linux-kernel - Re: [PATCH ghak90 V6 02/10] audit: add container id

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Message-ID: <CAHC9VhRFeCFSCn=m6wgDK2tXBN1euc2+bw8o=CfNwptk8t=j7A@mail.gmail.com>
Date:   Mon, 15 Jul 2019 16:38:25 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Tycho Andersen <tycho@...ho.ws>,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        sgrubb@...hat.com, omosnace@...hat.com, dhowells@...hat.com,
        simo@...hat.com, Eric Paris <eparis@...isplace.org>,
        Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
        nhorman@...driver.com
Subject: Re: [PATCH ghak90 V6 02/10] audit: add container id

On Mon, Jul 8, 2019 at 1:51 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> On 2019-05-29 11:29, Paul Moore wrote:

...

> > The idea is that only container orchestrators should be able to
> > set/modify the audit container ID, and since setting the audit
> > container ID can have a significant effect on the records captured
> > (and their routing to multiple daemons when we get there) modifying
> > the audit container ID is akin to modifying the audit configuration
> > which is why it is gated by CAP_AUDIT_CONTROL.  The current thinking
> > is that you would only change the audit container ID from one
> > set/inherited value to another if you were nesting containers, in
> > which case the nested container orchestrator would need to be granted
> > CAP_AUDIT_CONTROL (which everyone to date seems to agree is a workable
> > compromise).  We did consider allowing for a chain of nested audit
> > container IDs, but the implications of doing so are significant
> > (implementation mess, runtime cost, etc.) so we are leaving that out
> > of this effort.
>
> We had previously discussed the idea of restricting
> orchestrators/engines from only being able to set the audit container
> identifier on their own descendants, but it was discarded.  I've added a
> check to ensure this is now enforced.

When we weren't allowing nested orchestrators it wasn't necessary, but
with the move to support nesting I believe this will be a requirement.
We might also need/want to restrict audit container ID changes if a
descendant is acting as a container orchestrator and managing one or
more audit container IDs; although I'm less certain of the need for
this.

> I've also added a check to ensure that a process can't set its own audit
> container identifier ...

What does this protect against, or what problem does this solve?
Considering how easy it is to fork/exec, it seems like this could be
trivially bypassed.

> ... and that if the identifier is already set, then the
> orchestrator/engine must be in a descendant user namespace from the
> orchestrator that set the previously inherited audit container
> identifier.

You lost me here ... although I don't like the idea of relying on X
namespace inheritance for a hard coded policy on setting the audit
container ID; we've worked hard to keep this independent of any
definition of a "container" and it would sadden me greatly if we had
to go back on that.

-- 
paul moore
www.paul-moore.com