includes/Sanitizer.php

   1 <?php
   2 /**
   3  * HTML sanitizer for %MediaWiki.
   4  *
   5  * Copyright © 2002-2005 Brion Vibber <brion@pobox.com> et al
   6  * https://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Parser
  25  */
  26
  27 /**
  28  * HTML sanitizer for MediaWiki
  29  * @ingroup Parser
  30  */
  31 class Sanitizer {
  32         /**
  33          * Regular expression to match various types of character references in
  34          * Sanitizer::normalizeCharReferences and Sanitizer::decodeCharReferences
  35          */
  36         const CHAR_REFS_REGEX =
  37                 '/&([A-Za-z0-9\x80-\xff]+);
  38                  |&\#([0-9]+);
  39                  |&\#[xX]([0-9A-Fa-f]+);
  40                  |(&)/x';
  41
  42         /**
  43          * Acceptable tag name charset from HTML5 parsing spec
  44          * http://www.w3.org/TR/html5/syntax.html#tag-open-state
  45          */
  46         const ELEMENT_BITS_REGEX = '!^(/?)([A-Za-z][^\t\n\v />\0]*+)([^>]*?)(/?>)([^<]*)$!';
  47
  48         /**
  49          * Blacklist for evil uris like javascript:
  50          * WARNING: DO NOT use this in any place that actually requires blacklisting
  51          * for security reasons. There are NUMEROUS[1] ways to bypass blacklisting, the
  52          * only way to be secure from javascript: uri based xss vectors is to whitelist
  53          * things that you know are safe and deny everything else.
  54          * [1]: http://ha.ckers.org/xss.html
  55          */
  56         const EVIL_URI_PATTERN = '!(^|\s|\*/\s*)(javascript|vbscript)([^\w]|$)!i';
  57         const XMLNS_ATTRIBUTE_PATTERN = "/^xmlns:[:A-Z_a-z-.0-9]+$/";
  58
  59         /**
  60          * List of all named character entities defined in HTML 4.01
  61          * http://www.w3.org/TR/html4/sgml/entities.html
  62          * As well as &apos; which is only defined starting in XHTML1.
  63          */
  64         private static $htmlEntities = [
  65                 'Aacute'   => 193,
  66                 'aacute'   => 225,
  67                 'Acirc'    => 194,
  68                 'acirc'    => 226,
  69                 'acute'    => 180,
  70                 'AElig'    => 198,
  71                 'aelig'    => 230,
  72                 'Agrave'   => 192,
  73                 'agrave'   => 224,
  74                 'alefsym'  => 8501,
  75                 'Alpha'    => 913,
  76                 'alpha'    => 945,
  77                 'amp'      => 38,
  78                 'and'      => 8743,
  79                 'ang'      => 8736,
  80                 'apos'     => 39, // New in XHTML & HTML 5; avoid in output for compatibility with IE.
  81                 'Aring'    => 197,
  82                 'aring'    => 229,
  83                 'asymp'    => 8776,
  84                 'Atilde'   => 195,
  85                 'atilde'   => 227,
  86                 'Auml'     => 196,
  87                 'auml'     => 228,
  88                 'bdquo'    => 8222,
  89                 'Beta'     => 914,
  90                 'beta'     => 946,
  91                 'brvbar'   => 166,
  92                 'bull'     => 8226,
  93                 'cap'      => 8745,
  94                 'Ccedil'   => 199,
  95                 'ccedil'   => 231,
  96                 'cedil'    => 184,
  97                 'cent'     => 162,
  98                 'Chi'      => 935,
  99                 'chi'      => 967,
 100                 'circ'     => 710,
 101                 'clubs'    => 9827,
 102                 'cong'     => 8773,
 103                 'copy'     => 169,
 104                 'crarr'    => 8629,
 105                 'cup'      => 8746,
 106                 'curren'   => 164,
 107                 'dagger'   => 8224,
 108                 'Dagger'   => 8225,
 109                 'darr'     => 8595,
 110                 'dArr'     => 8659,
 111                 'deg'      => 176,
 112                 'Delta'    => 916,
 113                 'delta'    => 948,
 114                 'diams'    => 9830,
 115                 'divide'   => 247,
 116                 'Eacute'   => 201,
 117                 'eacute'   => 233,
 118                 'Ecirc'    => 202,
 119                 'ecirc'    => 234,
 120                 'Egrave'   => 200,
 121                 'egrave'   => 232,
 122                 'empty'    => 8709,
 123                 'emsp'     => 8195,
 124                 'ensp'     => 8194,
 125                 'Epsilon'  => 917,
 126                 'epsilon'  => 949,
 127                 'equiv'    => 8801,
 128                 'Eta'      => 919,
 129                 'eta'      => 951,
 130                 'ETH'      => 208,
 131                 'eth'      => 240,
 132                 'Euml'     => 203,
 133                 'euml'     => 235,
 134                 'euro'     => 8364,
 135                 'exist'    => 8707,
 136                 'fnof'     => 402,
 137                 'forall'   => 8704,
 138                 'frac12'   => 189,
 139                 'frac14'   => 188,
 140                 'frac34'   => 190,
 141                 'frasl'    => 8260,
 142                 'Gamma'    => 915,
 143                 'gamma'    => 947,
 144                 'ge'       => 8805,
 145                 'gt'       => 62,
 146                 'harr'     => 8596,
 147                 'hArr'     => 8660,
 148                 'hearts'   => 9829,
 149                 'hellip'   => 8230,
 150                 'Iacute'   => 205,
 151                 'iacute'   => 237,
 152                 'Icirc'    => 206,
 153                 'icirc'    => 238,
 154                 'iexcl'    => 161,
 155                 'Igrave'   => 204,
 156                 'igrave'   => 236,
 157                 'image'    => 8465,
 158                 'infin'    => 8734,
 159                 'int'      => 8747,
 160                 'Iota'     => 921,
 161                 'iota'     => 953,
 162                 'iquest'   => 191,
 163                 'isin'     => 8712,
 164                 'Iuml'     => 207,
 165                 'iuml'     => 239,
 166                 'Kappa'    => 922,
 167                 'kappa'    => 954,
 168                 'Lambda'   => 923,
 169                 'lambda'   => 955,
 170                 'lang'     => 9001,
 171                 'laquo'    => 171,
 172                 'larr'     => 8592,
 173                 'lArr'     => 8656,
 174                 'lceil'    => 8968,
 175                 'ldquo'    => 8220,
 176                 'le'       => 8804,
 177                 'lfloor'   => 8970,
 178                 'lowast'   => 8727,
 179                 'loz'      => 9674,
 180                 'lrm'      => 8206,
 181                 'lsaquo'   => 8249,
 182                 'lsquo'    => 8216,
 183                 'lt'       => 60,
 184                 'macr'     => 175,
 185                 'mdash'    => 8212,
 186                 'micro'    => 181,
 187                 'middot'   => 183,
 188                 'minus'    => 8722,
 189                 'Mu'       => 924,
 190                 'mu'       => 956,
 191                 'nabla'    => 8711,
 192                 'nbsp'     => 160,
 193                 'ndash'    => 8211,
 194                 'ne'       => 8800,
 195                 'ni'       => 8715,
 196                 'not'      => 172,
 197                 'notin'    => 8713,
 198                 'nsub'     => 8836,
 199                 'Ntilde'   => 209,
 200                 'ntilde'   => 241,
 201                 'Nu'       => 925,
 202                 'nu'       => 957,
 203                 'Oacute'   => 211,
 204                 'oacute'   => 243,
 205                 'Ocirc'    => 212,
 206                 'ocirc'    => 244,
 207                 'OElig'    => 338,
 208                 'oelig'    => 339,
 209                 'Ograve'   => 210,
 210                 'ograve'   => 242,
 211                 'oline'    => 8254,
 212                 'Omega'    => 937,
 213                 'omega'    => 969,
 214                 'Omicron'  => 927,
 215                 'omicron'  => 959,
 216                 'oplus'    => 8853,
 217                 'or'       => 8744,
 218                 'ordf'     => 170,
 219                 'ordm'     => 186,
 220                 'Oslash'   => 216,
 221                 'oslash'   => 248,
 222                 'Otilde'   => 213,
 223                 'otilde'   => 245,
 224                 'otimes'   => 8855,
 225                 'Ouml'     => 214,
 226                 'ouml'     => 246,
 227                 'para'     => 182,
 228                 'part'     => 8706,
 229                 'permil'   => 8240,
 230                 'perp'     => 8869,
 231                 'Phi'      => 934,
 232                 'phi'      => 966,
 233                 'Pi'       => 928,
 234                 'pi'       => 960,
 235                 'piv'      => 982,
 236                 'plusmn'   => 177,
 237                 'pound'    => 163,
 238                 'prime'    => 8242,
 239                 'Prime'    => 8243,
 240                 'prod'     => 8719,
 241                 'prop'     => 8733,
 242                 'Psi'      => 936,
 243                 'psi'      => 968,
 244                 'quot'     => 34,
 245                 'radic'    => 8730,
 246                 'rang'     => 9002,
 247                 'raquo'    => 187,
 248                 'rarr'     => 8594,
 249                 'rArr'     => 8658,
 250                 'rceil'    => 8969,
 251                 'rdquo'    => 8221,
 252                 'real'     => 8476,
 253                 'reg'      => 174,
 254                 'rfloor'   => 8971,
 255                 'Rho'      => 929,
 256                 'rho'      => 961,
 257                 'rlm'      => 8207,
 258                 'rsaquo'   => 8250,
 259                 'rsquo'    => 8217,
 260                 'sbquo'    => 8218,
 261                 'Scaron'   => 352,
 262                 'scaron'   => 353,
 263                 'sdot'     => 8901,
