Re: [AMaViS-user] Just let permitted Attachements pass

Ekkehard,

> what I might have to do is that I change the Banned File
> checks so that I just let pass Mails with attachments
> that I know that can pass and can be checked successfully.
>
> It's just as a firewall policy deny all then permit selectively.

As far as $banned_filename_re or $banned_namepath_re
lists are concerned, the 'explicit permit with a default deny' logic
is supported as usual.

> Did anyone out there try this already? Is it easy to get around it?
> I'm just thinking about setting a different MIME Type.

If you don't have too many local users and you receive a good feedback,
it may be doable. I'm not sure about all the implications, could be
a pain for the senders and recipients.

> Second thing in this effort is what do I do if lets say an unpacker
> fails. I'd like to stop the delivery on that too.

See sub decompose_part(), turn an unsuccessful status from eval {...}
into adding an undecipherable attribute to the failed part:
$newpart_obj->attributes_add('U');
and then block mail on the presence of such attribute:

$banned_filename_re = new_RE(
qr'^UNDECIPHERABLE$', # is or contains any undecipherable components
...
);

I never tried it though.

It is likely you will encounter contents which look like some archive
or compressed format to file(1) utility, which later turns out not to be.
The decoders that routinely try some decoding but then report
it is not really their format, are the do_ascii and do_executable
(which attempts to unwrap self-extracting archives).

Mark


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