service Application Program
407 Interface Version 2, Update 1", RFC 2743, January 2000.
409 [RFC2744] Wray, J., "Generic Security Service API Version 2 :
410 C-bindings", RFC 2744, January 2000.
412 5.2 Informative References
414 [GGM2] Goldreich, O., Goldwasser, S. and S. Micali, "On the
415 Cryptographic Applications of Random Functions", 1985.
417 [RFC1750] Eastlake, D., Crocker, S. and J. Schiller, "Randomness
418 Recommendations for Security", RFC 1750, December 1994.
429 EMail: Nicolas.Williams@sun.com
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