includes/Sanitizer.php

   1 <?php
   2 /**
   3  * XHTML sanitizer for MediaWiki
   4  *
   5  * Copyright (C) 2002-2005 Brion Vibber <brion@pobox.com> et al
   6  * http://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Parser
  25  */
  26
  27 /**
  28  * Regular expression to match various types of character references in
  29  * Sanitizer::normalizeCharReferences and Sanitizer::decodeCharReferences
  30  */
  31 define( 'MW_CHAR_REFS_REGEX',
  32         '/&([A-Za-z0-9\x80-\xff]+);
  33          |&\#([0-9]+);
  34          |&\#x([0-9A-Za-z]+);
  35          |&\#X([0-9A-Za-z]+);
  36          |(&)/x' );
  37
  38 /**
  39  * Regular expression to match HTML/XML attribute pairs within a tag.
  40  * Allows some... latitude.
  41  * Used in Sanitizer::fixTagAttributes and Sanitizer::decodeTagAttributes
  42  */
  43 $attrib = '[A-Za-z0-9]';
  44 $space = '[\x09\x0a\x0d\x20]';
  45 define( 'MW_ATTRIBS_REGEX',
  46         "/(?:^|$space)((?:xml:|xmlns:)?$attrib+)
  47           ($space*=$space*
  48                 (?:
  49                  # The attribute value: quoted or alone
  50                   \"([^<\"]*)\"
  51                  | '([^<']*)'
  52                  |  ([a-zA-Z0-9!#$%&()*,\\-.\\/:;<>?@[\\]^_`{|}~]+)
  53                  |  (\#[0-9a-fA-F]+) # Technically wrong, but lots of
  54                                                          # colors are specified like this.
  55                                                          # We'll be normalizing it.
  56                 )
  57            )?(?=$space|\$)/sx" );
  58
  59 /**
  60  * Regular expression to match URIs that could trigger script execution
  61  */
  62 define( 'MW_EVIL_URI_PATTERN', '!(^|\s|\*/\s*)(javascript|vbscript)([^\w]|$)!i' );
  63
  64 /**
  65  * Regular expression to match namespace attributes
  66  */
  67 define( 'MW_XMLNS_ATTRIBUTE_PATTRN', "/^xmlns:$attrib+$/" );
  68
  69 /**
  70  * List of all named character entities defined in HTML 4.01
  71  * http://www.w3.org/TR/html4/sgml/entities.html
  72  * @private
  73  */
  74 global $wgHtmlEntities;
  75 $wgHtmlEntities = array(
  76         'Aacute'   => 193,
  77         'aacute'   => 225,
  78         'Acirc'    => 194,
  79         'acirc'    => 226,
  80         'acute'    => 180,
  81         'AElig'    => 198,
  82         'aelig'    => 230,
  83         'Agrave'   => 192,
  84         'agrave'   => 224,
  85         'alefsym'  => 8501,
  86         'Alpha'    => 913,
  87         'alpha'    => 945,
  88         'amp'      => 38,
  89         'and'      => 8743,
  90         'ang'      => 8736,
  91         'Aring'    => 197,
  92         'aring'    => 229,
  93         'asymp'    => 8776,
  94         'Atilde'   => 195,
  95         'atilde'   => 227,
  96         'Auml'     => 196,
  97         'auml'     => 228,
  98         'bdquo'    => 8222,
  99         'Beta'     => 914,
 100         'beta'     => 946,
 101         'brvbar'   => 166,
 102         'bull'     => 8226,
 103         'cap'      => 8745,
 104         'Ccedil'   => 199,
 105         'ccedil'   => 231,
 106         'cedil'    => 184,
 107         'cent'     => 162,
 108         'Chi'      => 935,
 109         'chi'      => 967,
 110         'circ'     => 710,
 111         'clubs'    => 9827,
 112         'cong'     => 8773,
 113         'copy'     => 169,
 114         'crarr'    => 8629,
 115         'cup'      => 8746,
 116         'curren'   => 164,
 117         'dagger'   => 8224,
 118         'Dagger'   => 8225,
 119         'darr'     => 8595,
 120         'dArr'     => 8659,
 121         'deg'      => 176,
 122         'Delta'    => 916,
 123         'delta'    => 948,
 124         'diams'    => 9830,
 125         'divide'   => 247,
 126         'Eacute'   => 201,
 127         'eacute'   => 233,
 128         'Ecirc'    => 202,
 129         'ecirc'    => 234,
 130         'Egrave'   => 200,
 131         'egrave'   => 232,
 132         'empty'    => 8709,
 133         'emsp'     => 8195,
 134         'ensp'     => 8194,
 135         'Epsilon'  => 917,
 136         'epsilon'  => 949,
 137         'equiv'    => 8801,
 138         'Eta'      => 919,
 139         'eta'      => 951,
 140         'ETH'      => 208,
 141         'eth'      => 240,
 142         'Euml'     => 203,
 143         'euml'     => 235,
 144         'euro'     => 8364,
 145         'exist'    => 8707,
 146         'fnof'     => 402,
 147         'forall'   => 8704,
 148         'frac12'   => 189,
 149         'frac14'   => 188,
 150         'frac34'   => 190,
 151         'frasl'    => 8260,
 152         'Gamma'    => 915,
 153         'gamma'    => 947,
 154         'ge'       => 8805,
 155         'gt'       => 62,
 156         'harr'     => 8596,
 157         'hArr'     => 8660,
 158         'hearts'   => 9829,
 159         'hellip'   => 8230,
 160         'Iacute'   => 205,
 161         'iacute'   => 237,
 162         'Icirc'    => 206,
 163         'icirc'    => 238,
 164         'iexcl'    => 161,
 165         'Igrave'   => 204,
 166         'igrave'   => 236,
 167         'image'    => 8465,
 168         'infin'    => 8734,
 169         'int'      => 8747,
 170         'Iota'     => 921,
 171         'iota'     => 953,
 172         'iquest'   => 191,
 173         'isin'     => 8712,
 174         'Iuml'     => 207,
 175         'iuml'     => 239,
 176         'Kappa'    => 922,
 177         'kappa'    => 954,
 178         'Lambda'   => 923,
 179         'lambda'   => 955,
 180         'lang'     => 9001,
 181         'laquo'    => 171,
 182         'larr'     => 8592,
 183         'lArr'     => 8656,
 184         'lceil'    => 8968,
 185         'ldquo'    => 8220,
 186         'le'       => 8804,
 187         'lfloor'   => 8970,
 188         'lowast'   => 8727,
 189         'loz'      => 9674,
 190         'lrm'      => 8206,
 191         'lsaquo'   => 8249,
 192         'lsquo'    => 8216,
 193         'lt'       => 60,
 194         'macr'     => 175,
 195         'mdash'    => 8212,
 196         'micro'    => 181,
 197         'middot'   => 183,
 198         'minus'    => 8722,
 199         'Mu'       => 924,
 200         'mu'       => 956,
 201         'nabla'    => 8711,
 202         'nbsp'     => 160,
 203         'ndash'    => 8211,
 204         'ne'       => 8800,
 205         'ni'       => 8715,
 206         'not'      => 172,
 207         'notin'    => 8713,
 208         'nsub'     => 8836,
 209         'Ntilde'   => 209,
 210         'ntilde'   => 241,
 211         'Nu'       => 925,
 212         'nu'       => 957,
 213         'Oacute'   => 211,
 214         'oacute'   => 243,
 215         'Ocirc'    => 212,
 216         'ocirc'    => 244,
 217         'OElig'    => 338,
 218         'oelig'    => 339,
 219         'Ograve'   => 210,
 220         'ograve'   => 242,
 221         'oline'    => 8254,
 222         'Omega'    => 937,
 223         'omega'    => 969,
 224         'Omicron'  => 927,
 225         'omicron'  => 959,
 226         'oplus'    => 8853,
 227         'or'       => 8744,
 228         'ordf'     => 170,
 229         'ordm'     => 186,
 230         'Oslash'   => 216,
 231         'oslash'   => 248,
 232         'Otilde'   => 213,
 233         'otilde'   => 245,
 234         'otimes'   => 8855,
 235         'Ouml'     => 214,
 236         'ouml'     => 246,
 237         'para'     => 182,
 238         'part'     => 8706,
 239         'permil'   => 8240,
 240         'perp'     => 8869,
 241         'Phi'      => 934,
 242         'phi'      => 966,
 243         'Pi'       => 928,
 244         'pi'       => 960,
 245         'piv'      => 982,
 246         'plusmn'   => 177,
 247         'pound'    => 163,
 248         'prime'    => 8242,
 249         'Prime'    => 8243,
 250         'prod'     => 8719,
 251         'prop'     => 8733,
 252         'Psi'      => 936,
 253         'psi'      => 968,
 254         'quot'     => 34,
 255         'radic'    => 8730,
 256         'rang'     => 9002,
 257         'raquo'    => 187,
 258         'rarr'     => 8594,
 259         'rArr'     => 8658,
 260         'rceil'    => 8969,
 261         'rdquo'    => 8221,
 262         'real'     => 8476,
 263         'reg'      => 174,
 264         'rfloor'   => 8971,
 265         'Rho'      => 929,
 266         'rho'      => 961,
