diff --git a/website/content/docs/internals/rotation.mdx b/website/content/docs/internals/rotation.mdx index 79e653b9fe07..1c6a022e795b 100644 --- a/website/content/docs/internals/rotation.mdx +++ b/website/content/docs/internals/rotation.mdx @@ -6,78 +6,95 @@ description: Learn about the details of key rotation within Vault. # Key rotation -Vault has multiple encryption keys that are used for various purposes. These keys support -rotation so that they can be periodically changed or in response to a potential leak or -compromise. It is useful to first understand the -[high-level architecture](/vault/docs/internals/architecture) before learning about key rotation. - -As a review, Vault starts in a _sealed_ state. Vault is unsealed by providing the unseal keys. -By default, Vault uses a technique known as [Shamir's secret sharing algorithm](https://en.wikipedia.org/wiki/Shamir's_Secret_Sharing) -to split the root key into 5 shares, any 3 of which are required to reconstruct the master -key. The root key is used to protect the encryption key, which is ultimately used to protect -data written to the storage backend. +Vault stores different encryption keys for different purposes. Vault uses key +rotation to periodically change the keys according to a configured limit or in +response to a potential leak or compromised service. + +## Relevant key definitions + +There are four keys involved in key rotation: + +- **internal encryption key** - Encrypts and protects data written to the + storage backend. +- **root key** - "Master" key that seals Vault and protects the internal + encryption key. +- **unseal key** - A portion (share) of the root key used to reconstruct the + root key. By default, Vault uses the + [Shamir's secret sharing algorithm](https://en.wikipedia.org/wiki/Shamir's_Secret_Sharing) + to split the root key into 5 shares. +- **upgrade key** - A short-lived copy of the internal encryption key created + during key rotation in high-availability deployments. Vault encrypts upgrade + keys using the previous internal encryption key. + +## How key rotation works + +Vault supports online **rekey** and **rotate** operations to update the root +key, unseal keys, and backend encryption key even for high-availability +deployments. In replicated deployments, the active node performs the operations +and standby nodes use an upgrade key to update their keys without requiring a +manual unseal operation. + +1. Rekeying begins with a configured split and threshold for unseal keys: + 1. Vault receives the configured threshold of unseal keys. + 1. Vault generates and splits the new root key. + 1. Vault re-encrypts the internal encryption key with the new root key. + 1. Vault returns the new unseal keys. +1. Rotation begins: + 1. Vault generates a new internal encryption key. + 1. Vault adds the new encryption key to an internal keyring. + 1. Vault creates a temporary **upgrade key** (if needed). ![Key Rotate](/img/vault-key-rotate.png) -To support key rotation, we need to support changing the unseal keys, root key, and the -backend encryption key. We split this into two separate operations, `rekey` and `rotate`. - -The `rekey` operation is used to generate a new root key. When this is being done, -it is possible to change the parameters of the key splitting, so that the number of shares -and the threshold required to unseal can be changed. To perform a rekey a threshold of the -current unseal keys must be provided. This is to prevent a single malicious operator from -performing a rekey and invalidating the existing root key. - -Performing a rekey is fairly straightforward. The rekey operation must be initialized with -the new parameters for the split and threshold. Once initialized, the current unseal keys -must be provided until the threshold is met. Once met, Vault will generate the new master -key, perform the splitting, and re-encrypt the encryption key with the new root key. -The new unseal keys are then provided to the operator, and the old unseal keys are no -longer usable. - -The `rotate` operation is used to change the encryption key used to protect data written -to the storage backend. This key is never provided or visible to operators, who only -have unseal keys. This simplifies the rotation, as it does not require the current key -holders unlike the `rekey` operation. When `rotate` is triggered, a new encryption key -is generated and added to a keyring. All new values written to the storage backend are -encrypted with the new key. Old values written with previous encryption keys can still -be decrypted since older keys are saved in the keyring. This allows key rotation to be -done online, without an expensive re-encryption process. - -Both the `rekey` and `rotate` operations can be done online and in a highly available -configuration. Only the active Vault instance can perform either of the operations -but standby instances can still assume an active role after either operation. This is -done by providing an online upgrade path for standby instances. If the current encryption -key is `N` and a rotation installs `N+1`, Vault creates a special "upgrade" key, which -provides the `N+1` encryption key protected by the `N` key. This upgrade key is only available -for a few minutes enabling standby instances to do a periodic check for upgrades. -This allows standby instances to update their keys and stay in-sync with the active Vault -without requiring operators to perform another unseal. - -The `rotate/config` endpoint is used to configure the number