[Mimedefang] Change subject according to string match in body

[Steffen Kaiser]

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On Tue, 19 Jan 2010, Johan Lundberg wrote:

Primary, follow the advice of Dave and move your check into filter().
During this phase the module variables (globally defined varables
in mimedefang-filter) are shared, hence, you can prepare the check in
filter_begin(), e.g. open log file, prepare the condition when to search
for the pattern, do the subject check etc, and end it in filter_end(),
e.g close the log file.

If you read INPUTMSG directly, you have to deal with MIME encoding etc,
hence, I would go the filter() route.

BTW: because multiple MIMEDefang processes may run simultaneously,
you might loose log info. You should use Syslog.

> sub filter_end {
> *snip* *snip*
>    # Search for "pattern" in the mail body
>    # and prepend subject with [See Me].
>    my $sender = $entity->head->get('From',0);

Well, there is $Sender, which is the envelope MAIL FROM, which probably 
differs from the header. BTW: There is probably no From header.

>    if ($sender =~ /example\@example\.com/) {

I guess, you want to check anchored regex:
     if ($sender =~ /\A(example\@example\.com|..)\z/) {

>        my $subject = $entity->head->get('Subject',0);

Already in $Subject

>        if ($subject =~ /pattern/i) {
>            print INFO "Subject hit: Subject changed!\n";
>            action_change_header('Subject', "[See Me]$subject");
>        } else {
>            my $body = $entity->bodyhandle;

I'm not sure, if this works with multipart MIME messages, at least 
you would need some checks.

>            my $IO = $body->open("r");
>            while (defined($_ = $IO->getline)) {
>                if (/pattern/i) {
>                    print INFO "Body hit: Subject changed!\n";
>                    print INFO "Body line: $_\n";
>                    action_change_header('Subject', "[See Me]$subject");
>                    last;
>                }


BTW: If you use SpamAssassin, you can create your own rule, score it with
"0.0" - so the SPAM score is not changed - and check the matched rules for 
your one.

Regards,

- -- 
Steffen Kaiser
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