1091 lines
28 KiB
PHP
1091 lines
28 KiB
PHP
<?php
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/**
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* CodeIgniter
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*
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* An open source application development framework for PHP
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*
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* This content is released under the MIT License (MIT)
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*
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* Copyright (c) 2014 - 2019, British Columbia Institute of Technology
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*
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* @package CodeIgniter
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* @author EllisLab Dev Team
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* @copyright Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
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* @copyright Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
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* @license https://opensource.org/licenses/MIT MIT License
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* @link https://codeigniter.com
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* @since Version 1.0.0
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* @filesource
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*/
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defined('BASEPATH') OR exit('No direct script access allowed');
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/**
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* Security Class
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*
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* @package CodeIgniter
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* @subpackage Libraries
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* @category Security
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* @author EllisLab Dev Team
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* @link https://codeigniter.com/user_guide/libraries/security.html
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*/
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class CI_Security {
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/**
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* List of sanitize filename strings
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*
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* @var array
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*/
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public $filename_bad_chars = array(
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'../', '<!--', '-->', '<', '>',
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"'", '"', '&', '$', '#',
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'{', '}', '[', ']', '=',
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';', '?', '%20', '%22',
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'%3c', // <
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'%253c', // <
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'%3e', // >
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'%0e', // >
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'%28', // (
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'%29', // )
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'%2528', // (
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'%26', // &
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'%24', // $
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'%3f', // ?
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'%3b', // ;
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'%3d' // =
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);
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/**
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* Character set
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*
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* Will be overridden by the constructor.
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*
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* @var string
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*/
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public $charset = 'UTF-8';
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/**
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* XSS Hash
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*
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* Random Hash for protecting URLs.
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*
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* @var string
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*/
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protected $_xss_hash;
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/**
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* CSRF Hash
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*
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* Random hash for Cross Site Request Forgery protection cookie
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*
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* @var string
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*/
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protected $_csrf_hash;
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/**
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* CSRF Expire time
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*
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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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*
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* @var int
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*/
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protected $_csrf_expire = 7200;
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/**
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* CSRF Token name
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*
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* Token name for Cross Site Request Forgery protection cookie.
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*
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* @var string
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*/
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protected $_csrf_token_name = 'ci_csrf_token';
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/**
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* CSRF Cookie name
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*
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* Cookie name for Cross Site Request Forgery protection cookie.
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*
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* @var string
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*/
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protected $_csrf_cookie_name = 'ci_csrf_token';
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/**
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* List of never allowed strings
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*
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* @var array
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*/
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protected $_never_allowed_str = array(
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'document.cookie' => '[removed]',
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'(document).cookie' => '[removed]',
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'document.write' => '[removed]',
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'(document).write' => '[removed]',
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'.parentNode' => '[removed]',
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'.innerHTML' => '[removed]',
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'-moz-binding' => '[removed]',
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'<!--' => '<!--',
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'-->' => '-->',
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'<![CDATA[' => '<![CDATA[',
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'<comment>' => '<comment>',
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'<%' => '<%'
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);
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/**
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* List of never allowed regex replacements
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*
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* @var array
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*/
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protected $_never_allowed_regex = array(
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'javascript\s*:',
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'(\(?document\)?|\(?window\)?(\.document)?)\.(location|on\w*)',
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'expression\s*(\(|&\#40;)', // CSS and IE
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'vbscript\s*:', // IE, surprise!
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'wscript\s*:', // IE
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'jscript\s*:', // IE
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'vbs\s*:', // IE
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'Redirect\s+30\d',
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"([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"
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);
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/**
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* Class constructor
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*
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* @return void
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*/
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public function __construct()
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{
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// Is CSRF protection enabled?
