Improve HTML sanitization with washtml

4 files changed, 128 insertions, 51 deletions

diff --git a/program/include/rcube_message.php b/program/include/rcube_message.php
index 6654c3f90..48f999785 100644
--- a/program/include/rcube_message.php
+++ b/program/include/rcube_message.php
@@ -57,7 +57,6 @@ class rcube_message
     list(, $this->sender) = each($this->imap->decode_address_list($this->headers->from));
     
     $this->set_safe((intval($_GET['_safe']) || $_SESSION['safe_messages'][$uid]));
-    $this->set_safe(0);
     
     $this->opt = array(
       'safe' => $this->is_safe,
diff --git a/program/lib/washtml.php b/program/lib/washtml.php
index dfd36d224..340dc93f3 100644
--- a/program/lib/washtml.php
+++ b/program/lib/washtml.php
@@ -33,7 +33,8 @@
  *
  * SYNOPSIS:
  *
- * washtml::wash($html, $config, $full);
+ * $washer = new washtml($config);
+ * $washer->wash($html);
  * It return a sanityzed string of the $html parameter without html and head tags.
  * $html is a string containing the html code to wash.
  * $config is an array containing options:
@@ -42,11 +43,11 @@
  *   $config['show_washed'] is a boolean to include washed out attributes as x-washed
  *   $config['cid_map'] is an array where cid urls index urls to replace them.
  *   $config['charset'] is a string containing the charset of the HTML document if it is not defined in it.
- * $full is a reference to a boolean that is set to true if no remote images are removed. (FE: show remote images link)
+ * $washer->extlinks is a reference to a boolean that is set to true if remote images were removed. (FE: show remote images link)
  *
  * INTERNALS:
  *
- * Only tags and attributes in the globals $html_elements and $html_attributes
+ * Only tags and attributes in the static lists $html_elements and $html_attributes
  * are kept, inline styles are also filtered: all style identifiers matching
  * /[a-z\-]/i are allowed. Values matching colors, sizes, /[a-z\-]/i and safe
  * urls if allowed and cid urls if mapped are kept.
@@ -72,15 +73,51 @@
 
 class washtml
 {
+  /* Allowed HTML elements (default) */
+  static $html_elements = array('a', 'abbr', 'acronym', 'address', 'area', 'b', 'basefont', 'bdo', 'big', 'blockquote', 'br', 'caption', 'center', 'cite', 'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'dir', 'div', 'dl', 'dt', 'em', 'fieldset', 'font', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'ins', 'label', 'legend', 'li', 'map', 'menu', 'ol', 'p', 'pre', 'q', 's', 'samp', 'small', 'span', 'strike', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'tr', 'tt', 'u', 'ul', 'var', 'img');
+  
+  /* Ignore these HTML tags but process their content */
+  static $ignore_elements = array('html', 'body');
+  
+  /* Allowed HTML attributes */
+  static $html_attribs = array('name', 'class', 'title', 'alt', 'width', 'height', 'align', 'nowrap', 'col', 'row', 'id', 'rowspan', 'colspan', 'cellspacing', 'cellpadding', 'valign', 'bgcolor', 'color', 'border', 'bordercolorlight', 'bordercolordark', 'face', 'marginwidth', 'marginheight', 'axis', 'border', 'abbr', 'char', 'charoff', 'clear', 'compact', 'coords', 'vspace', 'hspace', 'cellborder', 'size', 'lang', 'dir', 'background');  
+  
+  /* State for linked objects in HTML */
+  public $extlinks = false;
+
+  /* Current settings */
+  private $config = array();
 
+  /* Registered callback functions for tags */
+  private $handlers = array();
+  
   /* Allowed HTML elements */
-  static $html_elements = array('a', 'abbr', 'acronym', 'address', 'area', 'b', 'basefont', 'bdo', 'big', 'blockquote', 'body', 'br', 'caption', 'center', 'cite', 'code', 'col', 'colgroup', 'dd', 'del', 'dfn', 'dir', 'div', 'dl', 'dt', 'em', 'fieldset', 'font', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'ins', 'label', 'legend', 'li', 'map', 'menu', 'ol', 'p', 'pre', 'q', 's', 'samp', 'small', 'span', 'strike', 'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th', 'thead', 'title', 'tr', 'tt', 'u', 'ul', 'var', 'img');
+  private $_html_elements = array();
 
