includes/Sanitizer.php

   1 <?php
   2 /**
   3  * HTML sanitizer for %MediaWiki.
   4  *
   5  * Copyright © 2002-2005 Brion Vibber <brion@pobox.com> et al
   6  * http://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Parser
  25  */
  26
  27 /**
  28  * HTML sanitizer for MediaWiki
  29  * @ingroup Parser
  30  */
  31 class Sanitizer {
  32         /**
  33          * Regular expression to match various types of character references in
  34          * Sanitizer::normalizeCharReferences and Sanitizer::decodeCharReferences
  35          */
  36         const CHAR_REFS_REGEX =
  37                 '/&([A-Za-z0-9\x80-\xff]+);
  38                  |&\#([0-9]+);
  39                  |&\#[xX]([0-9A-Fa-f]+);
  40                  |(&)/x';
  41
  42         /**
  43          * Blacklist for evil uris like javascript:
  44          * WARNING: DO NOT use this in any place that actually requires blacklisting
  45          * for security reasons. There are NUMEROUS[1] ways to bypass blacklisting, the
  46          * only way to be secure from javascript: uri based xss vectors is to whitelist
  47          * things that you know are safe and deny everything else.
  48          * [1]: http://ha.ckers.org/xss.html
  49          */
  50         const EVIL_URI_PATTERN = '!(^|\s|\*/\s*)(javascript|vbscript)([^\w]|$)!i';
  51         const XMLNS_ATTRIBUTE_PATTERN = "/^xmlns:[:A-Z_a-z-.0-9]+$/";
  52
  53         /**
  54          * List of all named character entities defined in HTML 4.01
  55          * http://www.w3.org/TR/html4/sgml/entities.html
  56          * As well as &apos; which is only defined starting in XHTML1.
  57          */
  58         private static $htmlEntities = array(
  59                 'Aacute'   => 193,
  60                 'aacute'   => 225,
  61                 'Acirc'    => 194,
  62                 'acirc'    => 226,
  63                 'acute'    => 180,
  64                 'AElig'    => 198,
  65                 'aelig'    => 230,
  66                 'Agrave'   => 192,
  67                 'agrave'   => 224,
  68                 'alefsym'  => 8501,
  69                 'Alpha'    => 913,
  70                 'alpha'    => 945,
  71                 'amp'      => 38,
  72                 'and'      => 8743,
  73                 'ang'      => 8736,
  74                 'apos'     => 39, // New in XHTML & HTML 5; avoid in output for compatibility with IE.
  75                 'Aring'    => 197,
  76                 'aring'    => 229,
  77                 'asymp'    => 8776,
  78                 'Atilde'   => 195,
  79                 'atilde'   => 227,
  80                 'Auml'     => 196,
  81                 'auml'     => 228,
  82                 'bdquo'    => 8222,
  83                 'Beta'     => 914,
  84                 'beta'     => 946,
  85                 'brvbar'   => 166,
  86                 'bull'     => 8226,
  87                 'cap'      => 8745,
  88                 'Ccedil'   => 199,
  89                 'ccedil'   => 231,
  90                 'cedil'    => 184,
  91                 'cent'     => 162,
  92                 'Chi'      => 935,
  93                 'chi'      => 967,
  94                 'circ'     => 710,
  95                 'clubs'    => 9827,
  96                 'cong'     => 8773,
  97                 'copy'     => 169,
  98                 'crarr'    => 8629,
  99                 'cup'      => 8746,
 100                 'curren'   => 164,
 101                 'dagger'   => 8224,
 102                 'Dagger'   => 8225,
 103                 'darr'     => 8595,
 104                 'dArr'     => 8659,
 105                 'deg'      => 176,
 106                 'Delta'    => 916,
 107                 'delta'    => 948,
 108                 'diams'    => 9830,
 109                 'divide'   => 247,
 110                 'Eacute'   => 201,
 111                 'eacute'   => 233,
 112                 'Ecirc'    => 202,
 113                 'ecirc'    => 234,
 114                 'Egrave'   => 200,
 115                 'egrave'   => 232,
 116                 'empty'    => 8709,
 117                 'emsp'     => 8195,
 118                 'ensp'     => 8194,
 119                 'Epsilon'  => 917,
 120                 'epsilon'  => 949,
 121                 'equiv'    => 8801,
 122                 'Eta'      => 919,
 123                 'eta'      => 951,
 124                 'ETH'      => 208,
 125                 'eth'      => 240,
 126                 'Euml'     => 203,
 127                 'euml'     => 235,
 128                 'euro'     => 8364,
 129                 'exist'    => 8707,
 130                 'fnof'     => 402,
 131                 'forall'   => 8704,
 132                 'frac12'   => 189,
 133                 'frac14'   => 188,
 134                 'frac34'   => 190,
 135                 'frasl'    => 8260,
 136                 'Gamma'    => 915,
 137                 'gamma'    => 947,
 138                 'ge'       => 8805,
 139                 'gt'       => 62,
 140                 'harr'     => 8596,
 141                 'hArr'     => 8660,
 142                 'hearts'   => 9829,
 143                 'hellip'   => 8230,
 144                 'Iacute'   => 205,
 145                 'iacute'   => 237,
 146                 'Icirc'    => 206,
 147                 'icirc'    => 238,
 148                 'iexcl'    => 161,
 149                 'Igrave'   => 204,
 150                 'igrave'   => 236,
 151                 'image'    => 8465,
 152                 'infin'    => 8734,
 153                 'int'      => 8747,
 154                 'Iota'     => 921,
 155                 'iota'     => 953,
 156                 'iquest'   => 191,
 157                 'isin'     => 8712,
 158                 'Iuml'     => 207,
 159                 'iuml'     => 239,
 160                 'Kappa'    => 922,
 161                 'kappa'    => 954,
 162                 'Lambda'   => 923,
 163                 'lambda'   => 955,
 164                 'lang'     => 9001,
 165                 'laquo'    => 171,
 166                 'larr'     => 8592,
 167                 'lArr'     => 8656,
 168                 'lceil'    => 8968,
 169                 'ldquo'    => 8220,
 170                 'le'       => 8804,
 171                 'lfloor'   => 8970,
 172                 'lowast'   => 8727,
 173                 'loz'      => 9674,
 174                 'lrm'      => 8206,
 175                 'lsaquo'   => 8249,
 176                 'lsquo'    => 8216,
 177                 'lt'       => 60,
 178                 'macr'     => 175,
 179                 'mdash'    => 8212,
 180                 'micro'    => 181,
 181                 'middot'   => 183,
 182                 'minus'    => 8722,
 183                 'Mu'       => 924,
 184                 'mu'       => 956,
 185                 'nabla'    => 8711,
 186                 'nbsp'     => 160,
 187                 'ndash'    => 8211,
 188                 'ne'       => 8800,
 189                 'ni'       => 8715,
 190                 'not'      => 172,
 191                 'notin'    => 8713,
 192                 'nsub'     => 8836,
 193                 'Ntilde'   => 209,
 194                 'ntilde'   => 241,
 195                 'Nu'       => 925,
 196                 'nu'       => 957,
 197                 'Oacute'   => 211,
 198                 'oacute'   => 243,
 199                 'Ocirc'    => 212,
 200                 'ocirc'    => 244,
 201                 'OElig'    => 338,
 202                 'oelig'    => 339,
 203                 'Ograve'   => 210,
 204                 'ograve'   => 242,
 205                 'oline'    => 8254,
 206                 'Omega'    => 937,
 207                 'omega'    => 969,
 208                 'Omicron'  => 927,
 209                 'omicron'  => 959,
 210                 'oplus'    => 8853,
 211                 'or'       => 8744,
 212                 'ordf'     => 170,
 213                 'ordm'     => 186,
 214                 'Oslash'   => 216,
 215                 'oslash'   => 248,
 216                 'Otilde'   => 213,
 217                 'otilde'   => 245,
 218                 'otimes'   => 8855,
 219                 'Ouml'     => 214,
 220                 'ouml'     => 246,
 221                 'para'     => 182,
 222                 'part'     => 8706,
 223                 'permil'   => 8240,
 224                 'perp'     => 8869,
 225                 'Phi'      => 934,
 226                 'phi'      => 966,
 227                 'Pi'       => 928,
 228                 'pi'       => 960,
 229                 'piv'      => 982,
 230                 'plusmn'   => 177,
 231                 'pound'    => 163,
 232                 'prime'    => 8242,
 233                 'Prime'    => 8243,
 234                 'prod'     => 8719,
 235                 'prop'     => 8733,
 236                 'Psi'      => 936,
 237                 'psi'      => 968,
 238                 'quot'     => 34,
 239                 'radic'    => 8730,
 240                 'rang'     => 9002,
 241                 'raquo'    => 187,
 242                 'rarr'     => 8594,
 243                 'rArr'     => 8658,
 244                 'rceil'    => 8969,
 245                 'rdquo'    => 8221,
 246                 'real'     => 8476,
 247                 'reg'      => 174,
 248                 'rfloor'   => 8971,
 249                 'Rho'      => 929,
 250                 'rho'      => 961,
 251                 'rlm'      => 8207,
