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 $attribsRegex;
 326
 327         /**
 328          * Regular expression to match HTML/XML attribute pairs within a tag.
 329          * Allows some... latitude.
 330          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 331          */
 332         static function getAttribsRegex() {
 333                 if ( self::$attribsRegex === null ) {
 334                         $attribFirst = '[:A-Z_a-z0-9]';
 335                         $attrib = '[:A-Z_a-z-.0-9]';
 336                         $space = '[\x09\x0a\x0d\x20]';
 337                         self::$attribsRegex =
 338                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 339                                   ($space*=$space*
 340                                         (?:
 341                                          # The attribute value: quoted or alone
 342                                           \"([^<\"]*)\"
 343                                          | '([^<']*)'
 344                                          |  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)
 345                                          |  (\#[0-9a-fA-F]+) # Technically wrong, but lots of
 346                                                                                  # colors are specified like this.
 347                                                                                  # We'll be normalizing it.
 348                                         )
 349                                 )?(?=$space|\$)/sx";
 350                 }
 351                 return self::$attribsRegex;
 352         }
 353
 354         /**
 355          * Cleans up HTML, removes dangerous tags and attributes, and
 356          * removes HTML comments
 357          * @private
 358          * @param string $text
 359          * @param callable $processCallback Callback to do any variable or parameter
 360          *   replacements in HTML attribute values
 361          * @param array|bool $args Arguments for the processing callback
 362          * @param array $extratags For any extra tags to include
 363          * @param array $removetags For any tags (default or extra) to exclude
 364          * @return string
 365          */
 366         static function removeHTMLtags( $text, $processCallback = null,
 367                 $args = array(), $extratags = array(), $removetags = array()
 368         ) {
 369                 global $wgUseTidy, $wgAllowMicrodataAttributes, $wgAllowImageTag;
 370
 371                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 372                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 373
 374                 wfProfileIn( __METHOD__ );
 375
 376                 // Base our staticInitialised variable off of the global config state so that if the globals
 377                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 378                 $globalContext = implode( '-', compact( 'wgAllowMicrodataAttributes', 'wgAllowImageTag' ) );
 379                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 380
 381                         $htmlpairsStatic = array( # Tags that must be closed
 382                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 383                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 384                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 385                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 386                                 'ruby', 'rt', 'rb', 'rp', 'p', 'span', 'abbr', 'dfn',
 387                                 'kbd', 'samp', 'data', 'time', 'mark'
 388                         );
 389                         $htmlsingle = array(
 390                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd'
 391                         );
 392                         $htmlsingleonly = array( # Elements that cannot have close tags
 393                                 'br', 'wbr', 'hr'
 394                         );
 395                         if ( $wgAllowMicrodataAttributes ) {
 396                                 $htmlsingle[] = $htmlsingleonly[] = 'meta';
 397                                 $htmlsingle[] = $htmlsingleonly[] = 'link';
 398                         }
 399                         $htmlnest = array( # Tags that can be nested--??
 400                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 401                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 402                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 403                         );
 404                         $tabletags = array( # Can only appear inside table, we will close them
 405                                 'td', 'th', 'tr',
 406                         );
 407                         $htmllist = array( # Tags used by list
 408                                 'ul', 'ol',
 409                         );
 410                         $listtags = array( # Tags that can appear in a list
 411                                 'li',
 412                         );
 413
 414                         if ( $wgAllowImageTag ) {
 415                                 $htmlsingle[] = 'img';
 416                                 $htmlsingleonly[] = 'img';
 417                         }
 418
 419                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 420                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 421
 422                         # Convert them all to hashtables for faster lookup
 423                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 424                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 425                         foreach ( $vars as $var ) {
 426                                 $$var = array_flip( $$var );
 427                         }
 428                         $staticInitialised = $globalContext;
 429                 }
 430                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 431                 $extratags = array_flip( $extratags );
 432                 $removetags = array_flip( $removetags );
 433                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 434                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 435
 436                 # Remove HTML comments
 437                 $text = Sanitizer::removeHTMLcomments( $text );
 438                 $bits = explode( '<', $text );
 439                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 440                 if ( !$wgUseTidy ) {
 441                         $tagstack = $tablestack = array();
 442                         foreach ( $bits as $x ) {
 443                                 $regs = array();
 444                                 # $slash: Does the current element start with a '/'?
 445                                 # $t: Current element name
 446                                 # $params: String between element name and >
 447                                 # $brace: Ending '>' or '/>'
 448                                 # $rest: Everything until the next element of $bits
 449                                 if ( preg_match( '!^(/?)([^\\s/>]+)([^>]*?)(/{0,1}>)([^<]*)$!', $x, $regs ) ) {
 450                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 451                                 } else {
 452                                         $slash = $t = $params = $brace = $rest = null;
 453                                 }
 454
 455                                 $badtag = false;
 456                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 457                                         # Check our stack
 458                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 459                                                 $badtag = true;
 460                                         } elseif ( $slash ) {
 461                                                 # Closing a tag... is it the one we just opened?
 462                                                 wfSuppressWarnings();
 463                                                 $ot = array_pop( $tagstack );
 464                                                 wfRestoreWarnings();
 465
 466                                                 if ( $ot != $t ) {
 467                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 468                                                                 # Pop all elements with an optional close tag
 469                                                                 # and see if we find a match below them
 470                                                                 $optstack = array();
 471                                                                 array_push( $optstack, $ot );
 472                                                                 wfSuppressWarnings();
 473                                                                 $ot = array_pop( $tagstack );
 474                                                                 wfRestoreWarnings();
 475                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 476                                                                         array_push( $optstack, $ot );
 477                                                                         wfSuppressWarnings();
 478                                                                         $ot = array_pop( $tagstack );
 479                                                                         wfRestoreWarnings();
 480                                                                 }
 481                                                                 if ( $t != $ot ) {
 482                                                                         # No match. Push the optional elements back again
 483                                                                         $badtag = true;
 484                                                                         wfSuppressWarnings();
 485                                                                         $ot = array_pop( $optstack );
 486                                                                         wfRestoreWarnings();
 487                                                                         while ( $ot ) {
 488                                                                                 array_push( $tagstack, $ot );
 489                                                                                 wfSuppressWarnings();
 490                                                                                 $ot = array_pop( $optstack );
 491                                                                                 wfRestoreWarnings();
 492                                                                         }
 493                                                                 }
 494                                                         } else {
 495                                                                 wfSuppressWarnings();
 496                                                                 array_push( $tagstack, $ot );
 497                                                                 wfRestoreWarnings();
 498
 499                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 500                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 501                                                                         $badtag = true;
 502                                                                 }
 503                                                         }
 504                                                 } else {
 505                                                         if ( $t == 'table' ) {
 506                                                                 $tagstack = array_pop( $tablestack );
 507                                                         }
 508                                                 }
 509                                                 $newparams = '';
 510                                         } else {
 511                                                 # Keep track for later
 512                                                 if ( isset( $tabletags[$t] ) &&
 513                                                 !in_array( 'table', $tagstack ) ) {
 514                                                         $badtag = true;
 515                                                 } elseif ( in_array( $t, $tagstack ) &&
 516                                                 !isset( $htmlnest[$t] ) ) {
 517                                                         $badtag = true;
 518                                                 # Is it a self closed htmlpair ? (bug 5487)
 519                                                 } elseif ( $brace == '/>' &&
 520                                                 isset( $htmlpairs[$t] ) ) {
 521                                                         $badtag = true;
 522                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 523                                                         # Hack to force empty tag for unclosable elements
 524                                                         $brace = '/>';
 525                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 526                                                         # Hack to not close $htmlsingle tags
 527                                                         $brace = null;
 528                                                         # Still need to push this optionally-closed tag to
 529                                                         # the tag stack so that we can match end tags
 530                                                         # instead of marking them as bad.