-  /* Allowed HTML attributes */
-  static $html_attribs = array('name', 'class', 'title', 'alt', 'width', 'height', 'align', 'nowrap', 'col', 'row', 'id', 'rowspan', 'colspan', 'cellspacing', 'cellpadding', 'valign', 'bgcolor', 'color', 'border', 'bordercolorlight', 'bordercolordark', 'face', 'marginwidth', 'marginheight', 'axis', 'border', 'abbr', 'char', 'charoff', 'clear', 'compact', 'coords', 'vspace', 'hspace', 'cellborder', 'size', 'lang', 'dir', 'background');
+  /* Ignore these HTML tags but process their content */
+  private $_ignore_elements = array();
 
+  /* Allowed HTML attributes */
+  private $_html_attribs = array();
+  
+
+  /* Constructor */
+  public function __construct($p = array()) {
+    $this->_html_elements = array_flip((array)$p['html_elements']) + array_flip(self::$html_elements) ;
+    $this->_html_attribs = array_flip((array)$p['html_attribs']) + array_flip(self::$html_attribs);
+    $this->_ignore_elements = array_flip((array)$p['ignore_elements']) + array_flip(self::$ignore_elements);
+    unset($p['html_elements'], $p['html_attribs'], $p['ignore_elements']);
+    $this->config = $p + array('show_washed'=>true, 'allow_remote'=>false, 'cid_map'=>array());
+  }
+  
+  /* Register a callback function for a certain tag */
+  public function add_callback($tagName, $callback)
+  {
+    $this->handlers[$tagName] = $callback;
+  }
+  
   /* Check CSS style */
-  static function wash_style($style, $config, &$full) {
+  private function wash_style($style) {
     $s = '';
 
     foreach(explode(';', $style) as $declaration) {
@@ -96,12 +133,12 @@ class washtml
                  ')\s*/i', $str, $match)) {
           if($match[2]) {
             if(preg_match('/^(http|https|ftp):.*$/i', $match[2], $url)) {
-              if($config['allow_remote'])
+              if($this->config['allow_remote'])
                 $value .= ' url(\''.htmlspecialchars($url[0], ENT_QUOTES).'\')';
               else
-                $full = false;
+                $this->extlinks = true;
             } else if(preg_match('/^cid:(.*)$/i', $match[2], $cid))
-              $value .= ' url(\''.htmlspecialchars($config['cid_map']['cid:'.$cid[1]], ENT_QUOTES) . '\')';
+              $value .= ' url(\''.htmlspecialchars($this->config['cid_map']['cid:'.$cid[1]], ENT_QUOTES) . '\')';
           } else if($match[0] != 'url' && $match[0] != 'rbg')//whitelist ?
             $value .= ' ' . $match[0];
           $str = substr($str, strlen($match[0]));
@@ -114,39 +151,39 @@ class washtml
   }
 
   /* Take a node and return allowed attributes and check values */
-  static function wash_attribs($node, $config, &$full) {
+  private function wash_attribs($node) {
     $t = '';
     $washed;
 
     foreach($node->attributes as $key => $plop) {
       $key = strtolower($key);
       $value = $node->getAttribute($key);
-      if((in_array($key, self::$html_attribs)) ||
+      if(isset($this->_html_attribs[$key]) ||
          ($key == 'href' && preg_match('/^(http|https|ftp|mailto):.*/i', $value)))
         $t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
-      else if($key == 'style' && ($style = self::wash_style($value, $config, $full)))
+      else if($key == 'style' && ($style = $this->wash_style($value)))
         $t .= ' style="' . $style . '"';
       else if($key == 'src' && strtolower($node->tagName) == 'img') { //check tagName anyway
         if(preg_match('/^(http|https|ftp):.*/i', $value)) {
-          if($config['allow_remote'])
+          if($this->config['allow_remote'])
             $t .= ' ' . $key . '="' . htmlspecialchars($value, ENT_QUOTES) . '"';
           else {
-            $full = false;
-            if ($config['blocked_src'])
-              $t .= ' src="' . htmlspecialchars($config['blocked_src'], ENT_QUOTES) . '"';
+            $this->extlinks = true;
+            if ($this->config['blocked_src'])
+              $t .= ' src="' . htmlspecialchars($this->config['blocked_src'], ENT_QUOTES) . '"';
           }
         } else if(preg_match('/^cid:(.*)$/i', $value, $cid))
-          $t .= ' ' . $key . '="' . htmlspecialchars($config['cid_map']['cid:'.$cid[1]], ENT_QUOTES) . '"';
+          $t .= ' ' . $key . '="' . htmlspecialchars($this->config['cid_map']['cid:'.$cid[1]], ENT_QUOTES) . '"';
       } else
         $washed .= ($washed?' ':'') . $key;
     }
-    return $t . ($washed && $config['show_washed']?' x-washed="'.$washed.'"':'');
+    return $t . ($washed && $this->config['show_washed']?' x-washed="'.$washed.'"':'');
   }
 
