Configuring the Security backend

One of the first steps to using the Security plugin is to decide on an authentication backend, which handles steps 2-3 of the authentication flow. The plugin has an internal user database, but many people prefer to use an existing authentication backend, such as an LDAP server, or some combination of the two.

The main configuration file for authentication and authorization backends is config/opensearch-security/config.yml. It defines how the Security plugin retrieves the user credentials, how it verifies these credentials, and how to fetch additional roles from backend systems (optional).

config.yml has three main parts:

opensearch_security:
  dynamic:
    http:
      ...
    authc:
      ...
    authz:
      ...

For a more complete example, see the sample file on GitHub.

HTTP

The http section has the following format:

anonymous_auth_enabled: <true|false>
xff: # optional section
  enabled: <true|false>
  internalProxies: <string> # Regex pattern
  remoteIpHeader: <string> # Name of the header in which to look. Typically: x-forwarded-for
  proxiesHeader: <string>
  trustedProxies: <string> # Regex pattern

If you disable anonymous authentication, the Security plugin won’t initialize if you have not provided at least one authc.

Authentication

The authc section has the following format:

<name>:
  http_enabled: <true|false>
  transport_enabled: <true|false>
  order: <integer>
  http_authenticator:
    ...
  authentication_backend:
    ...

An entry in the authc section is called an authentication domain. It specifies where to get the user credentials and against which backend they should be authenticated.

You can use more than one authentication domain. Each authentication domain has a name (for example, basic_auth_internal), enabled flags, and an order. The order makes it possible to chain authentication domains together. The Security plugin uses them in the order that you provide. If the user successfully authenticates with one domain, the Security plugin skips the remaining domains.

http_authenticator specifies which authentication method that you want to use on the HTTP layer.

This is the syntax for defining an authenticator on the HTTP layer:

http_authenticator:
  type: <type>
  challenge: <true|false>
  config:
    ...

These are the allowed values for type:

• basic: HTTP basic authentication. No additional configuration is needed.
• jwt: JSON Web Token (JWT) authentication. Additional configuration is needed. See Configuring JWTs for more information.
• clientcert: Authentication through a client TLS certificate. This certificate must be trusted by one of the root CAs in the truststore of your nodes.

After setting an HTTP authenticator, you must specify against which backend system you want to authenticate the user:

authentication_backend:
  type: <type>
  config:
    ...

These are the possible values for type:

• noop: No further authentication against any backend system is performed. Use noop if the HTTP authenticator has already authenticated the user completely, as in the case of JWT or client certificate authentication.
• internal: Use the users and roles defined in internal_users.yml for authentication.
• ldap: Authenticate users against an LDAP server. This setting requires additional, LDAP-specific configuration settings.

Authorization

After the user has been authenticated, the Security plugin can optionally collect additional roles from backend systems. The authorization configuration has the following format:

authz:
  <name>:
    http_enabled: <true|false>
    transport_enabled: <true|false>
    authorization_backend:
      type: <type>
      config:
        ...

You can define multiple entries in this section the same way as you can for authentication entries. In this case, execution order is not relevant, so there is no order field.

These are the possible values for type:

• noop: Skip this step altogether.
• ldap: Fetch additional roles from an LDAP server. This setting requires additional, LDAP-specific configuration settings.

HTTP basic authentication

To set up HTTP basic authentication, you must enable it in the http_authenticator section of the configuration:

http_authenticator:
  type: basic
  challenge: true

In most cases, you set the challenge flag to true. The flag defines the behavior of the Security plugin if the Authorization field in the HTTP header is not set.

If challenge is set to true, the Security plugin sends a response with status UNAUTHORIZED (401) back to the client. If the client is accessing the cluster with a browser, this triggers the authentication dialog box, and the user is prompted to enter a user name and password.

If challenge is set to false and no Authorization header field is set, the Security plugin does not send a WWW-Authenticate response back to the client, and authentication fails. You might want to use this setting if you have another challenge http_authenticator in your configured authentication domains. One such scenario is when you plan to use basic authentication and OpenID Connect together.

Backend configuration examples

The default config/opensearch-security/config.yml file included in your OpenSearch distribution contains many configuration examples. Use these examples as a starting point and customize them to your needs.

Next steps

To learn about configuring supported authentication backends, see the relevant topic for each type in the Authentication backends documentation.