# fido2luks [![Crates.io Version](https://img.shields.io/crates/v/fido2luks.svg)](https://crates.io/crates/fido2luks) This will allow you to unlock your LUKS encrypted disk with an FIDO2 compatible key. Note: This has only been tested under Fedora 31, [Ubuntu 20.04](initramfs-tools/), [NixOS](https://nixos.org/nixos/manual/#sec-luks-file-systems-fido2) using a Solo Key, Trezor Model T, YubiKey(fw >= [5.2.3](https://support.yubico.com/hc/en-us/articles/360016649319-YubiKey-5-2-3-Enhancements-to-FIDO-2-Support)) ## Setup ### Prerequisites ``` dnf install clang cargo cryptsetup-devel -y ``` ### Device ``` git clone https://github.com/shimunn/fido2luks.git && cd fido2luks # Alternativly cargo build --release && sudo cp target/release/fido2luks /usr/bin/ sudo -E cargo install -f --path . --root /usr # Copy template cp dracut/96luks-2fa/fido2luks.conf /etc/ # Name is optional but useful if your authenticator has a display echo FIDO2LUKS_CREDENTIAL_ID=$(fido2luks credential [NAME]) >> /etc/fido2luks.conf # Load config into env set -a . /etc/fido2luks.conf # Repeat for each luks volume # You can also use the `--token` flag when using LUKS2 which will then store the credential in the LUKS header, # enabling you to use `fido2luks open-token` without passing a credential as parameter sudo -E fido2luks -i add-key /dev/disk/by-uuid/ # Test(only works if the luks container isn't active) sudo -E fido2luks -i open /dev/disk/by-uuid/ luks- ``` ### Dracut ``` cd dracut sudo make install ``` ### Grub Add `rd.luks.2fa=:` to `GRUB_CMDLINE_LINUX` in /etc/default/grub Note: This is only required for your root disk, systemd will try to unlock all other LUKS partions using the same key if you added it using `fido2luks add-key` ``` grub2-mkconfig > /boot/grub2/grub.cfg ``` I'd also recommend to copy the executable onto /boot so that it is accessible in case you have to access your disk from a rescue system ``` mkdir /boot/fido2luks/ cp /usr/bin/fido2luks /boot/fido2luks/ cp /etc/fido2luks.conf /boot/fido2luks/ ``` ## Testing Just reboot and see if it works, if that's the case you should remove your old less secure password from your LUKS header: ``` # Recommend in case you lose your authenticator, store this backupfile somewhere safe cryptsetup luksHeaderBackup /dev/disk/by-uuid/ --header-backup-file luks_backup_ # There is no turning back if you mess this up, make sure you made a backup # You can also pass `--token` if you're using LUKS2 which will then store the credential in the LUKS header, # which will enable you to use `fido2luks open-token` without passing a credential as parameter fido2luks -i add-key --exclusive /dev/disk/by-uuid/ ``` ## Addtional settings ### Password less Remove your previous secret as described in the next section, in case you've already added one. Open `/etc/fido2luks.conf` and replace `FIDO2LUKS_SALT=Ask` with `FIDO2LUKS_SALT=string:` but be warned that this password will be included to into your initramfs. Import the new config into env: ``` set -a . /etc/fido2luks.conf ``` Then add the new secret to each device and update dracut afterwards `dracut -f` ### Multiple keys Additional/backup keys are supported, Multiple fido2luks credentials can be added to your /etc/fido2luks.conf file. Credential tokens are comma separated. ``` FIDO2LUKS_CREDENTIAL_ID=,, ``` ## Removal Remove `rd.luks.2fa` from `GRUB_CMDLINE_LINUX` in /etc/default/grub ``` set -a . fido2luks.conf sudo -E fido2luks -i replace-key /dev/disk/by-uuid/ sudo rm -rf /usr/lib/dracut/modules.d/96luks-2fa /etc/dracut.conf.d/luks-2fa.conf /etc/fido2luks.conf ``` ## Theory of operation fido2luks builds on two basic building blocks, LUKS as an abstraction over linux disk encryption and and the FIDO2 extension [`hmac-secret`](https://fidoalliance.org/specs/fido-v2.0-rd-20180702/fido-client-to-authenticator-protocol-v2.0-rd-20180702.html#sctn-hmac-secret-extension). The `hmac-secret` extension allows for an secret to be dervied on the FIDO2 device from two inputs, the user supplied salt/password/keyfile and another secret contained within the FID2 device. The output of the `hmac-secret` function will then be used to decrypt the LUKS header which in turn is used to decrypt the disk. ``` +-------------------------------------------------------------------------------+ | | | +-----------------------------------------+ | | | FIDO2 device | | | | | | | | | | +-------+--------+ +------+ | +---------------+ | | +------------------------+ | Salt/Password +-> |sha256+------------------------> | | | v | LUKS header | +----------------+ +------+ | | | | | | +---------------+ | | | | +--------+ +------------------------+--------> |Disk master key| | | sha256_hmac +---------> | sha256 +-------> | Keyslot 1 | +---------------+ +----------------+ | +----------+ | | | +--------+ +------------------------+ | FIDO credential+---------------> |Credential| +----> | | | | Keyslot 2 | +----------------+ | |secret | | | | +------------------------+ | +----------+ +---------------+ | | | | | +-----------------------------------------+ ``` Since all these components build upon each other losing or damaging just one of them will render the disk undecryptable, it's threfore of paramount importance to backup the LUKS header and ideally set an backup password or utilise more than one FIDO2 device. Each additional credential and password combination will require it's own LUKS keyslot since the credential secret is randomly generated for each new credential and will thus result in a completly different secret. ## License Licensed under * Mozilla Public License 2.0, ([LICENSE-MPL](LICENSE-MPL) or https://www.mozilla.org/en-US/MPL/2.0/) ### Contribution Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the MPL 2.0 license, shall be licensed as above, without any additional terms or conditions.