Propagating a custom Java serializable object for security attribute propagation


This document describes how to add an object into the Subject from a login module and describes other infrastructure considerations to make sure that the Java object gets propagated.

Prior to completing this task, verify that security propagation is enabled in the admin console.

With security attribute propagation enabled, we can propagate data either horizontally with SSO enabled or downstream using CSIv2. When a login occurs, either through an application login configuration or a system login configuration, a custom login module can be plugged in to add Java serialized objects into the Subject during login. This document describes how to add an object into the Subject from a login module and describes other infrastructure considerations to make sure that the Java object gets propagated.

 

  1. Add the custom Java object into the Subject from a custom login module. A two-phase process exists for each Java Authentication and Authorization Service (JAAS) login module. WAS completes the following processes for each login module present in the configuration:

    login method

    In this step, the login configuration callbacks are analyzed, if necessary, and the new objects or credentials are created.

    commit method

    In this step, the objects or credentials that are created during login are added into the Subject.
    After a custom Java object is added into the Subject, WAS serializes the object on the sending server, deserializes the object on the receiving server, and adds the object back into the Subject downstream. However, some requirements exist for this process to occur successfully.

    See on the JAAS model, see the JAAS information provided in the Security: Links article.

    Whenever you plug a custom login module into the login infrastructure of WAS, make sure that the code is trusted. When you put the classes together in a Java archive (JAR) file and add the file to the APP_ROOT/lib/ext/ directory, the login module has Java 2 Security AllPermissions permissions . IBM recommends that you add your login module and other infrastructure classes into any private directory. However, modify the $WP_PROFILE/properties/server.policy file to make sure that the private directory, JAR file, or both have the permissions required to run the APIs that are called from the login module. Because the login module might be run after the application code on the call stack, we might add doPrivileged code so that you do not need to add additional properties to the applications.

    The following code sample shows how to add doPrivileged code. For information on what to do during initialization, login and commit, see Develop custom login modules for a system login configuration for JAAS.

    public customLoginModule() 
    {
      public void initialize(Subject subject, CallbackHandler callbackHandler, 
         Map sharedState, Map options) 
      {
    
      }
    
      public boolean login() throws LoginException 
      {
         
    // Construct callback for the WSTokenHolderCallback so that you 
         
    // can determine if
         
    // the custom object has propagated
          Callback callbacks[] = new Callback[1];
          callbacks[0] = new WSTokenHolderCallback("Authz Token List: ");
        
          try
          {
                _callbackHandler.handle(callbacks);
          } 
          catch (Exception e)
          {
          throw new LoginException (e.getLocalizedMessage());
          }
    
          
    // Checks to see if any information is propagated into this login
          List authzTokenList = ((WSTokenHolderCallback) callbacks[1]).
                getTokenHolderList();
    
          if (authzTokenList != null)
          {
               for (int i = 0; i< authzTokenList.size(); i++)
                 {
                    TokenHolder tokenHolder = (TokenHolder)authzTokenList.get(i);
    
                      
    //  Look for the custom object. Make sure you use  
                      
    //  "startsWith"because there is some data appended 
                      
    //  to the end of the name indicating in which Subject  
                      
    //  Set it belongs. Example from getName(): 
                      
    //  "com.acme.CustomObject (1)". The class name is 
                      
    //  generated at the sending side by calling the 
                      
    //  object.getClass().getName() method. If this object 
                      
    //  is deserialized by WAS, 
                      
    //  then return it and you do not need to add it here.
                      
    //  Otherwise, we can add it below.
                      
    //  
    

    If the class appears in this list and does // not use custom serialization (for example, an // implementation of the Token interface described in // the Propagation Token Framework), then WebSphere // Application Server automatically deserializes the // Java object for you. We might just return here if // it is found in the list. if (tokenHolder.getName().startsWith("com.acme.CustomObject")) return true; } } // If we get to this point, then the custom object has not propagated myCustomObject = new com.acme.CustomObject(); myCustomObject.put("mykey", "mydata"); } public boolean commit() throws LoginException { try { // Assigns a reference to a final variable so it can be used in // the doPrivileged block final com.acme.CustomObject myCustomObjectFinal = myCustomObject; // Prevents the applications from needing a JAAS getPrivateCredential // permission. java.security.AccessController.doPrivileged(new java.security. PrivilegedExceptionAction() { public Object run() throws java.lang.Exception { // Try not to add a null object to the Subject or an object // that already exists. if (myCustomObjectFinal != null && !subject.getPrivateCredentials(). contains(myCustomObjectFinal)) { // This call requires a special Java 2 Security permission, // see the JAAS API // documentation. subject.getPrivateCredentials().add(myCustomObjectFinal); } return null; } }); } catch (java.security.PrivilegedActionException e) { // Wraps the exception in a WSLoginFailedException java.lang.Throwable myException = e.getException(); throw new WSLoginFailedException (myException.getMessage(), myException); } } // Defines the login module variables com.acme.CustomObject myCustomObject = null; }

