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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     David Howells <dhowells@redhat.com>
Cc:     Andy Lutomirski <luto@kernel.org>, Jann Horn <jannh@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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Date:   Wed, 04 Apr 2018 10:43:57 -0500
In-Reply-To: <20736.1522829117@warthog.procyon.org.uk> (David Howells's
        message of "Wed, 04 Apr 2018 09:05:17 +0100")
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Subject: Re: [GIT PULL] Kernel lockdown for secure boot
Sender: linux-kernel-owner@vger.kernel.org
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David Howells <dhowells@redhat.com> writes:

> Andy Lutomirski <luto@kernel.org> wrote:
>
>> As far as I can tell, what's really going on here is that there's a
>> significant contingent here that wants to prevent Linux from
>> chainloading something that isn't Linux.
>
> You have completely the wrong end of the stick.  No one has said that or even
> implied that.  You are alleging dishonesty on our part.
>
> What we *have* said is that *if* we want to pass the secure boot state across
> kexec, then we have to make sure that:
>
>  (1) no one tampers with the intermediate kernel between boot and kexec
>      otherwise the secure boot state is effectively invalidated, and
>
>  (2) the image that gets kexec'ed is trusted.
>
> Remember: you cannot know (2) if you don't have (1).
>
> And if someone tampers with the aim of breaking, say, Windows, then someone,
> e.g.  Microsoft, might blacklist the shim.

*Wow*   You just denied this isn't about not booting Windows and a few
lines later said that is your concern.

I was thinking I would have to dig up old archives where I had been told
this before, but you just nicely repeated all of the old arguments so I
don't see the point.

Eric