Authentication in X-Pack security is handled by one or more authentication services called realms. A realm is used to resolve and authenticate users based on authentication tokens. X-Pack security provides the following built-in realms:
- An internal realm where users are stored in a dedicated Elasticsearch index. This realm supports an authentication token in the form of username and password, and is available by default when no realms are explicitly configured. The users are managed via the user management APIs. See Native user authentication.
- A realm that uses an external LDAP server to authenticate the users. This realm supports an authentication token in the form of username and password, and requires explicit configuration in order to be used. See LDAP user authentication.
- A realm that uses an external Active Directory Server to authenticate the users. With this realm, users are authenticated by usernames and passwords. See Active Directory user authentication.
- A realm that authenticates users using Public Key Infrastructure (PKI). This realm works in conjunction with SSL/TLS and identifies the users through the Distinguished Name (DN) of the client’s X.509 certificates. See PKI user authentication.
- An internal realm where users are defined in files stored on each node in the Elasticsearch cluster. This realm supports an authentication token in the form of username and password and is always available. See File-based user authentication.
- A realm that facilitates authentication using the SAML 2.0 Web SSO protocol. This realm is designed to support authentication through Kibana and is not intended for use in the REST API. See SAML authentication.
- A realm that authenticates a user using Kerberos authentication. Users are authenticated on the basis of Kerberos tickets. See Kerberos authentication.
X-Pack security also supports custom realms. If you need to integrate with another authentication system, you can build a custom realm plugin. For more information, see Integrating with Other Authentication Systems.
Realm types can roughly be classified in two categories:
Realms that are internal to Elasticsearch and don’t require any
communication with external parties. They are fully managed by
X-Pack security. There can only be a maximum of one configured realm
per internal realm type. X-Pack security provides two internal realm
Realms that require interaction with parties/components external to
Elasticsearch, typically, with enterprise grade identity management
systems. Unlike internal realms, there can be as many external realms
as one would like - each with its own unique name and configuration.
X-Pack security provides the following external realm types: