thumb.php

   1 <?php
   2 /**
   3  * PHP script to stream out an image thumbnail.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Media
  22  */
  23
  24 define( 'MW_NO_OUTPUT_COMPRESSION', 1 );
  25 require __DIR__ . '/includes/WebStart.php';
  26
  27 // Don't use fancy MIME detection, just check the file extension for jpg/gif/png
  28 $wgTrivialMimeDetection = true;
  29
  30 if ( defined( 'THUMB_HANDLER' ) ) {
  31         // Called from thumb_handler.php via 404; extract params from the URI...
  32         wfThumbHandle404();
  33 } else {
  34         // Called directly, use $_GET params
  35         wfStreamThumb( $_GET );
  36 }
  37
  38 $mediawiki = new MediaWiki();
  39 $mediawiki->doPostOutputShutdown( 'fast' );
  40
  41 // --------------------------------------------------------------------------
  42
  43 /**
  44  * Handle a thumbnail request via thumbnail file URL
  45  *
  46  * @return void
  47  */
  48 function wfThumbHandle404() {
  49         global $wgArticlePath;
  50
  51         # Set action base paths so that WebRequest::getPathInfo()
  52         # recognizes the "X" as the 'title' in ../thumb_handler.php/X urls.
  53         # Note: If Custom per-extension repo paths are set, this may break.
  54         $repo = RepoGroup::singleton()->getLocalRepo();
  55         $oldArticlePath = $wgArticlePath;
  56         $wgArticlePath = $repo->getZoneUrl( 'thumb' ) . '/$1';
  57
  58         $matches = WebRequest::getPathInfo();
  59
  60         $wgArticlePath = $oldArticlePath;
  61
  62         if ( !isset( $matches['title'] ) ) {
  63                 wfThumbError( 404, 'Could not determine the name of the requested thumbnail.' );
  64                 return;
  65         }
  66
  67         $params = wfExtractThumbRequestInfo( $matches['title'] ); // basic wiki URL param extracting
  68         if ( $params == null ) {
  69                 wfThumbError( 400, 'The specified thumbnail parameters are not recognized.' );
  70                 return;
  71         }
  72
  73         wfStreamThumb( $params ); // stream the thumbnail
  74 }
  75
  76 /**
  77  * Stream a thumbnail specified by parameters
  78  *
  79  * @param array $params List of thumbnailing parameters. In addition to parameters
  80  *  passed to the MediaHandler, this may also includes the keys:
  81  *   f (for filename), archived (if archived file), temp (if temp file),
  82  *   w (alias for width), p (alias for page), r (ignored; historical),
  83  *   rel404 (path for render on 404 to verify hash path correct),
  84  *   thumbName (thumbnail name to potentially extract more parameters from
  85  *   e.g. 'lossy-page1-120px-Foo.tiff' would add page, lossy and width
  86  *   to the parameters)
  87  * @return void
  88  */
  89 function wfStreamThumb( array $params ) {
  90         global $wgVaryOnXFP;
  91
  92         $headers = array(); // HTTP headers to send
  93
  94         $fileName = isset( $params['f'] ) ? $params['f'] : '';
  95
  96         // Backwards compatibility parameters
  97         if ( isset( $params['w'] ) ) {
  98                 $params['width'] = $params['w'];
  99                 unset( $params['w'] );
 100         }
 101         if ( isset( $params['width'] ) && substr( $params['width'], -2 ) == 'px' ) {
 102                 // strip the px (pixel) suffix, if found
 103                 $params['width'] = substr( $params['width'], 0, -2 );
 104         }
 105         if ( isset( $params['p'] ) ) {
 106                 $params['page'] = $params['p'];
 107         }
 108
 109         // Is this a thumb of an archived file?
 110         $isOld = ( isset( $params['archived'] ) && $params['archived'] );
 111         unset( $params['archived'] ); // handlers don't care
 112
 113         // Is this a thumb of a temp file?