 531                                                         array_push( $tagstack, $t );
 532                                                 } elseif ( isset( $tabletags[$t] )
 533                                                 && in_array( $t, $tagstack ) ) {
 534                                                         // New table tag but forgot to close the previous one
 535                                                         $text .= "</$t>";
 536                                                 } else {
 537                                                         if ( $t == 'table' ) {
 538                                                                 array_push( $tablestack, $tagstack );
 539                                                                 $tagstack = array();
 540                                                         }
 541                                                         array_push( $tagstack, $t );
 542                                                 }
 543
 544                                                 # Replace any variables or template parameters with
 545                                                 # plaintext results.
 546                                                 if ( is_callable( $processCallback ) ) {
 547                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 548                                                 }
 549
 550                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 551                                                         $badtag = true;
 552                                                 }
 553
 554                                                 # Strip non-approved attributes from the tag
 555                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 556                                         }
 557                                         if ( !$badtag ) {
 558                                                 $rest = str_replace( '>', '&gt;', $rest );
 559                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 560                                                 $text .= "<$slash$t$newparams$close>$rest";
 561                                                 continue;
 562                                         }
 563                                 }
 564                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 565                         }
 566                         # Close off any remaining tags
 567                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 568                                 $text .= "</$t>\n";
 569                                 if ( $t == 'table' ) {
 570                                         $tagstack = array_pop( $tablestack );
 571                                 }
 572                         }
 573                 } else {
 574                         # this might be possible using tidy itself
 575                         foreach ( $bits as $x ) {
 576                                 preg_match(
 577                                         '/^(\\/?)(\\w+)([^>]*?)(\\/{0,1}>)([^<]*)$/',
 578                                         $x,
 579                                         $regs
 580                                 );
 581
 582                                 wfSuppressWarnings();
 583                                 list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 584                                 wfRestoreWarnings();
 585
 586                                 $badtag = false;
 587                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 588                                         if ( is_callable( $processCallback ) ) {
 589                                                 call_user_func_array( $processCallback, array( &$params, $args ) );
 590                                         }
 591
 592                                         if ( !Sanitizer::validateTag( $params, $t ) ) {
 593                                                 $badtag = true;
 594                                         }
 595
 596                                         $newparams = Sanitizer::fixTagAttributes( $params, $t );
 597                                         if ( !$badtag ) {
 598                                                 $rest = str_replace( '>', '&gt;', $rest );
 599                                                 $text .= "<$slash$t$newparams$brace$rest";
 600                                                 continue;
 601                                         }
 602                                 }
 603                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 604                         }
 605                 }
 606                 wfProfileOut( __METHOD__ );
 607                 return $text;
 608         }
 609
 610         /**
 611          * Remove '<!--', '-->', and everything between.
 612          * To avoid leaving blank lines, when a comment is both preceded
 613          * and followed by a newline (ignoring spaces), trim leading and
 614          * trailing spaces and one of the newlines.
 615          *
 616          * @private
 617          * @param string $text
 618          * @return string
 619          */
 620         static function removeHTMLcomments( $text ) {
 621                 wfProfileIn( __METHOD__ );
 622                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 623                         $end = strpos( $text, '-->', $start + 4 );
 624                         if ( $end === false ) {
 625                                 # Unterminated comment; bail out
 626                                 break;
 627                         }
 628
 629                         $end += 3;
 630
 631                         # Trim space and newline if the comment is both
 632                         # preceded and followed by a newline
 633                         $spaceStart = max( $start - 1, 0 );
 634                         $spaceLen = $end - $spaceStart;
 635                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 636                                 $spaceStart--;
 637                                 $spaceLen++;
 638                         }
 639                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 640                                 $spaceLen++;
 641                         }
 642                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 643                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 644                                 # Remove the comment, leading and trailing
 645                                 # spaces, and leave only one newline.
 646                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 647                         } else {
 648                                 # Remove just the comment.
 649                                 $text = substr_replace( $text, '', $start, $end - $start );
 650                         }
 651                 }
 652                 wfProfileOut( __METHOD__ );
 653                 return $text;
 654         }
 655
 656         /**
 657          * Takes attribute names and values for a tag and the tag name and
 658          * validates that the tag is allowed to be present.
 659          * This DOES NOT validate the attributes, nor does it validate the
 660          * tags themselves. This method only handles the special circumstances
 661          * where we may want to allow a tag within content but ONLY when it has
 662          * specific attributes set.
 663          *
 664          * @param string $params
 665          * @param string $element
 666          * @return bool
 667          */
 668         static function validateTag( $params, $element ) {
 669                 $params = Sanitizer::decodeTagAttributes( $params );
 670
 671                 if ( $element == 'meta' || $element == 'link' ) {
 672                         if ( !isset( $params['itemprop'] ) ) {
 673                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 674                                 return false;
 675                         }
 676                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 677                                 // <meta> must have a content="" for the itemprop
 678                                 return false;
 679                         }
 680                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 681                                 // <link> must have an associated href=""
 682                                 return false;
 683                         }
 684                 }
 685
 686                 return true;
 687         }
 688
 689         /**
 690          * Take an array of attribute names and values and normalize or discard
 691          * illegal values for the given element type.
