includes/Sanitizer.php

   1 <?php
   2 /**
   3  * HTML sanitizer for %MediaWiki.
   4  *
   5  * Copyright © 2002-2005 Brion Vibber <brion@pobox.com> et al
   6  * https://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  * HTML 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          */
  58         private static $htmlEntities = array(
  59                 'Aacute'   => 193,
  60                 'aacute'   => 225,
  61                 'Acirc'    => 194,
  62                 'acirc'    => 226,
  63                 'acute'    => 180,
  64                 'AElig'    => 198,
  65                 'aelig'    => 230,
  66                 'Agrave'   => 192,
  67                 'agrave'   => 224,
  68                 'alefsym'  => 8501,
  69                 'Alpha'    => 913,
  70                 'alpha'    => 945,
  71                 'amp'      => 38,
  72                 'and'      => 8743,
  73                 'ang'      => 8736,
  74                 'apos'     => 39, // New in XHTML & HTML 5; avoid in output for compatibility with IE.
  75                 'Aring'    => 197,
  76                 'aring'    => 229,
  77                 'asymp'    => 8776,
  78                 'Atilde'   => 195,
  79                 'atilde'   => 227,
  80                 'Auml'     => 196,
  81                 'auml'     => 228,
  82                 'bdquo'    => 8222,
  83                 'Beta'     => 914,
  84                 'beta'     => 946,
  85                 'brvbar'   => 166,
  86                 'bull'     => 8226,
  87                 'cap'      => 8745,
  88                 'Ccedil'   => 199,
  89                 'ccedil'   => 231,
  90                 'cedil'    => 184,
  91                 'cent'     => 162,
  92                 'Chi'      => 935,
  93                 'chi'      => 967,
  94                 'circ'     => 710,
  95                 'clubs'    => 9827,
  96                 'cong'     => 8773,
  97                 'copy'     => 169,
  98                 'crarr'    => 8629,
  99                 'cup'      => 8746,
 100                 'curren'   => 164,
 101                 'dagger'   => 8224,
 102                 'Dagger'   => 8225,
 103                 'darr'     => 8595,
 104                 'dArr'     => 8659,
 105                 'deg'      => 176,
 106                 'Delta'    => 916,
 107                 'delta'    => 948,
 108                 'diams'    => 9830,
 109                 'divide'   => 247,
 110                 'Eacute'   => 201,
 111                 'eacute'   => 233,
 112                 'Ecirc'    => 202,
 113                 'ecirc'    => 234,
 114                 'Egrave'   => 200,
 115                 'egrave'   => 232,
 116                 'empty'    => 8709,
 117                 'emsp'     => 8195,
 118                 'ensp'     => 8194,
 119                 'Epsilon'  => 917,
 120                 'epsilon'  => 949,
 121                 'equiv'    => 8801,
 122                 'Eta'      => 919,
 123                 'eta'      => 951,
 124                 'ETH'      => 208,
 125                 'eth'      => 240,
 126                 'Euml'     => 203,
 127                 'euml'     => 235,
 128                 'euro'     => 8364,
 129                 'exist'    => 8707,
 130                 'fnof'     => 402,
 131                 'forall'   => 8704,
 132                 'frac12'   => 189,
 133                 'frac14'   => 188,
 134                 'frac34'   => 190,
 135                 'frasl'    => 8260,
 136                 'Gamma'    => 915,
 137                 'gamma'    => 947,
 138                 'ge'       => 8805,
 139                 'gt'       => 62,
 140                 'harr'     => 8596,
 141                 'hArr'     => 8660,
 142                 'hearts'   => 9829,
 143                 'hellip'   => 8230,
 144                 'Iacute'   => 205,
 145                 'iacute'   => 237,
 146                 'Icirc'    => 206,
 147                 'icirc'    => 238,
 148                 'iexcl'    => 161,
 149                 'Igrave'   => 204,
 150                 'igrave'   => 236,
 151                 'image'    => 8465,
 152                 'infin'    => 8734,
 153                 'int'      => 8747,
 154                 'Iota'     => 921,
 155                 'iota'     => 953,
 156                 'iquest'   => 191,
 157                 'isin'     => 8712,
 158                 'Iuml'     => 207,
 159                 'iuml'     => 239,
 160                 'Kappa'    => 922,
 161                 'kappa'    => 954,
 162                 'Lambda'   => 923,
 163                 'lambda'   => 955,
 164                 'lang'     => 9001,
 165                 'laquo'    => 171,
 166                 'larr'     => 8592,
 167                 'lArr'     => 8656,
 168                 'lceil'    => 8968,
 169                 'ldquo'    => 8220,
 170                 'le'       => 8804,
 171                 'lfloor'   => 8970,
 172                 'lowast'   => 8727,
 173                 'loz'      => 9674,
 174                 'lrm'      => 8206,
 175                 'lsaquo'   => 8249,
 176                 'lsquo'    => 8216,
 177                 'lt'       => 60,
 178                 'macr'     => 175,
 179                 'mdash'    => 8212,
 180                 'micro'    => 181,
 181                 'middot'   => 183,
 182                 'minus'    => 8722,
 183                 'Mu'       => 924,
 184                 'mu'       => 956,
 185                 'nabla'    => 8711,
 186                 'nbsp'     => 160,
 187                 'ndash'    => 8211,
 188                 'ne'       => 8800,
 189                 'ni'       => 8715,
 190                 'not'      => 172,
 191                 'notin'    => 8713,
 192                 'nsub'     => 8836,
 193                 'Ntilde'   => 209,
 194                 'ntilde'   => 241,
 195                 'Nu'       => 925,
 196                 'nu'       => 957,
 197                 'Oacute'   => 211,
 198                 'oacute'   => 243,
 199                 'Ocirc'    => 212,
 200                 'ocirc'    => 244,
 201                 'OElig'    => 338,
 202                 'oelig'    => 339,
 203                 'Ograve'   => 210,
 204                 'ograve'   => 242,
 205                 'oline'    => 8254,
 206                 'Omega'    => 937,
 207                 'omega'    => 969,
 208                 'Omicron'  => 927,
 209                 'omicron'  => 959,
 210                 'oplus'    => 8853,
 211                 'or'       => 8744,
 212                 'ordf'     => 170,
 213                 'ordm'     => 186,
 214                 'Oslash'   => 216,
 215                 'oslash'   => 248,
 216                 'Otilde'   => 213,
 217                 'otilde'   => 245,
 218                 'otimes'   => 8855,
 219                 'Ouml'     => 214,
 220                 'ouml'     => 246,
 221                 'para'     => 182,
 222                 'part'     => 8706,
 223                 'permil'   => 8240,
 224                 'perp'     => 8869,
 225                 'Phi'      => 934,
 226                 'phi'      => 966,
 227                 'Pi'       => 928,
 228                 'pi'       => 960,
 229                 'piv'      => 982,
 230                 'plusmn'   => 177,
 231                 'pound'    => 163,
 232                 'prime'    => 8242,
 233                 'Prime'    => 8243,
 234                 'prod'     => 8719,
 235                 'prop'     => 8733,
 236                 'Psi'      => 936,
 237                 'psi'      => 968,
 238                 'quot'     => 34,
 239                 'radic'    => 8730,
 240                 'rang'     => 9002,
 241                 'raquo'    => 187,
 242                 'rarr'     => 8594,
 243                 'rArr'     => 8658,
 244                 'rceil'    => 8969,
 245                 'rdquo'    => 8221,
 246                 'real'     => 8476,
 247                 'reg'      => 174,
 248                 'rfloor'   => 8971,
 249                 'Rho'      => 929,
 250                 'rho'      => 961,
 251                 'rlm'      => 8207,
 252                 'rsaquo'   => 8250,
 253                 'rsquo'    => 8217,
 254                 'sbquo'    => 8218,
 255                 'Scaron'   => 352,
 256                 'scaron'   => 353,
 257                 'sdot'     => 8901,
 258                 'sect'     => 167,
 259                 'shy'      => 173,
 260                 'Sigma'    => 931,
 261                 'sigma'    => 963,
 262                 'sigmaf'   => 962,
 263                 'sim'      => 8764,
 264                 'spades'   => 9824,
 265                 'sub'      => 8834,
 266                 'sube'     => 8838,
