A short time ago, at a computer terminal not so far away, I wrote:
> + http://mailtools.anomy.net/archives/anomy-list//16/13/ecbd140/00.msg.pgp
Sigh, okay non-signed:
We're using Anomy here to uvscan and/or defang things like .exe and .pif.
However, recent reports from campus indicate that Palyh samples aren't
getting scanned or defanged.
One sample I found had the following MIME headers on the attachment:
Note the two seperate specifications of a name for the file, and that they
provide two different extensions.
Not being very familiar with the intricacies of MIME headers, I don't know
what the difference is supposed to be, and/or why it can be specified in
two separate places like that.
As best I can tell, the disposition/filename is what most clients use, both
for creating and parsing messages. It's not clear if the type/name is used
by anything, or indeed if it's valid. However, some reports from users, as
well as news articles, talk about "*.pi" files; I'm not sure if those are
messages with a disposition/filename of ".pi", or if it's the same
mismatch-situation as above, except where the client is in fact using the
There also seems to be some confusion whether ".pi" files are executable in
the same fashion as ".pif" files are. For instance:
Although the file has a .pi or .pif extension, it is an .exe file. And
because Windows processes files according to their internal structure
rather than their extension, Windows runs the file as soon as the
recipient double-clicks on it.
This doesn't match any of my experience with Windows, and I have been
unable to get windows to launch a ".pi" file for me.
I have, however, observed Windows apparently parsing _some_ files and
loading them properly despite/regardless of their extension. For instance,
any Office file renamed to an unknown extension, or to no extension at all,
is loaded into the proper Office application. That is, renaming
"meeting.doc" to "meeting.blah" will still launch into Word. However, this
has only worked for Office documents so far; in particular, renaming
"notepad.exe" to "notepad.blah" will not run the executable, but instead
wil prompt for application to read the file.
So, I guess I'm wondering:
- Is the Content-Type/name field valid, how does it compare to the
Content-Disposition/filename field, and/or should we expect clients to
parse and honor it?
- Should Anomy parse the type/name field in addition to the
- Are ".pi" files executable/launchable in the same manner as ".pif"
- How/why is windows understanding an Office file without a valid Office
extension, and does this apply to any other file types? Ie, if it does
apply to other types, then file extension starts to appear become an
insufficient basis on which to filter attachments. Should Anomy perhaps
use /bin/file or the equivalent, and filter based on the file's magic
-- Will Day Those who would give up essential Liberty, to @rom.oit.gatech.edu purchase a little temporary Safety, deserve neither Georgia Tech / OIT Liberty nor Safety. UNIX System Programmer - Benjamin Franklin, Penn. Assembly, Nov. 11, 1755 -> Opinions expressed are mine alone and do not reflect OIT policy <-