 114         $isTemp = ( isset( $params['temp'] ) && $params['temp'] );
 115         unset( $params['temp'] ); // handlers don't care
 116
 117         // Some basic input validation
 118         $fileName = strtr( $fileName, '\\/', '__' );
 119
 120         // Actually fetch the image. Method depends on whether it is archived or not.
 121         if ( $isTemp ) {
 122                 $repo = RepoGroup::singleton()->getLocalRepo()->getTempRepo();
 123                 $img = new UnregisteredLocalFile( null, $repo,
 124                         # Temp files are hashed based on the name without the timestamp.
 125                         # The thumbnails will be hashed based on the entire name however.
 126                         # @todo fix this convention to actually be reasonable.
 127                         $repo->getZonePath( 'public' ) . '/' . $repo->getTempHashPath( $fileName ) . $fileName
 128                 );
 129         } elseif ( $isOld ) {
 130                 // Format is <timestamp>!<name>
 131                 $bits = explode( '!', $fileName, 2 );
 132                 if ( count( $bits ) != 2 ) {
 133                         wfThumbError( 404, wfMessage( 'badtitletext' )->parse() );
 134                         return;
 135                 }
 136                 $title = Title::makeTitleSafe( NS_FILE, $bits[1] );
 137                 if ( !$title ) {
 138                         wfThumbError( 404, wfMessage( 'badtitletext' )->parse() );
 139                         return;
 140                 }
 141                 $img = RepoGroup::singleton()->getLocalRepo()->newFromArchiveName( $title, $fileName );
 142         } else {
 143                 $img = wfLocalFile( $fileName );
 144         }
 145
 146         // Check the source file title
 147         if ( !$img ) {
 148                 wfThumbError( 404, wfMessage( 'badtitletext' )->parse() );
 149                 return;
 150         }
 151
 152         // Check permissions if there are read restrictions
 153         $varyHeader = array();
 154         if ( !in_array( 'read', User::getGroupPermissions( array( '*' ) ), true ) ) {
 155                 if ( !$img->getTitle() || !$img->getTitle()->userCan( 'read' ) ) {
 156                         wfThumbError( 403, 'Access denied. You do not have permission to access ' .
 157                                 'the source file.' );
 158                         return;
 159                 }
 160                 $headers[] = 'Cache-Control: private';
 161                 $varyHeader[] = 'Cookie';
 162         }
 163
 164         // Check if the file is hidden
 165         if ( $img->isDeleted( File::DELETED_FILE ) ) {
 166                 wfThumbErrorText( 404, "The source file '$fileName' does not exist." );
 167                 return;
 168         }
 169
 170         // Do rendering parameters extraction from thumbnail name.
 171         if ( isset( $params['thumbName'] ) ) {
 172                 $params = wfExtractThumbParams( $img, $params );
 173         }
 174         if ( $params == null ) {
 175                 wfThumbError( 400, 'The specified thumbnail parameters are not recognized.' );
 176                 return;
 177         }
 178
 179         // Check the source file storage path
 180         if ( !$img->exists() ) {
 181                 $redirectedLocation = false;
 182                 if ( !$isTemp ) {
 183                         // Check for file redirect
 184                         // Since redirects are associated with pages, not versions of files,
 185                         // we look for the most current version to see if its a redirect.
 186                         $possRedirFile = RepoGroup::singleton()->getLocalRepo()->findFile( $img->getName() );
 187                         if ( $possRedirFile && !is_null( $possRedirFile->getRedirected() ) ) {
 188                                 $redirTarget = $possRedirFile->getName();
 189                                 $targetFile = wfLocalFile( Title::makeTitleSafe( NS_FILE, $redirTarget ) );
 190                                 if ( $targetFile->exists() ) {
 191                                         $newThumbName = $targetFile->thumbName( $params );
 192                                         if ( $isOld ) {
 193                                                 /** @var array $bits */
 194                                                 $newThumbUrl = $targetFile->getArchiveThumbUrl(
 195                                                         $bits[0] . '!' . $targetFile->getName(), $newThumbName );
 196                                         } else {
 197                                                 $newThumbUrl = $targetFile->getThumbUrl( $newThumbName );
 198                                         }
 199                                         $redirectedLocation = wfExpandUrl( $newThumbUrl, PROTO_CURRENT );
 200                                 }
 201                         }
 202                 }
 203
 204                 if ( $redirectedLocation ) {
 205                         // File has been moved. Give redirect.