 267                 'sum'      => 8721,
 268                 'sup'      => 8835,
 269                 'sup1'     => 185,
 270                 'sup2'     => 178,
 271                 'sup3'     => 179,
 272                 'supe'     => 8839,
 273                 'szlig'    => 223,
 274                 'Tau'      => 932,
 275                 'tau'      => 964,
 276                 'there4'   => 8756,
 277                 'Theta'    => 920,
 278                 'theta'    => 952,
 279                 'thetasym' => 977,
 280                 'thinsp'   => 8201,
 281                 'THORN'    => 222,
 282                 'thorn'    => 254,
 283                 'tilde'    => 732,
 284                 'times'    => 215,
 285                 'trade'    => 8482,
 286                 'Uacute'   => 218,
 287                 'uacute'   => 250,
 288                 'uarr'     => 8593,
 289                 'uArr'     => 8657,
 290                 'Ucirc'    => 219,
 291                 'ucirc'    => 251,
 292                 'Ugrave'   => 217,
 293                 'ugrave'   => 249,
 294                 'uml'      => 168,
 295                 'upsih'    => 978,
 296                 'Upsilon'  => 933,
 297                 'upsilon'  => 965,
 298                 'Uuml'     => 220,
 299                 'uuml'     => 252,
 300                 'weierp'   => 8472,
 301                 'Xi'       => 926,
 302                 'xi'       => 958,
 303                 'Yacute'   => 221,
 304                 'yacute'   => 253,
 305                 'yen'      => 165,
 306                 'Yuml'     => 376,
 307                 'yuml'     => 255,
 308                 'Zeta'     => 918,
 309                 'zeta'     => 950,
 310                 'zwj'      => 8205,
 311                 'zwnj'     => 8204
 312         );
 313
 314         /**
 315          * Character entity aliases accepted by MediaWiki
 316          */
 317         private static $htmlEntityAliases = array(
 318                 'רלמ' => 'rlm',
 319                 'رلم' => 'rlm',
 320         );
 321
 322         /**
 323          * Lazy-initialised attributes regex, see getAttribsRegex()
 324          */
 325         private static $attribsRegex;
 326
 327         /**
 328          * Regular expression to match HTML/XML attribute pairs within a tag.
 329          * Allows some... latitude.
 330          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 331          * @return string
 332          */
 333         static function getAttribsRegex() {
 334                 if ( self::$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 string $text
 360          * @param callable $processCallback Callback to do any variable or parameter
 361          *   replacements in HTML attribute values
 362          * @param array|bool $args Arguments for the processing callback
 363          * @param array $extratags For any extra tags to include
 364          * @param array $removetags For any tags (default or extra) to exclude
 365          * @return string
 366          */
 367         static function removeHTMLtags( $text, $processCallback = null,
 368                 $args = array(), $extratags = array(), $removetags = array()
 369         ) {
 370                 global $wgUseTidy, $wgAllowMicrodataAttributes, $wgAllowImageTag;
 371
 372                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 373                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 374
 375                 wfProfileIn( __METHOD__ );
 376
 377                 // Base our staticInitialised variable off of the global config state so that if the globals
 378                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 379                 $globalContext = implode( '-', compact( 'wgAllowMicrodataAttributes', 'wgAllowImageTag' ) );
 380                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 381
 382                         $htmlpairsStatic = array( # Tags that must be closed
 383                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 384                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 385                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 386                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 387                                 'ruby', 'rb', 'rp', 'rt', 'rtc', 'p', 'span', 'abbr', 'dfn',
 388                                 'kbd', 'samp', 'data', 'time', 'mark'
 389                         );
 390                         $htmlsingle = array(
 391                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd'
 392                         );
 393                         $htmlsingleonly = array( # Elements that cannot have close tags
 394                                 'br', 'wbr', 'hr'
 395                         );
 396                         if ( $wgAllowMicrodataAttributes ) {
 397                                 $htmlsingle[] = $htmlsingleonly[] = 'meta';
 398                                 $htmlsingle[] = $htmlsingleonly[] = 'link';
 399                         }
 400                         $htmlnest = array( # Tags that can be nested--??
 401                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 402                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 403                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 404                         );
 405                         $tabletags = array( # Can only appear inside table, we will close them
 406                                 'td', 'th', 'tr',
 407                         );
 408                         $htmllist = array( # Tags used by list
 409                                 'ul', 'ol',
 410                         );
 411                         $listtags = array( # Tags that can appear in a list
 412                                 'li',
 413                         );
 414
 415                         if ( $wgAllowImageTag ) {
 416                                 $htmlsingle[] = 'img';
 417                                 $htmlsingleonly[] = 'img';
 418                         }
 419
 420                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 421                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 422
 423                         # Convert them all to hashtables for faster lookup
 424                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 425                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 426                         foreach ( $vars as $var ) {
 427                                 $$var = array_flip( $$var );
 428                         }
 429                         $staticInitialised = $globalContext;
 430                 }
 431                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 432                 $extratags = array_flip( $extratags );
 433                 $removetags = array_flip( $removetags );
 434                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 435                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 436
 437                 # Remove HTML comments
 438                 $text = Sanitizer::removeHTMLcomments( $text );
 439                 $bits = explode( '<', $text );
 440                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 441                 if ( !$wgUseTidy ) {
 442                         $tagstack = $tablestack = array();
 443                         foreach ( $bits as $x ) {
 444                                 $regs = array();
 445                                 # $slash: Does the current element start with a '/'?
 446                                 # $t: Current element name
 447                                 # $params: String between element name and >
 448                                 # $brace: Ending '>' or '/>'
 449                                 # $rest: Everything until the next element of $bits
 450                                 if ( preg_match( '!^(/?)([^\\s/>]+)([^>]*?)(/{0,1}>)([^<]*)$!', $x, $regs ) ) {
 451                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 452                                 } else {
 453                                         $slash = $t = $params = $brace = $rest = null;
 454                                 }
 455
 456                                 $badtag = false;
 457                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 458                                         # Check our stack
 459                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 460                                                 $badtag = true;
 461                                         } elseif ( $slash ) {
 462                                                 # Closing a tag... is it the one we just opened?
