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

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Message-Id: <1501077470.28419.8.camel@linux.vnet.ibm.com>
Date:   Wed, 26 Jul 2017 09:57:50 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     "Serge E. Hallyn" <serge@...lyn.com>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Mimi Zohar <zohar@...ibm.com>, "Theodore Ts'o" <tytso@....edu>,
        containers@...ts.linux-foundation.org, lkp@...org,
        linux-kernel@...r.kernel.org, tycho@...ker.com,
        James.Bottomley@...senPartnership.com, vgoyal@...hat.com,
        christian.brauner@...lbox.org, amir73il@...il.com,
        linux-security-module@...r.kernel.org, casey@...aufler-ca.com
Subject: Re: [PATCH v2] xattr: Enable security.capability in user namespaces

On Tue, 2017-07-25 at 22:00 -0500, Serge E. Hallyn wrote:
> On Fri, Jul 14, 2017 at 03:26:14PM -0400, Mimi Zohar wrote:
> > On Fri, 2017-07-14 at 13:17 -0500, Eric W. Biederman wrote:
> > > Which brings us to the semantic question of would it be nice to have
> > > stacked IMA/EVM on the same file.
> > > 
> > > I really don't think we do.  I think allowing multiple keys for
> > > different part of trusting files is easy enough that we should have no
> > > need to fight over which keys do which.
> > 
> > We definitely want to support different policies on the native and in
> > the namespace with different keys and keyrings.
> 
> Ok, so Stefan's code to support userspace in a container reading
> security.ima and getting back the value for security.ima@...=1000
> (if 1000 is the kuid of the container's root user) is in fact
> useful to IMA?

Definitely!  Root within the namespace needs to be able to read and
write security.ima in order to (re)sign files, with a specific key
known to that container.  Stefan's code provides different views of
the security xattrs.

Mimi