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          * https://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          * Tells escapeUrlForHtml() to encode the ID using the wiki's primary encoding.
  61          *
  62          * @since 1.30
  63          */
  64         const ID_PRIMARY = 0;
  65
  66         /**
  67          * Tells escapeUrlForHtml() to encode the ID using the fallback encoding, or return false
  68          * if no fallback is configured.
  69          *
  70          * @since 1.30
  71          */
  72         const ID_FALLBACK = 1;
  73
  74         /**
  75          * List of all named character entities defined in HTML 4.01
  76          * https://www.w3.org/TR/html4/sgml/entities.html
  77          * As well as &apos; which is only defined starting in XHTML1.
  78          */
  79         private static $htmlEntities = [
  80                 'Aacute'   => 193,
  81                 'aacute'   => 225,
  82                 'Acirc'    => 194,
  83                 'acirc'    => 226,
  84                 'acute'    => 180,
  85                 'AElig'    => 198,
  86                 'aelig'    => 230,
  87                 'Agrave'   => 192,
  88                 'agrave'   => 224,
  89                 'alefsym'  => 8501,
  90                 'Alpha'    => 913,
  91                 'alpha'    => 945,
  92                 'amp'      => 38,
  93                 'and'      => 8743,
  94                 'ang'      => 8736,
  95                 'apos'     => 39, // New in XHTML & HTML 5; avoid in output for compatibility with IE.
  96                 'Aring'    => 197,
  97                 'aring'    => 229,
  98                 'asymp'    => 8776,
  99                 'Atilde'   => 195,
 100                 'atilde'   => 227,
 101                 'Auml'     => 196,
 102                 'auml'     => 228,
 103                 'bdquo'    => 8222,
 104                 'Beta'     => 914,
 105                 'beta'     => 946,
 106                 'brvbar'   => 166,
 107                 'bull'     => 8226,
 108                 'cap'      => 8745,
 109                 'Ccedil'   => 199,
 110                 'ccedil'   => 231,
 111                 'cedil'    => 184,
 112                 'cent'     => 162,
 113                 'Chi'      => 935,
 114                 'chi'      => 967,
 115                 'circ'     => 710,
 116                 'clubs'    => 9827,
 117                 'cong'     => 8773,
 118                 'copy'     => 169,
 119                 'crarr'    => 8629,
 120                 'cup'      => 8746,
 121                 'curren'   => 164,
 122                 'dagger'   => 8224,
 123                 'Dagger'   => 8225,
 124                 'darr'     => 8595,
 125                 'dArr'     => 8659,
 126                 'deg'      => 176,
 127                 'Delta'    => 916,
 128                 'delta'    => 948,
 129                 'diams'    => 9830,
 130                 'divide'   => 247,
 131                 'Eacute'   => 201,
 132                 'eacute'   => 233,
 133                 'Ecirc'    => 202,
 134                 'ecirc'    => 234,
 135                 'Egrave'   => 200,
 136                 'egrave'   => 232,
 137                 'empty'    => 8709,
 138                 'emsp'     => 8195,
 139                 'ensp'     => 8194,
 140                 'Epsilon'  => 917,
 141                 'epsilon'  => 949,
 142                 'equiv'    => 8801,
 143                 'Eta'      => 919,
 144                 'eta'      => 951,
 145                 'ETH'      => 208,
 146                 'eth'      => 240,
 147                 'Euml'     => 203,
 148                 'euml'     => 235,
 149                 'euro'     => 8364,
 150                 'exist'    => 8707,
 151                 'fnof'     => 402,
 152                 'forall'   => 8704,
 153                 'frac12'   => 189,
 154                 'frac14'   => 188,
 155                 'frac34'   => 190,
 156                 'frasl'    => 8260,
 157                 'Gamma'    => 915,
 158                 'gamma'    => 947,
 159                 'ge'       => 8805,
 160                 'gt'       => 62,
 161                 'harr'     => 8596,
 162                 'hArr'     => 8660,
 163                 'hearts'   => 9829,
 164                 'hellip'   => 8230,
 165                 'Iacute'   => 205,
 166                 'iacute'   => 237,
 167                 'Icirc'    => 206,
 168                 'icirc'    => 238,
 169                 'iexcl'    => 161,
 170                 'Igrave'   => 204,
 171                 'igrave'   => 236,
 172                 'image'    => 8465,
 173                 'infin'    => 8734,
 174                 'int'      => 8747,
 175                 'Iota'     => 921,
 176                 'iota'     => 953,
 177                 'iquest'   => 191,
 178                 'isin'     => 8712,
 179                 'Iuml'     => 207,
 180                 'iuml'     => 239,
 181                 'Kappa'    => 922,
 182                 'kappa'    => 954,
 183                 'Lambda'   => 923,
 184                 'lambda'   => 955,
 185                 'lang'     => 9001,
 186                 'laquo'    => 171,
 187                 'larr'     => 8592,
 188                 'lArr'     => 8656,
 189                 'lceil'    => 8968,
 190                 'ldquo'    => 8220,
 191                 'le'       => 8804,
 192                 'lfloor'   => 8970,
 193                 'lowast'   => 8727,
 194                 'loz'      => 9674,
 195                 'lrm'      => 8206,
 196                 'lsaquo'   => 8249,
 197                 'lsquo'    => 8216,
 198                 'lt'       => 60,
 199                 'macr'     => 175,
 200                 'mdash'    => 8212,
 201                 'micro'    => 181,
 202                 'middot'   => 183,
 203                 'minus'    => 8722,
 204                 'Mu'       => 924,
 205                 'mu'       => 956,
 206                 'nabla'    => 8711,
 207                 'nbsp'     => 160,
 208                 'ndash'    => 8211,
 209                 'ne'       => 8800,
 210                 'ni'       => 8715,
 211                 'not'      => 172,
 212                 'notin'    => 8713,
 213                 'nsub'     => 8836,
 214                 'Ntilde'   => 209,
 215                 'ntilde'   => 241,
 216                 'Nu'       => 925,
 217                 'nu'       => 957,
 218                 'Oacute'   => 211,
 219                 'oacute'   => 243,
 220                 'Ocirc'    => 212,
 221                 'ocirc'    => 244,
 222                 'OElig'    => 338,
 223                 'oelig'    => 339,
 224                 'Ograve'   => 210,
 225                 'ograve'   => 242,
 226                 'oline'    => 8254,
 227                 'Omega'    => 937,
 228                 'omega'    => 969,
 229                 'Omicron'  => 927,
 230                 'omicron'  => 959,
 231                 'oplus'    => 8853,
 232                 'or'       => 8744,
 233                 'ordf'     => 170,
 234                 'ordm'     => 186,
 235                 'Oslash'   => 216,
 236                 'oslash'   => 248,
 237                 'Otilde'   => 213,
 238                 'otilde'   => 245,
 239                 'otimes'   => 8855,
 240                 'Ouml'     => 214,
 241                 'ouml'     => 246,
 242                 'para'     => 182,
 243                 'part'     => 8706,
 244                 'permil'   => 8240,
 245                 'perp'     => 8869,
 246                 'Phi'      => 934,
 247                 'phi'      => 966,
 248                 'Pi'       => 928,
 249                 'pi'       => 960,
 250                 'piv'      => 982,
 251                 'plusmn'   => 177,
 252                 'pound'    => 163,
 253                 'prime'    => 8242,
 254                 'Prime'    => 8243,
 255                 'prod'     => 8719,
 256                 'prop'     => 8733,
 257                 'Psi'      => 936,
 258                 'psi'      => 968,
 259                 'quot'     => 34,
 260                 'radic'    => 8730,
 261                 'rang'     => 9002,
 262                 'raquo'    => 187,
 263                 'rarr'     => 8594,
 264                 'rArr'     => 8658,
 265                 'rceil'    => 8969,
 266                 'rdquo'    => 8221,
 267                 'real'     => 8476,
 268                 'reg'      => 174,
 269                 'rfloor'   => 8971,
 270                 'Rho'      => 929,
 271                 'rho'      => 961,
 272                 'rlm'      => 8207,
 273                 'rsaquo'   => 8250,
 274                 'rsquo'    => 8217,
 275                 'sbquo'    => 8218,
 276                 'Scaron'   => 352,
 277                 'scaron'   => 353,
 278                 'sdot'     => 8901,
 279                 'sect'     => 167,
 280                 'shy'      => 173,
 281                 'Sigma'    => 931,
 282                 'sigma'    => 963,
 283                 'sigmaf'   => 962,
 284                 'sim'      => 8764,
 285                 'spades'   => 9824,
 286                 'sub'      => 8834,
 287                 'sube'     => 8838,
 288                 'sum'      => 8721,
 289                 'sup'      => 8835,
 290                 'sup1'     => 185,
 291                 'sup2'     => 178,
 292                 'sup3'     => 179,
 293                 'supe'     => 8839,
 294                 'szlig'    => 223,
 295                 'Tau'      => 932,
 296                 'tau'      => 964,
 297                 'there4'   => 8756,
 298                 'Theta'    => 920,
 299                 'theta'    => 952,
 300                 'thetasym' => 977,
 301                 'thinsp'   => 8201,
 302                 'THORN'    => 222,
 303                 'thorn'    => 254,
 304                 'tilde'    => 732,
 305                 'times'    => 215,
 306                 'trade'    => 8482,
 307                 'Uacute'   => 218,
 308                 'uacute'   => 250,
 309                 'uarr'     => 8593,
 310                 'uArr'     => 8657,
 311                 'Ucirc'    => 219,
 312                 'ucirc'    => 251,
 313                 'Ugrave'   => 217,
 314                 'ugrave'   => 249,
 315                 'uml'      => 168,
 316                 'upsih'    => 978,
 317                 'Upsilon'  => 933,
 318                 'upsilon'  => 965,
 319                 'Uuml'     => 220,
 320                 'uuml'     => 252,
 321                 'weierp'   => 8472,
 322                 'Xi'       => 926,
 323                 'xi'       => 958,
 324                 'Yacute'   => 221,
 325                 'yacute'   => 253,
 326                 'yen'      => 165,
 327                 'Yuml'     => 376,
 328                 'yuml'     => 255,
 329                 'Zeta'     => 918,
 330                 'zeta'     => 950,
 331                 'zwj'      => 8205,
 332                 'zwnj'     => 8204
 333         ];
 334
 335         /**
 336          * Character entity aliases accepted by MediaWiki
 337          */
 338         private static $htmlEntityAliases = [
 339                 'רלמ' => 'rlm',
 340                 'رلم' => 'rlm',
 341         ];
 342
 343         /**
 344          * Lazy-initialised attributes regex, see getAttribsRegex()
 345          */
 346         private static $attribsRegex;
 347
 348         /**
 349          * Regular expression to match HTML/XML attribute pairs within a tag.
