21 ms·

It's really nice to see that happening, but every time I raised the subject with the Gnome team to see how we could run VLC in it, it's a no-go. Indeed, for a

by jbk 12y ago

It's really nice to see that happening, but every time I raised the subject with the Gnome team to see how we could run VLC in it, it's a no-go. Indeed, for a complete media player, I need: - access to files not directly opened by the user (playlists, MKV, DCP, MXF), - access (and unique probably) to raw devices read-only (DVD, AudioCD, Blu-Rays, webcams-v4l2, SDI, DVB), - direct access to raw audio output, - access to X11 for YUV output, or at least a direct OpenGL context, - access to network. For access to files and network, there seemed to be a solution with a manifest to get $home access; for audio, a solution might come with kdbus and pulseaudio; but for the others, they refuse blankly, saying that my "use case is irrelevant and dangerous". I hope this will evolve (maybe it already has), but so far, it's a bit hard to make a complete media player, tbh.

thanksgiving 12y ago
How do they expect you to access the network? Can a web browser or an FTP client be sand boxed in the current scheme?
- jbk 12y ago
  So far, I am not sure, but I think a flag in the manifest will allow a pure networking access ("Use the host network namespace").
bkor 12y ago
If you want raw access to devices, X11, etc, then it is not so simple. The media players I use talk to Pulseaudio, not directly to audio. Various of your needs go pretty much against sandboxing. It's much easier to focus first on applications instead of these needs. For instance, fully sandboxing and X11 won't work anyway. It seems pretty impossible to create something which: 1) does sandboxing 2) has no limitations on what an application can do Edit: What I meant is: Is it possible to lower your requirements or change how VLC works/can do when it is sandboxed?
- jbk 12y ago
  > Is it possible to lower your requirements or change how VLC works/can do when it is sandboxed? Maybe for some, but not for others. You really need to be able to open a file without file opener. Opening optical disks is really important too. I don't get why read-only access to a device poses so much threats but I'm probably missing something. FYI, so far, libpulse links to x11.
  - sp332 12y ago
    Low-level access to a device would let you read data from files that you don't have permission to read at the filesystem level.
    - asveikau 12y ago
      You can set different permissions for different devices, you are aware of that right? I can say my DVD drive is readable by gid x, but not the partitions on my hard disk... This is already what Linux distros are doing.
      - edohyiez 12y ago
        Then the media player can read every DVD you put into your drive as long as its running. So you always have to close the media player before inserting a DVD containing private files. That probably isn't that important for DVDs, but for other devices (e.g. microphone, webcam) it certainly is.
  - tormeh 12y ago
    >You really need to be able to open a file without file opener What if you had read/write access to /home/user/music and /home/user/video ? Once we start adding blanket access like this we would probably need to add a /home/user/secret folder that no application can access unless invited to a specific file by a file opener.
alexlarsson 12y ago
It all depends on what your goal is. Allowing to run VLC as a bundle with more or less full access is certainly possible. However, that is not really "sandboxed" in any fashion. For instance, once any client has any kind of X11 access they can snope any kind of keyboard events, including your password at the unlock screen. If we want to support the full functionallity for a media player in a sandboxed way we need to start looking into each requirement and designing a safe way to access each item. This is gonna be a lot of work, but I don't see any way around that. For your exact list: Files access can either be granted to the app fully or partially. But we also want some kind of file selector service that runs in the session (outside the sandbox) that grants some kind of access to files the user chose. Raw device access will not happen by just having the app open the raw device nodes. Instead we'll have some kind of service in the session that (via user interaction or "remembered" grants from the user) virtualizes access to these things. This could be all from e.g. passing a file descriptor of the opened dvd device to a complete replacement of the subsystem. For an example of the later, for webcams see the pulse-video project: https://github.com/wmanley/pulsevideo https://github.com/wmanley/pulsevideo Is raw audio output necessary? Why does not pulseaudio work? OpenGL access is supported Network access is (optionally, but i think this will be on for most apps) allowed
- weland 12y ago
  > Is raw audio output necessary? Why does not pulseaudio work? I don't know if this applies to VLC, too, but raw audio output (or something that isn't PulseAudio) is necessary wherever low (or at least constant) latency is required. Edit: oh - now that I look at your username, I believe congratulations are in order re. the subject of this thread :)?
  - alexlarsson 12y ago
