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 = array(
  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 = array(
 324                 'רלמ' => 'rlm',
 325                 'رلم' => 'rlm',
 326         );
 327
 328         /**
 329          * Lazy-initialised attributes regex, see getAttribsRegex()
 330          */
 331         private static $attribsRegex;
 332
 333         /**
 334          * Regular expression to match HTML/XML attribute pairs within a tag.
 335          * Allows some... latitude.
 336          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 337          * @return string
 338          */
 339         static function getAttribsRegex() {
 340                 if ( self::$attribsRegex === null ) {
 341                         $attribFirst = '[:A-Z_a-z0-9]';
 342                         $attrib = '[:A-Z_a-z-.0-9]';
 343                         $space = '[\x09\x0a\x0d\x20]';
 344                         self::$attribsRegex =
 345                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 346                                   ($space*=$space*
 347                                         (?:
 348                                          # The attribute value: quoted or alone
 349                                           \"([^<\"]*)(?:\"|\$)
 350                                          | '([^<']*)(?:'|\$)
 351                                          |  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)
 352                                         )
 353                                 )?(?=$space|\$)/sx";
 354                 }
 355                 return self::$attribsRegex;
 356         }
 357
 358         /**
 359          * Return the various lists of recognized tags
 360          * @param array $extratags For any extra tags to include
 361          * @param array $removetags For any tags (default or extra) to exclude
 362          * @return array
 363          */
 364         public static function getRecognizedTagData( $extratags = array(), $removetags = array() ) {
 365                 global $wgAllowMicrodataAttributes, $wgAllowImageTag;
 366
 367                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 368                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 369
 370                 // Base our staticInitialised variable off of the global config state so that if the globals
 371                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 372                 $globalContext = implode( '-', compact( 'wgAllowMicrodataAttributes', 'wgAllowImageTag' ) );
 373                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 374                         $htmlpairsStatic = array( # Tags that must be closed
 375                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 376                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 377                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 378                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 379                                 'ruby', 'rb', 'rp', 'rt', 'rtc', 'p', 'span', 'abbr', 'dfn',
 380                                 'kbd', 'samp', 'data', 'time', 'mark'
 381                         );
 382                         $htmlsingle = array(
 383                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd'
 384                         );
 385                         $htmlsingleonly = array( # Elements that cannot have close tags
 386                                 'br', 'wbr', 'hr'
 387                         );
 388                         if ( $wgAllowMicrodataAttributes ) {
 389                                 $htmlsingle[] = $htmlsingleonly[] = 'meta';
 390                                 $htmlsingle[] = $htmlsingleonly[] = 'link';
 391                         }
 392                         $htmlnest = array( # Tags that can be nested--??
 393                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 394                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 395                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 396                         );
 397                         $tabletags = array( # Can only appear inside table, we will close them
 398                                 'td', 'th', 'tr',
 399                         );
 400                         $htmllist = array( # Tags used by list
 401                                 'ul', 'ol',
 402                         );
 403                         $listtags = array( # Tags that can appear in a list
 404                                 'li',
 405                         );
 406
 407                         if ( $wgAllowImageTag ) {
 408                                 $htmlsingle[] = 'img';
 409                                 $htmlsingleonly[] = 'img';
 410                         }
 411
 412                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 413                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 414
 415                         # Convert them all to hashtables for faster lookup
 416                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 417                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 418                         foreach ( $vars as $var ) {
 419                                 $$var = array_flip( $$var );
 420                         }
 421                         $staticInitialised = $globalContext;
 422                 }
 423
 424                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 425                 $extratags = array_flip( $extratags );
 426                 $removetags = array_flip( $removetags );
 427                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 428                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 429
 430                 return array(
 431                         'htmlpairs' => $htmlpairs,
 432                         'htmlsingle' => $htmlsingle,
 433                         'htmlsingleonly' => $htmlsingleonly,
 434                         'htmlnest' => $htmlnest,
 435                         'tabletags' => $tabletags,
 436                         'htmllist' => $htmllist,
 437                         'listtags' => $listtags,
 438                         'htmlsingleallowed' => $htmlsingleallowed,
 439                         'htmlelements' => $htmlelements,
 440                 );
 441         }
 442
 443         /**
 444          * Cleans up HTML, removes dangerous tags and attributes, and
 445          * removes HTML comments
 446          * @param string $text
 447          * @param callable $processCallback Callback to do any variable or parameter
 448          *   replacements in HTML attribute values
 449          * @param array|bool $args Arguments for the processing callback
 450          * @param array $extratags For any extra tags to include
 451          * @param array $removetags For any tags (default or extra) to exclude
 452          * @return string
 453          */
 454         public static function removeHTMLtags( $text, $processCallback = null,
 455                 $args = array(), $extratags = array(), $removetags = array()
 456         ) {
 457                 extract( self::getRecognizedTagData( $extratags, $removetags ) );
 458
 459                 # Remove HTML comments
 460                 $text = Sanitizer::removeHTMLcomments( $text );
 461                 $bits = explode( '<', $text );
 462                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 463                 if ( !MWTidy::isEnabled() ) {
 464                         $tagstack = $tablestack = array();
 465                         foreach ( $bits as $x ) {
 466                                 $regs = array();
 467                                 # $slash: Does the current element start with a '/'?
 468                                 # $t: Current element name
 469                                 # $params: String between element name and >
 470                                 # $brace: Ending '>' or '/>'
 471                                 # $rest: Everything until the next element of $bits
 472                                 if ( preg_match( self::ELEMENT_BITS_REGEX, $x, $regs ) ) {
 473                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 474                                 } else {
 475                                         $slash = $t = $params = $brace = $rest = null;
 476                                 }
 477
 478                                 $badtag = false;
 479                                 $t = strtolower( $t );
 480                                 if ( isset( $htmlelements[$t] ) ) {
 481                                         # Check our stack
 482                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 483                                                 $badtag = true;
 484                                         } elseif ( $slash ) {
 485                                                 # Closing a tag... is it the one we just opened?
