<?php defined('SYSPATH') OR die('No direct access allowed.');
/**
 * Security helper class.
 *
 * @package    Security
 * @author     Kohana Team
 * @copyright  (c) 2007-2009 Kohana Team
 * @license    http://kohanaphp.com/license.html
 */
class Kohana_Security {

	/**
	 * Remove XSS from user input.
	 *
	 * @author     Christian Stocker <chregu@bitflux.ch>
	 * @copyright  (c) 2001-2006 Bitflux GmbH
	 *
	 * @param   string  string to sanitize
	 * @return  string
	 */
	public static function xss_clean($str)
	{
		// http://svn.bitflux.ch/repos/public/popoon/trunk/classes/externalinput.php
		// +----------------------------------------------------------------------+
		// | Copyright (c) 2001-2006 Bitflux GmbH                                 |
		// +----------------------------------------------------------------------+
		// | Licensed under the Apache License, Version 2.0 (the "License");      |
		// | you may not use this file except in compliance with the License.     |
		// | You may obtain a copy of the License at                              |
		// | http://www.apache.org/licenses/LICENSE-2.0                           |
		// | Unless required by applicable law or agreed to in writing, software  |
		// | distributed under the License is distributed on an "AS IS" BASIS,    |
		// | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or      |
		// | implied. See the License for the specific language governing         |
		// | permissions and limitations under the License.                       |
		// +----------------------------------------------------------------------+
		// | Author: Christian Stocker <chregu@bitflux.ch>                        |
		// +----------------------------------------------------------------------+
		//
		// Kohana Modifications:
		// * Changed double quotes to single quotes, changed indenting and spacing
		// * Removed magic_quotes stuff
		// * Increased regex readability:
		//   * Used delimeters that aren't found in the pattern
		//   * Removed all unneeded escapes
		//   * Deleted U modifiers and swapped greediness where needed
		// * Increased regex speed:
		//   * Made capturing parentheses non-capturing where possible
		//   * Removed parentheses where possible
		//   * Split up alternation alternatives
		//   * Made some quantifiers possessive

		// Fix &entity\n;
		$str = str_replace(array('&amp;','&lt;','&gt;'), array('&amp;amp;','&amp;lt;','&amp;gt;'), $str);
		$str = preg_replace('/(&#*\w+)[\x00-\x20]+;/u', '$1;', $str);
		$str = preg_replace('/(&#x*[0-9A-F]+);*/iu', '$1;', $str);
		$str = html_entity_decode($str, ENT_COMPAT, Kohana::$charset);

		// Remove any attribute starting with "on" or xmlns
		$str = preg_replace('#(<[^>]+?[\x00-\x20"\'])(?:on|xmlns)[^>]*+>#iu', '$1>', $str);

		// Remove javascript: and vbscript: protocols
		$str = preg_replace('#([a-z]*)[\x00-\x20]*=[\x00-\x20]*([`\'"]*)[\x00-\x20]*j[\x00-\x20]*a[\x00-\x20]*v[\x00-\x20]*a[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#iu', '$1=$2nojavascript...', $str);
		$str = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*v[\x00-\x20]*b[\x00-\x20]*s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:#iu', '$1=$2novbscript...', $str);
		$str = preg_replace('#([a-z]*)[\x00-\x20]*=([\'"]*)[\x00-\x20]*-moz-binding[\x00-\x20]*:#u', '$1=$2nomozbinding...', $str);

		// Only works in IE: <span style="width: expression(alert('Ping!'));"></span>
		$str = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?expression[\x00-\x20]*\([^>]*+>#i', '$1>', $str);
		$str = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?behaviour[\x00-\x20]*\([^>]*+>#i', '$1>', $str);
		$str = preg_replace('#(<[^>]+?)style[\x00-\x20]*=[\x00-\x20]*[`\'"]*.*?s[\x00-\x20]*c[\x00-\x20]*r[\x00-\x20]*i[\x00-\x20]*p[\x00-\x20]*t[\x00-\x20]*:*[^>]*+>#iu', '$1>', $str);

		// Remove namespaced elements (we do not need them)
		$str = preg_replace('#</*\w+:\w[^>]*+>#i', '', $str);

		do
		{
			// Remove really unwanted tags
			$old = $str;
			$str = preg_replace('#</*(?:applet|b(?:ase|gsound|link)|embed|frame(?:set)?|i(?:frame|layer)|l(?:ayer|ink)|meta|object|s(?:cript|tyle)|title|xml)[^>]*+>#i', '', $str);
		}
		while ($old !== $str);

		return $str;
	}

	/**
	 * Remove image tags from a string.
	 *
	 * @param   string  string to sanitize
	 * @return  string
	 */
	public static function strip_image_tags($str)
	{
		return preg_replace('#<img\s.*?(?:src\s*=\s*["\']?([^"\'<>\s]*)["\']?[^>]*)?>#is', '$1', $str);
	}

	/**
	 * Remove PHP tags from a string.
	 *
	 * @param   string  string to sanitize
	 * @return  string
	 */
	public static function encode_php_tags($str)
	{
		return str_replace(array('<?', '?>'), array('&lt;?', '?&gt;'), $str);
	}

} // End security
