<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/**

 * CodeIgniter

 *

 * An open source application development framework for PHP 5.1.6 or newer

 *

 * @package		CodeIgniter

 * @author		ExpressionEngine Dev Team

 * @copyright	Copyright (c) 2008 - 2011, EllisLab, Inc.

 * @license		http://codeigniter.com/user_guide/license.html

 * @link		http://codeigniter.com

 * @since		Version 1.0

 * @filesource

 */



// ------------------------------------------------------------------------



/**

 * Security Class

 *

 * @package		CodeIgniter

 * @subpackage	Libraries

 * @category	Security

 * @author		ExpressionEngine Dev Team

 * @link		http://codeigniter.com/user_guide/libraries/security.html

 */

class CI_Security {



	/**

	 * Random Hash for protecting URLs

	 *

	 * @var string

	 * @access protected

	 */

	protected $_xss_hash			= '';

	/**

	 * Random Hash for Cross Site Request Forgery Protection Cookie

	 *

	 * @var string

	 * @access protected

	 */

	protected $_csrf_hash			= '';

	/**

	 * Expiration time for Cross Site Request Forgery Protection Cookie

	 * Defaults to two hours (in seconds)

	 *

	 * @var int

	 * @access protected

	 */

	protected $_csrf_expire			= 7200;

	/**

	 * Token name for Cross Site Request Forgery Protection Cookie

	 *

	 * @var string

	 * @access protected

	 */

	protected $_csrf_token_name		= 'ci_csrf_token';

	/**

	 * Cookie name for Cross Site Request Forgery Protection Cookie

	 *

	 * @var string

	 * @access protected

	 */

	protected $_csrf_cookie_name	= 'ci_csrf_token';

	/**

	 * List of never allowed strings

	 *

	 * @var array

	 * @access protected

	 */

	protected $_never_allowed_str = array(

		'document.cookie'	=> '[removed]',

		'document.write'	=> '[removed]',

		'.parentNode'		=> '[removed]',

		'.innerHTML'		=> '[removed]',

		'window.location'	=> '[removed]',

		'-moz-binding'		=> '[removed]',

		'<!--'				=> '&lt;!--',

		'-->'				=> '--&gt;',

		'<![CDATA['			=> '&lt;![CDATA[',

		'<comment>'			=> '&lt;comment&gt;'

	);



	/* never allowed, regex replacement */

	/**

	 * List of never allowed regex replacement

	 *

	 * @var array

	 * @access protected

	 */

	protected $_never_allowed_regex = array(

		'javascript\s*:',

		'expression\s*(\(|&\#40;)', // CSS and IE

		'vbscript\s*:', // IE, surprise!

		'Redirect\s+302',

		"([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"

	);



	/**

	 * Constructor

	 *

	 * @return	void

	 */

	public function __construct()

	{

		// Is CSRF protection enabled?

		if (config_item('csrf_protection') === TRUE)

		{

			// CSRF config

			foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key)

			{

				if (FALSE !== ($val = config_item($key)))

				{

					$this->{'_'.$key} = $val;

				}

			}



			// Append application specific cookie prefix

			if (config_item('cookie_prefix'))

			{

				$this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name;

			}



			// Set the CSRF hash

			$this->_csrf_set_hash();

		}



		log_message('debug', "Security Class Initialized");

	}



	// --------------------------------------------------------------------



	/**

	 * Verify Cross Site Request Forgery Protection

	 *

	 * @return	object

	 */

	public function csrf_verify()

	{

		// If it's not a POST request we will set the CSRF cookie

		if (strtoupper($_SERVER['REQUEST_METHOD']) !== 'POST')

		{

			return $this->csrf_set_cookie();

		}



		// Do the tokens exist in both the _POST and _COOKIE arrays?

		if ( ! isset($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name]))

		{

			$this->csrf_show_error();

		}



		// Do the tokens match?

		if ($_POST[$this->_csrf_token_name] != $_COOKIE[$this->_csrf_cookie_name])

		{

			$this->csrf_show_error();

		}



		// We kill this since we're done and we don't want to

		// polute the _POST array

		unset($_POST[$this->_csrf_token_name]);



		// Nothing should last forever

		unset($_COOKIE[$this->_csrf_cookie_name]);

		$this->_csrf_set_hash();

		$this->csrf_set_cookie();



		log_message('debug', 'CSRF token verified');



		return $this;

	}



	// --------------------------------------------------------------------



	/**

	 * Set Cross Site Request Forgery Protection Cookie

	 *

	 * @return	object

	 */

	public function csrf_set_cookie()

