Subject: [Asrg] Body signature subgroup and the forwarding project

From: John Levine <[email-masked]>
Date: 27 Jul 2005 02:38:26 -0000

Over on the lists where people are working on DKIM and similar
signature schemes, there's a lot of discussion of message
canonicalization for signature hashes.  That is, the signature
involves a hash of the message, but before making the hash, the
message is cleaned up to make it more likely that the signature will
still verify after the message passes through a few intermediate mail
systems, while not letting a bad guy change the message into something
substantively different.

Lots of people have strong opinions about various canonicalization
schemes, but we have precious little data on how messages actually
change when passing through MTAs.  So I thought a little research
might be in order.  My plan is to get a bunch of people with different
MTAs to set up forwarding addresses that forward back to addresses
here so that I can send them a message, it goes through their MTA and
returns, and I can now see how the message changed.  My MTA is qmail
which carefully avoids doing anything to incoming messages other than
prefixing a Received: header, so it's not hard to isolate the effects
of the remote MTA.

I've set up a new subgroup called bodysig.  To subscribe to its list,
send "subscribe bodysig" to [email-masked].  (It's a closed list,
so if I don't already know who you are, please send me a two sentence
message introducing yourself.)  I already have some offers of forwarders,
but I'm looking for more, particularly once I know what MTAs I already
have covered.

At this point I haven't figured out what the mechanism for running
messages through the forwarding gauntlet should be.  Suggestions
welcome.  Paste them into a web form?  Mail them in as an attachment?

Regards,
John Levine, [email-masked], Taughannock Networks, Trumansburg NY
http://www.taugh.com

_______________________________________________
Asrg mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/asrg

---

From: "william(at)elan.net" <[email-masked]>
Date: Tue, 26 Jul 2005 19:53:32 -0700 (PDT)

Before you begin testing, the question that should be asked is  -
  What is a forwarder?

Depending on if you classify automated email redirection systems such
as mail lists as forwarders, your results on survivability of the messages 
and effectiveness of different canonicalization methods would be very
different. In the same way, only classifying behavior and transformations 
by MTAs the message passed though may not be appropriate.

Additionally the results would also depend on what kind of email messages
are tested against, for example the messages with certain types of MIME 
content (text vs binary) could be interpreted by intermediate systems in 
different ways if they are mime-aware.

-- 
William Leibzon
Elan Networks
[email-masked]