 264                 'sect'     => 167,
 265                 'shy'      => 173,
 266                 'Sigma'    => 931,
 267                 'sigma'    => 963,
 268                 'sigmaf'   => 962,
 269                 'sim'      => 8764,
 270                 'spades'   => 9824,
 271                 'sub'      => 8834,
 272                 'sube'     => 8838,
 273                 'sum'      => 8721,
 274                 'sup'      => 8835,
 275                 'sup1'     => 185,
 276                 'sup2'     => 178,
 277                 'sup3'     => 179,
 278                 'supe'     => 8839,
 279                 'szlig'    => 223,
 280                 'Tau'      => 932,
 281                 'tau'      => 964,
 282                 'there4'   => 8756,
 283                 'Theta'    => 920,
 284                 'theta'    => 952,
 285                 'thetasym' => 977,
 286                 'thinsp'   => 8201,
 287                 'THORN'    => 222,
 288                 'thorn'    => 254,
 289                 'tilde'    => 732,
 290                 'times'    => 215,
 291                 'trade'    => 8482,
 292                 'Uacute'   => 218,
 293                 'uacute'   => 250,
 294                 'uarr'     => 8593,
 295                 'uArr'     => 8657,
 296                 'Ucirc'    => 219,
 297                 'ucirc'    => 251,
 298                 'Ugrave'   => 217,
 299                 'ugrave'   => 249,
 300                 'uml'      => 168,
 301                 'upsih'    => 978,
 302                 'Upsilon'  => 933,
 303                 'upsilon'  => 965,
 304                 'Uuml'     => 220,
 305                 'uuml'     => 252,
 306                 'weierp'   => 8472,
 307                 'Xi'       => 926,
 308                 'xi'       => 958,
 309                 'Yacute'   => 221,
 310                 'yacute'   => 253,
 311                 'yen'      => 165,
 312                 'Yuml'     => 376,
 313                 'yuml'     => 255,
 314                 'Zeta'     => 918,
 315                 'zeta'     => 950,
 316                 'zwj'      => 8205,
 317                 'zwnj'     => 8204
 318         ];
 319
 320         /**
 321          * Character entity aliases accepted by MediaWiki
 322          */
 323         private static $htmlEntityAliases = [
 324                 'רלמ' => 'rlm',
 325                 'رلم' => 'rlm',
 326         ];
 327
 328         /**
 329          * Lazy-initialised attributes regex, see getAttribsRegex()
 330          */
 331         private static $attribsRegex;
 332
 333         /**
 334          * Regular expression to match HTML/XML attribute pairs within a tag.
 335          * Allows some... latitude. Based on,
 336          * http://www.w3.org/TR/html5/syntax.html#before-attribute-value-state
 337          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 338          * @return string
 339          */
 340         static function getAttribsRegex() {
 341                 if ( self::$attribsRegex === null ) {
 342                         $attribFirst = '[:A-Z_a-z0-9]';
 343                         $attrib = '[:A-Z_a-z-.0-9]';
 344                         $space = '[\x09\x0a\x0c\x0d\x20]';
 345                         self::$attribsRegex =
 346                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 347                                   ($space*=$space*
 348                                         (?:
 349                                          # The attribute value: quoted or alone
 350                                           \"([^\"]*)(?:\"|\$)
 351                                          | '([^']*)(?:'|\$)
 352                                          |  (((?!$space|>).)*)
 353                                         )
 354                                 )?(?=$space|\$)/sx";
 355                 }
 356                 return self::$attribsRegex;
 357         }
 358
 359         /**
 360          * Return the various lists of recognized tags
 361          * @param array $extratags For any extra tags to include
 362          * @param array $removetags For any tags (default or extra) to exclude
 363          * @return array
 364          */
 365         public static function getRecognizedTagData( $extratags = [], $removetags = [] ) {
 366                 global $wgAllowMicrodataAttributes, $wgAllowImageTag;
 367
 368                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 369                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 370
 371                 // Base our staticInitialised variable off of the global config state so that if the globals
 372                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 373                 $globalContext = implode( '-', compact( 'wgAllowMicrodataAttributes', 'wgAllowImageTag' ) );
 374                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 375                         $htmlpairsStatic = [ # Tags that must be closed
 376                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 377                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 378                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 379                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 380                                 'ruby', 'rb', 'rp', 'rt', 'rtc', 'p', 'span', 'abbr', 'dfn',
 381                                 'kbd', 'samp', 'data', 'time', 'mark'
 382                         ];
 383                         $htmlsingle = [
 384                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd'
 385                         ];
 386                         $htmlsingleonly = [ # Elements that cannot have close tags
 387                                 'br', 'wbr', 'hr'
 388                         ];
 389                         if ( $wgAllowMicrodataAttributes ) {
 390                                 $htmlsingle[] = $htmlsingleonly[] = 'meta';
 391                                 $htmlsingle[] = $htmlsingleonly[] = 'link';
 392                         }
 393                         $htmlnest = [ # Tags that can be nested--??
 394                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 395                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 396                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 397                         ];
 398                         $tabletags = [ # Can only appear inside table, we will close them
 399                                 'td', 'th', 'tr',
 400                         ];
 401                         $htmllist = [ # Tags used by list
 402                                 'ul', 'ol',
 403                         ];
 404                         $listtags = [ # Tags that can appear in a list
 405                                 'li',
 406                         ];
 407
 408                         if ( $wgAllowImageTag ) {
 409                                 $htmlsingle[] = 'img';
 410                                 $htmlsingleonly[] = 'img';
 411                         }
 412
 413                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 414                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 415
 416                         # Convert them all to hashtables for faster lookup
 417                         $vars = [ 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 418                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' ];
 419                         foreach ( $vars as $var ) {
 420                                 $$var = array_flip( $$var );
 421                         }
 422                         $staticInitialised = $globalContext;
 423                 }
 424
 425                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 426                 $extratags = array_flip( $extratags );
 427                 $removetags = array_flip( $removetags );
 428                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 429                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 430
 431                 return [
 432                         'htmlpairs' => $htmlpairs,
 433                         'htmlsingle' => $htmlsingle,
 434                         'htmlsingleonly' => $htmlsingleonly,
 435                         'htmlnest' => $htmlnest,
 436                         'tabletags' => $tabletags,
 437                         'htmllist' => $htmllist,
 438                         'listtags' => $listtags,
 439                         'htmlsingleallowed' => $htmlsingleallowed,
 440                         'htmlelements' => $htmlelements,
 441                 ];
 442         }
 443
 444         /**
 445          * Cleans up HTML, removes dangerous tags and attributes, and
 446          * removes HTML comments
 447          * @param string $text
 448          * @param callable $processCallback Callback to do any variable or parameter
 449          *   replacements in HTML attribute values
 450          * @param array|bool $args Arguments for the processing callback
 451          * @param array $extratags For any extra tags to include
 452          * @param array $removetags For any tags (default or extra) to exclude
 453          * @return string
 454          */
 455         public static function removeHTMLtags( $text, $processCallback = null,
 456                 $args = [], $extratags = [], $removetags = []
 457         ) {
 458                 extract( self::getRecognizedTagData( $extratags, $removetags ) );
 459
 460                 # Remove HTML comments
 461                 $text = Sanitizer::removeHTMLcomments( $text );
 462                 $bits = explode( '<', $text );
 463                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 464                 if ( !MWTidy::isEnabled() ) {
 465                         $tagstack = $tablestack = [];
 466                         foreach ( $bits as $x ) {
 467                                 $regs = [];
 468                                 # $slash: Does the current element start with a '/'?
