Re: [RFC] Second attempt at kernel secure boot support

[Shea Levy]

On 10/31/2012 10:54 AM, Josh Boyer wrote:
> On Wed, Oct 31, 2012 at 10:50 AM, Jiri Kosina <jkosina@xxxxxxx> wrote:
> > On Mon, 29 Oct 2012, Matthew Garrett wrote:
> >
> > > > > This is pretty much identical to the first patchset, but with the capability
> > > > > renamed (CAP_COMPROMISE_KERNEL) and the kexec patch dropped. If anyone wants
> > > > > to deploy these then they should disable kexec until support for signed
> > > > > kexec payloads has been merged.
> > > > Apparently your patchset currently doesn't handle device firmware loading,
> > > > nor do you seem to mention in in the comments.
> > > Correct.
> > >
> > > > I believe signed firmware loading should be put on plate as well, right?
> > > I think that's definitely something that should be covered. I hadn't
> > > worried about it immediately as any attack would be limited to machines
> > > with a specific piece of hardware, and the attacker would need to expend
> > > a significant amount of reverse engineering work on the firmware - and
> > > we'd probably benefit from them doing that in the long run...
> > Now -- how about resuming from S4?
> >
> > Reading stored memory image (potentially tampered before reboot) from disk
> > is basically DMA-ing arbitrary data over the whole RAM. I am currently not
> > able to imagine a scenario how this could be made "secure" (without
> > storing private keys to sign the hibernation image on the machine itself
> > which, well, doesn't sound secure either).
> I have a patch that disables that.  I imagine it will be included in the
> next submission of the patchset.
>
> You can find it here in the meantime:
>
> http://jwboyer.fedorapeople.org/pub/0001-hibernate-Disable-in-a-Secure-Boot-environment.patch
>
> josh
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Perhaps this is overkill and too efi-specific, but on systems (like efi) 
where there is firmware-manged storage that is protected from unsigned 
access (e.g. efi vars), couldn't the kernel store a hash of the 
hibernation image in that storage?
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