libraries/Input.php

   1 <?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
   2 /**
   3  * CodeIgniter
   4  *
   5  * An open source application development framework for PHP 4.3.2 or newer
   6  *
   7  * @package             CodeIgniter
   8  * @author              ExpressionEngine Dev Team
   9  * @copyright   Copyright (c) 2008 - 2009, EllisLab, Inc.
  10  * @license             http://codeigniter.com/user_guide/license.html
  11  * @link                http://codeigniter.com
  12  * @since               Version 1.0
  13  * @filesource
  14  */
  15
  16 // ------------------------------------------------------------------------
  17
  18 /**
  19  * Input Class
  20  *
  21  * Pre-processes global input data for security
  22  *
  23  * @package             CodeIgniter
  24  * @subpackage  Libraries
  25  * @category    Input
  26  * @author              ExpressionEngine Dev Team
  27  * @link                http://codeigniter.com/user_guide/libraries/input.html
  28  */
  29 class CI_Input {
  30         var $use_xss_clean              = FALSE;
  31         var $xss_hash                   = '';
  32         var $ip_address                 = FALSE;
  33         var $user_agent                 = FALSE;
  34         var $allow_get_array    = FALSE;
  35
  36         /* never allowed, string replacement */
  37         var $never_allowed_str = array(
  38                                                                         'document.cookie'       => '[removed]',
  39                                                                         'document.write'        => '[removed]',
  40                                                                         '.parentNode'           => '[removed]',
  41                                                                         '.innerHTML'            => '[removed]',
  42                                                                         'window.location'       => '[removed]',
  43                                                                         '-moz-binding'          => '[removed]',
  44                                                                         '<!--'                          => '&lt;!--',
  45                                                                         '-->'                           => '--&gt;',
  46                                                                         '<![CDATA['                     => '&lt;![CDATA['
  47                                                                         );
  48         /* never allowed, regex replacement */
  49         var $never_allowed_regex = array(
  50                                                                                 "javascript\s*:"                        => '[removed]',
  51                                                                                 "expression\s*(\(|&\#40;)"      => '[removed]', // CSS and IE
  52                                                                                 "vbscript\s*:"                          => '[removed]', // IE, surprise!
  53                                                                                 "Redirect\s+302"                        => '[removed]'
  54                                                                         );
  55
  56         /**
  57         * Constructor
  58         *
  59         * Sets whether to globally enable the XSS processing
  60         * and whether to allow the $_GET array
  61         *
  62         * @access       public
  63         */
  64         function CI_Input()
  65         {
  66                 log_message('debug', "Input Class Initialized");
  67
  68                 $CFG =& load_class('Config');
  69                 $this->use_xss_clean    = ($CFG->item('global_xss_filtering') === TRUE) ? TRUE : FALSE;
  70                 $this->allow_get_array  = ($CFG->item('enable_query_strings') === TRUE) ? TRUE : FALSE;
  71                 $this->_sanitize_globals();
  72         }
  73
  74         // --------------------------------------------------------------------
  75
  76         /**
  77         * Sanitize Globals
  78         *
  79         * This function does the following:
  80         *
  81         * Unsets $_GET data (if query strings are not enabled)
  82         *
  83         * Unsets all globals if register_globals is enabled
  84         *
  85         * Standardizes newline characters to \n
  86         *
  87         * @access       private
  88         * @return       void
  89         */
  90         function _sanitize_globals()
  91         {
  92                 // Would kind of be "wrong" to unset any of these GLOBALS
  93                 $protected = array('_SERVER', '_GET', '_POST', '_FILES', '_REQUEST', '_SESSION', '_ENV', 'GLOBALS', 'HTTP_RAW_POST_DATA',
  94                                                         'system_folder', 'application_folder', 'BM', 'EXT', 'CFG', 'URI', 'RTR', 'OUT', 'IN');
  95
  96                 // Unset globals for security.