 267         'rlm'      => 8207,
 268         'rsaquo'   => 8250,
 269         'rsquo'    => 8217,
 270         'sbquo'    => 8218,
 271         'Scaron'   => 352,
 272         'scaron'   => 353,
 273         'sdot'     => 8901,
 274         'sect'     => 167,
 275         'shy'      => 173,
 276         'Sigma'    => 931,
 277         'sigma'    => 963,
 278         'sigmaf'   => 962,
 279         'sim'      => 8764,
 280         'spades'   => 9824,
 281         'sub'      => 8834,
 282         'sube'     => 8838,
 283         'sum'      => 8721,
 284         'sup'      => 8835,
 285         'sup1'     => 185,
 286         'sup2'     => 178,
 287         'sup3'     => 179,
 288         'supe'     => 8839,
 289         'szlig'    => 223,
 290         'Tau'      => 932,
 291         'tau'      => 964,
 292         'there4'   => 8756,
 293         'Theta'    => 920,
 294         'theta'    => 952,
 295         'thetasym' => 977,
 296         'thinsp'   => 8201,
 297         'THORN'    => 222,
 298         'thorn'    => 254,
 299         'tilde'    => 732,
 300         'times'    => 215,
 301         'trade'    => 8482,
 302         'Uacute'   => 218,
 303         'uacute'   => 250,
 304         'uarr'     => 8593,
 305         'uArr'     => 8657,
 306         'Ucirc'    => 219,
 307         'ucirc'    => 251,
 308         'Ugrave'   => 217,
 309         'ugrave'   => 249,
 310         'uml'      => 168,
 311         'upsih'    => 978,
 312         'Upsilon'  => 933,
 313         'upsilon'  => 965,
 314         'Uuml'     => 220,
 315         'uuml'     => 252,
 316         'weierp'   => 8472,
 317         'Xi'       => 926,
 318         'xi'       => 958,
 319         'Yacute'   => 221,
 320         'yacute'   => 253,
 321         'yen'      => 165,
 322         'Yuml'     => 376,
 323         'yuml'     => 255,
 324         'Zeta'     => 918,
 325         'zeta'     => 950,
 326         'zwj'      => 8205,
 327         'zwnj'     => 8204 );
 328
 329 /**
 330  * Character entity aliases accepted by MediaWiki
 331  */
 332 global $wgHtmlEntityAliases;
 333 $wgHtmlEntityAliases = array(
 334         'רלמ' => 'rlm',
 335         'رلم' => 'rlm',
 336 );
 337
 338
 339 /**
 340  * XHTML sanitizer for MediaWiki
 341  * @ingroup Parser
 342  */
 343 class Sanitizer {
 344         /**
 345          * Cleans up HTML, removes dangerous tags and attributes, and
 346          * removes HTML comments
 347          * @private
 348          * @param $text String
 349          * @param $processCallback Callback to do any variable or parameter replacements in HTML attribute values
 350          * @param $args Array for the processing callback
 351          * @param $extratags Array for any extra tags to include
 352          * @param $removetags Array for any tags (default or extra) to exclude
 353          * @return string
 354          */
 355         static function removeHTMLtags( $text, $processCallback = null, $args = array(), $extratags = array(), $removetags = array() ) {
 356                 global $wgUseTidy;
 357
 358                 static $htmlpairsStatic, $htmlsingle, $htmlsingleonly, $htmlnest, $tabletags,
 359                         $htmllist, $listtags, $htmlsingleallowed, $htmlelementsStatic, $staticInitialised;
 360
 361                 wfProfileIn( __METHOD__ );
 362
 363                 if ( !$staticInitialised ) {
 364
 365                         $htmlpairsStatic = array( # Tags that must be closed
 366                                 'b', 'del', 'i', 'ins', 'u', 'font', 'big', 'small', 'sub', 'sup', 'h1',
 367                                 'h2', 'h3', 'h4', 'h5', 'h6', 'cite', 'code', 'em', 's',
 368                                 'strike', 'strong', 'tt', 'var', 'div', 'center',
 369                                 'blockquote', 'ol', 'ul', 'dl', 'table', 'caption', 'pre',
 370                                 'ruby', 'rt' , 'rb' , 'rp', 'p', 'span', 'u', 'abbr'
 371                         );
 372                         $htmlsingle = array(
 373                                 'br', 'hr', 'li', 'dt', 'dd'
 374                         );
 375                         $htmlsingleonly = array( # Elements that cannot have close tags
 376                                 'br', 'hr'
 377                         );
 378                         $htmlnest = array( # Tags that can be nested--??
 379                                 'table', 'tr', 'td', 'th', 'div', 'blockquote', 'ol', 'ul',
 380                                 'dl', 'font', 'big', 'small', 'sub', 'sup', 'span'
 381                         );
 382                         $tabletags = array( # Can only appear inside table, we will close them
 383                                 'td', 'th', 'tr',
 384                         );
 385                         $htmllist = array( # Tags used by list
 386                                 'ul','ol',
 387                         );
 388                         $listtags = array( # Tags that can appear in a list
 389                                 'li',
 390                         );
 391
 392                         global $wgAllowImageTag;
 393                         if ( $wgAllowImageTag ) {
 394                                 $htmlsingle[] = 'img';
 395                                 $htmlsingleonly[] = 'img';
 396                         }
 397
 398                         $htmlsingleallowed = array_unique( array_merge( $htmlsingle, $tabletags ) );
 399                         $htmlelementsStatic = array_unique( array_merge( $htmlsingle, $htmlpairsStatic, $htmlnest ) );
 400
 401                         # Convert them all to hashtables for faster lookup
 402                         $vars = array( 'htmlpairsStatic', 'htmlsingle', 'htmlsingleonly', 'htmlnest', 'tabletags',
 403                                 'htmllist', 'listtags', 'htmlsingleallowed', 'htmlelementsStatic' );
 404                         foreach ( $vars as $var ) {
 405                                 $$var = array_flip( $$var );
 406                         }
 407                         $staticInitialised = true;
 408                 }
 409                 # Populate $htmlpairs and $htmlelements with the $extratags and $removetags arrays
 410                 $extratags = array_flip( $extratags );
 411                 $removetags = array_flip( $removetags );
 412                 $htmlpairs = array_merge( $extratags, $htmlpairsStatic );
 413                 $htmlelements = array_diff_key( array_merge( $extratags, $htmlelementsStatic ) , $removetags );
 414
 415                 # Remove HTML comments
 416                 $text = Sanitizer::removeHTMLcomments( $text );
 417                 $bits = explode( '<', $text );
 418                 $text = str_replace( '>', '&gt;', array_shift( $bits ) );
 419                 if ( !$wgUseTidy ) {
 420                         $tagstack = $tablestack = array();
 421                         foreach ( $bits as $x ) {
 422                                 $regs = array();
 423                                 # $slash: Does the current element start with a '/'?
 424                                 # $t: Current element name
 425                                 # $params: String between element name and >
 426                                 # $brace: Ending '>' or '/>'
 427                                 # $rest: Everything until the next element of $bits
 428                                 if( preg_match( '!^(/?)(\\w+)([^>]*?)(/{0,1}>)([^<]*)$!', $x, $regs ) ) {
 429                                         list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 430                                 } else {
 431                                         $slash = $t = $params = $brace = $rest = null;
 432                                 }
 433
 434                                 $badtag = false;
 435                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 436                                         # Check our stack
 437                                         if ( $slash && isset( $htmlsingleonly[$t] ) ) {
 438                                                 $badtag = true;
 439                                         } elseif ( $slash ) {
 440                                                 # Closing a tag... is it the one we just opened?
