PKIX Working Group J. Schaad Internet-Draft Soaring Hawk Consulting Expires: April 25, 2006 M. Myers TraceRoute Security, Inc. October 22, 2005 Certificate Management over CMS (CMC) Transport Protocols draft-ietf-pkix-cmc-trans-04.txt 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 April 25, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document defines a number of transport mechanisms that are used to move CMC (Certificate Managment over CMS (Cryptographic Message Syntax)) messages. The transport mechanisms described in this document are: HTTP, file, mail and TCP. Schaad & Myers Expires April 25, 2006 [Page 1] Internet-Draft CMC: Transport Protocols October 2005 1. Overview This document defines a number of transport methods that are used to move CMC messages (defined in [CMC-STRUCT]). The transport mechanisms described in this document are: HTTP, file, mail and TCP. 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. File based protocol Enrollment messages and responses may be transferred between clients and servers using file system-based mechanisms, such as when enrollment is performed for an off-line client. When files are used to transport binary, BER-encoded Full Enrollment Request and Response messages, there MUST be only one instance of a request or response message in a single file. The following file type extensions SHOULD be used: +-------------------+----------------+ | Message Type | File Extension | +-------------------+----------------+ | Full PKI Request | .crq | | Full PKI Response | .crp | +-------------------+----------------+ 3. Mail based protocol MIME wrapping is defined for those environments that are MIME native. The basic mime wrapping in this section is taken from [SMIMEV2] and [SMIMEV3]. Simple enrollment requests are encoded using the "application/pkcs10" content type. A file name MUST be included either in a content type or a content disposition statement. The extension for the file MUST be ".p10". Simple enrollment response messages MUST be encoded as content-type "application/pkcs7-mime". An smime-type parameter MUST be on the content-type statement with a value of "certs-only." A file name with the ".p7c" extension MUST be specified as part of the content- type or content-disposition statement. Full enrollment request messages MUST be encoded as content-type "application/pkcs7-mime". The smime-type parameter MUST be included with a value of "CMC-enroll". A file name with the ".p7m" extension Schaad & Myers Expires April 25, 2006 [Page 2] Internet-Draft CMC: Transport Protocols October 2005 MUST be specified as part of the content-type or content-disposition statement. Full enrollment response messages MUST be encoded as content-type "application/pkcs7-mime". The smime-type parameter MUST be included with a value of "CMC-response." A file name with the ".p7m" extensions MUST be specified as part of the content-type or content- disposition statement. +-------------+------------------------+-------------+--------------+ | Item | MIME TYPE | File | SMIME-TYPE | | | | Extension | | +-------------+------------------------+-------------+--------------+ | simple | application/pkcs10 | .p10 | N/A | | request | | | | | full | applicaiton/pkcs7-mime | .p7m | CMC-request | | request | | | | | simple | application/pkcs7-mime | .p7c | certs-only | | response | | | | | full | application/pkcs7-mime | .p7m | CMC-response | | response | | | | +-------------+------------------------+-------------+--------------+ 4. HTTP/HTTPS based protocol HTTP messages are wrapped with by a mime object as specified above. 5. TCP based protocol When CMC messages are sent over a TCP-Based connection, no wrapping is required of the message. Messages are sent in their binary encoded form. The connection is closed by the server after generating a response for the client. (All CMC request messages from client to server generate a response message.) If a second set of messages from the client to the server is required to complete the transaction, the client generates a new TCP-Based connection for this purpose; it cannot reuse an existing one. Out of band setup can be used to keep a TCP-Based connection open for more than one message pair. A situation where this can occur is an RA talking to a CA over a specially setup TCP connection. Schaad & Myers Expires April 25, 2006 [Page 3] Internet-Draft CMC: Transport Protocols October 2005 6. Socket-Based Transport When enrollment messages and responses are sent over sockets, no wrapping is required. Messages MUST be sent in their binary, BER- encoded form. 7. Security Considerations Mechanisms for thwarting replay attacks may be required in particular implementations of this protocol depending on the operational environment. In cases where the CA maintains significant state information, replay attacks may be detectable without the inclusion of the optional nonce mechanisms. Implementers of this protocol need to carefully consider environmental conditions before choosing whether or not to implement the senderNonce and recipientNonce attributes described in section 5.6. Developers of state-constrained PKI clients are strongly encouraged to incorporate the use of these attributes. 8. Acknowledgments The authors and the Working Group are greatful for the participation of Xiaoui Lui and Jeff Weinstein in helping to author the original versions of this document. The authors would like to thank Brian LaMacchia for his work in developing and writing up many of the concepts presented in this document. The authors would also like to thank Alex Deacon and Barb Fox for their contributions. 9. References 9.1. Normative References [CMC-STRUCT] Schaad, J. and M. Myers, "Certificate Management Messages over CMS", Work in Progress , September 2005. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997. [SMIMEV3] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC 2633, June 1999. Schaad & Myers Expires April 25, 2006 [Page 4] Internet-Draft CMC: Transport Protocols October 2005 9.2. Informative References [SMIMEV2] Dusse, S., Hoffman, P., Ramsdell, B., Lundblade, L., and L. Repka, "S/MIME Version 2 Message Specification", RFC 2311, March 1998. Schaad & Myers Expires April 25, 2006 [Page 5] Internet-Draft CMC: Transport Protocols October 2005 Authors' Addresses Jim Schaad Soaring Hawk Consulting PO Box 675 Gold Bar, WA 98251 Phone: (425) 785-1031 Email: jimsch@exmsft.com Michael Myers TraceRoute Security, Inc. Email: myers@coastside.inc Schaad & Myers Expires April 25, 2006 [Page 6] Internet-Draft CMC: Transport Protocols October 2005 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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