includes/Sanitizer.php

   1 <?php
   2 /**
   3  * HTML sanitizer for %MediaWiki.
   4  *
   5  * Copyright © 2002-2005 Brion Vibber <brion@pobox.com> et al
   6  * https://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Parser
  25  */
  26
  27 /**
  28  * HTML sanitizer for MediaWiki
  29  * @ingroup Parser
  30  */
  31 class Sanitizer {
  32         /**
  33          * Regular expression to match various types of character references in
  34          * Sanitizer::normalizeCharReferences and Sanitizer::decodeCharReferences
  35          */
  36         const CHAR_REFS_REGEX =
  37                 '/&([A-Za-z0-9\x80-\xff]+);
  38                  |&\#([0-9]+);
  39                  |&\#[xX]([0-9A-Fa-f]+);
  40                  |(&)/x';
  41
  42         /**
  43          * Blacklist for evil uris like javascript:
  44          * WARNING: DO NOT use this in any place that actually requires blacklisting
  45          * for security reasons. There are NUMEROUS[1] ways to bypass blacklisting, the
  46          * only way to be secure from javascript: uri based xss vectors is to whitelist
  47          * things that you know are safe and deny everything else.
  48          * [1]: http://ha.ckers.org/xss.html
  49          */
  50         const EVIL_URI_PATTERN = '!(^|\s|\*/\s*)(javascript|vbscript)([^\w]|$)!i';
  51         const XMLNS_ATTRIBUTE_PATTERN = "/^xmlns:[:A-Z_a-z-.0-9]+$/";
  52
  53         /**
  54          * List of all named character entities defined in HTML 4.01
  55          * http://www.w3.org/TR/html4/sgml/entities.html
  56          * As well as &apos; which is only defined starting in XHTML1.
  57          */
  58         private static $htmlEntities = array(
  59                 'Aacute'   => 193,
  60                 'aacute'   => 225,
  61                 'Acirc'    => 194,
  62                 'acirc'    => 226,
  63                 'acute'    => 180,
  64                 'AElig'    => 198,
  65                 'aelig'    => 230,
  66                 'Agrave'   => 192,
  67                 'agrave'   => 224,
  68                 'alefsym'  => 8501,
  69                 'Alpha'    => 913,
  70                 'alpha'    => 945,
  71                 'amp'      => 38,
  72                 'and'      => 8743,
  73                 'ang'      => 8736,
  74                 'apos'     => 39, // New in XHTML & HTML 5; avoid in output for compatibility with IE.
  75                 'Aring'    => 197,
  76                 'aring'    => 229,
  77                 'asymp'    => 8776,
  78                 'Atilde'   => 195,
  79                 'atilde'   => 227,
  80                 'Auml'     => 196,
  81                 'auml'     => 228,
  82                 'bdquo'    => 8222,
  83                 'Beta'     => 914,
  84                 'beta'     => 946,
  85                 'brvbar'   => 166,
  86                 'bull'     => 8226,
  87                 'cap'      => 8745,
  88                 'Ccedil'   => 199,
  89                 'ccedil'   => 231,
  90                 'cedil'    => 184,
  91                 'cent'     => 162,
  92                 'Chi'      => 935,
  93                 'chi'      => 967,
  94                 'circ'     => 710,
  95                 'clubs'    => 9827,
  96                 'cong'     => 8773,
  97                 'copy'     => 169,
  98                 'crarr'    => 8629,
  99                 'cup'      => 8746,
 100                 'curren'   => 164,
 101                 'dagger'   => 8224,
 102                 'Dagger'   => 8225,
 103                 'darr'     => 8595,
 104                 'dArr'     => 8659,
 105                 'deg'      => 176,
 106                 'Delta'    => 916,
 107                 'delta'    => 948,
 108                 'diams'    => 9830,
 109                 'divide'   => 247,
 110                 'Eacute'   => 201,
 111                 'eacute'   => 233,
 112                 'Ecirc'    => 202,
 113                 'ecirc'    => 234,
 114                 'Egrave'   => 200,
 115                 'egrave'   => 232,
 116                 'empty'    => 8709,
 117                 'emsp'     => 8195,
 118                 'ensp'     => 8194,
 119                 'Epsilon'  => 917,
 120                 'epsilon'  => 949,
 121                 'equiv'    => 8801,
 122                 'Eta'      => 919,
 123                 'eta'      => 951,
 124                 'ETH'      => 208,
 125                 'eth'      => 240,
 126                 'Euml'     => 203,
 127                 'euml'     => 235,
 128                 'euro'     => 8364,
 129                 'exist'    => 8707,
 130                 'fnof'     => 402,
 131                 'forall'   => 8704,
 132                 'frac12'   => 189,
 133                 'frac14'   => 188,
 134                 'frac34'   => 190,
 135                 'frasl'    => 8260,
 136                 'Gamma'    => 915,
 137                 'gamma'    => 947,
 138                 'ge'       => 8805,
 139                 'gt'       => 62,
 140                 'harr'     => 8596,
 141                 'hArr'     => 8660,
 142                 'hearts'   => 9829,
 143                 'hellip'   => 8230,
 144                 'Iacute'   => 205,
 145                 'iacute'   => 237,
 146                 'Icirc'    => 206,
 147                 'icirc'    => 238,
 148                 'iexcl'    => 161,
 149                 'Igrave'   => 204,
 150                 'igrave'   => 236,
 151                 'image'    => 8465,
 152                 'infin'    => 8734,
 153                 'int'      => 8747,
 154                 'Iota'     => 921,
 155                 'iota'     => 953,
 156                 'iquest'   => 191,
 157                 'isin'     => 8712,
 158                 'Iuml'     => 207,
 159                 'iuml'     => 239,
 160                 'Kappa'    => 922,
 161                 'kappa'    => 954,
 162                 'Lambda'   => 923,
 163                 'lambda'   => 955,
 164                 'lang'     => 9001,
 165                 'laquo'    => 171,
 166                 'larr'     => 8592,
 167                 'lArr'     => 8656,
 168                 'lceil'    => 8968,
 169                 'ldquo'    => 8220,
 170                 'le'       => 8804,
 171                 'lfloor'   => 8970,
 172                 'lowast'   => 8727,
 173                 'loz'      => 9674,
 174                 'lrm'      => 8206,
 175                 'lsaquo'   => 8249,
 176                 'lsquo'    => 8216,
 177                 'lt'       => 60,
 178                 'macr'     => 175,
 179                 'mdash'    => 8212,
 180                 'micro'    => 181,
 181                 'middot'   => 183,
 182                 'minus'    => 8722,
 183                 'Mu'       => 924,
 184                 'mu'       => 956,
 185                 'nabla'    => 8711,
 186                 'nbsp'     => 160,
 187                 'ndash'    => 8211,
 188                 'ne'       => 8800,
 189                 'ni'       => 8715,
 190                 'not'      => 172,
 191                 'notin'    => 8713,
 192                 'nsub'     => 8836,
 193                 'Ntilde'   => 209,
 194                 'ntilde'   => 241,
 195                 'Nu'       => 925,
 196                 'nu'       => 957,
 197                 'Oacute'   => 211,
 198                 'oacute'   => 243,
 199                 'Ocirc'    => 212,
 200                 'ocirc'    => 244,
 201                 'OElig'    => 338,
 202                 'oelig'    => 339,
 203                 'Ograve'   => 210,
 204                 'ograve'   => 242,
 205                 'oline'    => 8254,
 206                 'Omega'    => 937,
 207                 'omega'    => 969,
 208                 'Omicron'  => 927,
 209                 'omicron'  => 959,
 210                 'oplus'    => 8853,
 211                 'or'       => 8744,
 212                 'ordf'     => 170,
 213                 'ordm'     => 186,
 214                 'Oslash'   => 216,
 215                 'oslash'   => 248,
 216                 'Otilde'   => 213,
 217                 'otilde'   => 245,
 218                 'otimes'   => 8855,
 219                 'Ouml'     => 214,
 220                 'ouml'     => 246,
 221                 'para'     => 182,
 222                 'part'     => 8706,
 223                 'permil'   => 8240,
 224                 'perp'     => 8869,
 225                 'Phi'      => 934,
 226                 'phi'      => 966,
 227                 'Pi'       => 928,
 228                 'pi'       => 960,
 229                 'piv'      => 982,
 230                 'plusmn'   => 177,
 231                 'pound'    => 163,
 232                 'prime'    => 8242,
 233                 'Prime'    => 8243,
 234                 'prod'     => 8719,
 235                 'prop'     => 8733,
 236                 'Psi'      => 936,
 237                 'psi'      => 968,
 238                 'quot'     => 34,
 239                 'radic'    => 8730,
 240                 'rang'     => 9002,
 241                 'raquo'    => 187,
 242                 'rarr'     => 8594,
 243                 'rArr'     => 8658,
 244                 'rceil'    => 8969,
 245                 'rdquo'    => 8221,
 246                 'real'     => 8476,
 247                 'reg'      => 174,
 248                 'rfloor'   => 8971,
 249                 'Rho'      => 929,
 250                 'rho'      => 961,
 251                 'rlm'      => 8207,
 252                 'rsaquo'   => 8250,