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if (config_item('csrf_protection'))
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{
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// CSRF config
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foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key)
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{
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if (NULL !== ($val = config_item($key)))
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{
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$this->{'_'.$key} = $val;
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}
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}
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// Append application specific cookie prefix
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if ($cookie_prefix = config_item('cookie_prefix'))
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{
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$this->_csrf_cookie_name = $cookie_prefix.$this->_csrf_cookie_name;
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}
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// Set the CSRF hash
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$this->_csrf_set_hash();
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}
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$this->charset = strtoupper(config_item('charset'));
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log_message('info', 'Security Class Initialized');
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}
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// --------------------------------------------------------------------
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/**
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* CSRF Verify
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*
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* @return CI_Security
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*/
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public function csrf_verify()
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{
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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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{
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return $this->csrf_set_cookie();
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}
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// Check if URI has been whitelisted from CSRF checks
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if ($exclude_uris = config_item('csrf_exclude_uris'))
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{
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$uri = load_class('URI', 'core');
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foreach ($exclude_uris as $excluded)
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{
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if (preg_match('#^'.$excluded.'$#i'.(UTF8_ENABLED ? 'u' : ''), $uri->uri_string()))
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{
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return $this;
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}
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}
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}
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// Check CSRF token validity, but don't error on mismatch just yet - we'll want to regenerate
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$valid = isset($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name])
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&& hash_equals($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name]);
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// We kill this since we're done and we don't want to pollute the _POST array
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unset($_POST[$this->_csrf_token_name]);
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// Regenerate on every submission?
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if (config_item('csrf_regenerate'))
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{
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// Nothing should last forever
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unset($_COOKIE[$this->_csrf_cookie_name]);
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$this->_csrf_hash = NULL;
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}
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$this->_csrf_set_hash();
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$this->csrf_set_cookie();
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if ($valid !== TRUE)
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{
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$this->csrf_show_error();
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}
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log_message('info', 'CSRF token verified');
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return $this;
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}
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// --------------------------------------------------------------------
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/**
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* CSRF Set Cookie
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*
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* @codeCoverageIgnore
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* @return CI_Security
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*/
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public function csrf_set_cookie()
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{
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$expire = time() + $this->_csrf_expire;
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$secure_cookie = (bool) config_item('cookie_secure');
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if ($secure_cookie && ! is_https())
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{
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return FALSE;
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}
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setcookie(
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$this->_csrf_cookie_name,
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$this->_csrf_hash,
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$expire,
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config_item('cookie_path'),
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config_item('cookie_domain'),
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$secure_cookie,
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config_item('cookie_httponly')
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);
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log_message('info', 'CSRF cookie sent');
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return $this;
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}
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// --------------------------------------------------------------------
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/**
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* Show CSRF Error
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*
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* @return void
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*/
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public function csrf_show_error()
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{
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show_error('The action you have requested is not allowed.', 403);
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}
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// --------------------------------------------------------------------
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/**
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* Get CSRF Hash
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*
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* @see CI_Security::$_csrf_hash
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* @return string CSRF hash
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*/
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public function get_csrf_hash()
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{
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return $this->_csrf_hash;
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}
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// --------------------------------------------------------------------
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/**
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* Get CSRF Token Name
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*
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* @see CI_Security::$_csrf_token_name
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* @return string CSRF token name
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*/
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public function get_csrf_token_name()
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{
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return $this->_csrf_token_name;
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}
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// --------------------------------------------------------------------
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/**
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* XSS Clean
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*
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* Sanitizes data so that Cross Site Scripting Hacks can be
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* prevented. This method 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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* the filter.
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*
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* Note: Should only be used to deal with data upon submission.
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* It's not something that should be used for general
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* runtime processing.
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*
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* @link http://channel.bitflux.ch/wiki/XSS_Prevention
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* Based in part on some code and ideas from Bitflux.
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*
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* @link http://ha.ckers.org/xss.html
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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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*
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* @param string|string[] $str Input data
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* @param bool $is_image Whether the input is an image
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* @return string
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*/
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public function xss_clean($str, $is_image = FALSE)
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{
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// Is the string an array?
