Re: [PATCH v2] xattr: Enable security.capability in user namespaces
From: Serge E. Hallyn
Date: Fri Jul 14 2017 - 09:35:21 EST
Quoting Stefan Berger (stefanb@xxxxxxxxxxxxxxxxxx):
> On 07/13/2017 08:38 PM, Eric W. Biederman wrote:
> >Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx> writes:
> >>On 07/13/2017 01:49 PM, Eric W. Biederman wrote:
> >>>My big question right now is can you implement Ted's suggested
> >>>restriction. Only one security.foo or secuirty.foo@... attribute ?
> >>We need to raw-list the xattrs and do the check before writing them. I am fairly sure this can be done.
> >>So now you want to allow security.foo and one security.foo@uid=<> or just a single one security.foo(@[[:print:]]*)?
> >The latter.
> That case would prevent a container user from overriding the xattr
> on the host. Is that what we want? For limiting the number of xattrs
Not really. If the file is owned by a uid mapped into the container,
then the container root can chown the file which will clear the file
capability, after which he can set a new one. If the file is not
owned by a uid mapped into the container, then container root could
not set a filecap anyway.