linux-kernel - Re: Trusted kernel patchset for Secure Boot lockdown

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Date:	Fri, 14 Mar 2014 22:52:56 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	"gnomes@...rguk.ukuu.org.uk" <gnomes@...rguk.ukuu.org.uk>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"jwboyer@...oraproject.org" <jwboyer@...oraproject.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: Trusted kernel patchset for Secure Boot lockdown

On Fri, 2014-03-14 at 22:31 +0000, One Thousand Gnomes wrote:
> On Fri, 14 Mar 2014 22:15:45 +0000
> Matthew Garrett <matthew.garrett@...ula.com> wrote:
> > The general problem includes having to support this even without an
> > selinux policy.
> 
> Yes. No dispute about that. But equally the general solution should allow
> for it.

Well, sure. The current implementation doesn't conflict with selinux in
any way.

> > some other way. ChromeOS will load unmeasured kernel modules provided it
> > can attest to the trustworthyness of the filesystem containing them.
> 
> See "How to Bypass Verified Boot Security in Chromium OS" 8)
> 
> And it attests the trustworthiness of the filesystem by measuring it. If
> you have a measurement of object X that states it is unchanged then you
> have a valid measurement of any subset of object X for which the same
> assertion is proven. In this case since you know all the bits in the root
> fs are as before, so you know all the bits in the module are as before

You may attest to the trustworthiness of a filesystem by measuring it,
but you may also attest to it via some other means - for instance, it's
read-only and stored on media that requires physical presence to
modify. 

-- 
Matthew Garrett <matthew.garrett@...ula.com>