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

[Mimi Zohar]

On Wed, 2018-04-18 at 15:12 -0500, Eric W. Biederman wrote:
> Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> 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. ÂThis
> >> > 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, ...). ÂThe next IMA
namespacing stage would add support for these files.

Mimi