first commit

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diff --git a/www/wiki/thumb.php b/www/wiki/thumb.php
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--- /dev/null
+++ b/www/wiki/thumb.php
@@ -0,0 +1,677 @@
+<?php
+/**
+ * PHP script to stream out an image thumbnail.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ * @ingroup Media
+ */
+
+use MediaWiki\Logger\LoggerFactory;
+use MediaWiki\MediaWikiServices;
+
+define( 'MW_NO_OUTPUT_COMPRESSION', 1 );
+require __DIR__ . '/includes/WebStart.php';
+
+// Don't use fancy MIME detection, just check the file extension for jpg/gif/png
+$wgTrivialMimeDetection = true;
+
+if ( defined( 'THUMB_HANDLER' ) ) {
+	// Called from thumb_handler.php via 404; extract params from the URI...
+	wfThumbHandle404();
+} else {
+	// Called directly, use $_GET params
+	wfStreamThumb( $_GET );
+}
+
+$mediawiki = new MediaWiki();
+$mediawiki->doPostOutputShutdown( 'fast' );
+
+// --------------------------------------------------------------------------
+
+/**
+ * Handle a thumbnail request via thumbnail file URL
+ *
+ * @return void
+ */
+function wfThumbHandle404() {
+	global $wgArticlePath;
+
+	# Set action base paths so that WebRequest::getPathInfo()
+	# recognizes the "X" as the 'title' in ../thumb_handler.php/X urls.
+	# Note: If Custom per-extension repo paths are set, this may break.
+	$repo = RepoGroup::singleton()->getLocalRepo();
+	$oldArticlePath = $wgArticlePath;
+	$wgArticlePath = $repo->getZoneUrl( 'thumb' ) . '/$1';
+
+	$matches = WebRequest::getPathInfo();
+
+	$wgArticlePath = $oldArticlePath;
+
+	if ( !isset( $matches['title'] ) ) {
+		wfThumbError( 404, 'Could not determine the name of the requested thumbnail.' );
+		return;
+	}
+
+	$params = wfExtractThumbRequestInfo( $matches['title'] ); // basic wiki URL param extracting
+	if ( $params == null ) {
+		wfThumbError( 400, 'The specified thumbnail parameters are not recognized.' );
+		return;
+	}
+
+	wfStreamThumb( $params ); // stream the thumbnail
+}
+
+/**
+ * Stream a thumbnail specified by parameters
+ *
+ * @param array $params List of thumbnailing parameters. In addition to parameters
+ *  passed to the MediaHandler, this may also includes the keys:
+ *   f (for filename), archived (if archived file), temp (if temp file),
+ *   w (alias for width), p (alias for page), r (ignored; historical),
+ *   rel404 (path for render on 404 to verify hash path correct),
+ *   thumbName (thumbnail name to potentially extract more parameters from
+ *   e.g. 'lossy-page1-120px-Foo.tiff' would add page, lossy and width
+ *   to the parameters)
+ * @return void
+ */
+function wfStreamThumb( array $params ) {
+	global $wgVaryOnXFP;
+
+	$headers = []; // HTTP headers to send
+
+	$fileName = isset( $params['f'] ) ? $params['f'] : '';
+
+	// Backwards compatibility parameters
+	if ( isset( $params['w'] ) ) {
+		$params['width'] = $params['w'];
+		unset( $params['w'] );
+	}
+	if ( isset( $params['width'] ) && substr( $params['width'], -2 ) == 'px' ) {
+		// strip the px (pixel) suffix, if found
+		$params['width'] = substr( $params['width'], 0, -2 );
+	}
+	if ( isset( $params['p'] ) ) {
+		$params['page'] = $params['p'];
+	}
+
+	// Is this a thumb of an archived file?
+	$isOld = ( isset( $params['archived'] ) && $params['archived'] );
+	unset( $params['archived'] ); // handlers don't care
+
+	// Is this a thumb of a temp file?
+	$isTemp = ( isset( $params['temp'] ) && $params['temp'] );
+	unset( $params['temp'] ); // handlers don't care
+
+	// Some basic input validation
+	$fileName = strtr( $fileName, '\\/', '__' );
+
+	// Actually fetch the image. Method depends on whether it is archived or not.
+	if ( $isTemp ) {
+		$repo = RepoGroup::singleton()->getLocalRepo()->getTempRepo();
+		$img = new UnregisteredLocalFile( null, $repo,
+			# Temp files are hashed based on the name without the timestamp.
+			# The thumbnails will be hashed based on the entire name however.
+			# @todo fix this convention to actually be reasonable.