 350          * Allows some... latitude. Based on,
 351          * https://www.w3.org/TR/html5/syntax.html#before-attribute-value-state
 352          * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
 353          * @return string
 354          */
 355         static function getAttribsRegex() {
 356                 if ( self::$attribsRegex === null ) {
 357                         $attribFirst = "[:_\p{L}\p{N}]";
 358                         $attrib = "[:_\.\-\p{L}\p{N}]";
 359                         $space = '[\x09\x0a\x0c\x0d\x20]';
 360                         self::$attribsRegex =
 361                                 "/(?:^|$space)({$attribFirst}{$attrib}*)
 362                                         ($space*=$space*
 363                                         (?:
 364                                                 # The attribute value: quoted or alone
 365                                                 \"([^\"]*)(?:\"|\$)
 366                                                 | '([^']*)(?:'|\$)
 367                                                 | (((?!$space|>).)*)
 368                                         )
 369                                 )?(?=$space|\$)/sxu";
 370                 }
 371                 return self::$attribsRegex;
 372         }
 373
 374         /**
 375          * Return the various lists of recognized tags
 376          * @param array $extratags For any extra tags to include
 377          * @param array $removetags For any tags (default or extra) to exclude
 378          * @return array
 379          */
 380         public static function getRecognizedTagData( $extratags = [], $removetags = [] ) {
 381                 global $wgAllowImageTag;
 382
 383                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 384                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 385
 386                 // Base our staticInitialised variable off of the global config state so that if the globals
 387                 // are changed (like in the screwed up test system) we will re-initialise the settings.
 388                 $globalContext = $wgAllowImageTag;
 389                 if ( !$staticInitialised || $staticInitialised != $globalContext ) {
 390                         $htmlpairsStatic = [ # Tags that must be closed
 391                                 'b', 'bdi', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 392                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 393                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 394                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 395                                 'ruby', 'rb', 'rp', 'rt', 'rtc', 'p', 'span', 'abbr', 'dfn',
 396                                 'kbd', 'samp', 'data', 'time', 'mark'
 397                         ];
 398                         $htmlsingle = [
 399                                 'br', 'wbr', 'hr', 'li', 'dt', 'dd', 'meta', 'link'
 400                         ];
 401
 402                         # Elements that cannot have close tags. This is (not coincidentally)
 403                         # also the list of tags for which the HTML 5 parsing algorithm
 404                         # requires you to "acknowledge the token's self-closing flag", i.e.
 405                         # a self-closing tag like <br/> is not an HTML 5 parse error only
 406                         # for this list.
 407                         $htmlsingleonly = [
 408                                 'br', 'wbr', 'hr', 'meta', 'link'
 409                         ];
 410
 411                         $htmlnest = [ # Tags that can be nested--??
 412                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 413                                 'li', 'dl', 'dt', 'dd', 'font', 'big', 'small', 'sub', 'sup', 'span',
 414                                 'var', 'kbd', 'samp', 'em', 'strong', 'q', 'ruby', 'bdo'
 415                         ];
 416                         $tabletags = [ # Can only appear inside table, we will close them
 417                                 'td', 'th', 'tr',
 418                         ];
 419                         $htmllist = [ # Tags used by list
 420                                 'ul', 'ol',
 421                         ];
 422                         $listtags = [ # Tags that can appear in a list
 423                                 'li',
 424                         ];
 425
 426                         if ( $wgAllowImageTag ) {
 427                                 $htmlsingle[] = 'img';
 428                                 $htmlsingleonly[] = 'img';
 429                         }
 430
 431                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 432                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 433
 434                         # Convert them all to hashtables for faster lookup
 435                         $vars = [ 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 436                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' ];
 437                         foreach ( $vars as $var ) {
 438                                 $$var = array_flip( $$var );
 439                         }
 440                         $staticInitialised = $globalContext;
 441                 }
 442
 443                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 444                 $extratags = array_flip( $extratags );
 445                 $removetags = array_flip( $removetags );
 446                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 447                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ), $removetags );
 448
 449                 return [
 450                         'htmlpairs' => $htmlpairs,
 451                         'htmlsingle' => $htmlsingle,
 452                         'htmlsingleonly' => $htmlsingleonly,
 453                         'htmlnest' => $htmlnest,
 454                         'tabletags' => $tabletags,
 455                         'htmllist' => $htmllist,
 456                         'listtags' => $listtags,
 457                         'htmlsingleallowed' => $htmlsingleallowed,
 458                         'htmlelements' => $htmlelements,
 459                 ];
 460         }
 461
 462         /**
 463          * Cleans up HTML, removes dangerous tags and attributes, and
 464          * removes HTML comments
 465          * @param string $text
 466          * @param callable $processCallback Callback to do any variable or parameter
 467          *   replacements in HTML attribute values
 468          * @param array|bool $args Arguments for the processing callback
 469          * @param array $extratags For any extra tags to include
 470          * @param array $removetags For any tags (default or extra) to exclude
 471          * @param callable $warnCallback (Deprecated) Callback allowing the
 472          *   addition of a tracking category when bad input is encountered.
 473          *   DO NOT ADD NEW PARAMETERS AFTER $warnCallback, since it will be
 474          *   removed shortly.
 475          * @return string
 476          */
 477         public static function removeHTMLtags( $text, $processCallback = null,
 478                 $args = [], $extratags = [], $removetags = [], $warnCallback = null
 479         ) {
 480                 extract( self::getRecognizedTagData( $extratags, $removetags ) );
 481
 482                 # Remove HTML comments
 483                 $text = self::removeHTMLcomments( $text );
 484                 $bits = explode( '<', $text );
 485                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 486                 if ( !MWTidy::isEnabled() ) {
 487                         $tagstack = $tablestack = [];
 488                         foreach ( $bits as $x ) {
 489                                 $regs = [];
 490                                 # $slash: Does the current element start with a '/'?
 491                                 # $t: Current element name
 492                                 # $params: String between element name and >
 493                                 # $brace: Ending '>' or '/>'
 494                                 # $rest: Everything until the next element of $bits
 495                                 if ( preg_match( self::ELEMENT_BITS_REGEX, $x, $regs ) ) {
 496                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 497                                 } else {
 498                                         $slash = $t = $params = $brace = $rest = null;
 499                                 }
 500
 501                                 $badtag = false;
 502                                 $t = strtolower( $t );
 503                                 if ( isset( $htmlelements[$t] ) ) {
 504                                         # Check our stack
 505                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 506                                                 $badtag = true;
 507                                         } elseif ( $slash ) {
 508                                                 # Closing a tag... is it the one we just opened?
 509                                                 MediaWiki\suppressWarnings();
 510                                                 $ot = array_pop( $tagstack );
 511                                                 MediaWiki\restoreWarnings();
 512
 513                                                 if ( $ot != $t ) {
 514                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 515                                                                 # Pop all elements with an optional close tag
 516                                                                 # and see if we find a match below them
 517                                                                 $optstack = [];
 518                                                                 array_push( $optstack, $ot );
 519                                                                 MediaWiki\suppressWarnings();
 520                                                                 $ot = array_pop( $tagstack );
 521                                                                 MediaWiki\restoreWarnings();
 522                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 523                                                                         array_push( $optstack, $ot );
 524                                                                         MediaWiki\suppressWarnings();
 525                                                                         $ot = array_pop( $tagstack );
 526                                                                         MediaWiki\restoreWarnings();
 527                                                                 }
 528                                                                 if ( $t != $ot ) {
 529                                                                         # No match. Push the optional elements back again
 530                                                                         $badtag = true;
 531                                                                         MediaWiki\suppressWarnings();
 532                                                                         $ot = array_pop( $optstack );
 533                                                                         MediaWiki\restoreWarnings();
 534                                                                         while ( $ot ) {
 535                                                                                 array_push( $tagstack, $ot );
 536                                                                                 MediaWiki\suppressWarnings();
 537                                                                                 $ot = array_pop( $optstack );
 538                                                                                 MediaWiki\restoreWarnings();
 539                                                                         }
 540                                                                 }
 541                                                         } else {
 542                                                                 MediaWiki\suppressWarnings();
 543                                                                 array_push( $tagstack, $ot );
 544                                                                 MediaWiki\restoreWarnings();
 545
 546                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 547                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 548                                                                         $badtag = true;
 549                                                                 }
 550                                                         }
 551                                                 } else {
 552                                                         if ( $t == 'table' ) {
 553                                                                 $tagstack = array_pop( $tablestack );
 554                                                         }
 555                                                 }
 556                                                 $newparams = '';
 557                                         } else {
 558                                                 # Keep track for later
 559                                                 if ( isset( $tabletags[$t] ) && !in_array( 'table', $tagstack ) ) {
 560                                                         $badtag = true;
 561                                                 } elseif ( in_array( $t, $tagstack ) && !isset( $htmlnest[$t] ) ) {
 562                                                         $badtag = true;
 563                                                 #  Is it a self closed htmlpair ? (T7487)
 564                                                 } elseif ( $brace == '/>' && isset( $htmlpairs[$t] ) ) {
 565                                                         // Eventually we'll just remove the self-closing
 566                                                         // slash, in order to be consistent with HTML5
 567                                                         // semantics.
