[U-Boot] [verified-boot] Compile 'key store' DTB without mkimage and private key

[Simon Glass]

Hi Teddy,

On 2 May 2016 at 14:24, Teddy Reed <teddy.reed at gmail.com> wrote:
>
> On Mon, May 2, 2016 at 7:06 AM, Simon Glass <sjg at chromium.org> wrote:
> > Hi Teddy,
> >
> > On 29 April 2016 at 18:44, Teddy Reed <teddy.reed at gmail.com> wrote:
> >> On Fri, Apr 29, 2016 at 4:09 PM, Simon Glass <sjg at chromium.org> wrote:
> >>> Hi Teddy,
> >>>
> >>> On 25 April 2016 at 10:25, Teddy Reed <teddy.reed at gmail.com> wrote:
> >>>> Hi all,
> >>>>
> >>>> I'm curious if anyone has a script (or if I've missed something within
> >>>> the verified-boot documentation) to compile a DTB given only public
> >>>> keying information, i.e., a x509 certificate.
> >>>>
> >>>> I have build/test bots that need to build a u-boot with an
> >>>> extra/embedded DTB containing a signing public key. I do not want the
> >>>> private key on those hosts and the only way I've found to build the
> >>>> documented/required nodes in /signature/key-KEYNAME/
> >>>> ('rsa,r-squared','rsa,modulus', 'rsa,n0-inverse' and 'rsa-num-bits')
> >>>> is by using mkimage on a FIT with the -K switch. That requires a
> >>>> private key to do the actual signing.
> >>>>
> >>>> I'm happy to write something, just want to ask first!
> >>>
> >>> Not on my side, sorry. Would be useful.
> >>>
> >>
> >> Ok!
> >>
> >> I can't make any promises of completeness, but I quickly hacked
> >> together https://github.com/theopolis/fit-certificate-store, to do
> >> this.
> >> I'll iterate on it over the next few weeks, and I'm more than happy to
> >> take bugs/criticism via Github PRs.
> >
> > Looks good. At some point will you do a U-Boot patch?
>
> Could we define a new environment variable, maybe DTB_KEYS_DIR, or
> build option, that could point to the directory of public keys.
>
> Then the U-Boot/SPL build could synthesize the EXT_DTB inline. :)

An env variable sounds reasonable to me.

Regards,
Simon