1 NETWORK WORKING GROUP L. Zhu
2 Internet-Draft K. Jaganathan
3 Expires: May 21, 2005 Microsoft Corporation
9 OCSP Support for PKINIT
10 draft-ietf-krb-wg-ocsp-for-pkinit-02
14 This document is an Internet-Draft and is subject to all provisions
15 of section 3 of RFC 3667. By submitting this Internet-Draft, each
16 author represents that any applicable patent or other IPR claims of
17 which he or she is aware have been or will be disclosed, and any of
18 which he or she become aware will be disclosed, in accordance with
21 Internet-Drafts are working documents of the Internet Engineering
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26 Internet-Drafts are draft documents valid for a maximum of six months
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29 material or to cite them other than as "work in progress."
31 The list of current Internet-Drafts can be accessed at
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34 The list of Internet-Draft Shadow Directories can be accessed at
35 http://www.ietf.org/shadow.html.
37 This Internet-Draft will expire on May 21, 2005.
41 Copyright (C) The Internet Society (2004).
45 This document defines a mechanism to enable in-band transmission of
46 OCSP responses. These responses are used to verify the validity of
47 the certificates used in PKINIT - the Kerberos Version 5 extension
48 that provides for the use of public key cryptography.
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60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
61 2. Conventions Used in This Document . . . . . . . . . . . . . 4
62 3. Message Definition . . . . . . . . . . . . . . . . . . . . . 5
63 4. Security Considerations . . . . . . . . . . . . . . . . . . 6
64 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . 7
65 6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . 8
66 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 8
68 Intellectual Property and Copyright Statements . . . . . . . 10
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111 Internet-Draft OCSP Support for PKINIT November 2004
116 Online Certificate Status Protocol (OCSP) [RFC2560] enables
117 applications to obtain timely information regarding the revocation
118 status of a certificate. Because OCSP responses are well-bounded and
119 small in size, constrained clients may wish to use OCSP to check the
120 validity of KDC certificates in order to avoid transmission of large
121 Certificate Revocation Lists (CRLs) and therefore save bandwidth on
122 constrained networks [OCSP-PROFILE].
124 This document defines a pre-authentication type [CLARIFICATIONS],
125 where the client and the KDC MAY piggyback OCSP responses for
126 certificates used in authentication exchanges, as defined in
129 By using this OPTIONAL extension, PKINIT clients and the KDC can
130 maximize the reuse of cached OCSP responses.
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167 Internet-Draft OCSP Support for PKINIT November 2004
170 2. Conventions Used in This Document
172 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
173 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
174 document are to be interpreted as described in [RFC2119].
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226 3. Message Definition
228 A pre-authentication type identifier is defined for this mechanism:
230 PA-PK-OCSP-RESPONSE 16
232 The corresponding pre-authentication field contains OCSP data as
235 PA-PK-OCSP-DATA ::= SEQUENCE OF OcspResponse
237 OcspResponse ::= OCTET STRING
238 -- contains a complete OCSP response,
239 -- defined in [RFC2560]
241 The client MAY send OCSP responses for certificates used in
242 PA-PK-AS-REQ [PKINIT] via a PA-PK-OCSP-RESPONSE.
244 The KDC that receives a PA-PK-OCSP-RESPONSE the SHOULD send a
245 PA-PK-OCSP-RESPONSE in response. The client can request a
246 PA-PK-OCSP-RESPONSE by using an empty sequence in its request.
248 The KDC MAY send a PA-PK-OCSP-RESPONSE when it does not receive a
249 PA-PK-OCSP-RESPONSE from the client.
251 The PA-PK-OCSP-RESPONSE sent by the KDC contains OCSP responses for
252 certificates used in PA-PK-AS-REP [PKINIT].
254 Note the lack of integrity protection for the empty or missing OCSP
255 response; lack of an expected OCSP response from the KDC for the
256 KDC's certificates SHOULD be treated as an error by the client,
257 unless it is configured otherwise.
259 When using OCSP, the response is signed by the OCSP server, which is
260 trusted by the receiver. Depending on local policy, further
261 verification of the validity of the OCSP servers MAY need to be done.
263 The client and the KDC SHOULD ignore invalid OCSP responses received
264 via this mechanism, and they MAY implement CRL processing logic as a
265 fall-back position, if the OCSP responses received via this mechanism
266 alone are not sufficient for the verification of certificate
267 validity. The client and/or the KDC MAY ignore a valid OCSP response
268 and perform their own revocation status verification independently.
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282 4. Security Considerations
284 The pre-authentication data in this document do not actually
285 authenticate any principals, and MUST be used in conjunction with
288 There is a downgrade attack against clients which want OCSP responses
289 from the KDC for the KDC's certificates. The clients, however, can
290 treat the absence of valid OCSP responses as an error, based on their
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338 5. IANA Considerations
340 This document defines a new pre-authentication type for use with
341 PKINIT to encode OCSP responses. The official value for this padata
342 identifier need to be acquired from IANA.
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391 Internet-Draft OCSP Support for PKINIT November 2004
396 This document was based on conversations among the authors, Jeffrey
397 Altman, Sam Hartman, Martin Rex and other members of the Kerberos
403 Neuman, B., Yu, Y., Hartman, S. and K. Raeburn, "The
404 Kerberos Network Authentication Service (V5)",
405 draft-ietf-krb-wg-kerberos-clarifications, Work in
409 Deacon, A. and R. Hurst, "Lightweight OCSP Profile for
410 High Volume Environments",
411 draft-ietf-pkix-lightweight-ocsp-profile, Work in
414 [PKINIT] Tung, B., Neuman, B. and S. Medvinsky, "Public Key
415 Cryptography for Initial Authentication in Kerberos",
416 draft-ietf-cat-kerberos-pk-init, Work in progress.
418 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
419 Requirement Levels", BCP 14, RFC 2119, March 1997.
421 [RFC2560] Myers, M., Ankney, R., Malpani, A., Galperin, S. and C.
422 Adams, "X.509 Internet Public Key Infrastructure Online
423 Certificate Status Protocol - OCSP", RFC 2560, June 1999.
429 Microsoft Corporation
434 EMail: lzhu@microsoft.com
438 Microsoft Corporation
443 EMail: karthikj@microsoft.com
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459 EMail: Nicolas.Williams@sun.com
504 Zhu, et al. Expires May 21, 2005 [Page 9]
506 Internet-Draft OCSP Support for PKINIT November 2004
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