   /* The main loop that recurse on a node tree.
    * It output only allowed tags with allowed attributes
    * and allowed inline styles */
-  static function dumpHtml($node, $config, &$full) {
+  private function dumpHtml($node) {
     if(!$node->hasChildNodes())
       return '';
 
@@ -157,23 +194,31 @@ class washtml
       switch($node->nodeType) {
       case XML_ELEMENT_NODE: //Check element
         $tagName = strtolower($node->tagName);
-        if(in_array($tagName, self::$html_elements)) {
-          $content = self::dumpHtml($node, $config, $full);
-          $dump .= '<' . $tagName . self::wash_attribs($node, $config, $full) .
+        if($callback = $this->handlers[$tagName]) {
+          $dump .= call_user_func($callback, $tagName, $this->wash_attribs($node), $this->dumpHtml($node));
+        } else if(isset($this->_html_elements[$tagName])) {
+          $content = $this->dumpHtml($node);
+          $dump .= '<' . $tagName . $this->wash_attribs($node) .
             ($content?">$content</$tagName>":' />');
-        } else if($tagName == 'html' || $tagName == 'body') {
-          $dump .= self::dumpHtml($node, $config, $full); //Just ignored
+        } else if(isset($this->_ignore_elements[$tagName])) {
+          $dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' ignored -->';
+          $dump .= $this->dumpHtml($node); //Just ignored
         } else
           $dump .= '<!-- ' . htmlspecialchars($tagName, ENT_QUOTES) . ' not allowed -->';
         break;
+      case XML_CDATA_SECTION_NODE:
+        $dump .= $node->nodeValue;
+        break;
       case XML_TEXT_NODE:
         $dump .= htmlspecialchars($node->nodeValue);
         break;
       case XML_HTML_DOCUMENT_NODE:
-        $dump .= self::dumpHtml($node, $config, $full);
+        $dump .= $this->dumpHtml($node);
+        break;
+      case XML_DOCUMENT_TYPE_NODE:
         break;
-      case XML_DOCUMENT_TYPE_NODE: break;
       default:
+        $dump . '<!-- node type ' . $node->nodeType . ' -->';
       }
     } while($node = $node->nextSibling);
 
@@ -182,13 +227,12 @@ class washtml
 
   /* Main function, give it untrusted HTML, tell it if you allow loading
    * remote images and give it a map to convert "cid:" urls. */
-  static function wash($html, $config=array(), &$full=true) {
-    $config += array('show_washed'=>true, 'allow_remote'=>false, 'cid_map'=>array());
+  public function wash($html) {
     //Charset seems to be ignored (probably if defined in the HTML document)
-    $node = new DOMDocument('1.0', $config['charset']);
-    $full = true;
+    $node = new DOMDocument('1.0', $this->config['charset']);
+    $this->extlinks = false;
     @$node->loadHTML($html);
-    return self::dumpHtml($node, $config, $full);
+    return $this->dumpHtml($node);
   }
 
 }
diff --git a/program/steps/mail/func.inc b/program/steps/mail/func.inc
index 58c9c8bd7..36605894a 100644
--- a/program/steps/mail/func.inc
+++ b/program/steps/mail/func.inc
@@ -539,12 +539,14 @@ function rcmail_get_messagecount_text($count=NULL, $page=NULL)
  * @param bool  True if part should be converted to plaintext
  * @return string Formatted HTML string
  */
-function rcmail_print_body($part, $safe=false, $plain=false)
+function rcmail_print_body($part, $p = array())
 {
   global $REMOTE_OBJECTS;
   