 206                         $response = RequestContext::getMain()->getRequest()->response();
 207                         $response->statusHeader( 302 );
 208                         $response->header( 'Location: ' . $redirectedLocation );
 209                         $response->header( 'Expires: ' .
 210                                 gmdate( 'D, d M Y H:i:s', time() + 12 * 3600 ) . ' GMT' );
 211                         if ( $wgVaryOnXFP ) {
 212                                 $varyHeader[] = 'X-Forwarded-Proto';
 213                         }
 214                         if ( count( $varyHeader ) ) {
 215                                 $response->header( 'Vary: ' . implode( ', ', $varyHeader ) );
 216                         }
 217                         $response->header( 'Content-Length: 0' );
 218                         return;
 219                 }
 220
 221                 // If its not a redirect that has a target as a local file, give 404.
 222                 wfThumbErrorText( 404, "The source file '$fileName' does not exist." );
 223                 return;
 224         } elseif ( $img->getPath() === false ) {
 225                 wfThumbErrorText( 400, "The source file '$fileName' is not locally accessible." );
 226                 return;
 227         }
 228
 229         // Check IMS against the source file
 230         // This means that clients can keep a cached copy even after it has been deleted on the server
 231         if ( !empty( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ) {
 232                 // Fix IE brokenness
 233                 $imsString = preg_replace( '/;.*$/', '', $_SERVER["HTTP_IF_MODIFIED_SINCE"] );
 234                 // Calculate time
 235                 MediaWiki\suppressWarnings();
 236                 $imsUnix = strtotime( $imsString );
 237                 MediaWiki\restoreWarnings();
 238                 if ( wfTimestamp( TS_UNIX, $img->getTimestamp() ) <= $imsUnix ) {
 239                         HttpStatus::header( 304 );
 240                         return;
 241                 }
 242         }
 243
 244         $rel404 = isset( $params['rel404'] ) ? $params['rel404'] : null;
 245         unset( $params['r'] ); // ignore 'r' because we unconditionally pass File::RENDER
 246         unset( $params['f'] ); // We're done with 'f' parameter.
 247         unset( $params['rel404'] ); // moved to $rel404
 248
 249         // Get the normalized thumbnail name from the parameters...
 250         try {
 251                 $thumbName = $img->thumbName( $params );
 252                 if ( !strlen( $thumbName ) ) { // invalid params?
 253                         throw new MediaTransformInvalidParametersException(
 254                                 'Empty return from File::thumbName'
 255                         );
 256                 }
 257                 $thumbName2 = $img->thumbName( $params, File::THUMB_FULL_NAME ); // b/c; "long" style
 258         } catch ( MediaTransformInvalidParametersException $e ) {
 259                 wfThumbError(
 260                         400,
 261                         'The specified thumbnail parameters are not valid: ' . $e->getMessage()
 262                 );
 263                 return;
 264         } catch ( MWException $e ) {
 265                 wfThumbError( 500, $e->getHTML() );
 266                 return;
 267         }
 268
 269         // For 404 handled thumbnails, we only use the base name of the URI
 270         // for the thumb params and the parent directory for the source file name.
 271         // Check that the zone relative path matches up so squid caches won't pick
 272         // up thumbs that would not be purged on source file deletion (bug 34231).
