Re: IMA: How to manage user space signing policy with others

From: Mimi Zohar
Date: Thu Feb 28 2013 - 21:17:16 EST

On Thu, 2013-02-28 at 16:35 -0500, Vivek Goyal wrote:
> On Thu, Feb 28, 2013 at 02:23:39PM -0500, Mimi Zohar wrote:
> [..]
> > I would suggest that the ima_appraise_tcb, which is more restrictive, be
> > permitted to replace the secureboot policy.
> Also ima_appraise_tcb is not necessarily more restrictive. It takes
> appraises only for root user. Files for rest of users are not appraised.

Ok, good point.

> In general case of "memory locked execution of signed binary" I was
> hoping to give user a flexibility to do appraisal either for root
> or both root and non-root user.
> For the time being I can hardcode things only for root user but the
> moment somebody will extend functionality for non-root user, again
> we will run into the issue that ima_appraise_tcb is not superset so
> we can't allow that.

So we can agree that the 'ima_appraise_tcb' policy is more restrictive
for root owned files. So as long as the 'ima_appraise_tcb' policy
precedes the secureboot integrity policy, we should be good.



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