includes/Sanitizer.php

   1 <?php
   2 /**
   3  * XHTML sanitizer for MediaWiki
   4  *
   5  * Copyright © 2002-2005 Brion Vibber <brion@pobox.com> et al
   6  * http://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Parser
  25  */
  26
  27 /**
  28  * XHTML sanitizer for MediaWiki
  29  * @ingroup Parser
  30  */
  31 class Sanitizer {
  32         /**
  33          * Regular expression to match various types of character references in
  34          * Sanitizer::normalizeCharReferences and Sanitizer::decodeCharReferences
  35          */
  36         const CHAR_REFS_REGEX =
  37                 '/&([A-Za-z0-9\x80-\xff]+);
  38                  |&\#([0-9]+);
  39                  |&\#[xX]([0-9A-Fa-f]+);
  40                  |(&)/x';
  41
  42         /**
  43          * Blacklist for evil uris like javascript:
  44          * WARNING: DO NOT use this in any place that actually requires blacklisting
  45          * for security reasons. There are NUMEROUS[1] ways to bypass blacklisting, the
  46          * only way to be secure from javascript: uri based xss vectors is to whitelist
  47          * things that you know are safe and deny everything else.
  48          * [1]: http://ha.ckers.org/xss.html
  49          */
  50         const EVIL_URI_PATTERN = '!(^|\s|\*/\s*)(javascript|vbscript)([^\w]|$)!i';
  51         const XMLNS_ATTRIBUTE_PATTERN = "/^xmlns:[:A-Z_a-z-.0-9]+$/";
  52
  53         /**
  54          * List of all named character entities defined in HTML 4.01
  55          * http://www.w3.org/TR/html4/sgml/entities.html
  56          * As well as &apos; which is only defined starting in XHTML1.
  57          * @private
  58          */
  59         static $htmlEntities = array(
  60                 'Aacute'   => 193,
  61                 'aacute'   => 225,
  62                 'Acirc'    => 194,
  63                 'acirc'    => 226,
  64                 'acute'    => 180,
  65                 'AElig'    => 198,
  66                 'aelig'    => 230,
  67                 'Agrave'   => 192,
  68                 'agrave'   => 224,
  69                 'alefsym'  => 8501,
  70                 'Alpha'    => 913,
  71                 'alpha'    => 945,
  72                 'amp'      => 38,
  73                 'and'      => 8743,
  74                 'ang'      => 8736,
  75                 'apos'     => 39, // New in XHTML & HTML 5; avoid in output for compatibility with IE.
  76                 'Aring'    => 197,
  77                 'aring'    => 229,
  78                 'asymp'    => 8776,
  79                 'Atilde'   => 195,
  80                 'atilde'   => 227,
  81                 'Auml'     => 196,
  82                 'auml'     => 228,
  83                 'bdquo'    => 8222,
  84                 'Beta'     => 914,
  85                 'beta'     => 946,
  86                 'brvbar'   => 166,
  87                 'bull'     => 8226,
  88                 'cap'      => 8745,
  89                 'Ccedil'   => 199,
  90                 'ccedil'   => 231,
  91                 'cedil'    => 184,
  92                 'cent'     => 162,
  93                 'Chi'      => 935,
  94                 'chi'      => 967,
  95                 'circ'     => 710,
  96                 'clubs'    => 9827,
  97                 'cong'     => 8773,
  98                 'copy'     => 169,
  99                 'crarr'    => 8629,
 100                 'cup'      => 8746,
 101                 'curren'   => 164,
 102                 'dagger'   => 8224,
 103                 'Dagger'   => 8225,
 104                 'darr'     => 8595,
 105                 'dArr'     => 8659,
 106                 'deg'      => 176,
 107                 'Delta'    => 916,
 108                 'delta'    => 948,
 109                 'diams'    => 9830,
 110                 'divide'   => 247,
 111                 'Eacute'   => 201,
 112                 'eacute'   => 233,
 113                 'Ecirc'    => 202,
 114                 'ecirc'    => 234,
 115                 'Egrave'   => 200,
 116                 'egrave'   => 232,
 117                 'empty'    => 8709,
 118                 'emsp'     => 8195,
 119                 'ensp'     => 8194,
 120                 'Epsilon'  => 917,
 121                 'epsilon'  => 949,
 122                 'equiv'    => 8801,
 123                 'Eta'      => 919,
 124                 'eta'      => 951,
 125                 'ETH'      => 208,
 126                 'eth'      => 240,
 127                 'Euml'     => 203,
 128                 'euml'     => 235,
 129                 'euro'     => 8364,
 130                 'exist'    => 8707,
 131                 'fnof'     => 402,
 132                 'forall'   => 8704,
 133                 'frac12'   => 189,
 134                 'frac14'   => 188,
 135                 'frac34'   => 190,
 136                 'frasl'    => 8260,
 137                 'Gamma'    => 915,
 138                 'gamma'    => 947,
 139                 'ge'       => 8805,
 140                 'gt'       => 62,
 141                 'harr'     => 8596,
 142                 'hArr'     => 8660,
 143                 'hearts'   => 9829,
 144                 'hellip'   => 8230,
 145                 'Iacute'   => 205,
 146                 'iacute'   => 237,
 147                 'Icirc'    => 206,
 148                 'icirc'    => 238,
 149                 'iexcl'    => 161,
 150                 'Igrave'   => 204,
 151                 'igrave'   => 236,
 152                 'image'    => 8465,
 153                 'infin'    => 8734,
 154                 'int'      => 8747,
 155                 'Iota'     => 921,
 156                 'iota'     => 953,
 157                 'iquest'   => 191,
 158                 'isin'     => 8712,
 159                 'Iuml'     => 207,
 160                 'iuml'     => 239,
 161                 'Kappa'    => 922,
 162                 'kappa'    => 954,
 163                 'Lambda'   => 923,
 164                 'lambda'   => 955,
 165                 'lang'     => 9001,
 166                 'laquo'    => 171,
 167                 'larr'     => 8592,
 168                 'lArr'     => 8656,
 169                 'lceil'    => 8968,
 170                 'ldquo'    => 8220,
 171                 'le'       => 8804,
 172                 'lfloor'   => 8970,
 173                 'lowast'   => 8727,
 174                 'loz'      => 9674,
 175                 'lrm'      => 8206,
 176                 'lsaquo'   => 8249,
 177                 'lsquo'    => 8216,
 178                 'lt'       => 60,
 179                 'macr'     => 175,
 180                 'mdash'    => 8212,
 181                 'micro'    => 181,
 182                 'middot'   => 183,
 183                 'minus'    => 8722,
 184                 'Mu'       => 924,
 185                 'mu'       => 956,
 186                 'nabla'    => 8711,
 187                 'nbsp'     => 160,
 188                 'ndash'    => 8211,
 189                 'ne'       => 8800,
 190                 'ni'       => 8715,
 191                 'not'      => 172,
 192                 'notin'    => 8713,
 193                 'nsub'     => 8836,
 194                 'Ntilde'   => 209,
 195                 'ntilde'   => 241,
 196                 'Nu'       => 925,
 197                 'nu'       => 957,
 198                 'Oacute'   => 211,
 199                 'oacute'   => 243,
 200                 'Ocirc'    => 212,
 201                 'ocirc'    => 244,
 202                 'OElig'    => 338,
 203                 'oelig'    => 339,
 204                 'Ograve'   => 210,
 205                 'ograve'   => 242,
 206                 'oline'    => 8254,
 207                 'Omega'    => 937,
 208                 'omega'    => 969,
 209                 'Omicron'  => 927,
 210                 'omicron'  => 959,
 211                 'oplus'    => 8853,
 212                 'or'       => 8744,
 213                 'ordf'     => 170,
