On September 19, 2022 2:59 PM, Ard Biesheuvel wrote: > On Mon, 19 Sept 2022 at 04:13, Xu, Min M <min.m...@intel.com> wrote: > > > > On September 18, 2022 8:52 PM, Ard Biesheuvel wrote: > > > Hello Min Xu, > > > > > > On Sat, 17 Sept 2022 at 04:53, Xu, Min M <min.m...@intel.com> wrote: > > > > > > > > Hi, Ard > > > > > > > > I am checking the measurement behavior when loading the kernel via > > > > the > > > QEMU -kernel option. I find it is implemented by below 2 driver/lib: > > > > > > > > - OvmfPkg/QemuKernelLoaderFsDxe > > > > > > > > This is a separate DXE driver that exposes the virtual > > > > SimpleFileSystem > > > implementation that carries the kernel and initrd passed via the > > > QEMU command line. > > > > > > > > - OvmfPkg/Library/X86QemuLoadImageLib > > > > > > > > This is the library that consumes above driver and call > > > LoadImage/StartImage so that the kernel image gets authenticated > > > and/or measured. > > > > > > > > See https://edk2.groups.io/g/devel/message/55381 > > > > > > > > > > > > > > > > I have some questions about the implementation need your help. > > > > > > > > 2. Kernel image is authenticated and/or measured in LoadImage. I > > > > am > > > wondering if “command line” is measured as well? “Command line” can > > > be treated as an external input and in my opinion it should be measured > too. > > > > > > > > 3. The same question to initrd. Is it measured? > > > > > > > > > > The initrd is measured by the EFI stub in Linux, and we are > > > currently adding measurement of the load options to that as well: > > > https://lore.kernel.org/all/20220916081441.1993492-2- > > > ilias.apalodi...@linaro.org/ > > > > > > The initrd is Linux specific in any case, so there, the Linux OS > > > loader is a natural place to take care of this. The load options are > > > being added because of the oversight in the TCG spec, which only > > > covers load options if they are part of a Boot#### option, but > > > between > > > LoadImage() and StartImage, you can pass any load options you want > > > via the loaded image protocol, so it needs to be measured as well. > > > > > Thanks Ard for the explanation. > > I was told that in grub boot cmd-line/initrd will be measured as well. So my > question is that will they be measured twice? One in grub.efi, the other in > efi- > stub? > > > > The EFI stub may be the only OS loader, so the EFI stub should measure the > command line and the initrd. > > Whether or not a previous loader stage exists that may or may not measure > the same pieces is not for the EFI stub to reason about. And in any case, > measuring the same thing twice is much less of an issue than not measuring it > at all. > > > My understanding is that the loader should take the responsibility to do the > measurement. > > For grub boot, grub.efi is the loader so it measures kernel-image/cmd- > line/initrd. > > If the EFI stub is invoked, the EFI stub is the OS loader. We should not be > relying on the presence of absence of GRUB (or shim) in the boot chain. > > > For direct boot, TryRunningQemuKernel() now measures kernel image (in > CoreLoadImage). Shall it also measure cmd-line/initrd in the same time? > > > > No, I don't think it should. This is why we are adding this to the EFI stub > instead. > > If we measure the initrd and command line in the EFI stub, we don't have to > measure it anywhere else, and we can use any generic EFI loader on a > measured boot system. > Ard, thanks for the explanation. The reason why I am checking the measurement of cmd-line and initrd is that I am thinking how to measure cmd-line and initrd in TDVF with the EFI_CC_MEASUREMENT_PROTOCOL which is defined in MdePkg/Include/Protocol/CcMeasurement.h. Actually EFI_CC_MEASUREMENT_PROTOCOL is designed for the Confidential Computing guest to support measurement.
I check the patch in https://lore.kernel.org/all/20220916081441.1993492-1-ilias.apalodi...@linaro.org/. It supports the EFI_TCG2_PROTOCOL. I think it can also support EFI_CC_MEASUREMENT_PROTOCOL like below: efi_tcg2_protocol_t *tcg2 = NULL; efi_cc_protocol_t *cc = NULL; efi_bs_call(locate_protocol, &tcg2_guild, NULL, (void**)&tcg2); efi_bs_call(locate_protocol, &cc_guild, NULL, (void**)&cc); if (tcg2) { do_tcg2_measurement (); } else if (cc) { cc-> MapPcrToMrIndex (); // because there is a map between TPM-PCR index to CC-MeasureRegister Index. do_cc_measurement (); } I am wondering when your 2 patches would be accepted and merged so that I can submit my patch based on yours. Thanks Min -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#93975): https://edk2.groups.io/g/devel/message/93975 Mute This Topic: https://groups.io/mt/93737108/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
