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