 273         if ( $rel404 !== null ) { // thumbnail was handled via 404
 274                 if ( rawurldecode( $rel404 ) === $img->getThumbRel( $thumbName ) ) {
 275                         // Request for the canonical thumbnail name
 276                 } elseif ( rawurldecode( $rel404 ) === $img->getThumbRel( $thumbName2 ) ) {
 277                         // Request for the "long" thumbnail name; redirect to canonical name
 278                         $response = RequestContext::getMain()->getRequest()->response();
 279                         $response->statusHeader( 301 );
 280                         $response->header( 'Location: ' .
 281                                 wfExpandUrl( $img->getThumbUrl( $thumbName ), PROTO_CURRENT ) );
 282                         $response->header( 'Expires: ' .
 283                                 gmdate( 'D, d M Y H:i:s', time() + 7 * 86400 ) . ' GMT' );
 284                         if ( $wgVaryOnXFP ) {
 285                                 $varyHeader[] = 'X-Forwarded-Proto';
 286                         }
 287                         if ( count( $varyHeader ) ) {
 288                                 $response->header( 'Vary: ' . implode( ', ', $varyHeader ) );
 289                         }
 290                         return;
 291                 } else {
 292                         wfThumbErrorText( 404, "The given path of the specified thumbnail is incorrect;
 293                                 expected '" . $img->getThumbRel( $thumbName ) . "' but got '" .
 294                                 rawurldecode( $rel404 ) . "'." );
 295                         return;
 296                 }
 297         }
 298
 299         $dispositionType = isset( $params['download'] ) ? 'attachment' : 'inline';
 300
 301         // Suggest a good name for users downloading this thumbnail
 302         $headers[] =
 303                 "Content-Disposition: {$img->getThumbDisposition( $thumbName, $dispositionType )}";
 304
 305         if ( count( $varyHeader ) ) {
 306                 $headers[] = 'Vary: ' . implode( ', ', $varyHeader );
 307         }
 308
 309         // Stream the file if it exists already...
 310         $thumbPath = $img->getThumbPath( $thumbName );
 311         if ( $img->getRepo()->fileExists( $thumbPath ) ) {
 312                 $starttime = microtime( true );
 313                 $success = $img->getRepo()->streamFile( $thumbPath, $headers );
 314                 $streamtime = microtime( true ) - $starttime;
 315
 316                 if ( !$success ) {
 317                         wfThumbError( 500, 'Could not stream the file' );
 318                 } else {
 319                         RequestContext::getMain()->getStats()->timing( 'media.thumbnail.stream', $streamtime );
 320                 }
 321                 return;
 322         }
 323
 324         $user = RequestContext::getMain()->getUser();
 325         if ( !wfThumbIsStandard( $img, $params ) && $user->pingLimiter( 'renderfile-nonstandard' ) ) {
 326                 wfThumbError( 429, wfMessage( 'actionthrottledtext' )->parse() );
 327                 return;
 328         } elseif ( $user->pingLimiter( 'renderfile' ) ) {
 329                 wfThumbError( 429, wfMessage( 'actionthrottledtext' )->parse() );
 330                 return;
 331         }
 332
 333         list( $thumb, $errorMsg ) = wfGenerateThumbnail( $img, $params, $thumbName, $thumbPath );
 334
 335         /** @var MediaTransformOutput|MediaTransformError|bool $thumb */
 336
 337         // Check for thumbnail generation errors...
