# Web UI Pre-Authentication

You can configure your Horizon instance to run behind a proxy that provides authentication. Authenticated users can then be directed to the Horizon web UI using a header. You can configure pre-authentication settings in `${OPENNMS_HOME}/jetty-webapps/opennms/WEB-INF/spring-security.d/header-preauth.xml`. This file is automatically included in the Spring security context, but is not enabled by default.  Do not configure Horizon to use pre-authentication unless you are certain that the web UI is accessible only to the proxy, and not to end users. If end users have access to the web UI, malicious attackers can craft queries that include the pre-authentication header, allowing them full control of the web UI and any REST APIs. ## Enable pre-authentication Set the `enabled` property in `header-preauth.xml`: ``<beans:property name="enabled" value="true" />`` ## Configure pre-authentication You can configure the following properties to change the pre-authentication plugin’s behavior: Property Description Default Value enabled Indicates whether the pre-authentication plugin is active. false failOnError If `true`, block users from logging in if their header is not set or the user does not exist. If `false`, fall through to other mechanisms (basic authentication, form login, and so on). false userHeader The HTTP header that specifies which user to authenticate. X-Remote-User credentialsHeader A comma-separated list of credentials to associate with the principal. If specified, the header must be set for authentication to be successful. Blank authoritiesHeader HTTP header. When set, this contains a comma-separated list of roles for the authenticated user. Blank ## Enable pre-authorization Modify `${OPENNMS-HOME}/jetty-webapps/opennms/WEB-INF/applicationContext-spring-security.xml`, and set the following:

``````<beans:bean id="preauthAuthProvider" class="org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationProvider">
<beans:property name="preAuthenticatedUserDetailsService">
<beans:bean id="preAuthUserDetailsService" class="org.springframework.security.web.authentication.preauth.PreAuthenticatedGrantedAuthoritiesUserDetailsService"/>
</beans:property>
</beans:bean>``````

After the pre-authentication plugin is enabled and set up, use the following command to test its configuration:

``curl -H "X-Remote-User: myuser" -H "X-Remote-Role: ROLE_USER,ROLE_REST" http://localhost:8980/opennms/rest/whoami``