gnome thumbnailers should have an apparmor profile

[Jamie Strandboge]

Binary package hint: gnome-control-center

Nautilus normally uses gnome-thumbnail-font, to provide font previews. Eg:
$ gconftool-2 -g /desktop/gnome/thumbnailers/application@x-font-ttf/enable
true
$ gconftool-2 -g /desktop/gnome/thumbnailers/application@x-font-ttf/command
gnome-thumbnail-font %u %o

If a flaw is discovered in a font library or Gnome and a user navigates to a directory that has a malicious font file, gnome-thumbnail-font could be used to execute arbitrary code, write out to files or leak information. Providing an apparmor profile for gnome-thumbnail-font would be a good step towards proactively protecting the user from this sort of attack.

The same can be said for other thumbnailers. Nautilus also uses totem-video-thumbnail and evince-thumbnailer (evince-thumbnailer has an apparmor profile already). For images, nautilus uses gdk-pixbuf routines via gnome-desktop, but these can be altered to use evince-thumbnailer by installing schema files for the various image mime-types and updating gnome-desktop to not fallback to gdk-pixbuf on thumbnail script error.

[Jamie Strandboge (jdstrand)]

Attached is a preliminary profile to achieve this. It was tested with various font files based on http://gfontview.sourceforge.net/features.html as well as with nautilus. It requires more testing before inclusion in Ubuntu. To try it out, copy it to /etc/apparmor.d/usr.bin.gnome-thumbnail-font and then perform:
$ sudo apparmor_parser -r /etc/apparmor.d/usr.bin.gnome-thumbnail-font

Feedback is welcome.

[Jamie Strandboge (jdstrand)]

Attached is a preliminary totem abstraction and totem-previewers profile for totem-video-thumbnailer and /usr/bin/totem-audio-preview. To use, put totem.abstraction in /etc/apparmor.d/abstractions/totem and usr.bin.totem-previewers in /etc/apparmor.d/usr.bin.totem-previewers. Then do:
$ sudo apparmor_parser -r /etc/apparmor.d/usr.bin.totem-previewers

It requires more testing before inclusion in Ubuntu, but was tested with ogg audio and flash video thumbnails via nautilus.

[dino99 (9d9)]

hi Jamie,
i'm ready to test but cant see the attached file into post #1

[Jamie Strandboge (jdstrand)]

@dino99: I updated the usr.bin.gnome-thumbnail-font profile by attaching a new profile to this bug in comment #5 (also seen on the right of this page).

[Simon Déziel (sdeziel)]

@Jamie, I've been running with your profile (from comment #5) on Precise since a long time and it works really well. It would be nice to have it shipped enabled by default in future releases. Thanks