 463                                                 wfSuppressWarnings();
 464                                                 $ot = array_pop( $tagstack );
 465                                                 wfRestoreWarnings();
 466
 467                                                 if ( $ot != $t ) {
 468                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 469                                                                 # Pop all elements with an optional close tag
 470                                                                 # and see if we find a match below them
 471                                                                 $optstack = array();
 472                                                                 array_push( $optstack, $ot );
 473                                                                 wfSuppressWarnings();
 474                                                                 $ot = array_pop( $tagstack );
 475                                                                 wfRestoreWarnings();
 476                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 477                                                                         array_push( $optstack, $ot );
 478                                                                         wfSuppressWarnings();
 479                                                                         $ot = array_pop( $tagstack );
 480                                                                         wfRestoreWarnings();
 481                                                                 }
 482                                                                 if ( $t != $ot ) {
 483                                                                         # No match. Push the optional elements back again
 484                                                                         $badtag = true;
 485                                                                         wfSuppressWarnings();
 486                                                                         $ot = array_pop( $optstack );
 487                                                                         wfRestoreWarnings();
 488                                                                         while ( $ot ) {
 489                                                                                 array_push( $tagstack, $ot );
 490                                                                                 wfSuppressWarnings();
 491                                                                                 $ot = array_pop( $optstack );
 492                                                                                 wfRestoreWarnings();
 493                                                                         }
 494                                                                 }
 495                                                         } else {
 496                                                                 wfSuppressWarnings();
 497                                                                 array_push( $tagstack, $ot );
 498                                                                 wfRestoreWarnings();
 499
 500                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 501                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 502                                                                         $badtag = true;
 503                                                                 }
 504                                                         }
 505                                                 } else {
 506                                                         if ( $t == 'table' ) {
 507                                                                 $tagstack = array_pop( $tablestack );
 508                                                         }
 509                                                 }
 510                                                 $newparams = '';
 511                                         } else {
 512                                                 # Keep track for later
 513                                                 if ( isset( $tabletags[$t] ) &&
 514                                                 !in_array( 'table', $tagstack ) ) {
 515                                                         $badtag = true;
 516                                                 } elseif ( in_array( $t, $tagstack ) &&
 517                                                 !isset( $htmlnest[$t] ) ) {
 518                                                         $badtag = true;
 519                                                 # Is it a self closed htmlpair ? (bug 5487)
 520                                                 } elseif ( $brace == '/>' &&
 521                                                 isset( $htmlpairs[$t] ) ) {
 522                                                         $badtag = true;
 523                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 524                                                         # Hack to force empty tag for unclosable elements
 525                                                         $brace = '/>';
 526                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 527                                                         # Hack to not close $htmlsingle tags
 528                                                         $brace = null;
 529                                                         # Still need to push this optionally-closed tag to
 530                                                         # the tag stack so that we can match end tags
 531                                                         # instead of marking them as bad.
 532                                                         array_push( $tagstack, $t );
 533                                                 } elseif ( isset( $tabletags[$t] )
 534                                                 && in_array( $t, $tagstack ) ) {
 535                                                         // New table tag but forgot to close the previous one
 536                                                         $text .= "</$t>";
 537                                                 } else {
 538                                                         if ( $t == 'table' ) {
 539                                                                 array_push( $tablestack, $tagstack );
 540                                                                 $tagstack = array();
 541                                                         }
 542                                                         array_push( $tagstack, $t );
 543                                                 }
 544
 545                                                 # Replace any variables or template parameters with
 546                                                 # plaintext results.
 547                                                 if ( is_callable( $processCallback ) ) {
 548                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 549                                                 }
 550
 551                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 552                                                         $badtag = true;
 553                                                 }
 554
 555                                                 # Strip non-approved attributes from the tag
 556                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 557                                         }
 558                                         if ( !$badtag ) {
 559                                                 $rest = str_replace( '>', '&gt;', $rest );
 560                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 561                                                 $text .= "<$slash$t$newparams$close>$rest";
 562                                                 continue;
 563                                         }
 564                                 }
 565                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 566                         }
 567                         # Close off any remaining tags
 568                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 569                                 $text .= "</$t>\n";
 570                                 if ( $t == 'table' ) {
 571                                         $tagstack = array_pop( $tablestack );
 572                                 }
 573                         }
 574                 } else {
 575                         # this might be possible using tidy itself
 576                         foreach ( $bits as $x ) {
 577                                 preg_match(
 578                                         '/^(\\/?)(\\w+)([^>]*?)(\\/{0,1}>)([^<]*)$/',
 579                                         $x,
 580                                         $regs
 581                                 );
 582
 583                                 wfSuppressWarnings();
 584                                 list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 585                                 wfRestoreWarnings();
 586
 587                                 $badtag = false;
 588                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 589                                         if ( is_callable( $processCallback ) ) {
 590                                                 call_user_func_array( $processCallback, array( &$params, $args ) );
 591                                         }
 592
 593                                         if ( !Sanitizer::validateTag( $params, $t ) ) {
 594                                                 $badtag = true;
 595                                         }
 596
 597                                         $newparams = Sanitizer::fixTagAttributes( $params, $t );
 598                                         if ( !$badtag ) {
 599                                                 $rest = str_replace( '>', '&gt;', $rest );
 600                                                 $text .= "<$slash$t$newparams$brace$rest";
 601                                                 continue;
 602                                         }
 603                                 }
 604                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 605                         }
 606                 }
 607                 wfProfileOut( __METHOD__ );
 608                 return $text;
 609         }
 610
 611         /**
 612          * Remove '<!--', '-->', and everything between.
 613          * To avoid leaving blank lines, when a comment is both preceded
 614          * and followed by a newline (ignoring spaces), trim leading and
 615          * trailing spaces and one of the newlines.
 616          *
 617          * @private
 618          * @param string $text
 619          * @return string
 620          */
 621         static function removeHTMLcomments( $text ) {
 622                 wfProfileIn( __METHOD__ );
 623                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 624                         $end = strpos( $text, '-->', $start + 4 );
 625                         if ( $end === false ) {
 626                                 # Unterminated comment; bail out
 627                                 break;
 628                         }
 629
 630                         $end += 3;
 631
 632                         # Trim space and newline if the comment is both
 633                         # preceded and followed by a newline
 634                         $spaceStart = max( $start - 1, 0 );
 635                         $spaceLen = $end - $spaceStart;
 636                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 637                                 $spaceStart--;
 638                                 $spaceLen++;
 639                         }
 640                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 641                                 $spaceLen++;
 642                         }
 643                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 644                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 645                                 # Remove the comment, leading and trailing
 646                                 # spaces, and leave only one newline.
 647                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 648                         } else {
 649                                 # Remove just the comment.
 650                                 $text = substr_replace( $text, '', $start, $end - $start );
 651                         }
 652                 }
 653                 wfProfileOut( __METHOD__ );
 654                 return $text;
 655         }
 656
 657         /**
 658          * Takes attribute names and values for a tag and the tag name and
 659          * validates that the tag is allowed to be present.
 660          * This DOES NOT validate the attributes, nor does it validate the
 661          * tags themselves. This method only handles the special circumstances
 662          * where we may want to allow a tag within content but ONLY when it has
 663          * specific attributes set.
 664          *
 665          * @param string $params
 666          * @param string $element
 667          * @return bool
 668          */
 669         static function validateTag( $params, $element ) {
 670                 $params = Sanitizer::decodeTagAttributes( $params );
 671
 672                 if ( $element == 'meta' || $element == 'link' ) {
 673                         if ( !isset( $params['itemprop'] ) ) {
 674                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 675                                 return false;
 676                         }
 677                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 678                                 // <meta> must have a content="" for the itemprop
 679                                 return false;
 680                         }
 681                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 682                                 // <link> must have an associated href=""
 683                                 return false;
 684                         }
 685                 }
 686
 687                 return true;
 688         }
 689
 690         /**
 691          * Take an array of attribute names and values and normalize or discard
 692          * illegal values for the given element type.
 693          *
 694          * - Discards attributes not on a whitelist for the given element
 695          * - Unsafe style attributes are discarded
 696          * - Invalid id attributes are re-encoded
 697          *
 698          * @param array $attribs
 699          * @param string $element
 700          * @return array
 701          *
 702          * @todo Check for legal values where the DTD limits things.
 703          * @todo Check for unique id attribute :P
 704          */
 705         static function validateTagAttributes( $attribs, $element ) {
 706                 return Sanitizer::validateAttributes( $attribs,
 707                         Sanitizer::attributeWhitelist( $element ) );
 708         }
 709
 710         /**
 711          * Take an array of attribute names and values and normalize or discard
 712          * illegal values for the given whitelist.