+  $p += array('safe' => false, 'plain' => false, 'inline_html' => true);
+  
   // convert html to text/plain
-  if ($part->ctype_secondary == 'html' && $plain) {
+  if ($part->ctype_secondary == 'html' && $p['plain']) {
     $txt = new html2text($part->body, false, true);
     $body = $txt->get_text();
     $part->ctype_secondary = 'plain';
@@ -553,25 +555,40 @@ function rcmail_print_body($part, $safe=false, $plain=false)
   else if ($part->ctype_secondary == 'html') {
     // charset was converted to UTF-8 in rcube_imap::get_message_part() -> change charset specification in HTML accordingly
     $html = $part->body; 
-    if(preg_match('/(\s+content=[\'"]\w+\/\w+;\s+charset)=([a-z0-9-]+)/i', $html)) 
-      $html = preg_replace('/(\s+content=[\'"]\w+\/\w+;\s+charset)=([a-z0-9-]+)/i', '\\1='.RCMAIL_CHARSET, $html); 
+    if (preg_match('/(\s+content=[\'"]\w+\/\w+;\s*charset)=([a-z0-9-]+)/i', $html)) 
+      $html = preg_replace('/(\s+content=[\'"]\w+\/\w+;\s*charset)=([a-z0-9-]+)/i', '\\1='.RCMAIL_CHARSET, $html); 
     else {
       // add <head> for malformed messages, washtml cannot work without that
-      if (!preg_match('/<head>(.*)<\/head>/m', $html))
+      if (!preg_match('/<head>(.*)<\\/head>/Uims', $html))
         $html = '<head></head>' . $html;
       $html = substr_replace($html, '<meta http-equiv="Content-Type" content="text/html; charset='.RCMAIL_CHARSET.'" />', intval(stripos($html, '</head>')), 0);
     }
-
+    
     // clean HTML with washhtml by Frederic Motte
-    $body = washtml::wash($html, array(
+    $wash_opts = array(
       'show_washed' => false,
-      'allow_remote' => $safe,
+      'allow_remote' => $p['safe'],
       'blocked_src' => "./program/blocked.gif",
       'charset' => RCMAIL_CHARSET,
       'cid_map' => $part->replaces,
-      ), $full_inline);
-
-    $REMOTE_OBJECTS = !$full_inline;
+      'html_elements' => array('body'),
+    );
+    
+    if (!$p['inline_html']) {
+      $wash_opts['html_elements'] = array('html','head','title','body');
+    }
+    
+    /* CSS styles need to be sanitized!
+    if ($p['safe']) {
+      $wash_opts['html_elements'][] = 'style';
+      $wash_opts['html_attribs'] = array('type');
+    }
+    */
+    
+    $washer = new washtml($wash_opts);
+    $washer->add_callback('form', 'rcmail_washtml_callback');
+    $body = $washer->wash($html);
+    $REMOTE_OBJECTS = $washer->extlinks;
 
     return $body;
   }
@@ -637,21 +654,36 @@ function rcmail_print_body($part, $safe=false, $plain=false)
   $body = preg_replace("/##string_replacement\{([0-9]+)\}##/e", "\$replace_strings[\\1]", join("\n", $a_lines));
   
   return "<div class=\"pre\">".$body."\n</div>";
-  }
-
-
+}
 
 /**
  * add a string to the replacement array and return a replacement string
  */
 function rcmail_str_replacement($str, &$rep)
-  {
+{
   static $count = 0;
   $rep[$count] = stripslashes($str);
   return "##string_replacement{".($count++)."}##";
-  }
+}
 
 
+/**
+ * Callback function for washtml cleaning class
+ */
+function rcmail_washtml_callback($tagname, $attrib, $content)
+{
+  switch ($tagname) {
+    case 'form':
+      $out = html::div('form', $content);
+      break;
+      
+    default:
+      $out = '';
+  }
+  
+  return $out;
+}
+
 
 /**
  * return table with message headers
@@ -756,7 +788,7 @@ function rcmail_message_body($attrib)
         if (!isset($part->body))
           $part->body = $MESSAGE->get_part_content($part->mime_id);
 
-        $body = rcmail_print_body($part, $safe_mode, !$CONFIG['prefer_html']);
+        $body = rcmail_print_body($part, array('safe' => $safe_mode, 'plain' => !$CONFIG['prefer_html']));
 
         if ($part->ctype_secondary == 'html')
           $out .= html::div('message-htmlpart', rcmail_html4inline($body, $attrib['id']));
diff --git a/program/steps/mail/get.inc b/program/steps/mail/get.inc
index 4d7895269..842c60536 100644
--- a/program/steps/mail/get.inc
+++ b/program/steps/mail/get.inc
@@ -65,6 +65,8 @@ else if ($pid = get_input_value('_part', RCUBE_INPUT_GET)) {
       header("Cache-Control: private", false);
       header("Content-Type: application/octet-stream");
     }
+    else if ($ctype_primary == 'text')
+      header("Content-Type: text/$ctype_secondary; charset=" . RCMAIL_CHARSET);
     else
       header("Content-Type: $mimetype");
 
@@ -95,7 +97,7 @@ else if ($pid = get_input_value('_part', RCUBE_INPUT_GET)) {
         $part->body = $MESSAGE->get_part_content($part->mime_id);
 
       $OUTPUT = new rcube_html_page();
-      $OUTPUT->write(rcmail_print_body($part, $MESSAGE->is_safe));
+      $OUTPUT->write(rcmail_print_body($part, array('safe' => $MESSAGE->is_safe, 'inline_html' => false)));
     }
     else {
       header(sprintf('Content-Disposition: %s; filename="%s";',