 253                 'rsquo'    => 8217,
 254                 'sbquo'    => 8218,
 255                 'Scaron'   => 352,
 256                 'scaron'   => 353,
 257                 'sdot'     => 8901,
 258                 'sect'     => 167,
 259                 'shy'      => 173,
 260                 'Sigma'    => 931,
 261                 'sigma'    => 963,
 262                 'sigmaf'   => 962,
 263                 'sim'      => 8764,
 264                 'spades'   => 9824,
 265                 'sub'      => 8834,
 266                 'sube'     => 8838,
 267                 'sum'      => 8721,
 268                 'sup'      => 8835,
 269                 'sup1'     => 185,
 270                 'sup2'     => 178,
 271                 'sup3'     => 179,
 272                 'supe'     => 8839,
 273                 'szlig'    => 223,
 274                 'Tau'      => 932,
 275                 'tau'      => 964,
 276                 'there4'   => 8756,
 277                 'Theta'    => 920,
 278                 'theta'    => 952,
 279                 'thetasym' => 977,
 280                 'thinsp'   => 8201,
 281                 'THORN'    => 222,
 282                 'thorn'    => 254,
 283                 'tilde'    => 732,
 284                 'times'    => 215,
 285                 'trade'    => 8482,
 286                 'Uacute'   => 218,
 287                 'uacute'   => 250,
 288                 'uarr'     => 8593,
 289                 'uArr'     => 8657,
 290                 'Ucirc'    => 219,
 291                 'ucirc'    => 251,
 292                 'Ugrave'   => 217,
 293                 'ugrave'   => 249,
 294                 'uml'      => 168,
 295                 'upsih'    => 978,
 296                 'Upsilon'  => 933,
 297                 'upsilon'  => 965,
 298                 'Uuml'     => 220,
 299                 'uuml'     => 252,
 300                 'weierp'   => 8472,
 301                 'Xi'       => 926,
 302                 'xi'       => 958,
 303                 'Yacute'   => 221,
 304                 'yacute'   => 253,
 305                 'yen'      => 165,
 306                 'Yuml'     => 376,
 307                 'yuml'     => 255,
 308                 'Zeta'     => 918,
 309                 'zeta'     => 950,
 310                 'zwj'      => 8205,
 311                 'zwnj'     => 8204
 312         );
 313
 314         /**
 315          * Character entity aliases accepted by MediaWiki
 316          */
 317         private static $htmlEntityAliases = array(
 318                 'רלמ' => 'rlm',
 319                 'رلم' => 'rlm',
 320         );
 321
 322         /**
 323          * Lazy-initialised attributes regex, see getAttribsRegex()
 324          */
 325         private static $attribsRegex;
 326
 327         /**
 328          * Regular expression to match HTML/XML attribute pairs within a tag.
 329          * Allows some... latitude.
 330          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 331          * @return string
 332          */
 333         static function getAttribsRegex() {
 334                 if ( self::$attribsRegex === null ) {
 335                         $attribFirst = '[:A-Z_a-z0-9]';
 336                         $attrib = '[:A-Z_a-z-.0-9]';
 337                         $space = '[\x09\x0a\x0d\x20]';
 338                         self::$attribsRegex =
 339                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 340                                   ($space*=$space*
 341                                         (?:
 342                                          # The attribute value: quoted or alone
 343                                           \"([^<\"]*)\"
 344                                          | '([^<']*)'
 345                                          |  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)
 346                                          |  (\#[0-9a-fA-F]+) # Technically wrong, but lots of
 347                                                                                  # colors are specified like this.
 348                                                                                  # We'll be normalizing it.
 349                                         )
 350                                 )?(?=$space|\$)/sx";
 351                 }
 352                 return self::$attribsRegex;
 353         }
 354
 355         /**
 356          * Cleans up HTML, removes dangerous tags and attributes, and
 357          * removes HTML comments
 358          * @private
 359          * @param string $text
 360          * @param callable $processCallback Callback to do any variable or parameter
 361          *   replacements in HTML attribute values
 362          * @param array|bool $args Arguments for the processing callback
 363          * @param array $extratags For any extra tags to include
 364          * @param array $removetags For any tags (default or extra) to exclude
 365          * @return string
 366          */
 367         static function removeHTMLtags( $text, $processCallback = null,
 368                 $args = array(), $extratags = array(), $removetags = array()
 369         ) {
 370                 global $wgUseTidy, $wgAllowMicrodataAttributes, $wgAllowImageTag;
 371
 372                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 373                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 374
 375                 wfProfileIn( __METHOD__ );
 376
 377                 // Base our staticInitialised variable off of the global config state so that if the globals
 378                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 379                 $globalContext = implode( '-', compact( 'wgAllowMicrodataAttributes', 'wgAllowImageTag' ) );
 380                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 381
 382                         $htmlpairsStatic = array( # Tags that must be closed
 383                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 384                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 385                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 386                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 387                                 'ruby', 'rb', 'rp', 'rt', 'rtc', 'p', 'span', 'abbr', 'dfn',
 388                                 'kbd', 'samp', 'data', 'time', 'mark'
 389                         );
 390                         $htmlsingle = array(
 391                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd'
 392                         );
 393                         $htmlsingleonly = array( # Elements that cannot have close tags
 394                                 'br', 'wbr', 'hr'
 395                         );
 396                         if ( $wgAllowMicrodataAttributes ) {
 397                                 $htmlsingle[] = $htmlsingleonly[] = 'meta';
 398                                 $htmlsingle[] = $htmlsingleonly[] = 'link';
 399                         }
 400                         $htmlnest = array( # Tags that can be nested--??
 401                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 402                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 403                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 404                         );
 405                         $tabletags = array( # Can only appear inside table, we will close them
 406                                 'td', 'th', 'tr',
 407                         );
 408                         $htmllist = array( # Tags used by list
 409                                 'ul', 'ol',
 410                         );
 411                         $listtags = array( # Tags that can appear in a list
 412                                 'li',
 413                         );
 414
 415                         if ( $wgAllowImageTag ) {
 416                                 $htmlsingle[] = 'img';
 417                                 $htmlsingleonly[] = 'img';
 418                         }
 419
 420                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 421                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 422
 423                         # Convert them all to hashtables for faster lookup
 424                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 425                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 426                         foreach ( $vars as $var ) {
 427                                 $$var = array_flip( $$var );
 428                         }
 429                         $staticInitialised = $globalContext;
 430                 }
 431                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 432                 $extratags = array_flip( $extratags );
 433                 $removetags = array_flip( $removetags );
 434                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 435                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 436
 437                 # Remove HTML comments
 438                 $text = Sanitizer::removeHTMLcomments( $text );
 439                 $bits = explode( '<', $text );
 440                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 441                 if ( !$wgUseTidy ) {
 442                         $tagstack = $tablestack = array();
 443                         foreach ( $bits as $x ) {
 444                                 $regs = array();
 445                                 # $slash: Does the current element start with a '/'?
