Implement a custom authentication token for security attribute propagation

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

With this implementation, we can specify an authentication token that can be used by a custom login module or application. Consider writing our own implementation to accomplish one of the following tasks:

• Isolate the attributes within our own implementation.

• Serialize the information by using custom serialization. We 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 using the getUniqueID (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:

1. Write a custom implementation of the AuthenticationToken interface. Many different methods are available for implementing the AuthenticationToken interface. However, make sure the methods required by the AuthenticationToken interface and the token interface are fully implemented. After you implement this interface, we can place it in the app_server_root/classes directory. Alternatively, we can place the class in any private directory. However, verify the WAS class loader can locate the class and that it is granted the appropriate permissions. We can add the JAR file or directory containing this class into the server.policy file so the class has the necessary permissions required by the server code.

   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 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 plug in a custom login module. After the object is instantiated in the login module, we can add the object to the Subject during the commit method.

   If we only want to add information to the Subject to get propagated, see Propagating a custom Java serializable object for security attribute propagation. To ensure that the information is propagated, do our own custom serialization, or specify the uniqueness for Subject caching purposes, consider writing our 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 the specific custom authentication token TokenHolder instance, convert the byte array back into the custom AuthenticationToken object, and set it back into the Subject. The code sample shows both instances.

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

3. Add the 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 the custom authorization token.

   Because this login module relies on information in the shared state 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 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 authentication token.

Subtopics

• Example: A com.ibm.wsspi.security.token.AuthenticationToken implementation
  The following example illustrates an authentication token implementation. The following sample code does not extend an abstract class, but rather implements the com.ibm.wsspi.security.token.AuthenticationToken interface directly. We can implement the interface directly, but it might cause you to write duplicate code. However, you might choose to implement the interface directly if considerable differences exist between how you handle the various token implementations.

• Example: A custom authentication token login module
  This examples shows how to determine if the login is an initial login or a propagation login.

Related concepts

Security attribute propagation

Related tasks

Implement tokens for security attribute propagation

Propagating security attributes among application servers

Develop custom login modules for a system login configuration for JAAS

Propagating a custom Java serializable object for security attribute propagation