 252                 'rsaquo'   => 8250,
 253                 'rsquo'    => 8217,
 254                 'sbquo'    => 8218,
 255                 'Scaron'   => 352,
 256                 'scaron'   => 353,
 257                 'sdot'     => 8901,
 258                 'sect'     => 167,
 259                 'shy'      => 173,
 260                 'Sigma'    => 931,
 261                 'sigma'    => 963,
 262                 'sigmaf'   => 962,
 263                 'sim'      => 8764,
 264                 'spades'   => 9824,
 265                 'sub'      => 8834,
 266                 'sube'     => 8838,
 267                 'sum'      => 8721,
 268                 'sup'      => 8835,
 269                 'sup1'     => 185,
 270                 'sup2'     => 178,
 271                 'sup3'     => 179,
 272                 'supe'     => 8839,
 273                 'szlig'    => 223,
 274                 'Tau'      => 932,
 275                 'tau'      => 964,
 276                 'there4'   => 8756,
 277                 'Theta'    => 920,
 278                 'theta'    => 952,
 279                 'thetasym' => 977,
 280                 'thinsp'   => 8201,
 281                 'THORN'    => 222,
 282                 'thorn'    => 254,
 283                 'tilde'    => 732,
 284                 'times'    => 215,
 285                 'trade'    => 8482,
 286                 'Uacute'   => 218,
 287                 'uacute'   => 250,
 288                 'uarr'     => 8593,
 289                 'uArr'     => 8657,
 290                 'Ucirc'    => 219,
 291                 'ucirc'    => 251,
 292                 'Ugrave'   => 217,
 293                 'ugrave'   => 249,
 294                 'uml'      => 168,
 295                 'upsih'    => 978,
 296                 'Upsilon'  => 933,
 297                 'upsilon'  => 965,
 298                 'Uuml'     => 220,
 299                 'uuml'     => 252,
 300                 'weierp'   => 8472,
 301                 'Xi'       => 926,
 302                 'xi'       => 958,
 303                 'Yacute'   => 221,
 304                 'yacute'   => 253,
 305                 'yen'      => 165,
 306                 'Yuml'     => 376,
 307                 'yuml'     => 255,
 308                 'Zeta'     => 918,
 309                 'zeta'     => 950,
 310                 'zwj'      => 8205,
 311                 'zwnj'     => 8204
 312         );
 313
 314         /**
 315          * Character entity aliases accepted by MediaWiki
 316          */
 317         private static $htmlEntityAliases = array(
 318                 'רלמ' => 'rlm',
 319                 'رلم' => 'rlm',
 320         );
 321
 322         /**
 323          * Lazy-initialised attributes regex, see getAttribsRegex()
 324          */
 325         private static $attribsRegex;
 326
 327         /**
 328          * Regular expression to match HTML/XML attribute pairs within a tag.
 329          * Allows some... latitude.
 330          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 331          */
 332         static function getAttribsRegex() {
 333                 if ( self::$attribsRegex === null ) {
 334                         $attribFirst = '[:A-Z_a-z0-9]';
 335                         $attrib = '[:A-Z_a-z-.0-9]';
 336                         $space = '[\x09\x0a\x0d\x20]';
 337                         self::$attribsRegex =
 338                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 339                                   ($space*=$space*
 340                                         (?:
 341                                          # The attribute value: quoted or alone
 342                                           \"([^<\"]*)\"
 343                                          | '([^<']*)'
 344                                          |  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)
 345                                          |  (\#[0-9a-fA-F]+) # Technically wrong, but lots of
 346                                                                                  # colors are specified like this.
 347                                                                                  # We'll be normalizing it.
 348                                         )
 349                                 )?(?=$space|\$)/sx";
 350                 }
 351                 return self::$attribsRegex;
 352         }
 353
 354         /**
 355          * Cleans up HTML, removes dangerous tags and attributes, and
 356          * removes HTML comments
 357          * @private
 358          * @param string $text
 359          * @param callable $processCallback Callback to do any variable or parameter
 360          *   replacements in HTML attribute values
 361          * @param array $args Arguments for the processing callback
 362          * @param array $extratags For any extra tags to include
 363          * @param array $removetags For any tags (default or extra) to exclude
 364          * @return string
 365          */
 366         static function removeHTMLtags( $text, $processCallback = null,
 367                 $args = array(), $extratags = array(), $removetags = array()
 368         ) {
 369                 global $wgUseTidy, $wgAllowMicrodataAttributes, $wgAllowImageTag;
 370
 371                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 372                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 373
 374                 wfProfileIn( __METHOD__ );
 375
 376                 // Base our staticInitialised variable off of the global config state so that if the globals
 377                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 378                 $globalContext = implode( '-', compact( 'wgAllowMicrodataAttributes', 'wgAllowImageTag' ) );
 379                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 380
 381                         $htmlpairsStatic = array( # Tags that must be closed
 382                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 383                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 384                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 385                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 386                                 'ruby', 'rt', 'rb', 'rp', 'p', 'span', 'abbr', 'dfn',
 387                                 'kbd', 'samp', 'data', 'time', 'mark'
 388                         );
 389                         $htmlsingle = array(
 390                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd'
 391                         );
 392                         $htmlsingleonly = array( # Elements that cannot have close tags
 393                                 'br', 'wbr', 'hr'
 394                         );
 395                         if ( $wgAllowMicrodataAttributes ) {
 396                                 $htmlsingle[] = $htmlsingleonly[] = 'meta';
 397                                 $htmlsingle[] = $htmlsingleonly[] = 'link';
 398                         }
 399                         $htmlnest = array( # Tags that can be nested--??
 400                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 401                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 402                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 403                         );
 404                         $tabletags = array( # Can only appear inside table, we will close them
 405                                 'td', 'th', 'tr',
 406                         );
 407                         $htmllist = array( # Tags used by list
 408                                 'ul', 'ol',
 409                         );
 410                         $listtags = array( # Tags that can appear in a list
 411                                 'li',
 412                         );
 413
 414                         if ( $wgAllowImageTag ) {
 415                                 $htmlsingle[] = 'img';
 416                                 $htmlsingleonly[] = 'img';
 417                         }
 418
 419                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 420                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 421
 422                         # Convert them all to hashtables for faster lookup
 423                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 424                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 425                         foreach ( $vars as $var ) {
 426                                 $$var = array_flip( $$var );
 427                         }
 428                         $staticInitialised = $globalContext;
 429                 }
 430                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 431                 $extratags = array_flip( $extratags );
 432                 $removetags = array_flip( $removetags );
 433                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 434                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 435
 436                 # Remove HTML comments
 437                 $text = Sanitizer::removeHTMLcomments( $text );
 438                 $bits = explode( '<', $text );
 439                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 440                 if ( !$wgUseTidy ) {
 441                         $tagstack = $tablestack = array();
 442                         foreach ( $bits as $x ) {
 443                                 $regs = array();
 444                                 # $slash: Does the current element start with a '/'?
