If someone wants to seal to a PCR
explicitly to prevent booting rescue, the PCR is likely to
extend differently during install.
Leave the volume sealed to the tpm without any PCRs until first boot.
Then wipe the bindings without PCR specified, and seal according to user preferred values.
This allows a user to opt into pcrs if they understand what they are doing.
Some PCRs are sensitive to firmware updates and some are sensitive to boot loader, kernel, boot config, or initramfs. All of these are an opportunity for an unsuspecting update to remove access to the boot volume. There are update processes that can be put into place to make this work,
but it is up to the OS update process to address that, and
OS update processes are likely not to address that at this time.
Provide mechanism for administrator to place a custom
key for potential interactive recovery into
/var/lib/confluent/private/os/<profile>/pending/luks.key
If not provided, generate a unique one for each install.
Either way, persist the key in /etc/confluent/luks.key, to
facilitate later resealing if the user wants (clevis nor systemd
prior to 256 supports unlock via TPM2, so keyfile is required
for now).
Migrating to otherwise escrowed passphrases and/or sealing to
specific TPMs will be left to operators and/or third parties.
Jarrod Johnson