Implementing a custom propagation token for security attribute propagation

This topic explains how you might create your own propagation token implementation, which is set on the running thread and propagated downstream.

1. Write a custom implementation of the PropagationToken interface.
   Many different methods are available for implementing the PropagationToken interface. However, make sure that the methods that are required by the PropagationToken interface and the token interface are fully implemented.

   After you implement this interface, you can place it in the app_server_root/classes directory. Alternatively, you can place the class in any private directory. However, make sure that the WebSphere Application Server class loader can locate the class and that it is granted the appropriate permissions. You can add the Java™ archive (JAR) file or directory that contains this class into the server.policy file so that it has the required permissions for the server code.

   After you implement this interface, you can place it in the profile_root/classes directory. For more information on classes, see Creating a classes subdirectory in your profile for custom classes.

   Tip: All of the token types that are defined by the propagation framework have similar interfaces. The token types are marker interfaces that implement the com.ibm.wsspi.security.token.Token interface. This interface defines most of the methods. If you plan to implement more than one token type, consider creating an abstract class that implements the com.ibm.wsspi.security.token.Token interface. All of your token implementations, including the propagation token, might extend the abstract class and then most of the work is complete.

   To see an implementation of the propagation token, see Example: com.ibm.wsspi.security.token.PropagationToken implementation.

2. Add and receive the custom propagation token during WebSphere Application Server logins.
   This task is typically accomplished by adding a custom login module to the various application and system login configurations. You also can add the implementation from an application. However, to deserialize the information, you must plug in a custom login module, which is discussed in Propagating a custom Java serializable object for security attribute propagation. The WSSecurityPropagationHelper class has APIs that are used to set a propagation token on the thread and to retrieve the token from the thread to make updates.

   The code sample in Example: Custom propagation token login module shows how to determine if the login is an initial login or a propagation login. The difference between these login types is whether the WSTokenHolderCallback callback contains propagation data. If the callback does not contain propagation data, initialize a new custom propagation token implementation and set it on the thread. If the callback contains propagation data, look for your specific custom propagation token TokenHolder instance, convert the byte array back into your custom PropagationToken object, and set it back on the thread. The code sample shows both instances.

   You can add attributes any time your custom propagation token is added to the thread. If you add attributes between requests and the getUniqueId method changes, the Common Secure Interoperability Version 2 (CSIv2) client session is invalidated so that it can send the new information downstream. Adding attributes between requests can affect performance. In many cases, you want the downstream requests to receive the new propagation token information.

   To add the custom propagation token to the thread, call the WSSecurityPropagationHelper.addPropagationToken method. This call requires the WebSphereRuntimePerMission "setPropagationToken" Java 2 Security permission.

3. Add your custom login module to WebSphere Application Server system login configurations that already contain the com.ibm.ws.security.server.lm.wsMapDefaultInboundLoginModule login module for receiving serialized versions of your custom propagation token
   You can also add this login module to any of the application logins where you might want to generate your custom propagation token on the thread during the login. Alternatively, you can generate the custom PropagationToken implementation from within your application. However, to deserialize it, you must add the implementation to the system login modules.

   For information on how to add your custom login module to the existing login configurations, see Developing custom login modules for a system login configuration for JAAS.