 214                 'ordm'     => 186,
 215                 'Oslash'   => 216,
 216                 'oslash'   => 248,
 217                 'Otilde'   => 213,
 218                 'otilde'   => 245,
 219                 'otimes'   => 8855,
 220                 'Ouml'     => 214,
 221                 'ouml'     => 246,
 222                 'para'     => 182,
 223                 'part'     => 8706,
 224                 'permil'   => 8240,
 225                 'perp'     => 8869,
 226                 'Phi'      => 934,
 227                 'phi'      => 966,
 228                 'Pi'       => 928,
 229                 'pi'       => 960,
 230                 'piv'      => 982,
 231                 'plusmn'   => 177,
 232                 'pound'    => 163,
 233                 'prime'    => 8242,
 234                 'Prime'    => 8243,
 235                 'prod'     => 8719,
 236                 'prop'     => 8733,
 237                 'Psi'      => 936,
 238                 'psi'      => 968,
 239                 'quot'     => 34,
 240                 'radic'    => 8730,
 241                 'rang'     => 9002,
 242                 'raquo'    => 187,
 243                 'rarr'     => 8594,
 244                 'rArr'     => 8658,
 245                 'rceil'    => 8969,
 246                 'rdquo'    => 8221,
 247                 'real'     => 8476,
 248                 'reg'      => 174,
 249                 'rfloor'   => 8971,
 250                 'Rho'      => 929,
 251                 'rho'      => 961,
 252                 'rlm'      => 8207,
 253                 'rsaquo'   => 8250,
 254                 'rsquo'    => 8217,
 255                 'sbquo'    => 8218,
 256                 'Scaron'   => 352,
 257                 'scaron'   => 353,
 258                 'sdot'     => 8901,
 259                 'sect'     => 167,
 260                 'shy'      => 173,
 261                 'Sigma'    => 931,
 262                 'sigma'    => 963,
 263                 'sigmaf'   => 962,
 264                 'sim'      => 8764,
 265                 'spades'   => 9824,
 266                 'sub'      => 8834,
 267                 'sube'     => 8838,
 268                 'sum'      => 8721,
 269                 'sup'      => 8835,
 270                 'sup1'     => 185,
 271                 'sup2'     => 178,
 272                 'sup3'     => 179,
 273                 'supe'     => 8839,
 274                 'szlig'    => 223,
 275                 'Tau'      => 932,
 276                 'tau'      => 964,
 277                 'there4'   => 8756,
 278                 'Theta'    => 920,
 279                 'theta'    => 952,
 280                 'thetasym' => 977,
 281                 'thinsp'   => 8201,
 282                 'THORN'    => 222,
 283                 'thorn'    => 254,
 284                 'tilde'    => 732,
 285                 'times'    => 215,
 286                 'trade'    => 8482,
 287                 'Uacute'   => 218,
 288                 'uacute'   => 250,
 289                 'uarr'     => 8593,
 290                 'uArr'     => 8657,
 291                 'Ucirc'    => 219,
 292                 'ucirc'    => 251,
 293                 'Ugrave'   => 217,
 294                 'ugrave'   => 249,
 295                 'uml'      => 168,
 296                 'upsih'    => 978,
 297                 'Upsilon'  => 933,
 298                 'upsilon'  => 965,
 299                 'Uuml'     => 220,
 300                 'uuml'     => 252,
 301                 'weierp'   => 8472,
 302                 'Xi'       => 926,
 303                 'xi'       => 958,
 304                 'Yacute'   => 221,
 305                 'yacute'   => 253,
 306                 'yen'      => 165,
 307                 'Yuml'     => 376,
 308                 'yuml'     => 255,
 309                 'Zeta'     => 918,
 310                 'zeta'     => 950,
 311                 'zwj'      => 8205,
 312                 'zwnj'     => 8204
 313         );
 314
 315         /**
 316          * Character entity aliases accepted by MediaWiki
 317          */
 318         static $htmlEntityAliases = array(
 319                 'רלמ' => 'rlm',
 320                 'رلم' => 'rlm',
 321         );
 322
 323         /**
 324          * Lazy-initialised attributes regex, see getAttribsRegex()
 325          */
 326         static $attribsRegex;
 327
 328         /**
 329          * Regular expression to match HTML/XML attribute pairs within a tag.
 330          * Allows some... latitude.
 331          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 332          */
 333         static function getAttribsRegex() {
 334                 if ( self::$attribsRegex === null ) {
 335                         $attribFirst = '[:A-Z_a-z0-9]';
 336                         $attrib = '[:A-Z_a-z-.0-9]';
 337                         $space = '[\x09\x0a\x0d\x20]';
 338                         self::$attribsRegex =
 339                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 340                                   ($space*=$space*
 341                                         (?:
 342                                          # The attribute value: quoted or alone
 343                                           \"([^<\"]*)\"
 344                                          | '([^<']*)'
 345                                          |  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)
 346                                          |  (\#[0-9a-fA-F]+) # Technically wrong, but lots of
 347                                                                                  # colors are specified like this.
 348                                                                                  # We'll be normalizing it.
 349                                         )
 350                                 )?(?=$space|\$)/sx";
 351                 }
 352                 return self::$attribsRegex;
 353         }
 354
 355         /**
 356          * Cleans up HTML, removes dangerous tags and attributes, and
 357          * removes HTML comments
 358          * @private
 359          * @param $text String
 360          * @param $processCallback Callback to do any variable or parameter replacements in HTML attribute values
 361          * @param $args Array for the processing callback
 362          * @param $extratags Array for any extra tags to include
 363          * @param $removetags Array for any tags (default or extra) to exclude
 364          * @return string
 365          */
 366         static function removeHTMLtags( $text, $processCallback = null, $args = array(), $extratags = array(), $removetags = array() ) {
 367                 global $wgUseTidy;
 368
 369                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 370                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 371
 372                 wfProfileIn( __METHOD__ );
 373
 374                 if ( !$staticInitialised ) {
 375
 376                         $htmlpairsStatic = array( # Tags that must be closed
 377                                 'b', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 378                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 379                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 380                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 381                                 'ruby', 'rt' , 'rb' , 'rp', 'p', 'span', 'abbr', 'dfn',
 382                                 'kbd', 'samp', 'thead', 'tbody', 'tfoot'
 383                         );
 384                         $htmlsingle = array(
 385                                 'br', 'hr', 'li', 'dt', 'dd'
 386                         );
 387                         $htmlsingleonly = array( # Elements that cannot have close tags
 388                                 'br', 'hr'
 389                         );
 390                         $htmlnest = array( # Tags that can be nested--??