 713          *
 714          * - Discards attributes not the given whitelist
 715          * - Unsafe style attributes are discarded
 716          * - Invalid id attributes are re-encoded
 717          *
 718          * @param array $attribs
 719          * @param array $whitelist List of allowed attribute names
 720          * @return array
 721          *
 722          * @todo Check for legal values where the DTD limits things.
 723          * @todo Check for unique id attribute :P
 724          */
 725         static function validateAttributes( $attribs, $whitelist ) {
 726                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 727
 728                 $whitelist = array_flip( $whitelist );
 729                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 730
 731                 $out = array();
 732                 foreach ( $attribs as $attribute => $value ) {
 733                         #allow XML namespace declaration if RDFa is enabled
 734                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 735                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 736                                         $out[$attribute] = $value;
 737                                 }
 738
 739                                 continue;
 740                         }
 741
 742                         # Allow any attribute beginning with "data-"
 743                         if ( !preg_match( '/^data-/i', $attribute ) && !isset( $whitelist[$attribute] ) ) {
 744                                 continue;
 745                         }
 746
 747                         # Strip javascript "expression" from stylesheets.
 748                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 749                         if ( $attribute == 'style' ) {
 750                                 $value = Sanitizer::checkCss( $value );
 751                         }
 752
 753                         if ( $attribute === 'id' ) {
 754                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 755                         }
 756
 757                         # WAI-ARIA
 758                         # http://www.w3.org/TR/wai-aria/
 759                         # http://www.whatwg.org/html/elements.html#wai-aria
 760                         # For now we only support role="presentation" until we work out what roles should be
 761                         # usable by content and we ensure that our code explicitly rejects patterns that
 762                         # violate HTML5's ARIA restrictions.
 763                         if ( $attribute === 'role' && $value !== 'presentation' ) {
 764                                 continue;
 765                         }
 766
 767                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 768                         // Check them for sanity.
 769                         if ( $attribute === 'rel' || $attribute === 'rev'
 770                                 # RDFa
 771                                 || $attribute === 'about' || $attribute === 'property'
 772                                 || $attribute === 'resource' || $attribute === 'datatype'
 773                                 || $attribute === 'typeof'
 774                                 # HTML5 microdata
 775                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 776                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 777                                 || $attribute === 'itemtype'
 778                         ) {
 779                                 //Paranoia. Allow "simple" values but suppress javascript
 780                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 781                                         continue;
 782                                 }
 783                         }
 784
 785                         # NOTE: even though elements using href/src are not allowed directly, supply
 786                         #       validation code that can be used by tag hook handlers, etc
 787                         if ( $attribute === 'href' || $attribute === 'src' ) {
 788                                 if ( !preg_match( $hrefExp, $value ) ) {
 789                                         continue; //drop any href or src attributes not using an allowed protocol.
 790                                         // NOTE: this also drops all relative URLs
 791                                 }
 792                         }
 793
 794                         // If this attribute was previously set, override it.
 795                         // Output should only have one attribute of each name.
 796                         $out[$attribute] = $value;
 797                 }
 798
 799                 if ( $wgAllowMicrodataAttributes ) {
 800                         # itemtype, itemid, itemref don't make sense without itemscope
 801                         if ( !array_key_exists( 'itemscope', $out ) ) {
 802                                 unset( $out['itemtype'] );
 803                                 unset( $out['itemid'] );
 804                                 unset( $out['itemref'] );
 805                         }
 806                         # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 807                 }
 808                 return $out;
 809         }
 810
 811         /**
 812          * Merge two sets of HTML attributes.  Conflicting items in the second set
 813          * will override those in the first, except for 'class' attributes which
 814          * will be combined (if they're both strings).
 815          *
 816          * @todo implement merging for other attributes such as style
 817          * @param array $a
 818          * @param array $b
 819          * @return array
 820          */
 821         static function mergeAttributes( $a, $b ) {
 822                 $out = array_merge( $a, $b );
 823                 if ( isset( $a['class'] ) && isset( $b['class'] )
 824                         && is_string( $a['class'] ) && is_string( $b['class'] )
 825                         && $a['class'] !== $b['class']
 826                 ) {
 827                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 828                                 -1, PREG_SPLIT_NO_EMPTY );
 829                         $out['class'] = implode( ' ', array_unique( $classes ) );
 830                 }
 831                 return $out;
 832         }
 833
 834         /**
 835          * Normalize CSS into a format we can easily search for hostile input
 836          *  - decode character references
 837          *  - decode escape sequences
 838          *  - convert characters that IE6 interprets into ascii
 839          *  - remove comments, unless the entire value is one single comment
 840          * @param string $value the css string
 841          * @return string normalized css
 842          */
 843         public static function normalizeCss( $value ) {
 844
 845                 // Decode character references like &#123;
 846                 $value = Sanitizer::decodeCharReferences( $value );
 847
 848                 // Decode escape sequences and line continuation
 849                 // See the grammar in the CSS 2 spec, appendix D.
 850                 // This has to be done AFTER decoding character references.
 851                 // This means it isn't possible for this function to return
 852                 // unsanitized escape sequences. It is possible to manufacture
 853                 // input that contains character references that decode to
 854                 // escape sequences that decode to character references, but
 855                 // it's OK for the return value to contain character references
 856                 // because the caller is supposed to escape those anyway.
 857                 static $decodeRegex;
 858                 if ( !$decodeRegex ) {
 859                         $space = '[\\x20\\t\\r\\n\\f]';
 860                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 861                         $backslash = '\\\\';
 862                         $decodeRegex = "/ $backslash
 863                                 (?:
 864                                         ($nl) |  # 1. Line continuation
 865                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 866                                         (.) | # 3. backslash cancelling special meaning
 867                                         () | # 4. backslash at end of string
 868                                 )/xu";
 869                 }
 870                 $value = preg_replace_callback( $decodeRegex,
 871                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 872
 873                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 874                 $value = preg_replace_callback(
 875                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (bug 58088)
 876                         function ( $matches ) {
 877                                 $cp = utf8ToCodepoint( $matches[0] );
 878                                 if ( $cp === false ) {
 879                                         return '';
 880                                 }
 881                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 882                         },
 883                         $value
 884                 );
 885
 886                 // Convert more characters IE6 might treat as ascii
 887                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 888                 $value = str_replace(
 889                         array( 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ),
 890                         array( 'r', 'n', 'n', 'l', 'i', '(', '(' ),
 891                         $value
 892                 );
 893
 894                 // Let the value through if it's nothing but a single comment, to
 895                 // allow other functions which may reject it to pass some error
 896                 // message through.
 897                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 898                         // Remove any comments; IE gets token splitting wrong
 899                         // This must be done AFTER decoding character references and
 900                         // escape sequences, because those steps can introduce comments
 901                         // This step cannot introduce character references or escape
 902                         // sequences, because it replaces comments with spaces rather
 903                         // than removing them completely.
 904                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 905
 906                         // Remove anything after a comment-start token, to guard against
 907                         // incorrect client implementations.
 908                         $commentPos = strpos( $value, '/*' );
 909                         if ( $commentPos !== false ) {
 910                                 $value = substr( $value, 0, $commentPos );
 911                         }
 912                 }
 913
 914                 // S followed by repeat, iteration, or prolonged sound marks,
 915                 // which IE will treat as "ss"
 916                 $value = preg_replace(
 917                         '/s(?:
 918                                 \xE3\x80\xB1 | # U+3031
 919                                 \xE3\x82\x9D | # U+309D
 920                                 \xE3\x83\xBC | # U+30FC
 921                                 \xE3\x83\xBD | # U+30FD
 922                                 \xEF\xB9\xBC | # U+FE7C
 923                                 \xEF\xB9\xBD | # U+FE7D
 924                                 \xEF\xBD\xB0   # U+FF70
 925                         )/ix',
 926                         'ss',
 927                         $value
 928                 );
 929
 930                 return $value;
 931         }
 932
 933
 934         /**
 935          * Pick apart some CSS and check it for forbidden or unsafe structures.