 441                                                 $ot = @array_pop( $tagstack );
 442                                                 if ( $ot != $t ) {
 443                                                         if ( isset( $htmlsingleallowed[$ot] ) ) {
 444                                                                 # Pop all elements with an optional close tag
 445                                                                 # and see if we find a match below them
 446                                                                 $optstack = array();
 447                                                                 array_push( $optstack, $ot );
 448                                                                 $ot = @array_pop( $tagstack );
 449                                                                 while ( $ot != $t && isset( $htmlsingleallowed[$ot] ) ) {
 450                                                                         array_push( $optstack, $ot );
 451                                                                         $ot = @array_pop( $tagstack );
 452                                                                 }
 453                                                                 if ( $t != $ot ) {
 454                                                                         # No match. Push the optional elements back again
 455                                                                         $badtag = true;
 456                                                                         while ( $ot = @array_pop( $optstack ) ) {
 457                                                                                 array_push( $tagstack, $ot );
 458                                                                         }
 459                                                                 }
 460                                                         } else {
 461                                                                 @array_push( $tagstack, $ot );
 462                                                                 # <li> can be nested in <ul> or <ol>, skip those cases:
 463                                                                 if ( !isset( $htmllist[$ot] ) || !isset( $listtags[$t] ) ) {
 464                                                                         $badtag = true;
 465                                                                 }
 466                                                         }
 467                                                 } else {
 468                                                         if ( $t == 'table' ) {
 469                                                                 $tagstack = array_pop( $tablestack );
 470                                                         }
 471                                                 }
 472                                                 $newparams = '';
 473                                         } else {
 474                                                 # Keep track for later
 475                                                 if ( isset( $tabletags[$t] ) &&
 476                                                 !in_array( 'table', $tagstack ) ) {
 477                                                         $badtag = true;
 478                                                 } elseif ( in_array( $t, $tagstack ) &&
 479                                                 !isset( $htmlnest [$t ] ) ) {
 480                                                         $badtag = true;
 481                                                 # Is it a self closed htmlpair ? (bug 5487)
 482                                                 } elseif ( $brace == '/>' &&
 483                                                 isset( $htmlpairs[$t] ) ) {
 484                                                         $badtag = true;
 485                                                 } elseif ( isset( $htmlsingleonly[$t] ) ) {
 486                                                         # Hack to force empty tag for uncloseable elements
 487                                                         $brace = '/>';
 488                                                 } elseif ( isset( $htmlsingle[$t] ) ) {
 489                                                         # Hack to not close $htmlsingle tags
 490                                                         $brace = null;
 491                                                 } elseif ( isset( $tabletags[$t] )
 492                                                 && in_array( $t, $tagstack ) ) {
 493                                                         // New table tag but forgot to close the previous one
 494                                                         $text .= "</$t>";
 495                                                 } else {
 496                                                         if ( $t == 'table' ) {
 497                                                                 array_push( $tablestack, $tagstack );
 498                                                                 $tagstack = array();
 499                                                         }
 500                                                         array_push( $tagstack, $t );
 501                                                 }
 502
 503                                                 # Replace any variables or template parameters with
 504                                                 # plaintext results.
 505                                                 if( is_callable( $processCallback ) ) {
 506                                                         call_user_func_array( $processCallback, array( &$params, $args ) );
 507                                                 }
 508
 509                                                 # Strip non-approved attributes from the tag
 510                                                 $newparams = Sanitizer::fixTagAttributes( $params, $t );
 511                                         }
 512                                         if ( !$badtag ) {
 513                                                 $rest = str_replace( '>', '&gt;', $rest );
 514                                                 $close = ( $brace == '/>' && !$slash ) ? ' /' : '';
 515                                                 $text .= "<$slash$t$newparams$close>$rest";
 516                                                 continue;
 517                                         }
 518                                 }
 519                                 $text .= '&lt;' . str_replace( '>', '&gt;', $x);
 520                         }
 521                         # Close off any remaining tags
 522                         while ( is_array( $tagstack ) && ($t = array_pop( $tagstack )) ) {
 523                                 $text .= "</$t>\n";
 524                                 if ( $t == 'table' ) { $tagstack = array_pop( $tablestack ); }
 525                         }
 526                 } else {
 527                         # this might be possible using tidy itself
 528                         foreach ( $bits as $x ) {
 529                                 preg_match( '/^(\\/?)(\\w+)([^>]*?)(\\/{0,1}>)([^<]*)$/',
 530                                 $x, $regs );
 531                                 @list( /* $qbar */, $slash, $t, $params, $brace, $rest ) = $regs;
 532                                 if ( isset( $htmlelements[$t = strtolower( $t )] ) ) {
 533                                         if( is_callable( $processCallback ) ) {
 534                                                 call_user_func_array( $processCallback, array( &$params, $args ) );
 535                                         }
 536                                         $newparams = Sanitizer::fixTagAttributes( $params, $t );
 537                                         $rest = str_replace( '>', '&gt;', $rest );
 538                                         $text .= "<$slash$t$newparams$brace$rest";
 539                                 } else {
 540                                         $text .= '&lt;' . str_replace( '>', '&gt;', $x);
 541                                 }
 542                         }
 543                 }
 544                 wfProfileOut( __METHOD__ );
 545                 return $text;
 546         }
 547
 548         /**
 549          * Remove '<!--', '-->', and everything between.
 550          * To avoid leaving blank lines, when a comment is both preceded
 551          * and followed by a newline (ignoring spaces), trim leading and
 552          * trailing spaces and one of the newlines.
 553          *
 554          * @private
 555          * @param $text String
 556          * @return string
 557          */
 558         static function removeHTMLcomments( $text ) {
 559                 wfProfileIn( __METHOD__ );
 560                 while (($start = strpos($text, '<!--')) !== false) {
 561                         $end = strpos($text, '-->', $start + 4);
 562                         if ($end === false) {
 563                                 # Unterminated comment; bail out
 564                                 break;
 565                         }
 566
 567                         $end += 3;
 568
 569                         # Trim space and newline if the comment is both
 570                         # preceded and followed by a newline
 571                         $spaceStart = max($start - 1, 0);
 572                         $spaceLen = $end - $spaceStart;
 573                         while (substr($text, $spaceStart, 1) === ' ' && $spaceStart > 0) {
 574                                 $spaceStart--;
 575                                 $spaceLen++;
 576                         }
 577                         while (substr($text, $spaceStart + $spaceLen, 1) === ' ')
 578                                 $spaceLen++;
 579                         if (substr($text, $spaceStart, 1) === "\n" and substr($text, $spaceStart + $spaceLen, 1) === "\n") {
 580                                 # Remove the comment, leading and trailing
 581                                 # spaces, and leave only one newline.
 582                                 $text = substr_replace($text, "\n", $spaceStart, $spaceLen + 1);
 583                         }
 584                         else {
 585                                 # Remove just the comment.
 586                                 $text = substr_replace($text, '', $start, $end - $start);
 587                         }
 588                 }
 589                 wfProfileOut( __METHOD__ );
 590                 return $text;
 591         }
 592
 593         /**
 594          * Take an array of attribute names and values and normalize or discard
 595          * illegal values for the given element type.
 596          *
 597          * - Discards attributes not on a whitelist for the given element
 598          * - Unsafe style attributes are discarded
 599          * - Invalid id attributes are reencoded
 600          *
 601          * @param $attribs Array
 602          * @param $element String
 603          * @return Array
 604          *
 605          * @todo Check for legal values where the DTD limits things.
 606          * @todo Check for unique id attribute :P
 607          */
 608         static function validateTagAttributes( $attribs, $element ) {
 609                 return Sanitizer::validateAttributes( $attribs,
 610                         Sanitizer::attributeWhitelist( $element ) );
 611         }
 612
 613         /**
 614          * Take an array of attribute names and values and normalize or discard
 615          * illegal values for the given whitelist.