 445                                 # $t: Current element name
 446                                 # $params: String between element name and >
 447                                 # $brace: Ending '>' or '/>'
 448                                 # $rest: Everything until the next element of $bits
 449                                 if ( preg_match( '!^(/?)([^\\s/>]+)([^>]*?)(/{0,1}>)([^<]*)$!', $x, $regs ) ) {
 450                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 451                                 } else {
 452                                         $slash = $t = $params = $brace = $rest = null;
 453                                 }
 454
 455                                 $badtag = false;
 456                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 457                                         # Check our stack
 458                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 459                                                 $badtag = true;
 460                                         } elseif ( $slash ) {
 461                                                 # Closing a tag... is it the one we just opened?
 462                                                 $ot = @array_pop( $tagstack );
 463                                                 if ( $ot != $t ) {
 464                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 465                                                                 # Pop all elements with an optional close tag
 466                                                                 # and see if we find a match below them
 467                                                                 $optstack = array();
 468                                                                 array_push( $optstack, $ot );
 469                                                                 wfSuppressWarnings();
 470                                                                 $ot = array_pop( $tagstack );
 471                                                                 wfRestoreWarnings();
 472                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 473                                                                         array_push( $optstack, $ot );
 474                                                                         wfSuppressWarnings();
 475                                                                         $ot = array_pop( $tagstack );
 476                                                                         wfRestoreWarnings();
 477                                                                 }
 478                                                                 if ( $t != $ot ) {
 479                                                                         # No match. Push the optional elements back again
 480                                                                         $badtag = true;
 481                                                                         wfSuppressWarnings();
 482                                                                         $ot = array_pop( $optstack );
 483                                                                         wfRestoreWarnings();
 484                                                                         while ( $ot ) {
 485                                                                                 array_push( $tagstack, $ot );
 486                                                                                 wfSuppressWarnings();
 487                                                                                 $ot = array_pop( $optstack );
 488                                                                                 wfRestoreWarnings();
 489                                                                         }
 490                                                                 }
 491                                                         } else {
 492                                                                 @array_push( $tagstack, $ot );
 493                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 494                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 495                                                                         $badtag = true;
 496                                                                 }
 497                                                         }
 498                                                 } else {
 499                                                         if ( $t == 'table' ) {
 500                                                                 $tagstack = array_pop( $tablestack );
 501                                                         }
 502                                                 }
 503                                                 $newparams = '';
 504                                         } else {
 505                                                 # Keep track for later
 506                                                 if ( isset( $tabletags[$t] ) &&
 507                                                 !in_array( 'table', $tagstack ) ) {
 508                                                         $badtag = true;
 509                                                 } elseif ( in_array( $t, $tagstack ) &&
 510                                                 !isset( $htmlnest[$t] ) ) {
 511                                                         $badtag = true;
 512                                                 # Is it a self closed htmlpair ? (bug 5487)
 513                                                 } elseif ( $brace == '/>' &&
 514                                                 isset( $htmlpairs[$t] ) ) {
 515                                                         $badtag = true;
 516                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 517                                                         # Hack to force empty tag for unclosable elements
 518                                                         $brace = '/>';
 519                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 520                                                         # Hack to not close $htmlsingle tags
 521                                                         $brace = null;
 522                                                         # Still need to push this optionally-closed tag to
 523                                                         # the tag stack so that we can match end tags
 524                                                         # instead of marking them as bad.
 525                                                         array_push( $tagstack, $t );
 526                                                 } elseif ( isset( $tabletags[$t] )
 527                                                 && in_array( $t, $tagstack ) ) {
 528                                                         // New table tag but forgot to close the previous one
 529                                                         $text .= "</$t>";
 530                                                 } else {
 531                                                         if ( $t == 'table' ) {
 532                                                                 array_push( $tablestack, $tagstack );
 533                                                                 $tagstack = array();
 534                                                         }
 535                                                         array_push( $tagstack, $t );
 536                                                 }
 537
 538                                                 # Replace any variables or template parameters with
 539                                                 # plaintext results.
 540                                                 if ( is_callable( $processCallback ) ) {
 541                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 542                                                 }
 543
 544                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 545                                                         $badtag = true;
 546                                                 }
 547
 548                                                 # Strip non-approved attributes from the tag
 549                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 550                                         }
 551                                         if ( !$badtag ) {
 552                                                 $rest = str_replace( '>', '&gt;', $rest );
 553                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 554                                                 $text .= "<$slash$t$newparams$close>$rest";
 555                                                 continue;
 556                                         }
 557                                 }
 558                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 559                         }
 560                         # Close off any remaining tags
 561                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 562                                 $text .= "</$t>\n";
 563                                 if ( $t == 'table' ) {
 564                                         $tagstack = array_pop( $tablestack );
 565                                 }
 566                         }
 567                 } else {
 568                         # this might be possible using tidy itself
 569                         foreach ( $bits as $x ) {
 570                                 preg_match( '/^(\\/?)(\\w+)([^>]*?)(\\/{0,1}>)([^<]*)$/',
 571                                 $x, $regs );
 572                                 @list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 573                                 $badtag = false;
 574                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 575                                         if ( is_callable( $processCallback ) ) {
 576                                                 call_user_func_array( $processCallback, array( &$params, $args ) );
 577                                         }
 578
 579                                         if ( !Sanitizer::validateTag( $params, $t ) ) {
 580                                                 $badtag = true;
 581                                         }
 582
 583                                         $newparams = Sanitizer::fixTagAttributes( $params, $t );
 584                                         if ( !$badtag ) {
 585                                                 $rest = str_replace( '>', '&gt;', $rest );
 586                                                 $text .= "<$slash$t$newparams$brace$rest";
 587                                                 continue;
 588                                         }
 589                                 }
 590                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 591                         }
 592                 }
 593                 wfProfileOut( __METHOD__ );
 594                 return $text;
 595         }
 596
 597         /**
 598          * Remove '<!--', '-->', and everything between.
 599          * To avoid leaving blank lines, when a comment is both preceded
 600          * and followed by a newline (ignoring spaces), trim leading and
 601          * trailing spaces and one of the newlines.
 602          *
 603          * @private
 604          * @param string $text
 605          * @return string
 606          */
 607         static function removeHTMLcomments( $text ) {
 608                 wfProfileIn( __METHOD__ );
 609                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 610                         $end = strpos( $text, '-->', $start + 4 );
 611                         if ( $end === false ) {
 612                                 # Unterminated comment; bail out
 613                                 break;
 614                         }
 615
 616                         $end += 3;
 617
 618                         # Trim space and newline if the comment is both
 619                         # preceded and followed by a newline
 620                         $spaceStart = max( $start - 1, 0 );
 621                         $spaceLen = $end - $spaceStart;
 622                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 623                                 $spaceStart--;
 624                                 $spaceLen++;
 625                         }
 626                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 627                                 $spaceLen++;
 628                         }
 629                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 630                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 631                                 # Remove the comment, leading and trailing
 632                                 # spaces, and leave only one newline.
 633                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 634                         }
 635                         else {
 636                                 # Remove just the comment.
 637                                 $text = substr_replace( $text, '', $start, $end - $start );
 638                         }
 639                 }
 640                 wfProfileOut( __METHOD__ );
 641                 return $text;
 642         }
 643
 644         /**
 645          * Takes attribute names and values for a tag and the tag name and
 646          * validates that the tag is allowed to be present.
 647          * This DOES NOT validate the attributes, nor does it validate the
 648          * tags themselves. This method only handles the special circumstances
 649          * where we may want to allow a tag within content but ONLY when it has
 650          * specific attributes set.