 486                                                 MediaWiki\suppressWarnings();
 487                                                 $ot = array_pop( $tagstack );
 488                                                 MediaWiki\restoreWarnings();
 489
 490                                                 if ( $ot != $t ) {
 491                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 492                                                                 # Pop all elements with an optional close tag
 493                                                                 # and see if we find a match below them
 494                                                                 $optstack = array();
 495                                                                 array_push( $optstack, $ot );
 496                                                                 MediaWiki\suppressWarnings();
 497                                                                 $ot = array_pop( $tagstack );
 498                                                                 MediaWiki\restoreWarnings();
 499                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 500                                                                         array_push( $optstack, $ot );
 501                                                                         MediaWiki\suppressWarnings();
 502                                                                         $ot = array_pop( $tagstack );
 503                                                                         MediaWiki\restoreWarnings();
 504                                                                 }
 505                                                                 if ( $t != $ot ) {
 506                                                                         # No match. Push the optional elements back again
 507                                                                         $badtag = true;
 508                                                                         MediaWiki\suppressWarnings();
 509                                                                         $ot = array_pop( $optstack );
 510                                                                         MediaWiki\restoreWarnings();
 511                                                                         while ( $ot ) {
 512                                                                                 array_push( $tagstack, $ot );
 513                                                                                 MediaWiki\suppressWarnings();
 514                                                                                 $ot = array_pop( $optstack );
 515                                                                                 MediaWiki\restoreWarnings();
 516                                                                         }
 517                                                                 }
 518                                                         } else {
 519                                                                 MediaWiki\suppressWarnings();
 520                                                                 array_push( $tagstack, $ot );
 521                                                                 MediaWiki\restoreWarnings();
 522
 523                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 524                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 525                                                                         $badtag = true;
 526                                                                 }
 527                                                         }
 528                                                 } else {
 529                                                         if ( $t == 'table' ) {
 530                                                                 $tagstack = array_pop( $tablestack );
 531                                                         }
 532                                                 }
 533                                                 $newparams = '';
 534                                         } else {
 535                                                 # Keep track for later
 536                                                 if ( isset( $tabletags[$t] ) && !in_array( 'table', $tagstack ) ) {
 537                                                         $badtag = true;
 538                                                 } elseif ( in_array( $t, $tagstack ) && !isset( $htmlnest[$t] ) ) {
 539                                                         $badtag = true;
 540                                                 #  Is it a self closed htmlpair ? (bug 5487)
 541                                                 } elseif ( $brace == '/>' && isset( $htmlpairs[$t] ) ) {
 542                                                         $badtag = true;
 543                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 544                                                         # Hack to force empty tag for unclosable elements
 545                                                         $brace = '/>';
 546                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 547                                                         # Hack to not close $htmlsingle tags
 548                                                         $brace = null;
 549                                                         # Still need to push this optionally-closed tag to
 550                                                         # the tag stack so that we can match end tags
 551                                                         # instead of marking them as bad.
 552                                                         array_push( $tagstack, $t );
 553                                                 } elseif ( isset( $tabletags[$t] ) && in_array( $t, $tagstack ) ) {
 554                                                         // New table tag but forgot to close the previous one
 555                                                         $text .= "</$t>";
 556                                                 } else {
 557                                                         if ( $t == 'table' ) {
 558                                                                 array_push( $tablestack, $tagstack );
 559                                                                 $tagstack = array();
 560                                                         }
 561                                                         array_push( $tagstack, $t );
 562                                                 }
 563
 564                                                 # Replace any variables or template parameters with
 565                                                 # plaintext results.
 566                                                 if ( is_callable( $processCallback ) ) {
 567                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 568                                                 }
 569
 570                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 571                                                         $badtag = true;
 572                                                 }
 573
 574                                                 # Strip non-approved attributes from the tag
 575                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 576                                         }
 577                                         if ( !$badtag ) {
 578                                                 $rest = str_replace( '>', '&gt;', $rest );
 579                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 580                                                 $text .= "<$slash$t$newparams$close>$rest";
 581                                                 continue;
 582                                         }
 583                                 }
 584                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 585                         }
 586                         # Close off any remaining tags
 587                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 588                                 $text .= "</$t>\n";
 589                                 if ( $t == 'table' ) {
 590                                         $tagstack = array_pop( $tablestack );
 591                                 }
 592                         }
 593                 } else {
 594                         # this might be possible using tidy itself
 595                         foreach ( $bits as $x ) {
 596                                 if ( preg_match( self::ELEMENT_BITS_REGEX, $x, $regs ) ) {
 597                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 598
 599                                         $badtag = false;
 600                                         $t = strtolower( $t );
 601                                         if ( isset( $htmlelements[$t] ) ) {
 602                                                 if ( is_callable( $processCallback ) ) {
 603                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 604                                                 }
 605
 606                                                 if ( !Sanitizer::validateTag( $params, $t ) ) {
 607                                                         $badtag = true;
 608                                                 }
 609
 610                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 611                                                 if ( !$badtag ) {
 612                                                         $rest = str_replace( '>', '&gt;', $rest );
 613                                                         $text .= "<$slash$t$newparams$brace$rest";
 614                                                         continue;
 615                                                 }
 616                                         }
 617                                 }
 618                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 619                         }
 620                 }
 621                 return $text;
 622         }
 623
 624         /**
 625          * Remove '<!--', '-->', and everything between.
 626          * To avoid leaving blank lines, when a comment is both preceded
 627          * and followed by a newline (ignoring spaces), trim leading and
 628          * trailing spaces and one of the newlines.
 629          *
 630          * @param string $text
 631          * @return string
 632          */
 633         public static function removeHTMLcomments( $text ) {
 634                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 635                         $end = strpos( $text, '-->', $start + 4 );
 636                         if ( $end === false ) {
 637                                 # Unterminated comment; bail out
 638                                 break;
 639                         }
 640
 641                         $end += 3;
 642
 643                         # Trim space and newline if the comment is both
 644                         # preceded and followed by a newline
 645                         $spaceStart = max( $start - 1, 0 );
 646                         $spaceLen = $end - $spaceStart;
 647                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 648                                 $spaceStart--;
 649                                 $spaceLen++;
 650                         }
 651                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 652                                 $spaceLen++;
 653                         }
 654                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 655                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 656                                 # Remove the comment, leading and trailing
 657                                 # spaces, and leave only one newline.
 658                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 659                         } else {
 660                                 # Remove just the comment.
 661                                 $text = substr_replace( $text, '', $start, $end - $start );
 662                         }
 663                 }
 664                 return $text;
 665         }
 666
 667         /**
 668          * Takes attribute names and values for a tag and the tag name and
 669          * validates that the tag is allowed to be present.
 670          * This DOES NOT validate the attributes, nor does it validate the
 671          * tags themselves. This method only handles the special circumstances
 672          * where we may want to allow a tag within content but ONLY when it has
 673          * specific attributes set.
 674          *
 675          * @param string $params
 676          * @param string $element
 677          * @return bool
 678          */
 679         static function validateTag( $params, $element ) {
 680                 $params = Sanitizer::decodeTagAttributes( $params );
 681
 682                 if ( $element == 'meta' || $element == 'link' ) {
 683                         if ( !isset( $params['itemprop'] ) ) {
 684                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 685                                 return false;
 686                         }
 687                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 688                                 // <meta> must have a content="" for the itemprop
 689                                 return false;
 690                         }
 691                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 692                                 // <link> must have an associated href=""
 693                                 return false;
 694                         }
 695                 }
 696
 697                 return true;
 698         }
 699
 700         /**
 701          * Take an array of attribute names and values and normalize or discard
 702          * illegal values for the given element type.