 692          *
 693          * - Discards attributes not on a whitelist for the given element
 694          * - Unsafe style attributes are discarded
 695          * - Invalid id attributes are re-encoded
 696          *
 697          * @param array $attribs
 698          * @param string $element
 699          * @return array
 700          *
 701          * @todo Check for legal values where the DTD limits things.
 702          * @todo Check for unique id attribute :P
 703          */
 704         static function validateTagAttributes( $attribs, $element ) {
 705                 return Sanitizer::validateAttributes( $attribs,
 706                         Sanitizer::attributeWhitelist( $element ) );
 707         }
 708
 709         /**
 710          * Take an array of attribute names and values and normalize or discard
 711          * illegal values for the given whitelist.
 712          *
 713          * - Discards attributes not the given whitelist
 714          * - Unsafe style attributes are discarded
 715          * - Invalid id attributes are re-encoded
 716          *
 717          * @param array $attribs
 718          * @param array $whitelist list of allowed attribute names
 719          * @return array
 720          *
 721          * @todo Check for legal values where the DTD limits things.
 722          * @todo Check for unique id attribute :P
 723          */
 724         static function validateAttributes( $attribs, $whitelist ) {
 725                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 726
 727                 $whitelist = array_flip( $whitelist );
 728                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 729
 730                 $out = array();
 731                 foreach ( $attribs as $attribute => $value ) {
 732                         #allow XML namespace declaration if RDFa is enabled
 733                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 734                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 735                                         $out[$attribute] = $value;
 736                                 }
 737
 738                                 continue;
 739                         }
 740
 741                         # Allow any attribute beginning with "data-"
 742                         if ( !preg_match( '/^data-/i', $attribute ) && !isset( $whitelist[$attribute] ) ) {
 743                                 continue;
 744                         }
 745
 746                         # Strip javascript "expression" from stylesheets.
 747                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 748                         if ( $attribute == 'style' ) {
 749                                 $value = Sanitizer::checkCss( $value );
 750                         }
 751
 752                         if ( $attribute === 'id' ) {
 753                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 754                         }
 755
 756                         # WAI-ARIA
 757                         # http://www.w3.org/TR/wai-aria/
 758                         # http://www.whatwg.org/html/elements.html#wai-aria
 759                         # For now we only support role="presentation" until we work out what roles should be
 760                         # usable by content and we ensure that our code explicitly rejects patterns that
 761                         # violate HTML5's ARIA restrictions.
 762                         if ( $attribute === 'role' && $value !== 'presentation' ) {
 763                                 continue;
 764                         }
 765
 766                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 767                         // Check them for sanity.
 768                         if ( $attribute === 'rel' || $attribute === 'rev'
 769                                 # RDFa
 770                                 || $attribute === 'about' || $attribute === 'property'
 771                                 || $attribute === 'resource' || $attribute === 'datatype'
 772                                 || $attribute === 'typeof'
 773                                 # HTML5 microdata
 774                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 775                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 776                                 || $attribute === 'itemtype'
 777                         ) {
 778                                 //Paranoia. Allow "simple" values but suppress javascript
 779                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 780                                         continue;
 781                                 }
 782                         }
 783
 784                         # NOTE: even though elements using href/src are not allowed directly, supply
 785                         #       validation code that can be used by tag hook handlers, etc
 786                         if ( $attribute === 'href' || $attribute === 'src' ) {
 787                                 if ( !preg_match( $hrefExp, $value ) ) {
 788                                         continue; //drop any href or src attributes not using an allowed protocol.
 789                                         // NOTE: this also drops all relative URLs
 790                                 }
 791                         }
 792
 793                         // If this attribute was previously set, override it.
 794                         // Output should only have one attribute of each name.
 795                         $out[$attribute] = $value;
 796                 }
 797
 798                 if ( $wgAllowMicrodataAttributes ) {
 799                         # itemtype, itemid, itemref don't make sense without itemscope
 800                         if ( !array_key_exists( 'itemscope', $out ) ) {
 801                                 unset( $out['itemtype'] );
 802                                 unset( $out['itemid'] );
 803                                 unset( $out['itemref'] );
 804                         }
 805                         # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 806                 }
 807                 return $out;
 808         }
 809
 810         /**
 811          * Merge two sets of HTML attributes.  Conflicting items in the second set
 812          * will override those in the first, except for 'class' attributes which
 813          * will be combined (if they're both strings).
 814          *
 815          * @todo implement merging for other attributes such as style
 816          * @param array $a
 817          * @param array $b
 818          * @return array
 819          */
 820         static function mergeAttributes( $a, $b ) {
 821                 $out = array_merge( $a, $b );
 822                 if ( isset( $a['class'] ) && isset( $b['class'] )
 823                         && is_string( $a['class'] ) && is_string( $b['class'] )
 824                         && $a['class'] !== $b['class']
 825                 ) {
 826                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 827                                 -1, PREG_SPLIT_NO_EMPTY );
 828                         $out['class'] = implode( ' ', array_unique( $classes ) );
 829                 }
 830                 return $out;
 831         }
 832
 833         /**
 834          * Pick apart some CSS and check it for forbidden or unsafe structures.
 835          * Returns a sanitized string. This sanitized string will have
 836          * character references and escape sequences decoded and comments
 837          * stripped (unless it is itself one valid comment, in which case the value
 838          * will be passed through). If the input is just too evil, only a comment
 839          * complaining about evilness will be returned.
 840          *
 841          * Currently URL references, 'expression', 'tps' are forbidden.
 842          *
 843          * NOTE: Despite the fact that character references are decoded, the
 844          * returned string may contain character references given certain
 845          * clever input strings. These character references must
 846          * be escaped before the return value is embedded in HTML.
 847          *
 848          * @param string $value
 849          * @return string
 850          */
 851         static function checkCss( $value ) {
 852                 // Decode character references like &#123;
 853                 $value = Sanitizer::decodeCharReferences( $value );
 854
 855                 // Decode escape sequences and line continuation
 856                 // See the grammar in the CSS 2 spec, appendix D.
 857                 // This has to be done AFTER decoding character references.
 858                 // This means it isn't possible for this function to return
 859                 // unsanitized escape sequences. It is possible to manufacture
 860                 // input that contains character references that decode to
 861                 // escape sequences that decode to character references, but
 862                 // it's OK for the return value to contain character references
 863                 // because the caller is supposed to escape those anyway.
