Integrating with other authentication systems

If you are using an authentication system that is not supported out-of-the-box by the Elasticsearch security features, you can create a custom realm to interact with it to authenticate users. You implement a custom realm as an SPI loaded security extension as part of an ordinary elasticsearch plugin.

Implementing a custom realm

Sample code that illustrates the structure and implementation of a custom realm is provided in https://github.com/elastic/elasticsearch/tree/current/x-pack/qa/security-example-spi-extension. You can use this code as a starting point for creating your own realm.

To create a custom realm, you need to:

1. Extend org.elasticsearch.xpack.security.authc.Realm to communicate with your authentication system to authenticate users.
2. Implement the org.elasticsearch.xpack.security.authc.Realm.Factory interface in a class that will be used to create the custom realm.
3. Extend org.elasticsearch.xpack.security.authc.DefaultAuthenticationFailureHandler to handle authentication failures when using your custom realm.

To package your custom realm as a plugin:

1. Implement an extension class for your realm that extends org.elasticsearch.xpack.core.security.SecurityExtension. There you need to override one or more of the following methods:

   @Override
   public Map<String, Factory> getRealms() {
       ...
   }

   The getRealms method is used to provide a map of type names to the Factory that will be used to create the realm.

   @Override
   public AuthenticationFailureHandler getAuthenticationFailureHandler() {
       ...
   }

   The getAuthenticationFailureHandler method is used to optionally provide a custom AuthenticationFailureHandler, which will control how the Elasticsearch security features respond in certain authentication failure events.

   @Override
   public List<String> getSettingsFilter() {
       ...
   }

   The Plugin#getSettingsFilter method returns a list of setting names that should be filtered from the settings APIs as they may contain sensitive credentials. Note this method is not part of the SecurityExtension interface, it’s available as part of the elasticsearch plugin main class.

2. Create a build configuration file for the plugin; Gradle is our recommendation.

3. 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
4. Bundle all in a single zip file.

Using a custom realm to authenticate users

To use a custom realm:

1. Install the realm 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:

   bin/elasticsearch-plugin install file:///<path>/my-realm-1.0.zip

2. Add a realm configuration of the appropriate realm type to elasticsearch.yml under the xpack.security.authc.realms namespace. You must define your realm within the namespace that matches the type defined by the extension. The options you can set depend on the settings exposed by the custom realm. If you are configuring multiple realms, you should also explicitly set the order attribute to control the order in which the realms are consulted during authentication. You should make sure each configured realm has a distinct order setting. In the event that two or more realms have the same order, they will be processed in realm name order.

   When you configure realms in elasticsearch.yml, only the realms you specify are used for authentication. If you also want to use the native or file realms, you must include them in the realm chain.

3. Restart Elasticsearch.