added Security library

1 files changed, 710 insertions, 0 deletions

diff --git a/system/libraries/Security.php b/system/libraries/Security.php
new file mode 100644
index 000000000..93da59204
--- /dev/null
+++ b/system/libraries/Security.php
@@ -0,0 +1,710 @@
+<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 4.3.2 or newer
+ *
+ * @package		CodeIgniter
+ * @author		ExpressionEngine Dev Team
+ * @copyright	Copyright (c) 2008 - 2010, 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/sessions.html
+ */
+class CI_Security {
+	var $xss_hash 			= '';
+	var $csrf_hash 			= '';
+	var $csrf_expire		= 7200;  // Two hours (in seconds)
+	var $csrf_token_name	= 'ci_csrf_token';
+
+	/* never allowed, string replacement */
+	var $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['
+									);
+	/* never allowed, regex replacement */
+	var $never_allowed_regex = array(
+										"javascript\s*:"			=> '[removed]',
+										"expression\s*(\(|&\#40;)"	=> '[removed]', // CSS and IE
+										"vbscript\s*:"				=> '[removed]', // IE, surprise!
+										"Redirect\s+302"			=> '[removed]'
+									);
+
+	function CI_Security()
+	{
+		// Set the CSRF hash
+		$this->_csrf_set_hash();
+		
+		log_message('debug', "Security Class Initialized");
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Verify Cross Site Request Forgery Protection
+	 *
+	 * @access	public
+	 * @return	null
+	 */
+	function csrf_verify()
+	{	
+		// If no POST data exists we will set the CSRF cookie
+		if (count($_POST) == 0)
+		{
+			return $this->csrf_set_cookie();
+		}
+
+		// Do the tokens exist in both the _POST and _COOKIE arrays?
+		if ( ! isset($_POST[$this->csrf_token_name]) OR ! isset($_COOKIE[$this->csrf_token_name]))
+		{
+			$this->csrf_show_error();
+		}
+
+		// Do the tokens match?
+		if ($_POST[$this->csrf_token_name] != $_COOKIE[$this->csrf_token_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]);
+
+		log_message('debug', "CSRF token verified ");
+	}
+	
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Set Cross Site Request Forgery Protection Cookie
+	 *
+	 * @access	public
+	 * @return	null
+	 */
+	function csrf_set_cookie()
+	{
+		$prefix = ( ! is_string(config_item('cookie_prefix'))) ? '' : config_item('cookie_prefix');
+		
+		$expire = time() + $this->csrf_expire;
+
+		setcookie($prefix.$this->csrf_token_name, $this->csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), 0);
+		
+		log_message('debug', "CRSF cookie Set");		
+	}
+	
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Set Cross Site Request Forgery Protection Cookie
+	 *
+	 * @access	public
+	 * @return	null
+	 */
+	function _csrf_set_hash()
+	{
+		if ($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_token_name]) AND $_COOKIE[$this->csrf_token_name] != '')
+			{
+				$this->csrf_hash = $_COOKIE[$this->csrf_token_name];
+			}
+			else
+			{
+				$this->csrf_hash = md5(uniqid(rand(), TRUE));
+			}
+		}
+		
+		return $this->csrf_hash;
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Show CSRF Error
+	 *
+	 * @access	public
+	 * @return	null
+	 */
+	function csrf_show_error()
+	{
+		show_error('The action you have requested is not allowed.');
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * XSS Clean
+	 *
+	 * Sanitizes data so that Cross Site Scripting Hacks can be
+	 * prevented.  This function does a fair amount of work but
+	 * it is extremely thorough, designed to prevent even the
+	 * most obscure XSS attempts.  Nothing is ever 100% foolproof,
+	 * of course, but I haven't been able to get anything passed
+	 * the filter.
+	 *
+	 * Note: This function should only be used to deal with data
+	 * upon submission.  It's not something that should
+	 * be used for general runtime processing.