 864                 static $decodeRegex;
 865                 if ( !$decodeRegex ) {
 866                         $space = '[\\x20\\t\\r\\n\\f]';
 867                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 868                         $backslash = '\\\\';
 869                         $decodeRegex = "/ $backslash
 870                                 (?:
 871                                         ($nl) |  # 1. Line continuation
 872                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 873                                         (.) | # 3. backslash cancelling special meaning
 874                                         () | # 4. backslash at end of string
 875                                 )/xu";
 876                 }
 877                 $value = preg_replace_callback( $decodeRegex,
 878                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 879
 880                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 881                 $value = preg_replace_callback(
 882                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (bug 58088)
 883                         function ( $matches ) {
 884                                 $cp = utf8ToCodepoint( $matches[0] );
 885                                 if ( $cp === false ) {
 886                                         return '';
 887                                 }
 888                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 889                         },
 890                         $value
 891                 );
 892
 893                 // Convert more characters IE6 might treat as ascii
 894                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 895                 $value = str_replace(
 896                         array( 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ),
 897                         array( 'r', 'n', 'n', 'l', 'i', '(', '(' ),
 898                         $value
 899                 );
 900
 901                 // Let the value through if it's nothing but a single comment, to
 902                 // allow other functions which may reject it to pass some error
 903                 // message through.
 904                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 905                         // Remove any comments; IE gets token splitting wrong
 906                         // This must be done AFTER decoding character references and
 907                         // escape sequences, because those steps can introduce comments
 908                         // This step cannot introduce character references or escape
 909                         // sequences, because it replaces comments with spaces rather
 910                         // than removing them completely.
 911                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 912
 913                         // Remove anything after a comment-start token, to guard against
 914                         // incorrect client implementations.
 915                         $commentPos = strpos( $value, '/*' );
 916                         if ( $commentPos !== false ) {
 917                                 $value = substr( $value, 0, $commentPos );
 918                         }
 919                 }
 920
 921                 // S followed by repeat, iteration, or prolonged sound marks,
 922                 // which IE will treat as "ss"
 923                 $value = preg_replace(
 924                         '/s(?:
 925                                 \xE3\x80\xB1 | # U+3031
 926                                 \xE3\x82\x9D | # U+309D
 927                                 \xE3\x83\xBC | # U+30FC
 928                                 \xE3\x83\xBD | # U+30FD
 929                                 \xEF\xB9\xBC | # U+FE7C
 930                                 \xEF\xB9\xBD | # U+FE7D
 931                                 \xEF\xBD\xB0   # U+FF70
 932                         )/ix',
 933                         'ss',
 934                         $value
 935                 );
 936
 937                 // Reject problematic keywords and control characters
 938                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ) {
 939                         return '/* invalid control char */';
 940                 } elseif ( preg_match(
 941                         '! expression
 942                                 | filter\s*:
 943                                 | accelerator\s*:
 944                                 | -o-link\s*:
 945                                 | -o-link-source\s*:
 946                                 | -o-replace\s*:
 947                                 | url\s*\(
 948                                 | image\s*\(
 949                                 | image-set\s*\(
 950                         !ix', $value ) ) {
 951                         return '/* insecure input */';
 952                 }
 953                 return $value;
 954         }
 955
 956         /**
 957          * @param array $matches
 958          * @return string
 959          */
 960         static function cssDecodeCallback( $matches ) {
 961                 if ( $matches[1] !== '' ) {
 962                         // Line continuation
 963                         return '';
 964                 } elseif ( $matches[2] !== '' ) {
 965                         $char = codepointToUtf8( hexdec( $matches[2] ) );
 966                 } elseif ( $matches[3] !== '' ) {
 967                         $char = $matches[3];
 968                 } else {
 969                         $char = '\\';
 970                 }
 971                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
 972                         // These characters need to be escaped in strings
 973                         // Clean up the escape sequence to avoid parsing errors by clients
 974                         return '\\' . dechex( ord( $char ) ) . ' ';
 975                 } else {
 976                         // Decode unnecessary escape
 977                         return $char;
 978                 }
 979         }
 980
 981         /**
 982          * Take a tag soup fragment listing an HTML element's attributes
 983          * and normalize it to well-formed XML, discarding unwanted attributes.
 984          * Output is safe for further wikitext processing, with escaping of
 985          * values that could trigger problems.
 986          *
 987          * - Normalizes attribute names to lowercase
 988          * - Discards attributes not on a whitelist for the given element
 989          * - Turns broken or invalid entities into plaintext
 990          * - Double-quotes all attribute values
 991          * - Attributes without values are given the name as attribute
 992          * - Double attributes are discarded
 993          * - Unsafe style attributes are discarded
 994          * - Prepends space if there are attributes.
 995          *
 996          * @param string $text
 997          * @param string $element
 998          * @return string
 999          */
1000         static function fixTagAttributes( $text, $element ) {
1001                 if ( trim( $text ) == '' ) {
1002                         return '';
1003                 }
1004
1005                 $decoded = Sanitizer::decodeTagAttributes( $text );
1006                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
1007
1008                 return Sanitizer::safeEncodeTagAttributes( $stripped );
1009         }
1010
1011         /**
1012          * Encode an attribute value for HTML output.
1013          * @param string $text
1014          * @return string HTML-encoded text fragment
1015          */
1016         static function encodeAttribute( $text ) {
1017                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1018
1019                 // Whitespace is normalized during attribute decoding,
1020                 // so if we've been passed non-spaces we must encode them
1021                 // ahead of time or they won't be preserved.
1022                 $encValue = strtr( $encValue, array(
1023                         "\n" => '&#10;',
1024                         "\r" => '&#13;',
1025                         "\t" => '&#9;',
1026                 ) );
1027
1028                 return $encValue;
1029         }
1030
1031         /**
1032          * Encode an attribute value for HTML tags, with extra armoring
1033          * against further wiki processing.
1034          * @param string $text
1035          * @return string HTML-encoded text fragment
1036          */
1037         static function safeEncodeAttribute( $text ) {
1038                 $encValue = Sanitizer::encodeAttribute( $text );
1039
1040                 # Templates and links may be expanded in later parsing,
1041                 # creating invalid or dangerous output. Suppress this.
1042                 $encValue = strtr( $encValue, array(
1043                         '<'    => '&lt;',   // This should never happen,
1044                         '>'    => '&gt;',   // we've received invalid input
1045                         '"'    => '&quot;', // which should have been escaped.
