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Subject: Re: [RFC PATCH v2] x86/boot: add .sbat section to the bzImage
From:   James Bottomley <James.Bottomley@HansenPartnership.com>
To:     Luca Boccassi <bluca@debian.org>
Cc:     Eric Snowberg <eric.snowberg@oracle.com>,
        Ard Biesheuvel <ardb@kernel.org>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
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Date:   Fri, 21 Jul 2023 09:33:56 -0400
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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