Injecting public keys into FTDs for FIT verification

[Rasmus Villemoes]

On 05/11/2021 11.16, Jan Kiszka wrote:
> Hi all,
> 
> in order to use CONFIG_FIT_SIGNATURE and also
> CONFIG_SPL_FIT_SIGNATURE, a public key needs to be placed into the
> control FDT. So far, I only found mkimage being able to do that during
> FIT image signing. That is fairly unhandy and often incompatible with
> how firmware is built & signed vs. how the lifecycle of the artifacts to
> be loaded and verified look like. Is there really no other way than
> mkimage -K?
> 
> I'm currently considering to derive a tool that, given a public key
> (which is easy to hand around, compared to the private key needed for
> signing), injects them into a FDT. Then I would hook that up as generic
> feature for U-Boot builds, enriching all control FTDs already during the
> first build with this when requested.
> 
> Am I missing an even simpler approach?

You're not missing an existing upstream simpler approach, but it's
certainly an itch that others have had [1] [2]. My latest attempt

https://lore.kernel.org/u-boot/20210928085651.619892-1-rasmus.villemoes@prevas.dk/

does now have an R-b by Simon, so now I'm just waiting for that to
actually make it into master. I have the script(s) that will convert a
public key to a .dtsi fragment, and I'm happy to share that.

Rasmus

[1]
https://lore.kernel.org/u-boot/CAO5Uq5TyTMacERo01weTEda-5X4Fx-VUoYFHa=mBYhW-RvmVSQ@mail.gmail.com/
[2]
https://lore.kernel.org/u-boot/94d75c521aed46dbb54a8275be2f529e@kaspersky.com/