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List:       spamassassin-devel
Subject:    [Bug 7073] Oddly-formed MIME-Version header prevents base64 decoding
From:       bugzilla-daemon () bugzilla ! spamassassin ! org
Date:       2014-08-14 23:14:51
Message-ID: bug-7073-26-uBzXELAj9u () https ! issues ! apache ! org/SpamAssassin/
[Download RAW message or body]

https://issues.apache.org/SpamAssassin/show_bug.cgi?id=7073

--- Comment #9 from Karsten Bräckelmann <guenther@rudersport.de> ---
(In reply to Dave Pifke from comment #6)
> >  From jpeterson@olxagmzmkt.com Wed Aug 13 13:47:10 2014
> >  >From dave  Wed Aug 13 13:47:10 2014

> This is indeed a raw, unharmed sample.  The relevant Exim configuration that
> wrote it is:
> 
> procmail_pipe:
>         driver = pipe
>         command = /usr/bin/procmail -d ${local_part}
>         user = ${local_part}
>         check_string = "From "
>         escape_string = ">From "

This seems to explain the weird first two lines. I am by no means an Exim
expert, but glancing docs for those check/escape string options tells:

Those together form a string match and replace command, performed on each line.

This particular substitution matches the common From_ escape: In mbox format, a
line beginning with "From " marks the start of a new message. Thus, such string
in the body of a message must be escaped, to differentiate it from the mbox
format begin-of-message marker.

In a pipe to the procmail command for delivery, From_ escaping is

(a) unnecessary, since procmail does the escaping if (and only if) the delivery
target is in mbox format (no need for other formats), and

(b) slightly harmful in this case: The check/escape string option does not
differentiate between message headers and body, thus invalidating the already
existing From_ line, forcing procmail to add one of its own.


So, again, that explains the weird first two lines. And it is entirely
unrelated to any other format breakage. It is in particular unrelated to the
broken MIME structure and headers which led to this bug report.

Herring. Red. But at least we know it's smelly fish, not spam...

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