auth/cas: MDL-25062 CAS authentication plugin does not validate the CAS server certificate

The CAS protocol security model requires that you verify the cas server
certificate before you trust the answer (valid authentication and username
etc.).

Credit goes to Joachim Fritschi for reporting it and providing a patch.

auth/cas/auth.php

@@ -114,8 +114,12 @@ class auth_plugin_cas extends auth_plugin_base {
 // Connection to CAS server
 	 $this->connectCAS();
 
+     if($this->config->certificate_check && $this->config->certificate_path){
+         phpCAS::setCasServerCACert($this->config->certificate_path);
+     }else{
          // Don't try to validate the server SSL credentials
          phpCAS::setNoCasServerValidation();
+     }
 
 	  // Gestion de la connection CAS si acc�s direct d'un ent ou autre	
 	 if (phpCAS::checkAuthentication()) {
@@ -248,6 +252,10 @@ if ( !is_object($PHPCAS_CLIENT) ) {
             $config->logoutcas = '';
         if (!isset ($config->multiauth))
             $config->multiauth = '';
+        if (!isset ($config->certificate_check))
+            $config->certificate_check = '';
+        if (!isset ($config->certificate_path))
+            $config->certificate_path = '';
         // LDAP settings
         if (!isset($config->host_url))
             { $config->host_url = ''; }
@@ -290,6 +298,8 @@ if ( !is_object($PHPCAS_CLIENT) ) {
         set_config('proxycas',     $config->proxycas,     'auth/cas');
         set_config('logoutcas',     $config->logoutcas,     'auth/cas');
         set_config('multiauth',     $config->multiauth,     'auth/cas');
+        set_config('certificate_check',     $config->certificate_check,     'auth/cas');
+        set_config('certificate_path',     $config->certificate_path,     'auth/cas');
         // save LDAP settings
         set_config('host_url', $config->host_url, 'auth/cas');
         set_config('ldapencoding', $config->ldapencoding, 'auth/cas');

auth/cas/config.html

@@ -48,6 +48,14 @@
 
         $config->multiauth = '';
 
+    if (!isset ($config->certificate_check)) 
+
+        $config->certificate_check = '';
+
+    if (!isset ($config->certificate_path))
+
+        $config->certificate_path = '';
+
   // set to defaults if undefined (LDAP)
 
     if (!isset($config->host_url))
@@ -364,6 +372,44 @@ if (!function_exists('ldap_connect')) { // Is php4-ldap really there?
 
 
 
+<tr valign="top"  class="required">
+
+    <td align="right"><?php print_string('auth_cas_certificate_check_key', 'auth') ?>:</td>
+
+    <td>
+
+        <?php choose_from_menu ($yesno, 'certificate_check', $config->certificate_check, ''); ?>
+
+    </td>
+
+    <td><?php print_string('auth_cas_certificate_check', 'auth') ?></td>
+
+</tr>
+
+
+
+<tr valign="top" class="required">
+
+    <td align="right"><?php print_string('auth_cas_certificate_path_key', 'auth') ?>:</td>
+
+    <td>
+
+        <input name="certificate_path" type="text" size="30" value="<?php echo $config->certificate_path ?>" />
+
+        <?php if (isset($err['certificate_path'])) formerr($err['certificate_path']); ?>
+
+    </td>
+
+    <td>
+
+        <?php print_string('auth_cas_certificate_path', 'auth') ?>
+      
+    </td>
+
+</tr>
+
+
+
 <tr>
 
    <td colspan="2">

lang/en_utf8/auth.php

@@ -36,9 +36,13 @@ $string['auth_nologintitle'] = 'No login';
 $string['auth_cas_proxycas_key'] = "Proxy mode";
 $string['auth_cas_logoutcas_key'] = "Logout CAS";
 $string['auth_cas_multiauth_key'] = "Multi-authentication";
-$string['auth_cas_proxycas'] = "Turn this to 'yes'' if you use CASin proxy-mode";
-$string['auth_cas_logoutcas'] = "Turn this to 'yes'' if tou want to logout from CAS when you deconnect from Moodle";
-$string['auth_cas_multiauth'] = "Turn this to 'yes'' if you want to have multi-authentication (CAS + other authentication)";
+$string['auth_cas_certificate_check_key'] = "Server validation";
+$string['auth_cas_certificate_path_key'] = "Certificate path";
+$string['auth_cas_proxycas'] = "Turn this to ''yes'' if you use CASin proxy-mode";
+$string['auth_cas_logoutcas'] = "Turn this to ''yes'' if tou want to logout from CAS when you deconnect from Moodle";
+$string['auth_cas_multiauth'] = "Turn this to ''yes'' if you want to have multi-authentication (CAS + other authentication)";
+$string['auth_cas_certificate_check'] = "Turn this to ''yes'' if you want to validate the server certificate";
+$string['auth_cas_certificate_path'] = "Path of the CA chain file (PEM Format) to validate the server certificate";
 $string['accesCAS'] = "CAS users";
 $string['accesNOCAS'] = "other users";
 $string['CASform'] = "Authentication choice";