 391                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 392                                 'dl', 'font', 'big', 'small', 'sub', 'sup', 'span'
 393                         );
 394                         $tabletags = array( # Can only appear inside table, we will close them
 395                                 'td', 'th', 'tr',
 396                         );
 397                         $htmllist = array( # Tags used by list
 398                                 'ul','ol',
 399                         );
 400                         $listtags = array( # Tags that can appear in a list
 401                                 'li',
 402                         );
 403
 404                         global $wgAllowImageTag;
 405                         if ( $wgAllowImageTag ) {
 406                                 $htmlsingle[] = 'img';
 407                                 $htmlsingleonly[] = 'img';
 408                         }
 409
 410                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 411                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 412
 413                         # Convert them all to hashtables for faster lookup
 414                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 415                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 416                         foreach ( $vars as $var ) {
 417                                 $$var = array_flip( $$var );
 418                         }
 419                         $staticInitialised = true;
 420                 }
 421                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 422                 $extratags = array_flip( $extratags );
 423                 $removetags = array_flip( $removetags );
 424                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 425                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ) , $removetags );
 426
 427                 # Remove HTML comments
 428                 $text = Sanitizer::removeHTMLcomments( $text );
 429                 $bits = explode( '<', $text );
 430                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 431                 if ( !$wgUseTidy ) {
 432                         $tagstack = $tablestack = array();
 433                         foreach ( $bits as $x ) {
 434                                 $regs = array();
 435                                 # $slash: Does the current element start with a '/'?
 436                                 # $t: Current element name
 437                                 # $params: String between element name and >
 438                                 # $brace: Ending '>' or '/>'
 439                                 # $rest: Everything until the next element of $bits
 440                                 if( preg_match( '!^(/?)(\\w+)([^>]*?)(/{0,1}>)([^<]*)$!', $x, $regs ) ) {
 441                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 442                                 } else {
 443                                         $slash = $t = $params = $brace = $rest = null;
 444                                 }
 445
 446                                 $badtag = false;
 447                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 448                                         # Check our stack
 449                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 450                                                 $badtag = true;
 451                                         } elseif ( $slash ) {
 452                                                 # Closing a tag... is it the one we just opened?
 453                                                 $ot = @array_pop( $tagstack );
 454                                                 if ( $ot != $t ) {
 455                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 456                                                                 # Pop all elements with an optional close tag
 457                                                                 # and see if we find a match below them
 458                                                                 $optstack = array();
 459                                                                 array_push( $optstack, $ot );
 460                                                                 $ot = @array_pop( $tagstack );
 461                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 462                                                                         array_push( $optstack, $ot );
 463                                                                         $ot = @array_pop( $tagstack );
 464                                                                 }
 465                                                                 if ( $t != $ot ) {
 466                                                                         # No match. Push the optional elements back again
 467                                                                         $badtag = true;
 468                                                                         while ( $ot = @array_pop( $optstack ) ) {
 469                                                                                 array_push( $tagstack, $ot );
 470                                                                         }
 471                                                                 }
 472                                                         } else {
 473                                                                 @array_push( $tagstack, $ot );
 474                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 475                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 476                                                                         $badtag = true;
 477                                                                 }
 478                                                         }
 479                                                 } else {
 480                                                         if ( $t == 'table' ) {
 481                                                                 $tagstack = array_pop( $tablestack );
 482                                                         }
 483                                                 }
 484                                                 $newparams = '';
 485                                         } else {
 486                                                 # Keep track for later
 487                                                 if ( isset( $tabletags[$t] ) &&
 488                                                 !in_array( 'table', $tagstack ) ) {
 489                                                         $badtag = true;
 490                                                 } elseif ( in_array( $t, $tagstack ) &&
 491                                                 !isset( $htmlnest [$t ] ) ) {
 492                                                         $badtag = true;
 493                                                 # Is it a self closed htmlpair ? (bug 5487)
 494                                                 } elseif ( $brace == '/>' &&
 495                                                 isset( $htmlpairs[$t] ) ) {
 496                                                         $badtag = true;
 497                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 498                                                         # Hack to force empty tag for uncloseable elements
 499                                                         $brace = '/>';
 500                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 501                                                         # Hack to not close $htmlsingle tags
 502                                                         $brace = null;
 503                                                 } elseif ( isset( $tabletags[$t] )
 504                                                 && in_array( $t, $tagstack ) ) {
 505                                                         // New table tag but forgot to close the previous one
 506                                                         $text .= "</$t>";
 507                                                 } else {
 508                                                         if ( $t == 'table' ) {
 509                                                                 array_push( $tablestack, $tagstack );
 510                                                                 $tagstack = array();
 511                                                         }
 512                                                         array_push( $tagstack, $t );
 513                                                 }
 514
 515                                                 # Replace any variables or template parameters with
 516                                                 # plaintext results.
 517                                                 if( is_callable( $processCallback ) ) {
 518                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 519                                                 }
 520
 521                                                 # Strip non-approved attributes from the tag
 522                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 523                                         }
 524                                         if ( !$badtag ) {
 525                                                 $rest = str_replace( '>', '&gt;', $rest );
 526                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 527                                                 $text .= "<$slash$t$newparams$close>$rest";
 528                                                 continue;
 529                                         }
 530                                 }
 531                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x);
 532                         }
 533                         # Close off any remaining tags
 534                         while ( is_array( $tagstack ) && ($t = array_pop( $tagstack )) ) {
 535                                 $text .= "</$t>\n";
 536                                 if ( $t == 'table' ) { $tagstack = array_pop( $tablestack ); }
 537                         }
 538                 } else {
 539                         # this might be possible using tidy itself
 540                         foreach ( $bits as $x ) {
 541                                 preg_match( '/^(\\/?)(\\w+)([^>]*?)(\\/{0,1}>)([^<]*)$/',
 542                                 $x, $regs );
 543                                 @list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 544                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 545                                         if( is_callable( $processCallback ) ) {
 546                                                 call_user_func_array( $processCallback, array( &$params, $args ) );
 547                                         }
 548                                         $newparams = Sanitizer::fixTagAttributes( $params, $t );
 549                                         $rest = str_replace( '>', '&gt;', $rest );
 550                                         $text .= "<$slash$t$newparams$brace$rest";
 551                                 } else {
 552                                         $text .= '&lt;' . str_replace( '>', '&gt;', $x);
 553                                 }
 554                         }
 555                 }
 556                 wfProfileOut( __METHOD__ );
 557                 return $text;
 558         }
 559
 560         /**
 561          * Remove '<!--', '-->', and everything between.
 562          * To avoid leaving blank lines, when a comment is both preceded
 563          * and followed by a newline (ignoring spaces), trim leading and
 564          * trailing spaces and one of the newlines.
 565          *
 566          * @private
 567          * @param $text String
 568          * @return string
 569          */
 570         static function removeHTMLcomments( $text ) {
 571                 wfProfileIn( __METHOD__ );
 572                 while (($start = strpos($text, '<!--')) !== false) {
 573                         $end = strpos($text, '-->', $start + 4);
 574                         if ($end === false) {
 575                                 # Unterminated comment; bail out
 576                                 break;
 577                         }
 578
 579                         $end += 3;
 580
 581                         # Trim space and newline if the comment is both
 582                         # preceded and followed by a newline
 583                         $spaceStart = max($start - 1, 0);
 584                         $spaceLen = $end - $spaceStart;
 585                         while (substr($text, $spaceStart, 1) === ' ' && $spaceStart > 0) {
 586                                 $spaceStart--;
 587                                 $spaceLen++;
 588                         }
 589                         while (substr($text, $spaceStart + $spaceLen, 1) === ' ')
 590                                 $spaceLen++;
 591                         if (substr($text, $spaceStart, 1) === "\n" and substr($text, $spaceStart + $spaceLen, 1) === "\n") {
 592                                 # Remove the comment, leading and trailing
 593                                 # spaces, and leave only one newline.