  97                 // This is effectively the same as register_globals = off
  98                 foreach (array($_GET, $_POST, $_COOKIE, $_SERVER, $_FILES, $_ENV, (isset($_SESSION) && is_array($_SESSION)) ? $_SESSION : array()) as $global)
  99                 {
 100                         if ( ! is_array($global))
 101                         {
 102                                 if ( ! in_array($global, $protected))
 103                                 {
 104                                         unset($GLOBALS[$global]);
 105                                 }
 106                         }
 107                         else
 108                         {
 109                                 foreach ($global as $key => $val)
 110                                 {
 111                                         if ( ! in_array($key, $protected))
 112                                         {
 113                                                 unset($GLOBALS[$key]);
 114                                         }
 115
 116                                         if (is_array($val))
 117                                         {
 118                                                 foreach($val as $k => $v)
 119                                                 {
 120                                                         if ( ! in_array($k, $protected))
 121                                                         {
 122                                                                 unset($GLOBALS[$k]);
 123                                                         }
 124                                                 }
 125                                         }
 126                                 }
 127                         }
 128                 }
 129
 130                 // Is $_GET data allowed? If not we'll set the $_GET to an empty array
 131                 if ($this->allow_get_array == FALSE)
 132                 {
 133                         $_GET = array();
 134                 }
 135                 else
 136                 {
 137                         $_GET = $this->_clean_input_data($_GET);
 138                 }
 139
 140                 // Clean $_POST Data
 141                 $_POST = $this->_clean_input_data($_POST);
 142
 143                 // Clean $_COOKIE Data
 144                 // Also get rid of specially treated cookies that might be set by a server
 145                 // or silly application, that are of no use to a CI application anyway
 146                 // but that when present will trip our 'Disallowed Key Characters' alarm
 147                 // http://www.ietf.org/rfc/rfc2109.txt
 148                 // note that the key names below are single quoted strings, and are not PHP variables
 149                 unset($_COOKIE['$Version']);
 150                 unset($_COOKIE['$Path']);
 151                 unset($_COOKIE['$Domain']);
 152                 $_COOKIE = $this->_clean_input_data($_COOKIE);
 153
 154                 log_message('debug', "Global POST and COOKIE data sanitized");
 155         }
 156
 157         // --------------------------------------------------------------------
 158
 159         /**
 160         * Clean Input Data
 161         *
 162         * This is a helper function. It escapes data and
 163         * standardizes newline characters to \n
 164         *
 165         * @access       private
 166         * @param        string
 167         * @return       string
 168         */
 169         function _clean_input_data($str)
 170         {
 171                 if (is_array($str))
 172                 {
 173                         $new_array = array();
 174                         foreach ($str as $key => $val)
 175                         {
 176                                 $new_array[$this->_clean_input_keys($key)] = $this->_clean_input_data($val);
 177                         }
 178                         return $new_array;
 179                 }
 180
 181                 // We strip slashes if magic quotes is on to keep things consistent
 182                 if (get_magic_quotes_gpc())
 183                 {
 184                         $str = stripslashes($str);
 185                 }
 186
 187                 // Should we filter the input data?
 188                 if ($this->use_xss_clean === TRUE)
 189                 {
 190                         $str = $this->xss_clean($str);
 191                 }
 192
 193                 // Standardize newlines
 194                 if (strpos($str, "\r") !== FALSE)
 195                 {
 196                         $str = str_replace(array("\r\n", "\r"), "\n", $str);
 197                 }
 198
 199                 return $str;
 200         }
 201
 202         // --------------------------------------------------------------------
 203
 204         /**
 205         * Clean Keys
 206         *
 207         * This is a helper function. To prevent malicious users
 208         * from trying to exploit keys we make sure that keys are
 209         * only named with alpha-numeric text and a few other items.