	{

		$expire = time() + $this->_csrf_expire;

		$secure_cookie = (config_item('cookie_secure') === TRUE) ? 1 : 0;



		if ($secure_cookie && (empty($_SERVER['HTTPS']) OR strtolower($_SERVER['HTTPS']) === 'off'))

		{

			return FALSE;

		}



		setcookie($this->_csrf_cookie_name, $this->_csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), $secure_cookie);



		log_message('debug', "CRSF cookie Set");



		return $this;

	}



	// --------------------------------------------------------------------



	/**

	 * Show CSRF Error

	 *

	 * @return	void

	 */

	public function csrf_show_error()

	{

		show_error('The action you have requested is not allowed.');

	}



	// --------------------------------------------------------------------



	/**

	 * Get CSRF Hash

	 *

	 * Getter Method

	 *

	 * @return 	string 	self::_csrf_hash

	 */

	public function get_csrf_hash()

	{

		return $this->_csrf_hash;

	}



	// --------------------------------------------------------------------



	/**

	 * Get CSRF Token Name

	 *

	 * Getter Method

	 *

	 * @return 	string 	self::csrf_token_name

	 */

	public function get_csrf_token_name()

	{

		return $this->_csrf_token_name;

	}



	// --------------------------------------------------------------------



	/**

	 * XSS Clean

	 *

	 * Sanitizes data so that Cross Site Scripting Hacks can be

	 * prevented.  This function does a fair amount of work but

	 * it is extremely thorough, designed to prevent even the

	 * most obscure XSS attempts.  Nothing is ever 100% foolproof,

	 * of course, but I haven't been able to get anything passed

	 * the filter.

	 *

	 * Note: This function should only be used to deal with data

	 * upon submission.  It's not something that should

	 * be used for general runtime processing.

	 *

	 * This function was based in part on some code and ideas I

	 * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention

	 *

	 * To help develop this script I used this great list of

	 * vulnerabilities along with a few other hacks I've

	 * harvested from examining vulnerabilities in other programs:

	 * http://ha.ckers.org/xss.html

	 *

	 * @param	mixed	string or array

	 * @param 	bool

	 * @return	string

	 */

	public function xss_clean($str, $is_image = FALSE)

	{

		/*

		 * Is the string an array?

		 *

		 */

		if (is_array($str))

		{

			while (list($key) = each($str))

			{

				$str[$key] = $this->xss_clean($str[$key]);

			}



			return $str;

		}



		/*

		 * Remove Invisible Characters

		 */

		$str = remove_invisible_characters($str);



		// Validate Entities in URLs

		$str = $this->_validate_entities($str);



		/*

		 * URL Decode

		 *

		 * Just in case stuff like this is submitted:

		 *

		 * <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>

		 *

		 * Note: Use rawurldecode() so it does not remove plus signs

		 *

		 */

		$str = rawurldecode($str);



		/*

		 * Convert character entities to ASCII

		 *

		 * This permits our tests below to work reliably.

		 * We only convert entities that are within tags since

		 * these are the ones that will pose security problems.

		 *

		 */



		$str = preg_replace_callback("/[a-z]+=([\'\"]).*?\\1/si", array($this, '_convert_attribute'), $str);



		$str = preg_replace_callback("/<\w+.*?(?=>|<|$)/si", array($this, '_decode_entity'), $str);



		/*

		 * Remove Invisible Characters Again!

		 */

		$str = remove_invisible_characters($str);



		/*

		 * Convert all tabs to spaces

		 *

		 * This prevents strings like this: ja	vascript

		 * NOTE: we deal with spaces between characters later.

		 * NOTE: preg_replace was found to be amazingly slow here on

		 * large blocks of data, so we use str_replace.

		 */



		if (strpos($str, "\t") !== FALSE)

		{

			$str = str_replace("\t", ' ', $str);

		}



		/*

		 * Capture converted string for later comparison

		 */

		$converted_string = $str;



		// Remove Strings that are never allowed

		$str = $this->_do_never_allowed($str);



		/*

		 * Makes PHP tags safe

		 *

		 * Note: XML tags are inadvertently replaced too:

		 *

		 * <?xml

		 *

		 * But it doesn't seem to pose a problem.

		 */

		if ($is_image === TRUE)

		{

			// Images have a tendency to have the PHP short opening and

			// closing tags every so often so we skip those and only

			// do the long opening tags.