 594                                 $text = substr_replace($text, "\n", $spaceStart, $spaceLen + 1);
 595                         }
 596                         else {
 597                                 # Remove just the comment.
 598                                 $text = substr_replace($text, '', $start, $end - $start);
 599                         }
 600                 }
 601                 wfProfileOut( __METHOD__ );
 602                 return $text;
 603         }
 604
 605         /**
 606          * Take an array of attribute names and values and normalize or discard
 607          * illegal values for the given element type.
 608          *
 609          * - Discards attributes not on a whitelist for the given element
 610          * - Unsafe style attributes are discarded
 611          * - Invalid id attributes are reencoded
 612          *
 613          * @param $attribs Array
 614          * @param $element String
 615          * @return Array
 616          *
 617          * @todo Check for legal values where the DTD limits things.
 618          * @todo Check for unique id attribute :P
 619          */
 620         static function validateTagAttributes( $attribs, $element ) {
 621                 return Sanitizer::validateAttributes( $attribs,
 622                         Sanitizer::attributeWhitelist( $element ) );
 623         }
 624
 625         /**
 626          * Take an array of attribute names and values and normalize or discard
 627          * illegal values for the given whitelist.
 628          *
 629          * - Discards attributes not the given whitelist
 630          * - Unsafe style attributes are discarded
 631          * - Invalid id attributes are reencoded
 632          *
 633          * @param $attribs Array
 634          * @param $whitelist Array: list of allowed attribute names
 635          * @return Array
 636          *
 637          * @todo Check for legal values where the DTD limits things.
 638          * @todo Check for unique id attribute :P
 639          */
 640         static function validateAttributes( $attribs, $whitelist ) {
 641                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes, $wgHtml5;
 642
 643                 $whitelist = array_flip( $whitelist );
 644                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 645
 646                 $out = array();
 647                 foreach( $attribs as $attribute => $value ) {
 648                         #allow XML namespace declaration if RDFa is enabled
 649                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 650                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 651                                         $out[$attribute] = $value;
 652                                 }
 653
 654                                 continue;
 655                         }
 656
 657                         # Allow any attribute beginning with "data-", if in HTML5 mode
 658                         if ( !($wgHtml5 && preg_match( '/^data-/i', $attribute )) && !isset( $whitelist[$attribute] ) ) {
 659                                 continue;
 660                         }
 661
 662                         # Strip javascript "expression" from stylesheets.
 663                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 664                         if( $attribute == 'style' ) {
 665                                 $value = Sanitizer::checkCss( $value );
 666                         }
 667
 668                         if ( $attribute === 'id' ) {
 669                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 670                         }
 671
 672                         //RDFa and microdata properties allow URLs, URIs and/or CURIs. check them for sanity
 673                         if ( $attribute === 'rel' || $attribute === 'rev' ||
 674                                 $attribute === 'about' || $attribute === 'property' || $attribute === 'resource' || #RDFa
 675                                 $attribute === 'datatype' || $attribute === 'typeof' ||                             #RDFa
 676                                 $attribute === 'itemid' || $attribute === 'itemprop' || $attribute === 'itemref' || #HTML5 microdata
 677                                 $attribute === 'itemscope' || $attribute === 'itemtype' ) {                         #HTML5 microdata
 678
 679                                 //Paranoia. Allow "simple" values but suppress javascript
 680                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 681                                         continue;
 682                                 }
 683                         }
 684
 685                         # NOTE: even though elements using href/src are not allowed directly, supply
 686                         #       validation code that can be used by tag hook handlers, etc
 687                         if ( $attribute === 'href' || $attribute === 'src' ) {
 688                                 if ( !preg_match( $hrefExp, $value ) ) {
 689                                         continue; //drop any href or src attributes not using an allowed protocol.
 690                                                   //NOTE: this also drops all relative URLs
 691                                 }
 692                         }
 693
 694                         // If this attribute was previously set, override it.
 695                         // Output should only have one attribute of each name.
 696                         $out[$attribute] = $value;
 697                 }
 698
 699                 if ( $wgAllowMicrodataAttributes ) {
 700                         # itemtype, itemid, itemref don't make sense without itemscope
 701                         if ( !array_key_exists( 'itemscope', $out ) ) {
 702                                 unset( $out['itemtype'] );
 703                                 unset( $out['itemid'] );
 704                                 unset( $out['itemref'] );
 705                         }
 706                         # TODO: Strip itemprop if we aren't descendants of an itemscope.
 707                 }
 708                 return $out;
 709         }
 710
 711         /**
 712          * Merge two sets of HTML attributes.  Conflicting items in the second set
 713          * will override those in the first, except for 'class' attributes which
 714          * will be combined (if they're both strings).
 715          *
 716          * @todo implement merging for other attributes such as style
 717          * @param $a Array
 718          * @param $b Array
 719          * @return array
 720          */
 721         static function mergeAttributes( $a, $b ) {
 722                 $out = array_merge( $a, $b );
 723                 if( isset( $a['class'] ) && isset( $b['class'] )
 724                 && is_string( $a['class'] ) && is_string( $b['class'] )
 725                 && $a['class'] !== $b['class'] ) {
 726                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 727                                 -1, PREG_SPLIT_NO_EMPTY );
 728                         $out['class'] = implode( ' ', array_unique( $classes ) );
 729                 }
 730                 return $out;
 731         }
 732
 733         /**
 734          * Pick apart some CSS and check it for forbidden or unsafe structures.
 735          * Returns a sanitized string. This sanitized string will have
 736          * character references and escape sequences decoded, and comments
 737          * stripped. If the input is just too evil, only a comment complaining
 738          * about evilness will be returned.
 739          *
 740          * Currently URL references, 'expression', 'tps' are forbidden.
 741          *
 742          * NOTE: Despite the fact that character references are decoded, the
 743          * returned string may contain character references given certain
 744          * clever input strings. These character references must
 745          * be escaped before the return value is embedded in HTML.
 746          *
 747          * @param $value String
 748          * @return String
 749          */
 750         static function checkCss( $value ) {
 751                 // Decode character references like &#123;
 752                 $value = Sanitizer::decodeCharReferences( $value );
 753
 754                 // Decode escape sequences and line continuation
 755                 // See the grammar in the CSS 2 spec, appendix D.
 756                 // This has to be done AFTER decoding character references.
 757                 // This means it isn't possible for this function to return
 758                 // unsanitized escape sequences. It is possible to manufacture
 759                 // input that contains character references that decode to
 760                 // escape sequences that decode to character references, but
 761                 // it's OK for the return value to contain character references
 762                 // because the caller is supposed to escape those anyway.
 763                 static $decodeRegex;
 764                 if ( !$decodeRegex ) {
 765                         $space = '[\\x20\\t\\r\\n\\f]';
 766                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 767                         $backslash = '\\\\';
 768                         $decodeRegex = "/ $backslash
 769                                 (?:
 770                                         ($nl) |  # 1. Line continuation
 771                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 772                                         (.) | # 3. backslash cancelling special meaning
 773                                         () | # 4. backslash at end of string
 774                                 )/xu";
 775                 }
 776                 $value = preg_replace_callback( $decodeRegex,
 777                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 778
 779                 // Remove any comments; IE gets token splitting wrong
 780                 // This must be done AFTER decoding character references and
 781                 // escape sequences, because those steps can introduce comments
 782                 // This step cannot introduce character references or escape
 783                 // sequences, because it replaces comments with spaces rather
 784                 // than removing them completely.