 469                                 # $t: Current element name
 470                                 # $params: String between element name and >
 471                                 # $brace: Ending '>' or '/>'
 472                                 # $rest: Everything until the next element of $bits
 473                                 if ( preg_match( self::ELEMENT_BITS_REGEX, $x, $regs ) ) {
 474                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 475                                 } else {
 476                                         $slash = $t = $params = $brace = $rest = null;
 477                                 }
 478
 479                                 $badtag = false;
 480                                 $t = strtolower( $t );
 481                                 if ( isset( $htmlelements[$t] ) ) {
 482                                         # Check our stack
 483                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 484                                                 $badtag = true;
 485                                         } elseif ( $slash ) {
 486                                                 # Closing a tag... is it the one we just opened?
 487                                                 MediaWiki\suppressWarnings();
 488                                                 $ot = array_pop( $tagstack );
 489                                                 MediaWiki\restoreWarnings();
 490
 491                                                 if ( $ot != $t ) {
 492                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 493                                                                 # Pop all elements with an optional close tag
 494                                                                 # and see if we find a match below them
 495                                                                 $optstack = [];
 496                                                                 array_push( $optstack, $ot );
 497                                                                 MediaWiki\suppressWarnings();
 498                                                                 $ot = array_pop( $tagstack );
 499                                                                 MediaWiki\restoreWarnings();
 500                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 501                                                                         array_push( $optstack, $ot );
 502                                                                         MediaWiki\suppressWarnings();
 503                                                                         $ot = array_pop( $tagstack );
 504                                                                         MediaWiki\restoreWarnings();
 505                                                                 }
 506                                                                 if ( $t != $ot ) {
 507                                                                         # No match. Push the optional elements back again
 508                                                                         $badtag = true;
 509                                                                         MediaWiki\suppressWarnings();
 510                                                                         $ot = array_pop( $optstack );
 511                                                                         MediaWiki\restoreWarnings();
 512                                                                         while ( $ot ) {
 513                                                                                 array_push( $tagstack, $ot );
 514                                                                                 MediaWiki\suppressWarnings();
 515                                                                                 $ot = array_pop( $optstack );
 516                                                                                 MediaWiki\restoreWarnings();
 517                                                                         }
 518                                                                 }
 519                                                         } else {
 520                                                                 MediaWiki\suppressWarnings();
 521                                                                 array_push( $tagstack, $ot );
 522                                                                 MediaWiki\restoreWarnings();
 523
 524                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 525                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 526                                                                         $badtag = true;
 527                                                                 }
 528                                                         }
 529                                                 } else {
 530                                                         if ( $t == 'table' ) {
 531                                                                 $tagstack = array_pop( $tablestack );
 532                                                         }
 533                                                 }
 534                                                 $newparams = '';
 535                                         } else {
 536                                                 # Keep track for later
 537                                                 if ( isset( $tabletags[$t] ) && !in_array( 'table', $tagstack ) ) {
 538                                                         $badtag = true;
 539                                                 } elseif ( in_array( $t, $tagstack ) && !isset( $htmlnest[$t] ) ) {
 540                                                         $badtag = true;
 541                                                 #  Is it a self closed htmlpair ? (bug 5487)
 542                                                 } elseif ( $brace == '/>' && isset( $htmlpairs[$t] ) ) {
 543                                                         $badtag = true;
 544                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 545                                                         # Hack to force empty tag for unclosable elements
 546                                                         $brace = '/>';
 547                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 548                                                         # Hack to not close $htmlsingle tags
 549                                                         $brace = null;
 550                                                         # Still need to push this optionally-closed tag to
 551                                                         # the tag stack so that we can match end tags
 552                                                         # instead of marking them as bad.
 553                                                         array_push( $tagstack, $t );
 554                                                 } elseif ( isset( $tabletags[$t] ) && in_array( $t, $tagstack ) ) {
 555                                                         // New table tag but forgot to close the previous one
 556                                                         $text .= "</$t>";
 557                                                 } else {
 558                                                         if ( $t == 'table' ) {
 559                                                                 array_push( $tablestack, $tagstack );
 560                                                                 $tagstack = [];
 561                                                         }
 562                                                         array_push( $tagstack, $t );
 563                                                 }
 564
 565                                                 # Replace any variables or template parameters with
 566                                                 # plaintext results.
 567                                                 if ( is_callable( $processCallback ) ) {
 568                                                         call_user_func_array( $processCallback, [ &$params, $args ] );
 569                                                 }
 570
 571                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 572                                                         $badtag = true;
 573                                                 }
 574
 575                                                 # Strip non-approved attributes from the tag
 576                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 577                                         }
 578                                         if ( !$badtag ) {
 579                                                 $rest = str_replace( '>', '&gt;', $rest );
 580                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 581                                                 $text .= "<$slash$t$newparams$close>$rest";
 582                                                 continue;
 583                                         }
 584                                 }
 585                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 586                         }
 587                         # Close off any remaining tags
 588                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 589                                 $text .= "</$t>\n";
 590                                 if ( $t == 'table' ) {
 591                                         $tagstack = array_pop( $tablestack );
 592                                 }
 593                         }
 594                 } else {
 595                         # this might be possible using tidy itself
 596                         foreach ( $bits as $x ) {
 597                                 if ( preg_match( self::ELEMENT_BITS_REGEX, $x, $regs ) ) {
 598                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 599
 600                                         $badtag = false;
 601                                         $t = strtolower( $t );
 602                                         if ( isset( $htmlelements[$t] ) ) {
 603                                                 if ( is_callable( $processCallback ) ) {
 604                                                         call_user_func_array( $processCallback, [ &$params, $args ] );
 605                                                 }
 606
 607                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 608                                                         $badtag = true;
 609                                                 }
 610
 611                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 612                                                 if ( !$badtag ) {
 613                                                         $rest = str_replace( '>', '&gt;', $rest );
 614                                                         $text .= "<$slash$t$newparams$brace$rest";
 615                                                         continue;
 616                                                 }
 617                                         }
 618                                 }
 619                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 620                         }
 621                 }
 622                 return $text;
 623         }
 624
 625         /**
 626          * Remove '<!--', '-->', and everything between.
 627          * To avoid leaving blank lines, when a comment is both preceded
 628          * and followed by a newline (ignoring spaces), trim leading and
 629          * trailing spaces and one of the newlines.
 630          *
 631          * @param string $text
 632          * @return string
 633          */
 634         public static function removeHTMLcomments( $text ) {
 635                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 636                         $end = strpos( $text, '-->', $start + 4 );
 637                         if ( $end === false ) {
 638                                 # Unterminated comment; bail out
 639                                 break;
 640                         }
 641
 642                         $end += 3;
 643
 644                         # Trim space and newline if the comment is both
 645                         # preceded and followed by a newline
 646                         $spaceStart = max( $start - 1, 0 );
 647                         $spaceLen = $end - $spaceStart;
 648                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 649                                 $spaceStart--;
 650                                 $spaceLen++;
 651                         }
 652                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 653                                 $spaceLen++;
 654                         }
 655                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 656                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 657                                 # Remove the comment, leading and trailing
 658                                 # spaces, and leave only one newline.
 659                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 660                         } else {
 661                                 # Remove just the comment.
 662                                 $text = substr_replace( $text, '', $start, $end - $start );
 663                         }
 664                 }
 665                 return $text;
 666         }
 667
 668         /**
 669          * Takes attribute names and values for a tag and the tag name and
 670          * validates that the tag is allowed to be present.
 671          * This DOES NOT validate the attributes, nor does it validate the
 672          * tags themselves. This method only handles the special circumstances
 673          * where we may want to allow a tag within content but ONLY when it has
 674          * specific attributes set.
