This topic explains how you might create your own propagation
token implementation, which is set on the running thread and propagated
downstream.
About this task
The default propagation token usually is sufficient for propagating
attributes that are not user-specific. 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 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, you must complete
the following steps:
- 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 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.
- 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 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 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.
- 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 need to 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.