 568                                                         // $brace = '>';
 569                                                         // For now, let's just warn authors to clean up.
 570                                                         if ( is_callable( $warnCallback ) ) {
 571                                                                 call_user_func_array( $warnCallback, [ 'deprecated-self-close-category' ] );
 572                                                         }
 573                                                         $badtag = true;
 574                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 575                                                         # Hack to force empty tag for unclosable elements
 576                                                         $brace = '/>';
 577                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 578                                                         # Hack to not close $htmlsingle tags
 579                                                         $brace = null;
 580                                                         # Still need to push this optionally-closed tag to
 581                                                         # the tag stack so that we can match end tags
 582                                                         # instead of marking them as bad.
 583                                                         array_push( $tagstack, $t );
 584                                                 } elseif ( isset( $tabletags[$t] ) && in_array( $t, $tagstack ) ) {
 585                                                         // New table tag but forgot to close the previous one
 586                                                         $text .= "</$t>";
 587                                                 } else {
 588                                                         if ( $t == 'table' ) {
 589                                                                 array_push( $tablestack, $tagstack );
 590                                                                 $tagstack = [];
 591                                                         }
 592                                                         array_push( $tagstack, $t );
 593                                                 }
 594
 595                                                 # Replace any variables or template parameters with
 596                                                 # plaintext results.
 597                                                 if ( is_callable( $processCallback ) ) {
 598                                                         call_user_func_array( $processCallback, [ &$params, $args ] );
 599                                                 }
 600
 601                                                 if ( !self::validateTag( $params, $t ) ) {
 602                                                         $badtag = true;
 603                                                 }
 604
 605                                                 # Strip non-approved attributes from the tag
 606                                                 $newparams = self::fixTagAttributes( $params, $t );
 607                                         }
 608                                         if ( !$badtag ) {
 609                                                 $rest = str_replace( '>', '&gt;', $rest );
 610                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 611                                                 $text .= "<$slash$t$newparams$close>$rest";
 612                                                 continue;
 613                                         }
 614                                 }
 615                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 616                         }
 617                         # Close off any remaining tags
 618                         while ( is_array( $tagstack ) && ( $t = array_pop( $tagstack ) ) ) {
 619                                 $text .= "</$t>\n";
 620                                 if ( $t == 'table' ) {
 621                                         $tagstack = array_pop( $tablestack );
 622                                 }
 623                         }
 624                 } else {
 625                         # this might be possible using tidy itself
 626                         foreach ( $bits as $x ) {
 627                                 if ( preg_match( self::ELEMENT_BITS_REGEX, $x, $regs ) ) {
 628                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 629
 630                                         $badtag = false;
 631                                         $t = strtolower( $t );
 632                                         if ( isset( $htmlelements[$t] ) ) {
 633                                                 if ( is_callable( $processCallback ) ) {
 634                                                         call_user_func_array( $processCallback, [ &$params, $args ] );
 635                                                 }
 636
 637                                                 if ( $brace == '/>' && !( isset( $htmlsingle[$t] ) || isset( $htmlsingleonly[$t] ) ) ) {
 638                                                         // Eventually we'll just remove the self-closing
 639                                                         // slash, in order to be consistent with HTML5
 640                                                         // semantics.
 641                                                         // $brace = '>';
 642                                                         // For now, let's just warn authors to clean up.
 643                                                         if ( is_callable( $warnCallback ) ) {
 644                                                                 call_user_func_array( $warnCallback, [ 'deprecated-self-close-category' ] );
 645                                                         }
 646                                                 }
 647                                                 if ( !self::validateTag( $params, $t ) ) {
 648                                                         $badtag = true;
 649                                                 }
 650
 651                                                 $newparams = self::fixTagAttributes( $params, $t );
 652                                                 if ( !$badtag ) {
 653                                                         if ( $brace === '/>' && !isset( $htmlsingleonly[$t] ) ) {
 654                                                                 # Interpret self-closing tags as empty tags even when
 655                                                                 # HTML 5 would interpret them as start tags. Such input
 656                                                                 # is commonly seen on Wikimedia wikis with this intention.
 657                                                                 $brace = "></$t>";
 658                                                         }
 659
 660                                                         $rest = str_replace( '>', '&gt;', $rest );
 661                                                         $text .= "<$slash$t$newparams$brace$rest";
 662                                                         continue;
 663                                                 }
 664                                         }
 665                                 }
 666                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x );
 667                         }
 668                 }
 669                 return $text;
 670         }
 671
 672         /**
 673          * Remove '<!--', '-->', and everything between.
 674          * To avoid leaving blank lines, when a comment is both preceded
 675          * and followed by a newline (ignoring spaces), trim leading and
 676          * trailing spaces and one of the newlines.
 677          *
 678          * @param string $text
 679          * @return string
 680          */
 681         public static function removeHTMLcomments( $text ) {
 682                 while ( ( $start = strpos( $text, '<!--' ) ) !== false ) {
 683                         $end = strpos( $text, '-->', $start + 4 );
 684                         if ( $end === false ) {
 685                                 # Unterminated comment; bail out
 686                                 break;
 687                         }
 688
 689                         $end += 3;
 690
 691                         # Trim space and newline if the comment is both
 692                         # preceded and followed by a newline
 693                         $spaceStart = max( $start - 1, 0 );
 694                         $spaceLen = $end - $spaceStart;
 695                         while ( substr( $text, $spaceStart, 1 ) === ' ' && $spaceStart > 0 ) {
 696                                 $spaceStart--;
 697                                 $spaceLen++;
 698                         }
 699                         while ( substr( $text, $spaceStart + $spaceLen, 1 ) === ' ' ) {
 700                                 $spaceLen++;
 701                         }
 702                         if ( substr( $text, $spaceStart, 1 ) === "\n"
 703                                 && substr( $text, $spaceStart + $spaceLen, 1 ) === "\n" ) {
 704                                 # Remove the comment, leading and trailing
 705                                 # spaces, and leave only one newline.
 706                                 $text = substr_replace( $text, "\n", $spaceStart, $spaceLen + 1 );
 707                         } else {
 708                                 # Remove just the comment.
 709                                 $text = substr_replace( $text, '', $start, $end - $start );
 710                         }
 711                 }
 712                 return $text;
 713         }
 714
 715         /**
 716          * Takes attribute names and values for a tag and the tag name and
 717          * validates that the tag is allowed to be present.
 718          * This DOES NOT validate the attributes, nor does it validate the
 719          * tags themselves. This method only handles the special circumstances
 720          * where we may want to allow a tag within content but ONLY when it has
 721          * specific attributes set.
 722          *
 723          * @param string $params
 724          * @param string $element
 725          * @return bool
 726          */
 727         static function validateTag( $params, $element ) {
 728                 $params = self::decodeTagAttributes( $params );
 729
 730                 if ( $element == 'meta' || $element == 'link' ) {
 731                         if ( !isset( $params['itemprop'] ) ) {
 732                                 // <meta> and <link> must have an itemprop="" otherwise they are not valid or safe in content
 733                                 return false;
 734                         }
 735                         if ( $element == 'meta' && !isset( $params['content'] ) ) {
 736                                 // <meta> must have a content="" for the itemprop
 737                                 return false;
 738                         }
 739                         if ( $element == 'link' && !isset( $params['href'] ) ) {
 740                                 // <link> must have an associated href=""
 741                                 return false;
 742                         }
 743                 }
 744
 745                 return true;
 746         }
 747
 748         /**
 749          * Take an array of attribute names and values and normalize or discard
 750          * illegal values for the given element type.
 751          *
 752          * - Discards attributes not on a whitelist for the given element
 753          * - Unsafe style attributes are discarded
 754          * - Invalid id attributes are re-encoded
 755          *
 756          * @param array $attribs
 757          * @param string $element
 758          * @return array
 759          *
 760          * @todo Check for legal values where the DTD limits things.
 761          * @todo Check for unique id attribute :P
 762          */
 763         static function validateTagAttributes( $attribs, $element ) {
 764                 return self::validateAttributes( $attribs,
 765                         self::attributeWhitelist( $element ) );
 766         }
 767
 768         /**
 769          * Take an array of attribute names and values and normalize or discard
 770          * illegal values for the given whitelist.
 771          *
 772          * - Discards attributes not on the given whitelist
 773          * - Unsafe style attributes are discarded
 774          * - Invalid id attributes are re-encoded
 775          *
 776          * @param array $attribs
 777          * @param array $whitelist List of allowed attribute names
 778          * @return array
 779          *
 780          * @todo Check for legal values where the DTD limits things.
 781          * @todo Check for unique id attribute :P
 782          */
 783         static function validateAttributes( $attribs, $whitelist ) {
 784                 $whitelist = array_flip( $whitelist );
 785                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 786
 787                 $out = [];
 788                 foreach ( $attribs as $attribute => $value ) {
 789                         # Allow XML namespace declaration to allow RDFa
 790                         if ( preg_match( self::XMLNS_ATTRIBUTE_PATTERN, $attribute ) ) {
 791                                 if ( !preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 792                                         $out[$attribute] = $value;
 793                                 }
 794
 795                                 continue;
 796                         }
 797
 798                         # Allow any attribute beginning with "data-"
 799                         # However:
 800                         # * Disallow data attributes used by MediaWiki code
 801                         # * Ensure that the attribute is not namespaced by banning
 802                         #   colons.