 703          *
 704          * - Discards attributes not on a whitelist for the given element
 705          * - Unsafe style attributes are discarded
 706          * - Invalid id attributes are re-encoded
 707          *
 708          * @param array $attribs
 709          * @param string $element
 710          * @return array
 711          *
 712          * @todo Check for legal values where the DTD limits things.
 713          * @todo Check for unique id attribute :P
 714          */
 715         static function validateTagAttributes( $attribs, $element ) {
 716                 return Sanitizer::validateAttributes( $attribs,
 717                         Sanitizer::attributeWhitelist( $element ) );
 718         }
 719
 720         /**
 721          * Take an array of attribute names and values and normalize or discard
 722          * illegal values for the given whitelist.
 723          *
 724          * - Discards attributes not the given whitelist
 725          * - Unsafe style attributes are discarded
 726          * - Invalid id attributes are re-encoded
 727          *
 728          * @param array $attribs
 729          * @param array $whitelist List of allowed attribute names
 730          * @return array
 731          *
 732          * @todo Check for legal values where the DTD limits things.
 733          * @todo Check for unique id attribute :P
 734          */
 735         static function validateAttributes( $attribs, $whitelist ) {
 736                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 737
 738                 $whitelist = array_flip( $whitelist );
 739                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 740
 741                 $out = array();
 742                 foreach ( $attribs as $attribute => $value ) {
 743                         # allow XML namespace declaration if RDFa is enabled
 744                         if ( $wgAllowRdfaAttributes && preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 745                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 746                                         $out[$attribute] = $value;
 747                                 }
 748
 749                                 continue;
 750                         }
 751
 752                         # Allow any attribute beginning with "data-"
 753                         # However:
 754                         # * data-ooui is reserved for ooui
 755                         # * data-mw and data-parsoid are reserved for parsoid
 756                         # * data-mw-<name here> is reserved for extensions (or core) if
 757                         #   they need to communicate some data to the client and want to be
 758                         #   sure that it isn't coming from an untrusted user.
 759                         # * Ensure that the attribute is not namespaced by banning
 760                         #   colons.
 761                         if ( !preg_match( '/^data-(?!ooui|mw|parsoid)[^:]*$/i', $attribute )
 762                                 && !isset( $whitelist[$attribute] )
 763                         ) {
 764                                 continue;
 765                         }
 766
 767                         # Strip javascript "expression" from stylesheets.
 768                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 769                         if ( $attribute == 'style' ) {
 770                                 $value = Sanitizer::checkCss( $value );
 771                         }
 772
 773                         if ( $attribute === 'id' ) {
 774                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 775                         }
 776
 777                         # WAI-ARIA
 778                         # http://www.w3.org/TR/wai-aria/
 779                         # http://www.whatwg.org/html/elements.html#wai-aria
 780                         # For now we only support role="presentation" until we work out what roles should be
 781                         # usable by content and we ensure that our code explicitly rejects patterns that
 782                         # violate HTML5's ARIA restrictions.
 783                         if ( $attribute === 'role' && $value !== 'presentation' ) {
 784                                 continue;
 785                         }
 786
 787                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 788                         // Check them for sanity.
 789                         if ( $attribute === 'rel' || $attribute === 'rev'
 790                                 # RDFa
 791                                 || $attribute === 'about' || $attribute === 'property'
 792                                 || $attribute === 'resource' || $attribute === 'datatype'
 793                                 || $attribute === 'typeof'
 794                                 # HTML5 microdata
 795                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 796                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 797                                 || $attribute === 'itemtype'
 798                         ) {
 799                                 // Paranoia. Allow "simple" values but suppress javascript
 800                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 801                                         continue;
 802                                 }
 803                         }
 804
 805                         # NOTE: even though elements using href/src are not allowed directly, supply
 806                         #       validation code that can be used by tag hook handlers, etc
 807                         if ( $attribute === 'href' || $attribute === 'src' ) {
 808                                 if ( !preg_match( $hrefExp, $value ) ) {
 809                                         continue; // drop any href or src attributes not using an allowed protocol.
 810                                         // NOTE: this also drops all relative URLs
 811                                 }
 812                         }
 813
 814                         // If this attribute was previously set, override it.
 815                         // Output should only have one attribute of each name.
 816                         $out[$attribute] = $value;
 817                 }
 818
 819                 if ( $wgAllowMicrodataAttributes ) {
 820                         # itemtype, itemid, itemref don't make sense without itemscope
 821                         if ( !array_key_exists( 'itemscope', $out ) ) {
 822                                 unset( $out['itemtype'] );
 823                                 unset( $out['itemid'] );
 824                                 unset( $out['itemref'] );
 825                         }
 826                         # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 827                 }
 828                 return $out;
 829         }
 830
 831         /**
 832          * Merge two sets of HTML attributes.  Conflicting items in the second set
 833          * will override those in the first, except for 'class' attributes which
 834          * will be combined (if they're both strings).
 835          *
 836          * @todo implement merging for other attributes such as style
 837          * @param array $a
 838          * @param array $b
 839          * @return array
 840          */
 841         static function mergeAttributes( $a, $b ) {
 842                 $out = array_merge( $a, $b );
 843                 if ( isset( $a['class'] ) && isset( $b['class'] )
 844                         && is_string( $a['class'] ) && is_string( $b['class'] )
 845                         && $a['class'] !== $b['class']
 846                 ) {
 847                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 848                                 -1, PREG_SPLIT_NO_EMPTY );
 849                         $out['class'] = implode( ' ', array_unique( $classes ) );
 850                 }
 851                 return $out;
 852         }
 853
 854         /**
 855          * Normalize CSS into a format we can easily search for hostile input
 856          *  - decode character references
 857          *  - decode escape sequences
 858          *  - convert characters that IE6 interprets into ascii
 859          *  - remove comments, unless the entire value is one single comment
 860          * @param string $value the css string
 861          * @return string normalized css
 862          */
 863         public static function normalizeCss( $value ) {
 864
 865                 // Decode character references like &#123;
 866                 $value = Sanitizer::decodeCharReferences( $value );
 867
 868                 // Decode escape sequences and line continuation
 869                 // See the grammar in the CSS 2 spec, appendix D.
 870                 // This has to be done AFTER decoding character references.
 871                 // This means it isn't possible for this function to return
 872                 // unsanitized escape sequences. It is possible to manufacture
 873                 // input that contains character references that decode to
 874                 // escape sequences that decode to character references, but
 875                 // it's OK for the return value to contain character references
 876                 // because the caller is supposed to escape those anyway.
