Using the REMOTE_USER

package org.jasig.cas.adaptors.generic;

import org.jasig.cas.authentication.principal.Credentials;
import org.jasig.cas.authentication.principal.Principal;

/**
 * Credentials that bear the fully resolved and authenticated Principal.
 * 
 * These Credentials are a mechanism to pass into CAS information about an
 * authentication and Principal resolution that has already happened in layers
 * in front of CAS, e.g. by means of a Java Servlet Filter.
 * 
 * DO NOT accept these Credentials from arbitrary web-servicy calls to CAS.
 * Rather, the code constructing these Credentials must be trusted.
 */
public class PrincipalBearingCredentials 
    implements Credentials {

    private Principal principal;
    
    public Principal getPrincipal(){
        return this.principal;
    }
    
    public void setPrincipal(Principal principal) {
        this.principal = principal;
    }
    
}

/**
 * Extracts the remote user from the request into the PrincipalBearingCredentials.
 * @version $Revision:$ $Date:$
 */
public class RemoteUserCredentialsBinder 
    implements CredentialsBinder {

    public void bind(HttpServletRequest request, Credentials credentials) {
        String remoteUser = request.getRemoteUser();
        
        SimplePrincipal principal = new SimplePrincipal(remoteUser);
        ((PrincipalBearingCredentials) credentials).setPrincipal(principal);
        
    }

    public boolean supports(Class clazz) {
        return PrincipalBearingCredentials.class.equals(clazz);
    }

}

/**
 * AuthenticationHandler which authenticates Principal-bearing credentials.
 * Authentication must have occured at the time the Principal-bearing credentials
 * were created, so we perform no further authentication.
 * 
 */
public class PrincipalBearingCredentialsAuthnHandler 
    implements AuthenticationHandler {

    public boolean authenticate(Credentials credentials) 
        throws AuthenticationException {
        
        // we're assuming supports() was called and we supported the
        // credentials, so they must be PrincipalBearingCredentials.
        return true;
    }

    public boolean supports(Credentials credentials) {
        return credentials instanceof PrincipalBearingCredentials;
    }

}

package org.jasig.cas.adaptors.generic;

import org.jasig.cas.authentication.principal.Credentials;
import org.jasig.cas.authentication.principal.CredentialsToPrincipalResolver;
import org.jasig.cas.authentication.principal.Principal;

/**
 * Extracts the Principal out of PrincipalBearingCredentials.
 */
public class PrincipalBearingCredentialsToPrincipalResolver 
    implements CredentialsToPrincipalResolver {

    public Principal resolvePrincipal(Credentials credentials) {
        return ((PrincipalBearingCredentials) credentials).getPrincipal();
    }

    public boolean supports(Credentials credentials) {
        return credentials instanceof PrincipalBearingCredentials;
    }

}

<property name="authenticationHandlers">
    <list>
        <bean 
         class="org.jasig.cas.authentication.handler.support.HttpBasedServiceCredentialsAuthenticationHandler" />
	<bean
	class="org.jasig.cas.adaptors.generic.PrincipalBearingCredentialsAuthnHandler" />
    </list>
</property>

<property name="credentialsToPrincipalResolvers">
    <list>
        <bean
            class="org.jasig.cas.authentication.principal.PrincipalBearingCredentialsToPrincipalResolver" />
	<bean
            class="org.jasig.cas.authentication.principal.HttpBasedServiceCredentialsToPrincipalResolver" />
    </list>
</property>

<bean
    id="loginFormAction"
    class="org.jasig.cas.web.flow.LoginFormAction">
    <property
        name="centralAuthenticationService"
        ref="centralAuthenticationService" />
    <property
        name="credentialsBinder">
        <bean 
            class="org.jasig.cas.adaptors.generic.RemoteUserCredentialsBinder"/>
    </property>
    <property
        name="formObjectClass"
        value="org.jasig.cas.adaptors.generic.PrincipalBearingCredentials" />
</bean>

<filter>
  <filter-name>CAS Filter</filter-name>
  <filter-class>edu.yale.its.tp.cas.client.filter.CASFilter</filter-class>
  <init-param>
    <param-name>edu.yale.its.tp.cas.client.filter.loginUrl</param-name>
    <param-value>https://secure.its.yale.edu/cas/login</param-value>
  </init-param>
  <init-param>
    <param-name>edu.yale.its.tp.cas.client.filter.validateUrl</param-name>
    <param-value>https://secure.its.yale.edu/cas/serviceValidate</param-value>
  </init-param>
  <init-param>
    <param-name>edu.yale.its.tp.cas.client.filter.serverName</param-name>
    <param-value>hkg2.cis.yale.edu:8080</param-value>
  </init-param>
  <init-param>
	<param-name>edu.yale.its.tp.cas.client.filter.wrapRequest</param-name>
	<param-value>true</param-value>
  </init-param>
</filter>

<filter-mapping>
  <filter-name>CAS Validate Filter</filter-name>
  <url-pattern>/login</url-pattern>
</filter-mapping>