 803                         if ( !preg_match( '/^data-[^:]*$/i', $attribute )
 804                                 && !isset( $whitelist[$attribute] )
 805                                 || self::isReservedDataAttribute( $attribute )
 806                         ) {
 807                                 continue;
 808                         }
 809
 810                         # Strip javascript "expression" from stylesheets.
 811                         # https://msdn.microsoft.com/en-us/library/ms537634.aspx
 812                         if ( $attribute == 'style' ) {
 813                                 $value = self::checkCss( $value );
 814                         }
 815
 816                         # Escape HTML id attributes
 817                         if ( $attribute === 'id' ) {
 818                                 $value = self::escapeIdForAttribute( $value, Sanitizer::ID_PRIMARY );
 819                         }
 820
 821                         # Escape HTML id reference lists
 822                         if ( $attribute === 'aria-describedby'
 823                                 || $attribute === 'aria-flowto'
 824                                 || $attribute === 'aria-labelledby'
 825                                 || $attribute === 'aria-owns'
 826                         ) {
 827                                 $value = self::escapeIdReferenceList( $value, 'noninitial' );
 828                         }
 829
 830                         // RDFa and microdata properties allow URLs, URIs and/or CURIs.
 831                         // Check them for sanity.
 832                         if ( $attribute === 'rel' || $attribute === 'rev'
 833                                 # RDFa
 834                                 || $attribute === 'about' || $attribute === 'property'
 835                                 || $attribute === 'resource' || $attribute === 'datatype'
 836                                 || $attribute === 'typeof'
 837                                 # HTML5 microdata
 838                                 || $attribute === 'itemid' || $attribute === 'itemprop'
 839                                 || $attribute === 'itemref' || $attribute === 'itemscope'
 840                                 || $attribute === 'itemtype'
 841                         ) {
 842                                 // Paranoia. Allow "simple" values but suppress javascript
 843                                 if ( preg_match( self::EVIL_URI_PATTERN, $value ) ) {
 844                                         continue;
 845                                 }
 846                         }
 847
 848                         # NOTE: even though elements using href/src are not allowed directly, supply
 849                         #       validation code that can be used by tag hook handlers, etc
 850                         if ( $attribute === 'href' || $attribute === 'src' || $attribute === 'poster' ) {
 851                                 if ( !preg_match( $hrefExp, $value ) ) {
 852                                         continue; // drop any href or src attributes not using an allowed protocol.
 853                                         // NOTE: this also drops all relative URLs
 854                                 }
 855                         }
 856
 857                         // If this attribute was previously set, override it.
 858                         // Output should only have one attribute of each name.
 859                         $out[$attribute] = $value;
 860                 }
 861
 862                 # itemtype, itemid, itemref don't make sense without itemscope
 863                 if ( !array_key_exists( 'itemscope', $out ) ) {
 864                         unset( $out['itemtype'] );
 865                         unset( $out['itemid'] );
 866                         unset( $out['itemref'] );
 867                 }
 868                 # TODO: Strip itemprop if we aren't descendants of an itemscope or pointed to by an itemref.
 869
 870                 return $out;
 871         }
 872
 873         /**
 874          * Given an attribute name, checks whether it is a reserved data attribute
 875          * (such as data-mw-foo) which is unavailable to user-generated HTML so MediaWiki
 876          * core and extension code can safely use it to communicate with frontend code.
 877          * @param string $attr Attribute name.
 878          * @return bool
 879          */
 880         public static function isReservedDataAttribute( $attr ) {
 881                 // data-ooui is reserved for ooui.
 882                 // data-mw and data-parsoid are reserved for parsoid.
 883                 // data-mw-<name here> is reserved for extensions (or core) if
 884                 // they need to communicate some data to the client and want to be
 885                 // sure that it isn't coming from an untrusted user.
 886                 // We ignore the possibility of namespaces since user-generated HTML
 887                 // can't use them anymore.
 888                 return (bool)preg_match( '/^data-(ooui|mw|parsoid)/i', $attr );
 889         }
 890
 891         /**
 892          * Merge two sets of HTML attributes.  Conflicting items in the second set
 893          * will override those in the first, except for 'class' attributes which
 894          * will be combined (if they're both strings).
 895          *
 896          * @todo implement merging for other attributes such as style
 897          * @param array $a
 898          * @param array $b
 899          * @return array
 900          */
 901         static function mergeAttributes( $a, $b ) {
 902                 $out = array_merge( $a, $b );
 903                 if ( isset( $a['class'] ) && isset( $b['class'] )
 904                         && is_string( $a['class'] ) && is_string( $b['class'] )
 905                         && $a['class'] !== $b['class']
 906                 ) {
 907                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 908                                 -1, PREG_SPLIT_NO_EMPTY );
 909                         $out['class'] = implode( ' ', array_unique( $classes ) );
 910                 }
 911                 return $out;
 912         }
 913
 914         /**
 915          * Normalize CSS into a format we can easily search for hostile input
 916          *  - decode character references
 917          *  - decode escape sequences
 918          *  - convert characters that IE6 interprets into ascii
 919          *  - remove comments, unless the entire value is one single comment
 920          * @param string $value the css string
 921          * @return string normalized css
 922          */
 923         public static function normalizeCss( $value ) {
 924                 // Decode character references like &#123;
 925                 $value = self::decodeCharReferences( $value );
 926
 927                 // Decode escape sequences and line continuation
 928                 // See the grammar in the CSS 2 spec, appendix D.
 929                 // This has to be done AFTER decoding character references.
 930                 // This means it isn't possible for this function to return
 931                 // unsanitized escape sequences. It is possible to manufacture
 932                 // input that contains character references that decode to
 933                 // escape sequences that decode to character references, but
 934                 // it's OK for the return value to contain character references
 935                 // because the caller is supposed to escape those anyway.
 936                 static $decodeRegex;
 937                 if ( !$decodeRegex ) {
 938                         $space = '[\\x20\\t\\r\\n\\f]';
 939                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 940                         $backslash = '\\\\';
 941                         $decodeRegex = "/ $backslash
 942                                 (?:
 943                                         ($nl) |  # 1. Line continuation
 944                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 945                                         (.) | # 3. backslash cancelling special meaning
 946                                         () | # 4. backslash at end of string
 947                                 )/xu";
 948                 }
 949                 $value = preg_replace_callback( $decodeRegex,
 950                         [ __CLASS__, 'cssDecodeCallback' ], $value );
 951
 952                 // Normalize Halfwidth and Fullwidth Unicode block that IE6 might treat as ascii
 953                 $value = preg_replace_callback(
 954                         '/[！-［］-ｚ]/u', // U+FF01 to U+FF5A, excluding U+FF3C (T60088)
 955                         function ( $matches ) {
 956                                 $cp = UtfNormal\Utils::utf8ToCodepoint( $matches[0] );
 957                                 if ( $cp === false ) {
 958                                         return '';
 959                                 }
 960                                 return chr( $cp - 65248 ); // ASCII range \x21-\x7A
 961                         },
 962                         $value
 963                 );
 964
 965                 // Convert more characters IE6 might treat as ascii
 966                 // U+0280, U+0274, U+207F, U+029F, U+026A, U+207D, U+208D
 967                 $value = str_replace(
 968                         [ 'ʀ', 'ɴ', 'ⁿ', 'ʟ', 'ɪ', '⁽', '₍' ],
 969                         [ 'r', 'n', 'n', 'l', 'i', '(', '(' ],
 970                         $value
 971                 );
 972
 973                 // Let the value through if it's nothing but a single comment, to
 974                 // allow other functions which may reject it to pass some error
 975                 // message through.
 976                 if ( !preg_match( '! ^ \s* /\* [^*\\/]* \*/ \s* $ !x', $value ) ) {
 977                         // Remove any comments; IE gets token splitting wrong
 978                         // This must be done AFTER decoding character references and
 979                         // escape sequences, because those steps can introduce comments
 980                         // This step cannot introduce character references or escape
 981                         // sequences, because it replaces comments with spaces rather
 982                         // than removing them completely.
 983                         $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 984
 985                         // Remove anything after a comment-start token, to guard against
 986                         // incorrect client implementations.
 987                         $commentPos = strpos( $value, '/*' );
 988                         if ( $commentPos !== false ) {
 989                                 $value = substr( $value, 0, $commentPos );
 990                         }
 991                 }
 992
 993                 // S followed by repeat, iteration, or prolonged sound marks,
 994                 // which IE will treat as "ss"
 995                 $value = preg_replace(
 996                         '/s(?:
 997                                 \xE3\x80\xB1 | # U+3031
 998                                 \xE3\x82\x9D | # U+309D
 999                                 \xE3\x83\xBC | # U+30FC
1000                                 \xE3\x83\xBD | # U+30FD
1001                                 \xEF\xB9\xBC | # U+FE7C
1002                                 \xEF\xB9\xBD | # U+FE7D
1003                                 \xEF\xBD\xB0   # U+FF70
1004                         )/ix',
1005                         'ss',
1006                         $value
1007                 );
1008
1009                 return $value;
1010         }
1011
1012         /**
1013          * Pick apart some CSS and check it for forbidden or unsafe structures.
1014          * Returns a sanitized string. This sanitized string will have
1015          * character references and escape sequences decoded and comments
1016          * stripped (unless it is itself one valid comment, in which case the value
1017          * will be passed through). If the input is just too evil, only a comment
1018          * complaining about evilness will be returned.
1019          *
1020          * Currently URL references, 'expression', 'tps' are forbidden.
1021          *
1022          * NOTE: Despite the fact that character references are decoded, the
1023          * returned string may contain character references given certain
1024          * clever input strings. These character references must
1025          * be escaped before the return value is embedded in HTML.