1046                         '{'    => '&#123;',
1047                         '['    => '&#91;',
1048                         "''"   => '&#39;&#39;',
1049                         'ISBN' => '&#73;SBN',
1050                         'RFC'  => '&#82;FC',
1051                         'PMID' => '&#80;MID',
1052                         '|'    => '&#124;',
1053                         '__'   => '&#95;_',
1054                 ) );
1055
1056                 # Stupid hack
1057                 $encValue = preg_replace_callback(
1058                         '/((?i)' . wfUrlProtocols() . ')/',
1059                         array( 'Sanitizer', 'armorLinksCallback' ),
1060                         $encValue );
1061                 return $encValue;
1062         }
1063
1064         /**
1065          * Given a value, escape it so that it can be used in an id attribute and
1066          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1067          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1068          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1069          * escaped with lots of dots.
1070          *
1071          * To ensure we don't have to bother escaping anything, we also strip ', ",
1072          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1073          * We also strip # because it upsets IE, and % because it could be
1074          * ambiguous if it's part of something that looks like a percent escape
1075          * (which don't work reliably in fragments cross-browser).
1076          *
1077          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
1078          *   in the id and name attributes
1079          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1080          *   the id attribute
1081          * @see http://www.whatwg.org/html/elements.html#the-id-attribute
1082          *   HTML5 definition of id attribute
1083          *
1084          * @param string $id id to escape
1085          * @param string|array $options String or array of strings (default is array()):
1086          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1087          *       so don't pay attention if the first character isn't valid at the
1088          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1089          *       false.
1090          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1091          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1092          *       anchors and links won't break.
1093          * @return string
1094          */
1095         static function escapeId( $id, $options = array() ) {
1096                 global $wgExperimentalHtmlIds;
1097                 $options = (array)$options;
1098
1099                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1100                         $id = Sanitizer::decodeCharReferences( $id );
1101                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1102                         $id = trim( $id, '_' );
1103                         if ( $id === '' ) {
1104                                 # Must have been all whitespace to start with.
1105                                 return '_';
1106                         } else {
1107                                 return $id;
1108                         }
1109                 }
1110
1111                 # HTML4-style escaping
1112                 static $replace = array(
1113                         '%3A' => ':',
1114                         '%' => '.'
1115                 );
1116
1117                 $id = urlencode( Sanitizer::decodeCharReferences( strtr( $id, ' ', '_' ) ) );
1118                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1119
1120                 if ( !preg_match( '/^[a-zA-Z]/', $id )
1121                 && !in_array( 'noninitial', $options ) ) {
1122                         // Initial character must be a letter!
1123                         $id = "x$id";
1124                 }
1125                 return $id;
1126         }
1127
1128         /**
1129          * Given a value, escape it so that it can be used as a CSS class and
1130          * return it.
1131          *
1132          * @todo For extra validity, input should be validated UTF-8.
1133          *
1134          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1135          *
1136          * @param string $class
1137          * @return string
1138          */
1139         static function escapeClass( $class ) {
1140                 // Convert ugly stuff to underscores and kill underscores in ugly places
1141                 return rtrim( preg_replace(
1142                         array( '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ),
1143                         '_',
1144                         $class ), '_' );
1145         }
1146
1147         /**
1148          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1149          * This allows (generally harmless) entities like &#160; to survive.
1150          *
1151          * @param string $html HTML to escape
1152          * @return string Escaped input
1153          */
1154         static function escapeHtmlAllowEntities( $html ) {
1155                 $html = Sanitizer::decodeCharReferences( $html );
1156                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1157                 # hurt.
1158                 $html = htmlspecialchars( $html, ENT_QUOTES );
1159                 return $html;
1160         }
1161
1162         /**
1163          * Regex replace callback for armoring links against further processing.
1164          * @param array $matches
1165          * @return string
1166          */
1167         private static function armorLinksCallback( $matches ) {
1168                 return str_replace( ':', '&#58;', $matches[1] );
1169         }
1170
1171         /**
1172          * Return an associative array of attribute names and values from
1173          * a partial tag string. Attribute names are forces to lowercase,
1174          * character references are decoded to UTF-8 text.
1175          *
1176          * @param string $text
1177          * @return array
1178          */
1179         public static function decodeTagAttributes( $text ) {
1180                 if ( trim( $text ) == '' ) {
1181                         return array();
1182                 }
1183
1184                 $attribs = array();
1185                 $pairs = array();
1186                 if ( !preg_match_all(
1187                         self::getAttribsRegex(),
1188                         $text,
1189                         $pairs,
1190                         PREG_SET_ORDER ) ) {
1191                         return $attribs;
1192                 }
1193
1194                 foreach ( $pairs as $set ) {
1195                         $attribute = strtolower( $set[1] );
1196                         $value = Sanitizer::getTagAttributeCallback( $set );
1197
1198                         // Normalize whitespace
1199                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1200                         $value = trim( $value );
1201
1202                         // Decode character references
1203                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1204                 }
1205                 return $attribs;
1206         }
1207
1208         /**
1209          * Build a partial tag string from an associative array of attribute
1210          * names and values as returned by decodeTagAttributes.
1211          *
1212          * @param array $assoc_array
1213          * @return string
1214          */
1215         public static function safeEncodeTagAttributes( $assoc_array ) {
1216                 $attribs = array();
1217                 foreach ( $assoc_array as $attribute => $value ) {
1218                         $encAttribute = htmlspecialchars( $attribute );
1219                         $encValue = Sanitizer::safeEncodeAttribute( $value );
1220
1221                         $attribs[] = "$encAttribute=\"$encValue\"";
1222                 }
1223                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1224         }
1225
1226         /**
1227          * Pick the appropriate attribute value from a match set from the
1228          * attribs regex matches.
1229          *
1230          * @param array $set
1231          * @throws MWException when tag conditions are not met.
1232          * @return string
1233          */
1234         private static function getTagAttributeCallback( $set ) {
1235                 if ( isset( $set[6] ) ) {
1236                         # Illegal #XXXXXX color with no quotes.
1237                         return $set[6];
1238                 } elseif ( isset( $set[5] ) ) {
1239                         # No quotes.
1240                         return $set[5];
1241                 } elseif ( isset( $set[4] ) ) {
1242                         # Single-quoted
1243                         return $set[4];
1244                 } elseif ( isset( $set[3] ) ) {
1245                         # Double-quoted
1246                         return $set[3];
1247                 } elseif ( !isset( $set[2] ) ) {
1248                         # In XHTML, attributes must have a value.