 338         $msg = wfMessage( 'thumbnail_error' );
 339         $errorCode = 500;
 340         if ( !$thumb ) {
 341                 $errorMsg = $errorMsg ?: $msg->rawParams( 'File::transform() returned false' )->escaped();
 342                 if ( $errorMsg instanceof MessageSpecifier &&
 343                         $errorMsg->getKey() === 'thumbnail_image-failure-limit'
 344                 ) {
 345                         $errorCode = 429;
 346                 }
 347         } elseif ( $thumb->isError() ) {
 348                 $errorMsg = $thumb->getHtmlMsg();
 349         } elseif ( !$thumb->hasFile() ) {
 350                 $errorMsg = $msg->rawParams( 'No path supplied in thumbnail object' )->escaped();
 351         } elseif ( $thumb->fileIsSource() ) {
 352                 $errorMsg = $msg
 353                         ->rawParams( 'Image was not scaled, is the requested width bigger than the source?' )
 354                         ->escaped();
 355                 $errorCode = 400;
 356         }
 357
 358         if ( $errorMsg !== false ) {
 359                 wfThumbError( $errorCode, $errorMsg );
 360         } else {
 361                 // Stream the file if there were no errors
 362                 $success = $thumb->streamFile( $headers );
 363                 if ( !$success ) {
 364                         wfThumbError( 500, 'Could not stream the file' );
 365                 }
 366         }
 367 }
 368
 369 /**
 370  * Actually try to generate a new thumbnail
 371  *
 372  * @param File $file
 373  * @param array $params
 374  * @param string $thumbName
 375  * @param string $thumbPath
 376  * @return array (MediaTransformOutput|bool, string|bool error message HTML)
 377  */
 378 function wfGenerateThumbnail( File $file, array $params, $thumbName, $thumbPath ) {
 379         global $wgMemc, $wgAttemptFailureEpoch;
 380
 381         $key = wfMemcKey( 'attempt-failures', $wgAttemptFailureEpoch,
 382                 $file->getRepo()->getName(), $file->getSha1(), md5( $thumbName ) );
 383
 384         // Check if this file keeps failing to render
 385         if ( $wgMemc->get( $key ) >= 4 ) {
 386                 return array( false, wfMessage( 'thumbnail_image-failure-limit', 4 ) );
 387         }
 388
 389         $done = false;
 390         // Record failures on PHP fatals in addition to caching exceptions
 391         register_shutdown_function( function () use ( &$done, $key ) {
 392                 if ( !$done ) { // transform() gave a fatal
 393                         global $wgMemc;
 394                         // Randomize TTL to reduce stampedes
 395                         $wgMemc->incrWithInit( $key, 3600 + mt_rand( 0, 300 ) );
 396                 }
 397         } );
 398
 399         $thumb = false;
 400         $errorHtml = false;
 401
 402         // guard thumbnail rendering with PoolCounter to avoid stampedes
 403         // expensive files use a separate PoolCounter config so it is possible
 404         // to set up a global limit on them
 405         if ( $file->isExpensiveToThumbnail() ) {
 406                 $poolCounterType = 'FileRenderExpensive';
 407         } else {
 408                 $poolCounterType = 'FileRender';
 409         }
 410
 411         // Thumbnail isn't already there, so create the new thumbnail...
 412         try {
 413                 $work = new PoolCounterWorkViaCallback( $poolCounterType, sha1( $file->getName() ),
 414                         array(
 415                                 'doWork' => function () use ( $file, $params ) {
 416                                         return $file->transform( $params, File::RENDER_NOW );
 417                                 },
 418                                 'getCachedWork' => function () use ( $file, $params, $thumbPath ) {
 419                                         // If the worker that finished made this thumbnail then use it.
 420                                         // Otherwise, it probably made a different thumbnail for this file.
 421                                         return $file->getRepo()->fileExists( $thumbPath )
 422                                                 ? $file->transform( $params, File::RENDER_NOW )
 423                                                 : false; // retry once more in exclusive mode
 424                                 },
 425                                 'fallback' => function () {
 426                                         return wfMessage( 'generic-pool-error' )->parse();
 427                                 },
 428                                 'error' => function ( Status $status ) {
 429                                         return $status->getHTML();
 430                                 }
 431                         )
 432                 );
 433                 $result = $work->execute();
 434                 if ( $result instanceof MediaTransformOutput ) {
 435                         $thumb = $result;
 436                 } elseif ( is_string( $result ) ) { // error
 437                         $errorHtml = $result;
 438                 }
 439         } catch ( Exception $e ) {
 440                 // Tried to select a page on a non-paged file?