 446                                 # $t: Current element name
 447                                 # $params: String between element name and >
 448                                 # $brace: Ending '>' or '/>'
 449                                 # $rest: Everything until the next element of $bits
 450                                 if ( preg_match( '!^(/?)([^\\s/>]+)([^>]*?)(/{0,1}>)([^<]*)$!', $x, $regs ) ) {
 451                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 452                                 } else {
 453                                         $slash = $t = $params = $brace = $rest = null;
 454                                 }
 455
 456                                 $badtag = false;
 457                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 458                                         # Check our stack
 459                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 460                                                 $badtag = true;
 461                                         } elseif ( $slash ) {
 462                                                 # Closing a tag... is it the one we just opened?
 463                                                 wfSuppressWarnings();
 464                                                 $ot = array_pop( $tagstack );
 465                                                 wfRestoreWarnings();
 466
 467                                                 if ( $ot != $t ) {
 468                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 469                                                                 # Pop all elements with an optional close tag
 470                                                                 # and see if we find a match below them
 471                                                                 $optstack = array();
 472                                                                 array_push( $optstack, $ot );
 473                                                                 wfSuppressWarnings();
 474                                                                 $ot = array_pop( $tagstack );
 475                                                                 wfRestoreWarnings();
 476                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 477                                                                         array_push( $optstack, $ot );
 478                                                                         wfSuppressWarnings();
 479                                                                         $ot = array_pop( $tagstack );
 480                                                                         wfRestoreWarnings();
 481                                                                 }
 482                                                                 if ( $t != $ot ) {
 483                                                                         # No match. Push the optional elements back again
 484                                                                         $badtag = true;
 485                                                                         wfSuppressWarnings();
 486                                                                         $ot = array_pop( $optstack );
 487                                                                         wfRestoreWarnings();
 488                                                                         while ( $ot ) {
 489                                                                                 array_push( $tagstack, $ot );
 490                                                                                 wfSuppressWarnings();
 491                                                                                 $ot = array_pop( $optstack );
 492                                                                                 wfRestoreWarnings();
 493                                                                         }
 494                                                                 }
 495                                                         } else {
 496                                                                 wfSuppressWarnings();
 497                                                                 array_push( $tagstack, $ot );
 498                                                                 wfRestoreWarnings();
 499
 500                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 501                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 502                                                                         $badtag = true;
 503                                                                 }
 504                                                         }
 505                                                 } else {
 506                                                         if ( $t == 'table' ) {
 507                                                                 $tagstack = array_pop( $tablestack );
 508                                                         }
 509                                                 }
 510                                                 $newparams = '';
 511                                         } else {
 512                                                 # Keep track for later
 513                                                 if ( isset( $tabletags[$t] ) && !in_array( 'table', $tagstack ) ) {
 514                                                         $badtag = true;
 515                                                 } elseif ( in_array( $t, $tagstack ) && !isset( $htmlnest[$t] ) ) {
 516                                                         $badtag = true;
 517                                                 # Is it a self closed htmlpair ? (bug 5487)
 518                                                 } elseif ( $brace == '/>' && isset( $htmlpairs[$t] ) ) {
 519                                                         $badtag = true;
 520                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 521                                                         # Hack to force empty tag for unclosable elements
 522                                                         $brace = '/>';
 523                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 524                                                         # Hack to not close $htmlsingle tags
 525                                                         $brace = null;
 526                                                         # Still need to push this optionally-closed tag to
 527                                                         # the tag stack so that we can match end tags
 528                                                         # instead of marking them as bad.
 529                                                         array_push( $tagstack, $t );
 530                                                 } elseif ( isset( $tabletags[$t] ) && in_array( $t, $tagstack ) ) {
 531                                                         // New table tag but forgot to close the previous one
 532                                                         $text .= "</$t>";
 533                                                 } else {
 534                                                         if ( $t == 'table' ) {
 535                                                                 array_push( $tablestack, $tagstack );
 536                                                                 $tagstack = array();
 537                                                         }
 538                                                         array_push( $tagstack, $t );
 539                                                 }
 540
 541                                                 # Replace any variables or template parameters with
 542                                                 # plaintext results.
 543                                                 if ( is_callable( $processCallback ) ) {
 544                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 545                                                 }
 546
 547                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 548                                                         $badtag = true;
 549                                                 }
 550
 551                                                 # Strip non-approved attributes from the tag
 552                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 553                                         }
 554                                         if ( !$badtag ) {
 555                                                 $rest = str_replace( '>', '&gt;', $rest );
 556                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 557                                                 $text .= "<$slash$t$newparams$close>$rest";
 558                                                 continue;
 559                                         }
 560                                 }
 561                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 562                         }
 563                         # Close off any remaining tags
 564                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 565                                 $text .= "</$t>\n";
 566                                 if ( $t == 'table' ) {
 567                                         $tagstack = array_pop( $tablestack );
 568                                 }
 569                         }
 570                 } else {
 571                         # this might be possible using tidy itself
 572                         foreach ( $bits as $x ) {
 573                                 preg_match(
 574                                         '/^(\\/?)(\\w+)([^>]*?)(\\/{0,1}>)([^<]*)$/',
 575                                         $x,
 576                                         $regs
 577                                 );
 578
 579                                 wfSuppressWarnings();
 580                                 list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 581                                 wfRestoreWarnings();
 582
 583                                 $badtag = false;
 584                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 585                                         if ( is_callable( $processCallback ) ) {
 586                                                 call_user_func_array( $processCallback, array( &$params, $args ) );
 587                                         }
 588
 589                                         if ( !Sanitizer::validateTag( $params, $t ) ) {
 590                                                 $badtag = true;
 591                                         }
 592
 593                                         $newparams = Sanitizer::fixTagAttributes( $params, $t );
 594                                         if ( !$badtag ) {
 595                                                 $rest = str_replace( '>', '&gt;', $rest );
 596                                                 $text .= "<$slash$t$newparams$brace$rest";
 597                                                 continue;
 598                                         }
 599                                 }
 600                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 601                         }
 602                 }
 603                 wfProfileOut( __METHOD__ );
 604                 return $text;
 605         }
 606
 607         /**
 608          * Remove '<!--', '-->', and everything between.
 609          * To avoid leaving blank lines, when a comment is both preceded
 610          * and followed by a newline (ignoring spaces), trim leading and
 611          * trailing spaces and one of the newlines.
 612          *
 613          * @private
 614          * @param string $text
 615          * @return string
 616          */
 617         static function removeHTMLcomments( $text ) {
 618                 wfProfileIn( __METHOD__ );
 619                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 620                         $end = strpos( $text, '-->', $start + 4 );
 621                         if ( $end === false ) {
 622                                 # Unterminated comment; bail out
 623                                 break;
 624                         }
 625
 626                         $end += 3;
 627
 628                         # Trim space and newline if the comment is both
 629                         # preceded and followed by a newline
 630                         $spaceStart = max( $start - 1, 0 );
 631                         $spaceLen = $end - $spaceStart;
 632                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 633                                 $spaceStart--;
 634                                 $spaceLen++;
 635                         }
 636                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 637                                 $spaceLen++;
 638                         }
 639                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 640                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 641                                 # Remove the comment, leading and trailing
 642                                 # spaces, and leave only one newline.
 643                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 644                         } else {
 645                                 # Remove just the comment.
 646                                 $text = substr_replace( $text, '', $start, $end - $start );
 647                         }
 648                 }
 649                 wfProfileOut( __METHOD__ );
 650                 return $text;
 651         }
 652
 653         /**
 654          * Takes attribute names and values for a tag and the tag name and
 655          * validates that the tag is allowed to be present.
 656          * This DOES NOT validate the attributes, nor does it validate the
 657          * tags themselves. This method only handles the special circumstances
 658          * where we may want to allow a tag within content but ONLY when it has
 659          * specific attributes set.
