Graphically isolating Guix containers with Xpra.

Graphically isolating Guix containers with Xpra.

[Rutger Helling]

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Hey Guix,

Here's a small tip for how you can create graphically isolated containers with Guix and Xpra.

First we create a Xpra server, with no clipboard access.
$ xpra start --clipboard=no :200

Next we switch to an empty tmp directory, and start a Guix container that has access to the X200 socket only.
$ cd tmp
$ guix environment -C --ad-hoc coreutils gedit --expose=/home/$USER/.Xauthority --expose=/tmp/.X11-unix/X200 -- env DISPLAY=:200 XAUTHORITY=/home/$USER/.Xauthority gedit

On a different terminal (or over SSH) you can now access the Xpra server.
$ xpra attach :200

Note that in order to be fully isolated the container should not be able to access even abstract sockets.
You can either run the container without the -N switch, or create a new network namespace with a veth or something like that.

With the following command you can check the sockets. No X11 sockets other than the Xpra one should be shown.
$ ss | grep X11

Once Wayland becomes widely used this will probably be redundant, since the isolation in Wayland is far better than X11. But this might still be useful.

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Re: Graphically isolating Guix containers with Xpra.

[Ludovic Courtès]

Hello Rutger,

Rutger Helling <rhelling@mykolab.com> skribis:

> Here's a small tip for how you can create graphically isolated containers with Guix and Xpra.
>
> First we create a Xpra server, with no clipboard access.
> $ xpra start --clipboard=no :200
>
> Next we switch to an empty tmp directory, and start a Guix container that has access to the X200 socket only.
> $ cd tmp
> $ guix environment -C --ad-hoc coreutils gedit --expose=/home/$USER/.Xauthority --expose=/tmp/.X11-unix/X200 -- env DISPLAY=:200 XAUTHORITY=/home/$USER/.Xauthority gedit
>
> On a different terminal (or over SSH) you can now access the Xpra server.
> $ xpra attach :200

Nice trick!

Did you see the discussion at
<https://lists.gnu.org/archive/html/help-guix/2018-01/msg00056.html>?

This is something we could directly add to ‘guix run’ or similar.

Ludo’.

Re: Graphically isolating Guix containers with Xpra.

[Rutger Helling]

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Hi Ludo,

I've tried 'guix run' for a little bit and I think it has a lot of
potential! One of the problems with guix environment containers is that
it can take quite a while to build. 'guix run' could solve that.

Adding Xpra to 'guix run' and/or 'guix environment' in some way could
definitely be handy for isolation purposes. For the most part it would
just consist of starting up a Xpra socket and exposing that to the
container, then maybe automatically attaching to it.

I've pushed a change to Xpra to start Xvfb with '-nolisten local'. This
disables abstract sockets for the Xorg server that gets started with
Xpra. As a result, using the commands below, you should be isolated even
on the same network namespace.

I can also write something for the Guix documentation, though i'm not
sure if that's considered out-of-scope.

On Fri, 16 Feb 2018 17:55:46 +0100
ludo@gnu.org (Ludovic Courtès) wrote:

> Hello Rutger,
> 
> Rutger Helling <rhelling@mykolab.com> skribis:
> 
> > Here's a small tip for how you can create graphically isolated
> > containers with Guix and Xpra.
> >
> > First we create a Xpra server, with no clipboard access.
> > $ xpra start --clipboard=no :200
> >
> > Next we switch to an empty tmp directory, and start a Guix
> > container that has access to the X200 socket only. $ cd tmp
> > $ guix environment -C --ad-hoc coreutils gedit
> > --expose=/home/$USER/.Xauthority --expose=/tmp/.X11-unix/X200 --
> > env DISPLAY=:200 XAUTHORITY=/home/$USER/.Xauthority gedit
> >
> > On a different terminal (or over SSH) you can now access the Xpra
> > server. $ xpra attach :200  
> 
> Nice trick!
> 
> Did you see the discussion at
> <https://lists.gnu.org/archive/html/help-guix/2018-01/msg00056.html>?
> 
> This is something we could directly add to ‘guix run’ or similar.
> 
> Ludo’.


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