On 10/31/2012 11:02 AM, Matthew Garrett wrote:
On Wed, Oct 31, 2012 at 03:50:00PM +0100, Jiri Kosina wrote:
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).
shim generates a public and private key. It hands the kernel the private
key in a boot parameter and stores the public key in a boot variable. On
suspend, the kernel signs the suspend image with that private key and
discards it. On the next boot, shim generates a new key pair and hands
the new private key to the kernel along with the old public key. The
kernel verifies the suspend image before resuming it. The only way to
subvert this would be to be able to access kernel memory
Or the boot variable where you stored the key, but in that case I'd say
the attacker has won too.
directly, which
means the attacker has already won.
Now someone just needs to write it.
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