 651          *
 652          * @param string $params
 653          * @param string $element
 654          * @return bool
 655          */
 656         static function validateTag( $params, $element ) {
 657                 $params = Sanitizer::decodeTagAttributes( $params );
 658
 659                 if ( $element == 'meta' || $element == 'link' ) {
 660                         if ( !isset( $params['itemprop'] ) ) {
 661                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 662                                 return false;
 663                         }
 664                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 665                                 // <meta> must have a content="" for the itemprop
 666                                 return false;
 667                         }
 668                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 669                                 // <link> must have an associated href=""
 670                                 return false;
 671                         }
 672                 }
 673
 674                 return true;
 675         }
 676
 677         /**
 678          * Take an array of attribute names and values and normalize or discard
 679          * illegal values for the given element type.
 680          *
 681          * - Discards attributes not on a whitelist for the given element
 682          * - Unsafe style attributes are discarded
 683          * - Invalid id attributes are re-encoded
 684          *
 685          * @param array $attribs
 686          * @param string $element
 687          * @return array
 688          *
 689          * @todo Check for legal values where the DTD limits things.
 690          * @todo Check for unique id attribute :P
 691          */
 692         static function validateTagAttributes( $attribs, $element ) {
 693                 return Sanitizer::validateAttributes( $attribs,
 694                         Sanitizer::attributeWhitelist( $element ) );
 695         }
 696
 697         /**
 698          * Take an array of attribute names and values and normalize or discard
 699          * illegal values for the given whitelist.
 700          *
 701          * - Discards attributes not the given whitelist
 702          * - Unsafe style attributes are discarded
 703          * - Invalid id attributes are re-encoded
 704          *
 705          * @param array $attribs
 706          * @param array $whitelist list of allowed attribute names
 707          * @return array
 708          *
 709          * @todo Check for legal values where the DTD limits things.
 710          * @todo Check for unique id attribute :P
 711          */
 712         static function validateAttributes( $attribs, $whitelist ) {
 713                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 714
 715                 $whitelist = array_flip( $whitelist );
 716                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 717
 718                 $out = array();
 719                 foreach ( $attribs as $attribute => $value ) {
 720                         #allow XML namespace declaration if RDFa is enabled
 721                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 722                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 723                                         $out[$attribute] = $value;
 724                                 }
 725
 726                                 continue;
 727                         }
 728
 729                         # Allow any attribute beginning with "data-"
 730                         if ( !preg_match( '/^data-/i', $attribute ) && !isset( $whitelist[$attribute] ) ) {
 731                                 continue;
 732                         }
 733
 734                         # Strip javascript "expression" from stylesheets.
 735                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 736                         if ( $attribute == 'style' ) {
 737                                 $value = Sanitizer::checkCss( $value );
 738                         }
 739
 740                         if ( $attribute === 'id' ) {
 741                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 742                         }
 743
 744                         # WAI-ARIA
 745                         # http://www.w3.org/TR/wai-aria/
 746                         # http://www.whatwg.org/html/elements.html#wai-aria
 747                         # For now we only support role="presentation" until we work out what roles should be
 748                         # usable by content and we ensure that our code explicitly rejects patterns that
 749                         # violate HTML5's ARIA restrictions.
 750                         if ( $attribute === 'role' && $value !== 'presentation' ) {
 751                                 continue;
 752                         }
 753
 754                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 755                         // Check them for sanity.
 756                         if ( $attribute === 'rel' || $attribute === 'rev'
 757                                 # RDFa
 758                                 || $attribute === 'about' || $attribute === 'property'
 759                                 || $attribute === 'resource' || $attribute === 'datatype'
 760                                 || $attribute === 'typeof'
 761                                 # HTML5 microdata
 762                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 763                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 764                                 || $attribute === 'itemtype'
 765                         ) {
 766                                 //Paranoia. Allow "simple" values but suppress javascript
 767                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 768                                         continue;
 769                                 }
 770                         }
 771
 772                         # NOTE: even though elements using href/src are not allowed directly, supply
 773                         #       validation code that can be used by tag hook handlers, etc
 774                         if ( $attribute === 'href' || $attribute === 'src' ) {
 775                                 if ( !preg_match( $hrefExp, $value ) ) {
 776                                         continue; //drop any href or src attributes not using an allowed protocol.
 777                                         // NOTE: this also drops all relative URLs
 778                                 }
 779                         }
 780
 781                         // If this attribute was previously set, override it.
 782                         // Output should only have one attribute of each name.
 783                         $out[$attribute] = $value;
 784                 }
 785
 786                 if ( $wgAllowMicrodataAttributes ) {
 787                         # itemtype, itemid, itemref don't make sense without itemscope
 788                         if ( !array_key_exists( 'itemscope', $out ) ) {
 789                                 unset( $out['itemtype'] );
 790                                 unset( $out['itemid'] );
 791                                 unset( $out['itemref'] );
 792                         }
 793                         # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 794                 }
 795                 return $out;
 796         }
 797
 798         /**
 799          * Merge two sets of HTML attributes.  Conflicting items in the second set
 800          * will override those in the first, except for 'class' attributes which
 801          * will be combined (if they're both strings).
 802          *
 803          * @todo implement merging for other attributes such as style
 804          * @param array $a
 805          * @param array $b
 806          * @return array
 807          */
 808         static function mergeAttributes( $a, $b ) {
 809                 $out = array_merge( $a, $b );
 810                 if ( isset( $a['class'] ) && isset( $b['class'] )
 811                         && is_string( $a['class'] ) && is_string( $b['class'] )
 812                         && $a['class'] !== $b['class']
 813                 ) {
 814                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 815                                 -1, PREG_SPLIT_NO_EMPTY );
 816                         $out['class'] = implode( ' ', array_unique( $classes ) );
 817                 }
 818                 return $out;
 819         }
 820
 821         /**
 822          * Pick apart some CSS and check it for forbidden or unsafe structures.
 823          * Returns a sanitized string. This sanitized string will have
 824          * character references and escape sequences decoded and comments
 825          * stripped (unless it is itself one valid comment, in which case the value
 826          * will be passed through). If the input is just too evil, only a comment
 827          * complaining about evilness will be returned.
 828          *
 829          * Currently URL references, 'expression', 'tps' are forbidden.
 830          *
 831          * NOTE: Despite the fact that character references are decoded, the
 832          * returned string may contain character references given certain
 833          * clever input strings. These character references must
 834          * be escaped before the return value is embedded in HTML.
 835          *
 836          * @param string $value
 837          * @return string
 838          */
 839         static function checkCss( $value ) {
 840                 // Decode character references like &#123;
 841                 $value = Sanitizer::decodeCharReferences( $value );
 842
 843                 // Decode escape sequences and line continuation
 844                 // See the grammar in the CSS 2 spec, appendix D.
 845                 // This has to be done AFTER decoding character references.
 846                 // This means it isn't possible for this function to return
 847                 // unsanitized escape sequences. It is possible to manufacture
 848                 // input that contains character references that decode to
 849                 // escape sequences that decode to character references, but
 850                 // it's OK for the return value to contain character references
 851                 // because the caller is supposed to escape those anyway.
 852                 static $decodeRegex;
 853                 if ( !$decodeRegex ) {
 854                         $space = '[\\x20\\t\\r\\n\\f]';
 855                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 856                         $backslash = '\\\\';
 857                         $decodeRegex = "/ $backslash
 858                                 (?:
 859                                         ($nl) |  # 1. Line continuation
 860                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 861                                         (.) | # 3. backslash cancelling special meaning
 862                                         () | # 4. backslash at end of string
 863                                 )/xu";
 864                 }
 865                 $value = preg_replace_callback( $decodeRegex,
 866                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 867
 868                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 869                 $value = preg_replace_callback(
 870                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (bug 58088)
 871                         function ( $matches ) {
 872                                 $cp = utf8ToCodepoint( $matches[0] );
 873                                 if ( $cp === false ) {
 874                                         return '';
 875                                 }
 876                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 877                         },
 878                         $value
 879                 );
 880
 881                 // Convert more characters IE6 might treat as ascii
 882                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 883                 $value = str_replace(
 884                         array( 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ),
 885                         array( 'r', 'n', 'n', 'l', 'i', '(', '(' ),
 886                         $value
 887                 );
 888
 889                 // Let the value through if it's nothing but a single comment, to
 890                 // allow other functions which may reject it to pass some error
 891                 // message through.