 616          *
 617          * - Discards attributes not the given whitelist
 618          * - Unsafe style attributes are discarded
 619          * - Invalid id attributes are reencoded
 620          *
 621          * @param $attribs Array
 622          * @param $whitelist Array: list of allowed attribute names
 623          * @return Array
 624          *
 625          * @todo Check for legal values where the DTD limits things.
 626          * @todo Check for unique id attribute :P
 627          */
 628         static function validateAttributes( $attribs, $whitelist ) {
 629                 global $wgAllowRdfaAttributes, $wgAllowMicrodataAttributes;
 630
 631                 $whitelist = array_flip( $whitelist );
 632                 $hrefExp = '/^(' . wfUrlProtocols() . ')[^\s]+$/';
 633
 634                 $out = array();
 635                 foreach( $attribs as $attribute => $value ) {
 636                         #allow XML namespace declaration if RDFa is enabled
 637                         if ( $wgAllowRdfaAttributes && preg_match( MW_XMLNS_ATTRIBUTE_PATTRN, $attribute ) ) {
 638                                 if ( !preg_match( MW_EVIL_URI_PATTERN, $value ) ) {
 639                                         $out[$attribute] = $value;
 640                                 }
 641
 642                                 continue;
 643                         }
 644
 645                         if( !isset( $whitelist[$attribute] ) ) {
 646                                 continue;
 647                         }
 648
 649                         # Strip javascript "expression" from stylesheets.
 650                         # http://msdn.microsoft.com/workshop/author/dhtml/overview/recalc.asp
 651                         if( $attribute == 'style' ) {
 652                                 $value = Sanitizer::checkCss( $value );
 653                         }
 654
 655                         if ( $attribute === 'id' ) {
 656                                 $value = Sanitizer::escapeId( $value, 'noninitial' );
 657                         }
 658
 659                         //RDFa and microdata properties allow URLs, URIs and/or CURIs. check them for sanity
 660                         if ( $attribute === 'rel' || $attribute === 'rev' ||
 661                                 $attribute === 'about' || $attribute === 'property' || $attribute === 'resource' || #RDFa
 662                                 $attribute === 'datatype' || $attribute === 'typeof' ||                             #RDFa
 663                                 $attribute === 'itemid' || $attribute === 'itemprop' || $attribute === 'itemref' || #HTML5 microdata
 664                                 $attribute === 'itemscope' || $attribute === 'itemtype' ) {                         #HTML5 microdata
 665
 666                                 //Paranoia. Allow "simple" values but suppress javascript
 667                                 if ( preg_match( MW_EVIL_URI_PATTERN, $value ) ) {
 668                                         continue;
 669                                 }
 670                         }
 671
 672                         # NOTE: even though elements using href/src are not allowed directly, supply
 673                         #       validation code that can be used by tag hook handlers, etc
 674                         if ( $attribute === 'href' || $attribute === 'src' ) {
 675                                 if ( !preg_match( $hrefExp, $value ) ) {
 676                                         continue; //drop any href or src attributes not using an allowed protocol.
 677                                                   //NOTE: this also drops all relative URLs
 678                                 }
 679                         }
 680
 681                         // If this attribute was previously set, override it.
 682                         // Output should only have one attribute of each name.
 683                         $out[$attribute] = $value;
 684                 }
 685
 686                 if ( $wgAllowMicrodataAttributes ) {
 687                         # There are some complicated validity constraints we need to
 688                         # enforce here.  First of all, we don't want to allow non-standard
 689                         # itemtypes.
 690                         $allowedTypes = array(
 691                                 'http://microformats.org/profile/hcard',
 692                                 'http://microformats.org/profile/hcalendar#vevent',
 693                                 'http://n.whatwg.org/work',
 694                         );
 695                         if ( isset( $out['itemtype'] ) && !in_array( $out['itemtype'],
 696                         $allowedTypes ) ) {
 697                                 # Kill everything
 698                                 unset( $out['itemscope'] );
 699                         }
 700                         # itemtype, itemid, itemref don't make sense without itemscope
 701                         if ( !array_key_exists( 'itemscope', $out ) ) {
 702                                 unset( $out['itemtype'] );
 703                                 unset( $out['itemid'] );
 704                                 unset( $out['itemref'] );
 705                         }
 706                         # TODO: Strip itemprop if we aren't descendants of an itemscope.
 707                 }
 708                 return $out;
 709         }
 710
 711         /**
 712          * Merge two sets of HTML attributes.  Conflicting items in the second set
 713          * will override those in the first, except for 'class' attributes which
 714          * will be combined (if they're both strings).
 715          *
 716          * @todo implement merging for other attributes such as style
 717          * @param $a Array
 718          * @param $b Array
 719          * @return array
 720          */
 721         static function mergeAttributes( $a, $b ) {
 722                 $out = array_merge( $a, $b );
 723                 if( isset( $a['class'] ) && isset( $b['class'] )
 724                 && is_string( $a['class'] ) && is_string( $b['class'] )
 725                 && $a['class'] !== $b['class'] ) {
 726                         $classes = preg_split( '/\s+/', "{$a['class']} {$b['class']}",
 727                                 -1, PREG_SPLIT_NO_EMPTY );
 728                         $out['class'] = implode( ' ', array_unique( $classes ) );
 729                 }
 730                 return $out;
 731         }
 732
 733         /**
 734          * Pick apart some CSS and check it for forbidden or unsafe structures.
 735          * Returns a sanitized string, or false if it was just too evil.
 736          *
 737          * Currently URL references, 'expression', 'tps' are forbidden.
 738          *
 739          * @param $value String
 740          * @return Mixed
 741          */
 742         static function checkCss( $value ) {
 743                 $value = Sanitizer::decodeCharReferences( $value );
 744
 745                 // Remove any comments; IE gets token splitting wrong
 746                 $value = StringUtils::delimiterReplace( '/*', '*/', ' ', $value );
 747
 748                 // Decode escape sequences and line continuation
 749                 // See the grammar in the CSS 2 spec, appendix D.
 750                 static $decodeRegex, $reencodeTable;
 751                 if ( !$decodeRegex ) {
 752                         $space = '[\\x20\\t\\r\\n\\f]';
 753                         $nl = '(?:\\n|\\r\\n|\\r|\\f)';
 754                         $backslash = '\\\\';
 755                         $decodeRegex = "/ $backslash
 756                                 (?:
 757                                         ($nl) |  # 1. Line continuation
 758                                         ([0-9A-Fa-f]{1,6})$space? |  # 2. character number
 759                                         (.) | # 3. backslash cancelling special meaning
 760                                         () | # 4. backslash at end of string
 761                                 )/xu";
 762                 }
 763                 $value = preg_replace_callback( $decodeRegex,
 764                         array( __CLASS__, 'cssDecodeCallback' ), $value );
 765
 766                 // Reject problematic keywords and control characters
 767                 if ( preg_match( '/[\000-\010\016-\037\177]/', $value ) ) {
 768                         return '/* invalid control char */';
 769                 } elseif ( preg_match( '! expression | filter\s*: | accelerator\s*: | url\s*\( !ix', $value ) ) {
 770                         return '/* insecure input */';
 771                 }
 772                 return $value;
 773         }
 774
 775         static function cssDecodeCallback( $matches ) {
 776                 if ( $matches[1] !== '' ) {
 777                         // Line continuation
 778                         return '';
 779                 } elseif ( $matches[2] !== '' ) {
 780                         $char = codepointToUtf8( hexdec( $matches[2] ) );
 781                 } elseif ( $matches[3] !== '' ) {
 782                         $char = $matches[3];
 783                 } else {
 784                         $char = '\\';
 785                 }
 786                 if ( $char == "\n" || $char == '"' || $char == "'" || $char == '\\' ) {
 787                         // These characters need to be escaped in strings
 788                         // Clean up the escape sequence to avoid parsing errors by clients
 789                         return '\\' . dechex( ord( $char ) ) . ' ';
 790                 } else {
 791                         // Decode unnecessary escape
 792                         return $char;
 793                 }
 794         }
 795
 796         /**
 797         * Take an associative array of attribute name/value pairs
 798         * and generate a css style representing all the style-related
 799         * attributes. If there already a style attribute in the array,
 800         * it is also included in the value returned.
