linux-kernel - Re: [RFC] Second attempt at kernel secure boot support

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Date:	Mon, 05 Nov 2012 09:20:17 +0100
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Pavel Machek <pavel@....cz>,
	Chris Friesen <chris.friesen@...band.com>,
	Eric Paris <eparis@...isplace.org>,
	Jiri Kosina <jkosina@...e.cz>, Oliver Neukum <oneukum@...e.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Josh Boyer <jwboyer@...il.com>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [RFC] Second attempt at kernel secure boot support

On Sun, 2012-11-04 at 13:52 +0000, Matthew Garrett wrote:
> On Sun, Nov 04, 2012 at 09:14:47AM +0000, James Bottomley wrote:
> 
> > I've actually had more than enough experience with automated installs
> > over my career: they're either done by paying someone or using a
> > provisioning system.  In either case, they provision a static image and
> > boot environment description, including EFI boot services variables, so
> > you can provision a default MOK database if you want the ignition image
> > not to pause on firstboot.
> 
> And now you've moved the attack vector to a copy of your provisioning 
> system instead.

Well, no, it always exists: a lot of provisioning systems install efi
(or previously dos) based agents not linux kernels.  However it's a
different vector since the efi agents tend to want to PXE boot and
contact the image server.

> > There is obviously the question of making the provisioning systems
> > secure, but it's a separate one from making boot secure.
> 
> You don't get to punt on making the kernel secure by simply asserting 
> that some other system can be secure instead. The chain of trust needs 
> to go all the way back - if your security model is based on all installs 
> needing a physically present end user, all installs need a physically 
> present end user. That's not acceptable, so we need a different security 
> model.

I didn't.  I advocated a simple security model which you asserted
wouldn't allow unattended installs, so I explained how they could be
done.  

James


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