    PulseAudio can be very low latency. Here are some docs on how to set this up: http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Clients/LatencyControl/ http://www.freedesktop.org/wiki/Software/PulseAudio/Document... That said, I don't think a video player needs low latencies. It can generally have pretty large buffers.
rogerbinns 12y ago
Note that you are requiring all of this in the same/single app. Instead it could be broken down into multiple compartmentalized apps, each doing one thing with simple permissions, and all cooperating. For example one app could do the raw device access, but have no other access including networking. Another does networking but no local access. Another is the renderer to video and audio. Another does UI etc.
- jbk 12y ago
  And how do you share the buffers between the apps?
  - rogerbinns 12y ago
    The desktop environment already has to provide a means of interprocess/component communication, so it gets solved there. You can already see something similar in Chrome where functionality like rendering is done in separate processes.
    - jbk 12y ago
      No it has not. 0-copy shared buffer don't exist yet for most video usecases.
      - rogerbinns 12y ago
        Are you saying it is completely impossible? Or that they haven't done it yet? The former would be a big problem, and the latter is just about the right apis, driver models etc.
        jbk 12y ago
        > Are you saying it is completely impossible? Nothing is impossible, this is software. But it's far far far from being ready.
agwa 12y ago
Instead of sandboxing the entire app, you should use privilege separation inside VLC. Low-risk code would run in processes with higher privileges, while the high-risk code (e.g. the decoders) would run in highly sandboxed processes and communicate with the privileged processes over a simple interface. This is the approach used by security-conscious server apps (e.g. openssh, postfix, dovecot) as well as Google Chrome, and I think it has more promise than trying to sandbox entire apps. Many apps have complex access requirements (much more than the game used as an example in this blog post) and trying to sandbox them will require granting so much privilege that the sandbox becomes almost meaningless. I'm currently working on converting a PDF viewer to use privilege separation. I'd love to see a media player use privilege separation too. Does VLC currently have pretty clear separation between its various components? Do you think it be much work to spin security-conscious parts like the decoders into separate processes?
- jbk 12y ago
  It's a good question. But hard. > Does VLC currently have pretty clear separation between its various components? Very clear separation. One of the best, tbh. > Do you think it be much work to spin security-conscious parts like the decoders into separate processes? Extremely difficult. We've thought about it. For a video player the 3 parts that are sensitive, are protocols (file, http), demuxers (mkv, avi) and decoders. The crashes mostly happen in protocols and demuxers, but not in decoders (a contrario from what people think). The main issue is that the video decoder MUST be in the same process than the video output, for performance reasons (buffer sharing: memcpy is murder) and for hardware decoders. And video output are usually with very high access in the kernels. Moreover video outputs are almost necessarily in the process with the UI thread. For audio output, it's not good either, although some platforms are better (pulseaudio+Kdbus might work).
  - chubot 12y ago
    The main issue is that the video decoder MUST be in the same process than the video output, for performance reasons (buffer sharing: memcpy is murder) Why not used shared memory? I believe that's what Chrome uses for its rendering buffers. The renderer is sandboxed and shares buffers with the X11 process. EDIT, used to use: https://codereview.chromium.org/298443002/ https://codereview.chromium.org/298443002/ Still, it appears it used this method for a long time, so it seems feasible. Also, Chrome has multiple video playing paths, including Flash, which is sandboxed, so I don't see the difference. The Flash video has to be decoded in a sandbox. I imagine HTML5 video is sandboxed somehow too. It is very platform-specific and difficult, and performance is a prime concern, but not impossible.
davidgerard 12y ago
>they refuse blankly, saying that my "use case is irrelevant and dangerous". Because it's not like anyone uses media players in the real world. Seriously, WHAT?
upofadown 12y ago
Why would you want to sandbox an open source program like VLC? This sort of thing is mostly useful to allow the running of proprietary binaries that could be hostile in some way. You are not going to care that much if you can trust a program not to attack other programs.
- cplease 12y ago