 210         *
 211         * @access       private
 212         * @param        string
 213         * @return       string
 214         */
 215         function _clean_input_keys($str)
 216         {
 217                 if ( ! preg_match("/^[a-z0-9:_\/-]+$/i", $str))
 218                 {
 219                         exit('Disallowed Key Characters.');
 220                 }
 221
 222                 return $str;
 223         }
 224
 225         // --------------------------------------------------------------------
 226
 227         /**
 228         * Fetch from array
 229         *
 230         * This is a helper function to retrieve values from global arrays
 231         *
 232         * @access       private
 233         * @param        array
 234         * @param        string
 235         * @param        bool
 236         * @return       string
 237         */
 238         function _fetch_from_array(&$array, $index = '', $xss_clean = FALSE)
 239         {
 240                 if ( ! isset($array[$index]))
 241                 {
 242                         return FALSE;
 243                 }
 244
 245                 if ($xss_clean === TRUE)
 246                 {
 247                         return $this->xss_clean($array[$index]);
 248                 }
 249
 250                 return $array[$index];
 251         }
 252
 253         // --------------------------------------------------------------------
 254
 255         /**
 256         * Fetch an item from the GET array
 257         *
 258         * @access       public
 259         * @param        string
 260         * @param        bool
 261         * @return       string
 262         */
 263         function get($index = '', $xss_clean = FALSE)
 264         {
 265                 return $this->_fetch_from_array($_GET, $index, $xss_clean);
 266         }
 267
 268         // --------------------------------------------------------------------
 269
 270         /**
 271         * Fetch an item from the POST array
 272         *
 273         * @access       public
 274         * @param        string
 275         * @param        bool
 276         * @return       string
 277         */
 278         function post($index = '', $xss_clean = FALSE)
 279         {
 280                 return $this->_fetch_from_array($_POST, $index, $xss_clean);
 281         }
 282
 283         // --------------------------------------------------------------------
 284
 285         /**
 286         * Fetch an item from either the GET array or the POST
 287         *
 288         * @access       public
 289         * @param        string  The index key
 290         * @param        bool    XSS cleaning
 291         * @return       string
 292         */
 293         function get_post($index = '', $xss_clean = FALSE)
 294         {
 295                 if ( ! isset($_POST[$index]) )
 296                 {
 297                         return $this->get($index, $xss_clean);
 298                 }
 299                 else
 300                 {
 301                         return $this->post($index, $xss_clean);
 302                 }
 303         }
 304
 305         // --------------------------------------------------------------------
 306
 307         /**
 308         * Fetch an item from the COOKIE array
 309         *
 310         * @access       public
 311         * @param        string
 312         * @param        bool
 313         * @return       string
 314         */
 315         function cookie($index = '', $xss_clean = FALSE)
 316         {
 317                 return $this->_fetch_from_array($_COOKIE, $index, $xss_clean);
 318         }
 319
 320         // --------------------------------------------------------------------
 321
 322         /**
 323         * Fetch an item from the SERVER array
 324         *
 325         * @access       public
 326         * @param        string
 327         * @param        bool
 328         * @return       string
 329         */
 330         function server($index = '', $xss_clean = FALSE)
 331         {
 332                 return $this->_fetch_from_array($_SERVER, $index, $xss_clean);
 333         }
 334
 335         // --------------------------------------------------------------------
 336
 337         /**
 338         * Fetch the IP Address
 339         *
 340         * @access       public
 341         * @return       string
 342         */
 343         function ip_address()
 344         {
 345                 if ($this->ip_address !== FALSE)
 346                 {
 347                         return $this->ip_address;
 348                 }
 349
 350                 if (config_item('proxy_ips') != '' && $this->server('HTTP_X_FORWARDED_FOR') && $this->server('REMOTE_ADDR'))
 351                 {
 352                         $proxies = preg_split('/[\s,]/', config_item('proxy_ips'), -1, PREG_SPLIT_NO_EMPTY);
 353                         $proxies = is_array($proxies) ? $proxies : array($proxies);
 354
 355                         $this->ip_address = in_array($_SERVER['REMOTE_ADDR'], $proxies) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : $_SERVER['REMOTE_ADDR'];
 356                 }
 357                 elseif ($this->server('REMOTE_ADDR') AND $this->server('HTTP_CLIENT_IP'))
 358                 {
 359                         $this->ip_address = $_SERVER['HTTP_CLIENT_IP'];
 360                 }
 361                 elseif ($this->server('REMOTE_ADDR'))
 362                 {
 363                         $this->ip_address = $_SERVER['REMOTE_ADDR'];
 364                 }
 365                 elseif ($this->server('HTTP_CLIENT_IP'))
 366                 {
 367                         $this->ip_address = $_SERVER['HTTP_CLIENT_IP'];
 368                 }
 369                 elseif ($this->server('HTTP_X_FORWARDED_FOR'))
 370                 {
 371                         $this->ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
 372                 }
 373
 374                 if ($this->ip_address === FALSE)
 375                 {
 376                         $this->ip_address = '0.0.0.0';
 377                         return $this->ip_address;
 378                 }
 379
 380                 if (strstr($this->ip_address, ','))
 381                 {
 382                         $x = explode(',', $this->ip_address);
 383                         $this->ip_address = trim(end($x));