  2. Verify that the custom Java class implements the java.io.Serializable interface. An object that is added to the Subject must be serialized if we want the object to propagate. For example, the object must implement the java.io.Serializable interface. If the object is not serialized, the request does not fail, but the object does not propagate. To make sure an object that is added to the Subject is propagated, implement one of the token interfaces that is defined in Security attribute propagation or add attributes to one of the following existing default token implementations:

    AuthorizationToken

    Add attributes if they are user-specific.

    See Use the default authorization token.

    PropagationToken

    Add attributes that are specific to an invocation.

    See Use the default propagation token.

    If careful adding custom objects and follow all the steps to make sure that WAS can serialize and deserialize the object at each hop, then it is sufficient to use custom Java objects only.

  3. Verify that the custom Java class exists on all of the systems that might receive the request.

    When you add a custom object into the Subject and expect WAS to propagate the object, put the class definitions together in a JAR file and add the file to the APP_ROOT/lib/ext/ directory on all of the nodes where serialization or deserialization might occur. Also, verify that the Java class versions are the same.

  4. Verify that the custom login module is configured in all of the login configurations used in the environment where we need to add the custom object during a login. Any login configuration that interacts with WAS generates a Subject that might be propagated outbound for an EJB request. If we want WAS to propagate a custom object in all cases, make sure that the custom login module is added to every login configuration used in the environment.

    See Develop custom login modules for a system login configuration for JAAS.

  5. Verify that security attribute propagation is enabled on all of the downstream servers that receive the propagated information. When an EJB request is sent to a downstream server and security attribute propagation is disabled on that server, only the authentication token is sent for backwards compatibility. Therefore, review the configuration to verify that propagation is enabled in all of the cells that might receive requests. You must check several places in the admin console to make sure propagation is fully enabled.

    See Propagating security attributes among appservers.

  6. Add any custom objects to the propagation exclude list that you do not want to propagate. Configure a property to exclude the propagation of objects that match specific class names, package names, or both. For example, we can have a custom object that is related to a specific process. If the object is propagated, it does not contain valid information. You must tell WAS not to propagate this object. Complete the following steps to specify the object in the propagation exclude list, using the admin console:

    1. Click Security > Global security > Custom properties > New.

    2. Add com.ibm.ws.security.propagationExcludeList in the Name field.

    3. Add the name of the custom object in the Value field.

      We can add a list of custom objects to the propagation exclude list, separated by a colon (:). For example, we might enter com.acme.CustomLocalObject:com.acme.private.*. We can enter a class name such as com.acme.CustomLocalObject or a package name such as com.acme.private.*. In this example, WAS does not propagate any class that equals com.acme.CustomLocalObject or begins with com.acme.private.

      Although we can add custom objects to the propagation exclude list, be aware of a side effect. WAS stores the opaque token, or the serialized Subject contents, in a local cache for the life of the SSO token. The life of the SSO token, which has a default of two hours, is configured in the SSO properties on the admin console. The information that is added to the opaque token includes only the objects not in the exclude list.

      If the authentication cache does not match the SSO token timeout, configure the authentication cache properties. See Set the authentication cache. It is recommended that you make the authentication cache timeout value equal to the SSO token timeout.

 

Results

As a result of this task, custom Java serializable objects are propagated horizontally or downstream.

See on the differences between horizontal and downstream propagation, see Security attribute propagation.

 

Related concepts


Security attribute propagation

 

Related tasks


Develop custom login modules for a system login configuration for JAAS
Use the default authorization token
Use the default propagation token
Propagating security attributes among appservers
Implementing tokens for security attribute propagation

 

Related


Security: Links