[systemd-devel] Enrolling PCR11 does not work as expected

[Felix Rubio]

For what is explained on the the systemd-pcrphase.service(8) and 
comparing it to what I see in the log of the systemd services, there are 
three events in relation to this question:

systemd-pcrphase-initrd.service
[...]
[systemd-ask-password-console.service]
[...]
systemd-pcrphase-sysinit
systemd-pcrphase

This means that, indeed, running cryptenroll after the new kernel has 
booted will never provide the correct PCR registry for 11. But then... 
what options do I have? Do I need to choose between having PCRs 7 and 
14, so that I make sure that SB is up and running and all the certs from 
shim have not changed, or to have only PCR 11 so that I know that the 
UKI has not changed although SB can potentially be even disabled 
(please, correct me if wrong)?

Thank you!

Felix

On 2023-07-05 10:36, Lennart Poettering wrote:
> On Mi, 05.07.23 08:30, Felix Rubio (felix at kngnt.org) wrote:
> 
>> Hi everybody,
>> 
>> In my setup (sd-boot+UKI+LUKS) I am using PCRs 7+11+14 to unlock the 
>> LUKS
>> drive. Should I use only PCRs 7+14 everything works, but when I add 11 
>> I
>> need to provide the rescue password every single time I boot.
>> 
>> I have extracted the values of those PCRs using tpm2_pcrread in two
>> consecutive boots, and they are equal, so at least the issue is
>> reproducible.
>> 
>> To enroll the PCRs, after a new kernel (and, therefore, the UKI) has 
>> been
>> generated, I run the following command:
>> 
>> systemd-cryptenroll --wipe-slot=tpm2 --tpm2-device=auto 
>> --tpm2-pcrs=7+11+14
>> <device>
>> 
>> After reading the documentation on systemd-measure (that I am not 
>> using at
>> the moment): could it be that there are events added to PCR 11 after 
>> the
>> unlocking has happened, so that I am enrolling the wrong PCR value?
>> Otherwise... what am I doing wrong?
> 
> We mesaure the "boot phase" into PCR 11 too. See
> systemd-pcrphase.service(8) for details.
> 
> Generally the assumption is that PCR 11 is used for signed PCR
> policies, i.e. under vendor control.
> 
> Lennart
> 
> --
> Lennart Poettering, Berlin