1249                         # For 'reduced' form, return explicitly the attribute name here.
1250                         return $set[1];
1251                 } else {
1252                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1253                 }
1254         }
1255
1256         /**
1257          * Normalize whitespace and character references in an XML source-
1258          * encoded text for an attribute value.
1259          *
1260          * See http://www.w3.org/TR/REC-xml/#AVNormalize for background,
1261          * but note that we're not returning the value, but are returning
1262          * XML source fragments that will be slapped into output.
1263          *
1264          * @param string $text
1265          * @return string
1266          * @todo Remove, unused?
1267          */
1268         private static function normalizeAttributeValue( $text ) {
1269                 return str_replace( '"', '&quot;',
1270                         self::normalizeWhitespace(
1271                                 Sanitizer::normalizeCharReferences( $text ) ) );
1272         }
1273
1274         /**
1275          * @param string $text
1276          * @return string
1277          */
1278         private static function normalizeWhitespace( $text ) {
1279                 return preg_replace(
1280                         '/\r\n|[\x20\x0d\x0a\x09]/',
1281                         ' ',
1282                         $text );
1283         }
1284
1285         /**
1286          * Normalizes whitespace in a section name, such as might be returned
1287          * by Parser::stripSectionName(), for use in the id's that are used for
1288          * section links.
1289          *
1290          * @param string $section
1291          * @return string
1292          */
1293         static function normalizeSectionNameWhitespace( $section ) {
1294                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1295         }
1296
1297         /**
1298          * Ensure that any entities and character references are legal
1299          * for XML and XHTML specifically. Any stray bits will be
1300          * &amp;-escaped to result in a valid text fragment.
1301          *
1302          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1303          *   numericized (this way we're well-formed even without a DTD)
1304          * b. any numeric char refs must be legal chars, not invalid or forbidden
1305          * c. use lower cased "&#x", not "&#X"
1306          * d. fix or reject non-valid attributes
1307          *
1308          * @param string $text
1309          * @return string
1310          * @private
1311          */
1312         static function normalizeCharReferences( $text ) {
1313                 return preg_replace_callback(
1314                         self::CHAR_REFS_REGEX,
1315                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1316                         $text );
1317         }
1318
1319         /**
1320          * @param string $matches
1321          * @return string
1322          */
1323         static function normalizeCharReferencesCallback( $matches ) {
1324                 $ret = null;
1325                 if ( $matches[1] != '' ) {
1326                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1327                 } elseif ( $matches[2] != '' ) {
1328                         $ret = Sanitizer::decCharReference( $matches[2] );
1329                 } elseif ( $matches[3] != '' ) {
1330                         $ret = Sanitizer::hexCharReference( $matches[3] );
1331                 }
1332                 if ( is_null( $ret ) ) {
1333                         return htmlspecialchars( $matches[0] );
1334                 } else {
1335                         return $ret;
1336                 }
1337         }
1338
1339         /**
1340          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1341          * return the equivalent numeric entity reference (except for the core &lt;
1342          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1343          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1344          * pseudo-entity source (eg &amp;foo;)
1345          *
1346          * @param string $name
1347          * @return string
1348          */
1349         static function normalizeEntity( $name ) {
1350                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1351                         return '&' . self::$htmlEntityAliases[$name] . ';';
1352                 } elseif ( in_array( $name,
1353                 array( 'lt', 'gt', 'amp', 'quot' ) ) ) {
1354                         return "&$name;";
1355                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1356                         return '&#' . self::$htmlEntities[$name] . ';';
1357                 } else {
1358                         return "&amp;$name;";
1359                 }
1360         }
1361
1362         /**
1363          * @param int $codepoint
1364          * @return null|string
1365          */
1366         static function decCharReference( $codepoint ) {
1367                 $point = intval( $codepoint );
1368                 if ( Sanitizer::validateCodepoint( $point ) ) {
1369                         return sprintf( '&#%d;', $point );
1370                 } else {
1371                         return null;
1372                 }
1373         }
1374
1375         /**
1376          * @param int $codepoint
1377          * @return null|string
1378          */
1379         static function hexCharReference( $codepoint ) {
1380                 $point = hexdec( $codepoint );
1381                 if ( Sanitizer::validateCodepoint( $point ) ) {
1382                         return sprintf( '&#x%x;', $point );
1383                 } else {
1384                         return null;
1385                 }
1386         }
1387
1388         /**
1389          * Returns true if a given Unicode codepoint is a valid character in XML.
1390          * @param int $codepoint
1391          * @return bool
1392          */
1393         private static function validateCodepoint( $codepoint ) {
1394                 return $codepoint == 0x09
1395                         || $codepoint == 0x0a
1396                         || $codepoint == 0x0d
1397                         || ( $codepoint >= 0x20 && $codepoint <= 0xd7ff )
1398                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1399                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1400         }
1401
1402         /**
1403          * Decode any character references, numeric or named entities,
1404          * in the text and return a UTF-8 string.
1405          *
1406          * @param string $text
1407          * @return string
1408          */
1409         public static function decodeCharReferences( $text ) {
1410                 return preg_replace_callback(
1411                         self::CHAR_REFS_REGEX,
1412                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1413                         $text );
1414         }
1415
1416         /**
1417          * Decode any character references, numeric or named entities,
1418          * in the next and normalize the resulting string. (bug 14952)
1419          *
1420          * This is useful for page titles, not for text to be displayed,
1421          * MediaWiki allows HTML entities to escape normalization as a feature.