+	 *
+	 * This function was based in part on some code and ideas I
+	 * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention
+	 *
+	 * To help develop this script I used this great list of
+	 * vulnerabilities along with a few other hacks I've
+	 * harvested from examining vulnerabilities in other programs:
+	 * http://ha.ckers.org/xss.html
+	 *
+	 * @access	public
+	 * @param	mixed	string or array
+	 * @return	string
+	 */
+	function xss_clean($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 = $this->_remove_invisible_characters($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);
+
+		/*
+		 * 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 = $this->_remove_invisible_characters($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 = $str;
+		
+		/*
+		 * Not Allowed Under Any Conditions
+		 */
+		
+		foreach ($this->never_allowed_str as $key => $val)
+		{
+			$str = str_replace($key, $val, $str);   
+		}
+	
+		foreach ($this->never_allowed_regex as $key => $val)
+		{
+			$str = preg_replace("#".$key."#i", $val, $str);   
+		}
+
+		/*
+		 * Makes PHP tags safe
+		 *
+		 *  Note: XML tags are inadvertently replaced too:
+		 *
+		 *	<?xml
+		 *
+		 * But it doesn't seem to pose a problem.
+		 *
+		 */
+		if ($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.
+		 *
+		 */
+		$words = array('javascript', 'expression', 'vbscript', 'script', 'applet', 'alert', 'document', 'write', 'cookie', 'window');
+		foreach ($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 JavaScript Event Handlers
+		 *
+		 * Note: This code is a little blunt.  It removes
+		 * the event handler and anything up to the closing >,
+		 * but it's unlikely to be a problem.
+		 *
+		 */
+		$event_handlers = array('[^a-z_\-]on\w*','xmlns');
+
+		if ($is_image === TRUE)
+		{
+			/*
+			 * Adobe Photoshop puts XML metadata into JFIF images, including namespacing, 
+			 * so we have to allow this for images. -Paul
+			 */
+			unset($event_handlers[array_search('xmlns', $event_handlers)]);
+		}
+
+		$str = preg_replace("#<([^><]+?)(".implode('|', $event_handlers).")(\s*=\s*[^><]*)([><]*)#i", "<\\1\\4", $str);
+		
+		/*
+		 * 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;", $str);
+					
+		/*
+		 * Final clean up
+		 *
+		 * This adds a bit of extra precaution in case
+		 * something got through the above filters
+		 *
+		 */
+		foreach ($this->never_allowed_str as $key => $val)
+		{
+			$str = str_replace($key, $val, $str);   
+		}
+	
+		foreach ($this->never_allowed_regex as $key => $val)
+		{
+			$str = preg_replace("#".$key."#i", $val, $str);
+		}
+
+		/*
+		 *  Images are Handled in a Special Way
+		 *  - Essentially, we want to know that after all of the character conversion is done whether
+		 *  any unwanted, likely XSS, code was found.  If not, we return TRUE, as the image is clean.
+		 *  However, if the string post-conversion does not matched the string post-removal of XSS,
+		 *  then it fails, as there was unwanted XSS code found and removed/changed during processing.
+		 */
+
+		if ($is_image === TRUE)
+		{
+			if ($str == $converted_string)
+			{
+				return TRUE;
+			}
+			else
+			{
+				return FALSE;
+			}
+		}
+		
+		log_message('debug', "XSS Filtering completed");
+		return $str;
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Random Hash for protecting URLs
+	 *
+	 * @access	public
+	 * @return	string
+	 */
+	function xss_hash()
+	{	
+		if ($this->xss_hash == '')
+		{
+			if (phpversion() >= 4.2)
+				mt_srand();
+			else
+				mt_srand(hexdec(substr(md5(microtime()), -8)) & 0x7fffffff);
+			
+			$this->xss_hash = md5(time() + mt_rand(0, 1999999999));
+		}
+		
+		return $this->xss_hash;
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Remove Invisible Characters
+	 *
+	 * This prevents sandwiching null characters
+	 * between ascii characters, like Java\0script.
