Message Tracking Model and Requirements
RFC 3888
Document | Type | RFC - Informational (September 2004) | |
---|---|---|---|
Author | Tony Hansen | ||
Last updated | 2015-10-14 | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Formats | |||
Additional resources | Mailing list discussion | ||
IESG | Responsible AD | Scott Hollenbeck | |
Send notices to | (None) |
RFC 3888
IESG state changed to Approved-announcement sentquot; model requires active enabling to indicate that some form of tracking is to be performed. The tracking information can be sent back immediately (as a form of telemetry) or sent to a 3rd party for later retrieval. Hansen Informational [Page 5] RFC 3888 Message Tracking Model and Requirements September 2004 5.2.2. Passive Request Tracking Information Forms of passive tracking information that could potentially be requested are as follows. Note that mechanisms already exist for requesting the information marked with a (+). The references for such mechanisms are listed at the end of each such entry. ** send a DSN of a message arriving at an intermediate MTA ** (+) send a DSN of a message being rejected while at an intermediate MTA [RFC-DSN] ** (+) send a DSN of a message leaving an intermediate MTA and going to another MTA [RFC-DELIVER-BY] ** send a DSN of a message arriving at a final MTA ** (+) send a DSN of a message being rejected while at a final MTA [RFC-DSN] ** (+) send a DSN of a message being delivered to a user's message store [RFC-DSN] ** (+) send a DSN of a message being delivered to a foreign MTA [RFC-DSN] ** (+) send an MDN of a message being read by an end user [RFC-MDN] 5.3. Active Request Model The "active request" model requires an active query by a user's user agent to the MSA, intermediate MTAs and final MTA, or to a third party, to find the message's status as known by that MTA. Active request will work with either passive enabling or active enabling. 5.3.1. Server Chaining vs. Server Referrals When a tracking server has been asked for tracking information, and the message has been passed on to another MTA of which this tracking server has no tracking knowledge, there are two modelling choices: ** the first tracking server will contact the next tracking server to query for status and pass back the combined status (server chaining), or ** the first tracking server will return the address of the next MTA and the tracking client has the responsibility of contacting the next tracking server (server referrals). Hansen Informational [Page 6] RFC 3888 Message Tracking Model and Requirements September 2004 5.3.2. Active Request Tracking Information Forms of active tracking information that could potentially be requested are as follows. (Note that no mechanisms currently exist for requesting such information.) ** the message has been queued for later delivery ** the message was delivered locally ** the message was delivered to another MTA, ** the message was delivered to a foreign MTA ** ask a different tracking server, ** I know but can't tell you, ** I don't know. 5.4. Combining DSN and MDN Information with Message Tracking Information The information that would be retrieved by message tracking and the information that is returned for DSN and MDN requests all attempt to answer the question of "what happened to message XX"? The information provided by each is complimentary in nature, but similar. A tracking user agent could use all three possible information sources to present a total view of the status of a message. Both DSN and MDN notifications utilize the formats defined by RFC 3462 [RFC-REPORT]. This suggests that the information returned by message tracking solutions should also be similar. 6. Security Considerations 6.1. Security Considerations Summary Security vulnerabilities are detailed in [RFC-MTRK-ESMTP], [RFC- MTRK-TSN] and [RFC-MTRK-MTQP]. These considerations include: ** vulnerability to snooping or replay attacks when using unencrypted sessions ** a dependency on the randomness of the per-message secret ** reliance on TLS Hansen Informational [Page 7] RFC 3888 Message Tracking Model and Requirements September 2004 ** man-in-the-middle attacks ** reliance on the server maintaining the security level when it performs chaining ** denial of service ** confidentiality concerns ** forgery by malicious servers 6.2. Message Identification and Authentication This is a security model for message identification and authentication that could be deployed. (There may be others.) A Tracking User Agent must prove that they are permitted to request tracking information about a message. Every [RFC-822]-compliant message is supposed to contain a Message-Id header. One possible mechanism is for the originator to calculate a one-way hash A from the message ID + time stamp + a per-user secret. The user then calculates another one-way hash B to be the hash of A. The user includes B in the submitted message, and retains A. Later, when the user makes a message tracking request to the messaging system or tracking entity, it submits A in the tracking request. The entity receiving the tracking request then uses A to calculate B, since it was already provided B, verifying that the requestor is authentic. In summary, A = H(message ID + time stamp + secret) B = H(A) Another possible mechanism for A is to ignore the message ID and time stamp and just use a one-way hash from a large (>128 bits) random number. B would be calculated as before. In summary, A = H(large-random-number) B = H(A) This is similar in technique to the methods used for One-Time Passwords [RFC-OTP]. The success of these techniques is dependent on the randomness of the per-user secret or the large random number, which can be incredibly difficult in some environments. Hansen Informational [Page 8] RFC 3888 Message Tracking Model and Requirements September 2004 If the originator of a message were to delegate his or her tracking request to a third party by sending it A, this would be vulnerable to snooping over unencrypted sessions. The user can decide on a message-by-message basis if this risk is acceptable. 7. Informational References [RFC-822] Crocker, D., "Standard for the format of ARPA Internet text messages", STD 11, RFC 822, August 1982. [RFC-DELIVER-BY] Newman, D., "Deliver By SMTP Service Extension", RFC 2852, June 2000. [RFC-DSN] Moore, K., and G. Vaudreuil, "An Extensible Message Format for Delivery Status Notifications", RFC 3464, January 2003. [RFC-ESMTP-DSN] Moore, K., "Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs)", RFC 3461, January 2003. [RFC-KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC-MDN] Hansen, T. and G. Vaudreuil, Eds., "Message Disposition Notifications", RFC 3798, May 2004. [RFC-OTP] Haller, N., Metz, C., Nesser, P. and M. Straw, "A One-Time Password System", STD 61, RFC 2289, February 1998. [RFC-REPORT] Vaudreuil, G., "The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages", RFC 3462, January 2003. [RFC-MTRK-ESMTP] Allman, E. and T. Hansen, "SMTP Service Extension for Message Tracking", RFC 3885, September 2004. [RFC-MTRK-TSN] Allman, E., "The Message/Tracking-Status MIME Extension", RFC 3886, September 2004. [RFC-MTRK-MTQP] Hansen, T., "Message Tracking Query Protocol", RFC 3887, September 2004. Hansen Informational [Page 9] RFC 3888 Message Tracking Model and Requirements September 2004 8. Acknowledgements This document is the product of input from many people and many sources, including all of the members of the Message Tracking Working Group: Philip Hazel, Alexey Melnikov, Lyndon Nerenberg, Chris Newman, and Gregory Neil Shapiro. It owes much to earlier work by Gordon Jones, Bruce Ernst, and Greg Vaudreuil. In particular, I'd like to also thank Ken Lin for his considerable contributions to the early versions of the document. 9. Author's Address Tony Hansen AT&T Laboratories Middletown, NJ 07748 USA Phone: +1.732.420.8934 EMail: tony+msgtrk@maillennium.att.com Hansen Informational [Page 10] RFC 3888 Message Tracking Model and Requirements September 2004 10. Full Copyright Statement Copyright (C) The Internet Society (2004). 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/S HE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Hansen Informational [Page 11]