Plugin system

Vault supports 3 types of plugins; auth methods, secret engines, and database plugins. This concept allows both built-in and external plugins to be treated like building blocks. Any plugin can exist at multiple different mount paths. Different versions of a plugin may be at each location, with each version differing from Vault's version.

A plugin is uniquely identified by its type (one of secret, auth, or database), name (e.g. aws), and version (e.g v1.0.0). An empty version implies either the built-in plugin or the single unversioned plugin that can be registered.

See Plugin Upgrade Procedure for details on how to upgrade a built-in plugin in-place.

Built-In plugins

Built-in plugins are shipped with Vault, often for commonly used integrations, and can be used without any prerequisite steps.

External plugins

External plugins are not shipped with Vault and require additional operator intervention to run.

To run an external plugin, a binary or container image of the plugin is required. Plugin binaries can be obtained from releases.hashicorp.com or they can be built from source. Containerized plugins are not yet available from a registry and must currently be built.

Vault's external plugins are completely separate, standalone applications that Vault executes and communicates with over RPC. Each time a Vault secret engine, auth method, or database plugin is mounted, a new process or container is spawned. However, plugins can be made to implement plugin multiplexing to improve performance. Plugin multiplexing allows plugin instances to be reused across all mounts of a given type.

Plugin versioning

Vault supports managing, running and upgrading plugins using semantic version information.

The plugin catalog optionally supports specifying a semantic version when registering an external plugin. Multiple versions of a plugin can be registered in the catalog simultaneously, and a version can be selected when mounting a plugin or tuning an existing mount in-place.

Alternatively, users can select pinned versions to enforce uniform cluster-wide version selection. When a pinned version is in effect, versions cannot be specified in mount config, and existing mounts that specify a version will ignore the locally configured version. See the pinned versions API for more details.

If no version is specified when creating a new mount, the following precedence is used for any available plugins whose type and name match:

1. The pinned version of the plugin, if any exists.
2. The plugin registered with no version.
3. The plugin with the most recent semantic version among any registered versions.
4. The plugin built into Vault.

Built-In versions

Vault will report a version for built-in plugins to indicate what version of the plugin code got built into Vault as a dependency. For example:

$ vault plugin list secret
Name                Version
----                -------
ad                  v0.14.0+builtin
alicloud            v0.13.0+builtin
aws                 v1.12.0+builtin.vault
# ...

Here, Vault has a dependency on v0.14.0 of the hashicorp/vault-plugin-secrets-ad repo, and the vault metadata identifier for aws indicates that plugin's code was within the Vault repo. For plugins within the Vault repo, Vault's own major, minor, and patch versions are used to form the plugin version.

The builtin metadata identifier is reserved and cannot be used when registering external plugins.