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

From: Eric W. Biederman
Date: Fri Jul 14 2017 - 08:12:59 EST

Stefan Berger <stefanb@xxxxxxxxxxxxxxxxxx> writes:

> 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?

Most definitely. If a more privileged use has set secure.capable that
is better.

> For limiting the number of xattrs and
> getting that functionality (override IMA signature for example) the
> former seems better...

I don't know about IMA. But my feeling is that we will only be dealing
with a single signing key, so I don't see how having multiple IMA xattrs
make sense. Could you explain that to me?

> For the former I now have the topmost patch here:

Thank you.