 675          *
 676          * @param string $params
 677          * @param string $element
 678          * @return bool
 679          */
 680         static function validateTag( $params, $element ) {
 681                 $params = Sanitizer::decodeTagAttributes( $params );
 682
 683                 if ( $element == 'meta' || $element == 'link' ) {
 684                         if ( !isset( $params['itemprop'] ) ) {
 685                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 686                                 return false;
 687                         }
 688                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 689                                 // <meta> must have a content="" for the itemprop
 690                                 return false;
 691                         }
 692                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 693                                 // <link> must have an associated href=""
 694                                 return false;
 695                         }
 696                 }
 697
 698                 return true;
 699         }
 700
 701         /**
 702          * Take an array of attribute names and values and normalize or discard
 703          * illegal values for the given element type.
 704          *
 705          * - Discards attributes not on a whitelist for the given element
 706          * - Unsafe style attributes are discarded
 707          * - Invalid id attributes are re-encoded
 708          *
 709          * @param array $attribs
 710          * @param string $element
 711          * @return array
 712          *
 713          * @todo Check for legal values where the DTD limits things.
 714          * @todo Check for unique id attribute :P
 715          */
 716         static function validateTagAttributes( $attribs, $element ) {
 717                 return Sanitizer::validateAttributes( $attribs,
 718                         Sanitizer::attributeWhitelist( $element ) );
 719         }
 720
 721         /**
 722          * Take an array of attribute names and values and normalize or discard
 723          * illegal values for the given whitelist.
 724          *
 725          * - Discards attributes not on the given whitelist
 726          * - Unsafe style attributes are discarded
 727          * - Invalid id attributes are re-encoded
 728          *
 729          * @param array $attribs
 730          * @param array $whitelist List of allowed attribute names
 731          * @return array
 732          *
 733          * @todo Check for legal values where the DTD limits things.
 734          * @todo Check for unique id attribute :P
 735          */
 736         static function validateAttributes( $attribs, $whitelist ) {
 737                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 738
 739                 $whitelist = array_flip( $whitelist );
 740                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 741
 742                 $out = [];
 743                 foreach ( $attribs as $attribute => $value ) {
 744                         # allow XML namespace declaration if RDFa is enabled
 745                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 746                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 747                                         $out[$attribute] = $value;
 748                                 }
 749
 750                                 continue;
 751                         }
 752
 753                         # Allow any attribute beginning with "data-"
 754                         # However:
 755                         # * data-ooui is reserved for ooui
 756                         # * data-mw and data-parsoid are reserved for parsoid
 757                         # * data-mw-<name here> is reserved for extensions (or core) if
 758                         #   they need to communicate some data to the client and want to be
 759                         #   sure that it isn't coming from an untrusted user.
 760                         # * Ensure that the attribute is not namespaced by banning
 761                         #   colons.
 762                         if ( !preg_match( '/^data-(?!ooui|mw|parsoid)[^:]*$/i', $attribute )
 763                                 && !isset( $whitelist[$attribute] )
 764                         ) {
 765                                 continue;
 766                         }
 767
 768                         # Strip javascript "expression" from stylesheets.
 769                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 770                         if ( $attribute == 'style' ) {
 771                                 $value = Sanitizer::checkCss( $value );
 772                         }
 773
 774                         # Escape HTML id attributes
 775                         if ( $attribute === 'id' ) {
 776                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 777                         }
 778
 779                         # Escape HTML id reference lists
 780                         if ( $attribute === 'aria-describedby'
 781                                 || $attribute === 'aria-flowto'
 782                                 || $attribute === 'aria-labelledby'
 783                                 || $attribute === 'aria-owns'
 784                         ) {
 785                                 $value = Sanitizer::escapeIdReferenceList( $value, 'noninitial' );
 786                         }
 787
 788                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 789                         // Check them for sanity.
 790                         if ( $attribute === 'rel' || $attribute === 'rev'
 791                                 # RDFa
 792                                 || $attribute === 'about' || $attribute === 'property'
 793                                 || $attribute === 'resource' || $attribute === 'datatype'
 794                                 || $attribute === 'typeof'
 795                                 # HTML5 microdata
 796                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 797                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 798                                 || $attribute === 'itemtype'
 799                         ) {
 800                                 // Paranoia. Allow "simple" values but suppress javascript
 801                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 802                                         continue;
 803                                 }
 804                         }
 805
 806                         # NOTE: even though elements using href/src are not allowed directly, supply
 807                         #       validation code that can be used by tag hook handlers, etc
 808                         if ( $attribute === 'href' || $attribute === 'src' ) {
 809                                 if ( !preg_match( $hrefExp, $value ) ) {
 810                                         continue; // drop any href or src attributes not using an allowed protocol.
 811                                         // NOTE: this also drops all relative URLs
 812                                 }
 813                         }
 814
 815                         // If this attribute was previously set, override it.
 816                         // Output should only have one attribute of each name.
 817                         $out[$attribute] = $value;
 818                 }
 819
 820                 if ( $wgAllowMicrodataAttributes ) {
 821                         # itemtype, itemid, itemref don't make sense without itemscope
 822                         if ( !array_key_exists( 'itemscope', $out ) ) {
 823                                 unset( $out['itemtype'] );
 824                                 unset( $out['itemid'] );
 825                                 unset( $out['itemref'] );
 826                         }
 827                         # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 828                 }
 829                 return $out;
 830         }
 831
 832         /**
 833          * Merge two sets of HTML attributes.  Conflicting items in the second set
 834          * will override those in the first, except for 'class' attributes which
 835          * will be combined (if they're both strings).
 836          *
 837          * @todo implement merging for other attributes such as style
 838          * @param array $a
 839          * @param array $b
 840          * @return array
 841          */
 842         static function mergeAttributes( $a, $b ) {
 843                 $out = array_merge( $a, $b );
 844                 if ( isset( $a['class'] ) && isset( $b['class'] )
 845                         && is_string( $a['class'] ) && is_string( $b['class'] )
 846                         && $a['class'] !== $b['class']
 847                 ) {
 848                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 849                                 -1, PREG_SPLIT_NO_EMPTY );
 850                         $out['class'] = implode( ' ', array_unique( $classes ) );
 851                 }
 852                 return $out;
 853         }
 854
 855         /**
 856          * Normalize CSS into a format we can easily search for hostile input
 857          *  - decode character references
 858          *  - decode escape sequences
 859          *  - convert characters that IE6 interprets into ascii
 860          *  - remove comments, unless the entire value is one single comment
 861          * @param string $value the css string
 862          * @return string normalized css
 863          */
 864         public static function normalizeCss( $value ) {
 865
 866                 // Decode character references like &#123;
 867                 $value = Sanitizer::decodeCharReferences( $value );
 868
 869                 // Decode escape sequences and line continuation
 870                 // See the grammar in the CSS 2 spec, appendix D.
 871                 // This has to be done AFTER decoding character references.
 872                 // This means it isn't possible for this function to return
 873                 // unsanitized escape sequences. It is possible to manufacture
 874                 // input that contains character references that decode to
 875                 // escape sequences that decode to character references, but
 876                 // it's OK for the return value to contain character references
 877                 // because the caller is supposed to escape those anyway.
 878                 static $decodeRegex;
 879                 if ( !$decodeRegex ) {
 880                         $space = '[\\x20\\t\\r\\n\\f]';
 881                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 882                         $backslash = '\\\\';
 883                         $decodeRegex = "/ $backslash
 884                                 (?:
 885                                         ($nl) |  # 1. Line continuation
 886                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 887                                         (.) | # 3. backslash cancelling special meaning
 888                                         () | # 4. backslash at end of string
 889                                 )/xu";
 890                 }
 891                 $value = preg_replace_callback( $decodeRegex,
 892                         [ __CLASS__, 'cssDecodeCallback' ], $value );
 893
 894                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 895                 $value = preg_replace_callback(
 896                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (bug 58088)
 897                         function ( $matches ) {
 898                                 $cp = UtfNormal\Utils::utf8ToCodepoint( $matches[0] );
 899                                 if ( $cp === false ) {
 900                                         return '';
 901                                 }
 902                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 903                         },
 904                         $value
 905                 );
 906
 907                 // Convert more characters IE6 might treat as ascii
 908                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 909                 $value = str_replace(
 910                         [ 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ],
 911                         [ 'r', 'n', 'n', 'l', 'i', '(', '(' ],
 912                         $value
 913                 );
 914
 915                 // Let the value through if it's nothing but a single comment, to
 916                 // allow other functions which may reject it to pass some error
 917                 // message through.
 918                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 919                         // Remove any comments; IE gets token splitting wrong
 920                         // This must be done AFTER decoding character references and
 921                         // escape sequences, because those steps can introduce comments
 922                         // This step cannot introduce character references or escape
 923                         // sequences, because it replaces comments with spaces rather
 924                         // than removing them completely.