+			$repo->getZonePath( 'public' ) . '/' . $repo->getTempHashPath( $fileName ) . $fileName
+		);
+	} elseif ( $isOld ) {
+		// Format is <timestamp>!<name>
+		$bits = explode( '!', $fileName, 2 );
+		if ( count( $bits ) != 2 ) {
+			wfThumbError( 404, wfMessage( 'badtitletext' )->parse() );
+			return;
+		}
+		$title = Title::makeTitleSafe( NS_FILE, $bits[1] );
+		if ( !$title ) {
+			wfThumbError( 404, wfMessage( 'badtitletext' )->parse() );
+			return;
+		}
+		$img = RepoGroup::singleton()->getLocalRepo()->newFromArchiveName( $title, $fileName );
+	} else {
+		$img = wfLocalFile( $fileName );
+	}
+
+	// Check the source file title
+	if ( !$img ) {
+		wfThumbError( 404, wfMessage( 'badtitletext' )->parse() );
+		return;
+	}
+
+	// Check permissions if there are read restrictions
+	$varyHeader = [];
+	if ( !in_array( 'read', User::getGroupPermissions( [ '*' ] ), true ) ) {
+		if ( !$img->getTitle() || !$img->getTitle()->userCan( 'read' ) ) {
+			wfThumbError( 403, 'Access denied. You do not have permission to access ' .
+				'the source file.' );
+			return;
+		}
+		$headers[] = 'Cache-Control: private';
+		$varyHeader[] = 'Cookie';
+	}
+
+	// Check if the file is hidden
+	if ( $img->isDeleted( File::DELETED_FILE ) ) {
+		wfThumbErrorText( 404, "The source file '$fileName' does not exist." );
+		return;
+	}
+
+	// Do rendering parameters extraction from thumbnail name.
+	if ( isset( $params['thumbName'] ) ) {
+		$params = wfExtractThumbParams( $img, $params );
+	}
+	if ( $params == null ) {
+		wfThumbError( 400, 'The specified thumbnail parameters are not recognized.' );
+		return;
+	}
+
+	// Check the source file storage path
+	if ( !$img->exists() ) {
+		$redirectedLocation = false;
+		if ( !$isTemp ) {
+			// Check for file redirect
+			// Since redirects are associated with pages, not versions of files,
+			// we look for the most current version to see if its a redirect.
+			$possRedirFile = RepoGroup::singleton()->getLocalRepo()->findFile( $img->getName() );
+			if ( $possRedirFile && !is_null( $possRedirFile->getRedirected() ) ) {
+				$redirTarget = $possRedirFile->getName();
+				$targetFile = wfLocalFile( Title::makeTitleSafe( NS_FILE, $redirTarget ) );
+				if ( $targetFile->exists() ) {
+					$newThumbName = $targetFile->thumbName( $params );
+					if ( $isOld ) {
+						/** @var array $bits */
+						$newThumbUrl = $targetFile->getArchiveThumbUrl(
+							$bits[0] . '!' . $targetFile->getName(), $newThumbName );
+					} else {
+						$newThumbUrl = $targetFile->getThumbUrl( $newThumbName );
+					}
+					$redirectedLocation = wfExpandUrl( $newThumbUrl, PROTO_CURRENT );
+				}
+			}
+		}
+
+		if ( $redirectedLocation ) {
+			// File has been moved. Give redirect.
+			$response = RequestContext::getMain()->getRequest()->response();
+			$response->statusHeader( 302 );
+			$response->header( 'Location: ' . $redirectedLocation );
+			$response->header( 'Expires: ' .
+				gmdate( 'D, d M Y H:i:s', time() + 12 * 3600 ) . ' GMT' );
+			if ( $wgVaryOnXFP ) {
+				$varyHeader[] = 'X-Forwarded-Proto';
+			}
+			if ( count( $varyHeader ) ) {
+				$response->header( 'Vary: ' . implode( ', ', $varyHeader ) );
+			}
+			$response->header( 'Content-Length: 0' );
+			return;
+		}
+
+		// If its not a redirect that has a target as a local file, give 404.
+		wfThumbErrorText( 404, "The source file '$fileName' does not exist." );
+		return;
+	} elseif ( $img->getPath() === false ) {
+		wfThumbErrorText( 400, "The source file '$fileName' is not locally accessible." );
+		return;
+	}
+
+	// Check IMS against the source file
+	// This means that clients can keep a cached copy even after it has been deleted on the server
+	if ( !empty( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ) {
+		// Fix IE brokenness
+		$imsString = preg_replace( '/;.*$/', '', $_SERVER["HTTP_IF_MODIFIED_SINCE"] );
+		// Calculate time
+		Wikimedia\suppressWarnings();
+		$imsUnix = strtotime( $imsString );
+		Wikimedia\restoreWarnings();
+		if ( wfTimestamp( TS_UNIX, $img->getTimestamp() ) <= $imsUnix ) {
+			HttpStatus::header( 304 );
+			return;
+		}
+	}
+
+	$rel404 = isset( $params['rel404'] ) ? $params['rel404'] : null;
+	unset( $params['r'] ); // ignore 'r' because we unconditionally pass File::RENDER
+	unset( $params['f'] ); // We're done with 'f' parameter.
