linux-kernel - Re: [PATCH 01/12] Security: Add CAP_COMPROMISE

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Date:	Wed, 20 Mar 2013 20:37:36 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC:	James Morris <jmorris@...ei.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 01/12] Security: Add CAP_COMPROMISE_KERNEL

On Wed, 2013-03-20 at 15:16 -0400, Mimi Zohar wrote:
> On Wed, 2013-03-20 at 18:12 +0000, Matthew Garrett wrote:
> > Well, in the absence of hardcoded in-kernel policy, there needs to be
> > some mechanism for ensuring the integrity of a policy. Shipping a signed
> > policy initramfs fragment and having any Secure Boot bootloaders pass a
> > flag in bootparams indicating that the kernel should panic if that
> > fragment isn't present would seem to be the easiest way of doing that.
> > Or have I misunderstood the question?
> 
> Ok, I was confused by the term "fragmented" initramfs.  So once you have
> verified the "early" fragmented initramfs signature, this initramfs will
> load the "trusted" public keys and could also load the MAC policy. (I
> realize that dracut is currently loading the MAC policy, not the
> initramfs.)  The MAC policy would then be trusted, right?  Could we then
> use the LSM labels for defining an integrity policy for kexec?

Right, that'd be the rough idea. Any further runtime policy updates
would presumably need to be signed with a trusted key.

-- 
Matthew Garrett | mjg59@...f.ucam.org