 660          *
 661          * @param string $params
 662          * @param string $element
 663          * @return bool
 664          */
 665         static function validateTag( $params, $element ) {
 666                 $params = Sanitizer::decodeTagAttributes( $params );
 667
 668                 if ( $element == 'meta' || $element == 'link' ) {
 669                         if ( !isset( $params['itemprop'] ) ) {
 670                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 671                                 return false;
 672                         }
 673                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 674                                 // <meta> must have a content="" for the itemprop
 675                                 return false;
 676                         }
 677                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 678                                 // <link> must have an associated href=""
 679                                 return false;
 680                         }
 681                 }
 682
 683                 return true;
 684         }
 685
 686         /**
 687          * Take an array of attribute names and values and normalize or discard
 688          * illegal values for the given element type.
 689          *
 690          * - Discards attributes not on a whitelist for the given element
 691          * - Unsafe style attributes are discarded
 692          * - Invalid id attributes are re-encoded
 693          *
 694          * @param array $attribs
 695          * @param string $element
 696          * @return array
 697          *
 698          * @todo Check for legal values where the DTD limits things.
 699          * @todo Check for unique id attribute :P
 700          */
 701         static function validateTagAttributes( $attribs, $element ) {
 702                 return Sanitizer::validateAttributes( $attribs,
 703                         Sanitizer::attributeWhitelist( $element ) );
 704         }
 705
 706         /**
 707          * Take an array of attribute names and values and normalize or discard
 708          * illegal values for the given whitelist.
 709          *
 710          * - Discards attributes not the given whitelist
 711          * - Unsafe style attributes are discarded
 712          * - Invalid id attributes are re-encoded
 713          *
 714          * @param array $attribs
 715          * @param array $whitelist List of allowed attribute names
 716          * @return array
 717          *
 718          * @todo Check for legal values where the DTD limits things.
 719          * @todo Check for unique id attribute :P
 720          */
 721         static function validateAttributes( $attribs, $whitelist ) {
 722                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 723
 724                 $whitelist = array_flip( $whitelist );
 725                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 726
 727                 $out = array();
 728                 foreach ( $attribs as $attribute => $value ) {
 729                         #allow XML namespace declaration if RDFa is enabled
 730                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 731                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 732                                         $out[$attribute] = $value;
 733                                 }
 734
 735                                 continue;
 736                         }
 737
 738                         # Allow any attribute beginning with "data-"
 739                         if ( !preg_match( '/^data-/i', $attribute ) && !isset( $whitelist[$attribute] ) ) {
 740                                 continue;
 741                         }
 742
 743                         # Strip javascript "expression" from stylesheets.
 744                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 745                         if ( $attribute == 'style' ) {
 746                                 $value = Sanitizer::checkCss( $value );
 747                         }
 748
 749                         if ( $attribute === 'id' ) {
 750                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 751                         }
 752
 753                         # WAI-ARIA
 754                         # http://www.w3.org/TR/wai-aria/
 755                         # http://www.whatwg.org/html/elements.html#wai-aria
 756                         # For now we only support role="presentation" until we work out what roles should be
 757                         # usable by content and we ensure that our code explicitly rejects patterns that
 758                         # violate HTML5's ARIA restrictions.
 759                         if ( $attribute === 'role' && $value !== 'presentation' ) {
 760                                 continue;
 761                         }
 762
 763                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 764                         // Check them for sanity.
 765                         if ( $attribute === 'rel' || $attribute === 'rev'
 766                                 # RDFa
 767                                 || $attribute === 'about' || $attribute === 'property'
 768                                 || $attribute === 'resource' || $attribute === 'datatype'
 769                                 || $attribute === 'typeof'
 770                                 # HTML5 microdata
 771                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 772                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 773                                 || $attribute === 'itemtype'
 774                         ) {
 775                                 //Paranoia. Allow "simple" values but suppress javascript
 776                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 777                                         continue;
 778                                 }
 779                         }
 780
 781                         # NOTE: even though elements using href/src are not allowed directly, supply
 782                         #       validation code that can be used by tag hook handlers, etc
 783                         if ( $attribute === 'href' || $attribute === 'src' ) {
 784                                 if ( !preg_match( $hrefExp, $value ) ) {
 785                                         continue; //drop any href or src attributes not using an allowed protocol.
 786                                         // NOTE: this also drops all relative URLs
 787                                 }
 788                         }
 789
 790                         // If this attribute was previously set, override it.
 791                         // Output should only have one attribute of each name.
 792                         $out[$attribute] = $value;
 793                 }
 794
 795                 if ( $wgAllowMicrodataAttributes ) {
 796                         # itemtype, itemid, itemref don't make sense without itemscope
 797                         if ( !array_key_exists( 'itemscope', $out ) ) {
 798                                 unset( $out['itemtype'] );
 799                                 unset( $out['itemid'] );
 800                                 unset( $out['itemref'] );
 801                         }
 802                         # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 803                 }
 804                 return $out;
 805         }
 806
 807         /**
 808          * Merge two sets of HTML attributes.  Conflicting items in the second set
 809          * will override those in the first, except for 'class' attributes which
 810          * will be combined (if they're both strings).
 811          *
 812          * @todo implement merging for other attributes such as style
 813          * @param array $a
 814          * @param array $b
 815          * @return array
 816          */
 817         static function mergeAttributes( $a, $b ) {
 818                 $out = array_merge( $a, $b );
 819                 if ( isset( $a['class'] ) && isset( $b['class'] )
 820                         && is_string( $a['class'] ) && is_string( $b['class'] )
 821                         && $a['class'] !== $b['class']
 822                 ) {
 823                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 824                                 -1, PREG_SPLIT_NO_EMPTY );
 825                         $out['class'] = implode( ' ', array_unique( $classes ) );
 826                 }
 827                 return $out;
 828         }
 829
 830         /**
 831          * Normalize CSS into a format we can easily search for hostile input
 832          *  - decode character references
 833          *  - decode escape sequences
 834          *  - convert characters that IE6 interprets into ascii
 835          *  - remove comments, unless the entire value is one single comment
 836          * @param string $value the css string
 837          * @return string normalized css
 838          */
 839         public static function normalizeCss( $value ) {
 840
 841                 // Decode character references like &#123;
 842                 $value = Sanitizer::decodeCharReferences( $value );
 843
 844                 // Decode escape sequences and line continuation
 845                 // See the grammar in the CSS 2 spec, appendix D.
 846                 // This has to be done AFTER decoding character references.
 847                 // This means it isn't possible for this function to return
 848                 // unsanitized escape sequences. It is possible to manufacture
 849                 // input that contains character references that decode to
 850                 // escape sequences that decode to character references, but
 851                 // it's OK for the return value to contain character references
 852                 // because the caller is supposed to escape those anyway.
 853                 static $decodeRegex;
 854                 if ( !$decodeRegex ) {
 855                         $space = '[\\x20\\t\\r\\n\\f]';
 856                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 857                         $backslash = '\\\\';
 858                         $decodeRegex = "/ $backslash
 859                                 (?:
 860                                         ($nl) |  # 1. Line continuation
 861                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 862                                         (.) | # 3. backslash cancelling special meaning
 863                                         () | # 4. backslash at end of string
 864                                 )/xu";
 865                 }
 866                 $value = preg_replace_callback( $decodeRegex,
 867                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 868
 869                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 870                 $value = preg_replace_callback(
 871                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (bug 58088)
 872                         function ( $matches ) {
 873                                 $cp = utf8ToCodepoint( $matches[0] );
 874                                 if ( $cp === false ) {
 875                                         return '';
 876                                 }
 877                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 878                         },
 879                         $value
 880                 );
 881
 882                 // Convert more characters IE6 might treat as ascii
 883                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 884                 $value = str_replace(
 885                         array( 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ),
 886                         array( 'r', 'n', 'n', 'l', 'i', '(', '(' ),
 887                         $value
 888                 );
 889
 890                 // Let the value through if it's nothing but a single comment, to
 891                 // allow other functions which may reject it to pass some error
 892                 // message through.
