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Date: Tue, 03 Apr 2018 23:59:40 +0000
From: Matthew Garrett <mjg59@...gle.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: luto@...nel.org, David Howells <dhowells@...hat.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, jmorris@...ei.org,
Alan Cox <gnomes@...rguk.ukuu.org.uk>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
jforbes@...hat.com, linux-man@...r.kernel.org, jlee@...e.com,
LSM List <linux-security-module@...r.kernel.org>,
linux-api@...r.kernel.org, Kees Cook <keescook@...omium.org>,
linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [GIT PULL] Kernel lockdown for secure boot
On Tue, Apr 3, 2018 at 4:55 PM Linus Torvalds
<torvalds@...ux-foundation.org>
wrote:
> On Tue, Apr 3, 2018 at 4:45 PM, Matthew Garrett <mjg59@...gle.com> wrote:
> >> Be honest now. It wasn't generally users who clamored for it.
> >
> > If you ask a user whether they want a system that lets an attacker
replace
> > their kernel or one that doesn't, what do you think their answer is
likely
> > to be?
> Goddamnit.
> We both know what the answer will be.
> And it will have *nothing* to do with secure boot.
Right, because they care about outcome rather than mechanism. Secure Boot
is the mechanism we have to make that outcome possible.
> > Again, what is your proposed mechanism for ensuring that off the shelf
> > systems can be configured in a way that makes this possible?
> If you think lockdown is a good idea, and you enabled it, then IT IS
ENABLED.
Ok. So we can build distribution kernels that *always* have this on, and to
turn it off you have to disable Secure Boot and install a different kernel.
Or we can build distribution kernels that only have this on when you're
booting in a context that makes sense, and you can disable it by just
disabling Secure Boot (by running mokutil --disable-validation) and not
have to install a new kernel. Which outcome do you prefer?
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