faulTPM paper (https://arxiv.org/pdf/2304.14717v1.pdf) deals mostly with Bitlocker and only mentions LUKS to note the differences.
The authors state:
With a passphrase, however, the same level of security that the passphrase-only protector offers is retained, thanks to the additional layer of encryption applied to the VMK before it is sealed by the TPM.
But it seems that the
VMK is Bitlocker-specific.
The abstract closes with:
Our results show that when an fTPM’s internal state is compromised, a TPM and PIN strategy for FDE is less secure than TPM-less protection with a reasonable passphrase.
The word "PIN" in the Bitlocker context being used interchangeably with passphrase ("enhanced PIN") making this harder to decipher.
AFAIK the LUKS-based FDE, at least by default (as is common i.e. during Ubuntu installation) is using TPM to store the keys.
Does this mean that the FDE/LUKS setup where users provide a passphrase on boot is defeated by
faulTPM, since the keys are stored in the TPM? Is there a way to use FDE/LUKS in a "TPM-less" mode with a passphrase only? If so would this provide sufficient defense against