On Fri, 2020-06-12 at 15:11 +0000, Roberto Sassu wrote: > with recent patches, boot_aggregate can be calculated from non-SHA1 > PCR banks. I would replace with: > > Extend cumulative digest over ... > > Given that with this patch boot_aggregate is calculated differently, > shouldn't we call it boot_aggregate_v2 and enable it with a new > option? So here's the problem: if your current grub doesn't do any TPM extensions (as most don't), then the two boot aggregates are the same because PCRs 8 and 9 are zero and there's a test that doesn't add them to the aggregate if they are zero. For these people its a nop so we shouldn't force them to choose a different version of the same thing. If, however, you're on a distribution where grub is automatically measuring the kernel and command line into PCRs 8 and 9 (I think Fedora 32 does this), your boot aggregate will change. It strikes me in that case we can call this a bug fix, since the boot aggregate isn't properly binding to the previous measurements without PCRs 8 and 9. In this case, do we want to allow people to select an option which doesn't properly bind the IMA log to the boot measurements? That sounds like a security hole to me. However, since it causes a user visible difference in the grub already measures case, do you have a current use case that would be affected? As in are lots of people already running a distro with the TPM grub updates and relying on the old boot aggregate? James
