Allow clean background:url(...) styles in safe mode. This will make Roundcube pass the Email Standards Acid Test

3 files changed, 25 insertions, 14 deletions

diff --git a/program/include/main.inc b/program/include/main.inc
index 8aa38c8d1..2d18567e7 100644
--- a/program/include/main.inc
+++ b/program/include/main.inc
@@ -883,19 +883,19 @@ function rcmail_get_edit_field($col, $value, $attrib, $type='text')
  * @param string Container ID to use as prefix
  * @return string Modified CSS source
  */
-function rcmail_mod_css_styles($source, $container_id)
+function rcmail_mod_css_styles($source, $container_id, $allow_remote=false)
   {
   $last_pos = 0;
   $replacements = new rcube_string_replacer;
 
   // ignore the whole block if evil styles are detected
-  $stripped = preg_replace('/[^a-z\(:;]/', '', rcmail_xss_entity_decode($source));
-  if (preg_match('/expression|behavior|url\(|import[^a]/', $stripped))
+  $source = rcmail_xss_entity_decode($source);
+  $stripped = preg_replace('/[^a-z\(:;]/i', '', $source);
+  $evilexpr = 'expression|behavior' . (!$allow_remote ? '|url\(|import[^a]' : '');
+  if (preg_match("/$evilexpr/i", $stripped) // don't accept No-Gos
+      || (strpos($stripped, 'url(') && !preg_match('!url\s*\([ "\'](https?:)//[a-z0-9/._+-]+["\' ]\)!Ui', $source))) // only allow clean urls
     return '/* evil! */';
 
-  // remove css comments (sometimes used for some ugly hacks)
-  $source = preg_replace('!/\*(.+)\*/!Ums', '', $source);
-
   // cut out all contents between { and }
   while (($pos = strpos($source, '{', $last_pos)) && ($pos2 = strpos($source, '}', $pos)))
   {
@@ -937,7 +937,7 @@ function rcmail_xss_entity_decode($content)
 {
   $out = html_entity_decode(html_entity_decode($content));
   $out = preg_replace_callback('/\\\([0-9a-f]{4})/i', 'rcmail_xss_entity_decode_callback', $out);
-  $out = preg_replace('#/\*.*\*/#Um', '', $out);
+  $out = preg_replace('#/\*.*\*/#Ums', '', $out);
   return $out;
 }
 
diff --git a/program/lib/washtml.php b/program/lib/washtml.php
index 9c8625f30..8bbc136e1 100644
--- a/program/lib/washtml.php
+++ b/program/lib/washtml.php
@@ -243,7 +243,7 @@ class washtml
       case XML_ELEMENT_NODE: //Check element
         $tagName = strtolower($node->tagName);
         if ($callback = $this->handlers[$tagName]) {
-          $dump .= call_user_func($callback, $tagName, $this->wash_attribs($node), $this->dumpHtml($node));
+          $dump .= call_user_func($callback, $tagName, $this->wash_attribs($node), $this->dumpHtml($node), $this);
         }
         else if (isset($this->_html_elements[$tagName])) {
           $content = $this->dumpHtml($node);
@@ -301,6 +301,14 @@ class washtml
     return $this->dumpHtml($node);
   }
 
+  /**
+   * Getter for config parameters
+   */
+  public function get_config($prop)
+  {
+      return $this->config[$prop];
+  }
+
 }
 
 ?>
diff --git a/program/steps/mail/func.inc b/program/steps/mail/func.inc
index 1063c8ddf..62474f16a 100644
--- a/program/steps/mail/func.inc
+++ b/program/steps/mail/func.inc
@@ -822,7 +822,7 @@ function rcmail_plain_body($body, $flowed=false)
 /**
  * Callback function for washtml cleaning class
  */
-function rcmail_washtml_callback($tagname, $attrib, $content)
+function rcmail_washtml_callback($tagname, $attrib, $content, $washtml)
 {
   switch ($tagname) {
     case 'form':
@@ -834,8 +834,11 @@ function rcmail_washtml_callback($tagname, $attrib, $content)
       $stripped = preg_replace('/[^a-zA-Z\(:;]/', '', rcmail_xss_entity_decode($content));
 
       // now check for evil strings like expression, behavior or url()
-      if (!preg_match('/expression|behavior|url\(|import[^a]/', $stripped)) {
-        $out = html::tag('style', array('type' => 'text/css'), $content);
+      if (!preg_match('/expression|behavior/i', $stripped)) {
+        if (!$washtml->get_config('allow_remote') && preg_match('/url\(|import[^a]/i', $stripped))
+          $washtml->extlinks = true;
+        else
+          $out = html::tag('style', array('type' => 'text/css'), $content);
         break;
       }
 
@@ -1021,7 +1024,7 @@ function rcmail_message_body($attrib)
         $body = rcmail_print_body($part, array('safe' => $safe_mode, 'plain' => !$CONFIG['prefer_html']));
 
         if ($part->ctype_secondary == 'html') {
-          $body = rcmail_html4inline($body, $attrib['id'], 'rcmBody', $attrs);
+          $body = rcmail_html4inline($body, $attrib['id'], 'rcmBody', $attrs, $safe_mode);
           $div_attr = array('class' => 'message-htmlpart');
           $style = array();
 
@@ -1104,7 +1107,7 @@ function rcmail_resolve_base($body)
 /**
  * modify a HTML message that it can be displayed inside a HTML page
  */
-function rcmail_html4inline($body, $container_id, $body_id='', &$attributes=null)
+function rcmail_html4inline($body, $container_id, $body_id='', &$attributes=null, $allow_remote=false)
 {
   $last_style_pos = 0;
   $cont_id = $container_id.($body_id ? ' div.'.$body_id : '');
@@ -1116,7 +1119,7 @@ function rcmail_html4inline($body, $container_id, $body_id='', &$attributes=null
 
     // replace all css definitions with #container [def]
     $styles = rcmail_mod_css_styles(
-      substr($body, $pos, $pos2-$pos), $cont_id);
+      substr($body, $pos, $pos2-$pos), $cont_id, $allow_remote);
 
     $body = substr_replace($body, $styles, $pos, $pos2-$pos);
     $last_style_pos = $pos2;