1026          *
1027          * @param string $value
1028          * @return string
1029          */
1030         static function checkCss( $value ) {
1031                 $value = self::normalizeCss( $value );
1032
1033                 // Reject problematic keywords and control characters
1034                 if ( preg_match( '/[\000-\010\013\016-\037\177]/', $value ) ||
1035                         strpos( $value, UtfNormal\Constants::UTF8_REPLACEMENT ) !== false ) {
1036                         return '/* invalid control char */';
1037                 } elseif ( preg_match(
1038                         '! expression
1039                                 | filter\s*:
1040                                 | accelerator\s*:
1041                                 | -o-link\s*:
1042                                 | -o-link-source\s*:
1043                                 | -o-replace\s*:
1044                                 | url\s*\(
1045                                 | image\s*\(
1046                                 | image-set\s*\(
1047                                 | attr\s*\([^)]+[\s,]+url
1048                         !ix', $value ) ) {
1049                         return '/* insecure input */';
1050                 }
1051                 return $value;
1052         }
1053
1054         /**
1055          * @param array $matches
1056          * @return string
1057          */
1058         static function cssDecodeCallback( $matches ) {
1059                 if ( $matches[1] !== '' ) {
1060                         // Line continuation
1061                         return '';
1062                 } elseif ( $matches[2] !== '' ) {
1063                         $char = UtfNormal\Utils::codepointToUtf8( hexdec( $matches[2] ) );
1064                 } elseif ( $matches[3] !== '' ) {
1065                         $char = $matches[3];
1066                 } else {
1067                         $char = '\\';
1068                 }
1069                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
1070                         // These characters need to be escaped in strings
1071                         // Clean up the escape sequence to avoid parsing errors by clients
1072                         return '\\' . dechex( ord( $char ) ) . ' ';
1073                 } else {
1074                         // Decode unnecessary escape
1075                         return $char;
1076                 }
1077         }
1078
1079         /**
1080          * Take a tag soup fragment listing an HTML element's attributes
1081          * and normalize it to well-formed XML, discarding unwanted attributes.
1082          * Output is safe for further wikitext processing, with escaping of
1083          * values that could trigger problems.
1084          *
1085          * - Normalizes attribute names to lowercase
1086          * - Discards attributes not on a whitelist for the given element
1087          * - Turns broken or invalid entities into plaintext
1088          * - Double-quotes all attribute values
1089          * - Attributes without values are given the name as attribute
1090          * - Double attributes are discarded
1091          * - Unsafe style attributes are discarded
1092          * - Prepends space if there are attributes.
1093          * - (Optionally) Sorts attributes by name.
1094          *
1095          * @param string $text
1096          * @param string $element
1097          * @param bool $sorted Whether to sort the attributes (default: false)
1098          * @return string
1099          */
1100         static function fixTagAttributes( $text, $element, $sorted = false ) {
1101                 if ( trim( $text ) == '' ) {
1102                         return '';
1103                 }
1104
1105                 $decoded = self::decodeTagAttributes( $text );
1106                 $stripped = self::validateTagAttributes( $decoded, $element );
1107
1108                 if ( $sorted ) {
1109                         ksort( $stripped );
1110                 }
1111
1112                 return self::safeEncodeTagAttributes( $stripped );
1113         }
1114
1115         /**
1116          * Encode an attribute value for HTML output.
1117          * @param string $text
1118          * @return string HTML-encoded text fragment
1119          */
1120         static function encodeAttribute( $text ) {
1121                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
1122
1123                 // Whitespace is normalized during attribute decoding,
1124                 // so if we've been passed non-spaces we must encode them
1125                 // ahead of time or they won't be preserved.
1126                 $encValue = strtr( $encValue, [
1127                         "\n" => '&#10;',
1128                         "\r" => '&#13;',
1129                         "\t" => '&#9;',
1130                 ] );
1131
1132                 return $encValue;
1133         }
1134
1135         /**
1136          * Encode an attribute value for HTML tags, with extra armoring
1137          * against further wiki processing.
1138          * @param string $text
1139          * @return string HTML-encoded text fragment
1140          */
1141         static function safeEncodeAttribute( $text ) {
1142                 $encValue = self::encodeAttribute( $text );
1143
1144                 # Templates and links may be expanded in later parsing,
1145                 # creating invalid or dangerous output. Suppress this.
1146                 $encValue = strtr( $encValue, [
1147                         '<'    => '&lt;',   // This should never happen,
1148                         '>'    => '&gt;',   // we've received invalid input
1149                         '"'    => '&quot;', // which should have been escaped.
1150                         '{'    => '&#123;',
1151                         '}'    => '&#125;', // prevent unpaired language conversion syntax
1152                         '['    => '&#91;',
1153                         "''"   => '&#39;&#39;',
1154                         'ISBN' => '&#73;SBN',
1155                         'RFC'  => '&#82;FC',
1156                         'PMID' => '&#80;MID',
1157                         '|'    => '&#124;',
1158                         '__'   => '&#95;_',
1159                 ] );
1160
1161                 # Stupid hack
1162                 $encValue = preg_replace_callback(
1163                         '/((?i)' . wfUrlProtocols() . ')/',
1164                         [ 'Sanitizer', 'armorLinksCallback' ],
1165                         $encValue );
1166                 return $encValue;
1167         }
1168
1169         /**
1170          * Given a value, escape it so that it can be used in an id attribute and
1171          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
1172          * true, allowing anything but ASCII whitespace.  Otherwise it will use
1173          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
1174          * escaped with lots of dots.
1175          *
1176          * To ensure we don't have to bother escaping anything, we also strip ', ",
1177          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
1178          * We also strip # because it upsets IE, and % because it could be
1179          * ambiguous if it's part of something that looks like a percent escape
1180          * (which don't work reliably in fragments cross-browser).
1181          *
1182          * @deprecated since 1.30, use one of this class' escapeIdFor*() functions
1183          *
1184          * @see https://www.w3.org/TR/html401/types.html#type-name Valid characters
1185          *   in the id and name attributes
1186          * @see https://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with
1187          *   the id attribute
1188          * @see https://www.w3.org/TR/html5/dom.html#the-id-attribute
1189          *   HTML5 definition of id attribute
1190          *
1191          * @param string $id Id to escape
1192          * @param string|array $options String or array of strings (default is array()):
1193          *   'noninitial': This is a non-initial fragment of an id, not a full id,
1194          *       so don't pay attention if the first character isn't valid at the
1195          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
1196          *       false.
1197          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
1198          *       if $wgExperimentalHtmlIds is used, so we can generate extra
1199          *       anchors and links won't break.
1200          * @return string
1201          */
1202         static function escapeId( $id, $options = [] ) {
1203                 global $wgExperimentalHtmlIds;
1204                 $options = (array)$options;
1205
1206                 $id = self::decodeCharReferences( $id );
1207
1208                 if ( $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1209                         $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1210                         $id = trim( $id, '_' );
1211                         if ( $id === '' ) {
1212                                 // Must have been all whitespace to start with.
1213                                 return '_';
1214                         } else {
1215                                 return $id;
1216                         }
1217                 }
1218
1219                 // HTML4-style escaping
1220                 static $replace = [
1221                         '%3A' => ':',
1222                         '%' => '.'
1223                 ];
1224
1225                 $id = urlencode( strtr( $id, ' ', '_' ) );
1226                 $id = strtr( $id, $replace );
1227
1228                 if ( !preg_match( '/^[a-zA-Z]/', $id ) && !in_array( 'noninitial', $options ) ) {
1229                         // Initial character must be a letter!
1230                         $id = "x$id";
1231                 }
1232                 return $id;
1233         }
1234
1235         /**
1236          * Given a section name or other user-generated or otherwise unsafe string, escapes it to be
1237          * a valid HTML id attribute.
1238          *
1239          * WARNING: unlike escapeId(), the output of this function is not guaranteed to be HTML safe,
1240          * be sure to use proper escaping.
1241          *
1242          * @param string $id String to escape
1243          * @param int $mode One of ID_* constants, specifying whether the primary or fallback encoding
1244          *     should be used.
1245          * @return string|bool Escaped ID or false if fallback encoding is requested but it's not
1246          *     configured.
1247          *
1248          * @since 1.30
1249          */
1250         public static function escapeIdForAttribute( $id, $mode = self::ID_PRIMARY ) {
1251                 global $wgFragmentMode;
1252
1253                 if ( !isset( $wgFragmentMode[$mode] ) ) {
1254                         if ( $mode === self::ID_PRIMARY ) {
1255                                 throw new UnexpectedValueException( '$wgFragmentMode is configured with no primary mode' );
1256                         }
1257                         return false;
1258                 }
1259
1260                 $internalMode = $wgFragmentMode[$mode];
1261
1262                 return self::escapeIdInternal( $id, $internalMode );
1263         }
1264
1265         /**
1266          * Given a section name or other user-generated or otherwise unsafe string, escapes it to be
1267          * a valid URL fragment.
1268          *
1269          * WARNING: unlike escapeId(), the output of this function is not guaranteed to be HTML safe,
1270          * be sure to use proper escaping.
1271          *
1272          * @param string $id String to escape
1273          * @return string Escaped ID
1274          *
1275          * @since 1.30
1276          */
1277         public static function escapeIdForLink( $id ) {
1278                 global $wgFragmentMode;
1279
1280                 if ( !isset( $wgFragmentMode[self::ID_PRIMARY] ) ) {
1281                         throw new UnexpectedValueException( '$wgFragmentMode is configured with no primary mode' );
1282                 }
1283
1284                 $mode = $wgFragmentMode[self::ID_PRIMARY];
1285
1286                 $id = self::escapeIdInternal( $id, $mode );
1287                 $id = self::urlEscapeId( $id, $mode );
1288
1289                 return $id;
1290         }
1291
1292         /**
1293          * Given a section name or other user-generated or otherwise unsafe string, escapes it to be
1294          * a valid URL fragment for external interwikis.