			$str = preg_replace('/<\?(php)/i', "&lt;?\\1", $str);

		}

		else

		{

			$str = str_replace(array('<?', '?'.'>'),  array('&lt;?', '?&gt;'), $str);

		}



		/*

		 * Compact any exploded words

		 *

		 * This corrects words like:  j a v a s c r i p t

		 * These words are compacted back to their correct state.

		 */

		$words = array(

			'javascript', 'expression', 'vbscript', 'script', 'base64',

			'applet', 'alert', 'document', 'write', 'cookie', 'window'

		);



		foreach ($words as $word)

		{

			$temp = '';



			for ($i = 0, $wordlen = strlen($word); $i < $wordlen; $i++)

			{

				$temp .= substr($word, $i, 1)."\s*";

			}



			// We only want to do this when it is followed by a non-word character

			// That way valid stuff like "dealer to" does not become "dealerto"

			$str = preg_replace_callback('#('.substr($temp, 0, -3).')(\W)#is', array($this, '_compact_exploded_words'), $str);

		}



		/*

		 * Remove disallowed Javascript in links or img tags

		 * We used to do some version comparisons and use of stripos for PHP5,

		 * but it is dog slow compared to these simplified non-capturing

		 * preg_match(), especially if the pattern exists in the string

		 */

		do

		{

			$original = $str;



			if (preg_match("/<a/i", $str))

			{

				$str = preg_replace_callback("#<a\s+([^>]*?)(>|$)#si", array($this, '_js_link_removal'), $str);

			}



			if (preg_match("/<img/i", $str))

			{

				$str = preg_replace_callback("#<img\s+([^>]*?)(\s?/?>|$)#si", array($this, '_js_img_removal'), $str);

			}



			if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str))

			{

				$str = preg_replace("#<(/*)(script|xss)(.*?)\>#si", '[removed]', $str);

			}

		}

		while($original != $str);



		unset($original);



		// Remove evil attributes such as style, onclick and xmlns

		$str = $this->_remove_evil_attributes($str, $is_image);



		/*

		 * Sanitize naughty HTML elements

		 *

		 * If a tag containing any of the words in the list

		 * below is found, the tag gets converted to entities.

		 *

		 * So this: <blink>

		 * Becomes: &lt;blink&gt;

		 */

		$naughty = 'alert|applet|audio|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|isindex|layer|link|meta|object|plaintext|style|script|textarea|title|video|xml|xss';

		$str = preg_replace_callback('#<(/*\s*)('.$naughty.')([^><]*)([><]*)#is', array($this, '_sanitize_naughty_html'), $str);



		/*

		 * Sanitize naughty scripting elements

		 *

		 * Similar to above, only instead of looking for

		 * tags it looks for PHP and JavaScript commands

		 * that are disallowed.  Rather than removing the

		 * code, it simply converts the parenthesis to entities

		 * rendering the code un-executable.

		 *

		 * For example:	eval('some code')

		 * Becomes:		eval&#40;'some code'&#41;

		 */

		$str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2&#40;\\3&#41;", $str);





		// Final clean up

		// This adds a bit of extra precaution in case

		// something got through the above filters

		$str = $this->_do_never_allowed($str);



		/*

		 * Images are Handled in a Special Way

		 * - Essentially, we want to know that after all of the character

		 * conversion is done whether any unwanted, likely XSS, code was found.

		 * If not, we return TRUE, as the image is clean.

		 * However, if the string post-conversion does not matched the

		 * string post-removal of XSS, then it fails, as there was unwanted XSS

		 * code found and removed/changed during processing.

		 */



		if ($is_image === TRUE)

		{

			return ($str == $converted_string) ? TRUE: FALSE;

		}



		log_message('debug', "XSS Filtering completed");

		return $str;

	}



	// --------------------------------------------------------------------



	/**

	 * Random Hash for protecting URLs

	 *

	 * @return	string

	 */

	public function xss_hash()

	{

		if ($this->_xss_hash == '')

		{

			mt_srand();

			$this->_xss_hash = md5(time() + mt_rand(0, 1999999999));

		}



		return $this->_xss_hash;

	}



	// --------------------------------------------------------------------



	/**

	 * HTML Entities Decode

	 *

	 * This function is a replacement for html_entity_decode()

	 *

	 * The reason we are not using html_entity_decode() by itself is because

	 * while it is not technically correct to leave out the semicolon

	 * at the end of an entity most browsers will still interpret the entity

	 * correctly.  html_entity_decode() does not convert entities without

	 * semicolons, so we are left with our own little solution here. Bummer.