 936          * Returns a sanitized string. This sanitized string will have
 937          * character references and escape sequences decoded and comments
 938          * stripped (unless it is itself one valid comment, in which case the value
 939          * will be passed through). If the input is just too evil, only a comment
 940          * complaining about evilness will be returned.
 941          *
 942          * Currently URL references, 'expression', 'tps' are forbidden.
 943          *
 944          * NOTE: Despite the fact that character references are decoded, the
 945          * returned string may contain character references given certain
 946          * clever input strings. These character references must
 947          * be escaped before the return value is embedded in HTML.
 948          *
 949          * @param string $value
 950          * @return string
 951          */
 952         static function checkCss( $value ) {
 953                 $value = self::normalizeCss( $value );
 954
 955                 // Reject problematic keywords and control characters
 956                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ) {
 957                         return '/* invalid control char */';
 958                 } elseif ( preg_match(
 959                         '! expression
 960                                 | filter\s*:
 961                                 | accelerator\s*:
 962                                 | -o-link\s*:
 963                                 | -o-link-source\s*:
 964                                 | -o-replace\s*:
 965                                 | url\s*\(
 966                                 | image\s*\(
 967                                 | image-set\s*\(
 968                         !ix', $value ) ) {
 969                         return '/* insecure input */';
 970                 }
 971                 return $value;
 972         }
 973
 974         /**
 975          * @param array $matches
 976          * @return string
 977          */
 978         static function cssDecodeCallback( $matches ) {
 979                 if ( $matches[1] !== '' ) {
 980                         // Line continuation
 981                         return '';
 982                 } elseif ( $matches[2] !== '' ) {
 983                         $char = codepointToUtf8( hexdec( $matches[2] ) );
 984                 } elseif ( $matches[3] !== '' ) {
 985                         $char = $matches[3];
 986                 } else {
 987                         $char = '\\';
 988                 }
 989                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
 990                         // These characters need to be escaped in strings
 991                         // Clean up the escape sequence to avoid parsing errors by clients
 992                         return '\\' . dechex( ord( $char ) ) . ' ';
 993                 } else {
 994                         // Decode unnecessary escape
 995                         return $char;
 996                 }
 997         }
 998
 999         /**
1000          * Take a tag soup fragment listing an HTML element's attributes
1001          * and normalize it to well-formed XML, discarding unwanted attributes.
1002          * Output is safe for further wikitext processing, with escaping of
1003          * values that could trigger problems.
1004          *
1005          * - Normalizes attribute names to lowercase
1006          * - Discards attributes not on a whitelist for the given element
1007          * - Turns broken or invalid entities into plaintext
1008          * - Double-quotes all attribute values
1009          * - Attributes without values are given the name as attribute
1010          * - Double attributes are discarded
1011          * - Unsafe style attributes are discarded
1012          * - Prepends space if there are attributes.
1013          *
1014          * @param string $text
1015          * @param string $element
1016          * @return string
1017          */
1018         static function fixTagAttributes( $text, $element ) {
1019                 if ( trim( $text ) == '' ) {
1020                         return '';
1021                 }
1022
1023                 $decoded = Sanitizer::decodeTagAttributes( $text );
1024                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
1025
1026                 return Sanitizer::safeEncodeTagAttributes( $stripped );
1027         }
1028
1029         /**
1030          * Encode an attribute value for HTML output.
1031          * @param string $text
1032          * @return string HTML-encoded text fragment
1033          */
1034         static function encodeAttribute( $text ) {
1035                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1036
1037                 // Whitespace is normalized during attribute decoding,
1038                 // so if we've been passed non-spaces we must encode them
1039                 // ahead of time or they won't be preserved.
1040                 $encValue = strtr( $encValue, array(
1041                         "\n" => '&#10;',
1042                         "\r" => '&#13;',
1043                         "\t" => '&#9;',
1044                 ) );
1045
1046                 return $encValue;
1047         }
1048
1049         /**
1050          * Encode an attribute value for HTML tags, with extra armoring
1051          * against further wiki processing.
1052          * @param string $text
1053          * @return string HTML-encoded text fragment
1054          */
1055         static function safeEncodeAttribute( $text ) {
1056                 $encValue = Sanitizer::encodeAttribute( $text );
1057
1058                 # Templates and links may be expanded in later parsing,
1059                 # creating invalid or dangerous output. Suppress this.
1060                 $encValue = strtr( $encValue, array(
1061                         '<'    => '&lt;',   // This should never happen,
1062                         '>'    => '&gt;',   // we've received invalid input
1063                         '"'    => '&quot;', // which should have been escaped.
1064                         '{'    => '&#123;',
1065                         '['    => '&#91;',
1066                         "''"   => '&#39;&#39;',
1067                         'ISBN' => '&#73;SBN',
1068                         'RFC'  => '&#82;FC',
1069                         'PMID' => '&#80;MID',
1070                         '|'    => '&#124;',
1071                         '__'   => '&#95;_',
1072                 ) );
1073
1074                 # Stupid hack
1075                 $encValue = preg_replace_callback(
1076                         '/((?i)' . wfUrlProtocols() . ')/',
1077                         array( 'Sanitizer', 'armorLinksCallback' ),
1078                         $encValue );
1079                 return $encValue;
1080         }
1081
1082         /**
1083          * Given a value, escape it so that it can be used in an id attribute and
1084          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1085          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1086          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1087          * escaped with lots of dots.
1088          *
1089          * To ensure we don't have to bother escaping anything, we also strip ', ",
1090          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1091          * We also strip # because it upsets IE, and % because it could be
1092          * ambiguous if it's part of something that looks like a percent escape
1093          * (which don't work reliably in fragments cross-browser).
1094          *
1095          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
1096          *   in the id and name attributes
1097          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1098          *   the id attribute
1099          * @see http://www.whatwg.org/html/elements.html#the-id-attribute
1100          *   HTML5 definition of id attribute
1101          *
1102          * @param string $id Id to escape
1103          * @param string|array $options String or array of strings (default is array()):
1104          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1105          *       so don't pay attention if the first character isn't valid at the
1106          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1107          *       false.
1108          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1109          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1110          *       anchors and links won't break.
1111          * @return string
1112          */
1113         static function escapeId( $id, $options = array() ) {
1114                 global $wgExperimentalHtmlIds;
1115                 $options = (array)$options;
1116
1117                 $id = Sanitizer::decodeCharReferences( $id );
1118
1119                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1120                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1121                         $id = trim( $id, '_' );
1122                         if ( $id === '' ) {
1123                                 # Must have been all whitespace to start with.
1124                                 return '_';
1125                         } else {
1126                                 return $id;
1127                         }
1128                 }
1129
1130                 # HTML4-style escaping
1131                 static $replace = array(
1132                         '%3A' => ':',
1133                         '%' => '.'
1134                 );
1135
1136                 $id = urlencode( strtr( $id, ' ', '_' ) );
1137                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1138
1139                 if ( !preg_match( '/^[a-zA-Z]/', $id )
1140                 && !in_array( 'noninitial', $options ) ) {
1141                         // Initial character must be a letter!
1142                         $id = "x$id";
1143                 }
1144                 return $id;
1145         }
1146
1147         /**
1148          * Given a value, escape it so that it can be used as a CSS class and
1149          * return it.