 384                 }
 385
 386                 if ( ! $this->valid_ip($this->ip_address))
 387                 {
 388                         $this->ip_address = '0.0.0.0';
 389                 }
 390
 391                 return $this->ip_address;
 392         }
 393
 394         // --------------------------------------------------------------------
 395
 396         /**
 397         * Validate IP Address
 398         *
 399         * Updated version suggested by Geert De Deckere
 400         *
 401         * @access       public
 402         * @param        string
 403         * @return       string
 404         */
 405         function valid_ip($ip)
 406         {
 407                 $ip_segments = explode('.', $ip);
 408
 409                 // Always 4 segments needed
 410                 if (count($ip_segments) != 4)
 411                 {
 412                         return FALSE;
 413                 }
 414                 // IP can not start with 0
 415                 if ($ip_segments[0][0] == '0')
 416                 {
 417                         return FALSE;
 418                 }
 419                 // Check each segment
 420                 foreach ($ip_segments as $segment)
 421                 {
 422                         // IP segments must be digits and can not be
 423                         // longer than 3 digits or greater then 255
 424                         if ($segment == '' OR preg_match("/[^0-9]/", $segment) OR $segment > 255 OR strlen($segment) > 3)
 425                         {
 426                                 return FALSE;
 427                         }
 428                 }
 429
 430                 return TRUE;
 431         }
 432
 433         // --------------------------------------------------------------------
 434
 435         /**
 436         * User Agent
 437         *
 438         * @access       public
 439         * @return       string
 440         */
 441         function user_agent()
 442         {
 443                 if ($this->user_agent !== FALSE)
 444                 {
 445                         return $this->user_agent;
 446                 }
 447
 448                 $this->user_agent = ( ! isset($_SERVER['HTTP_USER_AGENT'])) ? FALSE : $_SERVER['HTTP_USER_AGENT'];
 449
 450                 return $this->user_agent;
 451         }
 452
 453         // --------------------------------------------------------------------
 454
 455         /**
 456         * Filename Security
 457         *
 458         * @access       public
 459         * @param        string
 460         * @return       string
 461         */
 462         function filename_security($str)
 463         {
 464                 $bad = array(
 465                                                 "../",
 466                                                 "./",
 467                                                 "<!--",
 468                                                 "-->",
 469                                                 "<",
 470                                                 ">",
 471                                                 "'",
 472                                                 '"',
 473                                                 '&',
 474                                                 '$',
 475                                                 '#',
 476                                                 '{',
 477                                                 '}',
 478                                                 '[',
 479                                                 ']',
 480                                                 '=',
 481                                                 ';',
 482                                                 '?',
 483                                                 "%20",
 484                                                 "%22",
 485                                                 "%3c",          // <
 486                                                 "%253c",        // <
 487                                                 "%3e",          // >
 488                                                 "%0e",          // >
 489                                                 "%28",          // (
 490                                                 "%29",          // )
 491                                                 "%2528",        // (
 492                                                 "%26",          // &
 493                                                 "%24",          // $
 494                                                 "%3f",          // ?
 495                                                 "%3b",          // ;
 496                                                 "%3d"           // =
 497                                         );
 498
 499                 return stripslashes(str_replace($bad, '', $str));
 500         }
 501
 502         // --------------------------------------------------------------------
 503
 504         /**
 505         * XSS Clean
 506         *
 507         * Sanitizes data so that Cross Site Scripting Hacks can be
 508         * prevented.  This function does a fair amount of work but
 509         * it is extremely thorough, designed to prevent even the
 510         * most obscure XSS attempts.  Nothing is ever 100% foolproof,
 511         * of course, but I haven't been able to get anything passed
 512         * the filter.
 513         *
 514         * Note: This function should only be used to deal with data
 515         * upon submission.  It's not something that should
 516         * be used for general runtime processing.
 517         *
 518         * This function was based in part on some code and ideas I
 519         * got from Bitflux: http://blog.bitflux.ch/wiki/XSS_Prevention
 520         *
 521         * To help develop this script I used this great list of
 522         * vulnerabilities along with a few other hacks I've
 523         * harvested from examining vulnerabilities in other programs:
 524         * http://ha.ckers.org/xss.html
 525         *
 526         * @access       public
 527         * @param        string
 528         * @return       string
 529         */
 530         function xss_clean($str, $is_image = FALSE)
 531         {
 532                 /*
 533                 * Is the string an array?
