5 ms·

> [...] almost nobody on Linux has been fool enough to make use of the TPM. Can you elaborate as to what is foolish about using a TPM?

ghostpepper 4y ago
Not the OP but just anecdotally, last time I looked into enabling secure boot on my X1 Carbon there was an advisory from Lenovo that enrolling your own keys made it possible to brick the machine https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Carbon_(Gen_7) https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Carbon_(...
- privacyking 4y ago
  That's only if you fail to enroll the Lenovo hardware firmware images
  - ghostpepper 4y ago
    Can you link to a doc explaining how to do that? I'm not even sure what it means to enrol a firmware image. I'd love to finally get this working.
    - LoganDark 4y ago
      I think they're referring to the BIOS itself, since even that needs to be signed and verified.
      - mjg59 4y ago
        It does, but it's not signed with the UEFI Secure Boot keys (Boot Guard has its own mechanism that's burned into chipset fuses, you can't re-key it)
    - privacyking 4y ago
      https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot#Microsoft_Windows https://wiki.archlinux.org/title/Unified_Extensible_Firmware... It's referring to dual booting windows but the same principles apply.
- mjg59 4y ago
  That's related to Secure Boot, not the TPM
michaelt 4y ago
In practice you have to enrol your own MOK if you want to use the nvidia drivers, or v4l2-loopback, or virtualbox, or a bunch of other things - so unlike on Windows, it doesn't give you any great OS integrity benefits. You want those modules signed by someone like Canonical, so you don't have to mess around with a MOK? If you use Ubuntu Core they'll be happy to - for about $100,000 per year per module. Automatically unlocking hard drive encryption is less secure than just typing in a password at boot. No OS-independent way of confirming the user's presence means it's less secure than a Yubikey. No iphone-style activation lock, so it's useless as a theft deterrent. No xbox-style main memory or system bus encryption, so no protection against evil maid attacks. Too slow for servers to offload SSL or disk encryption to - so all the important keys end up being held in memory anyway. The spec and interface are complicated as hell, so you know there's no chance this stuff is bug-free. You want a command line tool? We've got 99 command line tools. Literally. The foundation of its security is the code of your system's BIOS, which we all know is some of the shittiest code out there. So the TPM offers a hair-trigger system that'll destroy all your data if your BIOS vendor messes up and miscalculates a PCR value. The security benefits you get in return are pretty minor.
- cryptonector 4y ago
  The MOK thing is secure boot, not TPM related. You can have arbitrarily complex TPM authorization policies for unlocking storage keys. You can have it be that the loaded firmwares and OS are trusted and (or or) you have to enter in a passphrase that only the TPM can verify, and/or you can have a recovery mechanism so that if some firmware got updated you could use a smartcard or whatever to authorize moving on anyways. So, while OSes that support TPMs for storage key recovery generally have -as you say- hair-trigger policies, that's not TPM's fault but the OS's, for they could develop much more interesting policies.
  - nextaccountic 4y ago
    How to do those things in Linux?
    - 4y ago
hulitu 4y ago
> Can you elaborate as to what is foolish about using a TPM? Another backdoored closed piece of hardware ?

ghostpepper 4y ago

Not the OP but just anecdotally, last time I looked into enabling secure boot on my X1 Carbon there was an advisory from Lenovo that enrolling your own keys made it possible to brick the machine https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Carbon_(Gen_7) https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Carbon_(...

privacyking 4y ago
That's only if you fail to enroll the Lenovo hardware firmware images
- ghostpepper 4y ago
  Can you link to a doc explaining how to do that? I'm not even sure what it means to enrol a firmware image. I'd love to finally get this working.
  - LoganDark 4y ago
    I think they're referring to the BIOS itself, since even that needs to be signed and verified.
    - mjg59 4y ago
      It does, but it's not signed with the UEFI Secure Boot keys (Boot Guard has its own mechanism that's burned into chipset fuses, you can't re-key it)
  - privacyking 4y ago
    https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot#Microsoft_Windows https://wiki.archlinux.org/title/Unified_Extensible_Firmware... It's referring to dual booting windows but the same principles apply.
mjg59 4y ago
That's related to Secure Boot, not the TPM

michaelt 4y ago

In practice you have to enrol your own MOK if you want to use the nvidia drivers, or v4l2-loopback, or virtualbox, or a bunch of other things - so unlike on Windows, it doesn't give you any great OS integrity benefits. You want those modules signed by someone like Canonical, so you don't have to mess around with a MOK? If you use Ubuntu Core they'll be happy to - for about $100,000 per year per module. Automatically unlocking hard drive encryption is less secure than just typing in a password at boot. No OS-independent way of confirming the user's presence means it's less secure than a Yubikey. No iphone-style activation lock, so it's useless as a theft deterrent. No xbox-style main memory or system bus encryption, so no protection against evil maid attacks. Too slow for servers to offload SSL or disk encryption to - so all the important keys end up being held in memory anyway. The spec and interface are complicated as hell, so you know there's no chance this stuff is bug-free. You want a command line tool? We've got 99 command line tools. Literally. The foundation of its security is the code of your system's BIOS, which we all know is some of the shittiest code out there. So the TPM offers a hair-trigger system that'll destroy all your data if your BIOS vendor messes up and miscalculates a PCR value. The security benefits you get in return are pretty minor.

cryptonector 4y ago
The MOK thing is secure boot, not TPM related. You can have arbitrarily complex TPM authorization policies for unlocking storage keys. You can have it be that the loaded firmwares and OS are trusted and (or or) you have to enter in a passphrase that only the TPM can verify, and/or you can have a recovery mechanism so that if some firmware got updated you could use a smartcard or whatever to authorize moving on anyways. So, while OSes that support TPMs for storage key recovery generally have -as you say- hair-trigger policies, that's not TPM's fault but the OS's, for they could develop much more interesting policies.
- nextaccountic 4y ago
  How to do those things in Linux?
  - 4y ago

hulitu 4y ago

> Can you elaborate as to what is foolish about using a TPM? Another backdoored closed piece of hardware ?