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