 893                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 894                         // Remove any comments; IE gets token splitting wrong
 895                         // This must be done AFTER decoding character references and
 896                         // escape sequences, because those steps can introduce comments
 897                         // This step cannot introduce character references or escape
 898                         // sequences, because it replaces comments with spaces rather
 899                         // than removing them completely.
 900                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 901
 902                         // Remove anything after a comment-start token, to guard against
 903                         // incorrect client implementations.
 904                         $commentPos = strpos( $value, '/*' );
 905                         if ( $commentPos !== false ) {
 906                                 $value = substr( $value, 0, $commentPos );
 907                         }
 908                 }
 909
 910                 // S followed by repeat, iteration, or prolonged sound marks,
 911                 // which IE will treat as "ss"
 912                 $value = preg_replace(
 913                         '/s(?:
 914                                 \xE3\x80\xB1 | # U+3031
 915                                 \xE3\x82\x9D | # U+309D
 916                                 \xE3\x83\xBC | # U+30FC
 917                                 \xE3\x83\xBD | # U+30FD
 918                                 \xEF\xB9\xBC | # U+FE7C
 919                                 \xEF\xB9\xBD | # U+FE7D
 920                                 \xEF\xBD\xB0   # U+FF70
 921                         )/ix',
 922                         'ss',
 923                         $value
 924                 );
 925
 926                 return $value;
 927         }
 928
 929
 930         /**
 931          * Pick apart some CSS and check it for forbidden or unsafe structures.
 932          * Returns a sanitized string. This sanitized string will have
 933          * character references and escape sequences decoded and comments
 934          * stripped (unless it is itself one valid comment, in which case the value
 935          * will be passed through). If the input is just too evil, only a comment
 936          * complaining about evilness will be returned.
 937          *
 938          * Currently URL references, 'expression', 'tps' are forbidden.
 939          *
 940          * NOTE: Despite the fact that character references are decoded, the
 941          * returned string may contain character references given certain
 942          * clever input strings. These character references must
 943          * be escaped before the return value is embedded in HTML.
 944          *
 945          * @param string $value
 946          * @return string
 947          */
 948         static function checkCss( $value ) {
 949                 $value = self::normalizeCss( $value );
 950
 951                 // Reject problematic keywords and control characters
 952                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ) {
 953                         return '/* invalid control char */';
 954                 } elseif ( preg_match(
 955                         '! expression
 956                                 | filter\s*:
 957                                 | accelerator\s*:
 958                                 | -o-link\s*:
 959                                 | -o-link-source\s*:
 960                                 | -o-replace\s*:
 961                                 | url\s*\(
 962                                 | image\s*\(
 963                                 | image-set\s*\(
 964                         !ix', $value ) ) {
 965                         return '/* insecure input */';
 966                 }
 967                 return $value;
 968         }
 969
 970         /**
 971          * @param array $matches
 972          * @return string
 973          */
 974         static function cssDecodeCallback( $matches ) {
 975                 if ( $matches[1] !== '' ) {
 976                         // Line continuation
 977                         return '';
 978                 } elseif ( $matches[2] !== '' ) {
 979                         $char = codepointToUtf8( hexdec( $matches[2] ) );
 980                 } elseif ( $matches[3] !== '' ) {
 981                         $char = $matches[3];
 982                 } else {
 983                         $char = '\\';
 984                 }
 985                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
 986                         // These characters need to be escaped in strings
 987                         // Clean up the escape sequence to avoid parsing errors by clients
 988                         return '\\' . dechex( ord( $char ) ) . ' ';
 989                 } else {
 990                         // Decode unnecessary escape
 991                         return $char;
 992                 }
 993         }
 994
 995         /**
 996          * Take a tag soup fragment listing an HTML element's attributes
 997          * and normalize it to well-formed XML, discarding unwanted attributes.
 998          * Output is safe for further wikitext processing, with escaping of
 999          * values that could trigger problems.
1000          *
1001          * - Normalizes attribute names to lowercase
1002          * - Discards attributes not on a whitelist for the given element
1003          * - Turns broken or invalid entities into plaintext
1004          * - Double-quotes all attribute values
1005          * - Attributes without values are given the name as attribute
1006          * - Double attributes are discarded
1007          * - Unsafe style attributes are discarded
1008          * - Prepends space if there are attributes.
1009          *
1010          * @param string $text
1011          * @param string $element
1012          * @return string
1013          */
1014         static function fixTagAttributes( $text, $element ) {
1015                 if ( trim( $text ) == '' ) {
1016                         return '';
1017                 }
1018
1019                 $decoded = Sanitizer::decodeTagAttributes( $text );
1020                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
1021
1022                 return Sanitizer::safeEncodeTagAttributes( $stripped );
1023         }
1024
1025         /**
1026          * Encode an attribute value for HTML output.
1027          * @param string $text
1028          * @return string HTML-encoded text fragment
1029          */
1030         static function encodeAttribute( $text ) {
1031                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1032
1033                 // Whitespace is normalized during attribute decoding,
1034                 // so if we've been passed non-spaces we must encode them
1035                 // ahead of time or they won't be preserved.
1036                 $encValue = strtr( $encValue, array(
1037                         "\n" => '&#10;',
1038                         "\r" => '&#13;',
1039                         "\t" => '&#9;',
1040                 ) );
1041
1042                 return $encValue;
1043         }
1044
1045         /**
1046          * Encode an attribute value for HTML tags, with extra armoring
1047          * against further wiki processing.
1048          * @param string $text
1049          * @return string HTML-encoded text fragment
1050          */
1051         static function safeEncodeAttribute( $text ) {
1052                 $encValue = Sanitizer::encodeAttribute( $text );
1053
1054                 # Templates and links may be expanded in later parsing,
1055                 # creating invalid or dangerous output. Suppress this.
1056                 $encValue = strtr( $encValue, array(
1057                         '<'    => '&lt;',   // This should never happen,
1058                         '>'    => '&gt;',   // we've received invalid input
1059                         '"'    => '&quot;', // which should have been escaped.
1060                         '{'    => '&#123;',
1061                         '['    => '&#91;',
1062                         "''"   => '&#39;&#39;',
1063                         'ISBN' => '&#73;SBN',
1064                         'RFC'  => '&#82;FC',
1065                         'PMID' => '&#80;MID',
1066                         '|'    => '&#124;',
1067                         '__'   => '&#95;_',
1068                 ) );
1069
1070                 # Stupid hack
1071                 $encValue = preg_replace_callback(
1072                         '/((?i)' . wfUrlProtocols() . ')/',
1073                         array( 'Sanitizer', 'armorLinksCallback' ),
1074                         $encValue );
1075                 return $encValue;
1076         }
1077
1078         /**
1079          * Given a value, escape it so that it can be used in an id attribute and
1080          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1081          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1082          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1083          * escaped with lots of dots.
1084          *
1085          * To ensure we don't have to bother escaping anything, we also strip ', ",
1086          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1087          * We also strip # because it upsets IE, and % because it could be
1088          * ambiguous if it's part of something that looks like a percent escape
1089          * (which don't work reliably in fragments cross-browser).
1090          *
1091          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
1092          *   in the id and name attributes
1093          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1094          *   the id attribute
1095          * @see http://www.whatwg.org/html/elements.html#the-id-attribute
1096          *   HTML5 definition of id attribute
1097          *
1098          * @param string $id Id to escape
1099          * @param string|array $options String or array of strings (default is array()):
1100          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1101          *       so don't pay attention if the first character isn't valid at the
1102          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1103          *       false.
1104          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1105          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1106          *       anchors and links won't break.
1107          * @return string
1108          */
1109         static function escapeId( $id, $options = array() ) {
1110                 global $wgExperimentalHtmlIds;
1111                 $options = (array)$options;
1112
1113                 $id = Sanitizer::decodeCharReferences( $id );
1114
1115                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1116                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1117                         $id = trim( $id, '_' );
1118                         if ( $id === '' ) {
1119                                 // Must have been all whitespace to start with.