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if (is_array($str))
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{
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foreach ($str as $key => &$value)
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{
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$str[$key] = $this->xss_clean($value);
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}
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return $str;
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}
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// Remove Invisible Characters
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$str = remove_invisible_characters($str);
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/*
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* URL Decode
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*
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* Just in case stuff like this is submitted:
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*
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* <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
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*
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* Note: Use rawurldecode() so it does not remove plus signs
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*/
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if (stripos($str, '%') !== false)
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{
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do
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{
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$oldstr = $str;
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$str = rawurldecode($str);
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$str = preg_replace_callback('#%(?:\s*[0-9a-f]){2,}#i', array($this, '_urldecodespaces'), $str);
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}
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while ($oldstr !== $str);
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unset($oldstr);
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}
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/*
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* Convert character entities to ASCII
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*
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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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*/
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$str = preg_replace_callback("/[^a-z0-9>]+[a-z0-9]+=([\'\"]).*?\\1/si", array($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($str);
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/*
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* Convert all tabs to spaces
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*
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* This prevents strings like this: ja vascript
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* NOTE: we deal with spaces between characters later.
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* NOTE: preg_replace was found to be amazingly slow here on
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* large blocks of data, so we use str_replace.
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*/
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$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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/*
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* Makes PHP tags safe
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*
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* Note: XML tags are inadvertently replaced too:
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*
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* <?xml
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*
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* But it doesn't seem to pose a problem.
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*/
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if ($is_image === TRUE)
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{
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// Images have a tendency to have the PHP short opening and
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// closing tags every so often so we skip those and only
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// do the long opening tags.
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$str = preg_replace('/<\?(php)/i', '<?\\1', $str);
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}
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else
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{
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$str = str_replace(array('<?', '?'.'>'), array('<?', '?>'), $str);
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}
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/*
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* Compact any exploded words
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*
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* This corrects words like: j a v a s c r i p t
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* These words are compacted back to their correct state.
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*/
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$words = array(
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'javascript', 'expression', 'vbscript', 'jscript', 'wscript',
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'vbs', 'script', 'base64', 'applet', 'alert', 'document',
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'write', 'cookie', 'window', 'confirm', 'prompt', 'eval'
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);
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foreach ($words as $word)
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{
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$word = implode('\s*', str_split($word)).'\s*';
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// We only want to do this when it is followed by a non-word character
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// That way valid stuff like "dealer to" does not become "dealerto"
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$str = preg_replace_callback('#('.substr($word, 0, -3).')(\W)#is', array($this, '_compact_exploded_words'), $str);
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}
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/*
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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(),
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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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*
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* Note: It was reported that not only space characters, but all in
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* the following pattern can be parsed as separators between a tag name
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* and its attributes: [\d\s"\'`;,\/\=\(\x00\x0B\x09\x0C]
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* ... however, remove_invisible_characters() above already strips the
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* hex-encoded ones, so we'll skip them below.
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*/
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do
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{
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$original = $str;
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if (preg_match('/<a/i', $str))
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{
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$str = preg_replace_callback('#<a(?:rea)?[^a-z0-9>]+([^>]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str);
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}
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if (preg_match('/<img/i', $str))
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{
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$str = preg_replace_callback('#<img[^a-z0-9]+([^>]*?)(?:\s?/?>|$)#si', array($this, '_js_img_removal'), $str);
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}
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if (preg_match('/script|xss/i', $str))
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{
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$str = preg_replace('#</*(?:script|xss).*?>#si', '[removed]', $str);
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}
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}
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while ($original !== $str);
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unset($original);
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/*
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* Sanitize naughty HTML elements
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*
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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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*
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* So this: <blink>
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* Becomes: <blink>
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*/
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$pattern = '#'
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.'<((?<slash>/*\s*)((?<tagName>[a-z0-9]+)(?=[^a-z0-9]|$)|.+)' // tag start and name, followed by a non-tag character
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.'[^\s\042\047a-z0-9>/=]*' // a valid attribute character immediately after the tag would count as a separator
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// optional attributes
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.'(?<attributes>(?:[\s\042\047/=]*' // non-attribute characters, excluding > (tag close) for obvious reasons
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.'[^\s\042\047>/=]+' // attribute characters
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// optional attribute-value
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.'(?:\s*=' // attribute-value separator
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.'(?:[^\s\042\047=><`]+|\s*\042[^\042]*\042|\s*\047[^\047]*\047|\s*(?U:[^\s\042\047=><`]*))' // single, double or non-quoted value
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.')?' // end optional attribute-value group
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.')*)' // end optional attributes group
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.'[^>]*)(?<closeTag>\>)?#isS';
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// Note: It would be nice to optimize this for speed, BUT
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// only matching the naughty elements here results in
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// false positives and in turn - vulnerabilities!