 534                 *
 535                 */
 536                 if (is_array($str))
 537                 {
 538                         while (list($key) = each($str))
 539                         {
 540                                 $str[$key] = $this->xss_clean($str[$key]);
 541                         }
 542
 543                         return $str;
 544                 }
 545
 546                 /*
 547                 * Remove Invisible Characters
 548                 */
 549                 $str = $this->_remove_invisible_characters($str);
 550
 551                 /*
 552                 * Protect GET variables in URLs
 553                 */
 554
 555                 // 901119URL5918AMP18930PROTECT8198
 556
 557                 $str = preg_replace('|\&([a-z\_0-9]+)\=([a-z\_0-9]+)|i', $this->xss_hash()."\\1=\\2", $str);
 558
 559                 /*
 560                 * Validate standard character entities
 561                 *
 562                 * Add a semicolon if missing.  We do this to enable
 563                 * the conversion of entities to ASCII later.
 564                 *
 565                 */
 566                 $str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);
 567
 568                 /*
 569                 * Validate UTF16 two byte encoding (x00)
 570                 *
 571                 * Just as above, adds a semicolon if missing.
 572                 *
 573                 */
 574                 $str = preg_replace('#(&\#x?)([0-9A-F]+);?#i',"\\1\\2;",$str);
 575
 576                 /*
 577                 * Un-Protect GET variables in URLs
 578                 */
 579                 $str = str_replace($this->xss_hash(), '&', $str);
 580
 581                 /*
 582                 * URL Decode
 583                 *
 584                 * Just in case stuff like this is submitted:
 585                 *
 586                 * <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
 587                 *
 588                 * Note: Use rawurldecode() so it does not remove plus signs
 589                 *
 590                 */
 591                 $str = rawurldecode($str);
 592
 593                 /*
 594                 * Convert character entities to ASCII
 595                 *
 596                 * This permits our tests below to work reliably.
 597                 * We only convert entities that are within tags since
 598                 * these are the ones that will pose security problems.
 599                 *
 600                 */
 601
 602                 $str = preg_replace_callback("/[a-z]+=([\'\"]).*?\\1/si", array($this, '_convert_attribute'), $str);
 603
 604                 $str = preg_replace_callback("/<\w+.*?(?=>|<|$)/si", array($this, '_html_entity_decode_callback'), $str);
 605
 606                 /*
 607                 * Remove Invisible Characters Again!
 608                 */
 609                 $str = $this->_remove_invisible_characters($str);
 610
 611                 /*
 612                 * Convert all tabs to spaces
 613                 *
 614                 * This prevents strings like this: ja   vascript
 615                 * NOTE: we deal with spaces between characters later.
 616                 * NOTE: preg_replace was found to be amazingly slow here on large blocks of data,
 617                 * so we use str_replace.
 618                 *
 619                 */
 620
 621                 if (strpos($str, "\t") !== FALSE)
 622                 {
 623                         $str = str_replace("\t", ' ', $str);
 624                 }
 625
 626                 /*
 627                 * Capture converted string for later comparison
 628                 */
 629                 $converted_string = $str;
 630
 631                 /*
 632                 * Not Allowed Under Any Conditions
 633                 */
 634
 635                 foreach ($this->never_allowed_str as $key => $val)
 636                 {
 637                         $str = str_replace($key, $val, $str);
 638                 }
 639
 640                 foreach ($this->never_allowed_regex as $key => $val)
 641                 {
 642                         $str = preg_replace("#".$key."#i", $val, $str);
 643                 }
 644
 645                 /*
 646                 * Makes PHP tags safe
 647                 *
 648                 *  Note: XML tags are inadvertently replaced too:
 649                 *
 650                 *       <?xml
 651                 *
 652                 * But it doesn't seem to pose a problem.
 653                 *
 654                 */
 655                 if ($is_image === TRUE)
 656                 {
 657                         // Images have a tendency to have the PHP short opening and closing tags every so often
 658                         // so we skip those and only do the long opening tags.
 659                         $str = preg_replace('/<\?(php)/i', "&lt;?\\1", $str);
 660                 }
 661                 else
 662                 {
 663                         $str = str_replace(array('<?', '?'.'>'),  array('&lt;?', '?&gt;'), $str);
 664                 }
 665
 666                 /*
 667                 * Compact any exploded words
 668                 *
 669                 * This corrects words like:  j a v a s c r i p t
 670                 * These words are compacted back to their correct state.
