Re: [PATCH v5 0/6] tpm: Support boot measurements

Joel Stanley
2023-02-22T05:36:30Z

On Thu, 2 Feb 2023 at 17:08, Eddie James <eajames@linux.ibm.com> wrote:
>
> This series adds support for measuring the boot images more generically
> than the existing EFI support. Several EFI functions have been moved to
> the TPM layer. The series includes optional measurement from the bootm
> command.
> A new test case has been added for the bootm measurement to test the new
> path, and the sandbox TPM2 driver has been updated to support this use
> case.
> This series is based on Ilias' auto-startup series:
> https://lore.kernel.org/u-boot/20230126081844.591148-1-ilias.apalodimas@linaro.org/

Nice work Eddie. It looks like you're closing in on the issues Ilias
and Simon have.

I did some testing and found some missing dependencies from running
'make check':

sandbox_spl: +make O=/home/joel/dev/u-boot/upstream/build-sandbox_spl
-s sandbox_spl_defconfig
+make O=/home/joel/dev/u-boot/upstream/build-sandbox_spl -s -j8
/usr/bin/ld: warning: test/overlay/test-fdt-overlay-stacked.dtb.o:
missing .note.GNU-stack section implies executable stack
/usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in
a future version of the linker
/usr/bin/ld: /tmp/cc8cNroX.ltrans22.ltrans.o:(.data.rel+0x440):
undefined reference to `do_ut_measurement'
collect2: error: ld returned 1 exit status
make[2]: *** [/home/joel/dev/u-boot/upstream/Makefile:1752: u-boot] Error 1

There's a few variants of the sandbox defconfig. I'm not sure if we
want to exclude the measurement code from those configs, or add it to
the configs.

When fixing them up to add CONFIG_MEASURED_BOOT=y we still fail to link:

sandbox_spl: +make O=/home/joel/dev/u-boot/upstream/build-sandbox_spl
-s sandbox_spl_defconfig
+make O=/home/joel/dev/u-boot/upstream/build-sandbox_spl -s -j8
/usr/bin/ld: warning: test/overlay/test-fdt-overlay-stacked.dtb.o:
missing .note.GNU-stack section implies executable stack
/usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in
a future version of the linker
/usr/bin/ld: /tmp/ccRuOSFi.ltrans17.ltrans.o: in function `tcg2_create_digest':
/home/joel/dev/u-boot/upstream/build-sandbox_spl/../lib/tpm-v2.c:112:
undefined reference to `sha512_starts'
/usr/bin/ld: /home/joel/dev/u-boot/upstream/build-sandbox_spl/../lib/tpm-v2.c:113:
undefined reference to `sha512_update'
/usr/bin/ld: /home/joel/dev/u-boot/upstream/build-sandbox_spl/../lib/tpm-v2.c:114:
undefined reference to `sha512_finish'
/usr/bin/ld: /home/joel/dev/u-boot/upstream/build-sandbox_spl/../lib/tpm-v2.c:106:
undefined reference to `sha384_starts'
/usr/bin/ld: /home/joel/dev/u-boot/upstream/build-sandbox_spl/../lib/tpm-v2.c:107:
undefined reference to `sha384_update'
/usr/bin/ld: /home/joel/dev/u-boot/upstream/build-sandbox_spl/../lib/tpm-v2.c:108:
undefined reference to `sha384_finish'
collect2: error: ld returned 1 exit status

This sorted that out for me:

--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -411,6 +411,8 @@ config TPM
bool "Trusted Platform Module (TPM) Support"
depends on DM
imply DM_RNG
+ select SHA512
+ select SHA384

The tree I tested with is here:
https://github.com/shenki/u-boot/commits/measured-boot

Cheers,

Joel

>
> Changes since v4:
> - Remove tcg2_measure_event function and check for NULL data in
> tcg2_measure_data
> - Use tpm_auto_startup
> - Fix efi_tcg2.c compilation for removing tcg2_pcr_read function
> - Change PCR indexes for initrd and dtb
> - Drop u8 casting in measurement test
> - Use bullets in documentation
>
> Changes since v3:
> - Reordered headers
> - Refactored more of EFI code into common code
> Removed digest_info structure and instead used the common alg_to_mask
> and alg_to_len
> Improved event log parsing in common code to get it equivalent to EFI
> Common code now extends PCR if previous bootloader stage couldn't
> No need to allocate memory in the common code, so EFI copies the
> discovered buffer like it did before
> Rename efi measure_event function
>
> Changes since v2:
> - Add documentation.
> - Changed reserved memory address to the top of the RAM for sandbox dts.
> - Add measure state to booti and bootz.
> - Skip measurement for EFI images that should be measured
>
> Changes since v1:
> - Refactor TPM layer functions to allow EFI system to use them, and
> remove duplicate EFI functions.
> - Add test case
> - Drop #ifdefs for bootm
> - Add devicetree measurement config option
> - Update sandbox TPM driver
>
> Eddie James (6):
> tpm: Fix spelling for tpmu_ha union
> tpm: Support boot measurements
> bootm: Support boot measurement
> tpm: sandbox: Update for needed TPM2 capabilities
> test: Add sandbox TPM boot measurement
> doc: Add measured boot documentation
>
> arch/sandbox/dts/sandbox.dtsi | 14 +
> arch/sandbox/dts/test.dts | 13 +
> boot/Kconfig | 23 +
> boot/bootm.c | 70 +++
> cmd/booti.c | 1 +
> cmd/bootm.c | 2 +
> cmd/bootz.c | 1 +
> configs/sandbox_defconfig | 1 +
> doc/usage/index.rst | 1 +
> doc/usage/measured_boot.rst | 23 +
> drivers/tpm/tpm2_tis_sandbox.c | 100 +++-
> include/bootm.h | 2 +
> include/efi_tcg2.h | 44 --
> include/image.h | 1 +
> include/test/suites.h | 1 +
> include/tpm-v2.h | 246 +++++++-
> lib/efi_loader/efi_tcg2.c | 1010 +++-----------------------------
> lib/tpm-v2.c | 771 ++++++++++++++++++++++++
> test/boot/Makefile | 1 +
> test/boot/measurement.c | 66 +++
> test/cmd_ut.c | 2 +
> 21 files changed, 1383 insertions(+), 1010 deletions(-)
> create mode 100644 doc/usage/measured_boot.rst
> create mode 100644 test/boot/measurement.c
>
> --
> 2.31.1
>