of operations or time interval -between automatic rotations of the backend encryption key. +Once the rotation completes, Vault can encrypt new writes to the storage backend +using the new key, but still decrypt entries written under the previous key. + + + + ConfigureKeyRotation - [`POST:/sys/rotate/config`](/vault/api-docs/system/rotate-config) + + + ## NIST rotation guidance -Periodic rotation of the encryption keys is recommended, even in the absence of -compromise. Due to the nature of the AES-256-GCM encryption used, keys should be -rotated before approximately 232 encryptions have been performed, following -the guidelines of NIST publication 800-38D. +The National Institute of Standards and Technology (NIST) recommends +periodically rotating encryption keys, even without a leak or compromise event. + +Due to the nature of AES-256-GCM encryption, +[NIST publication 800-38D](https://csrc.nist.gov/pubs/sp/800/38/d/final) +recommends rotating keys **before** performing ~232 encryptions. By +default, Vault monitors the `vault.barrier.estimated_encryptions` metric and +automatically rotates the backend encryption key before reaching 232 +encryption operations. + +You can approximate the `vault.barrier.estimated_encryptions` metric with the +following sum: + + + +```text +ESTIMATED_OPS = PUT_EVENTS + CREATE_EVENTS + MERKLE_FLUSH_EVENTS + WAL_INDEX +``` + + + +where: -As of Vault 1.7, Vault will automatically rotate the backend encryption key -prior to reaching 232 encryption operations by default. +- **`PUT_EVENTS`** is the `vault.barrier.put` telemetry metric. +- **`CREATION_EVENTS`** is the `vault.token.creation` metric where `token_type` + is `batch`. +- **`MERKLE_FLUSH_EVENTS`** is the `merkle.flushDirty.num_pages` telemetry metric. +- **`WAL_INDEX`** is the current write-ahead-log index. -Operators can estimate the number of encryptions by summing the following: + -- The `vault.barrier.put` telemetry metric. -- The `vault.token.creation` metric where the `token_type` label is `batch`. -- The `merkle.flushDirty.num_pages` metric. -- The WAL index. + Vault periodically persists the number of encryptions to support rotation. The + save operation has a 1 second timeout to limit performance impact when Vault is + under heavy load. If you use seal wrap, persisting encryptions involves the seal + backend, which means that some seals, like HSMs, may routinely take longer than + 1 second to respond. You can override the save timeout by setting the + `VAULT_ENCRYPTION_COUNT_PERSIST_TIMEOUT` environment variable on your Vault + server to a larger value, such as "5s". -Vault periodically persists the number of encryptions to support rotation. -This save operation has a 1 second timeout to prevent impact to performance -if Vault is under heavy load. Because persisting encryptions involves the -seal backend (if seal wrap is enabled), some seals (such as HSMs) may take -regularly longer than 1 second to respond. If this is the case, operators -may override that timeout by setting the environment variable -`VAULT_ENCRYPTION_COUNT_PERSIST_TIMEOUT` to a larger value, such as "5s". \ No newline at end of file + diff --git a/website/content/docs/internals/telemetry/metrics/all.mdx b/website/content/docs/internals/telemetry/metrics/all.mdx index adf0bb046f51..269e13e2d527 100644 --- a/website/content/docs/internals/telemetry/metrics/all.mdx +++ b/website/content/docs/internals/telemetry/metrics/all.mdx @@ -130,6 +130,8 @@ alphabetic order by name. @include 'telemetry-metrics/vault/barrier/delete.mdx' +@include 'telemetry-metrics/vault/barrier/estimated_encryptions.mdx' + @include 'telemetry-metrics/vault/barrier/get.mdx' @include 'telemetry-metrics/vault/barrier/list.mdx' diff --git a/website/content/docs/internals/telemetry/metrics/core-system.mdx b/website/content/docs/internals/telemetry/metrics/core-system.mdx index 8256e64c8ded..a2c7b95bc148 100644 --- a/website/content/docs/internals/telemetry/metrics/core-system.mdx +++ b/website/content/docs/internals/telemetry/metrics/core-system.mdx @@ -58,6 +58,8 @@ Vault instance. @include 'telemetry-metrics/vault/barrier/delete.mdx' +@include 'telemetry-metrics/vault/barrier/estimated_encryptions.mdx' + @include 'telemetry-metrics/vault/barrier/get.mdx' @include 'telemetry-metrics/vault/barrier/list.mdx' diff --git a/website/content/docs/internals/telemetry/metrics/storage.mdx b/website/content/docs/internals/telemetry/metrics/storage.mdx index 84539eb712e0..f92c99e2dec9 100644 --- a/website/content/docs/internals/telemetry/metrics/storage.mdx +++ b/website/content/docs/internals/telemetry/metrics/storage.mdx @@ -15,6 +15,8 @@ configured storage backends. For integrated storage metrics, refer to the @include 'telemetry-metrics/vault/barrier/delete.mdx' +@include 'telemetry-metrics/vault/barrier/estimated_encryptions.mdx' + @include 'telemetry-metrics/vault/barrier/get.mdx' @include 'telemetry-metrics/vault/barrier/list.mdx' diff --git a/website/content/partials/telemetry-metrics/vault/barrier/estimated_encryptions.mdx b/website/content/partials/telemetry-metrics/vault/barrier/estimated_encryptions.mdx new file mode 100644 index 000000000000..c3dc555c7a5f --- /dev/null +++ b/website/content/partials/telemetry-metrics/vault/barrier/estimated_encryptions.mdx @@ -0,0 +1,6 @@ +### vault.barrier.estimated_encryptions ((#vault-barrier-estimated_encryptions)) + +Metric type | Value | Description +----------- | ------ | ----------- +counter | number | The estimated number of encryptions performed since the last key rotation +