[Mimedefang] multipart and filenames

Michael Fox news at mefox.org
Mon Oct 9 04:11:12 EDT 2017

I've got a couple of questions about the example filter handling of
composite MIME types:



According to RFC 2045, three composite message types exist:  "message",
"multipart", or "X-<Extension>"


Question 1:  Are all of these composite types handled by the
filter_multipart() function?  If not, how are the others handled?


These composite types include one or more discrete types, such as "text",
"image", "audio", etc.  My observation is that when a file is attached to a
message, it is added as a discrete type, such as "text", "image", "audio",
etc., which is handled by the filter() function.  So, my observation is that
the multipart MIME part never has an associated filename.  But the discrete
part within the multipart message may have an associated filename.


Question 2:  In the example file, filter_multipart calls the
filter_bad_filenames() function to check for bad filename extensions.   I
see the utility of this test in the filter() function.  But does a multipart
message ever really have an associated filename?  If so, can you help me
understand, perhaps with examples, when filter_multipart() would need to
check filenames?






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