 877                 static $decodeRegex;
 878                 if ( !$decodeRegex ) {
 879                         $space = '[\\x20\\t\\r\\n\\f]';
 880                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 881                         $backslash = '\\\\';
 882                         $decodeRegex = "/ $backslash
 883                                 (?:
 884                                         ($nl) |  # 1. Line continuation
 885                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 886                                         (.) | # 3. backslash cancelling special meaning
 887                                         () | # 4. backslash at end of string
 888                                 )/xu";
 889                 }
 890                 $value = preg_replace_callback( $decodeRegex,
 891                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 892
 893                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 894                 $value = preg_replace_callback(
 895                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (bug 58088)
 896                         function ( $matches ) {
 897                                 $cp = UtfNormal\Utils::utf8ToCodepoint( $matches[0] );
 898                                 if ( $cp === false ) {
 899                                         return '';
 900                                 }
 901                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 902                         },
 903                         $value
 904                 );
 905
 906                 // Convert more characters IE6 might treat as ascii
 907                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 908                 $value = str_replace(
 909                         array( 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ),
 910                         array( 'r', 'n', 'n', 'l', 'i', '(', '(' ),
 911                         $value
 912                 );
 913
 914                 // Let the value through if it's nothing but a single comment, to
 915                 // allow other functions which may reject it to pass some error
 916                 // message through.
 917                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 918                         // Remove any comments; IE gets token splitting wrong
 919                         // This must be done AFTER decoding character references and
 920                         // escape sequences, because those steps can introduce comments
 921                         // This step cannot introduce character references or escape
 922                         // sequences, because it replaces comments with spaces rather
 923                         // than removing them completely.
 924                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 925
 926                         // Remove anything after a comment-start token, to guard against
 927                         // incorrect client implementations.
 928                         $commentPos = strpos( $value, '/*' );
 929                         if ( $commentPos !== false ) {
 930                                 $value = substr( $value, 0, $commentPos );
 931                         }
 932                 }
 933
 934                 // S followed by repeat, iteration, or prolonged sound marks,
 935                 // which IE will treat as "ss"
 936                 $value = preg_replace(
 937                         '/s(?:
 938                                 \xE3\x80\xB1 | # U+3031
 939                                 \xE3\x82\x9D | # U+309D
 940                                 \xE3\x83\xBC | # U+30FC
 941                                 \xE3\x83\xBD | # U+30FD
 942                                 \xEF\xB9\xBC | # U+FE7C
 943                                 \xEF\xB9\xBD | # U+FE7D
 944                                 \xEF\xBD\xB0   # U+FF70
 945                         )/ix',
 946                         'ss',
 947                         $value
 948                 );
 949
 950                 return $value;
 951         }
 952
 953         /**
 954          * Pick apart some CSS and check it for forbidden or unsafe structures.
 955          * Returns a sanitized string. This sanitized string will have
 956          * character references and escape sequences decoded and comments
 957          * stripped (unless it is itself one valid comment, in which case the value
 958          * will be passed through). If the input is just too evil, only a comment
 959          * complaining about evilness will be returned.
 960          *
 961          * Currently URL references, 'expression', 'tps' are forbidden.
 962          *
 963          * NOTE: Despite the fact that character references are decoded, the
 964          * returned string may contain character references given certain
 965          * clever input strings. These character references must
 966          * be escaped before the return value is embedded in HTML.
 967          *
 968          * @param string $value
 969          * @return string
 970          */
 971         static function checkCss( $value ) {
 972                 $value = self::normalizeCss( $value );
 973
 974                 // Reject problematic keywords and control characters
 975                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ||
 976                         strpos( $value, UtfNormal\Constants::UTF8_REPLACEMENT ) !== false ) {
 977                         return '/* invalid control char */';
 978                 } elseif ( preg_match(
 979                         '! expression
 980                                 | filter\s*:
 981                                 | accelerator\s*:
 982                                 | -o-link\s*:
 983                                 | -o-link-source\s*:
 984                                 | -o-replace\s*:
 985                                 | url\s*\(
 986                                 | image\s*\(
 987                                 | image-set\s*\(
 988                         !ix', $value ) ) {
 989                         return '/* insecure input */';
 990                 }
 991                 return $value;
 992         }
 993
 994         /**
 995          * @param array $matches
 996          * @return string
 997          */
 998         static function cssDecodeCallback( $matches ) {
 999                 if ( $matches[1] !== '' ) {
1000                         // Line continuation
1001                         return '';
1002                 } elseif ( $matches[2] !== '' ) {
1003                         $char = UtfNormal\Utils::codepointToUtf8( hexdec( $matches[2] ) );
1004                 } elseif ( $matches[3] !== '' ) {
1005                         $char = $matches[3];
1006                 } else {
1007                         $char = '\\';
1008                 }
1009                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
1010                         // These characters need to be escaped in strings
1011                         // Clean up the escape sequence to avoid parsing errors by clients
1012                         return '\\' . dechex( ord( $char ) ) . ' ';
1013                 } else {
1014                         // Decode unnecessary escape
1015                         return $char;
1016                 }
1017         }
1018
1019         /**
1020          * Take a tag soup fragment listing an HTML element's attributes
1021          * and normalize it to well-formed XML, discarding unwanted attributes.
1022          * Output is safe for further wikitext processing, with escaping of
1023          * values that could trigger problems.
1024          *
1025          * - Normalizes attribute names to lowercase
1026          * - Discards attributes not on a whitelist for the given element
1027          * - Turns broken or invalid entities into plaintext
1028          * - Double-quotes all attribute values
1029          * - Attributes without values are given the name as attribute
1030          * - Double attributes are discarded
1031          * - Unsafe style attributes are discarded
1032          * - Prepends space if there are attributes.
1033          *
1034          * @param string $text
1035          * @param string $element
1036          * @return string
1037          */
1038         static function fixTagAttributes( $text, $element ) {
1039                 if ( trim( $text ) == '' ) {
1040                         return '';
1041                 }
1042
1043                 $decoded = Sanitizer::decodeTagAttributes( $text );
1044                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
1045
1046                 return Sanitizer::safeEncodeTagAttributes( $stripped );
1047         }
1048
1049         /**
1050          * Encode an attribute value for HTML output.
1051          * @param string $text
1052          * @return string HTML-encoded text fragment
1053          */
1054         static function encodeAttribute( $text ) {
1055                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1056
1057                 // Whitespace is normalized during attribute decoding,
1058                 // so if we've been passed non-spaces we must encode them
1059                 // ahead of time or they won't be preserved.