 801         */
 802         static function styleFromAttributes( $attributes ) {
 803                 $styles = array();
 804
 805                 foreach ( $attributes as $attribute => $value ) {
 806                         if ( $attribute == 'bgcolor' ) {
 807                                 $styles[] = "background-color: $value";
 808                         } else if ( $attribute == 'border' ) {
 809                                 $styles[] = "border-width: $value";
 810                         } else if ( $attribute == 'align' ) {
 811                                 $styles[] = "text-align: $value";
 812                         } else if ( $attribute == 'valign' ) {
 813                                 $styles[] = "vertical-align: $value";
 814                         } else if ( $attribute == 'width' ) {
 815                                 if ( preg_match( '/\d+/', $value ) === false ) {
 816                                       $value .= 'px';
 817                                 }
 818
 819                                 $styles[] = "width: $value";
 820                         } else if ( $attribute == 'height' ) {
 821                                 if ( preg_match( '/\d+/', $value ) === false ) {
 822                                       $value .= 'px';
 823                                 }
 824
 825                                 $styles[] = "height: $value";
 826                         } else if ( $attribute == 'nowrap' ) {
 827                                 if ( $value ) {
 828                                         $styles[] = "white-space: nowrap";
 829                                 }
 830                         }
 831                 }
 832
 833                 if ( isset( $attributes[ 'style' ] ) ) {
 834                         $styles[] = $attributes[ 'style' ];
 835                 }
 836
 837                 if ( !$styles ) return '';
 838                 else return implode( '; ', $styles );
 839         }
 840
 841         /**
 842          * Take a tag soup fragment listing an HTML element's attributes
 843          * and normalize it to well-formed XML, discarding unwanted attributes.
 844          * Output is safe for further wikitext processing, with escaping of
 845          * values that could trigger problems.
 846          *
 847          * - Normalizes attribute names to lowercase
 848          * - Discards attributes not on a whitelist for the given element
 849          * - Turns broken or invalid entities into plaintext
 850          * - Double-quotes all attribute values
 851          * - Attributes without values are given the name as attribute
 852          * - Double attributes are discarded
 853          * - Unsafe style attributes are discarded
 854          * - Prepends space if there are attributes.
 855          *
 856          * @param $text String
 857          * @param $element String
 858          * @param $defaults Array (optional) associative array of default attributes to splice in.
 859          *                      class and style attributes are combined. Otherwise, values from
 860          *                      $attributes take precedence over values from $defaults.
 861          * @return String
 862          */
 863         static function fixTagAttributes( $text, $element, $defaults = null ) {
 864                 if( trim( $text ) == '' ) {
 865                         return '';
 866                 }
 867
 868                 $decoded = Sanitizer::decodeTagAttributes( $text );
 869                 $stripped = Sanitizer::validateTagAttributes( $decoded, $element );
 870                 $attribs = Sanitizer::collapseTagAttributes( $stripped, $defaults );
 871
 872                 return $attribs;
 873         }
 874
 875         /**
 876          * Take an associative array or attribute name/value pairs
 877          * and collapses it to well-formed XML.
 878          * Does not filter attributes.
 879          * Output is safe for further wikitext processing, with escaping of
 880          * values that could trigger problems.
 881          *
 882          * - Double-quotes all attribute values
 883          * - Prepends space if there are attributes.
 884          *
 885          * @param $attributes Array is an associative array of attribute name/value pairs.
 886          *                      Assumed to be sanitized already.
 887          * @param $defaults Array (optional) associative array of default attributes to splice in.
 888          *                      class and style attributes are combined. Otherwise, values from
 889          *                      $attributes take precedence over values from $defaults.
 890          * @return String
 891          */
 892         static function collapseTagAttributes( $attributes, $defaults = null ) {
 893                 if ( $defaults ) {
 894                         foreach( $defaults as $attribute => $value ) {
 895                                 if ( isset( $attributes[ $attribute ] ) ) {
 896                                         if ( $attribute == 'class' ) {
 897                                                 $value .= ' '. $attributes[ $attribute ];
 898                                         } else if ( $attribute == 'style' ) {
 899                                                 $value .= '; ' . $attributes[ $attribute ];
 900                                         } else {
 901                                                 continue;
 902                                         }
 903                                 }
 904
 905                                 $attributes[ $attribute ] = $value;
 906                         }
 907                 }
 908
 909                 $chunks = array();
 910
 911                 foreach( $attributes as $attribute => $value ) {
 912                         $encAttribute = htmlspecialchars( $attribute );
 913                         $encValue = Sanitizer::safeEncodeAttribute( $value );
 914
 915                         $chunks[] = "$encAttribute=\"$encValue\"";
 916                 }
 917                 return count( $chunks ) ? ' ' . implode( ' ', $chunks ) : '';
 918         }
 919
 920         /**
 921          * Encode an attribute value for HTML output.
 922          * @param $text String
 923          * @return HTML-encoded text fragment
 924          */
 925         static function encodeAttribute( $text ) {
 926                 $encValue = htmlspecialchars( $text, ENT_QUOTES );
 927
 928                 // Whitespace is normalized during attribute decoding,
 929                 // so if we've been passed non-spaces we must encode them
 930                 // ahead of time or they won't be preserved.
 931                 $encValue = strtr( $encValue, array(
 932                         "\n" => '&#10;',
 933                         "\r" => '&#13;',
 934                         "\t" => '&#9;',
 935                 ) );
 936
 937                 return $encValue;
 938         }
 939
 940         /**
 941          * Encode an attribute value for HTML tags, with extra armoring
 942          * against further wiki processing.
 943          * @param $text String
 944          * @return HTML-encoded text fragment
 945          */
 946         static function safeEncodeAttribute( $text ) {
 947                 $encValue = Sanitizer::encodeAttribute( $text );
 948
 949                 # Templates and links may be expanded in later parsing,
 950                 # creating invalid or dangerous output. Suppress this.
 951                 $encValue = strtr( $encValue, array(
 952                         '<'    => '&lt;',   // This should never happen,
 953                         '>'    => '&gt;',   // we've received invalid input
 954                         '"'    => '&quot;', // which should have been escaped.
 955                         '{'    => '&#123;',
 956                         '['    => '&#91;',
 957                         "''"   => '&#39;&#39;',
 958                         'ISBN' => '&#73;SBN',
 959                         'RFC'  => '&#82;FC',
 960                         'PMID' => '&#80;MID',
 961                         '|'    => '&#124;',
 962                         '__'   => '&#95;_',
 963                 ) );
 964
 965                 # Stupid hack
 966                 $encValue = preg_replace_callback(
 967                         '/(' . wfUrlProtocols() . ')/',
 968                         array( 'Sanitizer', 'armorLinksCallback' ),
 969                         $encValue );
 970                 return $encValue;
 971         }
 972
 973         /**
 974          * Given a value, escape it so that it can be used in an id attribute and
 975          * return it.  This will use HTML5 validation if $wgExperimentalHtmlIds is
 976          * true, allowing anything but ASCII whitespace.  Otherwise it will use
 977          * HTML 4 rules, which means a narrow subset of ASCII, with bad characters
 978          * escaped with lots of dots.
 979          *
 980          * To ensure we don't have to bother escaping anything, we also strip ', ",
 981          * & even if $wgExperimentalIds is true.  TODO: Is this the best tactic?
 982          * We also strip # because it upsets IE6.
 983          *
 984          * @see http://www.w3.org/TR/html401/types.html#type-name Valid characters
 985          *                                                          in the id and
 986          *                                                          name attributes
 987          * @see http://www.w3.org/TR/html401/struct/links.html#h-12.2.3 Anchors with the id attribute
 988          * @see http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#the-id-attribute
 989          *   HTML5 definition of id attribute
 990          *
 991          * @param $id String: id to escape
 992          * @param $options Mixed: string or array of strings (default is array()):
 993          *   'noninitial': This is a non-initial fragment of an id, not a full id,
 994          *       so don't pay attention if the first character isn't valid at the
 995          *       beginning of an id.  Only matters if $wgExperimentalHtmlIds is
 996          *       false.
 997          *   'legacy': Behave the way the old HTML 4-based ID escaping worked even
 998          *       if $wgExperimentalHtmlIds is used, so we can generate extra
 999          *       anchors and links won't break.