1150          *
1151          * @todo For extra validity, input should be validated UTF-8.
1152          *
1153          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1154          *
1155          * @param string $class
1156          * @return string
1157          */
1158         static function escapeClass( $class ) {
1159                 // Convert ugly stuff to underscores and kill underscores in ugly places
1160                 return rtrim( preg_replace(
1161                         array( '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ),
1162                         '_',
1163                         $class ), '_' );
1164         }
1165
1166         /**
1167          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1168          * This allows (generally harmless) entities like &#160; to survive.
1169          *
1170          * @param string $html HTML to escape
1171          * @return string Escaped input
1172          */
1173         static function escapeHtmlAllowEntities( $html ) {
1174                 $html = Sanitizer::decodeCharReferences( $html );
1175                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1176                 # hurt.
1177                 $html = htmlspecialchars( $html, ENT_QUOTES );
1178                 return $html;
1179         }
1180
1181         /**
1182          * Regex replace callback for armoring links against further processing.
1183          * @param array $matches
1184          * @return string
1185          */
1186         private static function armorLinksCallback( $matches ) {
1187                 return str_replace( ':', '&#58;', $matches[1] );
1188         }
1189
1190         /**
1191          * Return an associative array of attribute names and values from
1192          * a partial tag string. Attribute names are forces to lowercase,
1193          * character references are decoded to UTF-8 text.
1194          *
1195          * @param string $text
1196          * @return array
1197          */
1198         public static function decodeTagAttributes( $text ) {
1199                 if ( trim( $text ) == '' ) {
1200                         return array();
1201                 }
1202
1203                 $attribs = array();
1204                 $pairs = array();
1205                 if ( !preg_match_all(
1206                         self::getAttribsRegex(),
1207                         $text,
1208                         $pairs,
1209                         PREG_SET_ORDER ) ) {
1210                         return $attribs;
1211                 }
1212
1213                 foreach ( $pairs as $set ) {
1214                         $attribute = strtolower( $set[1] );
1215                         $value = Sanitizer::getTagAttributeCallback( $set );
1216
1217                         // Normalize whitespace
1218                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1219                         $value = trim( $value );
1220
1221                         // Decode character references
1222                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1223                 }
1224                 return $attribs;
1225         }
1226
1227         /**
1228          * Build a partial tag string from an associative array of attribute
1229          * names and values as returned by decodeTagAttributes.
1230          *
1231          * @param array $assoc_array
1232          * @return string
1233          */
1234         public static function safeEncodeTagAttributes( $assoc_array ) {
1235                 $attribs = array();
1236                 foreach ( $assoc_array as $attribute => $value ) {
1237                         $encAttribute = htmlspecialchars( $attribute );
1238                         $encValue = Sanitizer::safeEncodeAttribute( $value );
1239
1240                         $attribs[] = "$encAttribute=\"$encValue\"";
1241                 }
1242                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1243         }
1244
1245         /**
1246          * Pick the appropriate attribute value from a match set from the
1247          * attribs regex matches.
1248          *
1249          * @param array $set
1250          * @throws MWException When tag conditions are not met.
1251          * @return string
1252          */
1253         private static function getTagAttributeCallback( $set ) {
1254                 if ( isset( $set[6] ) ) {
1255                         # Illegal #XXXXXX color with no quotes.
1256                         return $set[6];
1257                 } elseif ( isset( $set[5] ) ) {
1258                         # No quotes.
1259                         return $set[5];
1260                 } elseif ( isset( $set[4] ) ) {
1261                         # Single-quoted
1262                         return $set[4];
1263                 } elseif ( isset( $set[3] ) ) {
1264                         # Double-quoted
1265                         return $set[3];
1266                 } elseif ( !isset( $set[2] ) ) {
1267                         # In XHTML, attributes must have a value.
1268                         # For 'reduced' form, return explicitly the attribute name here.
1269                         return $set[1];
1270                 } else {
1271                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1272                 }
1273         }
1274
1275         /**
1276          * Normalize whitespace and character references in an XML source-
1277          * encoded text for an attribute value.
1278          *
1279          * See http://www.w3.org/TR/REC-xml/#AVNormalize for background,
1280          * but note that we're not returning the value, but are returning
1281          * XML source fragments that will be slapped into output.
1282          *
1283          * @param string $text
1284          * @return string
1285          * @todo Remove, unused?
1286          */
1287         private static function normalizeAttributeValue( $text ) {
1288                 return str_replace( '"', '&quot;',
1289                         self::normalizeWhitespace(
1290                                 Sanitizer::normalizeCharReferences( $text ) ) );
1291         }
1292
1293         /**
1294          * @param string $text
1295          * @return string
1296          */
1297         private static function normalizeWhitespace( $text ) {
1298                 return preg_replace(
1299                         '/\r\n|[\x20\x0d\x0a\x09]/',
1300                         ' ',
1301                         $text );
1302         }
1303
1304         /**
1305          * Normalizes whitespace in a section name, such as might be returned
1306          * by Parser::stripSectionName(), for use in the id's that are used for
1307          * section links.
1308          *
1309          * @param string $section
1310          * @return string
1311          */
1312         static function normalizeSectionNameWhitespace( $section ) {
1313                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1314         }
1315
1316         /**
1317          * Ensure that any entities and character references are legal
1318          * for XML and XHTML specifically. Any stray bits will be
1319          * &amp;-escaped to result in a valid text fragment.
1320          *
1321          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1322          *   numericized (this way we're well-formed even without a DTD)
1323          * b. any numeric char refs must be legal chars, not invalid or forbidden
1324          * c. use lower cased "&#x", not "&#X"
1325          * d. fix or reject non-valid attributes
1326          *
1327          * @param string $text
1328          * @return string
1329          * @private
1330          */
1331         static function normalizeCharReferences( $text ) {
1332                 return preg_replace_callback(
1333                         self::CHAR_REFS_REGEX,
1334                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1335                         $text );
1336         }
1337
1338         /**
1339          * @param string $matches
1340          * @return string
1341          */
1342         static function normalizeCharReferencesCallback( $matches ) {
1343                 $ret = null;
1344                 if ( $matches[1] != '' ) {
1345                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1346                 } elseif ( $matches[2] != '' ) {
1347                         $ret = Sanitizer::decCharReference( $matches[2] );
1348                 } elseif ( $matches[3] != '' ) {
1349                         $ret = Sanitizer::hexCharReference( $matches[3] );
1350                 }
1351                 if ( is_null( $ret ) ) {
1352                         return htmlspecialchars( $matches[0] );
1353                 } else {
1354                         return $ret;
1355                 }
1356         }
1357
1358         /**
1359          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1360          * return the equivalent numeric entity reference (except for the core &lt;
1361          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1362          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1363          * pseudo-entity source (eg &amp;foo;)
1364          *
1365          * @param string $name
1366          * @return string
1367          */
1368         static function normalizeEntity( $name ) {
1369                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1370                         return '&' . self::$htmlEntityAliases[$name] . ';';
1371                 } elseif ( in_array( $name,
1372                 array( 'lt', 'gt', 'amp', 'quot' ) ) ) {
1373                         return "&$name;";
1374                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1375                         return '&#' . self::$htmlEntities[$name] . ';';
1376                 } else {
1377                         return "&amp;$name;";
1378                 }
1379         }
1380
1381         /**
1382          * @param int $codepoint
1383          * @return null|string
1384          */
1385         static function decCharReference( $codepoint ) {
1386                 $point = intval( $codepoint );
1387                 if ( Sanitizer::validateCodepoint( $point ) ) {
1388                         return sprintf( '&#%d;', $point );
1389                 } else {
1390                         return null;
1391                 }
1392         }
1393
1394         /**
1395          * @param int $codepoint
1396          * @return null|string
1397          */
1398         static function hexCharReference( $codepoint ) {
1399                 $point = hexdec( $codepoint );
1400                 if ( Sanitizer::validateCodepoint( $point ) ) {
1401                         return sprintf( '&#x%x;', $point );
1402                 } else {
1403                         return null;
1404                 }
1405         }
1406
1407         /**
1408          * Returns true if a given Unicode codepoint is a valid character in XML.