1060                 $encValue = strtr( $encValue, array(
1061                         "\n" => '&#10;',
1062                         "\r" => '&#13;',
1063                         "\t" => '&#9;',
1064                 ) );
1065
1066                 return $encValue;
1067         }
1068
1069         /**
1070          * Encode an attribute value for HTML tags, with extra armoring
1071          * against further wiki processing.
1072          * @param string $text
1073          * @return string HTML-encoded text fragment
1074          */
1075         static function safeEncodeAttribute( $text ) {
1076                 $encValue = Sanitizer::encodeAttribute( $text );
1077
1078                 # Templates and links may be expanded in later parsing,
1079                 # creating invalid or dangerous output. Suppress this.
1080                 $encValue = strtr( $encValue, array(
1081                         '<'    => '&lt;',   // This should never happen,
1082                         '>'    => '&gt;',   // we've received invalid input
1083                         '"'    => '&quot;', // which should have been escaped.
1084                         '{'    => '&#123;',
1085                         '['    => '&#91;',
1086                         "''"   => '&#39;&#39;',
1087                         'ISBN' => '&#73;SBN',
1088                         'RFC'  => '&#82;FC',
1089                         'PMID' => '&#80;MID',
1090                         '|'    => '&#124;',
1091                         '__'   => '&#95;_',
1092                 ) );
1093
1094                 # Stupid hack
1095                 $encValue = preg_replace_callback(
1096                         '/((?i)' . wfUrlProtocols() . ')/',
1097                         array( 'Sanitizer', 'armorLinksCallback' ),
1098                         $encValue );
1099                 return $encValue;
1100         }
1101
1102         /**
1103          * Given a value, escape it so that it can be used in an id attribute and
1104          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1105          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1106          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1107          * escaped with lots of dots.
1108          *
1109          * To ensure we don't have to bother escaping anything, we also strip ', ",
1110          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1111          * We also strip # because it upsets IE, and % because it could be
1112          * ambiguous if it's part of something that looks like a percent escape
1113          * (which don't work reliably in fragments cross-browser).
1114          *
1115          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
1116          *   in the id and name attributes
1117          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1118          *   the id attribute
1119          * @see http://www.whatwg.org/html/elements.html#the-id-attribute
1120          *   HTML5 definition of id attribute
1121          *
1122          * @param string $id Id to escape
1123          * @param string|array $options String or array of strings (default is array()):
1124          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1125          *       so don't pay attention if the first character isn't valid at the
1126          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1127          *       false.
1128          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1129          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1130          *       anchors and links won't break.
1131          * @return string
1132          */
1133         static function escapeId( $id, $options = array() ) {
1134                 global $wgExperimentalHtmlIds;
1135                 $options = (array)$options;
1136
1137                 $id = Sanitizer::decodeCharReferences( $id );
1138
1139                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1140                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1141                         $id = trim( $id, '_' );
1142                         if ( $id === '' ) {
1143                                 // Must have been all whitespace to start with.
1144                                 return '_';
1145                         } else {
1146                                 return $id;
1147                         }
1148                 }
1149
1150                 // HTML4-style escaping
1151                 static $replace = array(
1152                         '%3A' => ':',
1153                         '%' => '.'
1154                 );
1155
1156                 $id = urlencode( strtr( $id, ' ', '_' ) );
1157                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1158
1159                 if ( !preg_match( '/^[a-zA-Z]/', $id ) && !in_array( 'noninitial', $options ) ) {
1160                         // Initial character must be a letter!
1161                         $id = "x$id";
1162                 }
1163                 return $id;
1164         }
1165
1166         /**
1167          * Given a value, escape it so that it can be used as a CSS class and
1168          * return it.
1169          *
1170          * @todo For extra validity, input should be validated UTF-8.
1171          *
1172          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1173          *
1174          * @param string $class
1175          * @return string
1176          */
1177         static function escapeClass( $class ) {
1178                 // Convert ugly stuff to underscores and kill underscores in ugly places
1179                 return rtrim( preg_replace(
1180                         array( '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ),
1181                         '_',
1182                         $class ), '_' );
1183         }
1184
1185         /**
1186          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1187          * This allows (generally harmless) entities like &#160; to survive.
1188          *
1189          * @param string $html HTML to escape
1190          * @return string Escaped input
1191          */
1192         static function escapeHtmlAllowEntities( $html ) {
1193                 $html = Sanitizer::decodeCharReferences( $html );
1194                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1195                 # hurt.
1196                 $html = htmlspecialchars( $html, ENT_QUOTES );
1197                 return $html;
1198         }
1199
1200         /**
1201          * Regex replace callback for armoring links against further processing.
1202          * @param array $matches
1203          * @return string
1204          */
1205         private static function armorLinksCallback( $matches ) {
1206                 return str_replace( ':', '&#58;', $matches[1] );
1207         }
1208
1209         /**
1210          * Return an associative array of attribute names and values from
1211          * a partial tag string. Attribute names are forces to lowercase,
1212          * character references are decoded to UTF-8 text.
1213          *
1214          * @param string $text
1215          * @return array
1216          */
1217         public static function decodeTagAttributes( $text ) {
1218                 if ( trim( $text ) == '' ) {
1219                         return array();
1220                 }
1221
1222                 $attribs = array();
1223                 $pairs = array();
1224                 if ( !preg_match_all(
1225                         self::getAttribsRegex(),
1226                         $text,
1227                         $pairs,
1228                         PREG_SET_ORDER ) ) {
1229                         return $attribs;
1230                 }
1231
1232                 foreach ( $pairs as $set ) {
1233                         $attribute = strtolower( $set[1] );
1234                         $value = Sanitizer::getTagAttributeCallback( $set );
1235
1236                         // Normalize whitespace
1237                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1238                         $value = trim( $value );
1239
1240                         // Decode character references
1241                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1242                 }
1243                 return $attribs;
1244         }
1245
1246         /**
1247          * Build a partial tag string from an associative array of attribute
1248          * names and values as returned by decodeTagAttributes.
1249          *
1250          * @param array $assoc_array
1251          * @return string
1252          */
1253         public static function safeEncodeTagAttributes( $assoc_array ) {
1254                 $attribs = array();
1255                 foreach ( $assoc_array as $attribute => $value ) {
1256                         $encAttribute = htmlspecialchars( $attribute );
1257                         $encValue = Sanitizer::safeEncodeAttribute( $value );
1258
1259                         $attribs[] = "$encAttribute=\"$encValue\"";
1260                 }
1261                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1262         }
1263
1264         /**
1265          * Pick the appropriate attribute value from a match set from the
1266          * attribs regex matches.
1267          *
1268          * @param array $set
1269          * @throws MWException When tag conditions are not met.
1270          * @return string
1271          */
1272         private static function getTagAttributeCallback( $set ) {
1273                 if ( isset( $set[5] ) ) {
1274                         # No quotes.
