> On Jan 27, 2021, at 7:03 AM, Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote: > > [Cc'ing linux-integrity] > > On Wed, 2021-01-27 at 11:46 +0000, David Howells wrote: >> Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: >> >>>> I suppose a user space tool could be created. But wouldn’t what is >>>> currently done in the kernel in this area need to be removed? >>> >>> Right. I don't think this was a great idea in the first place to >>> do to the kernel but since it exists, I guess the patch does make >>> sense. >> >> This information needs to be loaded from the UEFI tables before the system >> starts loading any kernel modules or running any programs (if we do >> verification of such, which I think IMA can do). > > There needs to a clear distinction between the pre-boot and post-boot > keys. UEFI has its own trust model, which should be limited to UEFI. > The .platform keyring was upstreamed and limited to verifying the kexec > kernel image. Any other usage of the .platform keyring keys is > abusing its intended purpose. > > The cover letter says, "Anytime the .platform keyring is used, the > keys in the .blacklist keyring are referenced, if a matching key is > found, the key will be rejected." I don't have a problem with loading > the UEFI X509 dbx entries as long as its usage is limited to verifying > the kexec kernel image. Correct, with my patch, when EFI_CERT_X509_GUID entries are found in the dbx, they will only be used during kexec. I believe the latest dbx file on uefi.org contains three of these entires. Based on my understanding of why the platform keyring was introduced, I intentionally only used these for kexec. I do question the current upstream mainline code though. Currently, when EFI_CERT_X509_SHA256_GUID or EFI_CERT_SHA256_GUID entries are found in the dbx, they are applied everywhere. It seems like there should be a dbx revocation keyring equivalent to the current platform keyring that is only used for pre-boot. If that is a direction you would like to see this go in the future, let me know, I’d be happy to work on it.