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do
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{
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$old_str = $str;
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$str = preg_replace_callback($pattern, array($this, '_sanitize_naughty_html'), $str);
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}
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while ($old_str !== $str);
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unset($old_str);
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/*
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* Sanitize naughty scripting elements
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*
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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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*
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* For example: eval('some code')
|
|
* Becomes: eval('some code')
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*/
|
|
$str = preg_replace(
|
|
'#(alert|prompt|confirm|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si',
|
|
'\\1\\2(\\3)',
|
|
$str
|
|
);
|
|
|
|
// Same thing, but for "tag functions" (e.g. eval`some code`)
|
|
// See https://github.com/bcit-ci/CodeIgniter/issues/5420
|
|
$str = preg_replace(
|
|
'#(alert|prompt|confirm|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)`(.*?)`#si',
|
|
'\\1\\2`\\3`',
|
|
$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);
|
|
}
|
|
|
|
return $str;
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* XSS Hash
|
|
*
|
|
* Generates the XSS hash if needed and returns it.
|
|
*
|
|
* @see CI_Security::$_xss_hash
|
|
* @return string XSS hash
|
|
*/
|
|
public function xss_hash()
|
|
{
|
|
if ($this->_xss_hash === NULL)
|
|
{
|
|
$rand = $this->get_random_bytes(16);
|
|
$this->_xss_hash = ($rand === FALSE)
|
|
? md5(uniqid(mt_rand(), TRUE))
|
|
: bin2hex($rand);
|
|
}
|
|
|
|
return $this->_xss_hash;
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Get random bytes
|
|
*
|
|
* @param int $length Output length
|
|
* @return string
|
|
*/
|
|
public function get_random_bytes($length)
|
|
{
|
|
if (empty($length) OR ! ctype_digit((string) $length))
|
|
{
|
|
return FALSE;
|
|
}
|
|
|
|
if (function_exists('random_bytes'))
|
|
{
|
|
try
|
|
{
|
|
// The cast is required to avoid TypeError
|
|
return random_bytes((int) $length);
|
|
}
|
|
catch (Exception $e)
|
|
{
|
|
// If random_bytes() can't do the job, we can't either ...
|
|
// There's no point in using fallbacks.
|
|
log_message('error', $e->getMessage());
|
|
return FALSE;
|
|
}
|
|
}
|
|
|
|
// Unfortunately, none of the following PRNGs is guaranteed to exist ...
|
|
if (defined('MCRYPT_DEV_URANDOM') && ($output = mcrypt_create_iv($length, MCRYPT_DEV_URANDOM)) !== FALSE)
|
|
{
|
|
return $output;
|
|
}
|
|
|
|
|
|
if (is_readable('/dev/urandom') && ($fp = fopen('/dev/urandom', 'rb')) !== FALSE)
|
|
{
|
|
// Try not to waste entropy ...
|
|
is_php('5.4') && stream_set_chunk_size($fp, $length);
|
|
$output = fread($fp, $length);
|
|
fclose($fp);
|
|
if ($output !== FALSE)
|
|
{
|
|
return $output;
|
|
}
|
|
}
|
|
|
|
if (function_exists('openssl_random_pseudo_bytes'))
|
|
{
|
|
return openssl_random_pseudo_bytes($length);
|
|
}
|
|
|
|
return FALSE;
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* HTML Entities Decode
|
|
*
|
|
* 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.