1120                                 return '_';
1121                         } else {
1122                                 return $id;
1123                         }
1124                 }
1125
1126                 // HTML4-style escaping
1127                 static $replace = array(
1128                         '%3A' => ':',
1129                         '%' => '.'
1130                 );
1131
1132                 $id = urlencode( strtr( $id, ' ', '_' ) );
1133                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1134
1135                 if ( !preg_match( '/^[a-zA-Z]/', $id ) && !in_array( 'noninitial', $options ) ) {
1136                         // Initial character must be a letter!
1137                         $id = "x$id";
1138                 }
1139                 return $id;
1140         }
1141
1142         /**
1143          * Given a value, escape it so that it can be used as a CSS class and
1144          * return it.
1145          *
1146          * @todo For extra validity, input should be validated UTF-8.
1147          *
1148          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1149          *
1150          * @param string $class
1151          * @return string
1152          */
1153         static function escapeClass( $class ) {
1154                 // Convert ugly stuff to underscores and kill underscores in ugly places
1155                 return rtrim( preg_replace(
1156                         array( '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ),
1157                         '_',
1158                         $class ), '_' );
1159         }
1160
1161         /**
1162          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1163          * This allows (generally harmless) entities like &#160; to survive.
1164          *
1165          * @param string $html HTML to escape
1166          * @return string Escaped input
1167          */
1168         static function escapeHtmlAllowEntities( $html ) {
1169                 $html = Sanitizer::decodeCharReferences( $html );
1170                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1171                 # hurt.
1172                 $html = htmlspecialchars( $html, ENT_QUOTES );
1173                 return $html;
1174         }
1175
1176         /**
1177          * Regex replace callback for armoring links against further processing.
1178          * @param array $matches
1179          * @return string
1180          */
1181         private static function armorLinksCallback( $matches ) {
1182                 return str_replace( ':', '&#58;', $matches[1] );
1183         }
1184
1185         /**
1186          * Return an associative array of attribute names and values from
1187          * a partial tag string. Attribute names are forces to lowercase,
1188          * character references are decoded to UTF-8 text.
1189          *
1190          * @param string $text
1191          * @return array
1192          */
1193         public static function decodeTagAttributes( $text ) {
1194                 if ( trim( $text ) == '' ) {
1195                         return array();
1196                 }
1197
1198                 $attribs = array();
1199                 $pairs = array();
1200                 if ( !preg_match_all(
1201                         self::getAttribsRegex(),
1202                         $text,
1203                         $pairs,
1204                         PREG_SET_ORDER ) ) {
1205                         return $attribs;
1206                 }
1207
1208                 foreach ( $pairs as $set ) {
1209                         $attribute = strtolower( $set[1] );
1210                         $value = Sanitizer::getTagAttributeCallback( $set );
1211
1212                         // Normalize whitespace
1213                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1214                         $value = trim( $value );
1215
1216                         // Decode character references
1217                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1218                 }
1219                 return $attribs;
1220         }
1221
1222         /**
1223          * Build a partial tag string from an associative array of attribute
1224          * names and values as returned by decodeTagAttributes.
1225          *
1226          * @param array $assoc_array
1227          * @return string
1228          */
1229         public static function safeEncodeTagAttributes( $assoc_array ) {
1230                 $attribs = array();
1231                 foreach ( $assoc_array as $attribute => $value ) {
1232                         $encAttribute = htmlspecialchars( $attribute );
1233                         $encValue = Sanitizer::safeEncodeAttribute( $value );
1234
1235                         $attribs[] = "$encAttribute=\"$encValue\"";
1236                 }
1237                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1238         }
1239
1240         /**
1241          * Pick the appropriate attribute value from a match set from the
1242          * attribs regex matches.
1243          *
1244          * @param array $set
1245          * @throws MWException When tag conditions are not met.
1246          * @return string
1247          */
1248         private static function getTagAttributeCallback( $set ) {
1249                 if ( isset( $set[6] ) ) {
1250                         # Illegal #XXXXXX color with no quotes.
1251                         return $set[6];
1252                 } elseif ( isset( $set[5] ) ) {
1253                         # No quotes.
1254                         return $set[5];
1255                 } elseif ( isset( $set[4] ) ) {
1256                         # Single-quoted
1257                         return $set[4];
1258                 } elseif ( isset( $set[3] ) ) {
1259                         # Double-quoted
1260                         return $set[3];
1261                 } elseif ( !isset( $set[2] ) ) {
1262                         # In XHTML, attributes must have a value.
1263                         # For 'reduced' form, return explicitly the attribute name here.
1264                         return $set[1];
1265                 } else {
1266                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1267                 }
1268         }
1269
1270         /**
1271          * Normalize whitespace and character references in an XML source-
1272          * encoded text for an attribute value.
1273          *
1274          * See http://www.w3.org/TR/REC-xml/#AVNormalize for background,
1275          * but note that we're not returning the value, but are returning
1276          * XML source fragments that will be slapped into output.
1277          *
1278          * @param string $text
1279          * @return string
1280          * @todo Remove, unused?
1281          */
1282         private static function normalizeAttributeValue( $text ) {
1283                 return str_replace( '"', '&quot;',
1284                         self::normalizeWhitespace(
1285                                 Sanitizer::normalizeCharReferences( $text ) ) );
1286         }
1287
1288         /**
1289          * @param string $text
1290          * @return string
1291          */
1292         private static function normalizeWhitespace( $text ) {
1293                 return preg_replace(
1294                         '/\r\n|[\x20\x0d\x0a\x09]/',
1295                         ' ',
1296                         $text );
1297         }
1298
1299         /**
1300          * Normalizes whitespace in a section name, such as might be returned
1301          * by Parser::stripSectionName(), for use in the id's that are used for
1302          * section links.
1303          *
1304          * @param string $section
1305          * @return string
1306          */
1307         static function normalizeSectionNameWhitespace( $section ) {
1308                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1309         }
1310
1311         /**
1312          * Ensure that any entities and character references are legal
1313          * for XML and XHTML specifically. Any stray bits will be
1314          * &amp;-escaped to result in a valid text fragment.
1315          *
1316          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1317          *   numericized (this way we're well-formed even without a DTD)
1318          * b. any numeric char refs must be legal chars, not invalid or forbidden
1319          * c. use lower cased "&#x", not "&#X"
1320          * d. fix or reject non-valid attributes
1321          *
1322          * @param string $text
1323          * @return string
1324          * @private
1325          */
1326         static function normalizeCharReferences( $text ) {
1327                 return preg_replace_callback(
1328                         self::CHAR_REFS_REGEX,
1329                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1330                         $text );
1331         }
1332
1333         /**
1334          * @param string $matches
1335          * @return string
1336          */
1337         static function normalizeCharReferencesCallback( $matches ) {
1338                 $ret = null;
1339                 if ( $matches[1] != '' ) {
1340                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1341                 } elseif ( $matches[2] != '' ) {
1342                         $ret = Sanitizer::decCharReference( $matches[2] );
1343                 } elseif ( $matches[3] != '' ) {
1344                         $ret = Sanitizer::hexCharReference( $matches[3] );
1345                 }
1346                 if ( is_null( $ret ) ) {
1347                         return htmlspecialchars( $matches[0] );
1348                 } else {
1349                         return $ret;
1350                 }
1351         }
1352
1353         /**
1354          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1355          * return the equivalent numeric entity reference (except for the core &lt;
1356          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1357          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1358          * pseudo-entity source (eg &amp;foo;)
1359          *
1360          * @param string $name
1361          * @return string
1362          */
1363         static function normalizeEntity( $name ) {
1364                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1365                         return '&' . self::$htmlEntityAliases[$name] . ';';
1366                 } elseif ( in_array( $name, array( 'lt', 'gt', 'amp', 'quot' ) ) ) {
1367                         return "&$name;";
1368                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1369                         return '&#' . self::$htmlEntities[$name] . ';';
1370                 } else {
1371                         return "&amp;$name;";
1372                 }
1373         }
1374
1375         /**
1376          * @param int $codepoint
1377          * @return null|string
1378          */
1379         static function decCharReference( $codepoint ) {
1380                 $point = intval( $codepoint );
1381                 if ( Sanitizer::validateCodepoint( $point ) ) {
1382                         return sprintf( '&#%d;', $point );
1383                 } else {
1384                         return null;
1385                 }
1386         }
1387
1388         /**
1389          * @param int $codepoint
1390          * @return null|string
1391          */
1392         static function hexCharReference( $codepoint ) {
1393                 $point = hexdec( $codepoint );
1394                 if ( Sanitizer::validateCodepoint( $point ) ) {
1395                         return sprintf( '&#x%x;', $point );
1396                 } else {
1397                         return null;
1398                 }
1399         }
1400
1401         /**
1402          * Returns true if a given Unicode codepoint is a valid character in XML.