1422          *
1423          * @param string $text Already normalized, containing entities
1424          * @return string Still normalized, without entities
1425          */
1426         public static function decodeCharReferencesAndNormalize( $text ) {
1427                 global $wgContLang;
1428                 $text = preg_replace_callback(
1429                         self::CHAR_REFS_REGEX,
1430                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1431                         $text, /* limit */ -1, $count );
1432
1433                 if ( $count ) {
1434                         return $wgContLang->normalize( $text );
1435                 } else {
1436                         return $text;
1437                 }
1438         }
1439
1440         /**
1441          * @param string $matches
1442          * @return string
1443          */
1444         static function decodeCharReferencesCallback( $matches ) {
1445                 if ( $matches[1] != '' ) {
1446                         return Sanitizer::decodeEntity( $matches[1] );
1447                 } elseif ( $matches[2] != '' ) {
1448                         return Sanitizer::decodeChar( intval( $matches[2] ) );
1449                 } elseif ( $matches[3] != '' ) {
1450                         return Sanitizer::decodeChar( hexdec( $matches[3] ) );
1451                 }
1452                 # Last case should be an ampersand by itself
1453                 return $matches[0];
1454         }
1455
1456         /**
1457          * Return UTF-8 string for a codepoint if that is a valid
1458          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1459          * @param int $codepoint
1460          * @return string
1461          * @private
1462          */
1463         static function decodeChar( $codepoint ) {
1464                 if ( Sanitizer::validateCodepoint( $codepoint ) ) {
1465                         return codepointToUtf8( $codepoint );
1466                 } else {
1467                         return UTF8_REPLACEMENT;
1468                 }
1469         }
1470
1471         /**
1472          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1473          * return the UTF-8 encoding of that character. Otherwise, returns
1474          * pseudo-entity source (eg "&foo;")
1475          *
1476          * @param string $name
1477          * @return string
1478          */
1479         static function decodeEntity( $name ) {
1480                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1481                         $name = self::$htmlEntityAliases[$name];
1482                 }
1483                 if ( isset( self::$htmlEntities[$name] ) ) {
1484                         return codepointToUtf8( self::$htmlEntities[$name] );
1485                 } else {
1486                         return "&$name;";
1487                 }
1488         }
1489
1490         /**
1491          * Fetch the whitelist of acceptable attributes for a given element name.
1492          *
1493          * @param string $element
1494          * @return array
1495          */
1496         static function attributeWhitelist( $element ) {
1497                 $list = Sanitizer::setupAttributeWhitelist();
1498                 return isset( $list[$element] )
1499                         ? $list[$element]
1500                         : array();
1501         }
1502
1503         /**
1504          * Foreach array key (an allowed HTML element), return an array
1505          * of allowed attributes
1506          * @return array
1507          */
1508         static function setupAttributeWhitelist() {
1509                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
1510                 static $whitelist, $staticInitialised;
1511
1512                 $globalContext = implode( '-', compact( 'wgAllowRdfaAttributes', 'wgAllowMicrodataAttributes' ) );
1513
1514                 if ( $whitelist !== null && $staticInitialised == $globalContext ) {
1515                         return $whitelist;
1516                 }
1517
1518                 $common = array(
1519                         # HTML
1520                         'id',
1521                         'class',
1522                         'style',
1523                         'lang',
1524                         'dir',
1525                         'title',
1526
1527                         # WAI-ARIA
1528                         'role',
1529                 );
1530
1531                 if ( $wgAllowRdfaAttributes ) {
1532                         # RDFa attributes as specified in section 9 of
1533                         # http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1534                         $common = array_merge( $common, array(
1535                                 'about', 'property', 'resource', 'datatype', 'typeof',
1536                         ) );
1537                 }
1538
1539                 if ( $wgAllowMicrodataAttributes ) {
1540                         # add HTML5 microdata tags as specified by
1541                         # http://www.whatwg.org/html/microdata.html#the-microdata-model
1542                         $common = array_merge( $common, array(
1543                                 'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1544                         ) );
1545                 }
1546
1547                 $block = array_merge( $common, array( 'align' ) );
1548                 $tablealign = array( 'align', 'valign' );
1549                 $tablecell = array(
1550                         'abbr',
1551                         'axis',
1552                         'headers',
1553                         'scope',
1554                         'rowspan',
1555                         'colspan',
1556                         'nowrap', # deprecated
1557                         'width', # deprecated
1558                         'height', # deprecated
1559                         'bgcolor', # deprecated
1560                 );
1561
1562                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1563                 # See: http://www.w3.org/TR/html4/
1564                 $whitelist = array(
1565                         # 7.5.4
1566                         'div'        => $block,
1567                         'center'     => $common, # deprecated
1568                         'span'       => $common,
1569
1570                         # 7.5.5
1571                         'h1'         => $block,
1572                         'h2'         => $block,
1573                         'h3'         => $block,
1574                         'h4'         => $block,
1575                         'h5'         => $block,
1576                         'h6'         => $block,
1577
1578                         # 7.5.6
1579                         # address
1580
1581                         # 8.2.4
1582                         'bdo'        => $common,
1583
1584                         # 9.2.1
1585                         'em'         => $common,
1586                         'strong'     => $common,
1587                         'cite'       => $common,
1588                         'dfn'        => $common,
1589                         'code'       => $common,
1590                         'samp'       => $common,
1591                         'kbd'        => $common,
1592                         'var'        => $common,
1593                         'abbr'       => $common,
1594                         # acronym
1595
1596                         # 9.2.2
1597                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1598                         'q'          => array_merge( $common, array( 'cite' ) ),
1599
1600                         # 9.2.3
1601                         'sub'        => $common,
1602                         'sup'        => $common,
1603
1604                         # 9.3.1
1605                         'p'          => $block,
1606
1607                         # 9.3.2
1608                         'br'         => array_merge( $common, array( 'clear' ) ),
1609
1610                         # http://www.whatwg.org/html/text-level-semantics.html#the-wbr-element
1611                         'wbr'        => $common,
1612
1613                         # 9.3.4
1614                         'pre'        => array_merge( $common, array( 'width' ) ),
1615
1616                         # 9.4
1617                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1618                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1619
1620                         # 10.2
1621                         'ul'         => array_merge( $common, array( 'type' ) ),
1622                         'ol'         => array_merge( $common, array( 'type', 'start' ) ),
1623                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1624
1625                         # 10.3
1626                         'dl'         => $common,
1627                         'dd'         => $common,
1628                         'dt'         => $common,
1629
1630                         # 11.2.1
1631                         'table'      => array_merge( $common,
1632                                                                 array( 'summary', 'width', 'border', 'frame',
1633                                                                                 'rules', 'cellspacing', 'cellpadding',
1634                                                                                 'align', 'bgcolor',
1635                                                                 ) ),
1636
1637                         # 11.2.2
1638                         'caption'    => $block,
1639
1640                         # 11.2.3
1641                         'thead'      => $common,
1642                         'tfoot'      => $common,
1643                         'tbody'      => $common,
1644
1645                         # 11.2.4
1646                         'colgroup'   => array_merge( $common, array( 'span' ) ),
1647                         'col'        => array_merge( $common, array( 'span' ) ),
1648
1649                         # 11.2.5
1650                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1651
1652                         # 11.2.6
1653                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1654                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1655
1656                         # 12.2
1657                         # NOTE: <a> is not allowed directly, but the attrib
1658                         # whitelist is used from the Parser object
1659                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1660
1661                         # 13.2
1662                         # Not usually allowed, but may be used for extension-style hooks
1663                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1664                         # true
1665                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1666
1667                         # 15.2.1
1668                         'tt'         => $common,
1669                         'b'          => $common,
1670                         'i'          => $common,
1671                         'big'        => $common,
1672                         'small'      => $common,
1673                         'strike'     => $common,
1674                         's'          => $common,
1675                         'u'          => $common,
1676
1677                         # 15.2.2
1678                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1679                         # basefont
1680
1681                         # 15.3
1682                         'hr'         => array_merge( $common, array( 'width' ) ),
1683
1684                         # HTML Ruby annotation text module, simple ruby only.