 925                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 926
 927                         // Remove anything after a comment-start token, to guard against
 928                         // incorrect client implementations.
 929                         $commentPos = strpos( $value, '/*' );
 930                         if ( $commentPos !== false ) {
 931                                 $value = substr( $value, 0, $commentPos );
 932                         }
 933                 }
 934
 935                 // S followed by repeat, iteration, or prolonged sound marks,
 936                 // which IE will treat as "ss"
 937                 $value = preg_replace(
 938                         '/s(?:
 939                                 \xE3\x80\xB1 | # U+3031
 940                                 \xE3\x82\x9D | # U+309D
 941                                 \xE3\x83\xBC | # U+30FC
 942                                 \xE3\x83\xBD | # U+30FD
 943                                 \xEF\xB9\xBC | # U+FE7C
 944                                 \xEF\xB9\xBD | # U+FE7D
 945                                 \xEF\xBD\xB0   # U+FF70
 946                         )/ix',
 947                         'ss',
 948                         $value
 949                 );
 950
 951                 return $value;
 952         }
 953
 954         /**
 955          * Pick apart some CSS and check it for forbidden or unsafe structures.
 956          * Returns a sanitized string. This sanitized string will have
 957          * character references and escape sequences decoded and comments
 958          * stripped (unless it is itself one valid comment, in which case the value
 959          * will be passed through). If the input is just too evil, only a comment
 960          * complaining about evilness will be returned.
 961          *
 962          * Currently URL references, 'expression', 'tps' are forbidden.
 963          *
 964          * NOTE: Despite the fact that character references are decoded, the
 965          * returned string may contain character references given certain
 966          * clever input strings. These character references must
 967          * be escaped before the return value is embedded in HTML.
 968          *
 969          * @param string $value
 970          * @return string
 971          */
 972         static function checkCss( $value ) {
 973                 $value = self::normalizeCss( $value );
 974
 975                 // Reject problematic keywords and control characters
 976                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ||
 977                         strpos( $value, UtfNormal\Constants::UTF8_REPLACEMENT ) !== false ) {
 978                         return '/* invalid control char */';
 979                 } elseif ( preg_match(
 980                         '! expression
 981                                 | filter\s*:
 982                                 | accelerator\s*:
 983                                 | -o-link\s*:
 984                                 | -o-link-source\s*:
 985                                 | -o-replace\s*:
 986                                 | url\s*\(
 987                                 | image\s*\(
 988                                 | image-set\s*\(
 989                         !ix', $value ) ) {
 990                         return '/* insecure input */';
 991                 }
 992                 return $value;
 993         }
 994
 995         /**
 996          * @param array $matches
 997          * @return string
 998          */
 999         static function cssDecodeCallback( $matches ) {
1000                 if ( $matches[1] !== '' ) {
1001                         // Line continuation
1002                         return '';
1003                 } elseif ( $matches[2] !== '' ) {
1004                         $char = UtfNormal\Utils::codepointToUtf8( hexdec( $matches[2] ) );
1005                 } elseif ( $matches[3] !== '' ) {
1006                         $char = $matches[3];
1007                 } else {
1008                         $char = '\\';
1009                 }
1010                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
1011                         // These characters need to be escaped in strings
1012                         // Clean up the escape sequence to avoid parsing errors by clients
1013                         return '\\' . dechex( ord( $char ) ) . ' ';
1014                 } else {
1015                         // Decode unnecessary escape
1016                         return $char;
1017                 }
1018         }
1019
1020         /**
1021          * Take a tag soup fragment listing an HTML element's attributes
1022          * and normalize it to well-formed XML, discarding unwanted attributes.
1023          * Output is safe for further wikitext processing, with escaping of
1024          * values that could trigger problems.
1025          *
1026          * - Normalizes attribute names to lowercase
1027          * - Discards attributes not on a whitelist for the given element
1028          * - Turns broken or invalid entities into plaintext
1029          * - Double-quotes all attribute values
1030          * - Attributes without values are given the name as attribute
1031          * - Double attributes are discarded
1032          * - Unsafe style attributes are discarded
1033          * - Prepends space if there are attributes.
1034          *
1035          * @param string $text
1036          * @param string $element
1037          * @return string
1038          */
1039         static function fixTagAttributes( $text, $element ) {
1040                 if ( trim( $text ) == '' ) {
1041                         return '';
1042                 }
1043
1044                 $decoded = Sanitizer::decodeTagAttributes( $text );
1045                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
1046
1047                 return Sanitizer::safeEncodeTagAttributes( $stripped );
1048         }
1049
1050         /**
1051          * Encode an attribute value for HTML output.
1052          * @param string $text
1053          * @return string HTML-encoded text fragment
1054          */
1055         static function encodeAttribute( $text ) {
1056                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1057
1058                 // Whitespace is normalized during attribute decoding,
1059                 // so if we've been passed non-spaces we must encode them
1060                 // ahead of time or they won't be preserved.
1061                 $encValue = strtr( $encValue, [
1062                         "\n" => '&#10;',
1063                         "\r" => '&#13;',
1064                         "\t" => '&#9;',
1065                 ] );
1066
1067                 return $encValue;
1068         }
1069
1070         /**
1071          * Encode an attribute value for HTML tags, with extra armoring
1072          * against further wiki processing.
1073          * @param string $text
1074          * @return string HTML-encoded text fragment
1075          */
1076         static function safeEncodeAttribute( $text ) {
1077                 $encValue = Sanitizer::encodeAttribute( $text );
1078
1079                 # Templates and links may be expanded in later parsing,
1080                 # creating invalid or dangerous output. Suppress this.
1081                 $encValue = strtr( $encValue, [
1082                         '<'    => '&lt;',   // This should never happen,
1083                         '>'    => '&gt;',   // we've received invalid input
1084                         '"'    => '&quot;', // which should have been escaped.
1085                         '{'    => '&#123;',
1086                         '['    => '&#91;',
1087                         "''"   => '&#39;&#39;',
1088                         'ISBN' => '&#73;SBN',
1089                         'RFC'  => '&#82;FC',
1090                         'PMID' => '&#80;MID',
1091                         '|'    => '&#124;',
1092                         '__'   => '&#95;_',
1093                 ] );
1094
1095                 # Stupid hack
1096                 $encValue = preg_replace_callback(
1097                         '/((?i)' . wfUrlProtocols() . ')/',
1098                         [ 'Sanitizer', 'armorLinksCallback' ],
1099                         $encValue );
1100                 return $encValue;
1101         }
1102
1103         /**
1104          * Given a value, escape it so that it can be used in an id attribute and
1105          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1106          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1107          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1108          * escaped with lots of dots.
1109          *
1110          * To ensure we don't have to bother escaping anything, we also strip ', ",
1111          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1112          * We also strip # because it upsets IE, and % because it could be
1113          * ambiguous if it's part of something that looks like a percent escape
1114          * (which don't work reliably in fragments cross-browser).
1115          *
1116          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
1117          *   in the id and name attributes
1118          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1119          *   the id attribute
1120          * @see http://www.whatwg.org/html/elements.html#the-id-attribute
1121          *   HTML5 definition of id attribute
1122          *
1123          * @param string $id Id to escape
1124          * @param string|array $options String or array of strings (default is array()):
1125          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1126          *       so don't pay attention if the first character isn't valid at the
1127          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1128          *       false.
1129          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1130          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1131          *       anchors and links won't break.
1132          * @return string
1133          */
1134         static function escapeId( $id, $options = [] ) {
1135                 global $wgExperimentalHtmlIds;
1136                 $options = (array)$options;
1137
1138                 $id = Sanitizer::decodeCharReferences( $id );
1139
1140                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1141                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1142                         $id = trim( $id, '_' );
1143                         if ( $id === '' ) {
1144                                 // Must have been all whitespace to start with.
1145                                 return '_';
1146                         } else {
1147                                 return $id;
1148                         }
1149                 }
1150
1151                 // HTML4-style escaping
1152                 static $replace = [
1153                         '%3A' => ':',
1154                         '%' => '.'
1155                 ];
1156
1157                 $id = urlencode( strtr( $id, ' ', '_' ) );
1158                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1159
1160                 if ( !preg_match( '/^[a-zA-Z]/', $id ) && !in_array( 'noninitial', $options ) ) {
1161                         // Initial character must be a letter!
1162                         $id = "x$id";
1163                 }
1164                 return $id;
1165         }
1166
1167         /**
1168          * Given a string containing a space delimited list of ids, escape each id
1169          * to match ids escaped by the escapeId() function.
