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<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
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* An open source application development framework for PHP 5.1.6 or newer
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* @author ExpressionEngine Dev Team
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* @copyright Copyright (c) 2008 - 2011, EllisLab, Inc.
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* @license http://codeigniter.com/user_guide/license.html
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* @link http://codeigniter.com
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// ------------------------------------------------------------------------
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* @package CodeIgniter
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* @subpackage Libraries
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* @author ExpressionEngine Dev Team
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* @link http://codeigniter.com/user_guide/libraries/security.html
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* Random Hash for protecting URLs
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protected $_xss_hash = '';
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* Random Hash for Cross Site Request Forgery Protection Cookie
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protected $_csrf_hash = '';
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* Expiration time for Cross Site Request Forgery Protection Cookie
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* Defaults to two hours (in seconds)
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protected $_csrf_expire = 7200;
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* Token name for Cross Site Request Forgery Protection Cookie
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protected $_csrf_token_name = 'ci_csrf_token';
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* Cookie name for Cross Site Request Forgery Protection Cookie
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protected $_csrf_cookie_name = 'ci_csrf_token';
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* List of never allowed strings
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protected $_never_allowed_str = array(
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'document.cookie' => '[removed]',
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'document.write' => '[removed]',
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'.parentNode' => '[removed]',
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'.innerHTML' => '[removed]',
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'window.location' => '[removed]',
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'-moz-binding' => '[removed]',
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'<![CDATA[' => '<![CDATA[',
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'<comment>' => '<comment>'
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/* never allowed, regex replacement */
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* List of never allowed regex replacement
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protected $_never_allowed_regex = array(
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'expression\s*(\(|&\#40;)', // CSS and IE
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'vbscript\s*:', // IE, surprise!
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"([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"
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public function __construct()
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// Is CSRF protection enabled?
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if (config_item('csrf_protection') === TRUE)
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foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key)
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if (FALSE !== ($val = config_item($key)))
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$this->{'_'.$key} = $val;
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// Append application specific cookie prefix
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if (config_item('cookie_prefix'))
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$this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name;
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$this->_csrf_set_hash();
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log_message('debug', "Security Class Initialized");
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// --------------------------------------------------------------------
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* Verify Cross Site Request Forgery Protection
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public function csrf_verify()
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// If it's not a POST request we will set the CSRF cookie
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if (strtoupper($_SERVER['REQUEST_METHOD']) !== 'POST')
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return $this->csrf_set_cookie();
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// Do the tokens exist in both the _POST and _COOKIE arrays?
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if ( ! isset($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name]))
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$this->csrf_show_error();
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// Do the tokens match?
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if ($_POST[$this->_csrf_token_name] != $_COOKIE[$this->_csrf_cookie_name])
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$this->csrf_show_error();
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// We kill this since we're done and we don't want to
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// polute the _POST array
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unset($_POST[$this->_csrf_token_name]);
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// Nothing should last forever
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unset($_COOKIE[$this->_csrf_cookie_name]);
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$this->_csrf_set_hash();
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$this->csrf_set_cookie();
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log_message('debug', 'CSRF token verified');
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// --------------------------------------------------------------------
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* Set Cross Site Request Forgery Protection Cookie
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public function csrf_set_cookie()
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$expire = time() + $this->_csrf_expire;
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$secure_cookie = (config_item('cookie_secure') === TRUE) ? 1 : 0;
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if ($secure_cookie && (empty($_SERVER['HTTPS']) OR strtolower($_SERVER['HTTPS']) === 'off'))
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setcookie($this->_csrf_cookie_name, $this->_csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), $secure_cookie);
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log_message('debug', "CRSF cookie Set");
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// --------------------------------------------------------------------
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public function csrf_show_error()
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show_error('The action you have requested is not allowed.');
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// --------------------------------------------------------------------
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* @return string self::_csrf_hash
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public function get_csrf_hash()
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return $this->_csrf_hash;
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// --------------------------------------------------------------------
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* Get CSRF Token Name
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* @return string self::csrf_token_name
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public function get_csrf_token_name()
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return $this->_csrf_token_name;
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// --------------------------------------------------------------------
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* Sanitizes data so that Cross Site Scripting Hacks can be
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* prevented. This function does a fair amount of work but
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* it is extremely thorough, designed to prevent even the
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* most obscure XSS attempts. Nothing is ever 100% foolproof,
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* of course, but I haven't been able to get anything passed
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* Note: This function should only be used to deal with data
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* upon submission. It's not something that should
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* be used for general runtime processing.
