Timo Sirainen tss@iki.fi wrote:

On 21.9.2013, at 20.32, Charles Cazabon charlesc-dovecot@pyropus.ca wrote:

...

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.

[...] 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().

Thanks for the response, Timo.

Okay, given that this looks a little more complex than the other route, I decided to try your suggestion of adding a new % variable which I can supply in the mail_filter plugin configuration as a commandline argument to the filter script.

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().

I *think*, if I'm reading the code correctly, that it might be simpler in my particular case to modify the var_expand_table directly. The info I want to pass to the filter becomes available in the imap code shortly after login (actually immediately after client_add_input()), so unfortunately it's just after settings_var_expand() is called in src/imap/main.c:client_create_from_input().

I hacked in some code to change the table at that point (i.e. just before client_create_from_input() returns), but it seems the table has already been used to expand the vars by then, i.e. I'm just too late and my new variable isn't recognized/expanded.

Would a simple, ugly hack like calling settings_var_expand() a second time be sufficient to get my new % variable added here?

Charles

Charles Cazabon GPL'ed software available at: http://pyropus.ca/software/

On 25.9.2013, at 3.06, Charles Cazabon charlesc-dovecot@pyropus.ca wrote:

Timo Sirainen tss@iki.fi wrote:

...

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.

I hacked an additional %variable (I used %q) into a copy of mail-user.c:mail_user_var_expand_table () (and called this modified version instead of the original, in the same place it is normally called), and moved my data collection around in imap/main.c:settings_var_expand() so that my info was available at the time mail_user->var_expand_table is populated.

Better to not give a one character name, but only the long name so it won't conflict with any future Dovecot additions.

This appears to be working thus far. If I iterate over that table, my custom variable is present and has a correct key, value, and long_key before client_create() is called.

But when I put %q into the mail_filter config like so:

mail_plugins = $mail_plugins mail_filter

plugin { mail_filter = mail-filter %q foo %u mail_filter_out = mail-filter-out %u }

... and restart Dovecot, I find that the filter script is only being passed 2 arguments, the constant "foo" in the above and the username. The %q does not appear to be getting replaced; it's just skipped over. It's not even passing an empty string in its place.

Hmm. yeah, the empty string isn't there because mail-filter uses t_strsplit_spaces() instead of t_strsplit(). I suppose it should use t_strsplit().

Am I modifying the correct var_expand_table here? Is there any step I've missed in making the new variable get substituted properly? lib/var-expand.c doesn't appear to require anything else, but I may have missed something…

It looks like this should be correct. The plugin settings expansion i done by mail-user.c:mail_user_expand_plugins_envs().

The other possibility would be that you just modify mail-filter plugin and add the extra parameter without any %variable changes. Probably better since then you don't need to patch Dovecot core itself.