On 27/07/2024 21:26, Meinhard Schneider via dovecot wrote:
Hello,
I have now adjusted the values accordingly:
root@lnxmail01:~# doveconf | grep -A 13 ^plugin
plugin {
sieve = file:~/sieve;active=~/.dovecot.sieve
sieve_execute_exec_timeout = 60s
sieve_extensions = +vnd.dovecot.filter +spamtest +spamtestplus
sieve_filter_bin_dir = /usr/lib/dovecot/sieve-filter
sieve_filter_exec_timeout = 60s
sieve_filter_socket_dir = sieve-filter
sieve_global = /usr/lib/dovecot/sieve-global
sieve_pipe_exec_timeout = 60s
sieve_plugins = sieve_extprograms
sieve_spamtest_max_value = 5
sieve_spamtest_status_header = X-Spam-Level
sieve_spamtest_status_type = strlen
}
I will observe whether the problems continue to occur.
I guess that the possibility of problems happening is still there since
whatever timeout you put, it could be exceeded. It doesn't seem like a
robust way of filtering.
Nevertheless, I would like to know if there is a way to prevent the
e-mails from being completely discarded if an error occurs.
I would expect Dovecot and Pigeonhole not to discard emails in the case
of errors. My expectation would be that if the script returns an error
code then the email will be kept by default. Do you have any evidence of
discarding email in the case of errors, where the scripts is returning
an error to dovecot but it is ignored?
As for discarding emails when the script times out, I believe you are
right about that. On the face of it it seems the wrong thing to do but I
guess there may be an explanation that I don't know as to why it works
that way.
The program /usr/lib/dovecot/sieve-filter/spamc-filter.sh is executed
because there is an include in the file .dovecot.sieve:
include :global “spamc”;
This is sufficient to start the filter “spamc-filter.sh” (I got this
from a guide on the Internet, but I can't find the link to it now).
My understanding is that this will include another sieve script called
"spamc", not directly call an external comamnd.
The problem is that only spamc is started in the script and STDIN and
STDOUT are connected to dovecot-lda. It would be easy to abort the
call of spamc after X seconds (man 'timeout(1)'). But then the input
provided by dovecot-lda and piped into spamc would be lost. You would
therefore have to cache all input in the script that comes via STDIN
in a file. If spamc is aborted, the script would have to recognize
this and output the contents of this file again via STDOUT. spamc must
be called using 'timeout' and the timeout used must be less than what
was set for sieve_filter_exec_timeout. This would then save the mail
from /dev/null.
Unfortunately, I currently see no other way to solve this problem.
Or does anyone have another idea how to tackle this issue?
Maybe you could work out how to return an error code from the script
after a timeout (before the dovecot timeout kicks in and kills it). I'm
not convinced you'd need to worry about STDIN and STDOUT. You could
check this easily by having a test script which returns a non zero value
(e.g. exit 1).
John
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