Mailing List Archive

[Bug 1684] Malformed headers which exceed length spec willingly passed to remote servers
https://bugs.exim.org/show_bug.cgi?id=1684

Patrick Cernko <pcernko@mpi-klsb.mpg.de> changed:

What |Removed |Added
----------------------------------------------------------------------------
CC| |pcernko@mpi-klsb.mpg.de

--- Comment #15 from Patrick Cernko <pcernko@mpi-klsb.mpg.de> ---
I recently stumbled upon this change. I had a scenario, where my exim generated
a bounce based on a very long SMTP error message and failed to deliver it via
the local LMTP transport because the message *body* (generated by exim itself)
contained a line longer than message_linelength_limit. The result was a frozen
message. This caused a freeze_tell event but the resulting generated message
also had the message_linelength_limit issue (AFAIK). So in the end I had two
frozen messages in the queue but no message to postmaster about that. I only
stumbled upon the frozen messages by accident.
Unfortunately I removed the frozen message from the queue and was not able to
reproduce the behavior later to provide more a more detailed description.

I would like to request two things:
1. Please check all code sections generating (error) messages to not generate
lines longer than message_linelength_limit.
2. I cannot find any documentation about the changed default for
message_linelength_limit in the docs. Only thing I found was the documentation
about the new option with a different default as before. The sections seems to
be introduced in the 4.95 release but the release notes do not mention anything
about the new setting. As the setting definitely changes the behavior of
existing installations, it really should be worth mentioning.

Besides my requests, I really appreciate that new feature!

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[Bug 1684] Malformed headers which exceed length spec willingly passed to remote servers [ In reply to ]
https://bugs.exim.org/show_bug.cgi?id=1684

--- Comment #16 from Jeremy Harris <jgh146exb@wizmail.org> ---
It would help a lot if you could say what sort of SMTP error message.

The message_linelength_limit introduction was noted, with it's default
value, in the NewStuff file file for 4.95

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[Bug 1684] Malformed headers which exceed length spec willingly passed to remote servers [ In reply to ]
https://bugs.exim.org/show_bug.cgi?id=1684

--- Comment #17 from Patrick Cernko <pcernko@mpi-klsb.mpg.de> ---
Sorry, I only checked the Changelogs and missed that there is a separate
NewStuff file.

The SMTP error was a reject after DATA due to spamassassin results. The error
message included a longer report from spamassassin. In all my tries to
reproduce this error later the message was wrapped by the complaining server
and thus did not hit the line limit.

I extracted (and anonymized) the relevant log lines from the incident:

2023-02-16 10:36:25 1pSagd-006b9M-2u <= <> H=SENDER I=INTERFACE P=esmtp S=1747
for SRS_ENCODED_RECIPIENT
2023-02-16 10:42:05 1pSagd-006b9M-2u ** SRS_DECODED_RECIPIENT
<SRS_ENCODED_RECIPIENT> P=<> R=dnslookup T=remote_forwarded_smtp H=SENDER
I=INTERFACE X=CERTIFICATE_INFO: SMTP error from remote mail server after
pipelined end of data: 550-Rejected spam (score 5.7): Content analysis
details:\n550-* -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at\n550-*
https://www.dnswl.org/, no trust\n550-* [ANON_IP listed in
list.dnswl.org]\n550-* 0.8 BAYES_50 BODY: Bayes spam probability is 40 to
60%\n550-* [score: 0.5000]\n550-* 0.1 DKIM_SIGNED Message has a DKIM or
DK signature, not necessarily\n550-* valid\n550-* -0.1 DKIM_VALID Message
has at least one valid DKIM or DK signature\n550-* 0.5 MISSING_MID Missing
Message-Id: header\n550-* 1.4 MISSING_DATE Missing Date: header\n550-* 3.0
MPI_OWN_HEADDOM_WO_DKIM mail with one of our domains in From\n550-* header
but no DKIM signature
found\n550--------------------------------------------------------------------------------\n550
* 05.7 Total Score DT=2s
2023-02-16 10:42:05 1pSagd-006b9M-2u Frozen (delivery error message)
2023-02-16 10:46:45 1pSagd-006b9M-2u removed by root
2023-02-16 10:46:45 1pSagd-006b9M-2u Completed

2023-02-16 10:42:05 1pSamD-006e0P-1E <= <> R=1pSagd-006b9M-2u U=Debian-exim
P=local S=1533 for postmaster
2023-02-16 10:42:05 1pSamD-006e0P-1E ** POSTMASTER_ALIAS_ADDRESS
<POSTMASTER_ADDRESS> P=<> R=local_user T=dovecot: message has lines too long
for transport DT=0s
2023-02-16 10:42:05 1pSamD-006e0P-1E Frozen (delivery error message)
2023-02-16 10:47:02 1pSamD-006e0P-1E Message is frozen
2023-02-16 10:48:55 1pSamD-006e0P-1E removed by root
2023-02-16 10:48:55 1pSamD-006e0P-1E Completed

I have bounce_return_body enabled but I'm pretty sure, the body of the message
did not contain any longer lines as it was a test mail generated by me directly
via SMTP with telnet.

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[Bug 1684] Malformed headers which exceed length spec willingly passed to remote servers [ In reply to ]
https://bugs.exim.org/show_bug.cgi?id=1684

--- Comment #18 from Jeremy Harris <jgh146exb@wizmail.org> ---
Tracking as bug 2979.

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[Bug 1684] Malformed headers which exceed length spec willingly passed to remote servers [ In reply to ]
https://bugs.exim.org/show_bug.cgi?id=1684

Jeremy Harris <jgh146exb@wizmail.org> changed:

What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://bugs.exim.org/show_
| |bug.cgi?id=2979

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