linux-kernel - Re: [RFD] linux-firmware key arrangement for firmware signing

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Date:	Thu, 21 May 2015 12:22:20 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	"Woodhouse, David" <david.woodhouse@...el.com>
Cc:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"seth.forshee@...onical.com" <seth.forshee@...onical.com>,
	"mricon@...nel.org" <mricon@...nel.org>,
	"dhowells@...hat.com" <dhowells@...hat.com>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"jlee@...e.de" <jlee@...e.de>, "kyle@...nel.org" <kyle@...nel.org>,
	"gnomes@...rguk.ukuu.org.uk" <gnomes@...rguk.ukuu.org.uk>,
	"james.l.morris@...cle.com" <james.l.morris@...cle.com>,
	"mcgrof@...e.com" <mcgrof@...e.com>,
	"serge@...lyn.com" <serge@...lyn.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
Subject: Re: [RFD] linux-firmware key arrangement for firmware signing

On Thu, 2015-05-21 at 16:03 +0000, Woodhouse, David wrote:
> On Thu, 2015-05-21 at 08:45 -0700, Greg Kroah-Hartman wrote:
> > On Thu, May 21, 2015 at 09:05:21AM -0400, Mimi Zohar wrote:
> > > Signatures don't provide any guarantees as to code quality or
> > > correctness.   They do provide file integrity and provenance.  In
> > > addition to the license and a Signed-off-by line, having the 
> > > firmware provider include a signature of the firmware would be 
> > > nice.
> > 
> > That would be "nice", but that's not going to be happening here, from
> > what I can tell.  The firmware provider should be putting the signature
> > inside the firmware image itself, and verifying it on the device, in
> > order to properly "know" that it should be running that firmware.  The
> > kernel shouldn't be involved here at all, as Alan pointed out.
> 
> In a lot of cases we have loadable firmware precisely to allow us to
> reduce the cost of the hardware. Adding cryptographic capability in the
> 'load firmware' state of the device isn't really compatible with that
> :)
> 
> In the case where kernel and modules are signed, it *is* useful for a
> kernel device driver also to be able to validate that what it's about
> to load into a device is authentic. Where 'authentic' will originally
> just mean that it's come from the linux-firmware.git repository or the
> same entity that built (and signed) the kernel, but actually I *do*
> expect vendors who are actively maintaining the firmware images in
> linux-firmware.git to start providing detached signatures of their own.

That's great!  What format do you expect the detached signatures to be?
Where will they reside?

Mimi

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