+	 *
+	 * @access	public
+	 * @param	string
+	 * @return	string
+	 */
+	function _remove_invisible_characters($str)
+	{
+		static $non_displayables;
+		
+		if ( ! isset($non_displayables))
+		{
+			// every control character except newline (dec 10), carriage return (dec 13), and horizontal tab (dec 09),
+			$non_displayables = array(
+										'/%0[0-8bcef]/',			// url encoded 00-08, 11, 12, 14, 15
+										'/%1[0-9a-f]/',				// url encoded 16-31
+										'/[\x00-\x08]/',			// 00-08
+										'/\x0b/', '/\x0c/',			// 11, 12
+										'/[\x0e-\x1f]/'				// 14-31
+									);
+		}
+
+		do
+		{
+			$cleaned = $str;
+			$str = preg_replace($non_displayables, '', $str);
+		}
+		while ($cleaned != $str);
+
+		return $str;
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Compact Exploded Words
+	 *
+	 * Callback function for xss_clean() to remove whitespace from
+	 * things like j a v a s c r i p t
+	 *
+	 * @access	public
+	 * @param	type
+	 * @return	type
+	 */
+	function _compact_exploded_words($matches)
+	{
+		return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
+	}
+	
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Sanitize Naughty HTML
+	 *
+	 * Callback function for xss_clean() to remove naughty HTML elements
+	 *
+	 * @access	private
+	 * @param	array
+	 * @return	string
+	 */
+	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 $str;
+	}
+	
+	// --------------------------------------------------------------------
+	
+	/**
+	 * JS Link Removal
+	 *
+	 * Callback function for xss_clean() to sanitize links
+	 * This limits the PCRE backtracks, making it more performance friendly
+	 * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
+	 * PHP 5.2+ on link-heavy strings
+	 *
+	 * @access	private
+	 * @param	array
+	 * @return	string
+	 */
+	function _js_link_removal($match)
+	{
+		$attributes = $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]));
+		return str_replace($match[1], preg_replace("#href=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si", "", $attributes), $match[0]);
+	}
+	
+	/**
+	 * JS Image Removal
+	 *
+	 * Callback function for xss_clean() to sanitize image tags
+	 * This limits the PCRE backtracks, making it more performance friendly
+	 * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
+	 * PHP 5.2+ on image tag heavy strings
+	 *
+	 * @access	private
+	 * @param	array
+	 * @return	string
+	 */
+	function _js_img_removal($match)
+	{
+		$attributes = $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]));
+		return str_replace($match[1], preg_replace("#src=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si", "", $attributes), $match[0]);
+	}
+
+	// --------------------------------------------------------------------
+	
+	/**
+	 * Attribute Conversion
+	 *
+	 * Used as a callback for XSS Clean
+	 *
+	 * @access	public
+	 * @param	array
+	 * @return	string
+	 */
+	function _convert_attribute($match)
+	{
+		return str_replace(array('>', '<', '\\'), array('&gt;', '&lt;', '\\\\'), $match[0]);
+	}
+	
+	// --------------------------------------------------------------------
+
+	/**
+	 * Filter Attributes
+	 *
+	 * Filters tag attributes for consistency and safety
+	 *
+	 * @access	public
+	 * @param	string
+	 * @return	string
+	 */
+	function _filter_attributes($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 $out;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * HTML Entity Decode Callback
+	 *
+	 * Used as a callback for XSS Clean
+	 *
+	 * @access	public
+	 * @param	array
+	 * @return	string
+	 */
+	function _decode_entity($match)
+	{
+		$CI =& get_instance();
+		$CI->load->helper('typography');
+		return entity_decode($match[0], strtoupper($CI->config->item('charset')));
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Filename Security
+	 *
+	 * @access	public
+	 * @param	string
+	 * @return	string
+	 */
+	function sanitize_filename($str)
+	{
+		$bad = array(
+						"../",
+						"./",
+						"<!--",
+						"-->",
+						"<",
+						">",
+						"'",
+						'"',
+						'&',
+						'$',
+						'#',
+						'{',
+						'}',
+						'[',
+						']',
+						'=',
+						';',
+						'?',
+						'/',
+						"%20",
+						"%22",
+						"%3c",		// <
+						"%253c", 	// <
+						"%3e", 		// >
+						"%0e", 		// >
+						"%28", 		// (
+						"%29", 		// )
+						"%2528", 	// (
+						"%26", 		// &
+						"%24", 		// $
+						"%3f", 		// ?
+						"%3b", 		// ;
+						"%3d"		// =
+					);
+
+		return stripslashes(str_replace($bad, '', $str));
+	}
+
+}
+// END Security Class
+
+/* End of file Security.php */
+/* Location: ./system/libraries/Security.php */
\ No newline at end of file