[GIT PULL] Kernel lockdown for secure boot

Matthew Garrett mjg59 at google.com
Wed Apr 4 16:42:20 UTC 2018

On Wed, Apr 4, 2018 at 9:39 AM Andy Lutomirski <luto at kernel.org> wrote:
> On Wed, Apr 4, 2018 at 9:22 AM, Matthew Garrett <mjg59 at google.com> wrote:
> > If you don't have secure boot then an attacker with root can modify your
> > bootloader or kernel, and on next boot lockdown can be silently

> This has been rebutted over and over and over.  Secure boot is not the
> only verified boot mechanism in the world.  Other, better, much more
> auditable, and much simpler mechanisms have been around for a long,
> long time.

Right and if you *know* that you're in that situation then you either turn
it on in bootparams from the verified bootloader (which we can't do in UEFI
because the *firmware* can be the bootloader thanks to the EFI boot stub)
or you enable it from userland later (I can't remember if this version of
the patchset provides that functionality, but a previous one did).

> > Which is why Shim allows you to disable validation if you prove physical
> > user presence.

> And that's a giant hack.  The actual feature should be that a user
> proves physical presence and thus disables lockdown *without*
> disabling verification.

That's a completely reasonable feature request.
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