Key Management

Nomad servers maintain an encryption keyring used to encrypt Variables and sign task workload identities. The servers store key metadata in raft, but the encryption key material is stored in a separate file in the keystore subdirectory of the Nomad data directory. These files have the extension .nks.json. The key material in each file is wrapped in a unique key encryption key (KEK) that is not shared between servers. Nomad servers can use an external KMS or Vault transit encryption to wrap the key material using the keyring configuration block.

Under normal operations the keyring is entirely managed by Nomad, but this section provides administrators additional context around key replication and recovery.

Key Rotation

Only one key in the keyring is "active" at any given time, and all encryption and signing operations happen on the leader. Nomad automatically rotates the active encryption key every 30 days. When a key is rotated, the existing keys are marked as "inactive" but not deleted, so they can be used for decrypting previously encrypted variables and verifying workload identities for existing allocations.

If you believe key material has been compromised, you can execute nomad operator root keyring rotate -full. A new "active" key will be created and "inactive" keys will be marked "rekeying". Nomad will asynchronously decrypt and re-encrypt all variables with the new key. As each key's variables are encrypted with the new key, the old key will marked as "deprecated".

Key Replication

When a leader is elected, it creates the keyring if it does not already exist. When a key is added, the metadata will be replicated via raft. Each server runs a key replication process that watches for changes to the state store and will fetch the key material from the leader asynchronously, falling back to retrieving from other servers in the case where a key is written immediately before a leader election.

Restoring the Keyring from Backup

Key material is never stored in raft. This prevents an attacker with a backup of the state store from getting access to encrypted variables. It also allows the HashiCorp engineering and support organization to safely handle cluster snapshots you might provide without exposing any of your keys or variables.

However, this means that to restore a cluster from snapshot you need to also provide the keystore directory with the .nks.json key files on at least one server. The .nks.json key files are unique per server, but only one server's key files are needed to recover the cluster. Operators should include these files as part of your organization's backup and recovery strategy for the cluster.

If you are recovering a Raft snapshot onto a new cluster without running workloads, you can skip restoring the keyring and run nomad operator root keyring rotate once the servers have joined.