Re: [RFC PATCH v2] x86/boot: add .sbat section to the bzImage

James Bottomley
2023-07-21T13:34:06Z

On Fri, 2023-07-21 at 14:10 +0100, Luca Boccassi wrote:
> On Fri, 21 Jul 2023 at 14:01, James Bottomley
> <James.Bottomley@hansenpartnership.com> wrote:
[...]
> > Well, my job is to be concerned about how individuals who want to
> > own their own keys, either in MoK or db, participate in this, so I
> > am mostly thinking about local signing.  Whatever we decide, there
> > must be a local workflow pathway.
>
> Sure but for local signing via MoK that's obviously fine, as one gets
> to keep the pieces. AFAIK it's a different flow in Shim whether
> something is authorized by MoK, DB or the built-in cert, so having
> different policies built-in for those different cases should be
> doable. Actually at the moment even if Shim loads the image, if it
> gets authorized by DB .sbat isn't checked at all.

So let's be sure we mean the same thing here. There is really no third
party CA. Microsoft gives the distributions a signing key to allow
them to sign their version of shim. Some distributions, like Red Hat,
also embed their signing certificates in shim, so shim can distinguish
between a RH key and another key added to MokList. However, some
distributions, like SUSE, insist that all signing keys be approved by
the machine owner (so no embedded shim certs for non-enterprise) and
their shim can't distinguish between SUSE keys and machine owner
additions. Given the variances in key handling, I think trying to
distinguish between official and developer keys is a huge addition of
complexity we don't need, so there has to be a workflow that functions
for both and that workflow would seem to be allowing non-existent or
empty sbat sections. Official key holders would *always* add sbat
sections, so there's really no problem that needs a solution to be
mandated here.

James