Hi Ilias,
On Tue, 13 Jun 2023 at 06:48, Ilias Apalodimas ilias.apalodimas@linaro.org wrote:
On Mon, Jun 12, 2023 at 10:17:28PM +0100, Simon Glass wrote:
Hi Ilias,
On Wed, 7 Jun 2023 at 10:18, Ilias Apalodimas ilias.apalodimas@linaro.org wrote:
Currently we only read the pcr updates once on test_tpm2_pcr_read(). It turns out that the tpm init sequence of force_init() which consists of:
- tpm2 init
- tpm2 startup TPM2_SU_CLEAR
- tpm2 self_test full
- tpm2 clear TPM2_RH_LOCKOUT
also counts as an update. Running this in the console verifies the update bump => tpm2 init => tpm2 startup TPM2_SU_CLEAR => tpm2 self_test full => tpm pcr_read 10 $loadaddr PCR #10 content (28 known updates): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 => tpm2 clear TPM2_RH_LOCKOUT => tpm pcr_read 10 $loadaddr PCR #10 content (29 known updates): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>
With the recent changes of replacing 'tpm2 init' with 'tpm2 autostart' we end up always running the full init. The reason is 'tpm init' returns -EBUSY if the tpm is already open, while 'tpm autostart' handles ths gracefully and continues with the initialization. It's worth noting that this won't affect the device functionality at all since retriggering the startup sequence and selftests has no side effects.
This may be true for some TPMs.
The responses to the startup command are described by the spec, so unless the device isn't a standard TPM, this should be safe
Yes, that could be the problem.
Instead of relying on the initial value, reread the 'known updates' just before updating the PCR to ensure we read the correct values before testing
Signed-off-by: Ilias Apalodimas ilias.apalodimas@linaro.org
Changes since v1:
- new patch to fix the python testing failures
test/py/tests/test_tpm2.py | 6 ++++++ 1 file changed, 6 insertions(+)
Reviewed-by: Simon Glass sjg@chromium.org
BTW this is an example of why I still want to be able to just init the TPM to a basic level. Here we see that autostart changes the PCRs.
It doesnt change the PCRs. That code is checking how many commands have been sent to the TPM in total. In the previous version of the code 'tpm init' would return -EBUSY and we would never re-run the next commands. The new command returns 0 and as a result we end up running the TPM2_RH_LOCKOUT again.
OK.
Regards, Simon