[Mimedefang] Interesting anti-HTML filter side-effect

[David F. Skoll]

On Sat, 20 Sep 2003, G. Roderick Singleton wrote:

> Care to post the rules? I for one am struggling to find a solution in a
> hurry.

The filter looks something like this (edited to protect the innocent/guilty).
Not all functions are included; you'll have to figure out how to implement
the missing stuff.  This (very complicated) filter_begin function sets
$HTMLOK to 1 if we'll accept HTML, or 0 otherwise.  Later on, in filter,
if we find a text/html part and $HTMLOK is 0, we bounce the message.

Note:  Believe it or not, this is a *simplified* version of the actual
filter. :-)

Regards,

David.

sub filter_begin {
    $ToRoaringPenguin = 0;   # Is it to someone @roaringpenguin.com?
    $ToMDList = 0;           # Is it to the MIMEDefang list?
    $ToCanitAnnounce = 0;    # Is it to the CanIt-Announce list?
    $ToAFS = 0;              # Is it for my sister's domain?

    # I never *send* mail as postmaster.  Therefore, postmaster should
    # never *receive* bounce messages.
    if ($Sender eq "<>") {
	foreach $recip (@Recipients) {
	    if ($recip =~ /^<?postmaster\@/i) {
		action_bounce("Mail from <> not accepted to $recip");
		return;
	    }
	}
    }

    foreach $recip (@Recipients) {
	# to_rp() returns true if arg is to a roaringpenguin.com address
	if (to_rp($recip)) {
	    $ToRoaringPenguin = 1;
	}
	if ($recip =~ /artandframingsolutions/i) {
	    # For my sister
	    $ToAFS = 1;
	}
	if ($recip =~ /mimedefang\@lists\.roaringpenguin\.com/i or
	    $recip =~ /canit\@lists\.roaringpenguin\.com/i) {
            # For the MIMEDefang or CanIt mailing list
	    $ToMDList = 1;
	}
	if ($recip =~ /canit-announce\@lists\.roaringpenguin\.com/i) {
            # For the CanIt-Announce mailing list
	    $ToCanitAnnounce = 1;
	}
    }

    # Only David can post to CanIt-Announce, and he has to do it from
    # a specific machine.
    if ($ToCanitAnnounce) {
	if ($Sender ne '<dfs at roaringpenguin.com>' or
	    $RelayAddr ne "xxx.yyy.zzz.aaa") {
	    action_bounce("Not allowed to post to canit-announce");
	    return;
	}
    }

    # Certain senders are permitted to send HTML, no matter what.
    if ($Sender eq '<xxxxxx1 at dfsdfsd.com.sg>' || $Sender =~ /list1/ || $Sender =~ /xxlist2/ || $Sender =~ /xlist3/ || $Sender =~ /xlist4/ || $Sender =~ /\@xlist5xx/) {
	$HTMLOK = 1;
    } else {
	$HTMLOK = 0;
    }

    $OnlyToMySister = 1;
    foreach $recip (@Recipients) {
	if ($recip =~ /^<?.*\@artandframingsolutions\.com>?$/) {
	    next;
	}
	$OnlyToMySister = 0;
	last;
    }

    # Accept HTML if we appear in the To: field
    if (open(HDRS, "<./HEADERS")) {
        while(<HDRS>) {
            if (/^To:.*\@.*roaringpenguin\.com/i) {
                $HTMLOK = 1;
            }
            if (/^Cc:.*\@.*roaringpenguin\.com/i) {
                $HTMLOK = 1;
            }
            if (/^To:.*\@.*canit\.ca/i) {
                $HTMLOK = 1;
            }
            if (/^Cc:.*\@.*canit\.ca/i) {
                $HTMLOK = 1;
            }
            if (/^To:.*\@artandframingsolutions\.com/i) {
                $HTMLOK = 1;
            }
            if (/^Cc:.*\@artandframingsolutions\.com/i) {
                $HTMLOK = 1;
            }
        }
        close(HDRS);
    }

    if ($OnlyToMySister) {
	$HTMLOK = 1;
    }
}