1295          *
1296          * @param string $id String to escape
1297          * @return string Escaped ID
1298          *
1299          * @since 1.30
1300          */
1301         public static function escapeIdForExternalInterwiki( $id ) {
1302                 global $wgExternalInterwikiFragmentMode;
1303
1304                 $id = self::escapeIdInternal( $id, $wgExternalInterwikiFragmentMode );
1305                 $id = self::urlEscapeId( $id, $wgExternalInterwikiFragmentMode );
1306
1307                 return $id;
1308         }
1309
1310         /**
1311          * Helper for escapeIdFor*() functions. URL-escapes the ID if needed.
1312          *
1313          * @param string $id String to escape
1314          * @param string $mode One of modes from $wgFragmentMode
1315          * @return string
1316          */
1317         private static function urlEscapeId( $id, $mode ) {
1318                 if ( $mode === 'html5' ) {
1319                         $id = urlencode( $id );
1320                         $id = str_replace( '%3A', ':', $id );
1321                 }
1322
1323                 return $id;
1324         }
1325
1326         /**
1327          * Helper for escapeIdFor*() functions. Performs most of the actual escaping.
1328          *
1329          * @param string $id String to escape
1330          * @param string $mode One of modes from $wgFragmentMode
1331          * @return string
1332          */
1333         private static function escapeIdInternal( $id, $mode ) {
1334                 $id = Sanitizer::decodeCharReferences( $id );
1335
1336                 switch ( $mode ) {
1337                         case 'html5':
1338                                 $id = str_replace( ' ', '_', $id );
1339                                 break;
1340                         case 'legacy':
1341                                 // This corresponds to 'noninitial' mode of the old escapeId()
1342                                 static $replace = [
1343                                         '%3A' => ':',
1344                                         '%' => '.'
1345                                 ];
1346
1347                                 $id = urlencode( str_replace( ' ', '_', $id ) );
1348                                 $id = strtr( $id, $replace );
1349                                 break;
1350                         case 'html5-legacy':
1351                                 $id = preg_replace( '/[ \t\n\r\f_\'"&#%]+/', '_', $id );
1352                                 $id = trim( $id, '_' );
1353                                 if ( $id === '' ) {
1354                                         // Must have been all whitespace to start with.
1355                                         $id = '_';
1356                                 }
1357                                 break;
1358                         default:
1359                                 throw new InvalidArgumentException( "Invalid mode '$mode' passed to '" . __METHOD__ );
1360                 }
1361
1362                 return $id;
1363         }
1364
1365         /**
1366          * Given a string containing a space delimited list of ids, escape each id
1367          * to match ids escaped by the escapeId() function.
1368          *
1369          * @todo wfDeprecated() uses of $options in 1.31, remove completely in 1.32
1370          *
1371          * @since 1.27
1372          *
1373          * @param string $referenceString Space delimited list of ids
1374          * @param string|array $options Deprecated and does nothing.
1375          * @return string
1376          */
1377         static function escapeIdReferenceList( $referenceString, $options = [] ) {
1378                 # Explode the space delimited list string into an array of tokens
1379                 $references = preg_split( '/\s+/', "{$referenceString}", -1, PREG_SPLIT_NO_EMPTY );
1380
1381                 # Escape each token as an id
1382                 foreach ( $references as &$ref ) {
1383                         $ref = self::escapeIdForAttribute( $ref );
1384                 }
1385
1386                 # Merge the array back to a space delimited list string
1387                 # If the array is empty, the result will be an empty string ('')
1388                 $referenceString = implode( ' ', $references );
1389
1390                 return $referenceString;
1391         }
1392
1393         /**
1394          * Given a value, escape it so that it can be used as a CSS class and
1395          * return it.
1396          *
1397          * @todo For extra validity, input should be validated UTF-8.
1398          *
1399          * @see https://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1400          *
1401          * @param string $class
1402          * @return string
1403          */
1404         static function escapeClass( $class ) {
1405                 // Convert ugly stuff to underscores and kill underscores in ugly places
1406                 return rtrim( preg_replace(
1407                         [ '/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/', '/_+/' ],
1408                         '_',
1409                         $class ), '_' );
1410         }
1411
1412         /**
1413          * Given HTML input, escape with htmlspecialchars but un-escape entities.
1414          * This allows (generally harmless) entities like &#160; to survive.
1415          *
1416          * @param string $html HTML to escape
1417          * @return string Escaped input
1418          */
1419         static function escapeHtmlAllowEntities( $html ) {
1420                 $html = self::decodeCharReferences( $html );
1421                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1422                 # hurt. Use ENT_SUBSTITUTE so that incorrectly truncated multibyte characters
1423                 # don't cause the entire string to disappear.
1424                 $html = htmlspecialchars( $html, ENT_QUOTES | ENT_SUBSTITUTE );
1425                 return $html;
1426         }
1427
1428         /**
1429          * Regex replace callback for armoring links against further processing.
1430          * @param array $matches
1431          * @return string
1432          */
1433         private static function armorLinksCallback( $matches ) {
1434                 return str_replace( ':', '&#58;', $matches[1] );
1435         }
1436
1437         /**
1438          * Return an associative array of attribute names and values from
1439          * a partial tag string. Attribute names are forced to lowercase,
1440          * character references are decoded to UTF-8 text.
1441          *
1442          * @param string $text
1443          * @return array
1444          */
1445         public static function decodeTagAttributes( $text ) {
1446                 if ( trim( $text ) == '' ) {
1447                         return [];
1448                 }
1449
1450                 $attribs = [];
1451                 $pairs = [];
1452                 if ( !preg_match_all(
1453                         self::getAttribsRegex(),
1454                         $text,
1455                         $pairs,
1456                         PREG_SET_ORDER ) ) {
1457                         return $attribs;
1458                 }
1459
1460                 foreach ( $pairs as $set ) {
1461                         $attribute = strtolower( $set[1] );
1462                         $value = self::getTagAttributeCallback( $set );
1463
1464                         // Normalize whitespace
1465                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1466                         $value = trim( $value );
1467
1468                         // Decode character references
1469                         $attribs[$attribute] = self::decodeCharReferences( $value );
1470                 }
1471                 return $attribs;
1472         }
1473
1474         /**
1475          * Build a partial tag string from an associative array of attribute
1476          * names and values as returned by decodeTagAttributes.
1477          *
1478          * @param array $assoc_array
1479          * @return string
1480          */
1481         public static function safeEncodeTagAttributes( $assoc_array ) {
1482                 $attribs = [];
1483                 foreach ( $assoc_array as $attribute => $value ) {
1484                         $encAttribute = htmlspecialchars( $attribute );
1485                         $encValue = self::safeEncodeAttribute( $value );
1486
1487                         $attribs[] = "$encAttribute=\"$encValue\"";
1488                 }
1489                 return count( $attribs ) ? ' ' . implode( ' ', $attribs ) : '';
1490         }
1491
1492         /**
1493          * Pick the appropriate attribute value from a match set from the
1494          * attribs regex matches.
1495          *
1496          * @param array $set
1497          * @throws MWException When tag conditions are not met.
1498          * @return string
1499          */
1500         private static function getTagAttributeCallback( $set ) {
1501                 if ( isset( $set[5] ) ) {
1502                         # No quotes.
1503                         return $set[5];
1504                 } elseif ( isset( $set[4] ) ) {
1505                         # Single-quoted
1506                         return $set[4];
1507                 } elseif ( isset( $set[3] ) ) {
1508                         # Double-quoted
1509                         return $set[3];
1510                 } elseif ( !isset( $set[2] ) ) {
1511                         # In XHTML, attributes must have a value so return an empty string.
1512                         # See "Empty attribute syntax",
1513                         # https://www.w3.org/TR/html5/syntax.html#syntax-attribute-name
1514                         return "";
1515                 } else {
1516                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1517                 }
1518         }
1519
1520         /**
1521          * @param string $text
1522          * @return string
1523          */
1524         private static function normalizeWhitespace( $text ) {
1525                 return preg_replace(
1526                         '/\r\n|[\x20\x0d\x0a\x09]/',
1527                         ' ',
1528                         $text );
1529         }
1530
1531         /**
1532          * Normalizes whitespace in a section name, such as might be returned
1533          * by Parser::stripSectionName(), for use in the id's that are used for
1534          * section links.
1535          *
1536          * @param string $section
1537          * @return string
1538          */
1539         static function normalizeSectionNameWhitespace( $section ) {
1540                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1541         }
1542
1543         /**
1544          * Ensure that any entities and character references are legal
1545          * for XML and XHTML specifically. Any stray bits will be
1546          * &amp;-escaped to result in a valid text fragment.
