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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'X60' is mentioned on line 100, but not defined == Unused Reference: 'X690' is defined on line 194, but no explicit reference was found in the text ** Obsolete normative reference: RFC 2560 (Obsoleted by RFC 6960) -- Possible downref: Non-RFC (?) normative reference: ref. 'X690' Summary: 5 errors (**), 0 flaws (~~), 5 warnings (==), 8 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 NETWORK WORKING GROUP L. Zhu 3 Internet-Draft K. Jaganathan 4 Expires: November 21, 2005 Microsoft Corporation 5 N. Williams 6 Sun Microsystems 7 May 20, 2005 9 OCSP Support for PKINIT 10 draft-ietf-krb-wg-ocsp-for-pkinit-05 12 Status of this Memo 14 This document is an Internet-Draft and is subject to all provisions 15 of Section 3 of RFC 3667. 17 By submitting this Internet-Draft, each author represents 18 that any applicable patent or other IPR claims of which he 19 or she is aware have been or will be disclosed, and any of 20 which he or she becomes aware will be disclosed, in 21 accordance with Section 6 of BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF), its areas, and its working groups. Note that 25 other groups may also distribute working documents as Internet- 26 Drafts. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 The list of current Internet-Drafts can be accessed at 34 http://www.ietf.org/ietf/1id-abstracts.txt. 36 The list of Internet-Draft Shadow Directories can be accessed at 37 http://www.ietf.org/shadow.html. 39 This Internet-Draft will expire on November 21, 2005. 41 Copyright Notice 43 Copyright (C) The Internet Society (2005). 45 Abstract 47 This document defines a mechanism to enable in-band transmission of 48 Online Certificate Status Protocol (OCSP) responses in the Kerberos 49 network authentication protocol. These responses are used to verify 50 the validity of the certificates used in PKINIT - the Kerberos 51 Version 5 extension that provides for the use of public key 52 cryptography. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 58 3. Message Definition . . . . . . . . . . . . . . . . . . . . . . 3 59 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 60 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 61 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 62 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 7.1 Normative References . . . . . . . . . . . . . . . . . . . 5 64 7.2 Informative References . . . . . . . . . . . . . . . . . . 5 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 5 66 Intellectual Property and Copyright Statements . . . . . . . . 7 68 1. Introduction 70 Online Certificate Status Protocol (OCSP) [RFC2560] enables 71 applications to obtain timely information regarding the revocation 72 status of a certificate. Because OCSP responses are well-bounded and 73 small in size, constrained clients may wish to use OCSP to check the 74 validity of the certificates for Kerberos Key Distribution Center 75 (KDC) in order to avoid transmission of large Certificate Revocation 76 Lists (CRLs) and therefore save bandwidth on constrained networks 77 [OCSP-PROFILE]. 79 This document defines a pre-authentication type [CLARIFICATIONS], 80 where the client and the KDC MAY piggyback OCSP responses for 81 certificates used in authentication exchanges, as defined in 82 [PKINIT]. 84 By using this OPTIONAL extension, PKINIT clients and the KDC can 85 maximize the reuse of cached OCSP responses. 87 2. Conventions Used in This Document 89 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 90 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 91 document are to be interpreted as described in [RFC2119]. 93 3. Message Definition 95 A pre-authentication type identifier is defined for this mechanism: 97 PA-PK-OCSP-RESPONSE 18 99 The corresponding padata-value field [CLARIFICATIONS] contains the 100 DER [X60] encoding of the following ASN.1 type: 102 PKOcspData ::= SEQUENCE OF OcspResponse 103 -- If more than one OcspResponse is 104 -- included, the first OcspResponse 105 -- MUST contain the OCSP response 106 -- for the signer's certificate. 108 OcspResponse ::= OCTET STRING 109 -- Contains a complete OCSP response, 110 -- as defined in [RFC2560]. 112 The client MAY send OCSP responses for certificates used in PA-PK-AS- 113 REQ [PKINIT] via a PA-PK-OCSP-RESPONSE. 115 The KDC that receives a PA-PK-OCSP-RESPONSE then SHOULD send a PA-PK- 116 OCSP-RESPONSE containing OCSP responses for certificates used in the 117 KDC's PA-PK-AS-REP. The client can request a PA-PK-OCSP-RESPONSE by 118 using a PKOcspData containing an empty sequence. 