[PATCH 2/5] scripts/Makefile.lib: Embed capsule public key in platform's dtb

[Tom Rini]

On Thu, Aug 17, 2023 at 07:41:33AM -0600, Simon Glass wrote:
> Hi Tom,
> 
> On Wed, 16 Aug 2023 at 15:26, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Wed, Aug 16, 2023 at 09:58:42AM +0530, Sughosh Ganu wrote:
> > > hi Simon,
> > >
> > > On Wed, 16 Aug 2023 at 00:09, Simon Glass <sjg at chromium.org> wrote:
> > > >
> > > > Hi Sughosh,
> > > >
> > > > On Tue, 15 Aug 2023 at 10:26, Sughosh Ganu <sughosh.ganu at linaro.org> wrote:
> > > > >
> > > > > The EFI capsule authentication logic in u-boot expects the public key
> > > > > in the form of an EFI Signature List(ESL) to be provided as part of
> > > > > the platform's dtb. Currently, the embedding of the ESL file into the
> > > > > dtb needs to be done manually.
> > > > >
> > > > > Add a target for generating a dtsi file which contains the signature
> > > > > node with the ESL file included as a property under the signature
> > > > > node. Include the dtsi file in the dtb. This brings the embedding of
> > > > > the ESL in the dtb into the U-Boot build flow.
> > > > >
> > > > > The path to the ESL file is specified through the
> > > > > CONFIG_EFI_CAPSULE_ESL_FILE symbol.
> > > > >
> > > > > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > > > > ---
> > > > > Changes since RFC series:
> > > > > * Remove the default value of the config symbol.
> > > > > * s/include_files/dtsi_include_list
> > > > > * Add all the dtsi files being included as dependency for the dtb
> > > > >   target.
> > > > >
> > > > >  lib/efi_loader/Kconfig             |  8 ++++++++
> > > > >  lib/efi_loader/capsule_esl.dtsi.in | 11 +++++++++++
> > > > >  scripts/Makefile.lib               | 18 +++++++++++++++++-
> > > > >  3 files changed, 36 insertions(+), 1 deletion(-)
> > > > >  create mode 100644 lib/efi_loader/capsule_esl.dtsi.in
> > > > >
> > > > > diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> > > > > index 9989e3f384..d20aaab6db 100644
> > > > > --- a/lib/efi_loader/Kconfig
> > > > > +++ b/lib/efi_loader/Kconfig
> > > > > @@ -272,6 +272,14 @@ config EFI_CAPSULE_MAX
> > > > >           Select the max capsule index value used for capsule report
> > > > >           variables. This value is used to create CapsuleMax variable.
> > > > >
> > > > > +config EFI_CAPSULE_ESL_FILE
> > > > > +       string "Path to the EFI Signature List File"
> > > >
> > > > Do we need this, or could we name it as we do with the .env file? It
> > > > seems confusing to have to set this for each board - it might be
> > > > better to have it in a defined location.
> > >
> > > The reason I put this is because I thought this gave the user the
> > > flexibility to provide the location and name of the ESL. But I suppose
> > > that the board directory would be a good location to expect this file.
> > > Then this file can have a name like capsule_pub_key,esl. Tom, what are
> > > your thoughts on this?
> >
> > I feel like an automatic name we can guess isn't likely how this will be
> > used in the real world, so we should leave this as configurable.
> 
> Are we expecting these files to end up in the source tree? Where would they go?

Yes, they should be
board/vendor/common/whatever-vendor-uses-internally.esl or so.  As I
think I mentioned on IRC, in theory someone like Asus should be using
the same file here for their rockchip-based tinker board and their x8664
based motherboards too.  And it's a public key, not a private key.  But
we still need to ask here because a vendor may care more about
"security" and so have the key /over/somewhere/else more than
reproducible builds.

-- 
Tom
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