1000          * @return String
1001          */
1002         static function escapeId( $id, $options = array() ) {
1003                 global $wgHtml5, $wgExperimentalHtmlIds;
1004                 $options = (array)$options;
1005
1006                 if ( $wgHtml5 && $wgExperimentalHtmlIds && !in_array( 'legacy', $options ) ) {
1007                         $id = Sanitizer::decodeCharReferences( $id );
1008                         $id = preg_replace( '/[ \t\n\r\f_\'"&#]+/', '_', $id );
1009                         $id = trim( $id, '_' );
1010                         if ( $id === '' ) {
1011                                 # Must have been all whitespace to start with.
1012                                 return '_';
1013                         } else {
1014                                 return $id;
1015                         }
1016                 }
1017
1018                 # HTML4-style escaping
1019                 static $replace = array(
1020                         '%3A' => ':',
1021                         '%' => '.'
1022                 );
1023
1024                 $id = urlencode( Sanitizer::decodeCharReferences( strtr( $id, ' ', '_' ) ) );
1025                 $id = str_replace( array_keys( $replace ), array_values( $replace ), $id );
1026
1027                 if ( !preg_match( '/^[a-zA-Z]/', $id )
1028                 && !in_array( 'noninitial', $options ) )  {
1029                         // Initial character must be a letter!
1030                         $id = "x$id";
1031                 }
1032                 return $id;
1033         }
1034
1035         /**
1036          * Given a value, escape it so that it can be used as a CSS class and
1037          * return it.
1038          *
1039          * @todo For extra validity, input should be validated UTF-8.
1040          *
1041          * @see http://www.w3.org/TR/CSS21/syndata.html Valid characters/format
1042          *
1043          * @param $class String
1044          * @return String
1045          */
1046         static function escapeClass( $class ) {
1047                 // Convert ugly stuff to underscores and kill underscores in ugly places
1048                 return rtrim(preg_replace(
1049                         array('/(^[0-9\\-])|[\\x00-\\x20!"#$%&\'()*+,.\\/:;<=>?@[\\]^`{|}~]|\\xC2\\xA0/','/_+/'),
1050                         '_',
1051                         $class ), '_');
1052         }
1053
1054         /**
1055          * Given HTML input, escape with htmlspecialchars but un-escape entites.
1056          * This allows (generally harmless) entities like &#160; to survive.
1057          *
1058          * @param $html String to escape
1059          * @return String: escaped input
1060          */
1061         static function escapeHtmlAllowEntities( $html ) {
1062                 # It seems wise to escape ' as well as ", as a matter of course.  Can't
1063                 # hurt.
1064                 $html = htmlspecialchars( $html, ENT_QUOTES );
1065                 $html = str_replace( '&amp;', '&', $html );
1066                 $html = Sanitizer::normalizeCharReferences( $html );
1067                 return $html;
1068         }
1069
1070         /**
1071          * Regex replace callback for armoring links against further processing.
1072          * @param $matches Array
1073          * @return string
1074          */
1075         private static function armorLinksCallback( $matches ) {
1076                 return str_replace( ':', '&#58;', $matches[1] );
1077         }
1078
1079         /**
1080          * Return an associative array of attribute names and values from
1081          * a partial tag string. Attribute names are forces to lowercase,
1082          * character references are decoded to UTF-8 text.
1083          *
1084          * @param $text String
1085          * @return Array
1086          */
1087         public static function decodeTagAttributes( $text ) {
1088                 if( trim( $text ) == '' ) {
1089                         return array();
1090                 }
1091
1092                 $attribs = array();
1093                 $pairs = array();
1094                 if( !preg_match_all(
1095                         MW_ATTRIBS_REGEX,
1096                         $text,
1097                         $pairs,
1098                         PREG_SET_ORDER ) ) {
1099                         return $attribs;
1100                 }
1101
1102                 foreach( $pairs as $set ) {
1103                         $attribute = strtolower( $set[1] );
1104                         $value = Sanitizer::getTagAttributeCallback( $set );
1105
1106                         // Normalize whitespace
1107                         $value = preg_replace( '/[\t\r\n ]+/', ' ', $value );
1108                         $value = trim( $value );
1109
1110                         // Decode character references
1111                         $attribs[$attribute] = Sanitizer::decodeCharReferences( $value );
1112                 }
1113                 return $attribs;
1114         }
1115
1116         /**
1117          * Pick the appropriate attribute value from a match set from the
1118          * MW_ATTRIBS_REGEX matches.
1119          *
1120          * @param $set Array
1121          * @return String
1122          */
1123         private static function getTagAttributeCallback( $set ) {
1124                 if( isset( $set[6] ) ) {
1125                         # Illegal #XXXXXX color with no quotes.
1126                         return $set[6];
1127                 } elseif( isset( $set[5] ) ) {
1128                         # No quotes.
1129                         return $set[5];
1130                 } elseif( isset( $set[4] ) ) {
1131                         # Single-quoted
1132                         return $set[4];
1133                 } elseif( isset( $set[3] ) ) {
1134                         # Double-quoted
1135                         return $set[3];
1136                 } elseif( !isset( $set[2] ) ) {
1137                         # In XHTML, attributes must have a value.
1138                         # For 'reduced' form, return explicitly the attribute name here.
1139                         return $set[1];
1140                 } else {
1141                         throw new MWException( "Tag conditions not met. This should never happen and is a bug." );
1142                 }
1143         }
1144
1145         /**
1146          * Normalize whitespace and character references in an XML source-
1147          * encoded text for an attribute value.
1148          *
1149          * See http://www.w3.org/TR/REC-xml/#AVNormalize for background,
1150          * but note that we're not returning the value, but are returning
1151          * XML source fragments that will be slapped into output.
1152          *
1153          * @param $text String
1154          * @return String
1155          */
1156         private static function normalizeAttributeValue( $text ) {
1157                 return str_replace( '"', '&quot;',
1158                         self::normalizeWhitespace(
1159                                 Sanitizer::normalizeCharReferences( $text ) ) );
1160         }
1161
1162         private static function normalizeWhitespace( $text ) {
1163                 return preg_replace(
1164                         '/\r\n|[\x20\x0d\x0a\x09]/',
1165                         ' ',
1166                         $text );
1167         }
1168
1169         /**
1170          * Normalizes whitespace in a section name, such as might be returned
1171          * by Parser::stripSectionName(), for use in the id's that are used for
1172          * section links.
1173          *
1174          * @param $section String
1175          * @return String
1176          */
1177         static function normalizeSectionNameWhitespace( $section ) {
1178                 return trim( preg_replace( '/[ _]+/', ' ', $section ) );
1179         }
1180
1181         /**
1182          * Ensure that any entities and character references are legal
1183          * for XML and XHTML specifically. Any stray bits will be
1184          * &amp;-escaped to result in a valid text fragment.
1185          *
1186          * a. any named char refs must be known in XHTML
1187          * b. any numeric char refs must be legal chars, not invalid or forbidden
1188          * c. use &#x, not &#X
1189          * d. fix or reject non-valid attributes
1190          *
1191          * @param $text String
1192          * @return String
1193          * @private
1194          */
1195         static function normalizeCharReferences( $text ) {
1196                 return preg_replace_callback(
1197                         MW_CHAR_REFS_REGEX,
1198                         array( 'Sanitizer', 'normalizeCharReferencesCallback' ),
1199                         $text );
1200         }
1201         /**
1202          * @param $matches String
1203          * @return String
1204          */
1205         static function normalizeCharReferencesCallback( $matches ) {
1206                 $ret = null;
1207                 if( $matches[1] != '' ) {
1208                         $ret = Sanitizer::normalizeEntity( $matches[1] );
1209                 } elseif( $matches[2] != '' ) {
1210                         $ret = Sanitizer::decCharReference( $matches[2] );
1211                 } elseif( $matches[3] != ''  ) {
1212                         $ret = Sanitizer::hexCharReference( $matches[3] );
1213                 } elseif( $matches[4] != '' ) {
1214                         $ret = Sanitizer::hexCharReference( $matches[4] );
1215                 }
1216                 if( is_null( $ret ) ) {
1217                         return htmlspecialchars( $matches[0] );
1218                 } else {
1219                         return $ret;
1220                 }
1221         }
1222
1223         /**
1224          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1225          * return the named entity reference as is. If the entity is a
1226          * MediaWiki-specific alias, returns the HTML equivalent. Otherwise,
1227          * returns HTML-escaped text of pseudo-entity source (eg &amp;foo;)
1228          *
1229          * @param $name String
1230          * @return String
1231          */
1232         static function normalizeEntity( $name ) {
1233                 global $wgHtmlEntities, $wgHtmlEntityAliases;
1234                 if ( isset( $wgHtmlEntityAliases[$name] ) ) {
1235                         return "&{$wgHtmlEntityAliases[$name]};";
1236                 } elseif( isset( $wgHtmlEntities[$name] ) ) {
1237                         return "&$name;";
1238                 } else {
1239                         return "&amp;$name;";
1240                 }
1241         }
1242
1243         static function decCharReference( $codepoint ) {
1244                 $point = intval( $codepoint );
1245                 if( Sanitizer::validateCodepoint( $point ) ) {
1246                         return sprintf( '&#%d;', $point );
1247                 } else {
1248                         return null;
1249                 }
1250         }
1251
1252         static function hexCharReference( $codepoint ) {
1253                 $point = hexdec( $codepoint );
1254                 if( Sanitizer::validateCodepoint( $point ) ) {
1255                         return sprintf( '&#x%x;', $point );
1256                 } else {
1257                         return null;
1258                 }
1259         }
1260
1261         /**
1262          * Returns true if a given Unicode codepoint is a valid character in XML.