1685                         # http://www.whatwg.org/html/text-level-semantics.html#the-ruby-element
1686                         'ruby'       => $common,
1687                         # rbc
1688                         # rtc
1689                         'rb'         => $common,
1690                         'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),
1691                         'rp'         => $common,
1692
1693                         # MathML root element, where used for extensions
1694                         # 'title' may not be 100% valid here; it's XHTML
1695                         # http://www.w3.org/TR/REC-MathML/
1696                         'math'       => array( 'class', 'style', 'id', 'title' ),
1697
1698                         # HTML 5 section 4.6
1699                         'bdi' => $common,
1700
1701                         # HTML5 elements, defined by:
1702                         # http://www.whatwg.org/html/
1703                         'data' => array_merge( $common, array( 'value' ) ),
1704                         'time' => array_merge( $common, array( 'datetime' ) ),
1705                         'mark' => $common,
1706
1707                         // meta and link are only permitted by removeHTMLtags when Microdata
1708                         // is enabled so we don't bother adding a conditional to hide these
1709                         // Also meta and link are only valid in WikiText as Microdata elements
1710                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1711                         // So we don't bother including $common attributes that have no purpose.
1712                         'meta' => array( 'itemprop', 'content' ),
1713                         'link' => array( 'itemprop', 'href' ),
1714                 );
1715
1716                 $staticInitialised = $globalContext;
1717
1718                 return $whitelist;
1719         }
1720
1721         /**
1722          * Take a fragment of (potentially invalid) HTML and return
1723          * a version with any tags removed, encoded as plain text.
1724          *
1725          * Warning: this return value must be further escaped for literal
1726          * inclusion in HTML output as of 1.10!
1727          *
1728          * @param string $text HTML fragment
1729          * @return string
1730          */
1731         static function stripAllTags( $text ) {
1732                 # Actual <tags>
1733                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1734
1735                 # Normalize &entities and whitespace
1736                 $text = self::decodeCharReferences( $text );
1737                 $text = self::normalizeWhitespace( $text );
1738
1739                 return $text;
1740         }
1741
1742         /**
1743          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1744          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1745          * PHP 5.1 doesn't.
1746          *
1747          * Use for passing XHTML fragments to PHP's XML parsing functions
1748          *
1749          * @return string
1750          */
1751         static function hackDocType() {
1752                 $out = "<!DOCTYPE html [\n";
1753                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
1754                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1755                 }
1756                 $out .= "]>\n";
1757                 return $out;
1758         }
1759
1760         /**
1761          * @param string $url
1762          * @return mixed|string
1763          */
1764         static function cleanUrl( $url ) {
1765                 # Normalize any HTML entities in input. They will be
1766                 # re-escaped by makeExternalLink().
1767                 $url = Sanitizer::decodeCharReferences( $url );
1768
1769                 # Escape any control characters introduced by the above step
1770                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1771                         array( __CLASS__, 'cleanUrlCallback' ), $url );
1772
1773                 # Validate hostname portion
1774                 $matches = array();
1775                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1776                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1777
1778                         // Characters that will be ignored in IDNs.
1779                         // http://tools.ietf.org/html/3454#section-3.1
1780                         // Strip them before further processing so blacklists and such work.
1781                         $strip = "/
1782                                 \\s|          # general whitespace
1783                                 \xc2\xad|     # 00ad SOFT HYPHEN
1784                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1785                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1786                                 \xe2\x81\xa0| # 2060 WORD JOINER
1787                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1788                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1789                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1790                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1791                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1792                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1793                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1794                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
1795                                 /xuD";
1796
1797                         $host = preg_replace( $strip, '', $host );
1798
1799                         // @todo FIXME: Validate hostnames here
1800
1801                         return $protocol . $host . $rest;
1802                 } else {
1803                         return $url;
1804                 }
1805         }
1806
1807         /**
1808          * @param array $matches
1809          * @return string
1810          */
1811         static function cleanUrlCallback( $matches ) {
1812                 return urlencode( $matches[0] );
1813         }
1814
1815         /**
1816          * Does a string look like an e-mail address?
1817          *
1818          * This validates an email address using an HTML5 specification found at:
1819          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
1820          * Which as of 2011-01-24 says:
1821          *
1822          *   A valid e-mail address is a string that matches the ABNF production
1823          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1824          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1825          *   3.5.
1826          *
1827          * This function is an implementation of the specification as requested in
1828          * bug 22449.
1829          *
1830          * Client-side forms will use the same standard validation rules via JS or
1831          * HTML 5 validation; additional restrictions can be enforced server-side
1832          * by extensions via the 'isValidEmailAddr' hook.
1833          *
1834          * Note that this validation doesn't 100% match RFC 2822, but is believed
1835          * to be liberal enough for wide use. Some invalid addresses will still
1836          * pass validation here.
1837          *
1838          * @since 1.18
1839          *
1840          * @param string $addr E-mail address
1841          * @return bool
1842          */
1843         public static function validateEmail( $addr ) {
1844                 $result = null;
1845                 if ( !wfRunHooks( 'isValidEmailAddr', array( $addr, &$result ) ) ) {
1846                         return $result;
1847                 }
1848
1849                 // Please note strings below are enclosed in brackets [], this make the
1850                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1851                 // See bug 26948
1852                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
1853                 $rfc1034_ldh_str = "a-z0-9\\-";
1854
1855                 $html5_email_regexp = "/
1856                 ^                      # start of string
1857                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1858                 @                      # 'apostrophe'
1859                 [$rfc1034_ldh_str]+       # First domain part
1860                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1861                 $                      # End of string
1862                 /ix"; // case Insensitive, eXtended
1863
1864                 return (bool)preg_match( $html5_email_regexp, $addr );
1865         }
1866 }