Configure authentication filters


Overview

The portal authentication filters are a set of plug-in points. You can use them to...


The filter chain concept

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

Trigger of filter chain, |                        |
   for example explicit  |   CustomFilter1        |
   login or logout      ---> next(..., chain)     |                         |
                         |   {                    |                         |
                         |   do something         |   CustomFilter2         |
                         |   chain.next(...)     ---> next(..., chain)      |
                         |                        |   {                     |   
                         |                        |   do something          |   DefaultFilter
                         |                        |   chain.next(...)      ---> next(..., chain)
                         |                        |                         |   { 
                         |                        |                         |   // Execute the default logic
                         |                        |   do something        <---  }
                         |   do something       <---  }                     |  
Redirect, exception,   <--- }                     |  
   or continue           |

A default filter performs the default logic for a particular use case, for example, login. You can chain 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 logic 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 you can chain a custom set of filters. Each custom filter can perform operations before and after the following element(s) in the chain. You 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

The filter chain concept described above is applied to six types of events that concern the flows of Portal login, logout, and session handling. This provides a flexible approach to plug custom logic to each of those flows. In particular, there are filter chains for the following events:


Configure the filter chains

To 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, you 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 by 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 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. To define the redirect URLs for individual user IDs, specify 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


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