Re: [openpgp] PGP/MIME, RFC 3156, Require empty boundary preamble lines

[Werner Koch <[e-mail]>]

On Mon, 20 Sep 2021 11:57, Kai Engert said:

> is this list an appropriate place to discuss PGP/MIME topics?

Sure.

> Thunderbird 78 had added a non-empty preamble line, which was removed
> by a mail transport agent, causing the signature verification to fail.

Welcome to the party.  Unfortunately there are many mail processing
services which don't care about the MIME standard and willy-nilly modify
messages or MIME header at any encapsulation level.  I have seen changed
content-encoding, new MIME header lines, or changed boundaries.  It is
quite common that signatures break as soon as they pass though some very
helpful tools which have been sold to companies to "secure" their
communication.

To be fair; things are better than 10 years ago and most signed mail
check out nicely (unless they got filtered out as spam as a few
corporate mail gateways do).

> Perhaps a future revision of RFC 3156 could state that preamble lines
> inside the signed payload MUST be empty - in the hope that no

I dont think that this is a good idea.  First it is not an PGP/MIME but
a general MIME issue, and second it solves only one of the problems with
broken mail processing software.


Shalom-Salam,

   Werner

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