Configuring TAI for Liberty

You can configure Liberty to integrate with a third-party security service by using Trust Association Interceptors (TAI). The TAI can be called before or after single sign-on (SSO).

Before you begin

Make sure that you have already installed a third-party security server as a reverse proxy server. The third-party security server can act as a front-end authentication server when the Liberty server applies its own authorization policy onto the resulting credentials, which are passed by the proxy server. You must also have a JAR file that contains the custom TAI class, which implements the interface.
Note: There is no support for monitoring changes of this JAR file.

About this task

A TAI is used to validate HTTP requests between a third-party security server and a Liberty server. The TAI inspects the HTTP requests from the third-party security server to see whether they contain any security attributes. If the process of validating a request by the TAI is successful, the Liberty server authorizes the request by checking whether the client user has the required permission to access the resources.

For more information of custom TAI and SSO configuration with LTPA, see Developing a custom TAI for Liberty and Customizing SSO configuration using LTPA cookies in Liberty.

Avoid trouble: To avoid potential issues, users must not configure the TrustAssociationInterceptor component to call the InitialDirContext class with the Java property java.naming.ldap.factory.socket set to a socket factory other than Liberty's own ( Setting this property to other factories can cause a NoClassDefFoundException.


  1. Enable the appSecurity-3.0 Liberty feature in the server.xml file.
  2. Deploy your applications to the Liberty server and enable all Liberty features, such as, jsp-2.2 and jdbc-4.0.
  3. Place the TAI implementation library simpleTAI.jar in your server directory.
  4. Update the server.xml file with the TAI configuration options and location of the TAI implementation library.
    In the following server.xml file, the custom TAI is enabled, but does not do any authentication for unprotected URIs and does not allow to fallback to application authentication method if the TAI authentication fails. As shown in the example, the following configuration elements are available for TAI support:
    • trustAssociation
    • interceptors
    • properties
    <trustAssociation id="myTrustAssociation" invokeForUnprotectedURI="false" 
        <interceptors id="simpleTAI" enabled="true"  
                      invokeBeforeSSO="true" invokeAfterSSO="false" libraryRef="simpleTAI"> 
            <properties prop1="value1" prop2="value2"/>
    <library id="simpleTAI"> 
        <fileset dir="${server.config.dir}" includes="simpleTAI.jar"/> 
    Note: The property name cannot start with a period (.), config., or service. Also, the property name id or ID is not allowed.
    Note: By default, the invokeBeforeSSO property is set to true. By using this setting TAI is invoked even when the SSO token is present and valid. However, if the expected behavior is to invoke TAI only when the SSO token is invalid or not present, then this property can be disabled by setting it to false, and enabling the invokeAfterSSO property. By using this setting TAI is invoked only when the SSO token is not present or is invalid. In some cases, this setup might improve the performance of your system.

    For more information about the <trustAssociation>, <interceptors> and <properties> elements, see JMX REST Connector 2.0.