1263          * @param $codepoint Integer
1264          * @return Boolean
1265          */
1266         private static function validateCodepoint( $codepoint ) {
1267                 return ($codepoint ==    0x09)
1268                         || ($codepoint ==    0x0a)
1269                         || ($codepoint ==    0x0d)
1270                         || ($codepoint >=    0x20 && $codepoint <=   0xd7ff)
1271                         || ($codepoint >=  0xe000 && $codepoint <=   0xfffd)
1272                         || ($codepoint >= 0x10000 && $codepoint <= 0x10ffff);
1273         }
1274
1275         /**
1276          * Decode any character references, numeric or named entities,
1277          * in the text and return a UTF-8 string.
1278          *
1279          * @param $text String
1280          * @return String
1281          */
1282         public static function decodeCharReferences( $text ) {
1283                 return preg_replace_callback(
1284                         MW_CHAR_REFS_REGEX,
1285                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1286                         $text );
1287         }
1288
1289         /**
1290          * Decode any character references, numeric or named entities,
1291          * in the next and normalize the resulting string. (bug 14952)
1292          *
1293          * This is useful for page titles, not for text to be displayed,
1294          * MediaWiki allows HTML entities to escape normalization as a feature.
1295          *
1296          * @param $text String (already normalized, containing entities)
1297          * @return String (still normalized, without entities)
1298          */
1299         public static function decodeCharReferencesAndNormalize( $text ) {
1300                 global $wgContLang;
1301                 $text = preg_replace_callback(
1302                         MW_CHAR_REFS_REGEX,
1303                         array( 'Sanitizer', 'decodeCharReferencesCallback' ),
1304                         $text, /* limit */ -1, $count );
1305
1306                 if ( $count ) {
1307                         return $wgContLang->normalize( $text );
1308                 } else {
1309                         return $text;
1310                 }
1311         }
1312
1313         /**
1314          * @param $matches String
1315          * @return String
1316          */
1317         static function decodeCharReferencesCallback( $matches ) {
1318                 if( $matches[1] != '' ) {
1319                         return Sanitizer::decodeEntity( $matches[1] );
1320                 } elseif( $matches[2] != '' ) {
1321                         return  Sanitizer::decodeChar( intval( $matches[2] ) );
1322                 } elseif( $matches[3] != ''  ) {
1323                         return  Sanitizer::decodeChar( hexdec( $matches[3] ) );
1324                 } elseif( $matches[4] != '' ) {
1325                         return  Sanitizer::decodeChar( hexdec( $matches[4] ) );
1326                 }
1327                 # Last case should be an ampersand by itself
1328                 return $matches[0];
1329         }
1330
1331         /**
1332          * Return UTF-8 string for a codepoint if that is a valid
1333          * character reference, otherwise U+FFFD REPLACEMENT CHARACTER.
1334          * @param $codepoint Integer
1335          * @return String
1336          * @private
1337          */
1338         static function decodeChar( $codepoint ) {
1339                 if( Sanitizer::validateCodepoint( $codepoint ) ) {
1340                         return codepointToUtf8( $codepoint );
1341                 } else {
1342                         return UTF8_REPLACEMENT;
1343                 }
1344         }
1345
1346         /**
1347          * If the named entity is defined in the HTML 4.0/XHTML 1.0 DTD,
1348          * return the UTF-8 encoding of that character. Otherwise, returns
1349          * pseudo-entity source (eg &foo;)
1350          *
1351          * @param $name Strings
1352          * @return String
1353          */
1354         static function decodeEntity( $name ) {
1355                 global $wgHtmlEntities, $wgHtmlEntityAliases;
1356                 if ( isset( $wgHtmlEntityAliases[$name] ) ) {
1357                         $name = $wgHtmlEntityAliases[$name];
1358                 }
1359                 if( isset( $wgHtmlEntities[$name] ) ) {
1360                         return codepointToUtf8( $wgHtmlEntities[$name] );
1361                 } else {
1362                         return "&$name;";
1363                 }
1364         }
1365
1366         /**
1367          * Fetch the whitelist of acceptable attributes for a given element name.
1368          *
1369          * @param $element String
1370          * @return Array
1371          */
1372         static function attributeWhitelist( $element ) {
1373                 static $list;
1374                 if( !isset( $list ) ) {
1375                         $list = Sanitizer::setupAttributeWhitelist();
1376                 }
1377                 return isset( $list[$element] )
1378                         ? $list[$element]
1379                         : array();
1380         }
1381
1382         /**
1383          * Foreach array key (an allowed HTML element), return an array
1384          * of allowed attributes
1385          * @return Array
1386          */
1387         static function setupAttributeWhitelist() {
1388                 global $wgAllowRdfaAttributes, $wgHtml5, $wgAllowMicrodataAttributes;
1389
1390                 $common = array( 'id', 'class', 'lang', 'dir', 'title', 'style' );
1391
1392                 if ( $wgAllowRdfaAttributes ) {
1393                         #RDFa attributes as specified in section 9 of http://www.w3.org/TR/2008/REC-rdfa-syntax-20081014
1394                         $common = array_merge( $common, array(
1395                             'about', 'property', 'resource', 'datatype', 'typeof',
1396                         ) );
1397                 }
1398
1399                 if ( $wgHtml5 && $wgAllowMicrodataAttributes ) {
1400                         # add HTML5 microdata tages as pecified by http://www.whatwg.org/specs/web-apps/current-work/multipage/microdata.html#the-microdata-model
1401                         $common = array_merge( $common, array(
1402                             'itemid', 'itemprop', 'itemref', 'itemscope', 'itemtype'
1403                         ) );
1404                 }
1405
1406                 $block = array_merge( $common, array( 'align' ) );
1407                 $tablealign = array( 'align', 'char', 'charoff', 'valign' );
1408                 $tablecell = array( 'abbr',
1409                                     'axis',
1410                                     'headers',
1411                                     'scope',
1412                                     'rowspan',
1413                                     'colspan',
1414                                     'nowrap', # deprecated
1415                                     'width',  # deprecated
1416                                     'height', # deprecated
1417                                     'bgcolor' # deprecated
1418                                     );
1419
1420                 # Numbers refer to sections in HTML 4.01 standard describing the element.
1421                 # See: http://www.w3.org/TR/html4/
1422                 $whitelist = array (
1423                         # 7.5.4
1424                         'div'        => $block,
1425                         'center'     => $common, # deprecated
1426                         'span'       => $block, # ??
