PKIX Working Group J. Schaad
Internet-Draft Soaring Hawk Consulting
Expires: November 13, 2006 M. Myers
TraceRoute Security, Inc.
May 12, 2006
Certificate Management over CMS (CMC) Transport Protocols
draft-ietf-pkix-cmc-trans-05.txt
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Copyright (C) The Internet Society (2006).
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.
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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
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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.
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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.
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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.
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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
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