Implementing a custom authentication token for security attribute propagation

This topic explains how you might create your own authentication token implementation, which is set in the login Subject and propagated downstream.

About this task

With this implementation, you can specify an authentication token that can be used by a custom login module or application. Consider writing your own implementation if you want to accomplish one of the following tasks:
  • Isolate your attributes within your own implementation.
  • Serialize the information by using custom serialization. You must deserialize the bytes at the target and add that information back on the thread. This task also might include encryption and decryption.
  • Affect the overall uniqueness of the Subject by using the getUniqueID application programming interface (API).
Important: Custom authentication token implementations are not used by the security runtime in WebSphere® Application Server to enforce authentication. WebSphere Application Security runtime uses this token in the following situations only:
  • Call the getBytes method for serialization
  • Call the getForwardable method to determine whether to serialize the authentication token.
  • Call the getUniqueId method for uniqueness
  • Call the getName and the getVersion methods for adding serialized bytes to the token holder that is sent downstream
All of the other uses are custom implementations.

To implement a custom authentication token, you must complete the following steps:

Procedure

  1. Write a custom implementation of the AuthenticationToken interface.
    Many different methods are available for implementing the AuthenticationToken interface. However, make sure the methods that are required by the AuthenticationToken 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 the class has the necessary permissions that are required by the server code.
    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 authentication token, might extend the abstract class and then most of the work is complete.

    To see an implementation of the AuthenticationToken interface, see Example: A com.ibm.wsspi.security.token.AuthenticationToken implementation.

  2. Add and receive the custom authentication 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. However, to deserialize the information you must plug in a custom login module. After the object is instantiated in the login module, you can add the object to the Subject during the commit method.

    If you only want to add information to the Subject to get propagated, see Propagating a custom Java serializable object for security attribute propagation. If you want to ensure that the information is propagated, do your own custom serialization, or specify the uniqueness for Subject caching purposes, consider writing your own authentication token implementation.

    The code sample in Example: A custom authentication 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 authentication token implementation and set it into the Subject. If the callback contains propagation data, look for your specific custom authentication token TokenHolder instance, convert the byte array back into your custom AuthenticationToken object, and set it back into the Subject. The code sample shows both instances.

    You can make your authentication token read-only in the commit phase of the login module. If you do not make the token read-only, attributes can be added within your applications.

  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 authorization token.

    Because this login module relies on information in the shared state that is added by the com.ibm.ws.security.server.lm.wsMapDefaultInboundLoginModule login module, add this login module after the com.ibm.ws.security.server.lm.wsMapDefaultInboundLoginModule login module. 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.

Results

After completing these steps, you have implemented a custom authentication token.