126 lines
4 KiB
Markdown
126 lines
4 KiB
Markdown
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# LUKS-Encrypted File Systems {#sec-luks-file-systems}
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NixOS supports file systems that are encrypted using *LUKS* (Linux
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Unified Key Setup). For example, here is how you create an encrypted
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Ext4 file system on the device
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`/dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d`:
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```ShellSession
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# cryptsetup luksFormat /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d
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WARNING!
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========
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This will overwrite data on /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d irrevocably.
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Are you sure? (Type uppercase yes): YES
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Enter LUKS passphrase: ***
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Verify passphrase: ***
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# cryptsetup luksOpen /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d crypted
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Enter passphrase for /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d: ***
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# mkfs.ext4 /dev/mapper/crypted
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```
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The LUKS volume should be automatically picked up by
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`nixos-generate-config`, but you might want to verify that your
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`hardware-configuration.nix` looks correct. To manually ensure that the
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system is automatically mounted at boot time as `/`, add the following
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to `configuration.nix`:
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```nix
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{
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boot.initrd.luks.devices.crypted.device = "/dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d";
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fileSystems."/".device = "/dev/mapper/crypted";
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}
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```
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Should grub be used as bootloader, and `/boot` is located on an
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encrypted partition, it is necessary to add the following grub option:
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```nix
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{
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boot.loader.grub.enableCryptodisk = true;
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}
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```
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## FIDO2 {#sec-luks-file-systems-fido2}
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NixOS also supports unlocking your LUKS-Encrypted file system using a FIDO2
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compatible token.
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### Without systemd in initrd {#sec-luks-file-systems-fido2-legacy}
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In the following example, we will create a new
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FIDO2 credential and add it as a new key to our existing device
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`/dev/sda2`:
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```ShellSession
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# export FIDO2_LABEL="/dev/sda2 @ $HOSTNAME"
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# fido2luks credential "$FIDO2_LABEL"
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f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7
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# fido2luks -i add-key /dev/sda2 f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7
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Password:
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Password (again):
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Old password:
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Old password (again):
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Added to key to device /dev/sda2, slot: 2
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```
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To ensure that this file system is decrypted using the FIDO2 compatible
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key, add the following to `configuration.nix`:
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```nix
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{
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boot.initrd.luks.fido2Support = true;
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boot.initrd.luks.devices."/dev/sda2".fido2.credential = "f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7";
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}
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```
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You can also use the FIDO2 passwordless setup, but for security reasons,
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you might want to enable it only when your device is PIN protected, such
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as [Trezor](https://trezor.io/).
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```nix
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{
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boot.initrd.luks.devices."/dev/sda2".fido2.passwordLess = true;
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}
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```
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### systemd Stage 1 {#sec-luks-file-systems-fido2-systemd}
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If systemd stage 1 is enabled, it handles unlocking of LUKS-encrypted volumes
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during boot. The following example enables systemd stage1 and adds support for
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unlocking the existing LUKS2 volume `root` using any enrolled FIDO2 compatible
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tokens.
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```nix
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{
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boot.initrd = {
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luks.devices.root = {
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crypttabExtraOpts = [ "fido2-device=auto" ];
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device = "/dev/sda2";
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};
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systemd.enable = true;
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};
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}
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```
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All tokens that should be used for unlocking the LUKS2-encrypted volume must
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first be enrolled using [systemd-cryptenroll](https://www.freedesktop.org/software/systemd/man/systemd-cryptenroll.html).
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In the following example, a new key slot for the first discovered token is
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added to the LUKS volume.
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```ShellSession
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# systemd-cryptenroll --fido2-device=auto /dev/sda2
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```
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Existing key slots are left intact, unless `--wipe-slot=` is specified. It is
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recommened to add a recovery key that should be stored in a secure physical
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location and can be entered wherever a password would be entered.
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```ShellSession
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# systemd-cryptenroll --recovery-key /dev/sda2
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```
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