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

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Date:	Fri, 02 Nov 2012 23:38:23 +0000
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 Fri, 2012-11-02 at 18:04 +0000, Matthew Garrett wrote:
> On Fri, Nov 02, 2012 at 05:57:38PM +0000, James Bottomley wrote:
> > On Fri, 2012-11-02 at 17:54 +0000, Matthew Garrett wrote:
> > > ? That's the message generated by the Windows access control mechanism 
> > > when you run a binary that requests elevated privileges.
> > 
> > So that's a windows attack vector using a windows binary? I can't really
> > see how it's relevant to the secure boot discussion then.
> 
> 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.

James



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