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 master key and immediately splits this master key into a series of key shares following Shamir's Secret Sharing Algorithm. Vault never stores the master key, therefore, the only way to retrieve the master key is to have a quorum of unseal keys re-generate it.
The master key is used to decrypt the underlying encryption key. Vault uses the encryption key to encrypt data at rest in a storage backend like the filesystem or Consul.
Typically 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 master key and key shares. Here are a few examples:
- Someone joins or leaves the organization
- Security wants to change the number of shares or threshold of shares
- Compliance mandates the master key be rotated at a regular interval
In addition to rekeying the master 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 master key and applying Shamir's algorithm is called "rekeying". The process for generating a new encryption key for Vault to encrypt data at rest is called "rotating".
Both rekeying the Vault and rotating Vault's underlying encryption key 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.
-> NOTE: 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 add the flag -target=recovery to the rekey command to process recovery keys instead of unseal keys.
Key Value--- -----Nonce 3e6e2a84-eae4-9841-b68d-29edceb39036Started trueRekey Progress 0/3New Shares 3New Threshold 2Verification Required false
Each key holder runs the following command and enters their unseal key.
$ vault operator rekey Rekey operation nonce: 3e6e2a84-eae4-9841-b68d-29edceb39036Key (will be hidden):
Key Value--- -----Nonce 3e6e2a84-eae4-9841-b68d-29edceb39036Started trueRekey Progress 1/3New Shares 3New Threshold 2Verification 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+TtihTulfdHvFzXtBYQk36dmBczuQKey 2: sCkM1i5BGGNDFk5GsqtVolWRPyd5mWn2eZG0gUySiCF7Key 3: e5DUvDIH0cPU8Q+hh1KNVkkMc9lliliPVe9u3Fzbzv38 Operation nonce: dc1aec3b-ae67-5780-b4b5-2a10ca05b17c Vault rekeyed with 3 keys and a key threshold of 2. Pleasesecurely distribute the above keys. When the vault is re-sealed,restarted, or stopped, you must provide at least 2 of these keysto unseal it again. Vault does not store the master 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.
»Rotating the encryption key
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.
NOTE: 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.
»Adjusting the automatic key rotation
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 trueinterval 0max_operations 3865470566
Configure a time interval for automatic key rotation.
$ vault write sys/rotate/config interval=2160hSuccess! Data written to: sys/rotate/config
Configure the maximum number of encryption operations per key.
$ vault write sys/rotate/config max_operations=123456789Success! Data written to: sys/rotate/config
»Manual key rotation
Trigger a key rotation.
$ vault operator rotate
Example output: The output displays the key version and installation time.
Success! Rotated key Key Term 2Install Time 23 Jul 21 21:41 UTCEncryption 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.