  Non "hostile," as you put it, software still has bugs. Attackers can use malicious inputs to exploit buggy software. Unless you personally built software from trusted source with a trusted toolchain, or reverse-engineered and inspected the binary package you are installing, you have no more confidence that your installed binary package is not malicious than any proprietary binary blob. Even presuming the maintainer and packager is not malicious (and why would you trust a random open source maintainer more than a random proprietary maintainer?), there have been cases in the past where repositories have compromised and with malicious packages inserted. These are just the ones we know about. Signatures help but don't solve anything; especially with distributed projects, keys can be compromised in any number of ways. And don't help with malicious actors. That said, I don't see sandboxing Linux apps as particularly revolutionary. Users, ACLs, and chroots have been around for ages. While not especially sugary, they are pretty effective. For full-on app sandboxing, Android is Linux, and they've been doing this since 2008. The average Linux desktop user has legitimate reasons they don't want to sandbox any given desktop app to this extent. On the server side, "sandboxing" in the form of "separation of privileges" has been standard best practice in the UNIX realm as long as Richard Stallman's beard. This is just not particularly interesting. More interesting to me is what has been done for sandboxing in the browser, most especially Chrome.
  - edohyiez 12y ago
    > The average Linux desktop user has legitimate reasons they don't want to sandbox any given desktop app to this extent. Could you expand on that?
    - cplease 12y ago
      It depends on what you mean by "sandboxing" and "app." But basically, with a browser or mobile app, there's a limited number of functions that you may want to permit an app to access, and it's okay to isolate the rest of the app to its own little world. With desktop apps, you generally want to be able to use apply them broadly to all your user data, or you will quickly be frustrated with them. Deeper-level sandboxing of splitting the app up into bipartite high and low-security/complexity components, as with the Chrome browser, requires a lot of engineering for the particular application and can't simply be dropped in place on a given off-the-shelf Linux app. Coarser-level application-specific permissions in the form of AppArmor profiles, installing daemons as their own users with chroots etc, is already available and deployed. The technology to go further with it is already there.
zanny 12y ago
With Wayland and dbus and all the techs going into a modern Linux desktop, it is probably very doable to prompt users when a program tries to open a file with a simple "Application X wants to open file Y in location Z, let it? Yes / No / Allow for all contents of Z / Allow All Locations". That would be a misnomer, because "important" file locations like ~/.config, ~/.share, etc would always prompt user acknowledgement when a program tries to open something in those and it is not the originator program (ie, VLC can open something like ~/.config/vlc or ~/.share/vlc, but if it tried to open ~/.config/mplayer or ~/.share/mplayer you would get a prompt notification of it. > access (and unique probably) to raw devices read-only I don't think this is hard at all, device permissions are something that mostly already works. Just say "App X wants to access device Y, allow? Yes / No / Always". With good package management and distributors, you could have most of these "prompts" configured with sane defaults so you don't get spam when VLC opens files - the distro can just trust VLC in ~/Music and ~/Video all the time, and any user made directories, so just give it access everywhere except the config and share dirs, so on and so forth. When you install something it would make sense to tell users what it uses in the same way Android does upon installation, and if it tries to access something post-install you get a dialog about it (ie, VLC could say at install it uses the network, or it could ask at runtime if it tries to access the network). Why would VLC need raw audio out? Route through pulseaudio, nobody should be opening raw audio devices anymore unless you are Ardour. I think the real problem is nobody gives a shit about desktop security. I mean I run Archlinux where there isn't a single working MAC solution that does not require days of prep work. But having delved a lot into Mac and such, I have no faith in Apparmor or SELinux when PAX and Grsec is doing a much better job and nobody is using it. And they all have holes somewhere, either they don't have fine grained device permissions, or lack tunables, or don't harden the kernel enough to avoid simple exploits. Its a mess nobody is really trying to solve upstream of security implementations and distros are doing a half assed job about it across the board.
em3rgent0rdr 12y ago
for such security, you should use something like Qubes OS (https://qubes-os.org/ https://qubes-os.org/) which uses Xen to sandbox apps into different domains (VMs), and keeps the networking stack in a seperate VM, disk storage in a seperate VM, DE in a seperate VM, etc.
tracker1 12y ago
what's wrong with having a service layer that isn't sandboxed, and an application layer that is? What's stopping you from running your filesystem and network requests through a local service... you can sandbox all the rendering and other access, and tighten controls on your service interface.
deleted 12y ago
[deleted]
digi_owl 12y ago
Yeah, if this sandboxing is anything like the Storage Access Framework that Google introduced in Android 4.4, i'll pass...

