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

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Message-ID: <20121103002244.GC18691@srcf.ucam.org>
Date:	Sat, 3 Nov 2012 00:22:44 +0000
From:	Matthew Garrett <mjg@...hat.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
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 Fri, Nov 02, 2012 at 11:38:23PM +0000, James Bottomley wrote:
> On Fri, 2012-11-02 at 18:04 +0000, Matthew Garrett wrote:
> > A user runs a binary that elevates itself to admin. Absent any flaws in 
> > Windows (cough), that should be all it can do in a Secure Boot world. 
> > But if you can drop a small trusted Linux system in there and use that 
> > to boot a compromised Windows kernel, it can make itself persistent.
> 
> We seem to be talking past each other.  Assume you managed to install a
> Linux boot system on the windows machine.  If the linux boot requires
> present user on first boot (either because the key of the bootloader
> isn't in db or because the MOK database isn't initialised), you still
> don't have a compromise because the loader won't start automatically.

Why would an attacker use one of those Linux systems? There's going to 
be plenty available that don't have that restriction.

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