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	public function entity_decode($str, $charset='UTF-8')

	{

		if (stristr($str, '&') === FALSE)

		{

			return $str;

		}



		$str = html_entity_decode($str, ENT_COMPAT, $charset);

		$str = preg_replace('~&#x(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);

		return preg_replace('~&#([0-9]{2,4})~e', 'chr(\\1)', $str);

	}



	// --------------------------------------------------------------------



	/**

	 * Filename Security

	 *

	 * @param	string

	 * @param 	bool

	 * @return	string

	 */

	public function sanitize_filename($str, $relative_path = FALSE)

	{

		$bad = array(

			"../",

			"<!--",

			"-->",

			"<",

			">",

			"'",

			'"',

			'&',

			'$',

			'#',

			'{',

			'}',

			'[',

			']',

			'=',

			';',

			'?',

			"%20",

			"%22",

			"%3c",		// <

			"%253c",	// <

			"%3e",		// >

			"%0e",		// >

			"%28",		// (

			"%29",		// )

			"%2528",	// (

			"%26",		// &

			"%24",		// $

			"%3f",		// ?

			"%3b",		// ;

			"%3d"		// =

		);



		if ( ! $relative_path)

		{

			$bad[] = './';

			$bad[] = '/';

		}



		$str = remove_invisible_characters($str, FALSE);

		return stripslashes(str_replace($bad, '', $str));

	}



	// ----------------------------------------------------------------



	/**

	 * Compact Exploded Words

	 *

	 * Callback function for xss_clean() to remove whitespace from

	 * things like j a v a s c r i p t

	 *

	 * @param	type

	 * @return	type

	 */

	protected function _compact_exploded_words($matches)

	{

		return preg_replace('/\s+/s', '', $matches[1]).$matches[2];

	}



	// --------------------------------------------------------------------



	/*

	 * Remove Evil HTML Attributes (like evenhandlers and style)

	 *

	 * It removes the evil attribute and either:

	 * 	- Everything up until a space

	 *		For example, everything between the pipes:

	 *		<a |style=document.write('hello');alert('world');| class=link>

	 * 	- Everything inside the quotes

	 *		For example, everything between the pipes:

	 *		<a |style="document.write('hello'); alert('world');"| class="link">

	 *

	 * @param string $str The string to check

	 * @param boolean $is_image TRUE if this is an image

	 * @return string The string with the evil attributes removed

	 */

	protected function _remove_evil_attributes($str, $is_image)

	{

		// All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns

		$evil_attributes = array('on\w*', 'style', 'xmlns', 'formaction');



		if ($is_image === TRUE)

		{

			/*

			 * Adobe Photoshop puts XML metadata into JFIF images, 

			 * including namespacing, so we have to allow this for images.

			 */

			unset($evil_attributes[array_search('xmlns', $evil_attributes)]);

		}



		do {

			$count = 0;

			$attribs = array();



			// find occurrences of illegal attribute strings with quotes (042 and 047 are octal quotes)

			preg_match_all('/('.implode('|', $evil_attributes).')\s*=\s*(\042|\047)([^\\2]*?)(\\2)/is', $str, $matches, PREG_SET_ORDER);



			foreach ($matches as $attr)

			{

				$attribs[] = preg_quote($attr[0], '/');

			}



			// find occurrences of illegal attribute strings without quotes

			preg_match_all('/('.implode('|', $evil_attributes).')\s*=\s*([^\s>]*)/is', $str, $matches, PREG_SET_ORDER);



			foreach ($matches as $attr)

			{

				$attribs[] = preg_quote($attr[0], '/');

			}



			// replace illegal attribute strings that are inside an html tag

			if (count($attribs) > 0)

			{

				$str = preg_replace('/(<?)(\/?[^><]+?)([^A-Za-z<>\-])(.*?)('.implode('|', $attribs).')(.*?)([\s><]?)([><]*)/i', '$1$2 $4$6$7$8', $str, -1, $count);

			}



		} while ($count);



		return $str;

	}



	// --------------------------------------------------------------------



	/**

	 * Sanitize Naughty HTML

	 *

	 * Callback function for xss_clean() to remove naughty HTML elements

	 *

	 * @param	array

	 * @return	string

	 */

	protected function _sanitize_naughty_html($matches)

	{

		// encode opening brace

		$str = '&lt;'.$matches[1].$matches[2].$matches[3];



		// encode captured opening or closing brace to prevent recursive vectors

		$str .= str_replace(array('>', '<'), array('&gt;', '&lt;'),

							$matches[4]);



		return $str;