 892                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 893                         // Remove any comments; IE gets token splitting wrong
 894                         // This must be done AFTER decoding character references and
 895                         // escape sequences, because those steps can introduce comments
 896                         // This step cannot introduce character references or escape
 897                         // sequences, because it replaces comments with spaces rather
 898                         // than removing them completely.
 899                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 900
 901                         // Remove anything after a comment-start token, to guard against
 902                         // incorrect client implementations.
 903                         $commentPos = strpos( $value, '/*' );
 904                         if ( $commentPos !== false ) {
 905                                 $value = substr( $value, 0, $commentPos );
 906                         }
 907                 }
 908
 909                 // S followed by repeat, iteration, or prolonged sound marks,
 910                 // which IE will treat as "ss"
 911                 $value = preg_replace(
 912                         '/s(?:
 913                                 \xE3\x80\xB1 | # U+3031
 914                                 \xE3\x82\x9D | # U+309D
 915                                 \xE3\x83\xBC | # U+30FC
 916                                 \xE3\x83\xBD | # U+30FD
 917                                 \xEF\xB9\xBC | # U+FE7C
 918                                 \xEF\xB9\xBD | # U+FE7D
 919                                 \xEF\xBD\xB0   # U+FF70
 920                         )/ix',
 921                         'ss',
 922                         $value
 923                 );
 924
 925                 // Reject problematic keywords and control characters
 926                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ) {
 927                         return '/* invalid control char */';
 928                 } elseif ( preg_match(
 929                         '! expression
 930                                 | filter\s*:
 931                                 | accelerator\s*:
 932                                 | -o-link\s*:
 933                                 | -o-link-source\s*:
 934                                 | -o-replace\s*:
 935                                 | url\s*\(
 936                                 | image\s*\(
 937                                 | image-set\s*\(
 938                         !ix', $value ) ) {
 939                         return '/* insecure input */';
 940                 }
 941                 return $value;
 942         }
 943
 944         /**
 945          * @param array $matches
 946          * @return string
 947          */
 948         static function cssDecodeCallback( $matches ) {
 949                 if ( $matches[1] !== '' ) {
 950                         // Line continuation
 951                         return '';
 952                 } elseif ( $matches[2] !== '' ) {
 953                         $char = codepointToUtf8( hexdec( $matches[2] ) );
 954                 } elseif ( $matches[3] !== '' ) {
 955                         $char = $matches[3];
 956                 } else {
 957                         $char = '\\';
 958                 }
 959                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
 960                         // These characters need to be escaped in strings
 961                         // Clean up the escape sequence to avoid parsing errors by clients
 962                         return '\\' . dechex( ord( $char ) ) . ' ';
 963                 } else {
 964                         // Decode unnecessary escape
 965                         return $char;
 966                 }
 967         }
 968
 969         /**
 970          * Take a tag soup fragment listing an HTML element's attributes
 971          * and normalize it to well-formed XML, discarding unwanted attributes.
 972          * Output is safe for further wikitext processing, with escaping of
 973          * values that could trigger problems.
 974          *
 975          * - Normalizes attribute names to lowercase
 976          * - Discards attributes not on a whitelist for the given element
 977          * - Turns broken or invalid entities into plaintext
 978          * - Double-quotes all attribute values
 979          * - Attributes without values are given the name as attribute
 980          * - Double attributes are discarded
 981          * - Unsafe style attributes are discarded
 982          * - Prepends space if there are attributes.
 983          *
 984          * @param string $text
 985          * @param string $element
 986          * @return string
 987          */
 988         static function fixTagAttributes( $text, $element ) {
 989                 if ( trim( $text ) == '' ) {
 990                         return '';
 991                 }
 992
 993                 $decoded = Sanitizer::decodeTagAttributes( $text );
 994                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
 995
 996                 return Sanitizer::safeEncodeTagAttributes( $stripped );
 997         }
 998
 999         /**
1000          * Encode an attribute value for HTML output.
1001          * @param string $text
1002          * @return string HTML-encoded text fragment
1003          */
1004         static function encodeAttribute( $text ) {
1005                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1006
1007                 // Whitespace is normalized during attribute decoding,
1008                 // so if we've been passed non-spaces we must encode them
1009                 // ahead of time or they won't be preserved.
1010                 $encValue = strtr( $encValue, array(
1011                         "\n" => '&#10;',
1012                         "\r" => '&#13;',
1013                         "\t" => '&#9;',
1014                 ) );
1015
1016                 return $encValue;
1017         }
1018
1019         /**
1020          * Encode an attribute value for HTML tags, with extra armoring
1021          * against further wiki processing.
1022          * @param string $text
1023          * @return string HTML-encoded text fragment
1024          */
1025         static function safeEncodeAttribute( $text ) {
1026                 $encValue = Sanitizer::encodeAttribute( $text );
1027
1028                 # Templates and links may be expanded in later parsing,
1029                 # creating invalid or dangerous output. Suppress this.
1030                 $encValue = strtr( $encValue, array(
1031                         '<'    => '&lt;',   // This should never happen,
1032                         '>'    => '&gt;',   // we've received invalid input
1033                         '"'    => '&quot;', // which should have been escaped.
1034                         '{'    => '&#123;',
1035                         '['    => '&#91;',
1036                         "''"   => '&#39;&#39;',
1037                         'ISBN' => '&#73;SBN',
1038                         'RFC'  => '&#82;FC',
1039                         'PMID' => '&#80;MID',
1040                         '|'    => '&#124;',
1041                         '__'   => '&#95;_',
1042                 ) );
1043
1044                 # Stupid hack
1045                 $encValue = preg_replace_callback(
1046                         '/((?i)' . wfUrlProtocols() . ')/',
1047                         array( 'Sanitizer', 'armorLinksCallback' ),
1048                         $encValue );
1049                 return $encValue;
1050         }
1051
1052         /**
1053          * Given a value, escape it so that it can be used in an id attribute and
1054          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1055          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1056          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1057          * escaped with lots of dots.
1058          *
1059          * To ensure we don't have to bother escaping anything, we also strip ', ",
1060          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1061          * We also strip # because it upsets IE, and % because it could be
1062          * ambiguous if it's part of something that looks like a percent escape
1063          * (which don't work reliably in fragments cross-browser).
1064          *
1065          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
1066          *   in the id and name attributes
1067          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1068          *   the id attribute
1069          * @see http://www.whatwg.org/html/elements.html#the-id-attribute
1070          *   HTML5 definition of id attribute
1071          *
1072          * @param string $id id to escape
1073          * @param $options Mixed: string or array of strings (default is array()):
1074          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1075          *       so don't pay attention if the first character isn't valid at the
1076          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1077          *       false.
1078          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1079          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1080          *       anchors and links won't break.
1081          * @return string
1082          */
1083         static function escapeId( $id, $options = array() ) {
1084                 global $wgExperimentalHtmlIds;
1085                 $options = (array)$options;
1086
1087                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1088                         $id = Sanitizer::decodeCharReferences( $id );
1089                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1090                         $id = trim( $id, '_' );
1091                         if ( $id === '' ) {
1092                                 # Must have been all whitespace to start with.
1093                                 return '_';
1094                         } else {
1095                                 return $id;
1096                         }
1097                 }
1098
1099                 # HTML4-style escaping
1100                 static $replace = array(
1101                         '%3A' => ':',
1102                         '%' => '.'
