Duncan Mills

Listing 5 Indicating that a Web resource requires SSL

<user-data-constraint>
     <transport-guarantee>CONFIDENTIAL</transport-guarantee>
</user-data-constraint>

Though J2EE Web resources can be configured to require HTTPS this way, the J2EE specification doesn't demand that Web containers respond by automatically switching protocols. Instead, J2EE containers usually return an HTTP error message to indicate a failed user request. Individual J2EE containers like Apache Tomcat provide native support for switching between the HTTP and HTTPS protocol. However, you ought to be aware that such solutions aren't portable to other J2EE containers.

Page Navigation in JavaServer Faces
So we've seen how basic container-managed security is configured through the use of logical application roles protecting a URL pattern. Now let's look at how JSF manages page navigation and how the principles of container-managed security can be applied.

Page navigation in JavaServer Faces is defined in the WEB-INF\faces-config.xml file, where the JSF NavigationHandler component uses it.

The application developer configures navigation in JSF either as a server-side forward or, if the <redirect/> element is included in the navigation case, as a browser redirect.

Listing 6 JSF navigation case issuing a redirect request for page navigation

<navigation-case>
     <from-outcome>success</from-outcome>
     <to-view-id>/Departments.jsp</to-view-id>
     <redirect/>
</navigation-case>

Server-side forwards are the de facto default implementation of navigation cases in JSF, but such navigation harbors two side effects: first, the URL won't change, and so pages in the application aren't bookmarkable; and secondly, there's no new submission of a URL pattern for container-managed security to be applied to. As a consequence, if you've implemented container-managed security, you'll have to use <redirect/> explicitly on any navigation cases that have to trigger a security check across role boundaries.

It should be clear by now that authorizing pages and implementing a secure channel for communication isn't easy to achieve in JavaServer Faces. And using JAAS instead of container-managed security offers no better solution. The answer lies in a combined approach: a reusable custom security implementation specifically designed to work with JSF based on JAAS or container-managed J2EE security.

Where Does Security Belong in JavaServer Faces?
As we've mentioned, JSF has no real security infrastructure built into it and this leaves the developer to wonder where and how to implement security. The examples that address user authentication in JSF (using JAAS, for instance) don't cover the important task of page authorization. (See Figure 1)

The authorization enforcer security pattern demands that authorization be handled in a central location. For many Web applications, this central location is a ServletFilter associated with the application front controller. In JSF, though, security is best implemented using the built-in extension points provided by the JavaServer Faces architecture.

The two candidate approaches for implementing security in JSF are:

• A custom ViewHandler that decorates the default ViewHandler and also adds security checks to the createView and restoreView methods
• A PhaseListener that adds security evaluation to the restoreView and invokeAction phases

Adding security to a Viewhandler doesn't appear to be an ideal solution because there's no guarantee that a security ViewHandler will be executed before any other custom ViewHandlers that have been registered. If another ViewHandler is present and writing to the servlet response stream then security-related actions such as redirecting a request to the HTTPS port would result in illegal state exceptions. So it seems that a custom PhaseListener is the better approach to adopt.

Developing a JavaServer Faces PhaseListener for Security
JavaServer Faces executes in a rich request lifecycle composed of a sequence of individual phase events: Restore View, Apply Request Values, Process Validation, Update Model Values, Invoke Application, and Render Response. PhaseListeners in JavaServer Faces are Java classes configured in the faces-config.xml file and notified when a specific phase event of interest occurs. (See Figure 2)

To execute custom logic before and after a specific event, custom application code is added to the beforePhase and afterPhase methods of a PhaseListener. Both methods accept an input argument of a PhaseEvent to provide information about the calling phase, for example, a phase ID. The third method developers have to implement is getPhaseId. The getPhaseId method is used to declare which phases the listener is actually interested in being notified about.

Listing 7 Custom PhaseListener listening to any event and implementing the JSf PhaseListener interface

public class J2EESecurityPhaseListener implements PhaseListener
{
     public SecurityPhaseListener() { }
     public void afterPhase(PhaseEvent phaseEvent) { }
     public void beforePhase(PhaseEvent phaseEvent){ }
     public PhaseId getPhaseId() {return PhaseId.ANY_PHASE;}
}

An application can have more than one PhaseListener configured. PhaseListeners are configured in the <lifecycle> element of the faces-config.xml configuration file.

Listing 8 PhaseListener configuration in faces-config.xml

<lifecycle>
    <phase-listener>
       com.groundside.jsf.J2EESecurityPhaseListener
    </phase-listener>
</lifecycle>

Java IDEs like Oracle JDeveloper provide visual editors to simplify this configuration of the faces-config.xml file.

A J2EE security PhaseListener - J2EESecurityPhaseListener
The J2EESecurityPhaseListener is a custom PhaseListener that implements page authorization for the JSF restoreView and invokeAction phases using container-managed J2EE security roles. JSF doesn't let PhaseListener register for multiple selected events. Either a PhaseListener registers for one specific event or it registers for all events. So the J2EESecurityPhaseListener listener is registered to listen to any phase, but responds only to the RESTORE_VIEW and INVOKE_APPLICATION phases.