1403          * @param int $codepoint
1404          * @return bool
1405          */
1406         private static function validateCodepoint( $codepoint ) {
1407                 return $codepoint == 0x09
1408                         || $codepoint == 0x0a
1409                         || $codepoint == 0x0d
1410                         || ( $codepoint >= 0x20 && $codepoint <= 0xd7ff )
1411                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1412                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1413         }
1414
1415         /**
1416          * Decode any character references, numeric or named entities,
1417          * in the text and return a UTF-8 string.
1418          *
1419          * @param string $text
1420          * @return string
1421          */
1422         public static function decodeCharReferences( $text ) {
1423                 return preg_replace_callback(
1424                         self::CHAR_REFS_REGEX,
1425                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1426                         $text );
1427         }
1428
1429         /**
1430          * Decode any character references, numeric or named entities,
1431          * in the next and normalize the resulting string. (bug 14952)
1432          *
1433          * This is useful for page titles, not for text to be displayed,
1434          * MediaWiki allows HTML entities to escape normalization as a feature.
1435          *
1436          * @param string $text Already normalized, containing entities
1437          * @return string Still normalized, without entities
1438          */
1439         public static function decodeCharReferencesAndNormalize( $text ) {
1440                 global $wgContLang;
1441                 $text = preg_replace_callback(
1442                         self::CHAR_REFS_REGEX,
1443                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1444                         $text, /* limit */ -1, $count );
1445
1446                 if ( $count ) {
1447                         return $wgContLang->normalize( $text );
1448                 } else {
1449                         return $text;
1450                 }
1451         }
1452
1453         /**
1454          * @param string $matches
1455          * @return string
1456          */
1457         static function decodeCharReferencesCallback( $matches ) {
1458                 if ( $matches[1] != '' ) {
1459                         return Sanitizer::decodeEntity( $matches[1] );
1460                 } elseif ( $matches[2] != '' ) {
1461                         return Sanitizer::decodeChar( intval( $matches[2] ) );
1462                 } elseif ( $matches[3] != '' ) {
1463                         return Sanitizer::decodeChar( hexdec( $matches[3] ) );
1464                 }
1465                 # Last case should be an ampersand by itself
1466                 return $matches[0];
1467         }
1468
1469         /**
1470          * Return UTF-8 string for a codepoint if that is a valid
1471          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1472          * @param int $codepoint
1473          * @return string
1474          * @private
1475          */
1476         static function decodeChar( $codepoint ) {
1477                 if ( Sanitizer::validateCodepoint( $codepoint ) ) {
1478                         return codepointToUtf8( $codepoint );
1479                 } else {
1480                         return UTF8_REPLACEMENT;
1481                 }
1482         }
1483
1484         /**
1485          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1486          * return the UTF-8 encoding of that character. Otherwise, returns
1487          * pseudo-entity source (eg "&foo;")
1488          *
1489          * @param string $name
1490          * @return string
1491          */
1492         static function decodeEntity( $name ) {
1493                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1494                         $name = self::$htmlEntityAliases[$name];
1495                 }
1496                 if ( isset( self::$htmlEntities[$name] ) ) {
1497                         return codepointToUtf8( self::$htmlEntities[$name] );
1498                 } else {
1499                         return "&$name;";
1500                 }
1501         }
1502
1503         /**
1504          * Fetch the whitelist of acceptable attributes for a given element name.
1505          *
1506          * @param string $element
1507          * @return array
1508          */
1509         static function attributeWhitelist( $element ) {
1510                 $list = Sanitizer::setupAttributeWhitelist();
1511                 return isset( $list[$element] )
1512                         ? $list[$element]
1513                         : array();
1514         }
1515
1516         /**
1517          * Foreach array key (an allowed HTML element), return an array
1518          * of allowed attributes
1519          * @return array
1520          */
1521         static function setupAttributeWhitelist() {
1522                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
1523                 static $whitelist, $staticInitialised;
1524
1525                 $globalContext = implode( '-', compact( 'wgAllowRdfaAttributes', 'wgAllowMicrodataAttributes' ) );
1526
1527                 if ( $whitelist !== null && $staticInitialised == $globalContext ) {
1528                         return $whitelist;
1529                 }
1530
1531                 $common = array(
1532                         # HTML
1533                         'id',
1534                         'class',
1535                         'style',
1536                         'lang',
1537                         'dir',
1538                         'title',
1539
1540                         # WAI-ARIA
1541                         'role',
1542                 );
1543
1544                 if ( $wgAllowRdfaAttributes ) {
1545                         # RDFa attributes as specified in section 9 of
1546                         # http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1547                         $common = array_merge( $common, array(
1548                                 'about', 'property', 'resource', 'datatype', 'typeof',
1549                         ) );
1550                 }
1551
1552                 if ( $wgAllowMicrodataAttributes ) {
1553                         # add HTML5 microdata tags as specified by
1554                         # http://www.whatwg.org/html/microdata.html#the-microdata-model
1555                         $common = array_merge( $common, array(
1556                                 'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1557                         ) );
1558                 }
1559
1560                 $block = array_merge( $common, array( 'align' ) );
1561                 $tablealign = array( 'align', 'valign' );
1562                 $tablecell = array(
1563                         'abbr',
1564                         'axis',
1565                         'headers',
1566                         'scope',
1567                         'rowspan',
1568                         'colspan',
1569                         'nowrap', # deprecated
1570                         'width', # deprecated
1571                         'height', # deprecated
1572                         'bgcolor', # deprecated
1573                 );
1574
1575                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1576                 # See: http://www.w3.org/TR/html4/
1577                 $whitelist = array(
1578                         # 7.5.4
1579                         'div'        => $block,
1580                         'center'     => $common, # deprecated
1581                         'span'       => $common,
1582
1583                         # 7.5.5
1584                         'h1'         => $block,
1585                         'h2'         => $block,
1586                         'h3'         => $block,
1587                         'h4'         => $block,
1588                         'h5'         => $block,
1589                         'h6'         => $block,
1590
1591                         # 7.5.6
1592                         # address
1593
1594                         # 8.2.4
1595                         'bdo'        => $common,
1596
1597                         # 9.2.1
1598                         'em'         => $common,
1599                         'strong'     => $common,
1600                         'cite'       => $common,
1601                         'dfn'        => $common,
1602                         'code'       => $common,
1603                         'samp'       => $common,
1604                         'kbd'        => $common,
1605                         'var'        => $common,
1606                         'abbr'       => $common,
1607                         # acronym
1608
1609                         # 9.2.2
1610                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1611                         'q'          => array_merge( $common, array( 'cite' ) ),
1612
1613                         # 9.2.3
1614                         'sub'        => $common,
1615                         'sup'        => $common,
1616
1617                         # 9.3.1
1618                         'p'          => $block,
1619
1620                         # 9.3.2
1621                         'br'         => array_merge( $common, array( 'clear' ) ),
1622
1623                         # http://www.whatwg.org/html/text-level-semantics.html#the-wbr-element
1624                         'wbr'        => $common,
1625
1626                         # 9.3.4
1627                         'pre'        => array_merge( $common, array( 'width' ) ),
1628
1629                         # 9.4
1630                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1631                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1632
1633                         # 10.2
1634                         'ul'         => array_merge( $common, array( 'type' ) ),
1635                         'ol'         => array_merge( $common, array( 'type', 'start' ) ),
1636                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1637
1638                         # 10.3
1639                         'dl'         => $common,
1640                         'dd'         => $common,
1641                         'dt'         => $common,
1642
1643                         # 11.2.1
1644                         'table'      => array_merge( $common,
1645                                                                 array( 'summary', 'width', 'border', 'frame',
1646                                                                                 'rules', 'cellspacing', 'cellpadding',
1647                                                                                 'align', 'bgcolor',
1648                                                                 ) ),
1649
1650                         # 11.2.2
1651                         'caption'    => $block,
1652
1653                         # 11.2.3
1654                         'thead'      => $common,
1655                         'tfoot'      => $common,
1656                         'tbody'      => $common,
1657
1658                         # 11.2.4
1659                         'colgroup'   => array_merge( $common, array( 'span' ) ),
1660                         'col'        => array_merge( $common, array( 'span' ) ),
1661
1662                         # 11.2.5
1663                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1664
1665                         # 11.2.6
1666                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1667                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1668
1669                         # 12.2
1670                         # NOTE: <a> is not allowed directly, but the attrib
1671                         # whitelist is used from the Parser object
1672                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1673
1674                         # 13.2
1675                         # Not usually allowed, but may be used for extension-style hooks
1676                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1677                         # true
1678                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1679
1680                         # 15.2.1
1681                         'tt'         => $common,
1682                         'b'          => $common,
1683                         'i'          => $common,
1684                         'big'        => $common,
1685                         'small'      => $common,
1686                         'strike'     => $common,
1687                         's'          => $common,
1688                         'u'          => $common,
1689
1690                         # 15.2.2
1691                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1692                         # basefont
1693
1694                         # 15.3
1695                         'hr'         => array_merge( $common, array( 'width' ) ),
1696
1697                         # HTML Ruby annotation text module, simple ruby only.