 785                 $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 786
 787                 // Remove anything after a comment-start token, to guard against
 788                 // incorrect client implementations.
 789                 $commentPos = strpos( $value, '/*' );
 790                 if ( $commentPos !== false ) {
 791                         $value = substr( $value, 0, $commentPos );
 792                 }
 793
 794                 // Reject problematic keywords and control characters
 795                 if ( preg_match( '/[\000-\010\016-\037\177]/', $value ) ) {
 796                         return '/* invalid control char */';
 797                 } elseif ( preg_match( '! expression | filter\s*: | accelerator\s*: | url\s*\( !ix', $value ) ) {
 798                         return '/* insecure input */';
 799                 }
 800                 return $value;
 801         }
 802
 803         /**
 804          * @param $matches array
 805          * @return String
 806          */
 807         static function cssDecodeCallback( $matches ) {
 808                 if ( $matches[1] !== '' ) {
 809                         // Line continuation
 810                         return '';
 811                 } elseif ( $matches[2] !== '' ) {
 812                         $char = codepointToUtf8( hexdec( $matches[2] ) );
 813                 } elseif ( $matches[3] !== '' ) {
 814                         $char = $matches[3];
 815                 } else {
 816                         $char = '\\';
 817                 }
 818                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
 819                         // These characters need to be escaped in strings
 820                         // Clean up the escape sequence to avoid parsing errors by clients
 821                         return '\\' . dechex( ord( $char ) ) . ' ';
 822                 } else {
 823                         // Decode unnecessary escape
 824                         return $char;
 825                 }
 826         }
 827
 828         /**
 829          * Take a tag soup fragment listing an HTML element's attributes
 830          * and normalize it to well-formed XML, discarding unwanted attributes.
 831          * Output is safe for further wikitext processing, with escaping of
 832          * values that could trigger problems.
 833          *
 834          * - Normalizes attribute names to lowercase
 835          * - Discards attributes not on a whitelist for the given element
 836          * - Turns broken or invalid entities into plaintext
 837          * - Double-quotes all attribute values
 838          * - Attributes without values are given the name as attribute
 839          * - Double attributes are discarded
 840          * - Unsafe style attributes are discarded
 841          * - Prepends space if there are attributes.
 842          *
 843          * @param $text String
 844          * @param $element String
 845          * @return String
 846          */
 847         static function fixTagAttributes( $text, $element ) {
 848                 if( trim( $text ) == '' ) {
 849                         return '';
 850                 }
 851
 852                 $stripped = Sanitizer::validateTagAttributes(
 853                         Sanitizer::decodeTagAttributes( $text ), $element );
 854
 855                 $attribs = array();
 856                 foreach( $stripped as $attribute => $value ) {
 857                         $encAttribute = htmlspecialchars( $attribute );
 858                         $encValue = Sanitizer::safeEncodeAttribute( $value );
 859
 860                         $attribs[] = "$encAttribute=\"$encValue\"";
 861                 }
 862                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
 863         }
 864
 865         /**
 866          * Encode an attribute value for HTML output.
 867          * @param $text String
 868          * @return HTML-encoded text fragment
 869          */
 870         static function encodeAttribute( $text ) {
 871                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
 872
 873                 // Whitespace is normalized during attribute decoding,
 874                 // so if we've been passed non-spaces we must encode them
 875                 // ahead of time or they won't be preserved.
 876                 $encValue = strtr( $encValue, array(
 877                         "\n" => '&#10;',
 878                         "\r" => '&#13;',
 879                         "\t" => '&#9;',
 880                 ) );
 881
 882                 return $encValue;
 883         }
 884
 885         /**
 886          * Encode an attribute value for HTML tags, with extra armoring
 887          * against further wiki processing.
 888          * @param $text String
 889          * @return HTML-encoded text fragment
 890          */
 891         static function safeEncodeAttribute( $text ) {
 892                 $encValue = Sanitizer::encodeAttribute( $text );
 893
 894                 # Templates and links may be expanded in later parsing,
 895                 # creating invalid or dangerous output. Suppress this.
 896                 $encValue = strtr( $encValue, array(
 897                         '<'    => '&lt;',   // This should never happen,
 898                         '>'    => '&gt;',   // we've received invalid input
 899                         '"'    => '&quot;', // which should have been escaped.
 900                         '{'    => '&#123;',
 901                         '['    => '&#91;',
 902                         "''"   => '&#39;&#39;',
 903                         'ISBN' => '&#73;SBN',
 904                         'RFC'  => '&#82;FC',
 905                         'PMID' => '&#80;MID',
 906                         '|'    => '&#124;',
 907                         '__'   => '&#95;_',
 908                 ) );
 909
 910                 # Stupid hack
 911                 $encValue = preg_replace_callback(
 912                         '/(' . wfUrlProtocols() . ')/',
 913                         array( 'Sanitizer', 'armorLinksCallback' ),
 914                         $encValue );
 915                 return $encValue;
 916         }
 917
 918         /**
 919          * Given a value, escape it so that it can be used in an id attribute and
 920          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
 921          * true, allowing anything but ASCII whitespace.  Otherwise it will use
 922          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
 923          * escaped with lots of dots.
 924          *
 925          * To ensure we don't have to bother escaping anything, we also strip ', ",
 926          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
 927          * We also strip # because it upsets IE, and % because it could be
 928          * ambiguous if it's part of something that looks like a percent escape
 929          * (which don't work reliably in fragments cross-browser).
 930          *
 931          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
 932          *                                                          in the id and
 933          *                                                          name attributes
 934          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with the id attribute
 935          * @see http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#the-id-attribute
 936          *   HTML5 definition of id attribute
 937          *
 938          * @param $id String: id to escape
 939          * @param $options Mixed: string or array of strings (default is array()):
 940          *   'noninitial': This is a non-initial fragment of an id, not a full id,
 941          *       so don't pay attention if the first character isn't valid at the
 942          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
 943          *       false.
 944          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
 945          *       if $wgExperimentalHtmlIds is used, so we can generate extra
 946          *       anchors and links won't break.
 947          * @return String
 948          */
 949         static function escapeId( $id, $options = array() ) {
 950                 global $wgHtml5, $wgExperimentalHtmlIds;
 951                 $options = (array)$options;
 952
 953                 if ( $wgHtml5 && $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
 954                         $id = Sanitizer::decodeCharReferences( $id );
 955                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
 956                         $id = trim( $id, '_' );
 957                         if ( $id === '' ) {
 958                                 # Must have been all whitespace to start with.
 959                                 return '_';
 960                         } else {
 961                                 return $id;
 962                         }
 963                 }
 964
 965                 # HTML4-style escaping
 966                 static $replace = array(
 967                         '%3A' => ':',
 968                         '%' => '.'
 969                 );
 970
 971                 $id = urlencode( Sanitizer::decodeCharReferences( strtr( $id, ' ', '_' ) ) );
 972                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
 973
 974                 if ( !preg_match( '/^[a-zA-Z]/', $id )
 975                 && !in_array( 'noninitial', $options ) )  {
 976                         // Initial character must be a letter!
