10 ms·

> I wonder how many of the bugs led to code execution? Quite a few. We're often affected with VLC, and code execution is easy to get to. But with VLC, you're "

by jbk 13y ago

> I wonder how many of the bugs led to code execution? Quite a few. We're often affected with VLC, and code execution is easy to get to. But with VLC, you're "only" in userland.

tptacek 13y ago
In other words, you're "only" dealing with a bug that would allow anything you downloaded from BitTorrent to own up your personal account on your computer. :) (I know you know that, I'm just spelling it out for people).
- jbk 13y ago
  Yep, and that's quite dangerous. Especially since you can see often fake videos circulate around, that tell you to download a special software or codec to play them (with malware, of course). WMP also had a scripting/runtime system that could be abused greatly. Be careful what you download :)
fulafel 13y ago
Chrome is also in userland - and it has a sandboxing system. Assuming they're sandboxing ffmpeg, these bugs are more risky for VLC users than Chrome users. Plus, Chrome is more diligent with security updates and the auto-update mechanism is fully automatic. A sandboxing system provided by either ffmpeg or VLC would be a very good idea, though it would be some work... encoded data in, decoded frames out via shared memory. Negligible performance impact.
- chubot 13y ago
  Yeah definitely. Really there is a gross violation of the principle of least privilege here. A video player is a great thing to sandbox because all it needs is a video output, very limited file access, and very limited gui input. It doesn't need to read all your files, open network connections, or start processes. Given that there are apparently thousands of bugs in the video parsing code, it seems like a no-brainer. Section 5.2 in this DJB paper talks about (portable) isolation of plain transformations. Video playing is already close to "pure" or could be made pure pretty easily. http://cr.yp.to/qmail/qmailsec-20071101.pdf http://cr.yp.to/qmail/qmailsec-20071101.pdf
  - jbk 13y ago
    > A video player is a great thing to sandbox because all it needs is a video output, very limited file access, and very limited gui input. It doesn't need to read all your files, open network connections, or start processes. Not sure if serious or sarcasm, to be honest, since this seems very far from what we see. A media player is not simple to sandbox, (as the MacOS X sandbox showed us for example), because: - you need to open files by yourself, without user interaction, to support playlists, - you need to open connections by yourself to support video protocol like RTSP, RTMP, RTP, - you need raw device access to support Webcams, Capture devices, DVDs, DVB tuners, - you need to access GPU buffers for direct rendering, and/or shaders to do fast filtering or just plain chroma-conversions, - you need to be able to access the audio output, at low-level, for libsync which is not always doable with the simplified APIs, - and I don't understand what you mean by "very limited gui input"; how is that less than other programs? Sure, it can be done, with performance costs but it's clearly not a "no-brainer".
    - chubot 13y ago
      I'm talking about a multiprocess architecture like Chrome. http://www.chromium.org/developers/design-documents/multi-process-architecture http://www.chromium.org/developers/design-documents/multi-pr... The entire app isn't sandboxed -- just the code that does video parsing, i.e. with the thousands of bugs and hundreds of remote code execution exploits (!). See my other comment on this topic. ffmpeg is already very modular, and used in many video players (user interfaces), so this separation is more than natural -- it already exists in the codebase. BTW, some people seem to be unfamiliar with the multiprocess/Unix design approach (usually people with a Windows background, which I came from as well). I recommend http://www.catb.org/esr/writings/taoup/ http://www.catb.org/esr/writings/taoup/ for a great intro to this design philosophy.
      - jbk 13y ago
        > The entire app isn't sandboxed -- just the code that does video parsing, i.e. with the thousands of bugs and hundreds of remote code execution exploits (!). The exploits are usually on the protocol (access) level, the demuxer (format) level but also the decoder level. While in theory the first 2 are what you call parsing, many security issues appear also at the decoder level. And if you want to split the video decoder from the rendering, you need to introduce an additional memcpy (or two) of full decoded frames, which has an important impact. I agree it would be nice to try, with a correct, separated processes architecture, but it means changing also a bit the usual architecture, where there is a direct-rendering between the decoder and the output.
- jbk 13y ago
  > Negligible performance impact. Memcpying complete video frame in HD at 30 or 60 fps is not negligible performance impact. But I agree it would be a good idea.
  - fulafel 13y ago
    You snipped out the part where I suggested shared memory :) It might get hairier if the platform graphics api wants to supply you a buffer to render into, and you can't pass it a shared memory buffer yourself (that is accessible by that sandboxed process).
Thaxll 13y ago
I'm sure some people are running VLC under root, still in userland but can be very dangerous.
- feepk 13y ago
  This is one of the reasons why you have to use a wrapper for the VLC binary to execute it within a root environment. Said wrapper is usually in an extra package on Linux and not provided on Windows and OS X (it can be compiled manually of course). Like 10 people per year complain about not being able to run VLC as root, but then again, why should you?
- Crito 13y ago
  I'm sure there are some people using telnet and using "password" as their root password. At a certain point it becomes more than reasonable to say "Well don't do that."