1427
1428                         # 7.5.5
1429                         'h1'         => $block,
1430                         'h2'         => $block,
1431                         'h3'         => $block,
1432                         'h4'         => $block,
1433                         'h5'         => $block,
1434                         'h6'         => $block,
1435
1436                         # 7.5.6
1437                         # address
1438
1439                         # 8.2.4
1440                         # bdo
1441
1442                         # 9.2.1
1443                         'em'         => $common,
1444                         'strong'     => $common,
1445                         'cite'       => $common,
1446                         # dfn
1447                         'code'       => $common,
1448                         # samp
1449                         # kbd
1450                         'var'        => $common,
1451                         'abbr'       => $common,
1452                         # acronym
1453
1454                         # 9.2.2
1455                         'blockquote' => array_merge( $common, array( 'cite' ) ),
1456                         # q
1457
1458                         # 9.2.3
1459                         'sub'        => $common,
1460                         'sup'        => $common,
1461
1462                         # 9.3.1
1463                         'p'          => $block,
1464
1465                         # 9.3.2
1466                         'br'         => array( 'id', 'class', 'title', 'style', 'clear' ),
1467
1468                         # 9.3.4
1469                         'pre'        => array_merge( $common, array( 'width' ) ),
1470
1471                         # 9.4
1472                         'ins'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1473                         'del'        => array_merge( $common, array( 'cite', 'datetime' ) ),
1474
1475                         # 10.2
1476                         'ul'         => array_merge( $common, array( 'type' ) ),
1477                         'ol'         => array_merge( $common, array( 'type', 'start' ) ),
1478                         'li'         => array_merge( $common, array( 'type', 'value' ) ),
1479
1480                         # 10.3
1481                         'dl'         => $common,
1482                         'dd'         => $common,
1483                         'dt'         => $common,
1484
1485                         # 11.2.1
1486                         'table'      => array_merge( $common,
1487                                                                 array( 'summary', 'width', 'border', 'frame',
1488                                                                                 'rules', 'cellspacing', 'cellpadding',
1489                                                                                 'align', 'bgcolor',
1490                                                                 ) ),
1491
1492                         # 11.2.2
1493                         'caption'    => array_merge( $common, array( 'align' ) ),
1494
1495                         # 11.2.3
1496                         'thead'      => array_merge( $common, $tablealign ),
1497                         'tfoot'      => array_merge( $common, $tablealign ),
1498                         'tbody'      => array_merge( $common, $tablealign ),
1499
1500                         # 11.2.4
1501                         'colgroup'   => array_merge( $common, array( 'span', 'width' ), $tablealign ),
1502                         'col'        => array_merge( $common, array( 'span', 'width' ), $tablealign ),
1503
1504                         # 11.2.5
1505                         'tr'         => array_merge( $common, array( 'bgcolor' ), $tablealign ),
1506
1507                         # 11.2.6
1508                         'td'         => array_merge( $common, $tablecell, $tablealign ),
1509                         'th'         => array_merge( $common, $tablecell, $tablealign ),
1510
1511                         # 12.2 # NOTE: <a> is not allowed directly, but the attrib whitelist is used from the Parser object
1512                         'a'          => array_merge( $common, array( 'href', 'rel', 'rev' ) ), # rel/rev esp. for RDFa
1513
1514                         # 13.2
1515                         # Not usually allowed, but may be used for extension-style hooks
1516                         # such as <math> when it is rasterized, or if $wgAllowImageTag is
1517                         # true
1518                         'img'        => array_merge( $common, array( 'alt', 'src', 'width', 'height' ) ),
1519
1520                         # 15.2.1
1521                         'tt'         => $common,
1522                         'b'          => $common,
1523                         'i'          => $common,
1524                         'big'        => $common,
1525                         'small'      => $common,
1526                         'strike'     => $common,
1527                         's'          => $common,
1528                         'u'          => $common,
1529
1530                         # 15.2.2
1531                         'font'       => array_merge( $common, array( 'size', 'color', 'face' ) ),
1532                         # basefont
1533
1534                         # 15.3
1535                         'hr'         => array_merge( $common, array( 'noshade', 'size', 'width' ) ),
1536
1537                         # XHTML Ruby annotation text module, simple ruby only.
1538                         # http://www.w3c.org/TR/ruby/
1539                         'ruby'       => $common,
1540                         # rbc
1541                         # rtc
1542                         'rb'         => $common,
1543                         'rt'         => $common, #array_merge( $common, array( 'rbspan' ) ),
1544                         'rp'         => $common,
1545
1546                         # MathML root element, where used for extensions
1547                         # 'title' may not be 100% valid here; it's XHTML
1548                         # http://www.w3.org/TR/REC-MathML/
1549                         'math'       => array( 'class', 'style', 'id', 'title' ),
1550                         );
1551                 return $whitelist;
1552         }
1553
1554         /**
1555          * Take a fragment of (potentially invalid) HTML and return
1556          * a version with any tags removed, encoded as plain text.
1557          *
1558          * Warning: this return value must be further escaped for literal
1559          * inclusion in HTML output as of 1.10!
1560          *
1561          * @param $text String: HTML fragment
1562          * @return String
1563          */
1564         static function stripAllTags( $text ) {
1565                 # Actual <tags>
1566                 $text = StringUtils::delimiterReplace( '<', '>', '', $text );
1567
1568                 # Normalize &entities and whitespace
1569                 $text = self::decodeCharReferences( $text );
1570                 $text = self::normalizeWhitespace( $text );
1571
1572                 return $text;
1573         }
1574
1575         /**
1576          * Hack up a private DOCTYPE with HTML's standard entity declarations.
1577          * PHP 4 seemed to know these if you gave it an HTML doctype, but
1578          * PHP 5.1 doesn't.
1579          *
1580          * Use for passing XHTML fragments to PHP's XML parsing functions
1581          *
1582          * @return String
1583          */
1584         static function hackDocType() {
1585                 global $wgHtmlEntities;
1586                 $out = "<!DOCTYPE html [\n";
1587                 foreach( $wgHtmlEntities as $entity => $codepoint ) {
1588                         $out .= "<!ENTITY $entity \"&#$codepoint;\">";
1589                 }
1590                 $out .= "]>\n";
1591                 return $out;
1592         }
1593
1594         static function cleanUrl( $url ) {
1595                 # Normalize any HTML entities in input. They will be
1596                 # re-escaped by makeExternalLink().
1597                 $url = Sanitizer::decodeCharReferences( $url );
1598
1599                 # Escape any control characters introduced by the above step
1600                 $url = preg_replace( '/[\][<>"\\x00-\\x20\\x7F\|]/e', "urlencode('\\0')", $url );
1601
1602                 # Validate hostname portion
1603                 $matches = array();
1604                 if( preg_match( '!^([^:]+:)(//[^/]+)?(.*)$!iD', $url, $matches ) ) {
1605                         list( /* $whole */, $protocol, $host, $rest ) = $matches;
1606
1607                         // Characters that will be ignored in IDNs.
1608                         // http://tools.ietf.org/html/3454#section-3.1
1609                         // Strip them before further processing so blacklists and such work.
1610                         $strip = "/
1611                                 \\s|          # general whitespace
1612                                 \xc2\xad|     # 00ad SOFT HYPHEN
1613                                 \xe1\xa0\x86| # 1806 MONGOLIAN TODO SOFT HYPHEN
1614                                 \xe2\x80\x8b| # 200b ZERO WIDTH SPACE
1615                                 \xe2\x81\xa0| # 2060 WORD JOINER
1616                                 \xef\xbb\xbf| # feff ZERO WIDTH NO-BREAK SPACE
1617                                 \xcd\x8f|     # 034f COMBINING GRAPHEME JOINER
1618                                 \xe1\xa0\x8b| # 180b MONGOLIAN FREE VARIATION SELECTOR ONE
1619                                 \xe1\xa0\x8c| # 180c MONGOLIAN FREE VARIATION SELECTOR TWO
1620                                 \xe1\xa0\x8d| # 180d MONGOLIAN FREE VARIATION SELECTOR THREE
1621                                 \xe2\x80\x8c| # 200c ZERO WIDTH NON-JOINER
1622                                 \xe2\x80\x8d| # 200d ZERO WIDTH JOINER
1623                                 [\xef\xb8\x80-\xef\xb8\x8f] # fe00-fe00f VARIATION SELECTOR-1-16
1624                                 /xuD";
1625
1626                         $host = preg_replace( $strip, '', $host );
1627
1628                         // @todo Fixme: validate hostnames here
1629
1630                         return $protocol . $host . $rest;
1631                 } else {
1632                         return $url;
1633                 }
1634         }
1635
1636 }