|
|
*
|
|
* @link http://php.net/html-entity-decode
|
|
*
|
|
* @param string $str Input
|
|
* @param string $charset Character set
|
|
* @return string
|
|
*/
|
|
public function entity_decode($str, $charset = NULL)
|
|
{
|
|
if (strpos($str, '&') === FALSE)
|
|
{
|
|
return $str;
|
|
}
|
|
|
|
static $_entities;
|
|
|
|
isset($charset) OR $charset = $this->charset;
|
|
$flag = is_php('5.4')
|
|
? ENT_COMPAT | ENT_HTML5
|
|
: ENT_COMPAT;
|
|
|
|
if ( ! isset($_entities))
|
|
{
|
|
$_entities = array_map('strtolower', get_html_translation_table(HTML_ENTITIES, $flag, $charset));
|
|
|
|
// If we're not on PHP 5.4+, add the possibly dangerous HTML 5
|
|
// entities to the array manually
|
|
if ($flag === ENT_COMPAT)
|
|
{
|
|
$_entities[':'] = ':';
|
|
$_entities['('] = '(';
|
|
$_entities[')'] = ')';
|
|
$_entities["\n"] = '
';
|
|
$_entities["\t"] = '	';
|
|
}
|
|
}
|
|
|
|
do
|
|
{
|
|
$str_compare = $str;
|
|
|
|
// Decode standard entities, avoiding false positives
|
|
if (preg_match_all('/&[a-z]{2,}(?![a-z;])/i', $str, $matches))
|
|
{
|
|
$replace = array();
|
|
$matches = array_unique(array_map('strtolower', $matches[0]));
|
|
foreach ($matches as &$match)
|
|
{
|
|
if (($char = array_search($match.';', $_entities, TRUE)) !== FALSE)
|
|
{
|
|
$replace[$match] = $char;
|
|
}
|
|
}
|
|
|
|
$str = str_replace(array_keys($replace), array_values($replace), $str);
|
|
}
|
|
|
|
// Decode numeric & UTF16 two byte entities
|
|
$str = html_entity_decode(
|
|
preg_replace('/(&#(?:x0*[0-9a-f]{2,5}(?![0-9a-f;])|(?:0*\d{2,4}(?![0-9;]))))/iS', '$1;', $str),
|
|
$flag,
|
|
$charset
|
|
);
|
|
|
|
if ($flag === ENT_COMPAT)
|
|
{
|
|
$str = str_replace(array_values($_entities), array_keys($_entities), $str);
|
|
}
|
|
}
|
|
while ($str_compare !== $str);
|
|
return $str;
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Sanitize Filename
|
|
*
|
|
* @param string $str Input file name
|
|
* @param bool $relative_path Whether to preserve paths
|
|
* @return string
|
|
*/
|
|
public function sanitize_filename($str, $relative_path = FALSE)
|
|
{
|
|
$bad = $this->filename_bad_chars;
|
|
|
|
if ( ! $relative_path)
|
|
{
|
|
$bad[] = './';
|
|
$bad[] = '/';
|
|
}
|
|
|
|
$str = remove_invisible_characters($str, FALSE);
|
|
|
|
do
|
|
{
|
|
$old = $str;
|
|
$str = str_replace($bad, '', $str);
|
|
}
|
|
while ($old !== $str);
|
|
|
|
return stripslashes($str);
|
|
}
|
|
|
|
// ----------------------------------------------------------------
|
|
|
|
/**
|
|
* Strip Image Tags
|
|
*
|
|
* @param string $str
|
|
* @return string
|
|
*/
|
|
public function strip_image_tags($str)
|
|
{
|
|
return preg_replace(
|
|
array(
|
|
'#<img[\s/]+.*?src\s*=\s*(["\'])([^\\1]+?)\\1.*?\>#i',
|
|
'#<img[\s/]+.*?src\s*=\s*?(([^\s"\'=<>`]+)).*?\>#i'
|
|
),
|
|
'\\2',
|
|
$str
|
|
);
|
|
}
|
|
|
|
// ----------------------------------------------------------------
|
|
|
|
/**
|
|
* URL-decode taking spaces into account
|
|
*
|
|
* @see https://github.com/bcit-ci/CodeIgniter/issues/4877
|
|
* @param array $matches
|
|
* @return string
|
|
*/
|
|
protected function _urldecodespaces($matches)
|
|
{
|
|
$input = $matches[0];
|
|
$nospaces = preg_replace('#\s+#', '', $input);
|
|
return ($nospaces === $input)
|
|
? $input
|
|
: rawurldecode($nospaces);
|
|
}
|
|
|
|
// ----------------------------------------------------------------
|
|
|
|
/**
|
|
* Compact Exploded Words
|
|
*
|
|
* Callback method for xss_clean() to remove whitespace from
|
|
* things like 'j a v a s c r i p t'.