by jbk 12y ago

thanksgiving 12y ago

How do they expect you to access the network? Can a web browser or an FTP client be sand boxed in the current scheme?

jbk 12y ago
So far, I am not sure, but I think a flag in the manifest will allow a pure networking access ("Use the host network namespace").

bkor 12y ago

If you want raw access to devices, X11, etc, then it is not so simple. The media players I use talk to Pulseaudio, not directly to audio. Various of your needs go pretty much against sandboxing. It's much easier to focus first on applications instead of these needs. For instance, fully sandboxing and X11 won't work anyway. It seems pretty impossible to create something which: 1) does sandboxing 2) has no limitations on what an application can do Edit: What I meant is: Is it possible to lower your requirements or change how VLC works/can do when it is sandboxed?

jbk 12y ago
> Is it possible to lower your requirements or change how VLC works/can do when it is sandboxed? Maybe for some, but not for others. You really need to be able to open a file without file opener. Opening optical disks is really important too. I don't get why read-only access to a device poses so much threats but I'm probably missing something. FYI, so far, libpulse links to x11.
- sp332 12y ago
  Low-level access to a device would let you read data from files that you don't have permission to read at the filesystem level.
  - asveikau 12y ago
    You can set different permissions for different devices, you are aware of that right? I can say my DVD drive is readable by gid x, but not the partitions on my hard disk... This is already what Linux distros are doing.
    - edohyiez 12y ago
      Then the media player can read every DVD you put into your drive as long as its running. So you always have to close the media player before inserting a DVD containing private files. That probably isn't that important for DVDs, but for other devices (e.g. microphone, webcam) it certainly is.
- tormeh 12y ago
  >You really need to be able to open a file without file opener What if you had read/write access to /home/user/music and /home/user/video ? Once we start adding blanket access like this we would probably need to add a /home/user/secret folder that no application can access unless invited to a specific file by a file opener.

alexlarsson 12y ago

It all depends on what your goal is. Allowing to run VLC as a bundle with more or less full access is certainly possible. However, that is not really "sandboxed" in any fashion. For instance, once any client has any kind of X11 access they can snope any kind of keyboard events, including your password at the unlock screen. If we want to support the full functionallity for a media player in a sandboxed way we need to start looking into each requirement and designing a safe way to access each item. This is gonna be a lot of work, but I don't see any way around that. For your exact list: Files access can either be granted to the app fully or partially. But we also want some kind of file selector service that runs in the session (outside the sandbox) that grants some kind of access to files the user chose. Raw device access will not happen by just having the app open the raw device nodes. Instead we'll have some kind of service in the session that (via user interaction or "remembered" grants from the user) virtualizes access to these things. This could be all from e.g. passing a file descriptor of the opened dvd device to a complete replacement of the subsystem. For an example of the later, for webcams see the pulse-video project: https://github.com/wmanley/pulsevideo https://github.com/wmanley/pulsevideo Is raw audio output necessary? Why does not pulseaudio work? OpenGL access is supported Network access is (optionally, but i think this will be on for most apps) allowed

weland 12y ago
> Is raw audio output necessary? Why does not pulseaudio work? I don't know if this applies to VLC, too, but raw audio output (or something that isn't PulseAudio) is necessary wherever low (or at least constant) latency is required. Edit: oh - now that I look at your username, I believe congratulations are in order re. the subject of this thread :)?
- alexlarsson 12y ago
  PulseAudio can be very low latency. Here are some docs on how to set this up: http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Clients/LatencyControl/ http://www.freedesktop.org/wiki/Software/PulseAudio/Document... That said, I don't think a video player needs low latencies. It can generally have pretty large buffers.

