Advanced Topic This tutorial presents an advanced topic that is not required for a basic understanding of Vault. Knowledge of this topic is not required for daily Vault use.
In order to prevent one person from having complete access to the system, Vault employs Shamir's Secret Sharing Algorithm. Under this process, a secret is divided into a subset of parts such that a subset of those parts are needed to reconstruct the original secret. Vault makes heavy use of this algorithm as part of the unsealing process.
When a Vault server is first initialized, Vault generates a root key (previously known as master key) and splits this root key into a series of key shares following Shamir's Secret Sharing Algorithm. The root key is used to decrypt the underlying encryption key. Vault uses the encryption key to encrypt data at rest in a storage backend such as Integrated Storage.
Each of these key shares is distributed to trusted parties in the organization. These parties must come together to "unseal" the Vault by entering their key share.
In some cases, you may want to re-generate the root key and its key shares. Here are a few examples:
- Someone joins or leaves the organization
- Security wants to change the number of shares or threshold
- Compliance mandates the keys be rotated at a regular interval
In addition to rekeying the root key, there may be an independent desire to rotate the underlying encryption key Vault uses to encrypt data at rest.
In Vault, rekeying and rotating are two separate operations. The process for generating a new root key and applying Shamir's algorithm is called "rekeying". The process for generating a new encryption key for Vault is called key "rotation".
Both the rekeying and rotating operations are fully online operations. Vault will continue to service requests uninterrupted during either of these processes.
This tutorial includes a free interactive command-line lab that lets you follow along on actual cloud infrastructure.
Rekeying the Vault requires a threshold number of unseal keys. Before continuing, you should ensure enough unseal key holders are available to assist with the rekeying to match the threshold configured when the keys were issued.
Initialize the rekeying operation. The flags represent the newly desired number of keys and threshold.
$ vault operator rekey -init -key-shares=3 -key-threshold=2
This will generate a nonce value and start the rekeying process. All other unseal keys must also provide this nonce value. This nonce value is not a secret, so it is safe to distribute over insecure channels like chat, email, or carrier pigeon.
The examples in this tutorial are for Vault using the default Shamir's Secret Sharing based seal. If your Vault uses an HSM or Cloud KMS based auto unseal, then you need to run the command with -target=recovery flag to the rekey command to process recovery keys instead of unseal keys:
vault operator rekey -init -key-shares=3 -key-threshold=2 -target=recovery
Key Value --- ----- Nonce 3e6e2a84-eae4-9841-b68d-29edceb39036 Started true Rekey Progress 0/3 New Shares 3 New Threshold 2 Verification Required false
Each key holder runs the following command and enters their unseal key.
$ vault operator rekey Rekey operation nonce: 3e6e2a84-eae4-9841-b68d-29edceb39036 Key (will be hidden):
Key Value --- ----- Nonce 3e6e2a84-eae4-9841-b68d-29edceb39036 Started true Rekey Progress 1/3 New Shares 3 New Threshold 2 Verification Required false
Repeat the step to complete the rekey operation. When the final unseal key holder enters their key, Vault will output the new unseal keys.
Key 1: EDj4NZK6z5Y9rpr+TtihTulfdHvFzXtBYQk36dmBczuQ Key 2: sCkM1i5BGGNDFk5GsqtVolWRPyd5mWn2eZG0gUySiCF7 Key 3: e5DUvDIH0cPU8Q+hh1KNVkkMc9lliliPVe9u3Fzbzv38 Operation nonce: dc1aec3b-ae67-5780-b4b5-2a10ca05b17c Vault rekeyed with 3 keys and a key threshold of 2. Please securely distribute the above keys. When the vault is re-sealed, restarted, or stopped, you must provide at least 2 of these keys to unseal it again. Vault does not store the root key. Without at least 2 keys, your vault will remain permanently sealed.
Like the initialization process, Vault supports PGP encrypting the resulting unseal keys and creating backup encryption keys for disaster recovery.
You can also verify that the newly generated keys are usable before the root key is actually rotated by specifying a
-verifyflag. You can learn more about key verification with this flag in the rekey API documentation.
Unlike rekeying the Vault, rotating Vault's encryption key does not require a quorum of unseal keys. Anyone with the proper permissions in Vault can perform the encryption key rotation.
As of Vault 1.7, Vault will automatically rotate the backend encryption key prior to reaching 232 encryption operations, in adherence with NIST SP800-32D guidelines.
View the current automatic rotation policy.
$ vault read sys/rotate/config
This returns the current status and configuration of automatic encryption key rotation.
Key Value --- ----- enabled true interval 0 max_operations 3865470566
Configure a time interval for automatic key rotation.
$ vault write sys/rotate/config interval=2160h Success! Data written to: sys/rotate/config
Configure the maximum number of encryption operations per key.
$ vault write sys/rotate/config max_operations=123456789 Success! Data written to: sys/rotate/config
Trigger a key rotation.
$ vault operator rotate
Example output: The output displays the key version and installation time.
Success! Rotated key
Key Term 2
Install Time 23 Jul 21 21:41 UTC
Encryption Count 1
This adds a new key to the keyring. All new values written to the storage backend will be encrypted with this new key.