 671                 *
 672                 */
 673                 $words = array('javascript', 'expression', 'vbscript', 'script', 'applet', 'alert', 'document', 'write', 'cookie', 'window');
 674                 foreach ($words as $word)
 675                 {
 676                         $temp = '';
 677
 678                         for ($i = 0, $wordlen = strlen($word); $i < $wordlen; $i++)
 679                         {
 680                                 $temp .= substr($word, $i, 1)."\s*";
 681                         }
 682
 683                         // We only want to do this when it is followed by a non-word character
 684                         // That way valid stuff like "dealer to" does not become "dealerto"
 685                         $str = preg_replace_callback('#('.substr($temp, 0, -3).')(\W)#is', array($this, '_compact_exploded_words'), $str);
 686                 }
 687
 688                 /*
 689                 * Remove disallowed Javascript in links or img tags
 690                 * We used to do some version comparisons and use of stripos for PHP5, but it is dog slow compared
 691                 * to these simplified non-capturing preg_match(), especially if the pattern exists in the string
 692                 */
 693                 do
 694                 {
 695                         $original = $str;
 696
 697                         if (preg_match("/<a/i", $str))
 698                         {
 699                                 $str = preg_replace_callback("#<a\s+([^>]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
 700                         }
 701
 702                         if (preg_match("/<img/i", $str))
 703                         {
 704                                 $str = preg_replace_callback("#<img\s+([^>]*?)(\s?/?>|$)#si", array($this, '_js_img_removal'), $str);
 705                         }
 706
 707                         if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str))
 708                         {
 709                                 $str = preg_replace("#<(/*)(script|xss)(.*?)\>#si", '[removed]', $str);
 710                         }
 711                 }
 712                 while($original != $str);
 713
 714                 unset($original);
 715
 716                 /*
 717                 * Remove JavaScript Event Handlers
 718                 *
 719                 * Note: This code is a little blunt.  It removes
 720                 * the event handler and anything up to the closing >,
 721                 * but it's unlikely to be a problem.
 722                 *
 723                 */
 724                 $event_handlers = array('[^a-z_\-]on\w*','xmlns');
 725
 726                 if ($is_image === TRUE)
 727                 {
 728                         /*
 729                         * Adobe Photoshop puts XML metadata into JFIF images, including namespacing,
 730                         * so we have to allow this for images. -Paul
 731                         */
 732                         unset($event_handlers[array_search('xmlns', $event_handlers)]);
 733                 }
 734
 735                 $str = preg_replace("#<([^><]+?)(".implode('|', $event_handlers).")(\s*=\s*[^><]*)([><]*)#i", "<\\1\\4", $str);
 736
 737                 /*
 738                 * Sanitize naughty HTML elements
 739                 *
 740                 * If a tag containing any of the words in the list
 741                 * below is found, the tag gets converted to entities.
 742                 *
 743                 * So this: <blink>
 744                 * Becomes: &lt;blink&gt;
 745                 *
 746                 */
 747                 $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';
 748                 $str = preg_replace_callback('#<(/*\s*)('.$naughty.')([^><]*)([><]*)#is', array($this, '_sanitize_naughty_html'), $str);
 749
 750                 /*
 751                 * Sanitize naughty scripting elements
 752                 *
 753                 * Similar to above, only instead of looking for
 754                 * tags it looks for PHP and JavaScript commands
 755                 * that are disallowed.  Rather than removing the
 756                 * code, it simply converts the parenthesis to entities
 757                 * rendering the code un-executable.
 758                 *
 759                 * For example:  eval('some code')
 760                 * Becomes:              eval&#40;'some code'&#41;
 761                 *
 762                 */
 763                 $str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2&#40;\\3&#41;", $str);
 764
 765                 /*
 766                 * Final clean up
 767                 *
 768                 * This adds a bit of extra precaution in case
 769                 * something got through the above filters
 770                 *
 771                 */
 772                 foreach ($this->never_allowed_str as $key => $val)
 773                 {
 774                         $str = str_replace($key, $val, $str);
 775                 }
 776
 777                 foreach ($this->never_allowed_regex as $key => $val)
 778                 {
 779                         $str = preg_replace("#".$key."#i", $val, $str);
 780                 }
 781
 782                 /*
 783                 *  Images are Handled in a Special Way
 784                 *  - Essentially, we want to know that after all of the character conversion is done whether
 785                 *  any unwanted, likely XSS, code was found.  If not, we return TRUE, as the image is clean.
 786                 *  However, if the string post-conversion does not matched the string post-removal of XSS,
 787                 *  then it fails, as there was unwanted XSS code found and removed/changed during processing.
