[Pymilter] Malformed attachment problem

[Stuart D. Gathman]

I have been trying to improve the handling of malformed attachments by the
mime.py module.  Currently, a malformed attachment (missing boundaries, etc)
gets an exception, and is rejected as spam.  However, I keep getting cases
where someone forwards a message (with missing boundaries) as an rfc822
attachment.  I don't know whether the sender received the message garbled, and
read it with a tolerant email client, or their email client garbled it
while forwarding.  

This usually happens internally (where everyone uses OutHouse), so I added a
feature to pymilter so that a malformed attachment exception does not block
internal mail.

Here is my attempt to postphone parsing of rfc822 attachments until needed:

***************
*** 213,225 ****
              except Errors.HeaderParseError:
                  msg = self._class()
                  self._parsebody(msg, fp)
!           except Errors.BoundaryError:
!               part = container.get_payload(decode=True)
!               bl = re.compile(r'(?:\r\n|\r|\n){2}')
!               parthdrs, part = bl.split(part, 1)
!               msg = self.parsestr(parthdrs, headersonly=1)
!               msg.set_payload(part)
!           container.set_payload([msg])
          else:
              text = fp.read()
              if firstbodyline is not None:
--- 206,212 ----
              except Errors.HeaderParseError:
                  msg = self._class()
                  self._parsebody(msg, fp)
!             container.set_payload([msg])
          else:
              text = fp.read()
              if firstbodyline is not None:


I wanted malformed rfc822 attachments to produce an exception only
when the scan_rfc822 option is turned on.  Unfortunately, my test cases
indicate that with this change, malformed attachments are never
detected - even with scan_rfc822 on.

Does anyone have pointers to handling this problem with the email
package?  Suggestions?  I can make a case for always rejecting malformed
mail - but the whole point of the rfc822 attachment is to be able
to encapsulate mail, malformed or not.

-- 
	      Stuart D. Gathman <stuart at bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flamis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.