1103                 );
1104
1105                 $id = urlencode( Sanitizer::decodeCharReferences( strtr( $id, ' ', '_' ) ) );
1106                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1107
1108                 if ( !preg_match( '/^[a-zA-Z]/', $id )
1109                 && !in_array( 'noninitial', $options ) ) {
1110                         // Initial character must be a letter!
1111                         $id = "x$id";
1112                 }
1113                 return $id;
1114         }
1115
1116         /**
1117          * Given a value, escape it so that it can be used as a CSS class and
1118          * return it.
1119          *
1120          * @todo For extra validity, input should be validated UTF-8.
1121          *
1122          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1123          *
1124          * @param string $class
1125          * @return string
1126          */
1127         static function escapeClass( $class ) {
1128                 // Convert ugly stuff to underscores and kill underscores in ugly places
1129                 return rtrim( preg_replace(
1130                         array( '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ),
1131                         '_',
1132                         $class ), '_' );
1133         }
1134
1135         /**
1136          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1137          * This allows (generally harmless) entities like &#160; to survive.
1138          *
1139          * @param string $html HTML to escape
1140          * @return string: escaped input
1141          */
1142         static function escapeHtmlAllowEntities( $html ) {
1143                 $html = Sanitizer::decodeCharReferences( $html );
1144                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1145                 # hurt.
1146                 $html = htmlspecialchars( $html, ENT_QUOTES );
1147                 return $html;
1148         }
1149
1150         /**
1151          * Regex replace callback for armoring links against further processing.
1152          * @param array $matches
1153          * @return string
1154          */
1155         private static function armorLinksCallback( $matches ) {
1156                 return str_replace( ':', '&#58;', $matches[1] );
1157         }
1158
1159         /**
1160          * Return an associative array of attribute names and values from
1161          * a partial tag string. Attribute names are forces to lowercase,
1162          * character references are decoded to UTF-8 text.
1163          *
1164          * @param string $text
1165          * @return array
1166          */
1167         public static function decodeTagAttributes( $text ) {
1168                 if ( trim( $text ) == '' ) {
1169                         return array();
1170                 }
1171
1172                 $attribs = array();
1173                 $pairs = array();
1174                 if ( !preg_match_all(
1175                         self::getAttribsRegex(),
1176                         $text,
1177                         $pairs,
1178                         PREG_SET_ORDER ) ) {
1179                         return $attribs;
1180                 }
1181
1182                 foreach ( $pairs as $set ) {
1183                         $attribute = strtolower( $set[1] );
1184                         $value = Sanitizer::getTagAttributeCallback( $set );
1185
1186                         // Normalize whitespace
1187                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1188                         $value = trim( $value );
1189
1190                         // Decode character references
1191                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1192                 }
1193                 return $attribs;
1194         }
1195
1196         /**
1197          * Build a partial tag string from an associative array of attribute
1198          * names and values as returned by decodeTagAttributes.
1199          *
1200          * @param array $assoc_array
1201          * @return string
1202          */
1203         public static function safeEncodeTagAttributes( $assoc_array ) {
1204                 $attribs = array();
1205                 foreach ( $assoc_array as $attribute => $value ) {
1206                         $encAttribute = htmlspecialchars( $attribute );
1207                         $encValue = Sanitizer::safeEncodeAttribute( $value );
1208
1209                         $attribs[] = "$encAttribute=\"$encValue\"";
1210                 }
1211                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1212         }
1213
1214         /**
1215          * Pick the appropriate attribute value from a match set from the
1216          * attribs regex matches.
1217          *
1218          * @param array $set
1219          * @throws MWException when tag conditions are not met.
1220          * @return string
1221          */
1222         private static function getTagAttributeCallback( $set ) {
1223                 if ( isset( $set[6] ) ) {
1224                         # Illegal #XXXXXX color with no quotes.
1225                         return $set[6];
1226                 } elseif ( isset( $set[5] ) ) {
1227                         # No quotes.
1228                         return $set[5];
1229                 } elseif ( isset( $set[4] ) ) {
1230                         # Single-quoted
1231                         return $set[4];
1232                 } elseif ( isset( $set[3] ) ) {
1233                         # Double-quoted
1234                         return $set[3];
1235                 } elseif ( !isset( $set[2] ) ) {
1236                         # In XHTML, attributes must have a value.
1237                         # For 'reduced' form, return explicitly the attribute name here.
1238                         return $set[1];
1239                 } else {
1240                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1241                 }
1242         }
1243
1244         /**
1245          * Normalize whitespace and character references in an XML source-
1246          * encoded text for an attribute value.
1247          *
1248          * See http://www.w3.org/TR/REC-xml/#AVNormalize for background,
1249          * but note that we're not returning the value, but are returning
1250          * XML source fragments that will be slapped into output.
1251          *
1252          * @param string $text
1253          * @return string
1254          * @todo Remove, unused?
1255          */
1256         private static function normalizeAttributeValue( $text ) {
1257                 return str_replace( '"', '&quot;',
1258                         self::normalizeWhitespace(
1259                                 Sanitizer::normalizeCharReferences( $text ) ) );
1260         }
1261
1262         /**
1263          * @param string $text
1264          * @return string
1265          */
1266         private static function normalizeWhitespace( $text ) {
1267                 return preg_replace(
1268                         '/\r\n|[\x20\x0d\x0a\x09]/',
1269                         ' ',
1270                         $text );
1271         }
1272
1273         /**
1274          * Normalizes whitespace in a section name, such as might be returned
1275          * by Parser::stripSectionName(), for use in the id's that are used for
1276          * section links.
1277          *
1278          * @param string $section
1279          * @return string
1280          */
1281         static function normalizeSectionNameWhitespace( $section ) {
1282                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1283         }
1284
1285         /**
1286          * Ensure that any entities and character references are legal
1287          * for XML and XHTML specifically. Any stray bits will be
1288          * &amp;-escaped to result in a valid text fragment.
1289          *
1290          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1291          *   numericized (this way we're well-formed even without a DTD)
1292          * b. any numeric char refs must be legal chars, not invalid or forbidden
1293          * c. use lower cased "&#x", not "&#X"
1294          * d. fix or reject non-valid attributes
1295          *
1296          * @param string $text
1297          * @return string
1298          * @private
1299          */
1300         static function normalizeCharReferences( $text ) {
1301                 return preg_replace_callback(
1302                         self::CHAR_REFS_REGEX,
1303                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1304                         $text );
1305         }
1306         /**
1307          * @param string $matches
1308          * @return string
1309          */
1310         static function normalizeCharReferencesCallback( $matches ) {
1311                 $ret = null;
1312                 if ( $matches[1] != '' ) {
1313                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1314                 } elseif ( $matches[2] != '' ) {
1315                         $ret = Sanitizer::decCharReference( $matches[2] );
1316                 } elseif ( $matches[3] != '' ) {
1317                         $ret = Sanitizer::hexCharReference( $matches[3] );
1318                 }
1319                 if ( is_null( $ret ) ) {
1320                         return htmlspecialchars( $matches[0] );
1321                 } else {
1322                         return $ret;
1323                 }
1324         }
1325
1326         /**
1327          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1328          * return the equivalent numeric entity reference (except for the core &lt;
1329          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1330          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1331          * pseudo-entity source (eg &amp;foo;)
1332          *
1333          * @param string $name
1334          * @return string
1335          */
1336         static function normalizeEntity( $name ) {
1337                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1338                         return '&' . self::$htmlEntityAliases[$name] . ';';
1339                 } elseif ( in_array( $name,
1340                 array( 'lt', 'gt', 'amp', 'quot' ) ) ) {
1341                         return "&$name;";
1342                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1343                         return '&#' . self::$htmlEntities[$name] . ';';
1344                 } else {
1345                         return "&amp;$name;";
1346                 }
1347         }
1348
1349         /**
1350          * @param int $codepoint
1351          * @return null|string
1352          */
1353         static function decCharReference( $codepoint ) {
1354                 $point = intval( $codepoint );
1355                 if ( Sanitizer::validateCodepoint( $point ) ) {
1356                         return sprintf( '&#%d;', $point );
1357                 } else {
1358                         return null;
1359                 }
1360         }
1361
1362         /**
1363          * @param int $codepoint
1364          * @return null|string
1365          */
1366         static function hexCharReference( $codepoint ) {
1367                 $point = hexdec( $codepoint );
1368                 if ( Sanitizer::validateCodepoint( $point ) ) {
1369                         return sprintf( '&#x%x;', $point );
1370                 } else {
1371                         return null;
1372                 }
1373         }
1374
1375         /**
1376          * Returns true if a given Unicode codepoint is a valid character in XML.