	}



	// --------------------------------------------------------------------



	/**

	 * JS Link Removal

	 *

	 * Callback function for xss_clean() to sanitize links

	 * This limits the PCRE backtracks, making it more performance friendly

	 * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in

	 * PHP 5.2+ on link-heavy strings

	 *

	 * @param	array

	 * @return	string

	 */

	protected function _js_link_removal($match)

	{

		return str_replace(

			$match[1],

			preg_replace(

				'#href=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|data\s*:)#si',

				'',

				$this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))

			),

			$match[0]

		);

	}



	// --------------------------------------------------------------------



	/**

	 * JS Image Removal

	 *

	 * Callback function for xss_clean() to sanitize image tags

	 * This limits the PCRE backtracks, making it more performance friendly

	 * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in

	 * PHP 5.2+ on image tag heavy strings

	 *

	 * @param	array

	 * @return	string

	 */

	protected function _js_img_removal($match)

	{

		return str_replace(

			$match[1],

			preg_replace(

				'#src=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si',

				'',

				$this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))

			),

			$match[0]

		);

	}



	// --------------------------------------------------------------------



	/**

	 * Attribute Conversion

	 *

	 * Used as a callback for XSS Clean

	 *

	 * @param	array

	 * @return	string

	 */

	protected function _convert_attribute($match)

	{

		return str_replace(array('>', '<', '\\'), array('&gt;', '&lt;', '\\\\'), $match[0]);

	}



	// --------------------------------------------------------------------



	/**

	 * Filter Attributes

	 *

	 * Filters tag attributes for consistency and safety

	 *

	 * @param	string

	 * @return	string

	 */

	protected function _filter_attributes($str)

	{

		$out = '';



		if (preg_match_all('#\s*[a-z\-]+\s*=\s*(\042|\047)([^\\1]*?)\\1#is', $str, $matches))

		{

			foreach ($matches[0] as $match)

			{

				$out .= preg_replace("#/\*.*?\*/#s", '', $match);

			}

		}



		return $out;

	}



	// --------------------------------------------------------------------



	/**

	 * HTML Entity Decode Callback

	 *

	 * Used as a callback for XSS Clean

	 *

	 * @param	array

	 * @return	string

	 */

	protected function _decode_entity($match)

	{

		return $this->entity_decode($match[0], strtoupper(config_item('charset')));

	}



	// --------------------------------------------------------------------



	/**

	 * Validate URL entities

	 *

	 * Called by xss_clean()

	 *

	 * @param 	string

	 * @return 	string

	 */

	protected function _validate_entities($str)

	{

		/*

		 * Protect GET variables in URLs

		 */



		 // 901119URL5918AMP18930PROTECT8198



		$str = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $this->xss_hash()."\\1=\\2", $str);



		/*

		 * Validate standard character entities

		 *

		 * Add a semicolon if missing.  We do this to enable

		 * the conversion of entities to ASCII later.

		 *

		 */

		$str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);



		/*

		 * Validate UTF16 two byte encoding (x00)

		 *

		 * Just as above, adds a semicolon if missing.

		 *

		 */

		$str = preg_replace('#(&\#x?)([0-9A-F]+);?#i',"\\1\\2;",$str);



		/*

		 * Un-Protect GET variables in URLs

		 */

		$str = str_replace($this->xss_hash(), '&', $str);



		return $str;

	}



	// ----------------------------------------------------------------------



	/**

	 * Do Never Allowed

	 *

	 * A utility function for xss_clean()

	 *

	 * @param 	string

	 * @return 	string

	 */

	protected function _do_never_allowed($str)

	{

		$str = str_replace(array_keys($this->_never_allowed_str), $this->_never_allowed_str, $str);



		foreach ($this->_never_allowed_regex as $regex)

		{

			$str = preg_replace('#'.$regex.'#is', '[removed]', $str);

		}



		return $str;

	}



	// --------------------------------------------------------------------



	/**

	 * Set Cross Site Request Forgery Protection Cookie

	 *

	 * @return	string

	 */

	protected function _csrf_set_hash()

	{

		if ($this->_csrf_hash == '')

		{

			// If the cookie exists we will use it's value.

			// We don't necessarily want to regenerate it with

			// each page load since a page could contain embedded

			// sub-pages causing this feature to fail

			if (isset($_COOKIE[$this->_csrf_cookie_name]) &&

				preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1)

			{

				return $this->_csrf_hash = $_COOKIE[$this->_csrf_cookie_name];

			}



			return $this->_csrf_hash = md5(uniqid(rand(), TRUE));

		}



		return $this->_csrf_hash;

	}



}



/* End of file Security.php */

/* Location: ./system/libraries/Security.php */

