#319466: SA-2008-47 (#295053): CSRF in cached forms.

includes/form.inc

@@ -100,7 +100,7 @@ function drupal_get_form($form_id) {
       array_unshift($args_temp, $form_id);
 
       $form = call_user_func_array('drupal_retrieve_form', $args_temp);
-      $form_build_id = 'form-' . md5(mt_rand());
+      $form_build_id = 'form-' . md5(uniqid(mt_rand(), TRUE));
       $form['#build_id'] = $form_build_id;
       drupal_prepare_form($form_id, $form, $form_state);
       // Store a copy of the unprocessed form for caching and indicate that it
@@ -221,10 +221,13 @@ function drupal_rebuild_form($form_id, &$form_state, $args, $form_build_id = NUL
 function form_get_cache($form_build_id, &$form_state) {
   if ($cached = cache_get('form_' . $form_build_id, 'cache_form')) {
     $form = $cached->data;
-    if ($cached = cache_get('storage_' . $form_build_id, 'cache_form')) {
-      $form_state['storage'] = $cached->data;
+    global $user;
+    if ((isset($form['#cache_token']) && drupal_valid_token($form['#cache_token'])) || (!isset($form['#cache_token']) && !$user->uid)) {
+      if ($cached = cache_get('storage_' . $form_build_id, 'cache_form')) {
+        $form_state['storage'] = $cached->data;
+      }
+      return $form;
     }
-    return $form;
   }
 }
 
@@ -234,7 +237,10 @@ function form_get_cache($form_build_id, &$form_state) {
 function form_set_cache($form_build_id, $form, $form_state) {
   // 6 hours cache life time for forms should be plenty.
   $expire = 21600;
-
+  global $user;
+  if ($user->uid) {
+    $form['#cache_token'] = drupal_get_token();
+  }
   cache_set('form_' . $form_build_id, $form, 'cache_form', REQUEST_TIME + $expire);
   if (!empty($form_state['storage'])) {
     cache_set('storage_' . $form_build_id, $form_state['storage'], 'cache_form', REQUEST_TIME + $expire);

modules/book/book.pages.inc

@@ -232,19 +232,16 @@ function book_remove_form_submit($form, &$form_state) {
  *   Prints the replacement HTML in JSON format.
  */
 function book_form_update() {
-  $cid = 'form_' . $_POST['form_build_id'];
+  $cached_form_state = array();
   $bid = $_POST['book']['bid'];
-  $cache = cache_get($cid, 'cache_form');
-  if ($cache) {
-    $form = $cache->data;
-
+  if ($form = form_get_cache($_POST['form_build_id'], $cached_form_state)) {
     // Validate the bid.
     if (isset($form['book']['bid']['#options'][$bid])) {
       $book_link = $form['#node']->book;
       $book_link['bid'] = $bid;
       // Get the new options and update the cache.
       $form['book']['plid'] = _book_parent_select($book_link);
-      cache_set($cid, $form, 'cache_form', $cache->expire);
+      form_set_cache($_POST['form_build_id'], $form, $cached_form_state);
       // Build and render the new select element, then return it in JSON format.
       $form_state = array();
       $form['#post'] = array();

modules/poll/poll.module

@@ -366,7 +366,9 @@ function poll_choice_js() {
   // not process it. We retreive the cached form, add the element, and resave.
   $form_build_id = $_POST['form_build_id'];
   $form_state = array('submitted' => FALSE);
-  $form = form_get_cache($form_build_id, $form_state);
+  if (!$form = form_get_cache($form_build_id, $form_state)) {
+    exit();
+  }
 
   $delta = count($_POST['choice']);
   $key = isset($form['#node']->choice) ? 'new:'. ($delta - count($form['#node']->choice)) : 'new:'. $delta;