dovecot - Sep 2013 - Passing info from mail process to mail_filter plugin script?

Hi, all,

The mail_filter plugin allows you to pass messages through an external
script/command on the way into and out of the Maildir/mbox/etc mail store.
With the recent/new version of the plugin, this seems to work correctly.

However, my mail-filter script (for filtering messages on the way from the
mail store through the IMAP process to a remote client) needs some extra info
from the IMAP mail process.  I'm having difficulty figuring out how this can
be accomplished.

Ideally, I'd like to pass another open file descriptor (opened in the IMAP
process) to the script, but I'm not sure if this is possible.  Opening the
file in the IMAP main.c fails, presumably due to file descriptor limits, but I
don't see where restrict_fd_limit() is called there.

My second choice for passing this info would be in an environment variable or
argument to the mail filter script.  Adding env_put() to the IMAP code
doesn't
seem to get the value passed to the script, presumably because the environment
is getting cleared, but again I'm not certain where the list of env vars to
keep is set here.

There may be another way to accomplish this that I'm not thinking of?

Any assistance would be appreciated.

Charles
-- 
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Charles Cazabon
GPL'ed software available at:               http://pyropus.ca/software/
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On 21.9.2013, at 20.32, Charles Cazabon <charlesc-dovecot at pyropus.ca>
wrote:
> The mail_filter plugin allows you to pass messages through an external
> script/command on the way into and out of the Maildir/mbox/etc mail store.
> With the recent/new version of the plugin, this seems to work correctly.
> 
> However, my mail-filter script (for filtering messages on the way from the
> mail store through the IMAP process to a remote client) needs some extra
info
> from the IMAP mail process.  I'm having difficulty figuring out how
this can
> be accomplished.
> 
> Ideally, I'd like to pass another open file descriptor (opened in the
IMAP
> process) to the script, but I'm not sure if this is possible.  Opening
the
> file in the IMAP main.c fails, presumably due to file descriptor limits,
but I
> don't see where restrict_fd_limit() is called there.
imap process communicates with the mail_filter process via UNIX socket. It would
be possible to pass a file descriptor, but it would need motifications to both
the mail-filter/[io]stream-ext-filter.c and to src/util/script.c to use
fd_send() and fd_recv().

Without modifications the only way to pass data is via the plugin { mail_filter
} parameters, such as the %u expanding to username in the example. If you want
some other parameters that don't exist in %variables (they get expanded
immediately when the imap process starts), you need to modify for example
mail-filter-plugin.c where it passes muser->args and muser->out_args to
[io]_stream_create_ext_filter().