 977                         $id = "x$id";
 978                 }
 979                 return $id;
 980         }
 981
 982         /**
 983          * Given a value, escape it so that it can be used as a CSS class and
 984          * return it.
 985          *
 986          * @todo For extra validity, input should be validated UTF-8.
 987          *
 988          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
 989          *
 990          * @param $class String
 991          * @return String
 992          */
 993         static function escapeClass( $class ) {
 994                 // Convert ugly stuff to underscores and kill underscores in ugly places
 995                 return rtrim(preg_replace(
 996                         array('/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/','/_+/'),
 997                         '_',
 998                         $class ), '_');
 999         }
1000
1001         /**
1002          * Given HTML input, escape with htmlspecialchars but un-escape entites.
1003          * This allows (generally harmless) entities like &#160; to survive.
1004          *
1005          * @param $html String to escape
1006          * @return String: escaped input
1007          */
1008         static function escapeHtmlAllowEntities( $html ) {
1009                 $html = Sanitizer::decodeCharReferences( $html );
1010                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1011                 # hurt.
1012                 $html = htmlspecialchars( $html, ENT_QUOTES );
1013                 return $html;
1014         }
1015
1016         /**
1017          * Regex replace callback for armoring links against further processing.
1018          * @param $matches Array
1019          * @return string
1020          */
1021         private static function armorLinksCallback( $matches ) {
1022                 return str_replace( ':', '&#58;', $matches[1] );
1023         }
1024
1025         /**
1026          * Return an associative array of attribute names and values from
1027          * a partial tag string. Attribute names are forces to lowercase,
1028          * character references are decoded to UTF-8 text.
1029          *
1030          * @param $text String
1031          * @return Array
1032          */
1033         public static function decodeTagAttributes( $text ) {
1034                 if( trim( $text ) == '' ) {
1035                         return array();
1036                 }
1037
1038                 $attribs = array();
1039                 $pairs = array();
1040                 if( !preg_match_all(
1041                         self::getAttribsRegex(),
1042                         $text,
1043                         $pairs,
1044                         PREG_SET_ORDER ) ) {
1045                         return $attribs;
1046                 }
1047
1048                 foreach( $pairs as $set ) {
1049                         $attribute = strtolower( $set[1] );
1050                         $value = Sanitizer::getTagAttributeCallback( $set );
1051
1052                         // Normalize whitespace
1053                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1054                         $value = trim( $value );
1055
1056                         // Decode character references
1057                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1058                 }
1059                 return $attribs;
1060         }
1061
1062         /**
1063          * Pick the appropriate attribute value from a match set from the
1064          * attribs regex matches.
1065          *
1066          * @param $set Array
1067          * @return String
1068          */
1069         private static function getTagAttributeCallback( $set ) {
1070                 if( isset( $set[6] ) ) {
1071                         # Illegal #XXXXXX color with no quotes.
1072                         return $set[6];
1073                 } elseif( isset( $set[5] ) ) {
1074                         # No quotes.
1075                         return $set[5];
1076                 } elseif( isset( $set[4] ) ) {
1077                         # Single-quoted
1078                         return $set[4];
1079                 } elseif( isset( $set[3] ) ) {
1080                         # Double-quoted
1081                         return $set[3];
1082                 } elseif( !isset( $set[2] ) ) {
1083                         # In XHTML, attributes must have a value.
1084                         # For 'reduced' form, return explicitly the attribute name here.
1085                         return $set[1];
1086                 } else {
1087                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1088                 }
1089         }
1090
1091         /**
1092          * Normalize whitespace and character references in an XML source-
1093          * encoded text for an attribute value.
1094          *
1095          * See http://www.w3.org/TR/REC-xml/#AVNormalize for background,
1096          * but note that we're not returning the value, but are returning
1097          * XML source fragments that will be slapped into output.
1098          *
1099          * @param $text String
1100          * @return String
1101          */
1102         private static function normalizeAttributeValue( $text ) {
1103                 return str_replace( '"', '&quot;',
1104                         self::normalizeWhitespace(
1105                                 Sanitizer::normalizeCharReferences( $text ) ) );
1106         }
1107
1108         /**
1109          * @param $text string
1110          * @return mixed
1111          */
1112         private static function normalizeWhitespace( $text ) {
1113                 return preg_replace(
1114                         '/\r\n|[\x20\x0d\x0a\x09]/',
1115                         ' ',
1116                         $text );
1117         }
1118
1119         /**
1120          * Normalizes whitespace in a section name, such as might be returned
1121          * by Parser::stripSectionName(), for use in the id's that are used for
1122          * section links.
1123          *
1124          * @param $section String
1125          * @return String
1126          */
1127         static function normalizeSectionNameWhitespace( $section ) {
1128                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1129         }
1130
1131         /**
1132          * Ensure that any entities and character references are legal
1133          * for XML and XHTML specifically. Any stray bits will be
1134          * &amp;-escaped to result in a valid text fragment.
1135          *
1136          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1137          *   numericized (this way we're well-formed even without a DTD)
1138          * b. any numeric char refs must be legal chars, not invalid or forbidden
1139          * c. use &#x, not &#X
1140          * d. fix or reject non-valid attributes
1141          *
1142          * @param $text String
1143          * @return String
1144          * @private
1145          */
1146         static function normalizeCharReferences( $text ) {
1147                 return preg_replace_callback(
1148                         self::CHAR_REFS_REGEX,
1149                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1150                         $text );
1151         }
1152         /**
1153          * @param $matches String
1154          * @return String
1155          */
1156         static function normalizeCharReferencesCallback( $matches ) {
1157                 $ret = null;
1158                 if( $matches[1] != '' ) {
1159                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1160                 } elseif( $matches[2] != '' ) {
1161                         $ret = Sanitizer::decCharReference( $matches[2] );
1162                 } elseif( $matches[3] != ''  ) {
1163                         $ret = Sanitizer::hexCharReference( $matches[3] );
1164                 }
1165                 if( is_null( $ret ) ) {
1166                         return htmlspecialchars( $matches[0] );
1167                 } else {
1168                         return $ret;
1169                 }
1170         }
1171
1172         /**
1173          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1174          * return the equivalent numeric entity reference (except for the core &lt;
1175          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1176          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1177          * pseudo-entity source (eg &amp;foo;)
1178          *
1179          * @param $name String
1180          * @return String
1181          */
1182         static function normalizeEntity( $name ) {
1183                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1184                         return '&' . self::$htmlEntityAliases[$name] . ';';
1185                 } elseif ( in_array( $name,
1186                 array( 'lt', 'gt', 'amp', 'quot' ) ) ) {
1187                         return "&$name;";
1188                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1189                         return '&#' . self::$htmlEntities[$name] . ';';
1190                 } else {
1191                         return "&amp;$name;";
1192                 }
1193         }
1194
1195         /**
1196          * @param $codepoint
1197          * @return null|string
1198          */
1199         static function decCharReference( $codepoint ) {
1200                 $point = intval( $codepoint );
1201                 if( Sanitizer::validateCodepoint( $point ) ) {
1202                         return sprintf( '&#%d;', $point );
1203                 } else {
1204                         return null;
1205                 }
1206         }
1207
1208         /**
1209          * @param $codepoint
1210          * @return null|string
1211          */
1212         static function hexCharReference( $codepoint ) {
1213                 $point = hexdec( $codepoint );
1214                 if( Sanitizer::validateCodepoint( $point ) ) {
1215                         return sprintf( '&#x%x;', $point );
1216                 } else {
1217                         return null;
1218                 }
1219         }
1220
1221         /**
1222          * Returns true if a given Unicode codepoint is a valid character in XML.