1409          * @param int $codepoint
1410          * @return bool
1411          */
1412         private static function validateCodepoint( $codepoint ) {
1413                 return $codepoint == 0x09
1414                         || $codepoint == 0x0a
1415                         || $codepoint == 0x0d
1416                         || ( $codepoint >= 0x20 && $codepoint <= 0xd7ff )
1417                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1418                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1419         }
1420
1421         /**
1422          * Decode any character references, numeric or named entities,
1423          * in the text and return a UTF-8 string.
1424          *
1425          * @param string $text
1426          * @return string
1427          */
1428         public static function decodeCharReferences( $text ) {
1429                 return preg_replace_callback(
1430                         self::CHAR_REFS_REGEX,
1431                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1432                         $text );
1433         }
1434
1435         /**
1436          * Decode any character references, numeric or named entities,
1437          * in the next and normalize the resulting string. (bug 14952)
1438          *
1439          * This is useful for page titles, not for text to be displayed,
1440          * MediaWiki allows HTML entities to escape normalization as a feature.
1441          *
1442          * @param string $text Already normalized, containing entities
1443          * @return string Still normalized, without entities
1444          */
1445         public static function decodeCharReferencesAndNormalize( $text ) {
1446                 global $wgContLang;
1447                 $text = preg_replace_callback(
1448                         self::CHAR_REFS_REGEX,
1449                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1450                         $text, /* limit */ -1, $count );
1451
1452                 if ( $count ) {
1453                         return $wgContLang->normalize( $text );
1454                 } else {
1455                         return $text;
1456                 }
1457         }
1458
1459         /**
1460          * @param string $matches
1461          * @return string
1462          */
1463         static function decodeCharReferencesCallback( $matches ) {
1464                 if ( $matches[1] != '' ) {
1465                         return Sanitizer::decodeEntity( $matches[1] );
1466                 } elseif ( $matches[2] != '' ) {
1467                         return Sanitizer::decodeChar( intval( $matches[2] ) );
1468                 } elseif ( $matches[3] != '' ) {
1469                         return Sanitizer::decodeChar( hexdec( $matches[3] ) );
1470                 }
1471                 # Last case should be an ampersand by itself
1472                 return $matches[0];
1473         }
1474
1475         /**
1476          * Return UTF-8 string for a codepoint if that is a valid
1477          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1478          * @param int $codepoint
1479          * @return string
1480          * @private
1481          */
1482         static function decodeChar( $codepoint ) {
1483                 if ( Sanitizer::validateCodepoint( $codepoint ) ) {
1484                         return codepointToUtf8( $codepoint );
1485                 } else {
1486                         return UTF8_REPLACEMENT;
1487                 }
1488         }
1489
1490         /**
1491          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1492          * return the UTF-8 encoding of that character. Otherwise, returns
1493          * pseudo-entity source (eg "&foo;")
1494          *
1495          * @param string $name
1496          * @return string
1497          */
1498         static function decodeEntity( $name ) {
1499                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1500                         $name = self::$htmlEntityAliases[$name];
1501                 }
1502                 if ( isset( self::$htmlEntities[$name] ) ) {
1503                         return codepointToUtf8( self::$htmlEntities[$name] );
1504                 } else {
1505                         return "&$name;";
1506                 }
1507         }
1508
1509         /**
1510          * Fetch the whitelist of acceptable attributes for a given element name.
1511          *
1512          * @param string $element
1513          * @return array
1514          */
1515         static function attributeWhitelist( $element ) {
1516                 $list = Sanitizer::setupAttributeWhitelist();
1517                 return isset( $list[$element] )
1518                         ? $list[$element]
1519                         : array();
1520         }
1521
1522         /**
1523          * Foreach array key (an allowed HTML element), return an array
1524          * of allowed attributes
1525          * @return array
1526          */
1527         static function setupAttributeWhitelist() {
1528                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
1529                 static $whitelist, $staticInitialised;
1530
1531                 $globalContext = implode( '-', compact( 'wgAllowRdfaAttributes', 'wgAllowMicrodataAttributes' ) );
1532
1533                 if ( $whitelist !== null && $staticInitialised == $globalContext ) {
1534                         return $whitelist;
1535                 }
1536
1537                 $common = array(
1538                         # HTML
1539                         'id',
1540                         'class',
1541                         'style',
1542                         'lang',
1543                         'dir',
1544                         'title',
1545
1546                         # WAI-ARIA
1547                         'role',
1548                 );
1549
1550                 if ( $wgAllowRdfaAttributes ) {
1551                         # RDFa attributes as specified in section 9 of
1552                         # http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1553                         $common = array_merge( $common, array(
1554                                 'about', 'property', 'resource', 'datatype', 'typeof',
1555                         ) );
1556                 }
1557
1558                 if ( $wgAllowMicrodataAttributes ) {
1559                         # add HTML5 microdata tags as specified by
1560                         # http://www.whatwg.org/html/microdata.html#the-microdata-model
1561                         $common = array_merge( $common, array(
1562                                 'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1563                         ) );
1564                 }
1565
1566                 $block = array_merge( $common, array( 'align' ) );
1567                 $tablealign = array( 'align', 'valign' );
1568                 $tablecell = array(
1569                         'abbr',
1570                         'axis',
1571                         'headers',
1572                         'scope',
1573                         'rowspan',
1574                         'colspan',
1575                         'nowrap', # deprecated
1576                         'width', # deprecated
1577                         'height', # deprecated
1578                         'bgcolor', # deprecated
1579                 );
1580
1581                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1582                 # See: http://www.w3.org/TR/html4/
1583                 $whitelist = array(
1584                         # 7.5.4
1585                         'div'        => $block,
1586                         'center'     => $common, # deprecated
1587                         'span'       => $common,
1588
1589                         # 7.5.5
1590                         'h1'         => $block,
1591                         'h2'         => $block,
1592                         'h3'         => $block,
1593                         'h4'         => $block,
1594                         'h5'         => $block,
1595                         'h6'         => $block,
1596
1597                         # 7.5.6
1598                         # address
1599
1600                         # 8.2.4
1601                         'bdo'        => $common,
1602
1603                         # 9.2.1
1604                         'em'         => $common,
1605                         'strong'     => $common,
1606                         'cite'       => $common,
1607                         'dfn'        => $common,
1608                         'code'       => $common,
1609                         'samp'       => $common,
1610                         'kbd'        => $common,
1611                         'var'        => $common,
1612                         'abbr'       => $common,
1613                         # acronym
1614
1615                         # 9.2.2
1616                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1617                         'q'          => array_merge( $common, array( 'cite' ) ),
1618
1619                         # 9.2.3
1620                         'sub'        => $common,
1621                         'sup'        => $common,
1622
1623                         # 9.3.1
1624                         'p'          => $block,
1625
1626                         # 9.3.2
1627                         'br'         => array_merge( $common, array( 'clear' ) ),
1628
1629                         # http://www.whatwg.org/html/text-level-semantics.html#the-wbr-element
1630                         'wbr'        => $common,
1631
1632                         # 9.3.4
1633                         'pre'        => array_merge( $common, array( 'width' ) ),
1634
1635                         # 9.4
1636                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1637                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1638
1639                         # 10.2
1640                         'ul'         => array_merge( $common, array( 'type' ) ),
1641                         'ol'         => array_merge( $common, array( 'type', 'start' ) ),
1642                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1643
1644                         # 10.3
1645                         'dl'         => $common,
1646                         'dd'         => $common,
1647                         'dt'         => $common,
1648
1649                         # 11.2.1
1650                         'table'      => array_merge( $common,
1651                                                                 array( 'summary', 'width', 'border', 'frame',
1652                                                                                 'rules', 'cellspacing', 'cellpadding',
1653                                                                                 'align', 'bgcolor',
1654                                                                 ) ),
1655
1656                         # 11.2.2
1657                         'caption'    => $block,
1658
1659                         # 11.2.3
1660                         'thead'      => $common,
1661                         'tfoot'      => $common,
1662                         'tbody'      => $common,
1663
1664                         # 11.2.4
1665                         'colgroup'   => array_merge( $common, array( 'span' ) ),
1666                         'col'        => array_merge( $common, array( 'span' ) ),
1667
1668                         # 11.2.5
1669                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1670
1671                         # 11.2.6
1672                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1673                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1674
1675                         # 12.2
1676                         # NOTE: <a> is not allowed directly, but the attrib
1677                         # whitelist is used from the Parser object
1678                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1679
1680                         # 13.2
1681                         # Not usually allowed, but may be used for extension-style hooks
1682                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1683                         # true
1684                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1685
1686                         # 15.2.1
1687                         'tt'         => $common,
1688                         'b'          => $common,
1689                         'i'          => $common,
1690                         'big'        => $common,
1691                         'small'      => $common,
1692                         'strike'     => $common,
1693                         's'          => $common,
1694                         'u'          => $common,
1695
1696                         # 15.2.2
1697                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1698                         # basefont
1699
1700                         # 15.3
1701                         'hr'         => array_merge( $common, array( 'width' ) ),
1702
1703                         # HTML Ruby annotation text module, simple ruby only.