 441         }
 442
 443         /** @noinspection PhpUnusedLocalVariableInspection */
 444         $done = true; // no PHP fatal occured
 445
 446         if ( !$thumb || $thumb->isError() ) {
 447                 // Randomize TTL to reduce stampedes
 448                 $wgMemc->incrWithInit( $key, 3600 + mt_rand( 0, 300 ) );
 449         }
 450
 451         return array( $thumb, $errorHtml );
 452 }
 453
 454 /**
 455  * Convert pathinfo type parameter, into normal request parameters
 456  *
 457  * So for example, if the request was redirected from
 458  * /w/images/thumb/a/ab/Foo.png/120px-Foo.png. The $thumbRel parameter
 459  * of this function would be set to "a/ab/Foo.png/120px-Foo.png".
 460  * This method is responsible for turning that into an array
 461  * with the folowing keys:
 462  *  * f => the filename (Foo.png)
 463  *  * rel404 => the whole thing (a/ab/Foo.png/120px-Foo.png)
 464  *  * archived => 1 (If the request is for an archived thumb)
 465  *  * temp => 1 (If the file is in the "temporary" zone)
 466  *  * thumbName => the thumbnail name, including parameters (120px-Foo.png)
 467  *
 468  * Transform specific parameters are set later via wfExtractThumbParams().
 469  *
 470  * @param string $thumbRel Thumbnail path relative to the thumb zone
 471  * @return array|null Associative params array or null
 472  */
 473 function wfExtractThumbRequestInfo( $thumbRel ) {
 474         $repo = RepoGroup::singleton()->getLocalRepo();
 475
 476         $hashDirReg = $subdirReg = '';
 477         $hashLevels = $repo->getHashLevels();
 478         for ( $i = 0; $i < $hashLevels; $i++ ) {
 479                 $subdirReg .= '[0-9a-f]';
 480                 $hashDirReg .= "$subdirReg/";
 481         }
 482
 483         // Check if this is a thumbnail of an original in the local file repo
 484         if ( preg_match( "!^((archive/)?$hashDirReg([^/]*)/([^/]*))$!", $thumbRel, $m ) ) {
 485                 list( /*all*/, $rel, $archOrTemp, $filename, $thumbname ) = $m;
 486         // Check if this is a thumbnail of an temp file in the local file repo
 487         } elseif ( preg_match( "!^(temp/)($hashDirReg([^/]*)/([^/]*))$!", $thumbRel, $m ) ) {
 488                 list( /*all*/, $archOrTemp, $rel, $filename, $thumbname ) = $m;
 489         } else {
 490                 return null; // not a valid looking thumbnail request
 491         }
 492
 493         $params = array( 'f' => $filename, 'rel404' => $rel );
 494         if ( $archOrTemp === 'archive/' ) {
 495                 $params['archived'] = 1;
 496         } elseif ( $archOrTemp === 'temp/' ) {
 497                 $params['temp'] = 1;
 498         }
 499
 500         $params['thumbName'] = $thumbname;
 501         return $params;
 502 }
 503
 504 /**
 505  * Convert a thumbnail name (122px-foo.png) to parameters, using
 506  * file handler.
 507  *
 508  * @param File $file File object for file in question
 509  * @param array $params Array of parameters so far
 510  * @return array Parameters array with more parameters
 511  */
 512 function wfExtractThumbParams( $file, $params ) {
 513         if ( !isset( $params['thumbName'] ) ) {
 514                 throw new InvalidArgumentException( "No thumbnail name passed to wfExtractThumbParams" );
 515         }
 516
 517         $thumbname = $params['thumbName'];
 518         unset( $params['thumbName'] );
 519
 520         // Do the hook first for older extensions that rely on it.
