On Thursday November 6 2008 23:11:34 Murray S. Kucherawy wrote:
> Seems like either patching the filter to anticipate such rewrites, or just
> have everyone use "relaxed" (perhaps even default to it) for the header
> fields is appropriate.  However, even this doesn't handle rewrites that
> alter the actual content, such as domain name masquerading.

...nor does "relaxed" help when sendmail inserts a FWS where there was none
originally, like after a comma separating addresses in a To: header field
(or after a colon, as was already mentioned here). Seems like the To field
is subject to more threats than most other header fields - and since it is
pretty much an informative-only header field (addresses are propagated
out-of-band in the envelope from MSA to the final delivery, the To: has
no effect on mail delivery nor on DSN), I don't think it is a great loss
to just leave it out of the signature.

> The ultimate solution would be to have the filter able to plug into the
> MTA at a point after all of the rewriting is done.  We call this "output
> filtering", but we don't currently have it.

That would help. The other great achievement would be to let a milter
see the Received header field that is being generated by the MTA.

The absence of it makes some milters jump hoops to internally synthesize
this header field to supply the needed information for its operation
(e.g. for calling SpamAssassin from a milter). Also, not knowing the
exact final appearance of this header field, along with a creative
counting of header field index when inserting a new field by a milter,
makes it a mess when a signing milter is combined with some other
classical milter.

For bedtime reading:

http://archives.neohapsis.com/archives/postfix/2006-10/1698.html
http://archives.neohapsis.com/archives/postfix/2006-11/0467.html
http://archives.neohapsis.com/archives/postfix/2006-11/0505.html
http://archives.neohapsis.com/archives/postfix/2006-11/0509.html
http://archives.neohapsis.com/archives/postfix/2006-11/0516.html
http://archives.neohapsis.com/archives/postfix/2006-11/0519.html
http://archives.neohapsis.com/archives/postfix/2006-11/0565.html
http://archives.neohapsis.com/archives/postfix/2006-11/0568.html
http://archives.neohapsis.com/archives/postfix/2006-12/1299.html

  Mark

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