The SSO-CAS Login Handler allows ti delegate authentication to a CAS server. It is different from the RemoteUser login handler in that it supports force authentication.
This guide assumes you have a running IdP, and that it has already been configured to use CAS. You can do it by following this : https://wiki.jasig.org/display/CASUM/Shibboleth-CAS+Integration.
To instruct your resources to use force authentication, see NativeSPSessionInitiator.

Download and installation

Download

You can either directly download the .JAR archive from https://sourcesup.renater.fr/frs/download.php/4086/ssocas-login-handler-0.1.jar or get the source code using subversion :

svn export https://subversion.renater.fr/ssocashandler/trunk/ ssocas-login-handler
cd ssocas-login-handler
mvn package

This will create the latest ssocas-login-handler-x.x.jar in the target/ directory.

Installation

The first step is to add the JAR (downloaded or obtained through the source code) into the library of your IdP's installation directory :

cp ssocas-login-handler-0.1.jar $IDP_INSTALL_DIR/lib

You will then have to re-install the IdP, but it's no use doing it right now since the following configuration modifications will also require a re-installation.

Configuration

Web applications

Modify the CAS client filters settings in $IDP_INSTALL_DIR/src/main/webapp/WEB-INF/web.xml (do not forget to modify the filter-mappings that were already defined):

    <!-- CAS Authentication Filter -->
	<filter> 
	 <filter-name>CAS Authentication Filter</filter-name>
	 <filter-class>org.jasig.cas.client.authentication.AuthenticationFilter</filter-class> 
	 <init-param>
	  <param-name>casServerLoginUrl</param-name>
	  <param-value>https://example.cas.server/cas/login</param-value> 
	 </init-param>
	</filter> 
 
	<!-- CAS Validation Filter --> 
	<filter> 
	 <filter-name>CAS Validation Filter</filter-name> 
	 <filter-class>org.jasig.cas.client.validation.Cas20ProxyReceivingTicketValidationFilter</filter-class> 
	 <init-param> 
	  <param-name>casServerUrlPrefix</param-name> 
	  <param-value>https://services-federation.renater.fr/cas</param-value> 
	 </init-param> 
	</filter> 
 
	<!-- CAS Authentication Filter - forceAuthn  -->
	<filter> 
	 <filter-name>CAS Authentication Filter - forceAuthn</filter-name> 
	 <filter-class>org.jasig.cas.client.authentication.AuthenticationFilter</filter-class> 
	 <init-param> 
	  <param-name>casServerLoginUrl</param-name> 
	  <param-value>https://example.cas.server/cas/login</param-value> 
	 </init-param> 
	 <init-param> 
	  <param-name>renew</param-name> 
	  <param-value>true</param-value> 
	 </init-param>
	</filter> 
 
	<!-- CAS Validation Filter - forceAuthn -->
	<filter> 
	 <filter-name>CAS Validation Filter - forceAuthn</filter-name> 
	 <filter-class>org.jasig.cas.client.validation.Cas20ProxyReceivingTicketValidationFilter</filter-class> 
	 <init-param> 
	  <param-name>casServerUrlPrefix</param-name> 
	  <param-value>https://services-federation.renater.fr/cas</param-value> 
	 </init-param> 
	 <init-param> 
	  <param-name>renew</param-name> 
	  <param-value>true</param-value> 
	 </init-param>
	</filter> 
 
 
	<!-- CAS HttpServletRequest Wrapper Filter --> 
	<filter> 
	 <filter-name>CAS HttpServletRequest Wrapper Filter</filter-name> 
	 <filter-class>org.jasig.cas.client.util.HttpServletRequestWrapperFilter</filter-class> 
	</filter> 
 
	<!-- CAS Assertion Thread Local Filter --> 
	<filter> 
	 <filter-name>CAS Assertion Thread Local Filter</filter-name> 
	 <filter-class>org.jasig.cas.client.util.AssertionThreadLocalFilter</filter-class> 
	</filter> 
 
	<!-- CAS Filters Mappings -->

    <filter-mapping> 
	 <filter-name>CAS Authentication Filter</filter-name> 
	 <url-pattern>/Authn/Cas/NoforceAuthn</url-pattern> 
	 <dispatcher>REQUEST</dispatcher>  
	 <dispatcher>FORWARD</dispatcher>  
	</filter-mapping> 
 
	<filter-mapping> 
	 <filter-name>CAS Validation Filter</filter-name> 
	 <url-pattern>/Authn/Cas/NoForceAuthn</url-pattern> 
	</filter-mapping> 
 
 
	<filter-mapping> 
	 <filter-name>CAS Authentication Filter - forceAuthn</filter-name> 
	 <url-pattern>/Authn/Cas/ForceAuthn</url-pattern>
	 <dispatcher>REQUEST</dispatcher>  
	 <dispatcher>FORWARD</dispatcher>  
	</filter-mapping> 
 
	<filter-mapping> 
	 <filter-name>CAS Validation Filter - forceAuthn</filter-name> 
	 <url-pattern>/Authn/Cas/ForceAuthn</url-pattern>
	</filter-mapping> 
 
 
	<filter-mapping> 
	 <filter-name>CAS HttpServletRequest Wrapper Filter</filter-name>  
	 <url-pattern>/Authn/Cas/*</url-pattern> 
	</filter-mapping> 
	<filter-mapping> 
	 <filter-name>CAS Assertion Thread Local Filter</filter-name>
	 <url-pattern>/Authn/Cas/*</url-pattern> 
	</filter-mapping>

Modify the remote user servlet mapping (still in this web.xml) :

    <servlet-mapping>
        <servlet-name>RemoteUserAuthHandler</servlet-name>
        <url-pattern>/Authn/Cas/*</url-pattern>
    </servlet-mapping>

Handlers

Define the CentralAuthnService login handler in $IDP_CONFIG_DIR/handler.xml :

Define the following namespace and schema in ProfileHandlerGroup :

    <ph:ProfileHandlerGroup xmlns:ph="urn:mace:shibboleth:2.0:idp:profile-handler"
			    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
			    xmlns:sclh="fr:renater:ssocashandler"
			    xsi:schemaLocation="urn:mace:shibboleth:2.0:idp:profile-handler classpath:/schema/shibboleth-2.0-idp-profile-handler.xsd
  									fr:renater:ssocashandler classpath:/schema/ssocasloginhandler.xsd">

Define the handler itself:

    <ph:LoginHandler xsi:type="sclh:CentralAuthnService" casFiltersPath="/Authn/Cas">
        <ph:AuthenticationMethod>urn:oasis:names:tc:SAML:2.0:ac:classes:unspecified</ph:AuthenticationMethod>
    </ph:LoginHandler>

You should also comment or delete the RemoteUser login handler definition, since the IdP will not use it anymore.

Deployment

You can now re-install the IdP :

cd $IDP_INSTALL_DIR
./install.sh

and restart your container to end the installation of the login handler.

SSO-CAS Login Handler