1170          *
1171          * @since 1.27
1172          *
1173          * @param string $referenceString Space delimited list of ids
1174          * @param string|array $options String or array of strings (default is array()):
1175          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1176          *       so don't pay attention if the first character isn't valid at the
1177          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1178          *       false.
1179          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1180          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1181          *       anchors and links won't break.
1182          * @return string
1183          */
1184         static function escapeIdReferenceList( $referenceString, $options = [] ) {
1185                 # Explode the space delimited list string into an array of tokens
1186                 $references = preg_split( '/\s+/', "{$referenceString}", -1, PREG_SPLIT_NO_EMPTY );
1187
1188                 # Escape each token as an id
1189                 foreach ( $references as &$ref ) {
1190                         $ref = Sanitizer::escapeId( $ref, $options );
1191                 }
1192
1193                 # Merge the array back to a space delimited list string
1194                 # If the array is empty, the result will be an empty string ('')
1195                 $referenceString = implode( ' ', $references );
1196
1197                 return $referenceString;
1198         }
1199
1200         /**
1201          * Given a value, escape it so that it can be used as a CSS class and
1202          * return it.
1203          *
1204          * @todo For extra validity, input should be validated UTF-8.
1205          *
1206          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1207          *
1208          * @param string $class
1209          * @return string
1210          */
1211         static function escapeClass( $class ) {
1212                 // Convert ugly stuff to underscores and kill underscores in ugly places
1213                 return rtrim( preg_replace(
1214                         [ '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ],
1215                         '_',
1216                         $class ), '_' );
1217         }
1218
1219         /**
1220          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1221          * This allows (generally harmless) entities like &#160; to survive.
1222          *
1223          * @param string $html HTML to escape
1224          * @return string Escaped input
1225          */
1226         static function escapeHtmlAllowEntities( $html ) {
1227                 $html = Sanitizer::decodeCharReferences( $html );
1228                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1229                 # hurt.
1230                 $html = htmlspecialchars( $html, ENT_QUOTES );
1231                 return $html;
1232         }
1233
1234         /**
1235          * Regex replace callback for armoring links against further processing.
1236          * @param array $matches
1237          * @return string
1238          */
1239         private static function armorLinksCallback( $matches ) {
1240                 return str_replace( ':', '&#58;', $matches[1] );
1241         }
1242
1243         /**
1244          * Return an associative array of attribute names and values from
1245          * a partial tag string. Attribute names are forced to lowercase,
1246          * character references are decoded to UTF-8 text.
1247          *
1248          * @param string $text
1249          * @return array
1250          */
1251         public static function decodeTagAttributes( $text ) {
1252                 if ( trim( $text ) == '' ) {
1253                         return [];
1254                 }
1255
1256                 $attribs = [];
1257                 $pairs = [];
1258                 if ( !preg_match_all(
1259                         self::getAttribsRegex(),
1260                         $text,
1261                         $pairs,
1262                         PREG_SET_ORDER ) ) {
1263                         return $attribs;
1264                 }
1265
1266                 foreach ( $pairs as $set ) {
1267                         $attribute = strtolower( $set[1] );
1268                         $value = Sanitizer::getTagAttributeCallback( $set );
1269
1270                         // Normalize whitespace
1271                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1272                         $value = trim( $value );
1273
1274                         // Decode character references
1275                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1276                 }
1277                 return $attribs;
1278         }
1279
1280         /**
1281          * Build a partial tag string from an associative array of attribute
1282          * names and values as returned by decodeTagAttributes.
1283          *
1284          * @param array $assoc_array
1285          * @return string
1286          */
1287         public static function safeEncodeTagAttributes( $assoc_array ) {
1288                 $attribs = [];
1289                 foreach ( $assoc_array as $attribute => $value ) {
1290                         $encAttribute = htmlspecialchars( $attribute );
1291                         $encValue = Sanitizer::safeEncodeAttribute( $value );
1292
1293                         $attribs[] = "$encAttribute=\"$encValue\"";
1294                 }
1295                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1296         }
1297
1298         /**
1299          * Pick the appropriate attribute value from a match set from the
1300          * attribs regex matches.
1301          *
1302          * @param array $set
1303          * @throws MWException When tag conditions are not met.
1304          * @return string
1305          */
1306         private static function getTagAttributeCallback( $set ) {
1307                 if ( isset( $set[5] ) ) {
1308                         # No quotes.
1309                         return $set[5];
1310                 } elseif ( isset( $set[4] ) ) {
1311                         # Single-quoted
1312                         return $set[4];
1313                 } elseif ( isset( $set[3] ) ) {
1314                         # Double-quoted
1315                         return $set[3];
1316                 } elseif ( !isset( $set[2] ) ) {
1317                         # In XHTML, attributes must have a value so return an empty string.
1318                         # See "Empty attribute syntax",
1319                         # http://www.w3.org/TR/html5/syntax.html#syntax-attribute-name
1320                         return "";
1321                 } else {
1322                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1323                 }
1324         }
1325
1326         /**
1327          * @param string $text
1328          * @return string
1329          */
1330         private static function normalizeWhitespace( $text ) {
1331                 return preg_replace(
1332                         '/\r\n|[\x20\x0d\x0a\x09]/',
1333                         ' ',
1334                         $text );
1335         }
1336
1337         /**
1338          * Normalizes whitespace in a section name, such as might be returned
1339          * by Parser::stripSectionName(), for use in the id's that are used for
1340          * section links.
1341          *
1342          * @param string $section
1343          * @return string
1344          */
1345         static function normalizeSectionNameWhitespace( $section ) {
1346                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1347         }
1348
1349         /**
1350          * Ensure that any entities and character references are legal
1351          * for XML and XHTML specifically. Any stray bits will be
1352          * &amp;-escaped to result in a valid text fragment.
1353          *
1354          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1355          *   numericized (this way we're well-formed even without a DTD)
1356          * b. any numeric char refs must be legal chars, not invalid or forbidden
1357          * c. use lower cased "&#x", not "&#X"
1358          * d. fix or reject non-valid attributes
1359          *
1360          * @param string $text
1361          * @return string
1362          * @private
1363          */
1364         static function normalizeCharReferences( $text ) {
1365                 return preg_replace_callback(
1366                         self::CHAR_REFS_REGEX,
1367                         [ 'Sanitizer', 'normalizeCharReferencesCallback' ],
1368                         $text );
1369         }
1370
1371         /**
1372          * @param string $matches
1373          * @return string
1374          */
1375         static function normalizeCharReferencesCallback( $matches ) {
1376                 $ret = null;
1377                 if ( $matches[1] != '' ) {
1378                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1379                 } elseif ( $matches[2] != '' ) {
1380                         $ret = Sanitizer::decCharReference( $matches[2] );
1381                 } elseif ( $matches[3] != '' ) {
1382                         $ret = Sanitizer::hexCharReference( $matches[3] );
1383                 }
1384                 if ( is_null( $ret ) ) {
1385                         return htmlspecialchars( $matches[0] );
1386                 } else {
1387                         return $ret;
1388                 }
1389         }
1390
1391         /**
1392          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1393          * return the equivalent numeric entity reference (except for the core &lt;
1394          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1395          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1396          * pseudo-entity source (eg &amp;foo;)
1397          *
1398          * @param string $name
1399          * @return string
1400          */
1401         static function normalizeEntity( $name ) {
1402                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1403                         return '&' . self::$htmlEntityAliases[$name] . ';';
1404                 } elseif ( in_array( $name, [ 'lt', 'gt', 'amp', 'quot' ] ) ) {
1405                         return "&$name;";
1406                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1407                         return '&#' . self::$htmlEntities[$name] . ';';
1408                 } else {
1409                         return "&amp;$name;";
1410                 }
1411         }
1412
1413         /**
1414          * @param int $codepoint
1415          * @return null|string
1416          */
1417         static function decCharReference( $codepoint ) {
1418                 $point = intval( $codepoint );
1419                 if ( Sanitizer::validateCodepoint( $point ) ) {
1420                         return sprintf( '&#%d;', $point );
1421                 } else {
1422                         return null;
1423                 }
1424         }
1425
1426         /**
1427          * @param int $codepoint
1428          * @return null|string
1429          */
1430         static function hexCharReference( $codepoint ) {
1431                 $point = hexdec( $codepoint );
1432                 if ( Sanitizer::validateCodepoint( $point ) ) {
1433                         return sprintf( '&#x%x;', $point );
1434                 } else {
1435                         return null;
1436                 }
1437         }
1438
1439         /**
1440          * Returns true if a given Unicode codepoint is a valid character in
1441          * both HTML5 and XML.
