On 7/20/21 3:03 AM, Dov Murik wrote: > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3457
I believe the convention is that this line be in the individual patch commit messages just like this (i.e. with the BZ: tag and the first line), not as a Ref: tag at the end of the commit message. I'll let Ard decide on that, though. Thanks, Tom > > Booting with SEV prevented the loading of kernel, initrd, and kernel > command-line via QEMU fw_cfg interface because they arrive from the VMM > which is untrusted in SEV. > > However, in some cases the kernel, initrd, and cmdline are not secret > but should not be modified by the host. In such a case, we want to > verify inside the trusted VM that the kernel, initrd, and cmdline are > indeed the ones expected by the Guest Owner, and only if that is the > case go on and boot them up (removing the need for grub inside OVMF in > that mode). > > This patch series reserves an area in MEMFD (previously the last 1KB of > the launch secret page) which will contain the hashes of these three > blobs (kernel, initrd, cmdline), each under its own GUID entry. This > tables of hashes is populated by QEMU before launch, and encrypted as > part of the initial VM memory; this makes sure these hashes are part of > the SEV measurement (which has to be approved by the Guest Owner for > secret injection, for example). Note that populating the hashes table > requires QEMU support [1]. > > OVMF parses the table of hashes populated by QEMU (patch 10), and as it > reads the fw_cfg blobs from QEMU, it will verify each one against the > expected hash. This is all done inside the trusted VM context. If all > the hashes are correct, boot of the kernel is allowed to continue. > > Any attempt by QEMU to modify the kernel, initrd, cmdline (including > dropping one of them), or to modify the OVMF code that verifies those > hashes, will cause the initial SEV measurement to change and therefore > will be detectable by the Guest Owner during launch before secret > injection. > > Relevant part of OVMF serial log during boot with AmdSevX86 build and > QEMU with -kernel/-initrd/-append: > > ... > BlobVerifierLibSevHashesConstructor: Found injected hashes table in secure > location > Select Item: 0x17 > Select Item: 0x8 > FetchBlob: loading 7379328 bytes for "kernel" > Select Item: 0x18 > Select Item: 0x11 > VerifyBlob: Found GUID 4DE79437-ABD2-427F-B835-D5B172D2045B in table > VerifyBlob: Hash comparison succeeded for "kernel" > Select Item: 0xB > FetchBlob: loading 12483878 bytes for "initrd" > Select Item: 0x12 > VerifyBlob: Found GUID 44BAF731-3A2F-4BD7-9AF1-41E29169781D in table > VerifyBlob: Hash comparison succeeded for "initrd" > Select Item: 0x14 > FetchBlob: loading 86 bytes for "cmdline" > Select Item: 0x15 > VerifyBlob: Found GUID 97D02DD8-BD20-4C94-AA78-E7714D36AB2A in table > VerifyBlob: Hash comparison succeeded for "cmdline" > ... > > The patch series is organized as follows: > > 1: Simple comment fix in adjacent area in the code. > 2: Use GenericQemuLoadImageLib to gain one location for fw_cfg blob > fetching. > 3: Allow the (previously blocked) usage of -kernel in AmdSevX64. > 4-7: Add BlobVerifierLib with null implementation and use it in the correct > location in QemuKernelLoaderFsDxe. > 8-9: Reserve memory for hashes table, declare this area in the reset vector. > 10-11: Add the secure implementation BlobVerifierLibSevHashes and use it in > AmdSevX64 builds. > > [1] > https://lore.kernel.org/qemu-devel/20210624102040.2015280-1-dovmu...