1698                         # http://www.whatwg.org/html/text-level-semantics.html#the-ruby-element
1699                         'ruby'       => $common,
1700                         # rbc
1701                         'rb'         => $common,
1702                         'rp'         => $common,
1703                         'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),
1704                         'rtc'         => $common,
1705
1706                         # MathML root element, where used for extensions
1707                         # 'title' may not be 100% valid here; it's XHTML
1708                         # http://www.w3.org/TR/REC-MathML/
1709                         'math'       => array( 'class', 'style', 'id', 'title' ),
1710
1711                         # HTML 5 section 4.6
1712                         'bdi' => $common,
1713
1714                         # HTML5 elements, defined by:
1715                         # http://www.whatwg.org/html/
1716                         'data' => array_merge( $common, array( 'value' ) ),
1717                         'time' => array_merge( $common, array( 'datetime' ) ),
1718                         'mark' => $common,
1719
1720                         // meta and link are only permitted by removeHTMLtags when Microdata
1721                         // is enabled so we don't bother adding a conditional to hide these
1722                         // Also meta and link are only valid in WikiText as Microdata elements
1723                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1724                         // So we don't bother including $common attributes that have no purpose.
1725                         'meta' => array( 'itemprop', 'content' ),
1726                         'link' => array( 'itemprop', 'href' ),
1727                 );
1728
1729                 $staticInitialised = $globalContext;
1730
1731                 return $whitelist;
1732         }
1733
1734         /**
1735          * Take a fragment of (potentially invalid) HTML and return
1736          * a version with any tags removed, encoded as plain text.
1737          *
1738          * Warning: this return value must be further escaped for literal
1739          * inclusion in HTML output as of 1.10!
1740          *
1741          * @param string $text HTML fragment
1742          * @return string
1743          */
1744         static function stripAllTags( $text ) {
1745                 # Actual <tags>
1746                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1747
1748                 # Normalize &entities and whitespace
1749                 $text = self::decodeCharReferences( $text );
1750                 $text = self::normalizeWhitespace( $text );
1751
1752                 return $text;
1753         }
1754
1755         /**
1756          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1757          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1758          * PHP 5.1 doesn't.
1759          *
1760          * Use for passing XHTML fragments to PHP's XML parsing functions
1761          *
1762          * @return string
1763          */
1764         static function hackDocType() {
1765                 $out = "<!DOCTYPE html [\n";
1766                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
1767                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1768                 }
1769                 $out .= "]>\n";
1770                 return $out;
1771         }
1772
1773         /**
1774          * @param string $url
1775          * @return mixed|string
1776          */
1777         static function cleanUrl( $url ) {
1778                 # Normalize any HTML entities in input. They will be
1779                 # re-escaped by makeExternalLink().
1780                 $url = Sanitizer::decodeCharReferences( $url );
1781
1782                 # Escape any control characters introduced by the above step
1783                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1784                         array( __CLASS__, 'cleanUrlCallback' ), $url );
1785
1786                 # Validate hostname portion
1787                 $matches = array();
1788                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1789                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1790
1791                         // Characters that will be ignored in IDNs.
1792                         // http://tools.ietf.org/html/3454#section-3.1
1793                         // Strip them before further processing so blacklists and such work.
1794                         $strip = "/
1795                                 \\s|          # general whitespace
1796                                 \xc2\xad|     # 00ad SOFT HYPHEN
1797                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1798                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1799                                 \xe2\x81\xa0| # 2060 WORD JOINER
1800                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1801                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1802                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1803                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1804                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1805                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1806                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1807                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
1808                                 /xuD";
1809
1810                         $host = preg_replace( $strip, '', $host );
1811
1812                         // @todo FIXME: Validate hostnames here
1813
1814                         return $protocol . $host . $rest;
1815                 } else {
1816                         return $url;
1817                 }
1818         }
1819
1820         /**
1821          * @param array $matches
1822          * @return string
1823          */
1824         static function cleanUrlCallback( $matches ) {
1825                 return urlencode( $matches[0] );
1826         }
1827
1828         /**
1829          * Does a string look like an e-mail address?
1830          *
1831          * This validates an email address using an HTML5 specification found at:
1832          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
1833          * Which as of 2011-01-24 says:
1834          *
1835          *   A valid e-mail address is a string that matches the ABNF production
1836          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1837          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1838          *   3.5.
1839          *
1840          * This function is an implementation of the specification as requested in
1841          * bug 22449.
1842          *
1843          * Client-side forms will use the same standard validation rules via JS or
1844          * HTML 5 validation; additional restrictions can be enforced server-side
1845          * by extensions via the 'isValidEmailAddr' hook.
1846          *
1847          * Note that this validation doesn't 100% match RFC 2822, but is believed
1848          * to be liberal enough for wide use. Some invalid addresses will still
1849          * pass validation here.
1850          *
1851          * @since 1.18
1852          *
1853          * @param string $addr E-mail address
1854          * @return bool
1855          */
1856         public static function validateEmail( $addr ) {
1857                 $result = null;
1858                 if ( !wfRunHooks( 'isValidEmailAddr', array( $addr, &$result ) ) ) {
1859                         return $result;
1860                 }
1861
1862                 // Please note strings below are enclosed in brackets [], this make the
1863                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1864                 // See bug 26948
1865                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
1866                 $rfc1034_ldh_str = "a-z0-9\\-";
1867
1868                 $html5_email_regexp = "/
1869                 ^                      # start of string
1870                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1871                 @                      # 'apostrophe'
1872                 [$rfc1034_ldh_str]+       # First domain part
1873                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1874                 $                      # End of string
1875                 /ix"; // case Insensitive, eXtended
1876
1877                 return (bool)preg_match( $html5_email_regexp, $addr );
1878         }
1879 }