Configure authentication filters

The portal authentication filters can intercept...

• portal login
• logout
• session timeout
• request processing

...and redirect users to a specific URL.

• The filter chain concept
• Available Filter Chains
• Configure the filter chains
• Example of a custom filter

The filter chain concept

The authentication filters in the portal use the same pattern as defined by the J2EE servlet filter facility. Refer to The essentials of filters.

A default filter performs the default logic for a particular use case, for example, login. We can chain has a set of custom filters to be executed before that default filter. When the filter chain is invoked, it calls the first element in the chain (in the example CustomFilter1) and passes a chain object as an argument to the call. The filter implementation can then perform some operations before calling the appropriate method on the chain object to trigger the next element in the chain (CustomFilter2). This filter again can implement some individual logis that is executed before calling the next element. The last element of the chain is the predefined DefaultFilter that makes sure that the default logic for the respective use case is executed.

After a filter has been executed or if an exception is thrown, each filter returns to the one that has called it, so it is possible to implement a customized exception handling or perform additional operations after having called the successor. This way we can chain a custom set of filters. Each custom filter can perform operations before and after the following element(s) in the chain. We can specify the order and the fully qualified class names of the custom filters by portal configuration properties. For details about the authentication filters refer to Authentication Service. The portal ships only with the DefaultFilter implementations and enforces that they are always the last element in the chains; if there are no custom login filters defined, the default filters are the only element.

Available Filter Chains

Filter chains can be applied to the following events are applied to six types of events that concern the flows of Portal login, logout, and session handling...

Event	Filter chain action
Explicit login	Login by user name and password as represented by the interface... com.ibm.portal.auth.ExplicitLoginFilter For example, this can be a login using the login portlet or the login URL.
Implicit login	This can be when a user is already authenticated by WAS, but not yet to Portal. This is represented by the interface... com.ibm.portal.auth.ImplicitLoginFilter.
Explicit logout	The user triggers a logout action directly, for example by clicking the Logout button in the user interface, interface... com.ibm.portal.auth.ExplicitLogoutFilter
Implicit logout	This can be after a session timeout, or if an authenticated user accesses a public page, or if the user navigates to a virtual portal without being member of the associated user realm. This is represented by the interface... com.ibm.portal.auth.ImplicitLogoutFilter
Session Timeout	Called immediately after an idle timeout of the user session occurred. This is represented by the interface... com.ibm.portal.auth.SessionTimeoutFilter
Session Validation	Called for every request before actions are triggered and the page is rendered. This is represented by the interface ... com.ibm.portal.auth.SessionValidationFilter

Besides the session timeout filter, each of the previous filters has access to the HTTP request and response objects. A special context object can be used to share information between filters and set redirects that are executed after the filter chain has been processed. For more detailed information about each of the filter and the filter chain interfaces refer to the WebSphere Portal and the API JavaDoc documentation. See step 3 for a filter chain example.

Configure the filter chains

We can specify the order of filters for each filter chain by setting the following properties in the WP Authentication Service:

login.explicit.filterchain = colon or semicolon-separated list of fully qualified class names 
login.implicit.filterchain = colon or semicolon-separated list of fully qualified class names 
logout.explicit.filterchain = colon or semicolon-separated list of fully qualified class names 
logout.implicit.filterchain = colon or semicolon-separated list of fully qualified class names 
sessiontimeout.filterchain = colon or semicolon-separated list of fully qualified class names 
sessionvalidation.filterchain = colon or semicolon-separated list of fully qualified class names 

Use the properties to specify only the custom filter elements, as the default filter implementation is added implicitly by the Portal infrastructure. Thus, by default no value is set for the properties.

In addition, we can set properties in the WP Authentication Service according to the following pattern:

filterchain.properties.fully qualified class name of the filter implementation.property name 

This makes the value of this property available in the filter configuration object of the specified class using the key property name .

For details about setting portal configuration properties refer to Set service configuration properties.

Example of a custom filter

The following gives an example of a custom filter plugged into the filter chain for the explicit Portal login. The custom filter holds properties that define particular redirect URLs for particular user IDs and triggers the corresponding redirect if one of those users logged in successfully. To implement such an example...

1. Implement the com.ibm.portal.auth.ExplicitLoginFilter interface and make the class available to the portal class path by adding the JAR file to the extended classpath directory of the WebSphere Portal application: PORTAL_HOME/shared/app . For an example for how to implement the methods of the interface refer to the following code sample:

   package com.ibm.portal.example;
   
   public class UserRedirectLoginFilter implements ExplicitLoginFilter 
   {
       // hash map to store the mappings from user id to redirect URL        
       private java.util.Map userToRedirectURLs = new java.util.HashMap();
   
       public void init(SecurityFilterConfig filterConfig)
          throws SecurityFilterInitException 
       {
           // iterate the list of init parameters and store the mappings of user to redirect urls for         
           (java.util.Iterator it = filterConfig.getInitParameterNames(); it.hasNext(); ) 
           {
              String currentParameter = (String)it.next();
              userToRedirectURLs.put(currentParameter, filterConfig.getInitParameter(currentParameter));
           }
       }
   
       public void login(HttpServletRequest req, 
                         HttpServletResponse resp, 
                         String userID, char[] password,
                         FilterChainContext portalLoginContext, 
                         Subject subject,
                         String realm, ExplicitLoginFilterChain chain)
                   throws LoginException, 
                          WSSecurityException,
                          PasswordInvalidException, 
                          UserIDInvalidException,
                          AuthenticationFailedException, 
                          AuthenticationException,
                          SystemLoginException, 
                          com.ibm.portal.auth.exceptions.LoginException 
       {
           // call the next element in the filter chain to trigger the default login            
           chain.login(req, resp, userID, password, portalLoginContext, subject, realm);
   
           // if no exception occured, the login was successful            
           if (userToRedirectURLs.containsKey(userID)) 
           {
               // set the redirect url for the user if we have an entry            
               portalLoginContext.setRedirectURL((String)userToRedirectURLs.get(userID));
           }
       }
   
       public void destroy() 
       {
           // nothing to do here     
       }
   }
   

2. Specify the class name of the custom filter in the WP Authentication Service properties:

   login.explicit.filterchain=com.ibm.portal.example.UserRedirectLoginFilter
   

3. Redirect URLs for individual user IDs, specify your custom set of properties for this class accordingly. Example:

   filterchain.properties.com.ibm.portal.example.UserRedirectLoginFilter.alice=/wps/myportal/pageA
   filterchain.properties.com.ibm.portal.example.UserRedirectLoginFilter.bob=/wps/myportal/pageB
   

4. Restart the portal.

The new filter for the explicit login is now available. Users defined in the properties will be redirected to the specified URL after logging in through the login portlet or login URL.

Parent: Configure portal behavior