MIMEDefang update (was Re: Bypassing SMTP Content Protection )

From: David F. Skoll (dfsat_private)
Date: Thu Sep 12 2002 - 08:11:07 PDT

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    MIMEDefang (http://www.roaringpenguin.com/mimedefang/) is an SMTP
    filtering tool which in its default configuration is susceptible
    to this attack.
    
    MIMEDefang relies on the MIME::tools Perl parsing module.  This module
    correctly descends into "message/rfc822" entities and parses parts
    inside them, but it does not descend into "message/partial" entities.
    Therefore, even the default filename checks will not work with
    "message/partial" types.  I hope to have a patched version of MIME::tools
    soon.
    
    For the next MIMEDefang release, the default filter will be modified to drop
    message/partial parts.  Current users of MIMEDefang should add the
    following code to their filter and filter_multipart routines:
    
    # Block message/partial parts
    if (lc($type) eq "message/partial") {
        action_quarantine_entire_message();
        action_notify_administrator("Message quarantined because of message/partial type");
        return action_discard();
    }
    
    --
    David.
    



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