[lxc-users] is starting unprivileged containers as root as secure as running them as any other user?

[Serge Hallyn]

Quoting Carlos Alberto Lopez Perez (clopez at igalia.com):
> Hi,
> 
> 
> Suppose that we create an unprivileged container as root (using the
> download template or manually converting it with uidmapshift).
> 
> Such container config will contain (for example) the following maps:
> 
> lxc.id_map = u 0 100000 65536
> lxc.id_map = g 0 100000 65536
> 
> And root would be also allowed to use them:
> 
> $ usermod --add-subuids 100000-165536 root
> $ usermod --add-subgids 100000-165536 root
> 
> 
> My question is....
> 
> From a security point of view, does creating and starting an
> unprivileged container as root make any difference than doing it as any
> other user of the host?

Yes.

For example, if you'll then be running lxc-attach as root instead of as
an unpriv user, then any attacks from inside the container against lxc-attach
will attack the root user.

> My understanding is that once the unprivileged container is running,
> root inside such container won't be able to get a host_uid < 100000 (in
> this example) so starting the unprivileged container as root will be as
> secure as starting the container as any other user that is allowed to do
> so via the subuid/subgid maps. Is this right?
> 
> Thanks.
> 



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