1442          * @param int $codepoint
1443          * @return bool
1444          */
1445         private static function validateCodepoint( $codepoint ) {
1446                 # U+000C is valid in HTML5 but not allowed in XML.
1447                 # U+000D is valid in XML but not allowed in HTML5.
1448                 # U+007F - U+009F are disallowed in HTML5 (control characters).
1449                 return $codepoint == 0x09
1450                         || $codepoint == 0x0a
1451                         || ( $codepoint >= 0x20 && $codepoint <= 0x7e )
1452                         || ( $codepoint >= 0xa0 && $codepoint <= 0xd7ff )
1453                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1454                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1455         }
1456
1457         /**
1458          * Decode any character references, numeric or named entities,
1459          * in the text and return a UTF-8 string.
1460          *
1461          * @param string $text
1462          * @return string
1463          */
1464         public static function decodeCharReferences( $text ) {
1465                 return preg_replace_callback(
1466                         self::CHAR_REFS_REGEX,
1467                         [ 'Sanitizer', 'decodeCharReferencesCallback' ],
1468                         $text );
1469         }
1470
1471         /**
1472          * Decode any character references, numeric or named entities,
1473          * in the next and normalize the resulting string. (bug 14952)
1474          *
1475          * This is useful for page titles, not for text to be displayed,
1476          * MediaWiki allows HTML entities to escape normalization as a feature.
1477          *
1478          * @param string $text Already normalized, containing entities
1479          * @return string Still normalized, without entities
1480          */
1481         public static function decodeCharReferencesAndNormalize( $text ) {
1482                 global $wgContLang;
1483                 $text = preg_replace_callback(
1484                         self::CHAR_REFS_REGEX,
1485                         [ 'Sanitizer', 'decodeCharReferencesCallback' ],
1486                         $text, /* limit */ -1, $count );
1487
1488                 if ( $count ) {
1489                         return $wgContLang->normalize( $text );
1490                 } else {
1491                         return $text;
1492                 }
1493         }
1494
1495         /**
1496          * @param string $matches
1497          * @return string
1498          */
1499         static function decodeCharReferencesCallback( $matches ) {
1500                 if ( $matches[1] != '' ) {
1501                         return Sanitizer::decodeEntity( $matches[1] );
1502                 } elseif ( $matches[2] != '' ) {
1503                         return Sanitizer::decodeChar( intval( $matches[2] ) );
1504                 } elseif ( $matches[3] != '' ) {
1505                         return Sanitizer::decodeChar( hexdec( $matches[3] ) );
1506                 }
1507                 # Last case should be an ampersand by itself
1508                 return $matches[0];
1509         }
1510
1511         /**
1512          * Return UTF-8 string for a codepoint if that is a valid
1513          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1514          * @param int $codepoint
1515          * @return string
1516          * @private
1517          */
1518         static function decodeChar( $codepoint ) {
1519                 if ( Sanitizer::validateCodepoint( $codepoint ) ) {
1520                         return UtfNormal\Utils::codepointToUtf8( $codepoint );
1521                 } else {
1522                         return UtfNormal\Constants::UTF8_REPLACEMENT;
1523                 }
1524         }
1525
1526         /**
1527          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1528          * return the UTF-8 encoding of that character. Otherwise, returns
1529          * pseudo-entity source (eg "&foo;")
1530          *
1531          * @param string $name
1532          * @return string
1533          */
1534         static function decodeEntity( $name ) {
1535                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1536                         $name = self::$htmlEntityAliases[$name];
1537                 }
1538                 if ( isset( self::$htmlEntities[$name] ) ) {
1539                         return UtfNormal\Utils::codepointToUtf8( self::$htmlEntities[$name] );
1540                 } else {
1541                         return "&$name;";
1542                 }
1543         }
1544
1545         /**
1546          * Fetch the whitelist of acceptable attributes for a given element name.
1547          *
1548          * @param string $element
1549          * @return array
1550          */
1551         static function attributeWhitelist( $element ) {
1552                 $list = Sanitizer::setupAttributeWhitelist();
1553                 return isset( $list[$element] )
1554                         ? $list[$element]
1555                         : [];
1556         }
1557
1558         /**
1559          * Foreach array key (an allowed HTML element), return an array
1560          * of allowed attributes
1561          * @return array
1562          */
1563         static function setupAttributeWhitelist() {
1564                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
1565                 static $whitelist, $staticInitialised;
1566
1567                 $globalContext = implode( '-', compact( 'wgAllowRdfaAttributes', 'wgAllowMicrodataAttributes' ) );
1568
1569                 if ( $whitelist !== null && $staticInitialised == $globalContext ) {
1570                         return $whitelist;
1571                 }
1572
1573                 $common = [
1574                         # HTML
1575                         'id',
1576                         'class',
1577                         'style',
1578                         'lang',
1579                         'dir',
1580                         'title',
1581
1582                         # WAI-ARIA
1583                         'aria-describedby',
1584                         'aria-flowto',
1585                         'aria-label',
1586                         'aria-labelledby',
1587                         'aria-owns',
1588                         'role',
1589                 ];
1590
1591                 if ( $wgAllowRdfaAttributes ) {
1592                         # RDFa attributes as specified in section 9 of
1593                         # http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1594                         $common = array_merge( $common, [
1595                                 'about', 'property', 'resource', 'datatype', 'typeof',
1596                         ] );
1597                 }
1598
1599                 if ( $wgAllowMicrodataAttributes ) {
1600                         # add HTML5 microdata tags as specified by
1601                         # http://www.whatwg.org/html/microdata.html#the-microdata-model
1602                         $common = array_merge( $common, [
1603                                 'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1604                         ] );
1605                 }
1606
1607                 $block = array_merge( $common, [ 'align' ] );
1608                 $tablealign = [ 'align', 'valign' ];
1609                 $tablecell = [
1610                         'abbr',
1611                         'axis',
1612                         'headers',
1613                         'scope',
1614                         'rowspan',
1615                         'colspan',
1616                         'nowrap', # deprecated
1617                         'width', # deprecated
1618                         'height', # deprecated
1619                         'bgcolor', # deprecated
1620                 ];
1621
1622                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1623                 # See: http://www.w3.org/TR/html4/
1624                 $whitelist = [
1625                         # 7.5.4
1626                         'div'        => $block,
1627                         'center'     => $common, # deprecated
1628                         'span'       => $common,
1629
1630                         # 7.5.5
1631                         'h1'         => $block,
1632                         'h2'         => $block,
1633                         'h3'         => $block,
1634                         'h4'         => $block,
1635                         'h5'         => $block,
1636                         'h6'         => $block,
1637
1638                         # 7.5.6
1639                         # address
1640
1641                         # 8.2.4
1642                         'bdo'        => $common,
1643
1644                         # 9.2.1
1645                         'em'         => $common,
1646                         'strong'     => $common,
1647                         'cite'       => $common,
1648                         'dfn'        => $common,
1649                         'code'       => $common,
1650                         'samp'       => $common,
1651                         'kbd'        => $common,
1652                         'var'        => $common,
1653                         'abbr'       => $common,
1654                         # acronym
1655
1656                         # 9.2.2
1657                         'blockquote' => array_merge( $common, [ 'cite' ] ),
1658                         'q'          => array_merge( $common, [ 'cite' ] ),
1659
1660                         # 9.2.3
1661                         'sub'        => $common,
1662                         'sup'        => $common,
1663
1664                         # 9.3.1
1665                         'p'          => $block,
1666
1667                         # 9.3.2
1668                         'br'         => array_merge( $common, [ 'clear' ] ),
1669
1670                         # http://www.whatwg.org/html/text-level-semantics.html#the-wbr-element
1671                         'wbr'        => $common,
1672
1673                         # 9.3.4
1674                         'pre'        => array_merge( $common, [ 'width' ] ),
1675
1676                         # 9.4
1677                         'ins'        => array_merge( $common, [ 'cite', 'datetime' ] ),
1678                         'del'        => array_merge( $common, [ 'cite', 'datetime' ] ),
1679
1680                         # 10.2
1681                         'ul'         => array_merge( $common, [ 'type' ] ),
1682                         'ol'         => array_merge( $common, [ 'type', 'start', 'reversed' ] ),
1683                         'li'         => array_merge( $common, [ 'type', 'value' ] ),
1684
1685                         # 10.3
1686                         'dl'         => $common,
1687                         'dd'         => $common,
1688                         'dt'         => $common,
1689
1690                         # 11.2.1
1691                         'table'      => array_merge( $common,
1692                                                                 [ 'summary', 'width', 'border', 'frame',
1693                                                                                 'rules', 'cellspacing', 'cellpadding',
1694                                                                                 'align', 'bgcolor',
1695                                                                 ] ),
1696
1697                         # 11.2.2
1698                         'caption'    => $block,
1699
1700                         # 11.2.3
1701                         'thead'      => $common,
1702                         'tfoot'      => $common,
1703                         'tbody'      => $common,
1704
1705                         # 11.2.4
1706                         'colgroup'   => array_merge( $common, [ 'span' ] ),
1707                         'col'        => array_merge( $common, [ 'span' ] ),
1708
1709                         # 11.2.5
1710                         'tr'         => array_merge( $common, [ 'bgcolor' ], $tablealign ),
1711
1712                         # 11.2.6
1713                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1714                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1715
1716                         # 12.2
1717                         # NOTE: <a> is not allowed directly, but the attrib
1718                         # whitelist is used from the Parser object
1719                         'a'          => array_merge( $common, [ 'href', 'rel', 'rev' ] ), # rel/rev esp. for RDFa
1720
1721                         # 13.2
1722                         # Not usually allowed, but may be used for extension-style hooks
1723                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1724                         # true
1725                         'img'        => array_merge( $common, [ 'alt', 'src', 'width', 'height' ] ),
1726
1727                         # 15.2.1
1728                         'tt'         => $common,
1729                         'b'          => $common,
1730                         'i'          => $common,
1731                         'big'        => $common,
1732                         'small'      => $common,
1733                         'strike'     => $common,
1734                         's'          => $common,
1735                         'u'          => $common,
1736
1737                         # 15.2.2
1738                         'font'       => array_merge( $common, [ 'size', 'color', 'face' ] ),
1739                         # basefont
1740
1741                         # 15.3
1742                         'hr'         => array_merge( $common, [ 'width' ] ),
1743
1744                         # HTML Ruby annotation text module, simple ruby only.
