Re: TPM: hibernate with IMA PCR 10

[Jarkko Sakkinen]

On Mon, Aug 29, 2022 at 02:51:50PM -0700, Matthew Garrett wrote:
> On Mon, Aug 29, 2022 at 2:45 PM Ken Goldman <kgold@xxxxxxxxxxxxx> wrote:
> >
> > On 5/4/2022 7:20 PM, Evan Green wrote:
> > > Enabling the kernel to be able to do encryption and integrity checks on
> > > the hibernate image prevents a malicious userspace from escalating to
> > > kernel execution via hibernation resume.  [snip]
> >
> > I have a related question.
> >
> > When a TPM powers up from hibernation, PCR 10 is reset.  When a
> > hibernate image is restored:
> >
> > 1. Is there a design for how PCR 10 is restored?
> 
> I don't see anything that does that at present.
> 
> > 2. How are /sys/kernel/security/ima/[pseudofiles] saved and
> > restored?
> 
> They're part of the running kernel state, so should re-appear without
> any special casing. However, in the absence of anything repopulating
> PCR 10, they'll no longer match the in-TPM value.

This feature could still be supported, if IMA is disabled
in the kernel configuration, which I see a non-issue as
long as config flag checks are there.

BR, Jarkko