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241 lines
8.6 KiB
241 lines
8.6 KiB
<?php
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/* For licensing terms, see /license.txt */
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/**
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* This is the security library for Chamilo.
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*
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* This library is based on recommendations found in the PHP5 Certification
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* Guide published at PHP|Architect, and other recommendations found on
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* http://www.phpsec.org/
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* The principles here are that all data is tainted (most scripts of Chamilo are
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* open to the public or at least to a certain public that could be malicious
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* under specific circumstances). We use the white list approach, where as we
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* consider that data can only be used in the database or in a file if it has
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* been filtered.
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*
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* For session fixation, use ...
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* For session hijacking, use get_ua() and check_ua()
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* For Cross-Site Request Forgeries, use get_token() and check_tocken()
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* For basic filtering, use filter()
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* For files inclusions (using dynamic paths) use check_rel_path() and check_abs_path()
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*
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* @package chamilo.library
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* @author Yannick Warnier <ywarnier@beeznest.org>
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*/
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/**
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* Security class
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*
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* Include/require it in your code and call Security::function()
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* to use its functionalities.
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*
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* This class can also be used as a container for filtered data, by creating
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* a new Security object and using $secure->filter($new_var,[more options])
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* and then using $secure->clean['var'] as a filtered equivalent, although
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* this is *not* mandatory at all.
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*/
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class Security {
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public static $clean = array();
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/**
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* Checks if the absolute path (directory) given is really under the
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* checker path (directory)
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* @param string Absolute path to be checked (with trailing slash)
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* @param string Checker path under which the path should be (absolute path, with trailing slash, get it from api_get_path(SYS_COURSE_PATH))
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* @return bool True if the path is under the checker, false otherwise
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*/
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public static function check_abs_path ($abs_path,$checker_path) {
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if (empty($checker_path)) {return false;} //checker path must be set
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$true_path=str_replace("\\", "/", realpath($abs_path));
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$found = strpos($true_path.'/',$checker_path);
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if ($found===0) {
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return true;
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}
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return false;
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}
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/**
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* Checks if the relative path (directory) given is really under the
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* checker path (directory)
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* @param string Relative path to be checked (relative to the current directory) (with trailing slash)
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* @param string Checker path under which the path should be (absolute path, with trailing slash, get it from api_get_path(SYS_COURSE_PATH))
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* @return bool True if the path is under the checker, false otherwise
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*/
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public static function check_rel_path ($rel_path,$checker_path) {
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if (empty($checker_path)){return false;} //checker path must be set
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$current_path = getcwd(); //no trailing slash
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if (substr($rel_path,-1,1)!='/') {
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$rel_path = '/'.$rel_path;
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}
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$abs_path = $current_path.$rel_path;
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$true_path=str_replace("\\", "/", realpath($abs_path));
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$found = strpos($true_path.'/',$checker_path);
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if ($found===0) {
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return true;
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}
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return false;
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}
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/**
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* Filters dangerous filenames (*.php[.]?* and .htaccess) and returns it in
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* a non-executable form (for PHP and htaccess, this is still vulnerable to
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* other languages' files extensions)
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* @param string Unfiltered filename
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* @param string Filtered filename
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*/
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public static function filter_filename ($filename) {
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require_once(api_get_path(LIBRARY_PATH).'fileUpload.lib.php');
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return disable_dangerous_file($filename);
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}
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/**
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* This function checks that the token generated in get_token() has been kept (prevents
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* Cross-Site Request Forgeries attacks)
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* @param string The array in which to get the token ('get' or 'post')
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* @return bool True if it's the right token, false otherwise
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*/
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public static function check_token ($array='post') {
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switch ($array) {
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case 'get':
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if (isset($_SESSION['sec_token']) && isset($_GET['sec_token']) && $_SESSION['sec_token'] === $_GET['sec_token']) {
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return true;
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}
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return false;
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case 'post':
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if (isset($_SESSION['sec_token']) && isset($_POST['sec_token']) && $_SESSION['sec_token'] === $_POST['sec_token']) {
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return true;
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}
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return false;
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default:
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if (isset($_SESSION['sec_token']) && isset($array) && $_SESSION['sec_token'] === $array) {
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return true;
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}
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return false;
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}
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return false; //just in case, don't let anything slip
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}
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/**
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* Checks the user agent of the client as recorder by get_ua() to prevent
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* most session hijacking attacks.