120 The KDC MAY send a PA-PK-OCSP-RESPONSE when it does not receive a PA- 121 PK-OCSP-RESPONSE from the client. 123 The PA-PK-OCSP-RESPONSE sent by the KDC contains OCSP responses for 124 certificates used in PA-PK-AS-REP [PKINIT]. 126 Note the lack of integrity protection for the empty or missing OCSP 127 response; lack of an expected OCSP response from the KDC for the 128 KDC's certificates SHOULD be treated as an error by the client, 129 unless it is configured otherwise. 131 When using OCSP, the response is signed by the OCSP server, which is 132 trusted by the receiver. Depending on local policy, further 133 verification of the validity of the OCSP servers may be needed 135 The client and the KDC SHOULD ignore invalid OCSP responses received 136 via this mechanism, and they MAY implement CRL processing logic as a 137 fall-back position, if the OCSP responses received via this mechanism 138 alone are not sufficient for the verification of certificate 139 validity. The client and/or the KDC MAY ignore a valid OCSP response 140 and perform their own revocation status verification independently. 142 4. Security Considerations 144 The pre-authentication data in this document do not actually 145 authenticate any principals, but is designed to be used in 146 conjunction with PKINIT. 148 There is no binding between PA-PK-OCSP-RESPONSE pre-authentication 149 data and PKINIT pre-authentication data other than a given OCSP 150 response corresponding to a certificate used in a PKINIT pre- 151 authentication data element. Attacks involving removal or 152 replacement of PA-PK-OCSP-RESPONSE pre-authentication data elements 153 are, at worst, downgrade attacks, where a PKINIT client or KDC would 154 proceed without use of CRLs or OCSP for certificate validation, or 155 denial of service attacks, where a PKINIT client or KDC that cannot 156 validate the other's certificate without an accompanying OCSP 157 response might reject the AS exchange or where they might have to 158 download very large CRLs in order to continue. Kerberos V does not 159 protect against denial-of-service attacks, therefore the denial-of- 160 service aspect of these attacks are acceptable. 162 If a PKINIT client or KDC cannot validate certificates without the 163 aid of a valid PA-PK-OCSP-RESPONSE then it SHOULD fail the AS 164 exchange, possibly according to local configuration. 166 5. IANA Considerations 168 No IANA actions are required for this document. 170 6. Acknowledgements 172 This document was based on conversations among the authors, Jeffrey 173 Altman, Sam Hartman, Martin Rex and other members of the Kerberos 174 working group. 176 7. References 178 7.1 Normative References 180 [CLARIFICATIONS] 181 RFC-Editor: To be replaced by RFC number for draft-ietf- 182 krb-wg-kerberos-clarifications. Work in Progress. 184 [PKINIT] RFC-Editor: To be replaced by RFC number for draft-ietf- 185 cat-kerberos-pk-init. Work in Progress. 187 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 188 Requirement Levels", BCP 14, RFC 2119, March 1997. 190 [RFC2560] Myers, M., Ankney, R., Malpani, A., Galperin, S. and C. 191 Adams, "X.509 Internet Public Key Infrastructure Online 192 Certificate Status Protocol - OCSP", RFC 2560, June 1999. 194 [X690] ASN.1 encoding rules: Specification of Basic Encoding 195 Rules (BER), Canonical Encoding Rules (CER) and 196 Distinguished Encoding Rules (DER), ITU-T Recommendation 197 X.690 (1997) | ISO/IEC International Standard 8825-1:1998. 199 7.2 Informative References 201 [OCSP-PROFILE] 202 RFC-Editor: To be replaced by RFC number for draft-deacon- 203 lightweight-ocsp-profile. Work in Progress. 205 Authors' Addresses 207 Larry Zhu 208 Microsoft Corporation 209 One Microsoft Way 210 Redmond, WA 98052 211 US 213 Email: lzhu@microsoft.com 215 Karthik Jaganathan 216 Microsoft Corporation 217 One Microsoft Way 218 Redmond, WA 98052 219 US 221 Email: karthikj@microsoft.com 223 Nicolas Williams 224 Sun Microsystems 225 5300 Riata Trace Ct 226 Austin, TX 78727 227 US 229 Email: Nicolas.Williams@sun.com 231 Intellectual Property Statement 233 The IETF takes no position regarding the validity or scope of any 234 Intellectual Property Rights or other rights that might be claimed to 235 pertain to the implementation or use of the technology described in 236 this document or the extent to which any license under such rights 237 might or might not be available; nor does it represent that it has 238 made any independent effort to identify any such rights. 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