linux-kernel - Re: [PATCH RFC 0/4] Add firmware signature file check

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Message-ID: <s5hd2zri5zi.wl%tiwai@suse.de>
Date:	Tue, 06 Nov 2012 07:46:09 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Josh Boyer <jwboyer@...il.com>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, joeyli <jlee@...e.com>,
	Jiri Kosina <jkosina@...e.cz>,
	David Howells <dhowells@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [PATCH RFC 0/4] Add firmware signature file check

At Mon, 5 Nov 2012 15:43:09 -0500,
Josh Boyer wrote:
> 
> On Mon, Nov 5, 2012 at 12:18 PM, Takashi Iwai <tiwai@...e.de> wrote:
> > Hi,
> >
> > this is a patch series to add the support for firmware signature
> > check.  At this time, the kernel checks extra signature file (*.sig)
> > for each firmware, instead of embedded signature.
> > It's just a quick hack using the existing module signing mechanism,
> > thus provided only as a proof of concept for now.
> >
> > To be noted, it doesn't support the firmwares via udev but only the
> > direct loading, and the check for built-in firmware is missing, too.
> 
> Just to make sure I'm reading this correctly, it will sign any of the
> firwmare files installed directly from the kernel tree if the option is
> set.  So for the firmware in the linux-firmware tree we'd need to
> either copy that into the kernel tree during build time, or duplicate the
> signing bits in the linux-firmware tree itself.  However if we do the
> latter, we'd probably need to use the same keys as the per-build kernel
> key which means copying keys (ew) or tell the kernel to include a
> separate firmware key in the extra list.

Yes, the situation is as same as the external module builds.

> I feel like I'm rambling a bit, but I'm trying to work out how signed
> firmware would look from a distro perspective.  A significant amount of
> work has been done to decouple linux-firmware from the kernel tree and
> if signed firmware is used it seems to couple them together one way or
> another.

Well, the primary question is whether the firmware signature check is
required or not.  Of course, these patches assume that it is for
secure boot lockdown :)

>  At the moment, using generated per-build keys to come up with
> the firmware signatures seems a bit suboptimal in that regard.

But how would distro sign modules that are built externally?
It should be the pretty same situation.

I thought that the current module signing is already supported (at
least accepted) by distro, even for external modules.  Isn't it?


thanks,

Takashi
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