by jbk 13y ago

> I wonder how many of the bugs led to code execution? Quite a few. We're often affected with VLC, and code execution is easy to get to. But with VLC, you're "only" in userland.

tptacek 13y ago

In other words, you're "only" dealing with a bug that would allow anything you downloaded from BitTorrent to own up your personal account on your computer. :) (I know you know that, I'm just spelling it out for people).

jbk 13y ago
Yep, and that's quite dangerous. Especially since you can see often fake videos circulate around, that tell you to download a special software or codec to play them (with malware, of course). WMP also had a scripting/runtime system that could be abused greatly. Be careful what you download :)

fulafel 13y ago

Chrome is also in userland - and it has a sandboxing system. Assuming they're sandboxing ffmpeg, these bugs are more risky for VLC users than Chrome users. Plus, Chrome is more diligent with security updates and the auto-update mechanism is fully automatic. A sandboxing system provided by either ffmpeg or VLC would be a very good idea, though it would be some work... encoded data in, decoded frames out via shared memory. Negligible performance impact.

chubot 13y ago
Yeah definitely. Really there is a gross violation of the principle of least privilege here. A video player is a great thing to sandbox because all it needs is a video output, very limited file access, and very limited gui input. It doesn't need to read all your files, open network connections, or start processes. Given that there are apparently thousands of bugs in the video parsing code, it seems like a no-brainer. Section 5.2 in this DJB paper talks about (portable) isolation of plain transformations. Video playing is already close to "pure" or could be made pure pretty easily. http://cr.yp.to/qmail/qmailsec-20071101.pdf http://cr.yp.to/qmail/qmailsec-20071101.pdf
- jbk 13y ago
  > A video player is a great thing to sandbox because all it needs is a video output, very limited file access, and very limited gui input. It doesn't need to read all your files, open network connections, or start processes. Not sure if serious or sarcasm, to be honest, since this seems very far from what we see. A media player is not simple to sandbox, (as the MacOS X sandbox showed us for example), because: - you need to open files by yourself, without user interaction, to support playlists, - you need to open connections by yourself to support video protocol like RTSP, RTMP, RTP, - you need raw device access to support Webcams, Capture devices, DVDs, DVB tuners, - you need to access GPU buffers for direct rendering, and/or shaders to do fast filtering or just plain chroma-conversions, - you need to be able to access the audio output, at low-level, for libsync which is not always doable with the simplified APIs, - and I don't understand what you mean by "very limited gui input"; how is that less than other programs? Sure, it can be done, with performance costs but it's clearly not a "no-brainer".
  - chubot 13y ago
    I'm talking about a multiprocess architecture like Chrome. http://www.chromium.org/developers/design-documents/multi-process-architecture http://www.chromium.org/developers/design-documents/multi-pr... The entire app isn't sandboxed -- just the code that does video parsing, i.e. with the thousands of bugs and hundreds of remote code execution exploits (!). See my other comment on this topic. ffmpeg is already very modular, and used in many video players (user interfaces), so this separation is more than natural -- it already exists in the codebase. BTW, some people seem to be unfamiliar with the multiprocess/Unix design approach (usually people with a Windows background, which I came from as well). I recommend http://www.catb.org/esr/writings/taoup/ http://www.catb.org/esr/writings/taoup/ for a great intro to this design philosophy.
    - jbk 13y ago
      > The entire app isn't sandboxed -- just the code that does video parsing, i.e. with the thousands of bugs and hundreds of remote code execution exploits (!). The exploits are usually on the protocol (access) level, the demuxer (format) level but also the decoder level. While in theory the first 2 are what you call parsing, many security issues appear also at the decoder level. And if you want to split the video decoder from the rendering, you need to introduce an additional memcpy (or two) of full decoded frames, which has an important impact. I agree it would be nice to try, with a correct, separated processes architecture, but it means changing also a bit the usual architecture, where there is a direct-rendering between the decoder and the output.
jbk 13y ago
> Negligible performance impact. Memcpying complete video frame in HD at 30 or 60 fps is not negligible performance impact. But I agree it would be a good idea.
- fulafel 13y ago
  You snipped out the part where I suggested shared memory :) It might get hairier if the platform graphics api wants to supply you a buffer to render into, and you can't pass it a shared memory buffer yourself (that is accessible by that sandboxed process).

Thaxll 13y ago

I'm sure some people are running VLC under root, still in userland but can be very dangerous.

feepk 13y ago
This is one of the reasons why you have to use a wrapper for the VLC binary to execute it within a root environment. Said wrapper is usually in an extra package on Linux and not provided on Windows and OS X (it can be compiled manually of course). Like 10 people per year complain about not being able to run VLC as root, but then again, why should you?
Crito 13y ago
I'm sure there are some people using telnet and using "password" as their root password. At a certain point it becomes more than reasonable to say "Well don't do that."