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But is the storage hdd/ssd epoxied too? The ssh keys to do MITM are in cleartext on boot partition... FBI can put their box on your server's IP, and you'll happ

But is the storage hdd/ssd epoxied too? The ssh keys to do MITM are in cleartext on boot partition... FBI can put their box on your server's IP, and you'll happily connect, same fingerprint, and type unlock and passphrase.

mirimir 8y ago
Sorry. Wasn't thinking clearly. I guess that you'd need to embed the SSD(s) too. But I wonder if there's a way to reproducibly generate SSH key pairs from hardware IDs. That way, there'd be no keys stored in /boot, and they'd be generated at each boot. So only your hardware would have the right keys.
- auslander 8y ago
  This TPM guide describes TPM for LUKS. "PCR 0-7 Measured by BIOS" seems like HW fingerprint. https://github.com/morbitzer/linux-luks-tpm-boot https://github.com/morbitzer/linux-luks-tpm-boot If this thing works, there is no need for remote ssh FDE unlocking.
  - deleted 8y ago
    [deleted]
  - mirimir 8y ago
    Thanks. If I understand that correctly, the LUKS key is stored in the TPM. Which is protected by a password. So you boot into initramfs, and provide the password. And this could also work via dropbear. There'd still be an exposed dropbear SSH key in /boot. But it'd be the TPM that you're unlocking. And I assume that there are ways to verify the authenticity of the TPM via initramfs, before providing a password. Am I understanding that right? It does seem more complicated. Especially given that you don't have physical access to the server.
    - auslander 8y ago
      > .. the LUKS key is stored in the TPM. Which is protected by a password. Yup. Nope. The key is protected by TPM magic :). TPM measures stuff, then we put the key in TPM and seal it to PCRs 0-13 measurements (whole boot environment). At boot, TPM will allow tcsd daemon (part of initrd) to read LUKS key once, and only if all measurements match, this is as far as I got. End result is unlocked volume, without any passphrase prompts, neither on console nor via ssh.

mirimir 8y ago

Sorry. Wasn't thinking clearly. I guess that you'd need to embed the SSD(s) too. But I wonder if there's a way to reproducibly generate SSH key pairs from hardware IDs. That way, there'd be no keys stored in /boot, and they'd be generated at each boot. So only your hardware would have the right keys.

auslander 8y ago
This TPM guide describes TPM for LUKS. "PCR 0-7 Measured by BIOS" seems like HW fingerprint. https://github.com/morbitzer/linux-luks-tpm-boot https://github.com/morbitzer/linux-luks-tpm-boot If this thing works, there is no need for remote ssh FDE unlocking.
- deleted 8y ago
  [deleted]
- mirimir 8y ago
  Thanks. If I understand that correctly, the LUKS key is stored in the TPM. Which is protected by a password. So you boot into initramfs, and provide the password. And this could also work via dropbear. There'd still be an exposed dropbear SSH key in /boot. But it'd be the TPM that you're unlocking. And I assume that there are ways to verify the authenticity of the TPM via initramfs, before providing a password. Am I understanding that right? It does seem more complicated. Especially given that you don't have physical access to the server.
  - auslander 8y ago
    > .. the LUKS key is stored in the TPM. Which is protected by a password. Yup. Nope. The key is protected by TPM magic :). TPM measures stuff, then we put the key in TPM and seal it to PCRs 0-13 measurements (whole boot environment). At boot, TPM will allow tcsd daemon (part of initrd) to read LUKS key once, and only if all measurements match, this is as far as I got. End result is unlocked volume, without any passphrase prompts, neither on console nor via ssh.