Automatic display of images (was: Security advisory?)

[Reiner Steib]

On Fri, Jun 22 2007, Glenn Morris wrote:

> I think they call it a "denial of service" because it occurred in the
> VM mail reader (not part of Emacs, of course), when viewing a spam
> mail with a malformed image. So someone could email you an image that
> would crash Emacs. I don't know if gnus, rmail, or mh-e automatically
> display images; I suspect not.

Gnus does display images automatically.  But we have been through this
discussion before in February in the thread "Image mode"...

,----[ http://article.gmane.org/gmane.emacs.devel/66004 ]
| From: Lars Magne Ingebrigtsen <larsi <at> gnus.org>
| Subject: Re: Image mode
| Newsgroups: gmane.emacs.devel
| Date: 2007-02-06 10:53:50 GMT
| 
| Richard Stallman <rms <at> gnu.org> writes:
| 
| >     In contrast, if someone sends me a JPEG image in an email, Gnus
| >     will happily show it to me without asking (at least with the
| >     settings I'm using).  So where's the protection in that case?
| >
| > Should we consider that a bug in Gnus?
| > (I don't know what the answer is.)
| 
| Switching image display off in a mail reader is like switching it off
| in a web browser.  Does Firefox query the user before displaying an
| image?  "Warning!  The web page you're browsing contains an image!
| Image libraries are sometimes prone to buffer overflows!  Do you
| really wish to expose yourself to this danger!!1!?"
| 
| Warning users about something that's almost certainly not dangerous is
| a huge security risk in itself, because you're inuring the users to
| warnings.  The user will answer "Yeah, whatever" when being bothered
| with these things, and then when Emacs asks the user "Are you sure you
| wish to do an rm -rf?" (or whatever the genuinely dangerous thing it
| is), they won't bother to read the warning. 
`----

Richard replied:

,----
| From: Richard Stallman <rms <at> gnu.org>
| Subject: Re: Image mode
| Newsgroups: gmane.emacs.devel
| Date: 2007-02-06 23:16:17 GMT
| 
|     Switching image display off in a mail reader is like switching it off
|     in a web browser.  Does Firefox query the user before displaying an
|     image?  "Warning!  The web page you're browsing contains an image!
|     Image libraries are sometimes prone to buffer overflows!  Do you
|     really wish to expose yourself to this danger!!1!?"
| 
| If this argument is valid for Gnus, it seems just as valid for
| visiting a file directly with Emacs.
| 
| To the extent that image libraries have bugs, there will be some level
| of danger in viewing images with Emacs.  That danger will obtain
| regardless of whether the image files have expected image extensions.
| It doesn't go away just because the JPG is in a file called foo.jpg.
| 
| Lars' argument seems to show that we just have to live with it.
`----

Bye, Reiner.
-- 
       ,,,
      (o o)
---ooO-(_)-Ooo---  |  PGP key available  |  http://rsteib.home.pages.de/