Re: [edk2-devel] measurement to command-line/initrd for loading kernel via -kernel option

["Min Xu" <min.m.xu@intel.com>]

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.xu@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.apalodimas@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?

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. 
For direct boot, TryRunningQemuKernel() now measures kernel image (in CoreLoadImage). Shall it also measure cmd-line/initrd in the same time?

Thanks
Min