rogerbinns 12y ago

Note that you are requiring all of this in the same/single app. Instead it could be broken down into multiple compartmentalized apps, each doing one thing with simple permissions, and all cooperating. For example one app could do the raw device access, but have no other access including networking. Another does networking but no local access. Another is the renderer to video and audio. Another does UI etc.

jbk 12y ago
And how do you share the buffers between the apps?
- rogerbinns 12y ago
  The desktop environment already has to provide a means of interprocess/component communication, so it gets solved there. You can already see something similar in Chrome where functionality like rendering is done in separate processes.
  - jbk 12y ago
    No it has not. 0-copy shared buffer don't exist yet for most video usecases.
    - rogerbinns 12y ago
      Are you saying it is completely impossible? Or that they haven't done it yet? The former would be a big problem, and the latter is just about the right apis, driver models etc.
      - jbk 12y ago
        > Are you saying it is completely impossible? Nothing is impossible, this is software. But it's far far far from being ready.

agwa 12y ago

Instead of sandboxing the entire app, you should use privilege separation inside VLC. Low-risk code would run in processes with higher privileges, while the high-risk code (e.g. the decoders) would run in highly sandboxed processes and communicate with the privileged processes over a simple interface. This is the approach used by security-conscious server apps (e.g. openssh, postfix, dovecot) as well as Google Chrome, and I think it has more promise than trying to sandbox entire apps. Many apps have complex access requirements (much more than the game used as an example in this blog post) and trying to sandbox them will require granting so much privilege that the sandbox becomes almost meaningless. I'm currently working on converting a PDF viewer to use privilege separation. I'd love to see a media player use privilege separation too. Does VLC currently have pretty clear separation between its various components? Do you think it be much work to spin security-conscious parts like the decoders into separate processes?

jbk 12y ago
It's a good question. But hard. > Does VLC currently have pretty clear separation between its various components? Very clear separation. One of the best, tbh. > Do you think it be much work to spin security-conscious parts like the decoders into separate processes? Extremely difficult. We've thought about it. For a video player the 3 parts that are sensitive, are protocols (file, http), demuxers (mkv, avi) and decoders. The crashes mostly happen in protocols and demuxers, but not in decoders (a contrario from what people think). The main issue is that the video decoder MUST be in the same process than the video output, for performance reasons (buffer sharing: memcpy is murder) and for hardware decoders. And video output are usually with very high access in the kernels. Moreover video outputs are almost necessarily in the process with the UI thread. For audio output, it's not good either, although some platforms are better (pulseaudio+Kdbus might work).
- chubot 12y ago
  The main issue is that the video decoder MUST be in the same process than the video output, for performance reasons (buffer sharing: memcpy is murder) Why not used shared memory? I believe that's what Chrome uses for its rendering buffers. The renderer is sandboxed and shares buffers with the X11 process. EDIT, used to use: https://codereview.chromium.org/298443002/ https://codereview.chromium.org/298443002/ Still, it appears it used this method for a long time, so it seems feasible. Also, Chrome has multiple video playing paths, including Flash, which is sandboxed, so I don't see the difference. The Flash video has to be decoded in a sandbox. I imagine HTML5 video is sandboxed somehow too. It is very platform-specific and difficult, and performance is a prime concern, but not impossible.

davidgerard 12y ago

>they refuse blankly, saying that my "use case is irrelevant and dangerous". Because it's not like anyone uses media players in the real world. Seriously, WHAT?

upofadown 12y ago

Why would you want to sandbox an open source program like VLC? This sort of thing is mostly useful to allow the running of proprietary binaries that could be hostile in some way. You are not going to care that much if you can trust a program not to attack other programs.

