On 12/7/21 10:39, Zbigniew Jędrzejewski-Szmek wrote:

 If available, use
the TPM2 to additionally tie the password to local hardware. If the
user is removed, also remove that password from that storage.

During boot, if it is necessary to authenticate before the root file
system has been mounted, allow admin users to log in using the credentials
that were stored previously.
Is this being worked on? Do you have any references?
Latest systemd versions have been getting some support for the low-level
parts, i.e. the low-level encrypted-secret storage. But we're missing the
upper parts, i.e. how to actually use and update the passwords. I didn't
even mention this, because we don't have a comprehensive story yet.

A scenario that wasn't mentioned here yet is using a disk from a failed system: either moving it to another system, or even simply accessing the data. If the credentials (including the LUKS encryption key/password) are protected by TPM2, it may effectively prevent any further access. It would be useful if any such new scheme avoided that.

In enterprise system, there usually is a backup decryption key, accessible to the enterprise admins. I am not sure what would be appropriate for single-user systems: some sort of install-time rescue passphrase [1] perhaps, that the user would write down and safely store [2]?

[1] https://xkcd.com/936/

[2] conveniently stored next to the rubber hose so that the attackers could forgo its use and type the rescue passphrase themselves. https://xkcd.com/538/