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* This function was based in part on some code and ideas I
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* got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention
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* To help develop this script I used this great list of
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* vulnerabilities along with a few other hacks I've
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* harvested from examining vulnerabilities in other programs:
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* http://ha.ckers.org/xss.html
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* @param mixed string or array
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public function xss_clean($str, $is_image = FALSE)
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* Is the string an array?
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while (list($key) = each($str))
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$str[$key] = $this->xss_clean($str[$key]);
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* Remove Invisible Characters
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$str = remove_invisible_characters($str);
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// Validate Entities in URLs
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$str = $this->_validate_entities($str);
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* Just in case stuff like this is submitted:
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* <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
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* Note: Use rawurldecode() so it does not remove plus signs
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$str = rawurldecode($str);
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* Convert character entities to ASCII
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* This permits our tests below to work reliably.
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* We only convert entities that are within tags since
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* these are the ones that will pose security problems.
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$str = preg_replace_callback("/[a-z]+=([\'\"]).*?\\1/si", array($this, '_convert_attribute'), $str);
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$str = preg_replace_callback("/<\w+.*?(?=>|<|$)/si", array($this, '_decode_entity'), $str);
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* Remove Invisible Characters Again!
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$str = remove_invisible_characters($str);
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* Convert all tabs to spaces
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* This prevents strings like this: ja vascript
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* NOTE: we deal with spaces between characters later.
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* NOTE: preg_replace was found to be amazingly slow here on
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* large blocks of data, so we use str_replace.
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if (strpos($str, "\t") !== FALSE)
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$str = str_replace("\t", ' ', $str);
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* Capture converted string for later comparison
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$converted_string = $str;
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// Remove Strings that are never allowed
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$str = $this->_do_never_allowed($str);
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* Makes PHP tags safe
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* Note: XML tags are inadvertently replaced too:
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* But it doesn't seem to pose a problem.
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if ($is_image === TRUE)
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// Images have a tendency to have the PHP short opening and
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// closing tags every so often so we skip those and only
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// do the long opening tags.
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$str = preg_replace('/<\?(php)/i', "<?\\1", $str);
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$str = str_replace(array('<?', '?'.'>'), array('<?', '?>'), $str);
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* Compact any exploded words
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* This corrects words like: j a v a s c r i p t
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* These words are compacted back to their correct state.
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'javascript', 'expression', 'vbscript', 'script', 'base64',
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'applet', 'alert', 'document', 'write', 'cookie', 'window'
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foreach ($words as $word)
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for ($i = 0, $wordlen = strlen($word); $i < $wordlen; $i++)
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$temp .= substr($word, $i, 1)."\s*";
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// We only want to do this when it is followed by a non-word character
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// That way valid stuff like "dealer to" does not become "dealerto"
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$str = preg_replace_callback('#('.substr($temp, 0, -3).')(\W)#is', array($this, '_compact_exploded_words'), $str);
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* Remove disallowed Javascript in links or img tags
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* We used to do some version comparisons and use of stripos for PHP5,
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* but it is dog slow compared to these simplified non-capturing
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* preg_match(), especially if the pattern exists in the string
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if (preg_match("/<a/i", $str))
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$str = preg_replace_callback("#<a\s+([^>]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
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if (preg_match("/<img/i", $str))
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$str = preg_replace_callback("#<img\s+([^>]*?)(\s?/?>|$)#si", array($this, '_js_img_removal'), $str);
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if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str))
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$str = preg_replace("#<(/*)(script|xss)(.*?)\>#si", '[removed]', $str);
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while($original != $str);
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// Remove evil attributes such as style, onclick and xmlns
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$str = $this->_remove_evil_attributes($str, $is_image);
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* Sanitize naughty HTML elements
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* If a tag containing any of the words in the list
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* below is found, the tag gets converted to entities.
