Issue 491 - Validate custom filters

lib/filterValidation.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2014 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 let {Filter, InvalidFilter, ElemHideBase} = require("filterClasses");
 
-function parseFilter(text)
+function parseFilter(text, ignore_headers)
 {
   text = Filter.normalize(text);
   if (!text)
     return null;
+
+  if (text[0] == "[")
+  {
+    if (ignore_headers)
+      return null;
+
+    throw ext.i18n.getMessage("unexpected_filter_list_header");
+  }
 
   let filter = Filter.fromText(text);
 
   if (filter instanceof InvalidFilter)
     throw filter.reason;
 
   if (filter instanceof ElemHideBase)
   {
     let style = document.createElement("style");
     document.documentElement.appendChild(style);
     let sheet = style.sheet;
     document.documentElement.removeChild(style);
 
     try
     {
       document.querySelector(filter.selector);
       sheet.insertRule(filter.selector + "{}", 0);
     }
     catch (error)
     {
       throw ext.i18n.getMessage("invalid_css_selector", "'" + filter.selector + "'");
     }
   }
 
   return filter;
 }
 exports.parseFilter = parseFilter;
 
-function parseFilters(text)
+function parseFilters(text, ignore_headers)
 {
   let lines = text.split("\n");
   let filters = [];
 
   for (let i = 0; i < lines.length; i++)
   {
     let filter;
     try
     {
-      filter = parseFilter(lines[i]);
+      filter = parseFilter(lines[i], ignore_headers);
     }
     catch (error)
     {
       throw ext.i18n.getMessage("line", (i + 1).toString()) + ": " + error;
     }
 
     if (filter)
       filters.push(filter);
   }
 
   return filters;
 }
 exports.parseFilters = parseFilters;