PKIX Working Group M. Myers Internet Draft VeriSign Document: draft-ietf-pkix-cmc-trans-00.txt X. Liu February 2001 Cisco Expires: July 2001 J. Schaad Soaring Hawk Consulting J. Weinstein CMC Transport Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 . 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. Comments or suggestions for improvement may be made on the "ietf- pkix" mailing list, or directly to the author. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. Abstract This document defines a number of transport mechanisms that are used to move [CMC] messages. 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 [RFC 2119]. 1. Overview 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 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. MIME TYPE File Extension SMIME-TYPE application/pkcs10 .p10 N/A (simple PKI request) application/pkcs7-mime .p7m CMC-request (full PKI request) application/pkcs7-mime .p7c certs-only (simple PKI response) application/pkcs7-mime .p7m CMC-response (full PKI response) 4. HTTP/HTTPS based protocol HTTP messages are wrapped with by a mime object as specified above. 5. TCP based protocol When is the connection closed? How is this represented? While this section is called TCP-Based and the messages are called TCP-message's, the same protocol can be used over any reliable, connection oriented transport protocol (e.g. SNA, DECnet, etc.). This protocol is suitable for cases where an end entity (or an RA) initiates a transaction and can poll to pick up the results. The length of the flags field for this version is 1 octet. The LSB is used to indicate a connection close; all other bits in the flags octet MUST be ignored by receivers, and MUST be set to zero by senders. By default connections are kept open after the receipt of a response. Either party (client or server) MAY set the connection close bit at any time. If the connection close bit is set on a request, then the server MUST set the bit in the response and close the connection after sending the response. If the bit is set on a response from the server, the client MUST NOT send any further requests on that connection. Applications MAY decide to close an idle connection (one on which no response is outstanding) after some time-out. Because of the problem where a client sends a request and the server closes the connection while the request is still in flight, clients SHOULD automatically retry a request for which no part of the response could be read due to a connection close or reset. If the connection is kept open, it MUST only be used for subsequent request/response transactions started by the client - the server MUST NOT use it to send requests to the client. Different transactions may be freely interwoven on the same connection. E.g. a CR/CP need not immediately be followed by the Confirm, but may be followed by any other request from a different transaction. 7.3 Socket-Based Transport When enrollment messages and responses are sent over sockets, no wrapping is required. Messages SHOULD be sent in their binary, BER- encoded form. 9. 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. 10. Acknowledgments 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. 11. References [CMS] Housley, R., "Cryptographic Message Syntax", RFC 2630, June 1999. [CRMF] Myers, M., Adams, C., Solo, D. and D. Kemp, "Internet X.509 Certificate Request Message Format", RFC 2511, March 1999. [DH] B. Kaliski, "PKCS 3: Diffie-Hellman Key Agreement v1.4" [DH-POP] H. Prafullchandra, J. Schaad, "Diffie-Hellman Proof-of- Possession Algorithms", Work in Progress. [HMAC] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed- Hashing for Message Authentication", RFC 2104, February 1997. [PKCS1] Kaliski, B., "PKCS #1: RSA Encryption, Version 1.5", RFC 2313, March 1998. [PKCS7] Kaliski, B., "PKCS #7: Cryptographic Message Syntax v1.5", RFC 2315, October 1997. [PKCS8] RSA Laboratories, "PKCS#8: Private-Key Information Syntax Standard, Version 1.2", November 1, 1993. [PKCS10] Kaliski, B., "PKCS #10: Certification Request Syntax v1.5", RFC 2314, October 1997. [PKIXCERT] Housley, R., Ford, W., Polk, W. and D. Solo "Internet X.509 Public Key Infrastructure Certificate and CRL Profile", RFC 2459, January 1999. [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [SMIMEV2] Dusse, S., Hoffman, P., Ramsdell, B., Lundblade, L. and L. Repka, "S/MIME Version 2 Message Specification", RFC 2311, March 1998. [SMIMEV3] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC 2633, June 1999. [X942] Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC 2631, June 1999. 12. Authors' Addresses Michael Myers TraceRoute Security, Inc. EMail: firstname.lastname@example.org Xiaoyi Liu Cisco Systems 170 West Tasman Drive San Jose, CA 95134 Phone: (480) 526-7430 EMail: email@example.com Jim Schaad Soaring Hawk Consulting EMail: firstname.lastname@example.org Jeff Weinstein EMail: email@example.com Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. 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