|
|
*
|
|
* @used-by CI_Security::xss_clean()
|
|
* @param array $matches
|
|
* @return string
|
|
*/
|
|
protected function _compact_exploded_words($matches)
|
|
{
|
|
return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Sanitize Naughty HTML
|
|
*
|
|
* Callback method for xss_clean() to remove naughty HTML elements.
|
|
*
|
|
* @used-by CI_Security::xss_clean()
|
|
* @param array $matches
|
|
* @return string
|
|
*/
|
|
protected function _sanitize_naughty_html($matches)
|
|
{
|
|
static $naughty_tags = array(
|
|
'alert', 'area', 'prompt', 'confirm', 'applet', 'audio', 'basefont', 'base', 'behavior', 'bgsound',
|
|
'blink', 'body', 'embed', 'expression', 'form', 'frameset', 'frame', 'head', 'html', 'ilayer',
|
|
'iframe', 'input', 'button', 'select', 'isindex', 'layer', 'link', 'meta', 'keygen', 'object',
|
|
'plaintext', 'style', 'script', 'textarea', 'title', 'math', 'video', 'svg', 'xml', 'xss'
|
|
);
|
|
|
|
static $evil_attributes = array(
|
|
'on\w+', 'style', 'xmlns', 'formaction', 'form', 'xlink:href', 'FSCommand', 'seekSegmentTime'
|
|
);
|
|
|
|
// First, escape unclosed tags
|
|
if (empty($matches['closeTag']))
|
|
{
|
|
return '<'.$matches[1];
|
|
}
|
|
// Is the element that we caught naughty? If so, escape it
|
|
elseif (in_array(strtolower($matches['tagName']), $naughty_tags, TRUE))
|
|
{
|
|
return '<'.$matches[1].'>';
|
|
}
|
|
// For other tags, see if their attributes are "evil" and strip those
|
|
elseif (isset($matches['attributes']))
|
|
{
|
|
// We'll store the already filtered attributes here
|
|
$attributes = array();
|
|
|
|
// Attribute-catching pattern
|
|
$attributes_pattern = '#'
|
|
.'(?<name>[^\s\042\047>/=]+)' // attribute characters
|
|
// optional attribute-value
|
|
.'(?:\s*=(?<value>[^\s\042\047=><`]+|\s*\042[^\042]*\042|\s*\047[^\047]*\047|\s*(?U:[^\s\042\047=><`]*)))' // attribute-value separator
|
|
.'#i';
|
|
|
|
// Blacklist pattern for evil attribute names
|
|
$is_evil_pattern = '#^('.implode('|', $evil_attributes).')$#i';
|
|
|
|
// Each iteration filters a single attribute
|
|
do
|
|
{
|
|
// Strip any non-alpha characters that may precede an attribute.
|
|
// Browsers often parse these incorrectly and that has been a
|
|
// of numerous XSS issues we've had.
|
|
$matches['attributes'] = preg_replace('#^[^a-z]+#i', '', $matches['attributes']);
|
|
|
|
if ( ! preg_match($attributes_pattern, $matches['attributes'], $attribute, PREG_OFFSET_CAPTURE))
|
|
{
|
|
// No (valid) attribute found? Discard everything else inside the tag
|
|
break;
|
|
}
|
|
|
|
if (
|
|
// Is it indeed an "evil" attribute?
|
|
preg_match($is_evil_pattern, $attribute['name'][0])
|
|
// Or does it have an equals sign, but no value and not quoted? Strip that too!