1275                         return $set[5];
1276                 } elseif ( isset( $set[4] ) ) {
1277                         # Single-quoted
1278                         return $set[4];
1279                 } elseif ( isset( $set[3] ) ) {
1280                         # Double-quoted
1281                         return $set[3];
1282                 } elseif ( !isset( $set[2] ) ) {
1283                         # In XHTML, attributes must have a value so return an empty string.
1284                         # See "Empty attribute syntax",
1285                         # http://www.w3.org/TR/html5/syntax.html#syntax-attribute-name
1286                         return "";
1287                 } else {
1288                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1289                 }
1290         }
1291
1292         /**
1293          * @param string $text
1294          * @return string
1295          */
1296         private static function normalizeWhitespace( $text ) {
1297                 return preg_replace(
1298                         '/\r\n|[\x20\x0d\x0a\x09]/',
1299                         ' ',
1300                         $text );
1301         }
1302
1303         /**
1304          * Normalizes whitespace in a section name, such as might be returned
1305          * by Parser::stripSectionName(), for use in the id's that are used for
1306          * section links.
1307          *
1308          * @param string $section
1309          * @return string
1310          */
1311         static function normalizeSectionNameWhitespace( $section ) {
1312                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1313         }
1314
1315         /**
1316          * Ensure that any entities and character references are legal
1317          * for XML and XHTML specifically. Any stray bits will be
1318          * &amp;-escaped to result in a valid text fragment.
1319          *
1320          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1321          *   numericized (this way we're well-formed even without a DTD)
1322          * b. any numeric char refs must be legal chars, not invalid or forbidden
1323          * c. use lower cased "&#x", not "&#X"
1324          * d. fix or reject non-valid attributes
1325          *
1326          * @param string $text
1327          * @return string
1328          * @private
1329          */
1330         static function normalizeCharReferences( $text ) {
1331                 return preg_replace_callback(
1332                         self::CHAR_REFS_REGEX,
1333                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1334                         $text );
1335         }
1336
1337         /**
1338          * @param string $matches
1339          * @return string
1340          */
1341         static function normalizeCharReferencesCallback( $matches ) {
1342                 $ret = null;
1343                 if ( $matches[1] != '' ) {
1344                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1345                 } elseif ( $matches[2] != '' ) {
1346                         $ret = Sanitizer::decCharReference( $matches[2] );
1347                 } elseif ( $matches[3] != '' ) {
1348                         $ret = Sanitizer::hexCharReference( $matches[3] );
1349                 }
1350                 if ( is_null( $ret ) ) {
1351                         return htmlspecialchars( $matches[0] );
1352                 } else {
1353                         return $ret;
1354                 }
1355         }
1356
1357         /**
1358          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1359          * return the equivalent numeric entity reference (except for the core &lt;
1360          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1361          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1362          * pseudo-entity source (eg &amp;foo;)
1363          *
1364          * @param string $name
1365          * @return string
1366          */
1367         static function normalizeEntity( $name ) {
1368                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1369                         return '&' . self::$htmlEntityAliases[$name] . ';';
1370                 } elseif ( in_array( $name, array( 'lt', 'gt', 'amp', 'quot' ) ) ) {
1371                         return "&$name;";
1372                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1373                         return '&#' . self::$htmlEntities[$name] . ';';
1374                 } else {
1375                         return "&amp;$name;";
1376                 }
1377         }
1378
1379         /**
1380          * @param int $codepoint
1381          * @return null|string
1382          */
1383         static function decCharReference( $codepoint ) {
1384                 $point = intval( $codepoint );
1385                 if ( Sanitizer::validateCodepoint( $point ) ) {
1386                         return sprintf( '&#%d;', $point );
1387                 } else {
1388                         return null;
1389                 }
1390         }
1391
1392         /**
1393          * @param int $codepoint
1394          * @return null|string
1395          */
1396         static function hexCharReference( $codepoint ) {
1397                 $point = hexdec( $codepoint );
1398                 if ( Sanitizer::validateCodepoint( $point ) ) {
1399                         return sprintf( '&#x%x;', $point );
1400                 } else {
1401                         return null;
1402                 }
1403         }
1404
1405         /**
1406          * Returns true if a given Unicode codepoint is a valid character in
1407          * both HTML5 and XML.
1408          * @param int $codepoint
1409          * @return bool
1410          */
1411         private static function validateCodepoint( $codepoint ) {
1412                 # U+000C is valid in HTML5 but not allowed in XML.
1413                 # U+000D is valid in XML but not allowed in HTML5.
1414                 # U+007F - U+009F are disallowed in HTML5 (control characters).
1415                 return $codepoint == 0x09
1416                         || $codepoint == 0x0a
1417                         || ( $codepoint >= 0x20 && $codepoint <= 0x7e )
1418                         || ( $codepoint >= 0xa0 && $codepoint <= 0xd7ff )
1419                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1420                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1421         }
1422
1423         /**
1424          * Decode any character references, numeric or named entities,
1425          * in the text and return a UTF-8 string.
1426          *
1427          * @param string $text
1428          * @return string
1429          */
1430         public static function decodeCharReferences( $text ) {
1431                 return preg_replace_callback(
1432                         self::CHAR_REFS_REGEX,
1433                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1434                         $text );
1435         }
1436
1437         /**
1438          * Decode any character references, numeric or named entities,
1439          * in the next and normalize the resulting string. (bug 14952)
1440          *
1441          * This is useful for page titles, not for text to be displayed,
1442          * MediaWiki allows HTML entities to escape normalization as a feature.
