Blocking execution of non-exec things

[Ted Gould]

On Tue, 2010-01-12 at 10:45 -0800, Kees Cook wrote:
> On Tue, Jan 12, 2010 at 07:40:12PM +0100, Milan Bouchet-Valat wrote:
> > Le mardi 12 janvier 2010 à 10:19 -0800, Kees Cook a écrit :
> > > Hello!
> > > 
> > > As part of implementing the "Execute-Permission Bit Required" policy[1], I
> > > need to make changes to a few MIME handlers and to the nautilus .desktop
> > > file handler.
> > > 
> > > The main issue is that of the error message to produce, and I'm hoping to
> > > get some input for that from the Desktop team.
> > Maybe you already know about it, but here's the thread in
> > desktop-devel-list where it was decided how to phrase the dialog shown
> > when .desktop files don't have +x set:
> > http://www.mail-archive.com/desktop-devel-list@gnome.org/msg15440.html
> > 
> > There, the message was:
> > > The application launcher %s is not marked as trusted. If this
> > > application launchers source is unknown to you then it may be unsafe to
> > > launch.
> > 
> > Sure, it doesn't do what you want, since it provides that bad button
> > "Launch Anyway" (which was there for transition mainly). Anyway, that
> > might be an inspiration, you could just remove the button.
> 
> Right, this is about strengthening that message further.  I've already
> uploaded a patch to remove the other buttons.  :)

Maybe I'm confused, but it seems like we're not "executing" the .desktop
file, were executing what is on the "Exec" line of the desktop file.  It
would seem that what ever is first on that line should have +x, not
necessarily the desktop file itself.

That would lead to the question, is there a list of "wrapper" utilities?
It would seem that the easiest hack around that technique would be "nice
myvirus" as nice would be executable.  (and while I don't want viruses
stealing excess CPU, that doesn't solve the real problem).

Also, what would you want the text to say?  That seems pretty clear to
me.  "unlikely to be safe"?

		--Ted

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