On Wed, Jan 27, 2021 at 08:41:29AM -0700, Eric Snowberg wrote: > > > 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. I would tend to agree with this. /Jarkko
