Network Working Group C. Newman Internet-Draft Sun Microsystems Expires: February 16, 2004 August 18, 2003 ESMTP and LMTP Transmission Types Registration draft-newman-esmtpsa-01.txt 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. This Internet-Draft will expire on February 16, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This registers seven new mail transmission types (ESMTPA, ESMTPS, ESMTPSA, LMTP, LMTPA, LMTPS, LMTPSA) for use in the "with" clause of a Received header in an Internet message. 1. IANA Considerations As directed by SMTP [2], IANA maintains a registry [7] of "WITH protocol types" for use in the "with" clause of the Received header in an Internet message. This registry presently includes SMTP [6], and ESMTP [2]. This specification updates the registry as follows: o The new keyword "ESMTPA" indicates the use of ESMTP when the SMTP AUTH [3] extension is also used and authentication is successfully Newman Expires February 16, 2004 [Page 1] Internet-Draft ESMTP and LMTP Transmission Types Registration August 2003 achieved. o The new keyword "ESMTPS" indicates the use of ESMTP when STARTTLS [1] is also successfully negotiated to provide a strong transport encryption layer. o The new keyword "ESMTPSA" indicates the use of ESMTP when both STARTTLS and SMTP AUTH are successfully negotiated (the combination of ESMTPS and ESMTPA). o The new keyword "LMTP" indicates the use of LMTP [4]. o The new keyword "LMTPA" indicates the use of LMTP when the SMTP AUTH extension is also used and authentication is successfully achieved. o The new keyword "LMTPS" indicates the use of LMTP when STARTTLS is also successfully negotiated to provide a strong transport encryption layer. o The new keyword "LMTPSA" indicates the use of LMTP when both STARTTLS and SMTP AUTH are successfully negotiated (the combination of LSMTPS and LSMTPA). o The references for the ESMTP and SMTP entries in the registry should be updated to the latest specification [2] since both RFC 821 and RFC 1869 are obsoleted by RFC 2821. 2. Implementation Experience The ESMTPA, ESMTPS and ESMTPSA keywords have been implemented in deployed email server software for several years and no problems have been reported with their use. 3. Security Considerations Use of these additional keywords provides trace information to indicate when various high-level security framing protocols are used for hop-to-hop transport of email without exposing details of the specifics of the security mechanism. This trace information provides an informal way to track the deployment of these mechanisms on the Internet and can assist after-the-fact diagnosis of email abuse. These keywords are not normally protected in transport which means they can be modified by an active attacker. They also do not indicate the specifics of the mechanism used, and therefore do not provide any real-world security assurance. As they are both cryptic Newman Expires February 16, 2004 [Page 2] Internet-Draft ESMTP and LMTP Transmission Types Registration August 2003 and hidden in trace headers used primarily to diagnose email problems, it is not expected they will mislead end users with a false sense of security. Information with a higher degree of reliability can be obtained by correlating the Received headers with the logs of the various Mail Transfer Agents through which the message passed. The trace information provided by these keywords and other parts of the Received header provide a significant benefit when doing after-the-fact diagnosis of email abuse or problems. Unfortunately, some people in a misguided attempt to hide information about their internal servers will strip Received headers of useful information and reduce their ability to correct security abuses after they happen. The result of such misguided efforts is usually a reduction of the overall security of the systems. Normative References [1] Hoffman, P., "SMTP Service Extension for Secure SMTP over Transport Layer Security", RFC 3207, February 2002. [2] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April 2001. [3] Myers, J., "SMTP Service Extension for Authentication", RFC 2554, March 1999. [4] Myers, J., "Local Mail Transfer Protocol", RFC 2033, October 1996. Informative References [5] Klensin, J., Freed, N., Rose, M., Stefferud, E. and D. Crocker, "SMTP Service Extensions", STD 10, RFC 1869, November 1995. [6] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, August 1982. URIs [7] Newman Expires February 16, 2004 [Page 3] Internet-Draft ESMTP and LMTP Transmission Types Registration August 2003 Author's Address Chris Newman Sun Microsystems 1050 Lakes Drive West Covina, CA 91790 US EMail: chris.newman@sun.com Newman Expires February 16, 2004 [Page 4] Internet-Draft ESMTP and LMTP Transmission Types Registration August 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Newman Expires February 16, 2004 [Page 5] Internet-Draft ESMTP and LMTP Transmission Types Registration August 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Newman Expires February 16, 2004 [Page 6]