[role="xpack"]
[[custom-roles-authorization]]
=== Customizing roles and authorization

If you need to retrieve user roles from a system not supported out-of-the-box
or if the authorization system that is provided by the {es} {security-features}
does not meet your needs, a SPI loaded security extension can be implemented to
customize role retrieval and/or the authorization system. The SPI loaded
security extension is part of an ordinary elasticsearch plugin.

[[implementing-custom-roles-provider]]
==== Implementing a custom roles provider

To create a custom roles provider:

. Implement the interface `BiConsumer<Set<String>, ActionListener<Set<RoleDescriptor>>>`.
  That is to say, the implementation consists of one method that takes a set of strings,
  which are the role names to resolve, and an ActionListener, on which the set of resolved
  role descriptors are passed on as the response.
. The custom roles provider implementation must take special care to not block on any I/O
  operations. It is the responsibility of the implementation to ensure asynchronous behavior
  and non-blocking calls, which is made easier by the fact that the `ActionListener` is
  provided on which to send the response when the roles have been resolved and the response
  is ready.

To package your custom roles provider as a plugin:

. Implement an extension class for your roles provider that implements
  `org.elasticsearch.xpack.core.security.SecurityExtension`. There you need to
  override one or more of the following methods:
+
[source,java]
----------------------------------------------------
@Override
public List<BiConsumer<Set<String>, ActionListener<Set<RoleDescriptor>>>>
getRolesProviders(Settings settings, ResourceWatcherService resourceWatcherService) {
    ...
}
----------------------------------------------------
+
The `getRolesProviders` method is used to provide a list of custom roles providers that
will be used to resolve role names, if the role names could not be resolved by the reserved
roles or native roles stores. The list should be returned in the order that the custom role
providers should be invoked to resolve roles. For example, if `getRolesProviders` returns two
instances of roles providers, and both of them are able to resolve role `A`, then the resolved
role descriptor that will be used for role `A` will be the one resolved by the first roles
provider in the list.

[[implementing-authorization-engine]]
==== Implementing an authorization engine

To create an authorization engine, you need to:

. Implement the `org.elasticsearch.xpack.core.security.authz.AuthorizationEngine`
  interface in a class with the desired authorization behavior.
. Implement the `org.elasticsearch.xpack.core.security.authz.Authorization.AuthorizationInfo`
  interface in a class that contains the necessary information to authorize the request.

To package your authorization engine as a plugin:

. Implement an extension class for your authorization engine that extends
  `org.elasticsearch.xpack.core.security.SecurityExtension`. There you need to
  override the following method:
+
[source,java]
----------------------------------------------------
@Override
public AuthorizationEngine getAuthorizationEngine(Settings settings) {
    ...
}
----------------------------------------------------
+
The `getAuthorizationEngine` method is used to provide the authorization engine
implementation.

Sample code that illustrates the structure and implementation of a custom
authorization engine is provided in the
https://github.com/elastic/elasticsearch/tree/master/plugins/examples/security-authorization-engine[elasticsearch]
repository on GitHub. You can use this code as a starting point for creating your
own authorization engine.

[[packing-extension-plugin]]
==== Implement an elasticsearch plugin

In order to register the security extension for your custom roles provider or
authorization engine, you need to also implement an elasticsearch plugin that
contains the extension:

. Implement a plugin class that extends `org.elasticsearch.plugins.Plugin`
. Create a build configuration file for the plugin; Gradle is our recommendation.
. Create a `plugin-descriptor.properties` file as described in
  {plugins}/plugin-authors.html[Help for plugin authors].
. Create a `META-INF/services/org.elasticsearch.xpack.core.security.SecurityExtension` descriptor file for the
  extension that contains the fully qualified class name of your `org.elasticsearch.xpack.core.security.SecurityExtension` implementation
. Bundle all in a single zip file.

[[using-security-extension]]
==== Using the security extension

To use a security extension:

. Install the plugin with the extension on each node in the cluster. You run
  `bin/elasticsearch-plugin` with the `install` sub-command and specify the URL
  pointing to the zip file that contains the extension. For example:
+
[source,shell]
----------------------------------------
bin/elasticsearch-plugin install file:///<path>/my-extension-plugin-1.0.zip
----------------------------------------

. Add any configuration parameters for implementations in the extension to the
`elasticsearch.yml` file. The settings are not namespaced and you have access to any
settings when constructing the extensions, although it is recommended to have a
namespacing convention for extensions to keep your `elasticsearch.yml`
configuration easy to understand.
+
For example, if you have a custom roles provider that
resolves roles from reading a blob in an S3 bucket on AWS, then you would specify settings
in `elasticsearch.yml` such as:
+
[source,js]
----------------------------------------
custom_roles_provider.s3_roles_provider.bucket: roles
custom_roles_provider.s3_roles_provider.region: us-east-1
custom_roles_provider.s3_roles_provider.secret_key: xxx
custom_roles_provider.s3_roles_provider.access_key: xxx
----------------------------------------
// NOTCONSOLE
+
These settings are passed as arguments to the methods in the `SecurityExtension` interface.

. Restart Elasticsearch.