1745                         # http://www.whatwg.org/html/text-level-semantics.html#the-ruby-element
1746                         'ruby'       => $common,
1747                         # rbc
1748                         'rb'         => $common,
1749                         'rp'         => $common,
1750                         'rt'         => $common, # array_merge( $common, array( 'rbspan' ) ),
1751                         'rtc'         => $common,
1752
1753                         # MathML root element, where used for extensions
1754                         # 'title' may not be 100% valid here; it's XHTML
1755                         # http://www.w3.org/TR/REC-MathML/
1756                         'math'       => [ 'class', 'style', 'id', 'title' ],
1757
1758                         # HTML 5 section 4.6
1759                         'bdi' => $common,
1760
1761                         # HTML5 elements, defined by:
1762                         # http://www.whatwg.org/html/
1763                         'data' => array_merge( $common, [ 'value' ] ),
1764                         'time' => array_merge( $common, [ 'datetime' ] ),
1765                         'mark' => $common,
1766
1767                         // meta and link are only permitted by removeHTMLtags when Microdata
1768                         // is enabled so we don't bother adding a conditional to hide these
1769                         // Also meta and link are only valid in WikiText as Microdata elements
1770                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1771                         // So we don't bother including $common attributes that have no purpose.
1772                         'meta' => [ 'itemprop', 'content' ],
1773                         'link' => [ 'itemprop', 'href' ],
1774                 ];
1775
1776                 $staticInitialised = $globalContext;
1777
1778                 return $whitelist;
1779         }
1780
1781         /**
1782          * Take a fragment of (potentially invalid) HTML and return
1783          * a version with any tags removed, encoded as plain text.
1784          *
1785          * Warning: this return value must be further escaped for literal
1786          * inclusion in HTML output as of 1.10!
1787          *
1788          * @param string $text HTML fragment
1789          * @return string
1790          */
1791         static function stripAllTags( $text ) {
1792                 # Actual <tags>
1793                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1794
1795                 # Normalize &entities and whitespace
1796                 $text = self::decodeCharReferences( $text );
1797                 $text = self::normalizeWhitespace( $text );
1798
1799                 return $text;
1800         }
1801
1802         /**
1803          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1804          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1805          * PHP 5.1 doesn't.
1806          *
1807          * Use for passing XHTML fragments to PHP's XML parsing functions
1808          *
1809          * @return string
1810          */
1811         static function hackDocType() {
1812                 $out = "<!DOCTYPE html [\n";
1813                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
1814                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1815                 }
1816                 $out .= "]>\n";
1817                 return $out;
1818         }
1819
1820         /**
1821          * @param string $url
1822          * @return mixed|string
1823          */
1824         static function cleanUrl( $url ) {
1825                 # Normalize any HTML entities in input. They will be
1826                 # re-escaped by makeExternalLink().
1827                 $url = Sanitizer::decodeCharReferences( $url );
1828
1829                 # Escape any control characters introduced by the above step
1830                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1831                         [ __CLASS__, 'cleanUrlCallback' ], $url );
1832
1833                 # Validate hostname portion
1834                 $matches = [];
1835                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1836                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1837
1838                         // Characters that will be ignored in IDNs.
1839                         // http://tools.ietf.org/html/3454#section-3.1
1840                         // Strip them before further processing so blacklists and such work.
1841                         $strip = "/
1842                                 \\s|          # general whitespace
1843                                 \xc2\xad|     # 00ad SOFT HYPHEN
1844                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1845                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1846                                 \xe2\x81\xa0| # 2060 WORD JOINER
1847                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1848                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1849                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1850                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1851                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1852                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1853                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1854                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
1855                                 /xuD";
1856
1857                         $host = preg_replace( $strip, '', $host );
1858
1859                         // IPv6 host names are bracketed with [].  Url-decode these.
1860                         if ( substr_compare( "//%5B", $host, 0, 5 ) === 0 &&
1861                                 preg_match( '!^//%5B([0-9A-Fa-f:.]+)%5D((:\d+)?)$!', $host, $matches )
1862                         ) {
1863                                 $host = '//[' . $matches[1] . ']' . $matches[2];
1864                         }
1865
1866                         // @todo FIXME: Validate hostnames here
1867
1868                         return $protocol . $host . $rest;
1869                 } else {
1870                         return $url;
1871                 }
1872         }
1873
1874         /**
1875          * @param array $matches
1876          * @return string
1877          */
1878         static function cleanUrlCallback( $matches ) {
1879                 return urlencode( $matches[0] );
1880         }
1881
1882         /**
1883          * Does a string look like an e-mail address?
1884          *
1885          * This validates an email address using an HTML5 specification found at:
1886          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
1887          * Which as of 2011-01-24 says:
1888          *
1889          *   A valid e-mail address is a string that matches the ABNF production
1890          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1891          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1892          *   3.5.
1893          *
1894          * This function is an implementation of the specification as requested in
1895          * bug 22449.
1896          *
1897          * Client-side forms will use the same standard validation rules via JS or
1898          * HTML 5 validation; additional restrictions can be enforced server-side
1899          * by extensions via the 'isValidEmailAddr' hook.
1900          *
1901          * Note that this validation doesn't 100% match RFC 2822, but is believed
1902          * to be liberal enough for wide use. Some invalid addresses will still
1903          * pass validation here.
1904          *
1905          * @since 1.18
1906          *
1907          * @param string $addr E-mail address
1908          * @return bool
1909          */
1910         public static function validateEmail( $addr ) {
1911                 $result = null;
1912                 if ( !Hooks::run( 'isValidEmailAddr', [ $addr, &$result ] ) ) {
1913                         return $result;
1914                 }
1915
1916                 // Please note strings below are enclosed in brackets [], this make the
1917                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1918                 // See bug 26948
1919                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
1920                 $rfc1034_ldh_str = "a-z0-9\\-";
1921
1922                 $html5_email_regexp = "/
1923                 ^                      # start of string
1924                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1925                 @                      # 'apostrophe'
1926                 [$rfc1034_ldh_str]+       # First domain part
1927                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1928                 $                      # End of string
1929                 /ix"; // case Insensitive, eXtended
1930
1931                 return (bool)preg_match( $html5_email_regexp, $addr );
1932         }
1933 }