 788                 */
 789
 790                 if ($is_image === TRUE)
 791                 {
 792                         if ($str == $converted_string)
 793                         {
 794                                 return TRUE;
 795                         }
 796                         else
 797                         {
 798                                 return FALSE;
 799                         }
 800                 }
 801
 802                 log_message('debug', "XSS Filtering completed");
 803                 return $str;
 804         }
 805
 806         // --------------------------------------------------------------------
 807
 808         /**
 809         * Random Hash for protecting URLs
 810         *
 811         * @access       public
 812         * @return       string
 813         */
 814         function xss_hash()
 815         {
 816                 if ($this->xss_hash == '')
 817                 {
 818                         if (phpversion() >= 4.2)
 819                                 mt_srand();
 820                         else
 821                                 mt_srand(hexdec(substr(md5(microtime()), -8)) & 0x7fffffff);
 822
 823                         $this->xss_hash = md5(time() + mt_rand(0, 1999999999));
 824                 }
 825
 826                 return $this->xss_hash;
 827         }
 828
 829         // --------------------------------------------------------------------
 830
 831         /**
 832         * Remove Invisible Characters
 833         *
 834         * This prevents sandwiching null characters
 835         * between ascii characters, like Java\0script.
 836         *
 837         * @access       public
 838         * @param        string
 839         * @return       string
 840         */
 841         function _remove_invisible_characters($str)
 842         {
 843                 static $non_displayables;
 844
 845                 if ( ! isset($non_displayables))
 846                 {
 847                         // every control character except newline (dec 10), carriage return (dec 13), and horizontal tab (dec 09),
 848                         $non_displayables = array(
 849                                                                                 '/%0[0-8bcef]/',                        // url encoded 00-08, 11, 12, 14, 15
 850                                                                                 '/%1[0-9a-f]/',                         // url encoded 16-31
 851                                                                                 '/[\x00-\x08]/',                        // 00-08
 852                                                                                 '/\x0b/', '/\x0c/',                     // 11, 12
 853                                                                                 '/[\x0e-\x1f]/'                         // 14-31
 854                                                                         );
 855                 }
 856
 857                 do
 858                 {
 859                         $cleaned = $str;
 860                         $str = preg_replace($non_displayables, '', $str);
 861                 }
 862                 while ($cleaned != $str);
 863
 864                 return $str;
 865         }
 866
 867         // --------------------------------------------------------------------
 868
 869         /**
 870         * Compact Exploded Words
 871         *
 872         * Callback function for xss_clean() to remove whitespace from
 873         * things like j a v a s c r i p t
 874         *
 875         * @access       public
 876         * @param        type
 877         * @return       type
 878         */
 879         function _compact_exploded_words($matches)
 880         {
 881                 return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
 882         }
 883
 884         // --------------------------------------------------------------------
 885
 886         /**
 887         * Sanitize Naughty HTML
 888         *
 889         * Callback function for xss_clean() to remove naughty HTML elements
 890         *
 891         * @access       private
 892         * @param        array
 893         * @return       string
 894         */
 895         function _sanitize_naughty_html($matches)
 896         {
 897                 // encode opening brace
 898                 $str = '&lt;'.$matches[1].$matches[2].$matches[3];
 899
 900                 // encode captured opening or closing brace to prevent recursive vectors
 901                 $str .= str_replace(array('>', '<'), array('&gt;', '&lt;'), $matches[4]);
 902
 903                 return $str;
 904         }
 905
 906         // --------------------------------------------------------------------
 907
 908         /**
 909         * JS Link Removal
 910         *
 911         * Callback function for xss_clean() to sanitize links
 912         * This limits the PCRE backtracks, making it more performance friendly
 913         * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
 914         * PHP 5.2+ on link-heavy strings
 915         *
 916         * @access       private
 917         * @param        array
 918         * @return       string
 919         */
 920         function _js_link_removal($match)
 921         {
 922                 $attributes = $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]));
 923                 return str_replace($match[1], preg_replace("#href=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si", "", $attributes), $match[0]);
 924         }
 925
 926         /**
 927         * JS Image Removal
 928         *
 929         * Callback function for xss_clean() to sanitize image tags