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* @return bool True if the user agent is the same, false otherwise
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*/
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public static function check_ua () {
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if (isset($_SESSION['sec_ua']) and $_SESSION['sec_ua'] === $_SERVER['HTTP_USER_AGENT'].$_SESSION['sec_ua_seed']) {
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return true;
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}
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return false;
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}
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/**
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* Clear the security token from the session
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* @return void
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*/
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public static function clear_token () {
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$_SESSION['sec_token'] = null;
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unset($_SESSION['sec_token']);
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}
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/**
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* This function sets a random token to be included in a form as a hidden field
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* and saves it into the user's session. Returns an HTML form element
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* This later prevents Cross-Site Request Forgeries by checking that the user is really
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* the one that sent this form in knowingly (this form hasn't been generated from
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* another website visited by the user at the same time).
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* Check the token with check_token()
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* @return string Hidden-type input ready to insert into a form
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*/
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public static function get_HTML_token () {
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$token = md5(uniqid(rand(),TRUE));
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$string = '<input type="hidden" name="sec_token" value="'.$token.'"/>';
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$_SESSION['sec_token'] = $token;
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return $string;
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}
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/**
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* This function sets a random token to be included in a form as a hidden field
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* and saves it into the user's session.
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* This later prevents Cross-Site Request Forgeries by checking that the user is really
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* the one that sent this form in knowingly (this form hasn't been generated from
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* another website visited by the user at the same time).
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* Check the token with check_token()
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* @return string Token
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*/
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public static function get_token () {
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$token = md5(uniqid(rand(),TRUE));
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$_SESSION['sec_token'] = $token;
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return $token;
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}
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/**
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* Gets the user agent in the session to later check it with check_ua() to prevent
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* most cases of session hijacking.
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* @return void
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*/
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public static function get_ua () {
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$_SESSION['sec_ua_seed'] = uniqid(rand(),TRUE);
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$_SESSION['sec_ua'] = $_SERVER['HTTP_USER_AGENT'].$_SESSION['sec_ua_seed'];
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}
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/**
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* This function filters a variable to the type given, with the options given
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* @param mixed The variable to be filtered
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* @param string The type of variable we expect (bool,int,float,string)
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* @param array Additional options
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* @return bool True if variable was filtered and added to the current object, false otherwise
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*/
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public static function filter ($var,$type='string',$options=array()) {
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//This function is not finished! Do not use!
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$result = false;
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//get variable name and value
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$args = func_get_args();
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$names =array_keys($args);
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$name = $names[0];
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$value = $args[$name];
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switch ($type) {
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case 'bool':
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$result = (bool) $var;
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break;
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case 'int':
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$result = (int) $var;
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break;
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case 'float':
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$result = (float) $var;
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break;
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case 'string/html':
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$result = self::remove_XSS($var);
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break;
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case 'string/db':
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$result = Database::escape_string($var);
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break;
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case 'array':
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//an array variable shouldn't be given to the filter
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return false;
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default:
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return false;
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}
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if (!empty($option['save'])) {
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$this->clean[$name]=$result;
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}
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return $result;
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}
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/**
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* This function returns a variable from the clean array. If the variable doesn't exist,
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* it returns null
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* @param string Variable name
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* @return mixed Variable or NULL on error
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*/
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public static function get ($varname) {
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if (isset(self::$clean[$varname])) {
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return self::$clean[$varname];
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}
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return NULL;
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}
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/**
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* This function tackles the XSS injections.
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* Filtering for XSS is very easily done by using the htmlentities() function.
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* This kind of filtering prevents JavaScript snippets to be understood as such.
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* @param mixed The variable to filter for XSS, this params can be a string or an array (example : array(x,y))
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* @param integer The user status,constant allowed(STUDENT,COURSEMANAGER,ANONYMOUS,COURSEMANAGERLOWSECURITY)
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* @return mixed Filtered string or array
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*/
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public static function remove_XSS ($var,$user_status=ANONYMOUS) {
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$purifier = new HTMLPurifier(null,$user_status);
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if (is_array($var)) {
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return $purifier->purifyArray($var);
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} else {
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return $purifier->purify($var);
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}
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}
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}
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