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

From: Mimi Zohar
Date: Thu Feb 28 2013 - 20:49:16 EST

On Thu, 2013-02-28 at 17:20 -0500, Eric Paris wrote:
> On Thu, Feb 28, 2013 at 4:35 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> > On Thu, Feb 28, 2013 at 02:23:39PM -0500, Mimi Zohar wrote:
> I think just a second for both of you to step back and see a slightly
> larger picture/problem might help.
> This is a weird case where Vivek does not trust root to make the
> policy decision. If the box is configured for secure boot, it needs
> to make these decisions no matter what the admin wants. This is why
> he talks about trying to merge multiple competing policies. The
> current IMA policy is controlled by whomever can first write to the
> ima policy file interface. Vivek does not want an admin to be able to
> overwrite the secureboot policy. So I get why he thinks changes may
> be needed to support this use case.

Nobody is saying that changes aren't necessary.

> The ima_tcb policy was meant to be larger than needed to determine a
> trusted computing base, but it is clearly not a superset of what he is
> hoping to accomplish.

The 'ima_tcb' policy is for measurement and attestation. The policy
being discussed here is the 'ima_appraise_tcb' used for enforcing local
file integrity.

> So how do we take a system where the admin/software has some control
> over the integrity policy (as it is today?) and the kernel/system
> itself also has control (as Vivek wants it)?

> It seems unsolved with what we have today....

Right, and merging policies won't work. I see where you're going with



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