1443          *
1444          * @param string $text Already normalized, containing entities
1445          * @return string Still normalized, without entities
1446          */
1447         public static function decodeCharReferencesAndNormalize( $text ) {
1448                 global $wgContLang;
1449                 $text = preg_replace_callback(
1450                         self::CHAR_REFS_REGEX,
1451                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1452                         $text, /* limit */ -1, $count );
1453
1454                 if ( $count ) {
1455                         return $wgContLang->normalize( $text );
1456                 } else {
1457                         return $text;
1458                 }
1459         }
1460
1461         /**
1462          * @param string $matches
1463          * @return string
1464          */
1465         static function decodeCharReferencesCallback( $matches ) {
1466                 if ( $matches[1] != '' ) {
1467                         return Sanitizer::decodeEntity( $matches[1] );
1468                 } elseif ( $matches[2] != '' ) {
1469                         return Sanitizer::decodeChar( intval( $matches[2] ) );
1470                 } elseif ( $matches[3] != '' ) {
1471                         return Sanitizer::decodeChar( hexdec( $matches[3] ) );
1472                 }
1473                 # Last case should be an ampersand by itself
1474                 return $matches[0];
1475         }
1476
1477         /**
1478          * Return UTF-8 string for a codepoint if that is a valid
1479          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1480          * @param int $codepoint
1481          * @return string
1482          * @private
1483          */
1484         static function decodeChar( $codepoint ) {
1485                 if ( Sanitizer::validateCodepoint( $codepoint ) ) {
1486                         return UtfNormal\Utils::codepointToUtf8( $codepoint );
1487                 } else {
1488                         return UtfNormal\Constants::UTF8_REPLACEMENT;
1489                 }
1490         }
1491
1492         /**
1493          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1494          * return the UTF-8 encoding of that character. Otherwise, returns
1495          * pseudo-entity source (eg "&foo;")
1496          *
1497          * @param string $name
1498          * @return string
1499          */
1500         static function decodeEntity( $name ) {
1501                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1502                         $name = self::$htmlEntityAliases[$name];
1503                 }
1504                 if ( isset( self::$htmlEntities[$name] ) ) {
1505                         return UtfNormal\Utils::codepointToUtf8( self::$htmlEntities[$name] );
1506                 } else {
1507                         return "&$name;";
1508                 }
1509         }
1510
1511         /**
1512          * Fetch the whitelist of acceptable attributes for a given element name.
1513          *
1514          * @param string $element
1515          * @return array
1516          */
1517         static function attributeWhitelist( $element ) {
1518                 $list = Sanitizer::setupAttributeWhitelist();
1519                 return isset( $list[$element] )
1520                         ? $list[$element]
1521                         : array();
1522         }
1523
1524         /**
1525          * Foreach array key (an allowed HTML element), return an array
1526          * of allowed attributes
1527          * @return array
1528          */
1529         static function setupAttributeWhitelist() {
1530                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
1531                 static $whitelist, $staticInitialised;
1532
1533                 $globalContext = implode( '-', compact( 'wgAllowRdfaAttributes', 'wgAllowMicrodataAttributes' ) );
1534
1535                 if ( $whitelist !== null && $staticInitialised == $globalContext ) {
1536                         return $whitelist;
1537                 }
1538
1539                 $common = array(
1540                         # HTML
1541                         'id',
1542                         'class',
1543                         'style',
1544                         'lang',
1545                         'dir',
1546                         'title',
1547
1548                         # WAI-ARIA
1549                         'role',
1550                 );
1551
1552                 if ( $wgAllowRdfaAttributes ) {
1553                         # RDFa attributes as specified in section 9 of
1554                         # http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1555                         $common = array_merge( $common, array(
1556                                 'about', 'property', 'resource', 'datatype', 'typeof',
1557                         ) );
1558                 }
1559
1560                 if ( $wgAllowMicrodataAttributes ) {
1561                         # add HTML5 microdata tags as specified by
1562                         # http://www.whatwg.org/html/microdata.html#the-microdata-model
1563                         $common = array_merge( $common, array(
1564                                 'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1565                         ) );
1566                 }
1567
1568                 $block = array_merge( $common, array( 'align' ) );
1569                 $tablealign = array( 'align', 'valign' );
1570                 $tablecell = array(
1571                         'abbr',
1572                         'axis',
1573                         'headers',
1574                         'scope',
1575                         'rowspan',
1576                         'colspan',
1577                         'nowrap', # deprecated
1578                         'width', # deprecated
1579                         'height', # deprecated
1580                         'bgcolor', # deprecated
1581                 );
1582
1583                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1584                 # See: http://www.w3.org/TR/html4/
1585                 $whitelist = array(
1586                         # 7.5.4
1587                         'div'        => $block,
1588                         'center'     => $common, # deprecated
1589                         'span'       => $common,
1590
1591                         # 7.5.5
1592                         'h1'         => $block,
1593                         'h2'         => $block,
1594                         'h3'         => $block,
1595                         'h4'         => $block,
1596                         'h5'         => $block,
1597                         'h6'         => $block,
1598
1599                         # 7.5.6
1600                         # address
1601
1602                         # 8.2.4
1603                         'bdo'        => $common,
1604
1605                         # 9.2.1
1606                         'em'         => $common,
1607                         'strong'     => $common,
1608                         'cite'       => $common,
1609                         'dfn'        => $common,
1610                         'code'       => $common,
1611                         'samp'       => $common,
1612                         'kbd'        => $common,
1613                         'var'        => $common,
1614                         'abbr'       => $common,
1615                         # acronym
1616
1617                         # 9.2.2
1618                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1619                         'q'          => array_merge( $common, array( 'cite' ) ),
1620
1621                         # 9.2.3
1622                         'sub'        => $common,
1623                         'sup'        => $common,
1624
1625                         # 9.3.1
1626                         'p'          => $block,
1627
1628                         # 9.3.2
1629                         'br'         => array_merge( $common, array( 'clear' ) ),
1630
1631                         # http://www.whatwg.org/html/text-level-semantics.html#the-wbr-element
1632                         'wbr'        => $common,
1633
1634                         # 9.3.4
1635                         'pre'        => array_merge( $common, array( 'width' ) ),
1636
1637                         # 9.4
1638                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1639                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1640
1641                         # 10.2
1642                         'ul'         => array_merge( $common, array( 'type' ) ),
1643                         'ol'         => array_merge( $common, array( 'type', 'start', 'reversed' ) ),
1644                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1645
1646                         # 10.3
1647                         'dl'         => $common,
1648                         'dd'         => $common,
1649                         'dt'         => $common,
1650
1651                         # 11.2.1
1652                         'table'      => array_merge( $common,
1653                                                                 array( 'summary', 'width', 'border', 'frame',
1654                                                                                 'rules', 'cellspacing', 'cellpadding',
1655                                                                                 'align', 'bgcolor',
1656                                                                 ) ),
1657
1658                         # 11.2.2
1659                         'caption'    => $block,
1660
1661                         # 11.2.3
1662                         'thead'      => $common,
1663                         'tfoot'      => $common,
1664                         'tbody'      => $common,
1665
1666                         # 11.2.4
1667                         'colgroup'   => array_merge( $common, array( 'span' ) ),
1668                         'col'        => array_merge( $common, array( 'span' ) ),
1669
1670                         # 11.2.5
1671                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1672
1673                         # 11.2.6
1674                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1675                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1676
1677                         # 12.2
1678                         # NOTE: <a> is not allowed directly, but the attrib
1679                         # whitelist is used from the Parser object
1680                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1681
1682                         # 13.2
1683                         # Not usually allowed, but may be used for extension-style hooks
1684                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1685                         # true
1686                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1687
1688                         # 15.2.1
1689                         'tt'         => $common,
1690                         'b'          => $common,
1691                         'i'          => $common,
1692                         'big'        => $common,
1693                         'small'      => $common,
1694                         'strike'     => $common,
1695                         's'          => $common,
1696                         'u'          => $common,
1697
1698                         # 15.2.2
1699                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1700                         # basefont
1701
1702                         # 15.3
1703                         'hr'         => array_merge( $common, array( 'width' ) ),
1704
1705                         # HTML Ruby annotation text module, simple ruby only.