1377          * @param int $codepoint
1378          * @return bool
1379          */
1380         private static function validateCodepoint( $codepoint ) {
1381                 return $codepoint == 0x09
1382                         || $codepoint == 0x0a
1383                         || $codepoint == 0x0d
1384                         || ( $codepoint >= 0x20 && $codepoint <= 0xd7ff )
1385                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1386                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1387         }
1388
1389         /**
1390          * Decode any character references, numeric or named entities,
1391          * in the text and return a UTF-8 string.
1392          *
1393          * @param string $text
1394          * @return string
1395          */
1396         public static function decodeCharReferences( $text ) {
1397                 return preg_replace_callback(
1398                         self::CHAR_REFS_REGEX,
1399                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1400                         $text );
1401         }
1402
1403         /**
1404          * Decode any character references, numeric or named entities,
1405          * in the next and normalize the resulting string. (bug 14952)
1406          *
1407          * This is useful for page titles, not for text to be displayed,
1408          * MediaWiki allows HTML entities to escape normalization as a feature.
1409          *
1410          * @param string $text Already normalized, containing entities
1411          * @return string Still normalized, without entities
1412          */
1413         public static function decodeCharReferencesAndNormalize( $text ) {
1414                 global $wgContLang;
1415                 $text = preg_replace_callback(
1416                         self::CHAR_REFS_REGEX,
1417                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1418                         $text, /* limit */ -1, $count );
1419
1420                 if ( $count ) {
1421                         return $wgContLang->normalize( $text );
1422                 } else {
1423                         return $text;
1424                 }
1425         }
1426
1427         /**
1428          * @param string $matches
1429          * @return string
1430          */
1431         static function decodeCharReferencesCallback( $matches ) {
1432                 if ( $matches[1] != '' ) {
1433                         return Sanitizer::decodeEntity( $matches[1] );
1434                 } elseif ( $matches[2] != '' ) {
1435                         return Sanitizer::decodeChar( intval( $matches[2] ) );
1436                 } elseif ( $matches[3] != '' ) {
1437                         return Sanitizer::decodeChar( hexdec( $matches[3] ) );
1438                 }
1439                 # Last case should be an ampersand by itself
1440                 return $matches[0];
1441         }
1442
1443         /**
1444          * Return UTF-8 string for a codepoint if that is a valid
1445          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1446          * @param int $codepoint
1447          * @return string
1448          * @private
1449          */
1450         static function decodeChar( $codepoint ) {
1451                 if ( Sanitizer::validateCodepoint( $codepoint ) ) {
1452                         return codepointToUtf8( $codepoint );
1453                 } else {
1454                         return UTF8_REPLACEMENT;
1455                 }
1456         }
1457
1458         /**
1459          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1460          * return the UTF-8 encoding of that character. Otherwise, returns
1461          * pseudo-entity source (eg "&foo;")
1462          *
1463          * @param string $name
1464          * @return string
1465          */
1466         static function decodeEntity( $name ) {
1467                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1468                         $name = self::$htmlEntityAliases[$name];
1469                 }
1470                 if ( isset( self::$htmlEntities[$name] ) ) {
1471                         return codepointToUtf8( self::$htmlEntities[$name] );
1472                 } else {
1473                         return "&$name;";
1474                 }
1475         }
1476
1477         /**
1478          * Fetch the whitelist of acceptable attributes for a given element name.
1479          *
1480          * @param string $element
1481          * @return array
1482          */
1483         static function attributeWhitelist( $element ) {
1484                 $list = Sanitizer::setupAttributeWhitelist();
1485                 return isset( $list[$element] )
1486                         ? $list[$element]
1487                         : array();
1488         }
1489
1490         /**
1491          * Foreach array key (an allowed HTML element), return an array
1492          * of allowed attributes
1493          * @return array
1494          */
1495         static function setupAttributeWhitelist() {
1496                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
1497
1498                 static $whitelist, $staticInitialised;
1499                 $globalContext = implode( '-', compact( 'wgAllowRdfaAttributes', 'wgAllowMicrodataAttributes' ) );
1500
1501                 if ( isset( $whitelist ) && $staticInitialised == $globalContext ) {
1502                         return $whitelist;
1503                 }
1504
1505                 $common = array(
1506                         # HTML
1507                         'id',
1508                         'class',
1509                         'style',
1510                         'lang',
1511                         'dir',
1512                         'title',
1513
1514                         # WAI-ARIA
1515                         'role',
1516                 );
1517
1518                 if ( $wgAllowRdfaAttributes ) {
1519                         # RDFa attributes as specified in section 9 of
1520                         # http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1521                         $common = array_merge( $common, array(
1522                                 'about', 'property', 'resource', 'datatype', 'typeof',
1523                         ) );
1524                 }
1525
1526                 if ( $wgAllowMicrodataAttributes ) {
1527                         # add HTML5 microdata tags as specified by
1528                         # http://www.whatwg.org/html/microdata.html#the-microdata-model
1529                         $common = array_merge( $common, array(
1530                                 'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1531                         ) );
1532                 }
1533
1534                 $block = array_merge( $common, array( 'align' ) );
1535                 $tablealign = array( 'align', 'valign' );
1536                 $tablecell = array(
1537                         'abbr',
1538                         'axis',
1539                         'headers',
1540                         'scope',
1541                         'rowspan',
1542                         'colspan',
1543                         'nowrap', # deprecated
1544                         'width', # deprecated
1545                         'height', # deprecated
1546                         'bgcolor', # deprecated
1547                 );
1548
1549                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1550                 # See: http://www.w3.org/TR/html4/
1551                 $whitelist = array(
1552                         # 7.5.4
1553                         'div'        => $block,
1554                         'center'     => $common, # deprecated
1555                         'span'       => $common,
1556
1557                         # 7.5.5
1558                         'h1'         => $block,
1559                         'h2'         => $block,
1560                         'h3'         => $block,
1561                         'h4'         => $block,
1562                         'h5'         => $block,
1563                         'h6'         => $block,
1564
1565                         # 7.5.6
1566                         # address
1567
1568                         # 8.2.4
1569                         'bdo'        => $common,
1570
1571                         # 9.2.1
1572                         'em'         => $common,
1573                         'strong'     => $common,
1574                         'cite'       => $common,
1575                         'dfn'        => $common,
1576                         'code'       => $common,
1577                         'samp'       => $common,
1578                         'kbd'        => $common,
1579                         'var'        => $common,
1580                         'abbr'       => $common,
1581                         # acronym
1582
1583                         # 9.2.2
1584                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1585                         'q'          => array_merge( $common, array( 'cite' ) ),
1586
1587                         # 9.2.3
1588                         'sub'        => $common,
1589                         'sup'        => $common,
1590
1591                         # 9.3.1
1592                         'p'          => $block,
1593
1594                         # 9.3.2
1595                         'br'         => array_merge( $common, array( 'clear' ) ),
1596
1597                         # http://www.whatwg.org/html/text-level-semantics.html#the-wbr-element
1598                         'wbr'        => $common,
1599
1600                         # 9.3.4
1601                         'pre'        => array_merge( $common, array( 'width' ) ),
1602
1603                         # 9.4
1604                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1605                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1606
1607                         # 10.2
1608                         'ul'         => array_merge( $common, array( 'type' ) ),
1609                         'ol'         => array_merge( $common, array( 'type', 'start' ) ),
1610                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1611
1612                         # 10.3
1613                         'dl'         => $common,
1614                         'dd'         => $common,
1615                         'dt'         => $common,
1616
1617                         # 11.2.1
1618                         'table'      => array_merge( $common,
1619                                                                 array( 'summary', 'width', 'border', 'frame',
1620                                                                                 'rules', 'cellspacing', 'cellpadding',
1621                                                                                 'align', 'bgcolor',
1622                                                                 ) ),
1623
1624                         # 11.2.2
1625                         'caption'    => $block,
1626
1627                         # 11.2.3
1628                         'thead'      => $common,
1629                         'tfoot'      => $common,
1630                         'tbody'      => $common,
1631
1632                         # 11.2.4
1633                         'colgroup'   => array_merge( $common, array( 'span' ) ),
1634                         'col'        => array_merge( $common, array( 'span' ) ),
1635
1636                         # 11.2.5
1637                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1638
1639                         # 11.2.6
1640                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1641                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1642
1643                         # 12.2
1644                         # NOTE: <a> is not allowed directly, but the attrib
1645                         # whitelist is used from the Parser object
1646                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1647
1648                         # 13.2
1649                         # Not usually allowed, but may be used for extension-style hooks
1650                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1651                         # true
1652                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1653
1654                         # 15.2.1
1655                         'tt'         => $common,
1656                         'b'          => $common,
1657                         'i'          => $common,
1658                         'big'        => $common,
1659                         'small'      => $common,
1660                         'strike'     => $common,
1661                         's'          => $common,
1662                         'u'          => $common,
1663
1664                         # 15.2.2
1665                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1666                         # basefont
1667
1668                         # 15.3
1669                         'hr'         => array_merge( $common, array( 'width' ) ),
1670
1671                         # HTML Ruby annotation text module, simple ruby only.
