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-00.txtdraft-ietf-kitten-gssapi-prf-01.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 30, 2004. Copyright Notice 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. Table of Contents 1. Conventions used in this document . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. GSS_Pseudo_random() . . . . . . . . . . . . . . . . . . . . . 5 3.1 C-Bindings . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 Normative References . . . . . . . . . . . . . . . . . . . . . 8 5.2 Informative References . . . . . 7. . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 78 Intellectual Property and Copyright Statements . . . . . . . . 89 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]. 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 PRFpseudo-random function (PRF) extension to the GSS-API. 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 functions.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. Mechanisms MAY limit theThe output string of this function MUST be a pseudo-random function [GGM1][GGM2] of the PRF according, possibly in ways related toinput keyed with key material from the types of cryptographic keys available forestablished security context -- the PRF function, thuschances of getting the prf_outsame output of GSS_Pseudo_random() MAYgiven different input parameters should be smaller than requested.exponentially small. This function, applied to the same inputs by an initiator and acceptor using the same established context, producesMUST produce the *same results* for both, the initiator and acceptor. Applications SHOULD NOT make more than one GSS PRF call per-established security context. If an application makesacceptor, even if called multiple calls, per established security context, totimes for the GSS PRF, then it is up tosame context. Mechanisms MAY limit the application to ensure synchronization of orderoutput of function calls between initiator and acceptor; such applications SHOULD provide different input octet strings to each such GSSthe PRF call. The result of making multiple callsaccording, possibly in ways related to the GSStypes of cryptographic keys available for the PRF in different order onfunction, thus the initiator and acceptor sides is undefined.prf_out output of GSS_Pseudo_random() MAY be smaller than requested. 3.1 C-Bindings 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 ); 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. 55. 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 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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