1223          * @param $codepoint Integer
1224          * @return Boolean
1225          */
1226         private static function validateCodepoint( $codepoint ) {
1227                 return ($codepoint ==    0x09)
1228                         || ($codepoint ==    0x0a)
1229                         || ($codepoint ==    0x0d)
1230                         || ($codepoint >=    0x20 && $codepoint <=   0xd7ff)
1231                         || ($codepoint >=  0xe000 && $codepoint <=   0xfffd)
1232                         || ($codepoint >= 0x10000 && $codepoint <= 0x10ffff);
1233         }
1234
1235         /**
1236          * Decode any character references, numeric or named entities,
1237          * in the text and return a UTF-8 string.
1238          *
1239          * @param $text String
1240          * @return String
1241          */
1242         public static function decodeCharReferences( $text ) {
1243                 return preg_replace_callback(
1244                         self::CHAR_REFS_REGEX,
1245                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1246                         $text );
1247         }
1248
1249         /**
1250          * Decode any character references, numeric or named entities,
1251          * in the next and normalize the resulting string. (bug 14952)
1252          *
1253          * This is useful for page titles, not for text to be displayed,
1254          * MediaWiki allows HTML entities to escape normalization as a feature.
1255          *
1256          * @param $text String (already normalized, containing entities)
1257          * @return String (still normalized, without entities)
1258          */
1259         public static function decodeCharReferencesAndNormalize( $text ) {
1260                 global $wgContLang;
1261                 $text = preg_replace_callback(
1262                         self::CHAR_REFS_REGEX,
1263                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1264                         $text, /* limit */ -1, $count );
1265
1266                 if ( $count ) {
1267                         return $wgContLang->normalize( $text );
1268                 } else {
1269                         return $text;
1270                 }
1271         }
1272
1273         /**
1274          * @param $matches String
1275          * @return String
1276          */
1277         static function decodeCharReferencesCallback( $matches ) {
1278                 if( $matches[1] != '' ) {
1279                         return Sanitizer::decodeEntity( $matches[1] );
1280                 } elseif( $matches[2] != '' ) {
1281                         return  Sanitizer::decodeChar( intval( $matches[2] ) );
1282                 } elseif( $matches[3] != ''  ) {
1283                         return  Sanitizer::decodeChar( hexdec( $matches[3] ) );
1284                 }
1285                 # Last case should be an ampersand by itself
1286                 return $matches[0];
1287         }
1288
1289         /**
1290          * Return UTF-8 string for a codepoint if that is a valid
1291          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1292          * @param $codepoint Integer
1293          * @return String
1294          * @private
1295          */
1296         static function decodeChar( $codepoint ) {
1297                 if( Sanitizer::validateCodepoint( $codepoint ) ) {
1298                         return codepointToUtf8( $codepoint );
1299                 } else {
1300                         return UTF8_REPLACEMENT;
1301                 }
1302         }
1303
1304         /**
1305          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1306          * return the UTF-8 encoding of that character. Otherwise, returns
1307          * pseudo-entity source (eg &foo;)
1308          *
1309          * @param $name String
1310          * @return String
1311          */
1312         static function decodeEntity( $name ) {
1313                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1314                         $name = self::$htmlEntityAliases[$name];
1315                 }
1316                 if( isset( self::$htmlEntities[$name] ) ) {
1317                         return codepointToUtf8( self::$htmlEntities[$name] );
1318                 } else {
1319                         return "&$name;";
1320                 }
1321         }
1322
1323         /**
1324          * Fetch the whitelist of acceptable attributes for a given element name.
1325          *
1326          * @param $element String
1327          * @return Array
1328          */
1329         static function attributeWhitelist( $element ) {
1330                 static $list;
1331                 if( !isset( $list ) ) {
1332                         $list = Sanitizer::setupAttributeWhitelist();
1333                 }
1334                 return isset( $list[$element] )
1335                         ? $list[$element]
1336                         : array();
1337         }
1338
1339         /**
1340          * Foreach array key (an allowed HTML element), return an array
1341          * of allowed attributes
1342          * @return Array
1343          */
1344         static function setupAttributeWhitelist() {
1345                 global $wgAllowRdfaAttributes, $wgHtml5, $wgAllowMicrodataAttributes;
1346
1347                 $common = array( 'id', 'class', 'lang', 'dir', 'title', 'style' );
1348
1349                 if ( $wgAllowRdfaAttributes ) {
1350                         #RDFa attributes as specified in section 9 of http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1351                         $common = array_merge( $common, array(
1352                             'about', 'property', 'resource', 'datatype', 'typeof',
1353                         ) );
1354                 }
1355
1356                 if ( $wgHtml5 && $wgAllowMicrodataAttributes ) {
1357                         # add HTML5 microdata tages as pecified by http://www.whatwg.org/specs/web-apps/current-work/multipage/microdata.html#the-microdata-model
1358                         $common = array_merge( $common, array(
1359                             'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1360                         ) );
1361                 }
1362
1363                 $block = array_merge( $common, array( 'align' ) );
1364                 $tablealign = array( 'align', 'char', 'charoff', 'valign' );
1365                 $tablecell = array( 'abbr',
1366                                     'axis',
1367                                     'headers',
1368                                     'scope',
1369                                     'rowspan',
1370                                     'colspan',
1371                                     'nowrap', # deprecated
1372                                     'width',  # deprecated
1373                                     'height', # deprecated
1374                                     'bgcolor' # deprecated
1375                                     );
1376
1377                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1378                 # See: http://www.w3.org/TR/html4/
1379                 $whitelist = array (
1380                         # 7.5.4
1381                         'div'        => $block,
1382                         'center'     => $common, # deprecated
1383                         'span'       => $block, # ??