1672                         # http://www.whatwg.org/html/text-level-semantics.html#the-ruby-element
1673                         'ruby'       => $common,
1674                         # rbc
1675                         # rtc
1676                         'rb'         => $common,
1677                         'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),
1678                         'rp'         => $common,
1679
1680                         # MathML root element, where used for extensions
1681                         # 'title' may not be 100% valid here; it's XHTML
1682                         # http://www.w3.org/TR/REC-MathML/
1683                         'math'       => array( 'class', 'style', 'id', 'title' ),
1684
1685                         # HTML 5 section 4.6
1686                         'bdi' => $common,
1687
1688                         # HTML5 elements, defined by:
1689                         # http://www.whatwg.org/html/
1690                         'data' => array_merge( $common, array( 'value' ) ),
1691                         'time' => array_merge( $common, array( 'datetime' ) ),
1692                         'mark' => $common,
1693
1694                         // meta and link are only permitted by removeHTMLtags when Microdata
1695                         // is enabled so we don't bother adding a conditional to hide these
1696                         // Also meta and link are only valid in WikiText as Microdata elements
1697                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1698                         // So we don't bother including $common attributes that have no purpose.
1699                         'meta' => array( 'itemprop', 'content' ),
1700                         'link' => array( 'itemprop', 'href' ),
1701                 );
1702
1703                 $staticInitialised = $globalContext;
1704
1705                 return $whitelist;
1706         }
1707
1708         /**
1709          * Take a fragment of (potentially invalid) HTML and return
1710          * a version with any tags removed, encoded as plain text.
1711          *
1712          * Warning: this return value must be further escaped for literal
1713          * inclusion in HTML output as of 1.10!
1714          *
1715          * @param string $text HTML fragment
1716          * @return string
1717          */
1718         static function stripAllTags( $text ) {
1719                 # Actual <tags>
1720                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1721
1722                 # Normalize &entities and whitespace
1723                 $text = self::decodeCharReferences( $text );
1724                 $text = self::normalizeWhitespace( $text );
1725
1726                 return $text;
1727         }
1728
1729         /**
1730          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1731          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1732          * PHP 5.1 doesn't.
1733          *
1734          * Use for passing XHTML fragments to PHP's XML parsing functions
1735          *
1736          * @return string
1737          */
1738         static function hackDocType() {
1739                 $out = "<!DOCTYPE html [\n";
1740                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
1741                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1742                 }
1743                 $out .= "]>\n";
1744                 return $out;
1745         }
1746
1747         /**
1748          * @param string $url
1749          * @return mixed|string
1750          */
1751         static function cleanUrl( $url ) {
1752                 # Normalize any HTML entities in input. They will be
1753                 # re-escaped by makeExternalLink().
1754                 $url = Sanitizer::decodeCharReferences( $url );
1755
1756                 # Escape any control characters introduced by the above step
1757                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1758                         array( __CLASS__, 'cleanUrlCallback' ), $url );
1759
1760                 # Validate hostname portion
1761                 $matches = array();
1762                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1763                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1764
1765                         // Characters that will be ignored in IDNs.
1766                         // http://tools.ietf.org/html/3454#section-3.1
1767                         // Strip them before further processing so blacklists and such work.
1768                         $strip = "/
1769                                 \\s|          # general whitespace
1770                                 \xc2\xad|     # 00ad SOFT HYPHEN
1771                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1772                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1773                                 \xe2\x81\xa0| # 2060 WORD JOINER
1774                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1775                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1776                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1777                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1778                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1779                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1780                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1781                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
1782                                 /xuD";
1783
1784                         $host = preg_replace( $strip, '', $host );
1785
1786                         // @todo FIXME: Validate hostnames here
1787
1788                         return $protocol . $host . $rest;
1789                 } else {
1790                         return $url;
1791                 }
1792         }
1793
1794         /**
1795          * @param array $matches
1796          * @return string
1797          */
1798         static function cleanUrlCallback( $matches ) {
1799                 return urlencode( $matches[0] );
1800         }
1801
1802         /**
1803          * Does a string look like an e-mail address?
1804          *
1805          * This validates an email address using an HTML5 specification found at:
1806          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
1807          * Which as of 2011-01-24 says:
1808          *
1809          *   A valid e-mail address is a string that matches the ABNF production
1810          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1811          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1812          *   3.5.
1813          *
1814          * This function is an implementation of the specification as requested in
1815          * bug 22449.
1816          *
1817          * Client-side forms will use the same standard validation rules via JS or
1818          * HTML 5 validation; additional restrictions can be enforced server-side
1819          * by extensions via the 'isValidEmailAddr' hook.
1820          *
1821          * Note that this validation doesn't 100% match RFC 2822, but is believed
1822          * to be liberal enough for wide use. Some invalid addresses will still
1823          * pass validation here.
1824          *
1825          * @since 1.18
1826          *
1827          * @param string $addr E-mail address
1828          * @return bool
1829          */
1830         public static function validateEmail( $addr ) {
1831                 $result = null;
1832                 if ( !wfRunHooks( 'isValidEmailAddr', array( $addr, &$result ) ) ) {
1833                         return $result;
1834                 }
1835
1836                 // Please note strings below are enclosed in brackets [], this make the
1837                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1838                 // See bug 26948
1839                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
1840                 $rfc1034_ldh_str = "a-z0-9\\-";
1841
1842                 $HTML5_email_regexp = "/
1843                 ^                      # start of string
1844                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1845                 @                      # 'apostrophe'
1846                 [$rfc1034_ldh_str]+       # First domain part
1847                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1848                 $                      # End of string
1849                 /ix"; // case Insensitive, eXtended
1850
1851                 return (bool)preg_match( $HTML5_email_regexp, $addr );
1852         }
1853 }