1547          *
1548          * a. named char refs can only be &lt; &gt; &amp; &quot;, others are
1549          *   numericized (this way we're well-formed even without a DTD)
1550          * b. any numeric char refs must be legal chars, not invalid or forbidden
1551          * c. use lower cased "&#x", not "&#X"
1552          * d. fix or reject non-valid attributes
1553          *
1554          * @param string $text
1555          * @return string
1556          * @private
1557          */
1558         static function normalizeCharReferences( $text ) {
1559                 return preg_replace_callback(
1560                         self::CHAR_REFS_REGEX,
1561                         [ 'Sanitizer', 'normalizeCharReferencesCallback' ],
1562                         $text );
1563         }
1564
1565         /**
1566          * @param string $matches
1567          * @return string
1568          */
1569         static function normalizeCharReferencesCallback( $matches ) {
1570                 $ret = null;
1571                 if ( $matches[1] != '' ) {
1572                         $ret = self::normalizeEntity( $matches[1] );
1573                 } elseif ( $matches[2] != '' ) {
1574                         $ret = self::decCharReference( $matches[2] );
1575                 } elseif ( $matches[3] != '' ) {
1576                         $ret = self::hexCharReference( $matches[3] );
1577                 }
1578                 if ( is_null( $ret ) ) {
1579                         return htmlspecialchars( $matches[0] );
1580                 } else {
1581                         return $ret;
1582                 }
1583         }
1584
1585         /**
1586          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1587          * return the equivalent numeric entity reference (except for the core &lt;
1588          * &gt; &amp; &quot;). If the entity is a MediaWiki-specific alias, returns
1589          * the HTML equivalent. Otherwise, returns HTML-escaped text of
1590          * pseudo-entity source (eg &amp;foo;)
1591          *
1592          * @param string $name
1593          * @return string
1594          */
1595         static function normalizeEntity( $name ) {
1596                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1597                         return '&' . self::$htmlEntityAliases[$name] . ';';
1598                 } elseif ( in_array( $name, [ 'lt', 'gt', 'amp', 'quot' ] ) ) {
1599                         return "&$name;";
1600                 } elseif ( isset( self::$htmlEntities[$name] ) ) {
1601                         return '&#' . self::$htmlEntities[$name] . ';';
1602                 } else {
1603                         return "&amp;$name;";
1604                 }
1605         }
1606
1607         /**
1608          * @param int $codepoint
1609          * @return null|string
1610          */
1611         static function decCharReference( $codepoint ) {
1612                 $point = intval( $codepoint );
1613                 if ( self::validateCodepoint( $point ) ) {
1614                         return sprintf( '&#%d;', $point );
1615                 } else {
1616                         return null;
1617                 }
1618         }
1619
1620         /**
1621          * @param int $codepoint
1622          * @return null|string
1623          */
1624         static function hexCharReference( $codepoint ) {
1625                 $point = hexdec( $codepoint );
1626                 if ( self::validateCodepoint( $point ) ) {
1627                         return sprintf( '&#x%x;', $point );
1628                 } else {
1629                         return null;
1630                 }
1631         }
1632
1633         /**
1634          * Returns true if a given Unicode codepoint is a valid character in
1635          * both HTML5 and XML.
1636          * @param int $codepoint
1637          * @return bool
1638          */
1639         private static function validateCodepoint( $codepoint ) {
1640                 # U+000C is valid in HTML5 but not allowed in XML.
1641                 # U+000D is valid in XML but not allowed in HTML5.
1642                 # U+007F - U+009F are disallowed in HTML5 (control characters).
1643                 return $codepoint == 0x09
1644                         || $codepoint == 0x0a
1645                         || ( $codepoint >= 0x20 && $codepoint <= 0x7e )
1646                         || ( $codepoint >= 0xa0 && $codepoint <= 0xd7ff )
1647                         || ( $codepoint >= 0xe000 && $codepoint <= 0xfffd )
1648                         || ( $codepoint >= 0x10000 && $codepoint <= 0x10ffff );
1649         }
1650
1651         /**
1652          * Decode any character references, numeric or named entities,
1653          * in the text and return a UTF-8 string.
1654          *
1655          * @param string $text
1656          * @return string
1657          */
1658         public static function decodeCharReferences( $text ) {
1659                 return preg_replace_callback(
1660                         self::CHAR_REFS_REGEX,
1661                         [ 'Sanitizer', 'decodeCharReferencesCallback' ],
1662                         $text );
1663         }
1664
1665         /**
1666          * Decode any character references, numeric or named entities,
1667          * in the next and normalize the resulting string. (T16952)
1668          *
1669          * This is useful for page titles, not for text to be displayed,
1670          * MediaWiki allows HTML entities to escape normalization as a feature.
1671          *
1672          * @param string $text Already normalized, containing entities
1673          * @return string Still normalized, without entities
1674          */
1675         public static function decodeCharReferencesAndNormalize( $text ) {
1676                 global $wgContLang;
1677                 $text = preg_replace_callback(
1678                         self::CHAR_REFS_REGEX,
1679                         [ 'Sanitizer', 'decodeCharReferencesCallback' ],
1680                         $text, /* limit */ -1, $count );
1681
1682                 if ( $count ) {
1683                         return $wgContLang->normalize( $text );
1684                 } else {
1685                         return $text;
1686                 }
1687         }
1688
1689         /**
1690          * @param string $matches
1691          * @return string
1692          */
1693         static function decodeCharReferencesCallback( $matches ) {
1694                 if ( $matches[1] != '' ) {
1695                         return self::decodeEntity( $matches[1] );
1696                 } elseif ( $matches[2] != '' ) {
1697                         return self::decodeChar( intval( $matches[2] ) );
1698                 } elseif ( $matches[3] != '' ) {
1699                         return self::decodeChar( hexdec( $matches[3] ) );
1700                 }
1701                 # Last case should be an ampersand by itself
1702                 return $matches[0];
1703         }
1704
1705         /**
1706          * Return UTF-8 string for a codepoint if that is a valid
1707          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1708          * @param int $codepoint
1709          * @return string
1710          * @private
1711          */
1712         static function decodeChar( $codepoint ) {
1713                 if ( self::validateCodepoint( $codepoint ) ) {
1714                         return UtfNormal\Utils::codepointToUtf8( $codepoint );
1715                 } else {
1716                         return UtfNormal\Constants::UTF8_REPLACEMENT;
1717                 }
1718         }
1719
1720         /**
1721          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1722          * return the UTF-8 encoding of that character. Otherwise, returns
1723          * pseudo-entity source (eg "&foo;")
1724          *
1725          * @param string $name
1726          * @return string
1727          */
1728         static function decodeEntity( $name ) {
1729                 if ( isset( self::$htmlEntityAliases[$name] ) ) {
1730                         $name = self::$htmlEntityAliases[$name];
1731                 }
1732                 if ( isset( self::$htmlEntities[$name] ) ) {
1733                         return UtfNormal\Utils::codepointToUtf8( self::$htmlEntities[$name] );
1734                 } else {
1735                         return "&$name;";
1736                 }
1737         }
1738
1739         /**
1740          * Fetch the whitelist of acceptable attributes for a given element name.
1741          *
1742          * @param string $element
1743          * @return array
1744          */
1745         static function attributeWhitelist( $element ) {
1746                 $list = self::setupAttributeWhitelist();
1747                 return isset( $list[$element] )
1748                         ? $list[$element]
1749                         : [];
1750         }
1751
1752         /**
1753          * Foreach array key (an allowed HTML element), return an array
1754          * of allowed attributes
1755          * @return array
1756          */
1757         static function setupAttributeWhitelist() {
1758                 static $whitelist;
1759
1760                 if ( $whitelist !== null ) {
1761                         return $whitelist;
1762                 }
1763
1764                 $common = [
1765                         # HTML
1766                         'id',
1767                         'class',
1768                         'style',
1769                         'lang',
1770                         'dir',
1771                         'title',
1772
1773                         # WAI-ARIA
1774                         'aria-describedby',
1775                         'aria-flowto',
1776                         'aria-label',
1777                         'aria-labelledby',
1778                         'aria-owns',
1779                         'role',
1780
1781                         # RDFa
1782                         # These attributes are specified in section 9 of
1783                         # https://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1784                         'about',
1785                         'property',
1786                         'resource',
1787                         'datatype',
1788                         'typeof',
1789
1790                         # Microdata. These are specified by
1791                         # https://html.spec.whatwg.org/multipage/microdata.html#the-microdata-model
1792                         'itemid',
1793                         'itemprop',
1794                         'itemref',
1795                         'itemscope',
1796                         'itemtype',
1797                 ];
1798
1799                 $block = array_merge( $common, [ 'align' ] );
1800                 $tablealign = [ 'align', 'valign' ];
1801                 $tablecell = [
1802                         'abbr',
1803                         'axis',
1804                         'headers',
1805                         'scope',
1806                         'rowspan',
1807                         'colspan',
1808                         'nowrap', # deprecated
1809                         'width', # deprecated
1810                         'height', # deprecated
1811                         'bgcolor', # deprecated
1812                 ];
1813
1814                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1815                 # See: https://www.w3.org/TR/html4/
1816                 $whitelist = [
1817                         # 7.5.4
1818                         'div'        => $block,
1819                         'center'     => $common, # deprecated
1820                         'span'       => $common,
1821
1822                         # 7.5.5
1823                         'h1'         => $block,
1824                         'h2'         => $block,
1825                         'h3'         => $block,
1826                         'h4'         => $block,
1827                         'h5'         => $block,
1828                         'h6'         => $block,
1829
1830                         # 7.5.6
1831                         # address
1832
1833                         # 8.2.4
1834                         'bdo'        => $common,
1835
1836                         # 9.2.1
1837                         'em'         => $common,
1838                         'strong'     => $common,
1839                         'cite'       => $common,
1840                         'dfn'        => $common,
1841                         'code'       => $common,
1842                         'samp'       => $common,
1843                         'kbd'        => $common,
1844                         'var'        => $common,
1845                         'abbr'       => $common,
1846                         # acronym
1847
1848                         # 9.2.2
1849                         'blockquote' => array_merge( $common, [ 'cite' ] ),
1850                         'q'          => array_merge( $common, [ 'cite' ] ),
1851
1852                         # 9.2.3
1853                         'sub'        => $common,
1854                         'sup'        => $common,
1855
1856                         # 9.3.1
1857                         'p'          => $block,
1858
1859                         # 9.3.2
1860                         'br'         => array_merge( $common, [ 'clear' ] ),
1861
1862                         # https://www.w3.org/TR/html5/text-level-semantics.html#the-wbr-element
1863                         'wbr'        => $common,
1864
1865                         # 9.3.4
1866                         'pre'        => array_merge( $common, [ 'width' ] ),
1867
1868                         # 9.4
1869                         'ins'        => array_merge( $common, [ 'cite', 'datetime' ] ),
1870                         'del'        => array_merge( $common, [ 'cite', 'datetime' ] ),
1871
1872                         # 10.2
1873                         'ul'         => array_merge( $common, [ 'type' ] ),
1874                         'ol'         => array_merge( $common, [ 'type', 'start', 'reversed' ] ),
1875                         'li'         => array_merge( $common, [ 'type', 'value' ] ),
1876
1877                         # 10.3
1878                         'dl'         => $common,
1879                         'dd'         => $common,
1880                         'dt'         => $common,
1881
1882                         # 11.2.1
1883                         'table'      => array_merge( $common,
1884                                                                 [ 'summary', 'width', 'border', 'frame',
1885                                                                                 'rules', 'cellspacing', 'cellpadding',
1886                                                                                 'align', 'bgcolor',
1887                                                                 ] ),
1888
1889                         # 11.2.2
1890                         'caption'    => $block,
1891
1892                         # 11.2.3
1893                         'thead'      => $common,
1894                         'tfoot'      => $common,
1895                         'tbody'      => $common,
1896
1897                         # 11.2.4
1898                         'colgroup'   => array_merge( $common, [ 'span' ] ),
1899                         'col'        => array_merge( $common, [ 'span' ] ),
1900
1901                         # 11.2.5
1902                         'tr'         => array_merge( $common, [ 'bgcolor' ], $tablealign ),
1903
1904                         # 11.2.6
1905                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1906                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1907
1908                         # 12.2
1909                         # NOTE: <a> is not allowed directly, but the attrib
1910                         # whitelist is used from the Parser object
1911                         'a'          => array_merge( $common, [ 'href', 'rel', 'rev' ] ), # rel/rev esp. for RDFa
1912
1913                         # 13.2
1914                         # Not usually allowed, but may be used for extension-style hooks
1915                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1916                         # true
1917                         'img'        => array_merge( $common, [ 'alt', 'src', 'width', 'height' ] ),
1918
1919                         'video'      => array_merge( $common, [ 'poster', 'controls', 'preload', 'width', 'height' ] ),
1920                         'source'     => array_merge( $common, [ 'type', 'src' ] ),
1921                         'track'      => array_merge( $common, [ 'type', 'src', 'srclang', 'kind', 'label' ] ),
1922
1923                         # 15.2.1
1924                         'tt'         => $common,
1925                         'b'          => $common,
1926                         'i'          => $common,
1927                         'big'        => $common,
1928                         'small'      => $common,
1929                         'strike'     => $common,
1930                         's'          => $common,
1931                         'u'          => $common,
1932
1933                         # 15.2.2
1934                         'font'       => array_merge( $common, [ 'size', 'color', 'face' ] ),
1935                         # basefont
1936
1937                         # 15.3
1938                         'hr'         => array_merge( $common, [ 'width' ] ),
1939
1940                         # HTML Ruby annotation text module, simple ruby only.