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* Becomes: <blink>
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$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';
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$str = preg_replace_callback('#<(/*\s*)('.$naughty.')([^><]*)([><]*)#is', array($this, '_sanitize_naughty_html'), $str);
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* Sanitize naughty scripting elements
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* Similar to above, only instead of looking for
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* tags it looks for PHP and JavaScript commands
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* that are disallowed. Rather than removing the
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* code, it simply converts the parenthesis to entities
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* rendering the code un-executable.
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* For example: eval('some code')
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* Becomes: eval('some code')
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$str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2(\\3)", $str);
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// This adds a bit of extra precaution in case
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// something got through the above filters
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$str = $this->_do_never_allowed($str);
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* Images are Handled in a Special Way
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* - Essentially, we want to know that after all of the character
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* conversion is done whether any unwanted, likely XSS, code was found.
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* If not, we return TRUE, as the image is clean.
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* However, if the string post-conversion does not matched the
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* string post-removal of XSS, then it fails, as there was unwanted XSS
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* code found and removed/changed during processing.
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if ($is_image === TRUE)
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return ($str == $converted_string) ? TRUE: FALSE;
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log_message('debug', "XSS Filtering completed");
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// --------------------------------------------------------------------
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* Random Hash for protecting URLs
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public function xss_hash()
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if ($this->_xss_hash == '')
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$this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
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return $this->_xss_hash;
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// --------------------------------------------------------------------
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* HTML Entities Decode
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* This function is a replacement for html_entity_decode()
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* The reason we are not using html_entity_decode() by itself is because
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* while it is not technically correct to leave out the semicolon
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* at the end of an entity most browsers will still interpret the entity
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* correctly. html_entity_decode() does not convert entities without
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* semicolons, so we are left with our own little solution here. Bummer.
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public function entity_decode($str, $charset='UTF-8')
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if (stristr($str, '&') === FALSE)
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$str = html_entity_decode($str, ENT_COMPAT, $charset);
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$str = preg_replace('~&#x(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);
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return preg_replace('~&#([0-9]{2,4})~e', 'chr(\\1)', $str);
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// --------------------------------------------------------------------
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public function sanitize_filename($str, $relative_path = FALSE)
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if ( ! $relative_path)
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$str = remove_invisible_characters($str, FALSE);
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return stripslashes(str_replace($bad, '', $str));
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// ----------------------------------------------------------------
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* Compact Exploded Words
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* Callback function for xss_clean() to remove whitespace from
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* things like j a v a s c r i p t
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protected function _compact_exploded_words($matches)
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return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
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// --------------------------------------------------------------------
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* Remove Evil HTML Attributes (like evenhandlers and style)
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* It removes the evil attribute and either:
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* - Everything up until a space
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* For example, everything between the pipes:
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* <a |style=document.write('hello');alert('world');| class=link>
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* - Everything inside the quotes
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* For example, everything between the pipes:
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* <a |style="document.write('hello'); alert('world');"| class="link">
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* @param string $str The string to check
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* @param boolean $is_image TRUE if this is an image
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* @return string The string with the evil attributes removed
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protected function _remove_evil_attributes($str, $is_image)
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// All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns
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$evil_attributes = array('on\w*', 'style', 'xmlns', 'formaction');
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if ($is_image === TRUE)
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* Adobe Photoshop puts XML metadata into JFIF images,
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* including namespacing, so we have to allow this for images.