1706                         # http://www.whatwg.org/html/text-level-semantics.html#the-ruby-element
1707                         'ruby'       => $common,
1708                         # rbc
1709                         'rb'         => $common,
1710                         'rp'         => $common,
1711                         'rt'         => $common, # array_merge( $common, array( 'rbspan' ) ),
1712                         'rtc'         => $common,
1713
1714                         # MathML root element, where used for extensions
1715                         # 'title' may not be 100% valid here; it's XHTML
1716                         # http://www.w3.org/TR/REC-MathML/
1717                         'math'       => array( 'class', 'style', 'id', 'title' ),
1718
1719                         # HTML 5 section 4.6
1720                         'bdi' => $common,
1721
1722                         # HTML5 elements, defined by:
1723                         # http://www.whatwg.org/html/
1724                         'data' => array_merge( $common, array( 'value' ) ),
1725                         'time' => array_merge( $common, array( 'datetime' ) ),
1726                         'mark' => $common,
1727
1728                         // meta and link are only permitted by removeHTMLtags when Microdata
1729                         // is enabled so we don't bother adding a conditional to hide these
1730                         // Also meta and link are only valid in WikiText as Microdata elements
1731                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1732                         // So we don't bother including $common attributes that have no purpose.
1733                         'meta' => array( 'itemprop', 'content' ),
1734                         'link' => array( 'itemprop', 'href' ),
1735                 );
1736
1737                 $staticInitialised = $globalContext;
1738
1739                 return $whitelist;
1740         }
1741
1742         /**
1743          * Take a fragment of (potentially invalid) HTML and return
1744          * a version with any tags removed, encoded as plain text.
1745          *
1746          * Warning: this return value must be further escaped for literal
1747          * inclusion in HTML output as of 1.10!
1748          *
1749          * @param string $text HTML fragment
1750          * @return string
1751          */
1752         static function stripAllTags( $text ) {
1753                 # Actual <tags>
1754                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1755
1756                 # Normalize &entities and whitespace
1757                 $text = self::decodeCharReferences( $text );
1758                 $text = self::normalizeWhitespace( $text );
1759
1760                 return $text;
1761         }
1762
1763         /**
1764          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1765          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1766          * PHP 5.1 doesn't.
1767          *
1768          * Use for passing XHTML fragments to PHP's XML parsing functions
1769          *
1770          * @return string
1771          */
1772         static function hackDocType() {
1773                 $out = "<!DOCTYPE html [\n";
1774                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
1775                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1776                 }
1777                 $out .= "]>\n";
1778                 return $out;
1779         }
1780
1781         /**
1782          * @param string $url
1783          * @return mixed|string
1784          */
1785         static function cleanUrl( $url ) {
1786                 # Normalize any HTML entities in input. They will be
1787                 # re-escaped by makeExternalLink().
1788                 $url = Sanitizer::decodeCharReferences( $url );
1789
1790                 # Escape any control characters introduced by the above step
1791                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
1792                         array( __CLASS__, 'cleanUrlCallback' ), $url );
1793
1794                 # Validate hostname portion
1795                 $matches = array();
1796                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1797                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1798
1799                         // Characters that will be ignored in IDNs.
1800                         // http://tools.ietf.org/html/3454#section-3.1
1801                         // Strip them before further processing so blacklists and such work.
1802                         $strip = "/
1803                                 \\s|          # general whitespace
1804                                 \xc2\xad|     # 00ad SOFT HYPHEN
1805                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1806                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1807                                 \xe2\x81\xa0| # 2060 WORD JOINER
1808                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1809                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1810                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1811                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1812                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1813                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1814                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1815                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
1816                                 /xuD";
1817
1818                         $host = preg_replace( $strip, '', $host );
1819
1820                         // IPv6 host names are bracketed with [].  Url-decode these.
1821                         if ( substr_compare( "//%5B", $host, 0, 5 ) === 0 &&
1822                                 preg_match( '!^//%5B([0-9A-Fa-f:.]+)%5D((:\d+)?)$!', $host, $matches )
1823                         ) {
1824                                 $host = '//[' . $matches[1] . ']' . $matches[2];
1825                         }
1826
1827                         // @todo FIXME: Validate hostnames here
1828
1829                         return $protocol . $host . $rest;
1830                 } else {
1831                         return $url;
1832                 }
1833         }
1834
1835         /**
1836          * @param array $matches
1837          * @return string
1838          */
1839         static function cleanUrlCallback( $matches ) {
1840                 return urlencode( $matches[0] );
1841         }
1842
1843         /**
1844          * Does a string look like an e-mail address?
1845          *
1846          * This validates an email address using an HTML5 specification found at:
1847          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
1848          * Which as of 2011-01-24 says:
1849          *
1850          *   A valid e-mail address is a string that matches the ABNF production
1851          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
1852          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
1853          *   3.5.
1854          *
1855          * This function is an implementation of the specification as requested in
1856          * bug 22449.
1857          *
1858          * Client-side forms will use the same standard validation rules via JS or
1859          * HTML 5 validation; additional restrictions can be enforced server-side
1860          * by extensions via the 'isValidEmailAddr' hook.
1861          *
1862          * Note that this validation doesn't 100% match RFC 2822, but is believed
1863          * to be liberal enough for wide use. Some invalid addresses will still
1864          * pass validation here.
1865          *
1866          * @since 1.18
1867          *
1868          * @param string $addr E-mail address
1869          * @return bool
1870          */
1871         public static function validateEmail( $addr ) {
1872                 $result = null;
1873                 if ( !Hooks::run( 'isValidEmailAddr', array( $addr, &$result ) ) ) {
1874                         return $result;
1875                 }
1876
1877                 // Please note strings below are enclosed in brackets [], this make the
1878                 // hyphen "-" a range indicator. Hence it is double backslashed below.
1879                 // See bug 26948
1880                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
1881                 $rfc1034_ldh_str = "a-z0-9\\-";
1882
1883                 $html5_email_regexp = "/
1884                 ^                      # start of string
1885                 [$rfc5322_atext\\.]+    # user part which is liberal :p
1886                 @                      # 'apostrophe'
1887                 [$rfc1034_ldh_str]+       # First domain part
1888                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
1889                 $                      # End of string
1890                 /ix"; // case Insensitive, eXtended
1891
1892                 return (bool)preg_match( $html5_email_regexp, $addr );
1893         }
1894 }