 521         if ( !Hooks::run( 'ExtractThumbParameters', array( $thumbname, &$params ) ) ) {
 522                 // Check hooks if parameters can be extracted
 523                 // Hooks return false if they manage to *resolve* the parameters
 524                 // This hook should be considered deprecated
 525                 wfDeprecated( 'ExtractThumbParameters', '1.22' );
 526                 return $params; // valid thumbnail URL (via extension or config)
 527         }
 528
 529         // FIXME: Files in the temp zone don't set a MIME type, which means
 530         // they don't have a handler. Which means we can't parse the param
 531         // string. However, not a big issue as what good is a param string
 532         // if you have no handler to make use of the param string and
 533         // actually generate the thumbnail.
 534         $handler = $file->getHandler();
 535
 536         // Based on UploadStash::parseKey
 537         $fileNamePos = strrpos( $thumbname, $params['f'] );
 538         if ( $fileNamePos === false ) {
 539                 // Maybe using a short filename? (see FileRepo::nameForThumb)
 540                 $fileNamePos = strrpos( $thumbname, 'thumbnail' );
 541         }
 542
 543         if ( $handler && $fileNamePos !== false ) {
 544                 $paramString = substr( $thumbname, 0, $fileNamePos - 1 );
 545                 $extraParams = $handler->parseParamString( $paramString );
 546                 if ( $extraParams !== false ) {
 547                         return $params + $extraParams;
 548                 }
 549         }
 550
 551         // As a last ditch fallback, use the traditional common parameters
 552         if ( preg_match( '!^(page(\d*)-)*(\d*)px-[^/]*$!', $thumbname, $matches ) ) {
 553                 list( /* all */, /* pagefull */, $pagenum, $size ) = $matches;
 554                 $params['width'] = $size;
 555                 if ( $pagenum ) {
 556                         $params['page'] = $pagenum;
 557                 }
 558                 return $params; // valid thumbnail URL
 559         }
 560         return null;
 561 }
 562
 563
 564 /**
 565  * Output a thumbnail generation error message
 566  *
 567  * @param int $status
 568  * @param string $msgText Plain text (will be html escaped)
 569  * @return void
 570  */
 571 function wfThumbErrorText( $status, $msgText ) {
 572         wfThumbError( $status, htmlspecialchars( $msgText ) );
 573 }
 574
 575 /**
 576  * Output a thumbnail generation error message
 577  *
 578  * @param int $status
 579  * @param string $msgHtml HTML
 580  * @return void
 581  */
 582 function wfThumbError( $status, $msgHtml ) {
 583         global $wgShowHostnames;
 584
 585         header( 'Cache-Control: no-cache' );
 586         header( 'Content-Type: text/html; charset=utf-8' );
 587         if ( $status == 400 || $status == 404 || $status == 429 ) {
 588                 HttpStatus::header( $status );
 589         } elseif ( $status == 403 ) {
 590                 HttpStatus::header( 403 );
 591                 header( 'Vary: Cookie' );
 592         } else {
 593                 HttpStatus::header( 500 );
 594         }
 595         if ( $wgShowHostnames ) {
 596                 header( 'X-MW-Thumbnail-Renderer: ' . wfHostname() );
 597                 $url = htmlspecialchars(
 598                         isset( $_SERVER['REQUEST_URI'] ) ? $_SERVER['REQUEST_URI'] : ''
 599                 );
 600                 $hostname = htmlspecialchars( wfHostname() );
 601                 $debug = "<!-- $url -->\n<!-- $hostname -->\n";
 602         } else {
 603                 $debug = '';
 604         }
 605         $content = <<<EOT
 606 <!DOCTYPE html>
 607 <html><head>
 608 <meta charset="UTF-8" />
 609 <title>Error generating thumbnail</title>
 610 </head>
 611 <body>
 612 <h1>Error generating thumbnail</h1>
 613 <p>
 614 $msgHtml
 615 </p>
 616 $debug
 617 </body>
 618 </html>
 619
 620 EOT;
 621         header( 'Content-Length: ' . strlen( $content ) );
 622         echo $content;
 623 }