Re: [PATCH v2] xattr: Enable security.capability in user namespaces

From: Serge E. Hallyn
Date: Fri Jul 14 2017 - 13:36:08 EST

Quoting Stefan Berger (stefanb@xxxxxxxxxxxxxxxxxx):
> On 07/14/2017 09:34 AM, Serge E. Hallyn wrote:
> >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 or 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 and one<> or just a single one[[: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.
> Let's say I installed a container where all files are signed and
> thus have security.ima. Now for some reason I want to re-sign some
> or all files inside that container. How would I do that ? Would I
> need to get rid of security.ima first, possibly by copying each
> file, deleting the original file, and renaming the copied file to
> the original name, or should I just be able to write out a new
> signature, thus creating security.ima@uid=1000 besides the
> security.ima ?
> Stefan

Hi Mimi,

what do you think makes most sense for IMA?