Disk Encryption

It is possible to enable encryption for system disks at the OS level. As of this writing, only STATE and EPHEMERAL partitions can be encrypted. STATE contains the most sensitive node data: secrets and certs. EPHEMERAL partition may contain some sensitive workload data. Data is encrypted using LUKS2, which is provided by the Linux kernel modules and cryptsetup utility. The operating system will run additional setup steps when encryption is enabled.

If the disk encryption is enabled for the STATE partition, the system will:

  • Save STATE encryption config as JSON in the META partition.
  • Before mounting the STATE partition, load encryption configs either from the machine config or from the META partition. Note that the machine config is always preferred over the META one.
  • Before mounting the STATE partition, format and encrypt it. This occurs only if the STATE partition is empty and has no filesystem.

If the disk encryption is enabled for the EPHEMERAL partition, the system will:

  • Get the encryption config from the machine config.
  • Before mounting the EPHEMERAL partition, encrypt and format it. This occurs only if the EPHEMERAL partition is empty and has no filesystem.

Configuration

Right now this encryption is disabled by default. To enable disk encryption you should modify the machine configuration with the following options:

machine:
  ...
  systemDisksEncryption:
    ephemeral:
      keys:
        - nodeID:
          keySlot: 0
    state:
      keys:
        - nodeID:
          keySlot: 0

Encryption Keys

Note: What the LUKS2 docs call "keys" are, in reality, a passphrase. When this passphrase is added, LUKS2 runs argon2 to create an actual key from that passphrase.

LUKS2 supports up to 32 encryption keys and it is possible to specify all of them in the machine configuration. Talos always tries to sync the keys list defined in the machine config with the actual keys defined for the LUKS2 partition. So if you update the keys list you should have at least one key that is not changed to be used for keys management.

When you define a key you should specify the key kind and the keySlot:

machine:
  ...
  state:
    keys:
      - nodeID: # key kind
        keySlot: 1

  ephemeral:
    keys:
      - static:
          passphrase: supersecret
        keySlot: 0

Take a note that key order does not play any role on which key slot is used. Every key must always have a slot defined.

Encryption Key Kinds

Talos supports two kinds of keys:

  • nodeID which is generated using the node UUID and the partition label (note that if the node UUID is not really random it will fail the entropy check).
  • static which you define right in the configuration.

Note: Use static keys only if your STATE partition is encrypted and only for the EPHEMERAL partition. For the STATE partition it will be stored in the META partition, which is not encrypted.

Key Rotation

It is necessary to do talosctl apply-config a couple of times to rotate keys, since there is a need to always maintain a single working key while changing the other keys around it.

So, for example, first add a new key:

machine:
  ...
  ephemeral:
    keys:
      - static:
          passphrase: oldkey
        keySlot: 0
      - static:
          passphrase: newkey
        keySlot: 1
  ...

Run:

talosctl apply-config -n <node> -f config.yaml

Then remove the old key:

machine:
  ...
  ephemeral:
    keys:
      - static:
          passphrase: newkey
        keySlot: 1
  ...

Run:

talosctl apply-config -n <node> -f config.yaml

Going from Unencrypted to Encrypted and Vice Versa

Ephemeral Partition

There is no in-place encryption support for the partitions right now, so to avoid losing any data only empty partitions can be encrypted.

As such, migration from unencrypted to encrypted needs some additional handling, especially around explicitly wiping partitions.

  • apply-config should be called with --on-reboot flag.
  • Partition should be wiped after apply-config, but before the reboot.

Edit your machine config and add the encryption configuration:

vim config.yaml

Apply the configuration with --on-reboot flag:

talosctl apply-config -f config.yaml -n <node ip> --on-reboot

Wipe the partition you're going to encrypt:

talosctl reset --system-labels-to-wipe EPHEMERAL -n <node ip> --reboot=true

That's it! After you run the last command, the partition will be wiped and the node will reboot. During the next boot the system will encrypt the partition.

State Partition

Calling wipe against the STATE partition will make the node lose the config, so the previous flow is not going to work.

The flow should be to first wipe the STATE partition:

talosctl reset  --system-labels-to-wipe STATE -n <node ip> --reboot=true

Node will enter into maintenance mode, then run apply-config with --insecure flag:

talosctl apply-config --insecure -n <node ip> -f config.yaml

After installation is complete the node should encrypt the STATE partition.