1384
1385                         # 7.5.5
1386                         'h1'         => $block,
1387                         'h2'         => $block,
1388                         'h3'         => $block,
1389                         'h4'         => $block,
1390                         'h5'         => $block,
1391                         'h6'         => $block,
1392
1393                         # 7.5.6
1394                         # address
1395
1396                         # 8.2.4
1397                         # bdo
1398
1399                         # 9.2.1
1400                         'em'         => $common,
1401                         'strong'     => $common,
1402                         'cite'       => $common,
1403                         'dfn'        => $common,
1404                         'code'       => $common,
1405                         'samp'       => $common,
1406                         'kbd'        => $common,
1407                         'var'        => $common,
1408                         'abbr'       => $common,
1409                         # acronym
1410
1411                         # 9.2.2
1412                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1413                         # q
1414
1415                         # 9.2.3
1416                         'sub'        => $common,
1417                         'sup'        => $common,
1418
1419                         # 9.3.1
1420                         'p'          => $block,
1421
1422                         # 9.3.2
1423                         'br'         => array( 'id', 'class', 'title', 'style', 'clear' ),
1424
1425                         # 9.3.4
1426                         'pre'        => array_merge( $common, array( 'width' ) ),
1427
1428                         # 9.4
1429                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1430                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1431
1432                         # 10.2
1433                         'ul'         => array_merge( $common, array( 'type' ) ),
1434                         'ol'         => array_merge( $common, array( 'type', 'start' ) ),
1435                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1436
1437                         # 10.3
1438                         'dl'         => $common,
1439                         'dd'         => $common,
1440                         'dt'         => $common,
1441
1442                         # 11.2.1
1443                         'table'      => array_merge( $common,
1444                                                                 array( 'summary', 'width', 'border', 'frame',
1445                                                                                 'rules', 'cellspacing', 'cellpadding',
1446                                                                                 'align', 'bgcolor',
1447                                                                 ) ),
1448
1449                         # 11.2.2
1450                         'caption'    => array_merge( $common, array( 'align' ) ),
1451
1452                         # 11.2.3
1453                         'thead'      => array_merge( $common, $tablealign ),
1454                         'tfoot'      => array_merge( $common, $tablealign ),
1455                         'tbody'      => array_merge( $common, $tablealign ),
1456
1457                         # 11.2.4
1458                         'colgroup'   => array_merge( $common, array( 'span', 'width' ), $tablealign ),
1459                         'col'        => array_merge( $common, array( 'span', 'width' ), $tablealign ),
1460
1461                         # 11.2.5
1462                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1463
1464                         # 11.2.6
1465                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1466                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1467
1468                         # 12.2 # NOTE: <a> is not allowed directly, but the attrib whitelist is used from the Parser object
1469                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1470
1471                         # 13.2
1472                         # Not usually allowed, but may be used for extension-style hooks
1473                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1474                         # true
1475                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1476
1477                         # 15.2.1
1478                         'tt'         => $common,
1479                         'b'          => $common,
1480                         'i'          => $common,
1481                         'big'        => $common,
1482                         'small'      => $common,
1483                         'strike'     => $common,
1484                         's'          => $common,
1485                         'u'          => $common,
1486
1487                         # 15.2.2
1488                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1489                         # basefont
1490
1491                         # 15.3
1492                         'hr'         => array_merge( $common, array( 'noshade', 'size', 'width' ) ),
1493
1494                         # XHTML Ruby annotation text module, simple ruby only.
1495                         # http://www.w3c.org/TR/ruby/
1496                         'ruby'       => $common,
1497                         # rbc
1498                         # rtc
1499                         'rb'         => $common,
1500                         'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),
1501                         'rp'         => $common,
1502
1503                         # MathML root element, where used for extensions
1504                         # 'title' may not be 100% valid here; it's XHTML
1505                         # http://www.w3.org/TR/REC-MathML/
1506                         'math'       => array( 'class', 'style', 'id', 'title' ),
1507                         );
1508                 return $whitelist;
1509         }
1510
1511         /**
1512          * Take a fragment of (potentially invalid) HTML and return
1513          * a version with any tags removed, encoded as plain text.
1514          *
1515          * Warning: this return value must be further escaped for literal
1516          * inclusion in HTML output as of 1.10!
1517          *
1518          * @param $text String: HTML fragment
1519          * @return String
1520          */
1521         static function stripAllTags( $text ) {
1522                 # Actual <tags>
1523                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1524
1525                 # Normalize &entities and whitespace
1526                 $text = self::decodeCharReferences( $text );
1527                 $text = self::normalizeWhitespace( $text );
1528
1529                 return $text;
1530         }
1531
1532         /**
1533          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1534          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1535          * PHP 5.1 doesn't.
1536          *
1537          * Use for passing XHTML fragments to PHP's XML parsing functions
1538          *
1539          * @return String
1540          */
1541         static function hackDocType() {
1542                 $out = "<!DOCTYPE html [\n";
1543                 foreach( self::$htmlEntities as $entity => $codepoint ) {
1544                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1545                 }
1546                 $out .= "]>\n";
1547                 return $out;
1548         }
1549
1550         /**
1551          * @param $url string
1552          * @return mixed|string
1553          */
1554         static function cleanUrl( $url ) {
1555                 # Normalize any HTML entities in input. They will be
1556                 # re-escaped by makeExternalLink().
1557                 $url = Sanitizer::decodeCharReferences( $url );
1558
1559                 # Escape any control characters introduced by the above step
1560                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1561                         array( __CLASS__, 'cleanUrlCallback' ), $url );
1562
1563                 # Validate hostname portion
1564                 $matches = array();
1565                 if( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1566                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1567
1568                         // Characters that will be ignored in IDNs.
1569                         // http://tools.ietf.org/html/3454#section-3.1
1570                         // Strip them before further processing so blacklists and such work.
1571                         $strip = "/
1572                                 \\s|          # general whitespace
1573                                 \xc2\xad|     # 00ad SOFT HYPHEN
1574                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1575                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1576                                 \xe2\x81\xa0| # 2060 WORD JOINER
1577                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1578                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1579                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1580                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1581                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1582                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1583                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1584                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe00f VARIATION SELECTOR-1-16
1585                                 /xuD";
1586
1587                         $host = preg_replace( $strip, '', $host );
1588
1589                         // @todo FIXME: Validate hostnames here
1590
1591                         return $protocol . $host . $rest;
1592                 } else {
1593                         return $url;
1594                 }
1595         }
1596
1597         /**
1598          * @param $matches array
1599          * @return string
1600          */
1601         static function cleanUrlCallback( $matches ) {
1602                 return urlencode( $matches[0] );
1603         }
1604
1605         /**
1606          * Does a string look like an e-mail address?
1607          *
1608          * This validates an email address using an HTML5 specification found at:
1609          * http://www.whatwg.org/specs/web-apps/current-work/multipage/states-of-the-type-attribute.html#valid-e-mail-address
1610          * Which as of 2011-01-24 says:
1611          *
1612          *   A valid e-mail address is a string that matches the ABNF production
1613          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1614          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1615          *   3.5.
1616          *
1617          * This function is an implementation of the specification as requested in
1618          * bug 22449.
1619          *
1620          * Client-side forms will use the same standard validation rules via JS or
1621          * HTML 5 validation; additional restrictions can be enforced server-side
1622          * by extensions via the 'isValidEmailAddr' hook.
1623          *
1624          * Note that this validation doesn't 100% match RFC 2822, but is believed
1625          * to be liberal enough for wide use. Some invalid addresses will still
1626          * pass validation here.
1627          *
1628          * @since 1.18
1629          *
1630          * @param $addr String E-mail address
1631          * @return Bool
1632          */
1633         public static function validateEmail( $addr ) {
1634                 $result = null;
1635                 if( !wfRunHooks( 'isValidEmailAddr', array( $addr, &$result ) ) ) {
1636                         return $result;
1637                 }
1638
1639                 // Please note strings below are enclosed in brackets [], this make the
1640                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1641                 // See bug 26948
1642                 $rfc5322_atext   = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~" ;
1643                 $rfc1034_ldh_str = "a-z0-9\\-" ;
1644
1645                 $HTML5_email_regexp = "/
1646                 ^                      # start of string
1647                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1648                 @                      # 'apostrophe'
1649                 [$rfc1034_ldh_str]+       # First domain part
1650                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1651                 $                      # End of string
1652                 /ix" ; // case Insensitive, eXtended
1653
1654                 return (bool) preg_match( $HTML5_email_regexp, $addr );
1655         }
1656 }