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unset($evil_attributes[array_search('xmlns', $evil_attributes)]);
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// find occurrences of illegal attribute strings without quotes
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preg_match_all('/('.implode('|', $evil_attributes).')\s*=\s*([^\s>]*)/is', $str, $matches, PREG_SET_ORDER);
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foreach ($matches as $attr)
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$attribs[] = preg_quote($attr[0], '/');
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// find occurrences of illegal attribute strings with quotes (042 and 047 are octal quotes)
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preg_match_all("/(".implode('|', $evil_attributes).")\s*=\s*(\042|\047)([^\\2]*?)(\\2)/is", $str, $matches, PREG_SET_ORDER);
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foreach ($matches as $attr)
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$attribs[] = preg_quote($attr[0], '/');
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// replace illegal attribute strings that are inside an html tag
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if (count($attribs) > 0)
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$str = preg_replace("/<(\/?[^><]+?)([^A-Za-z<>\-])(.*?)(".implode('|', $attribs).")(.*?)([\s><])([><]*)/i", '<$1 $3$5$6$7', $str, -1, $count);
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// --------------------------------------------------------------------
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* Sanitize Naughty HTML
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* Callback function for xss_clean() to remove naughty HTML elements
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protected function _sanitize_naughty_html($matches)
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// encode opening brace
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$str = '<'.$matches[1].$matches[2].$matches[3];
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// encode captured opening or closing brace to prevent recursive vectors
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$str .= str_replace(array('>', '<'), array('>', '<'),
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// --------------------------------------------------------------------
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* Callback function for xss_clean() to sanitize links
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* This limits the PCRE backtracks, making it more performance friendly
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* and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
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* PHP 5.2+ on link-heavy strings
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protected function _js_link_removal($match)
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'#href=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|data\s*:)#si',
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$this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
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// --------------------------------------------------------------------
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* Callback function for xss_clean() to sanitize image tags
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* This limits the PCRE backtracks, making it more performance friendly
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* and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
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* PHP 5.2+ on image tag heavy strings
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protected function _js_img_removal($match)
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'#src=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si',
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$this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
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// --------------------------------------------------------------------
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* Attribute Conversion
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* Used as a callback for XSS Clean
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protected function _convert_attribute($match)
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return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]);
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// --------------------------------------------------------------------
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* Filters tag attributes for consistency and safety
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protected function _filter_attributes($str)
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if (preg_match_all('#\s*[a-z\-]+\s*=\s*(\042|\047)([^\\1]*?)\\1#is', $str, $matches))
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foreach ($matches[0] as $match)
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$out .= preg_replace("#/\*.*?\*/#s", '', $match);
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// --------------------------------------------------------------------
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* HTML Entity Decode Callback
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* Used as a callback for XSS Clean
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protected function _decode_entity($match)
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return $this->entity_decode($match[0], strtoupper(config_item('charset')));
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// --------------------------------------------------------------------
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* Validate URL entities
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* Called by xss_clean()
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protected function _validate_entities($str)
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* Protect GET variables in URLs
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// 901119URL5918AMP18930PROTECT8198
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$str = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $this->xss_hash()."\\1=\\2", $str);
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* Validate standard character entities
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* Add a semicolon if missing. We do this to enable
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* the conversion of entities to ASCII later.
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$str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);
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* Validate UTF16 two byte encoding (x00)
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* Just as above, adds a semicolon if missing.
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$str = preg_replace('#(&\#x?)([0-9A-F]+);?#i',"\\1\\2;",$str);
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* Un-Protect GET variables in URLs
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$str = str_replace($this->xss_hash(), '&', $str);
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// ----------------------------------------------------------------------
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* A utility function for xss_clean()
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protected function _do_never_allowed($str)
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$str = str_replace(array_keys($this->_never_allowed_str), $this->_never_allowed_str, $str);
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foreach ($this->_never_allowed_regex as $regex)
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$str = preg_replace('#'.$regex.'#is', '[removed]', $str);
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// --------------------------------------------------------------------
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* Set Cross Site Request Forgery Protection Cookie
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protected function _csrf_set_hash()
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if ($this->_csrf_hash == '')
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// If the cookie exists we will use it's value.
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// We don't necessarily want to regenerate it with
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// each page load since a page could contain embedded
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// sub-pages causing this feature to fail
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if (isset($_COOKIE[$this->_csrf_cookie_name]) &&
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preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1)
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return $this->_csrf_hash = $_COOKIE[$this->_csrf_cookie_name];
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return $this->_csrf_hash = md5(uniqid(rand(), TRUE));
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return $this->_csrf_hash;
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/* End of file Security.php */
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/* Location: ./system/libraries/Security.php */
b'\\ No newline at end of file'
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codeigniter/system/core/Security.php