1941                         # https://www.w3.org/TR/html5/text-level-semantics.html#the-ruby-element
1942                         'ruby'       => $common,
1943                         # rbc
1944                         'rb'         => $common,
1945                         'rp'         => $common,
1946                         'rt'         => $common, # array_merge( $common, array( 'rbspan' ) ),
1947                         'rtc'        => $common,
1948
1949                         # MathML root element, where used for extensions
1950                         # 'title' may not be 100% valid here; it's XHTML
1951                         # https://www.w3.org/TR/REC-MathML/
1952                         'math'       => [ 'class', 'style', 'id', 'title' ],
1953
1954                         # HTML 5 section 4.6
1955                         'bdi' => $common,
1956
1957                         # HTML5 elements, defined by:
1958                         # https://html.spec.whatwg.org/multipage/semantics.html#the-data-element
1959                         'data' => array_merge( $common, [ 'value' ] ),
1960                         'time' => array_merge( $common, [ 'datetime' ] ),
1961                         'mark' => $common,
1962
1963                         // meta and link are only permitted by removeHTMLtags when Microdata
1964                         // is enabled so we don't bother adding a conditional to hide these
1965                         // Also meta and link are only valid in WikiText as Microdata elements
1966                         // (ie: validateTag rejects tags missing the attributes needed for Microdata)
1967                         // So we don't bother including $common attributes that have no purpose.
1968                         'meta' => [ 'itemprop', 'content' ],
1969                         'link' => [ 'itemprop', 'href' ],
1970                 ];
1971
1972                 return $whitelist;
1973         }
1974
1975         /**
1976          * Take a fragment of (potentially invalid) HTML and return
1977          * a version with any tags removed, encoded as plain text.
1978          *
1979          * Warning: this return value must be further escaped for literal
1980          * inclusion in HTML output as of 1.10!
1981          *
1982          * @param string $text HTML fragment
1983          * @return string
1984          */
1985         static function stripAllTags( $text ) {
1986                 # Actual <tags>
1987                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1988
1989                 # Normalize &entities and whitespace
1990                 $text = self::decodeCharReferences( $text );
1991                 $text = self::normalizeWhitespace( $text );
1992
1993                 return $text;
1994         }
1995
1996         /**
1997          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1998          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1999          * PHP 5.1 doesn't.
2000          *
2001          * Use for passing XHTML fragments to PHP's XML parsing functions
2002          *
2003          * @return string
2004          */
2005         static function hackDocType() {
2006                 $out = "<!DOCTYPE html [\n";
2007                 foreach ( self::$htmlEntities as $entity => $codepoint ) {
2008                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
2009                 }
2010                 $out .= "]>\n";
2011                 return $out;
2012         }
2013
2014         /**
2015          * @param string $url
2016          * @return mixed|string
2017          */
2018         static function cleanUrl( $url ) {
2019                 # Normalize any HTML entities in input. They will be
2020                 # re-escaped by makeExternalLink().
2021                 $url = self::decodeCharReferences( $url );
2022
2023                 # Escape any control characters introduced by the above step
2024                 $url = preg_replace_callback( '/[\][<>"\\x00-\\x20\\x7F\|]/',
2025                         [ __CLASS__, 'cleanUrlCallback' ], $url );
2026
2027                 # Validate hostname portion
2028                 $matches = [];
2029                 if ( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
2030                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
2031
2032                         // Characters that will be ignored in IDNs.
2033                         // https://tools.ietf.org/html/rfc3454#section-3.1
2034                         // Strip them before further processing so blacklists and such work.
2035                         $strip = "/
2036                                 \\s|          # general whitespace
2037                                 \xc2\xad|     # 00ad SOFT HYPHEN
2038                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
2039                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
2040                                 \xe2\x81\xa0| # 2060 WORD JOINER
2041                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
2042                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
2043                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
2044                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
2045                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
2046                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
2047                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
2048                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe0f VARIATION SELECTOR-1-16
2049                                 /xuD";
2050
2051                         $host = preg_replace( $strip, '', $host );
2052
2053                         // IPv6 host names are bracketed with [].  Url-decode these.
2054                         if ( substr_compare( "//%5B", $host, 0, 5 ) === 0 &&
2055                                 preg_match( '!^//%5B([0-9A-Fa-f:.]+)%5D((:\d+)?)$!', $host, $matches )
2056                         ) {
2057                                 $host = '//[' . $matches[1] . ']' . $matches[2];
2058                         }
2059
2060                         // @todo FIXME: Validate hostnames here
2061
2062                         return $protocol . $host . $rest;
2063                 } else {
2064                         return $url;
2065                 }
2066         }
2067
2068         /**
2069          * @param array $matches
2070          * @return string
2071          */
2072         static function cleanUrlCallback( $matches ) {
2073                 return urlencode( $matches[0] );
2074         }
2075
2076         /**
2077          * Does a string look like an e-mail address?
2078          *
2079          * This validates an email address using an HTML5 specification found at:
2080          * http://www.whatwg.org/html/states-of-the-type-attribute.html#valid-e-mail-address
2081          * Which as of 2011-01-24 says:
2082          *
2083          *   A valid e-mail address is a string that matches the ABNF production
2084          *   1*( atext / "." ) "@" ldh-str *( "." ldh-str ) where atext is defined
2085          *   in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section
2086          *   3.5.
2087          *
2088          * This function is an implementation of the specification as requested in
2089          * T24449.
2090          *
2091          * Client-side forms will use the same standard validation rules via JS or
2092          * HTML 5 validation; additional restrictions can be enforced server-side
2093          * by extensions via the 'isValidEmailAddr' hook.
2094          *
2095          * Note that this validation doesn't 100% match RFC 2822, but is believed
2096          * to be liberal enough for wide use. Some invalid addresses will still
2097          * pass validation here.
2098          *
2099          * @since 1.18
2100          *
2101          * @param string $addr E-mail address
2102          * @return bool
2103          */
2104         public static function validateEmail( $addr ) {
2105                 $result = null;
2106                 if ( !Hooks::run( 'isValidEmailAddr', [ $addr, &$result ] ) ) {
2107                         return $result;
2108                 }
2109
2110                 // Please note strings below are enclosed in brackets [], this make the
2111                 // hyphen "-" a range indicator. Hence it is double backslashed below.
2112                 // See T28948
2113                 $rfc5322_atext = "a-z0-9!#$%&'*+\\-\/=?^_`{|}~";
2114                 $rfc1034_ldh_str = "a-z0-9\\-";
2115
2116                 $html5_email_regexp = "/
2117                 ^                      # start of string
2118                 [$rfc5322_atext\\.]+    # user part which is liberal :p
2119                 @                      # 'apostrophe'
2120                 [$rfc1034_ldh_str]+       # First domain part
2121                 (\\.[$rfc1034_ldh_str]+)*  # Following part prefixed with a dot
2122                 $                      # End of string
2123                 /ix"; // case Insensitive, eXtended
2124
2125                 return (bool)preg_match( $html5_email_regexp, $addr );
2126         }
2127 }