Exploit-DB #40943
Description: Google Chrome (Fedora 25 / Ubuntu 16.04) - 'tracker-extract' / 'gnome-video-thumbnailer' + 'totem' Drive-By Download
Type: local
Platform: linux
Date: 2016-12-13
Author: Chris Evans

Exploit:
Source: https://scarybeastsecurity.blogspot.com/2016/12/redux-compromising-linux-using-snes.html

## Overview  

Full reliable 0day drive-by exploit against Fedora 25 + Google Chrome, by breaking out of Super Nintendo Entertainment System emulation via cascading side effects from a subtle and interesting emulation error. 

I had a lot of fun compromising the Linux desktop using 6502 opcodes on the original Nintendo NES (https://scarybeastsecurity.blogspot.com/2016/11/0day-exploit-compromising-linux-desktop.html). Would it be possible to have even more fun? Why, yes it would! My previous NES related exploit suffered from multiple fun-limiting issues:

- Although it was a genuine 0day exploit, it only affected very old Linux distributions. Something affecting bang up to date Linux installs would generate greater lulz.
- The vulnerability that was abused -- a total lack of bounds checking on memory bank mapping -- was somewhat obvious. More fun can often be had with vulnerabilities that are slightly more subtle.
- The lack of “super”! The Super Nintendo Entertainment System (SNES) is even more iconic than the original NES. Regarding its 1990 release, Wikipedia notes (https://en.wikipedia.org/wiki/Super_Nintendo_Entertainment_System) "the resulting social disturbance led the Japanese government to ask video game manufacturers to schedule future console releases on weekends". So we need more Super.

Resolving all the above, I present here a full, working, reliable, 0day exploit for current Linux distributions (Ubuntu 16.04 LTS and Fedora 25). It’s a full drive-by download in the context of Fedora. It abuses cascading subtle side effects of an emulation misstep that at first appears extremely difficult to exploit but ends up presenting beautiful and 100% reliable exploitation possibilities.

You’ve likely guessed it by now, but the Linux gstreamer media playback framework supports playback of SNES music files by…. emulating the SNES CPU and audio processor, courtesy of Game Music Emu (http://www.slack.net/~ant/libs/audio.html). How cool is that?

- - - 

## Demo and impact
Today, the demos are videos instead of images. This first video shows a full, reliable drive-by download against Fedora 25 + Google Chrome. The strong reliability of this exploit makes it work inside Fedora’s tracker-extract process, which has highly variable heap state that has frustrated my other exploit attempts. Finally, decent exploit proof of my earlier suspicion that tracker + Google Chrome is very dangerous (https://scarybeastsecurity.blogspot.com/2016/11/0day-poc-risky-design-decisions-in.html):
- https://www.youtube.com/watch?v=WKwRijjqdzY

Exploit file: gnome_calc_fedora_25_libc_2.24-3.spc (rename it to .flac to get it to work as in the video).
- Download: https://security.appspot.com/security/spc/gnome_calc_fedora_25_libc_2.24-3.spc
- Mirror: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/40943-1.flac

And this second video shows a couple of different exploitation contexts in Ubuntu 16.04 LTS, using the same exploit file for each. Again, this is showcasing the reliability that the underlying vulnerability permits. The different exploited processes (gnome-video-thumbnailer and totem) have very different heap and threading setups:
- https://www.youtube.com/watch?v=wrCLoem6ggM

Exploit file: xcalc_ubuntu_16.04_libc_2.23-0ubuntu3.spc (rename it to .mp3 to get it to work as in the video).
- Download: https://security.appspot.com/security/spc/xcalc_ubuntu_16.04_libc_2.23-0ubuntu3.spc
- Mirror: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/40943-2.mp3

Impact is mixed. On Ubuntu, the faulty code is installed and on the attack surface by default, if you select the “mp3” option during install -- which I certainly always do. On Fedora, there’s a very sensible decision to split gstreamer1-plugins-bad into multiple packages, with only gstreamer1-plugins-bad-free installed by default. This limits the attack surface and does not include Game Music Emu. Of course, the gstreamer framework will happily offer to install gstreamer1-plugins-bad-free-extras, with a very nice UI, if the victim simply tries to open the relevant media file.

As always, the general lack of sandboxing here contributes to the severity. I think we inhabit a world where media parsing sandboxes should be mandatory these days. There’s hope: some of my other recent disclosures appear to have motivated a sandbox for Gnome’s tracker (https://bugzilla.gnome.org/show_bug.cgi?id=764786).