1704                         # http://www.whatwg.org/html/text-level-semantics.html#the-ruby-element
1705                         'ruby'       => $common,
1706                         # rbc
1707                         'rb'         => $common,
1708                         'rp'         => $common,
1709                         'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),
1710                         'rtc'         => $common,
1711
1712                         # MathML root element, where used for extensions
1713                         # 'title' may not be 100% valid here; it's XHTML
1714                         # http://www.w3.org/TR/REC-MathML/
1715                         'math'       => array( 'class', 'style', 'id', 'title' ),
1716
1717                         # HTML 5 section 4.6
1718                         'bdi' => $common,
1719
1720                         # HTML5 elements, defined by:
1721                         # http://www.whatwg.org/html/
1722                         'data' => array_merge( $common, array( 'value' ) ),
1723                         'time' => array_merge( $common, array( 'datetime' ) ),
1724                         'mark' => $common,
1725
1726                         // meta and link are only permitted by removeHTMLtags when Microdata
1727                         // is enabled so we don't bother adding a conditional to hide these
1728                         // Also meta and link are only valid in WikiText as Microdata elements
1729                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1730                         // So we don't bother including $common attributes that have no purpose.
1731                         'meta' => array( 'itemprop', 'content' ),
1732                         'link' => array( 'itemprop', 'href' ),
1733                 );
1734
1735                 $staticInitialised = $globalContext;
1736
1737                 return $whitelist;
1738         }
1739
1740         /**
1741          * Take a fragment of (potentially invalid) HTML and return
1742          * a version with any tags removed, encoded as plain text.
1743          *
1744          * Warning: this return value must be further escaped for literal
1745          * inclusion in HTML output as of 1.10!
1746          *
1747          * @param string $text HTML fragment
1748          * @return string
1749          */
1750         static function stripAllTags( $text ) {
1751                 # Actual <tags>
1752                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1753
1754                 # Normalize &entities and whitespace
1755                 $text = self::decodeCharReferences( $text );
1756                 $text = self::normalizeWhitespace( $text );
1757
1758                 return $text;
1759         }
1760
1761         /**
1762          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1763          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1764          * PHP 5.1 doesn't.
1765          *
1766          * Use for passing XHTML fragments to PHP's XML parsing functions
1767          *
1768          * @return string
1769          */
1770         static function hackDocType() {
1771                 $out = "<!DOCTYPE html [\n";
1772                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
1773                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1774                 }
1775                 $out .= "]>\n";
1776                 return $out;
1777         }
1778
1779         /**
1780          * @param string $url
1781          * @return mixed|string
1782          */
1783         static function cleanUrl( $url ) {
1784                 # Normalize any HTML entities in input. They will be
1785                 # re-escaped by makeExternalLink().
1786                 $url = Sanitizer::decodeCharReferences( $url );
1787
1788                 # Escape any control characters introduced by the above step
1789                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1790                         array( __CLASS__, 'cleanUrlCallback' ), $url );
1791
1792                 # Validate hostname portion
1793                 $matches = array();
1794                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1795                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1796
1797                         // Characters that will be ignored in IDNs.
1798                         // http://tools.ietf.org/html/3454#section-3.1
1799                         // Strip them before further processing so blacklists and such work.
1800                         $strip = "/
1801                                 \\s|          # general whitespace
1802                                 \xc2\xad|     # 00ad SOFT HYPHEN
1803                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1804                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1805                                 \xe2\x81\xa0| # 2060 WORD JOINER
1806                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1807                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1808                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1809                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1810                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1811                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1812                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1813                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
1814                                 /xuD";
1815
1816                         $host = preg_replace( $strip, '', $host );
1817
1818                         // @todo FIXME: Validate hostnames here
1819
1820                         return $protocol . $host . $rest;
1821                 } else {
1822                         return $url;
1823                 }
1824         }
1825
1826         /**
1827          * @param array $matches
1828          * @return string
1829          */
1830         static function cleanUrlCallback( $matches ) {
1831                 return urlencode( $matches[0] );
1832         }
1833
1834         /**
1835          * Does a string look like an e-mail address?
1836          *
1837          * This validates an email address using an HTML5 specification found at:
1838          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
1839          * Which as of 2011-01-24 says:
1840          *
1841          *   A valid e-mail address is a string that matches the ABNF production
1842          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1843          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1844          *   3.5.
1845          *
1846          * This function is an implementation of the specification as requested in
1847          * bug 22449.
1848          *
1849          * Client-side forms will use the same standard validation rules via JS or
1850          * HTML 5 validation; additional restrictions can be enforced server-side
1851          * by extensions via the 'isValidEmailAddr' hook.
1852          *
1853          * Note that this validation doesn't 100% match RFC 2822, but is believed
1854          * to be liberal enough for wide use. Some invalid addresses will still
1855          * pass validation here.
1856          *
1857          * @since 1.18
1858          *
1859          * @param string $addr E-mail address
1860          * @return bool
1861          */
1862         public static function validateEmail( $addr ) {
1863                 $result = null;
1864                 if ( !wfRunHooks( 'isValidEmailAddr', array( $addr, &$result ) ) ) {
1865                         return $result;
1866                 }
1867
1868                 // Please note strings below are enclosed in brackets [], this make the
1869                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1870                 // See bug 26948
1871                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
1872                 $rfc1034_ldh_str = "a-z0-9\\-";
1873
1874                 $html5_email_regexp = "/
1875                 ^                      # start of string
1876                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1877                 @                      # 'apostrophe'
1878                 [$rfc1034_ldh_str]+       # First domain part
1879                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1880                 $                      # End of string
1881                 /ix"; // case Insensitive, eXtended
1882
1883                 return (bool)preg_match( $html5_email_regexp, $addr );
1884         }
1885 }