cplease 12y ago
Non "hostile," as you put it, software still has bugs. Attackers can use malicious inputs to exploit buggy software. Unless you personally built software from trusted source with a trusted toolchain, or reverse-engineered and inspected the binary package you are installing, you have no more confidence that your installed binary package is not malicious than any proprietary binary blob. Even presuming the maintainer and packager is not malicious (and why would you trust a random open source maintainer more than a random proprietary maintainer?), there have been cases in the past where repositories have compromised and with malicious packages inserted. These are just the ones we know about. Signatures help but don't solve anything; especially with distributed projects, keys can be compromised in any number of ways. And don't help with malicious actors. That said, I don't see sandboxing Linux apps as particularly revolutionary. Users, ACLs, and chroots have been around for ages. While not especially sugary, they are pretty effective. For full-on app sandboxing, Android is Linux, and they've been doing this since 2008. The average Linux desktop user has legitimate reasons they don't want to sandbox any given desktop app to this extent. On the server side, "sandboxing" in the form of "separation of privileges" has been standard best practice in the UNIX realm as long as Richard Stallman's beard. This is just not particularly interesting. More interesting to me is what has been done for sandboxing in the browser, most especially Chrome.
- edohyiez 12y ago
  > The average Linux desktop user has legitimate reasons they don't want to sandbox any given desktop app to this extent. Could you expand on that?
  - cplease 12y ago
    It depends on what you mean by "sandboxing" and "app." But basically, with a browser or mobile app, there's a limited number of functions that you may want to permit an app to access, and it's okay to isolate the rest of the app to its own little world. With desktop apps, you generally want to be able to use apply them broadly to all your user data, or you will quickly be frustrated with them. Deeper-level sandboxing of splitting the app up into bipartite high and low-security/complexity components, as with the Chrome browser, requires a lot of engineering for the particular application and can't simply be dropped in place on a given off-the-shelf Linux app. Coarser-level application-specific permissions in the form of AppArmor profiles, installing daemons as their own users with chroots etc, is already available and deployed. The technology to go further with it is already there.

zanny 12y ago

With Wayland and dbus and all the techs going into a modern Linux desktop, it is probably very doable to prompt users when a program tries to open a file with a simple "Application X wants to open file Y in location Z, let it? Yes / No / Allow for all contents of Z / Allow All Locations". That would be a misnomer, because "important" file locations like ~/.config, ~/.share, etc would always prompt user acknowledgement when a program tries to open something in those and it is not the originator program (ie, VLC can open something like ~/.config/vlc or ~/.share/vlc, but if it tried to open ~/.config/mplayer or ~/.share/mplayer you would get a prompt notification of it. > access (and unique probably) to raw devices read-only I don't think this is hard at all, device permissions are something that mostly already works. Just say "App X wants to access device Y, allow? Yes / No / Always". With good package management and distributors, you could have most of these "prompts" configured with sane defaults so you don't get spam when VLC opens files - the distro can just trust VLC in ~/Music and ~/Video all the time, and any user made directories, so just give it access everywhere except the config and share dirs, so on and so forth. When you install something it would make sense to tell users what it uses in the same way Android does upon installation, and if it tries to access something post-install you get a dialog about it (ie, VLC could say at install it uses the network, or it could ask at runtime if it tries to access the network). Why would VLC need raw audio out? Route through pulseaudio, nobody should be opening raw audio devices anymore unless you are Ardour. I think the real problem is nobody gives a shit about desktop security. I mean I run Archlinux where there isn't a single working MAC solution that does not require days of prep work. But having delved a lot into Mac and such, I have no faith in Apparmor or SELinux when PAX and Grsec is doing a much better job and nobody is using it. And they all have holes somewhere, either they don't have fine grained device permissions, or lack tunables, or don't harden the kernel enough to avoid simple exploits. Its a mess nobody is really trying to solve upstream of security implementations and distros are doing a half assed job about it across the board.

em3rgent0rdr 12y ago

for such security, you should use something like Qubes OS (https://qubes-os.org/ https://qubes-os.org/) which uses Xen to sandbox apps into different domains (VMs), and keeps the networking stack in a seperate VM, disk storage in a seperate VM, DE in a seperate VM, etc.

tracker1 12y ago

what's wrong with having a service layer that isn't sandboxed, and an application layer that is? What's stopping you from running your filesystem and network requests through a local service... you can sandbox all the rendering and other access, and tighten controls on your service interface.

deleted 12y ago

[deleted]

digi_owl 12y ago

Yeah, if this sandboxing is anything like the Storage Access Framework that Google introduced in Android 4.4, i'll pass...