 930         * This limits the PCRE backtracks, making it more performance friendly
 931         * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
 932         * PHP 5.2+ on image tag heavy strings
 933         *
 934         * @access       private
 935         * @param        array
 936         * @return       string
 937         */
 938         function _js_img_removal($match)
 939         {
 940                 $attributes = $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]));
 941                 return str_replace($match[1], preg_replace("#src=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si", "", $attributes), $match[0]);
 942         }
 943
 944         // --------------------------------------------------------------------
 945
 946         /**
 947         * Attribute Conversion
 948         *
 949         * Used as a callback for XSS Clean
 950         *
 951         * @access       public
 952         * @param        array
 953         * @return       string
 954         */
 955         function _convert_attribute($match)
 956         {
 957                 return str_replace(array('>', '<', '\\'), array('&gt;', '&lt;', '\\\\'), $match[0]);
 958         }
 959
 960         // --------------------------------------------------------------------
 961
 962         /**
 963         * HTML Entity Decode Callback
 964         *
 965         * Used as a callback for XSS Clean
 966         *
 967         * @access       public
 968         * @param        array
 969         * @return       string
 970         */
 971         function _html_entity_decode_callback($match)
 972         {
 973                 $CFG =& load_class('Config');
 974                 $charset = $CFG->item('charset');
 975
 976                 return $this->_html_entity_decode($match[0], strtoupper($charset));
 977         }
 978
 979         // --------------------------------------------------------------------
 980
 981         /**
 982         * HTML Entities Decode
 983         *
 984         * This function is a replacement for html_entity_decode()
 985         *
 986         * In some versions of PHP the native function does not work
 987         * when UTF-8 is the specified character set, so this gives us
 988         * a work-around.  More info here:
 989         * http://bugs.php.net/bug.php?id=25670
 990         *
 991         * @access       private
 992         * @param        string
 993         * @param        string
 994         * @return       string
 995         */
 996         /* -------------------------------------------------
 997         /*  Replacement for html_entity_decode()
 998         /* -------------------------------------------------*/
 999
1000         /*
1001         NOTE: html_entity_decode() has a bug in some PHP versions when UTF-8 is the
1002         character set, and the PHP developers said they were not back porting the
1003         fix to versions other than PHP 5.x.
1004         */
1005         function _html_entity_decode($str, $charset='UTF-8')
1006         {
1007                 if (stristr($str, '&') === FALSE) return $str;
1008
1009                 // The reason we are not using html_entity_decode() by itself is because
1010                 // while it is not technically correct to leave out the semicolon
1011                 // at the end of an entity most browsers will still interpret the entity
1012                 // correctly.  html_entity_decode() does not convert entities without
1013                 // semicolons, so we are left with our own little solution here. Bummer.
1014
1015                 if (function_exists('html_entity_decode') && (strtolower($charset) != 'utf-8' OR version_compare(phpversion(), '5.0.0', '>=')))
1016                 {
1017                         $str = html_entity_decode($str, ENT_COMPAT, $charset);
1018                         $str = preg_replace('~&#x(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);
1019                         return preg_replace('~&#([0-9]{2,4})~e', 'chr(\\1)', $str);
1020                 }
1021
1022                 // Numeric Entities
1023                 $str = preg_replace('~&#x(0*[0-9a-f]{2,5});{0,1}~ei', 'chr(hexdec("\\1"))', $str);
1024                 $str = preg_replace('~&#([0-9]{2,4});{0,1}~e', 'chr(\\1)', $str);
1025
1026                 // Literal Entities - Slightly slow so we do another check
1027                 if (stristr($str, '&') === FALSE)
1028                 {
1029                         $str = strtr($str, array_flip(get_html_translation_table(HTML_ENTITIES)));
1030                 }
1031
1032                 return $str;
1033         }
1034
1035         // --------------------------------------------------------------------
1036
1037         /**
1038         * Filter Attributes
1039         *
1040         * Filters tag attributes for consistency and safety
1041         *
1042         * @access       public
1043         * @param        string
1044         * @return       string
1045         */
1046         function _filter_attributes($str)
1047         {
1048                 $out = '';
1049
1050                 if (preg_match_all('#\s*[a-z\-]+\s*=\s*(\042|\047)([^\\1]*?)\\1#is', $str, $matches))
1051                 {
1052                         foreach ($matches[0] as $match)
1053                         {
1054                                 $out .= preg_replace("#/\*.*?\*/#s", '', $match);
1055                         }
1056                 }
1057
1058                 return $out;
1059         }
1060
1061         // --------------------------------------------------------------------
1062
1063 }
1064 // END Input class
1065
1066 /* End of file Input.php */
1067 /* Location: ./system/libraries/Input.php */