Implement a custom propagation token for security attribute propagation

This page explains how we might create our own propagation token implementation, which is set on the running thread and propagated downstream.

The default propagation token usually is sufficient for propagating attributes that are not user-specific. Consider writing our own implementation to accomplish one of the following tasks:

• Isolate the attributes within our own implementation.

• Serialize the information using custom serialization. You must deserialize the bytes at the target and add that information back on the thread by plugging in a custom login module into the inbound system login configurations. This task also might include encryption and decryption.

To implement a custom propagation token, complete the following steps:

 

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, we can place it in the APP_ROOT/classes directory. Alternatively, we can place the class in any private directory. However, make sure that the WAS class loader can locate the class and that it is granted the appropriate permissions. We can add the JAR file or directory that contains this class into the server.policy file so that it has the required permissions for the server code.

   Tip: All of the token types 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 we 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 the 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 WAS logins.

   This task is typically accomplished by adding a custom login module to the various application and system login configurations. We also can add the implementation from an application. However, to deserialize the information, we need to 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 the specific custom propagation token TokenHolder instance, convert the byte array back into the custom PropagationToken object, and set it back on the thread. The code sample shows both instances.

   You can add attributes any time the custom propagation token is added to the thread. If we add attributes between requests and the getUniqueId method changes, the 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 the custom login module to WAS system login configurations that already contain the com.ibm.ws.security.server.lm.wsMapDefaultInboundLoginModule login module for receiving serialized versions of the custom propagation token We can also add this login module to any of the application logins where we might want to generate the custom propagation token on the thread during the login. Alternatively, we can generate the custom PropagationToken implementation from within the application. However, to deserialize it, we need to add the implementation to the system login modules.

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

 

Results

After completing these steps, we have implemented a custom PropagationToken.

Example: com.ibm.wsspi.security.token.PropagationToken implementation
Example: Custom propagation token login module

 

Related concepts

Security attribute propagation

 

Related tasks

Propagating security attributes among appservers
Develop custom login modules for a system login configuration for JAAS
Implementing tokens for security attribute propagation