[systemd-devel] Issues supporting systems with and without TPM and firmware TPM (was Re: Handle device node timeout?)

[Lennart Poettering]

On Di, 16.04.24 15:02, Mikko Rapeli (mikko.rapeli at linaro.org) wrote:

> Hi,
>
> On Mon, Apr 15, 2024 at 05:41:00PM +0200, Lennart Poettering wrote:
> > Would be good to have that with systemd.log_target=debug, to see if
> > tpm2.target even gets enqueued.
>
> Here is the verbose log:
>
> https://people.linaro.org/~mikko.rapeli/systemd_255_tpm2_target_qemu_swtpm_boot_encryption_failure.txt

So that shows that tpm2.target is only enqueued once the /dev/tpmrm0
device actually shows up. But that makes it useless. The idea is that
the target is already enqueued when during very early setup in
systemd-tpm2-generator we come to the conclusion that "yes, a tpm2
device has not been found and set up by Linux yet, but the firmware
indicates there is one, hence let's schedule a job for it, that
everything can sync on". But this determination never happened
here, tpm2.target was never enqueued, hence never acted as a
synchronization milestone.

(As a temporary hack you can *force* systemd-tpm2-generator to assume
that a TPM device will show up via systemd.tpm2_wait=1 on the kernel
cmdline, and thus enqueue tpm2.target. But that's only suitable as
local hack: we should be able to determine all this automatically
based on firmware properties, see below.)

> System is qemu arm64 with UEFI / ARM System Ready compatible firmware,
> secure boot and TPM2 device via swtpm.

So this firmware implements UEFI and ACPI? As indication whether the
firmware supports TPM2, we check for the existance of the
/sys/firmware/acpi/tables/TPM2 ACPI table. Does that exist for you?

See src/share/efi-api.c, function efi_has_tpm2().

Do you have /sys/kernel/security/tpm0/binary_bios_measurements?

> systemd-tpm2-setup-early.service: ConditionSecurity=measured-uki
> failed.

So this suggests you haven't booted the system with a UKI or that your
firmware doesn#t actually do TPM.

Or in other words: ConditionSecurity=measured-uki will only hold if
the aforementioned ACPI table exists *and* the StubPcrKernelImage EFI
variable is found to be set.

Lennart

--
Lennart Poettering, Berlin