linux-kernel - Re: [RFC PATCH v3 1/3] ima: extend clone() with IMA namespace support

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Date:   Wed, 18 Apr 2018 16:27:08 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     John Johansen <john.johansen@...onical.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org,
        containers@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, serge@...lyn.com,
        sunyuqiong1988@...il.com, david.safford@...com,
        mkayaalp@...binghamton.edu,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Mehmet Kayaalp <mkayaalp@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH v3 1/3] ima: extend clone() with IMA namespace
 support

On Wed, 2018-04-18 at 15:12 -0500, Eric W. Biederman wrote:
> Mimi Zohar <zohar@...ux.vnet.ibm.com> writes:
> 
> > On Wed, 2018-04-18 at 09:09 -0700, John Johansen wrote:
> >> On 04/13/2018 09:25 AM, Mimi Zohar wrote:
> >> > [Cc'ing John Johansen]
> >> > 
> >> > On Tue, 2018-03-27 at 18:01 -0500, Eric W. Biederman wrote:
> >> > [...]
> >> >> As such I expect the best way to create the ima namespace is by simply
> >> >> writing to securityfs/imafs.  Possibly before the user namespace is
> >> >> even unshared.  That would allow IMA to keep track of things from
> >> >> before a container is created.
> >> > 
> >> 
> >> I do think this is generally the right approach for LSMs when looking
> >> forward to LSM stacking and more LSMs.
> >> 
> >> 
> >> > My initial thought was to stage IMA namespacing with just IMA-audit
> >> > first, followed by either IMA-measurement or IMA-appraisal.  This
> >> > would allow us to get the basic IMA namespacing framework working and
> >> > defer dealing with the securityfs related namespacing of the IMA
> >> > policy and measurement list issues to later.
> >> > 
> >> > By tying IMA namespacing to a securityfs ima/unshare file, we would
> >> > need to address the securityfs issues first.
> >> > 
> >> 
> >> well it depends on what you want to do. It would be possible to have
> >> a simple file (not a jump link) within securityfs that IMA could use
> >> without having to deal with all the securityfs issues first. However it
> >> does require that securityfs (not necessarily imafs) be visible within
> >> the mount namespace of the task doing the setup.
> >
> > Eric, would you be OK with that?
> 
> Roughly.  My understanding is that you have to have a write to some
> filesystem to set the ima policy.
> 
> I was expecting having to write an "create ima namespace" value
> to the filesystem would not be any special effort.
> 
> Now it sounds like providing the "create an ima namespace" is going to
> be a special case, and that does not sound correct.

This is not any different than any of the other security/ima/ files
(eg. policy, ascii_runtime_measurements, ...).  The next IMA
namespacing stage would add support for these files.

Mimi