On Wed, Sep 07, 2022 at 07:57:27PM -0400, Mimi Zohar wrote: > On Wed, 2022-09-07 at 13:47 -0700, Evan Green wrote: > > On Tue, Aug 30, 2022 at 7:48 PM Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > > > > > > 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. > > > > Right, from what I understand about IMA, the TPM's PCR getting out of > > sync with the in-kernel measurement list across a hibernate (because > > TPM is reset) or kexec() (because in-memory list gets reset) is > > already a problem. This series doesn't really address that, in that it > > doesn't really make that situation better or worse. > > For kexec, the PCRs are not reset, so the IMA measurment list needs to > be carried across kexec and restored. This is now being done on most > architectures. Afterwards, the IMA measurement list does match the > PCRs. > > Hibernation introduces a different situation, where the the PCRs are > reset, but the measurement list is restored, resulting in their not > matching. As I said earlier the feature still can be supported if kernel does not use IMA but obviously needs to be flagged. BR, Jarkko