|
|
OR (trim($attribute['value'][0]) === '')
|
|
)
|
|
{
|
|
$attributes[] = 'xss=removed';
|
|
}
|
|
else
|
|
{
|
|
$attributes[] = $attribute[0][0];
|
|
}
|
|
|
|
$matches['attributes'] = substr($matches['attributes'], $attribute[0][1] + strlen($attribute[0][0]));
|
|
}
|
|
while ($matches['attributes'] !== '');
|
|
|
|
$attributes = empty($attributes)
|
|
? ''
|
|
: ' '.implode(' ', $attributes);
|
|
return '<'.$matches['slash'].$matches['tagName'].$attributes.'>';
|
|
}
|
|
|
|
return $matches[0];
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* JS Link Removal
|
|
*
|
|
* Callback method 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.
|
|
*
|
|
* @used-by CI_Security::xss_clean()
|
|
* @param array $match
|
|
* @return string
|
|
*/
|
|
protected function _js_link_removal($match)
|
|
{
|
|
return str_replace(
|
|
$match[1],
|
|
preg_replace(
|
|
'#href=.*?(?:(?:alert|prompt|confirm)(?:\(|&\#40;|`|&\#96;)|javascript:|livescript:|mocha:|charset=|window\.|\(?document\)?\.|\.cookie|<script|<xss|d\s*a\s*t\s*a\s*:)#si',
|
|
'',
|
|
$this->_filter_attributes($match[1])
|
|
),
|
|
$match[0]
|
|
);
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* JS Image Removal
|
|
*
|
|
* Callback method 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.
|
|
*
|
|
* @used-by CI_Security::xss_clean()
|
|
* @param array $match
|
|
* @return string
|
|
*/
|
|
protected function _js_img_removal($match)
|
|
{
|
|
return str_replace(
|
|
$match[1],
|
|
preg_replace(
|
|
'#src=.*?(?:(?:alert|prompt|confirm|eval)(?:\(|&\#40;|`|&\#96;)|javascript:|livescript:|mocha:|charset=|window\.|\(?document\)?\.|\.cookie|<script|<xss|base64\s*,)#si',
|
|
'',
|
|
$this->_filter_attributes($match[1])
|
|
),
|
|
$match[0]
|
|
);
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Attribute Conversion
|
|
*
|
|
* @used-by CI_Security::xss_clean()
|
|
* @param array $match
|
|
* @return string
|
|
*/
|
|
protected function _convert_attribute($match)
|
|
{
|
|
return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]);
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Filter Attributes
|
|
*
|
|
* Filters tag attributes for consistency and safety.
|
|
*
|
|
* @used-by CI_Security::_js_img_removal()
|
|
* @used-by CI_Security::_js_link_removal()
|
|
* @param string $str
|
|
* @return string
|
|
*/
|
|
protected function _filter_attributes($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-by CI_Security::xss_clean()
|
|
* @param array $match
|
|
* @return string
|
|
*/
|
|
protected function _decode_entity($match)
|
|
{
|
|
// Protect GET variables in URLs
|
|
// 901119URL5918AMP18930PROTECT8198
|
|
$match = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-/]+)|i', $this->xss_hash().'\\1=\\2', $match[0]);
|
|
|
|
// Decode, then un-protect URL GET vars
|
|
return str_replace(
|
|
$this->xss_hash(),
|
|
'&',
|
|
$this->entity_decode($match, $this->charset)
|
|
);
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Do Never Allowed
|
|
*
|
|
* @used-by CI_Security::xss_clean()
|
|
* @param string
|
|
* @return string
|
|
*/
|
|
protected function _do_never_allowed($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 $str;
|
|
}
|
|
|
|
// --------------------------------------------------------------------
|
|
|
|
/**
|
|
* Set CSRF Hash and Cookie
|
|
*
|
|
* @return string
|
|
*/
|
|
protected function _csrf_set_hash()
|
|
{
|
|
if ($this->_csrf_hash === NULL)
|
|
{
|
|
// If the cookie exists we will use its 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]) && is_string($_COOKIE[$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];
|
|
}
|
|
|
|
$rand = $this->get_random_bytes(16);
|
|
$this->_csrf_hash = ($rand === FALSE)
|
|
? md5(uniqid(mt_rand(), TRUE))
|
|
: bin2hex($rand);
|
|
}
|
|
|
|
return $this->_csrf_hash;
|
|
}
|
|
|
|
}
|