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

Mimi Zohar
2015-05-21T16:23:29Z

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