@linux.ibm.com/ > > Code is at > https://github.com/confidential-containers-demo/edk2/tree/sev-hashes-v3 > > v3 changes: > - Rename to BlobVerifierLibNull, use decimal INF_VERSION, remove unused > DebugLib reference, fix doxygen comments, add missing IN attribute > - Rename to BlobVerifierLibSevHashes, use decimal INF_VERSION, fix > doxygen comments, add missing IN attribute, > calculate buffer hash only when the guid is found in hashes table > - SecretPei: use ALIGN_VALUE to round the hob size > - Coding style fixes > - Add missing 'Ref:' in patch 1 commit message > - Fix phrasing and typos in commit messages > - Remove Cc: Laszlo from series > > v2: https://edk2.groups.io/g/devel/message/77505 > v2 changes: > - Use the last 1KB of the existing SEV launch secret page for hashes table > (instead of reserving a whole new MEMFD page). > - Build on top of commit cf203024745f ("OvmfPkg/GenericQemuLoadImageLib: Read > cmdline from QemuKernelLoaderFs", 2021-06-28) to have a single location in > which all of kernel/initrd/cmdline are fetched from QEMU. > - Use static linking of the two BlobVerifierLib implemenatations. > - Reorganize series. > > v1: https://edk2.groups.io/g/devel/message/75567 > > Cc: Ard Biesheuvel <ardb+tianoc...@kernel.org> > Cc: Jordan Justen <jordan.l.jus...@intel.com> > Cc: Ashish Kalra <ashish.ka...@amd.com> > Cc: Brijesh Singh <brijesh.si...@amd.com> > Cc: Erdem Aktas <erdemak...@google.com> > Cc: James Bottomley <j...@linux.ibm.com> > Cc: Jiewen Yao <jiewen....@intel.com> > Cc: Min Xu <min.m...@intel.com> > Cc: Tom Lendacky <thomas.lenda...@amd.com> > Cc: Leif Lindholm <l...@nuviainc.com> > Cc: Sami Mujawar <sami.muja...@arm.com> > > Dov Murik (8): > OvmfPkg/AmdSev: use GenericQemuLoadImageLib in AmdSev builds > OvmfPkg: add library class BlobVerifierLib with null implementation > OvmfPkg: add BlobVerifierLibNull to DSC > ArmVirtPkg: add BlobVerifierLibNull to DSC > OvmfPkg/QemuKernelLoaderFsDxe: call VerifyBlob after fetch from fw_cfg > OvmfPkg/AmdSev/SecretPei: build hob for full page > OvmfPkg: add BlobVerifierLibSevHashes > OvmfPkg/AmdSev: Enforce hash verification of kernel blobs > > James Bottomley (3): > OvmfPkg/AmdSev/SecretDxe: fix header comment to generic naming > OvmfPkg: PlatformBootManagerLibGrub: Allow executing kernel via fw_cfg > OvmfPkg/AmdSev: reserve MEMFD space for for firmware config hashes > > OvmfPkg/OvmfPkg.dec > | 9 + > ArmVirtPkg/ArmVirtQemu.dsc > | 5 +- > ArmVirtPkg/ArmVirtQemuKernel.dsc > | 5 +- > OvmfPkg/AmdSev/AmdSevX64.dsc > | 9 +- > OvmfPkg/OvmfPkgIa32.dsc > | 5 +- > OvmfPkg/OvmfPkgIa32X64.dsc > | 5 +- > OvmfPkg/OvmfPkgX64.dsc > | 5 +- > OvmfPkg/AmdSev/AmdSevX64.fdf > | 5 +- > OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf > | 24 +++ > OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf > | 37 ++++ > OvmfPkg/Library/PlatformBootManagerLibGrub/PlatformBootManagerLibGrub.inf > | 2 + > OvmfPkg/ResetVector/ResetVector.inf > | 2 + > OvmfPkg/Include/Library/BlobVerifierLib.h > | 38 ++++ > OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.h > | 11 ++ > OvmfPkg/AmdSev/SecretDxe/SecretDxe.c > | 2 +- > OvmfPkg/AmdSev/SecretPei/SecretPei.c > | 3 +- > OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c > | 33 ++++ > OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c > | 200 ++++++++++++++++++++ > OvmfPkg/Library/PlatformBootManagerLibGrub/BdsPlatform.c > | 5 + > OvmfPkg/Library/{PlatformBootManagerLib => > PlatformBootManagerLibGrub}/QemuKernel.c | 0 > OvmfPkg/QemuKernelLoaderFsDxe/QemuKernelLoaderFsDxe.c > | 9 + > OvmfPkg/ResetVector/Ia16/ResetVectorVtf0.asm > | 20 ++ > OvmfPkg/ResetVector/ResetVector.nasmb > | 2 + > 23 files changed, 426 insertions(+), 10 deletions(-) > create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibNull.inf > create mode 100644 > OvmfPkg/Library/BlobVerifierLib/BlobVerifierLibSevHashes.inf > create mode 100644 OvmfPkg/Include/Library/BlobVerifierLib.h > create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierNull.c > create mode 100644 OvmfPkg/Library/BlobVerifierLib/BlobVerifierSevHashes.c > copy OvmfPkg/Library/{PlatformBootManagerLib => > PlatformBootManagerLibGrub}/QemuKernel.c (100%) > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. 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