IETF S. Farrell Internet-Draft Trinity College Dublin Intended status: Informational December 21, 2007 Expires: June 23, 2008 Other Certificates Extension draft-farrell-pkix-other-certs-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 June 23, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract Some applications using public key certificates can benefit from a way to link together a set of certificates belonging to the same end entity. This memo defines a certificate extension that supports such linkage. Farrell Expires June 23, 2008 [Page 1] Internet-Draft Abbreviated Title December 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. A Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Other Certificates Extension . . . . . . . . . . . . . . . . . 4 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7.1. Normative References . . . . . . . . . . . . . . . . . . . 4 7.2. Informative References . . . . . . . . . . . . . . . . . . 5 Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . . . 6 Farrell Expires June 23, 2008 [Page 2] Internet-Draft Abbreviated Title December 2007 1. Introduction RFC 3280 [RFC3280] defines a profile for the use of public key certificates for Internet applications. Some applications may require a way to link together a set of certificates belonging to the same end entity so this memo defines a new public key certificate extension that supports such linkage. Other than asserting that the set of certificates belong to the same end entity, the semantics of the actual linkage of certifcates is not defined here, that is a matter for application developers and the operators of certification authorities (CAs). In particular we do not define how a CA can validate that the same end entity is the holder of the various private keys, nor how any application should make use of this information. This memo simply defines the relevant syntax. 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 RFC 2119 [RFC2119]. 2. A Use Case Public key certificates expire, typically about a year after they are created. Some applications might need to know that the same entity is the subject of this certificate and a previously used certificate. For example, if a web server certificate expires, it could be useful for a web browser to know that the server currently presenting a certificate in a TLS [RFC4346] handshake represents the same web server that previously presented a certificate. This could be used for example to allow the browser to automatically fill in form fields for the server in question, even if the server certificate has been replaced. While the same effect can be achieved based on the use of the same issuer and subject fields in a certificate there could be security issues involved in such comparisons, e.g. if the subject name includes a DNS name and the ownership of that DNS domain has changed. The use of the new extension provides a way for the CA to signal to the application that the same end entity is involved, regardless of name changes. The new extension could also allow the web site operator to more easily change CA when renewing its certificate. Farrell Expires June 23, 2008 [Page 3] Internet-Draft Abbreviated Title December 2007 3. Other Certificates Extension This section defines the syntax for the other certificates extension. The new extension is simply a list of other issuer/serial number pairs from the linked certificates. The IssuerAndSerialNumber construct is taken from CMS [RFC3852]. When this extension is present the CA is asserting that the same end entity is the subject of the relevant certificates. Mechanisms for how this assertion is validated by the CA or used by consumers of the certificate are out of scope of this memo. This extension MUST NOT be marked critical. id-ce-otherCerts OBJECT IDENTIFIER ::== { id-ce XXX } OtherCertificates ::= SEQUENCE OF IssuerAndSerialNumber 4. Acknowledgements The use case motivating this was contributed to the W3C web security context (WSC) working group by Tyler Close. See http://www.w3.org/2006/WSC/wiki/SafeWebFormEditor for details. 5. IANA Considerations This memo includes no request to IANA. 6. Security Considerations TBD. Some warnings for CAs and applications needed. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3280, April 2002. Farrell Expires June 23, 2008 [Page 4] Internet-Draft Abbreviated Title December 2007 [RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3852, July 2004. 7.2. Informative References [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. Appendix A. ASN.1 Module TBD Author's Address Stephen Farrell Trinity College Dublin Department of Computer Science Trinity College Dublin, 2 Ireand Phone: +353-1-896-1761 Email: stephen.farrell@cs.tcd.ie Farrell Expires June 23, 2008 [Page 5] Internet-Draft Abbreviated Title December 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Farrell Expires June 23, 2008 [Page 6]