4 ms·

The TPM isn't involved in secure boot. Could you provide some more details about what went wrong?

• lostmsu 3y ago
  It is about full disk encryption with automatic unlock during boot. One needs to make TPM dependent on a successful secure boot to allow access to decryption. The boot completes no problem, but the TPM entry that controls access needs to be manually recreated with each new kernel update. See https://gist.github.com/jdoss/777e8b52c8d88eb87467935769c98a95#enroll-your-encrypted-volumes https://gist.github.com/jdoss/777e8b52c8d88eb87467935769c98a... , the bit "then auto volume decryption on your next reboot will fail". This makes sense.
  • mjg59 3y ago
    Using anything other than PCR 7 is going to make it very fragile, yes - I have no idea why that doc is recommending using PCR 4 as well.
    • lostmsu 3y ago
      To defend against an attacker with physical access to an offline machine you need to verify anything that the attacker can overwrite without the encryption key. Aren't bootloader and kernel on the writable unencrypted partition?
      • mjg59 3y ago
        If you have secure boot enabled, how does the attacker replace the kernel or bootloader?
        • lostmsu 3y ago
          Pull the drive out, insert it into his machine, replace, then insert it back.
          • mjg59 3y ago
            And now the signature doesn't match, so the system doesn't boot
            • lostmsu 3y ago
              Which signature?
              • mjg59 3y ago
                The signature that's validated by secure boot. If you don't have secure boot turned on then there's no point in verifying PCR 7, because all PCR 7 contains is the secure boot data.