+	unset( $params['rel404'] ); // moved to $rel404
+
+	// Get the normalized thumbnail name from the parameters...
+	try {
+		$thumbName = $img->thumbName( $params );
+		if ( !strlen( $thumbName ) ) { // invalid params?
+			throw new MediaTransformInvalidParametersException(
+				'Empty return from File::thumbName'
+			);
+		}
+		$thumbName2 = $img->thumbName( $params, File::THUMB_FULL_NAME ); // b/c; "long" style
+	} catch ( MediaTransformInvalidParametersException $e ) {
+		wfThumbError(
+			400,
+			'The specified thumbnail parameters are not valid: ' . $e->getMessage()
+		);
+		return;
+	} catch ( MWException $e ) {
+		wfThumbError( 500, $e->getHTML(), 'Exception caught while extracting thumb name',
+			[ 'exception' => $e ] );
+		return;
+	}
+
+	// For 404 handled thumbnails, we only use the base name of the URI
+	// for the thumb params and the parent directory for the source file name.
+	// Check that the zone relative path matches up so squid caches won't pick
+	// up thumbs that would not be purged on source file deletion (T36231).
+	if ( $rel404 !== null ) { // thumbnail was handled via 404
+		if ( rawurldecode( $rel404 ) === $img->getThumbRel( $thumbName ) ) {
+			// Request for the canonical thumbnail name
+		} elseif ( rawurldecode( $rel404 ) === $img->getThumbRel( $thumbName2 ) ) {
+			// Request for the "long" thumbnail name; redirect to canonical name
+			$response = RequestContext::getMain()->getRequest()->response();
+			$response->statusHeader( 301 );
+			$response->header( 'Location: ' .
+				wfExpandUrl( $img->getThumbUrl( $thumbName ), PROTO_CURRENT ) );
+			$response->header( 'Expires: ' .
+				gmdate( 'D, d M Y H:i:s', time() + 7 * 86400 ) . ' GMT' );
+			if ( $wgVaryOnXFP ) {
+				$varyHeader[] = 'X-Forwarded-Proto';
+			}
+			if ( count( $varyHeader ) ) {
+				$response->header( 'Vary: ' . implode( ', ', $varyHeader ) );
+			}
+			return;
+		} else {
+			wfThumbErrorText( 404, "The given path of the specified thumbnail is incorrect;
+				expected '" . $img->getThumbRel( $thumbName ) . "' but got '" .
+				rawurldecode( $rel404 ) . "'." );
+			return;
+		}
+	}
+
+	$dispositionType = isset( $params['download'] ) ? 'attachment' : 'inline';
+
+	// Suggest a good name for users downloading this thumbnail
+	$headers[] =
+		"Content-Disposition: {$img->getThumbDisposition( $thumbName, $dispositionType )}";
+
+	if ( count( $varyHeader ) ) {
+		$headers[] = 'Vary: ' . implode( ', ', $varyHeader );
+	}
+
+	// Stream the file if it exists already...
+	$thumbPath = $img->getThumbPath( $thumbName );
+	if ( $img->getRepo()->fileExists( $thumbPath ) ) {
+		$starttime = microtime( true );
+		$status = $img->getRepo()->streamFileWithStatus( $thumbPath, $headers );
+		$streamtime = microtime( true ) - $starttime;
+
+		if ( $status->isOK() ) {
+			MediaWikiServices::getInstance()->getStatsdDataFactory()->timing(
+				'media.thumbnail.stream', $streamtime
+			);
+		} else {
+			wfThumbError( 500, 'Could not stream the file', null, [ 'file' => $thumbName,
+				'path' => $thumbPath, 'error' => $status->getWikiText( false, false, 'en' ) ] );
+		}
+		return;
+	}
+
+	$user = RequestContext::getMain()->getUser();
+	if ( !wfThumbIsStandard( $img, $params ) && $user->pingLimiter( 'renderfile-nonstandard' ) ) {
+		wfThumbError( 429, wfMessage( 'actionthrottledtext' )->parse() );
+		return;
+	} elseif ( $user->pingLimiter( 'renderfile' ) ) {
+		wfThumbError( 429, wfMessage( 'actionthrottledtext' )->parse() );
+		return;
+	}
+
+	$thumbProxyUrl = $img->getRepo()->getThumbProxyUrl();
+
+	if ( strlen( $thumbProxyUrl ) ) {
+		wfProxyThumbnailRequest( $img, $thumbName );
+		// No local fallback when in proxy mode
+		return;
+	} else {
+		// Generate the thumbnail locally
+		list( $thumb, $errorMsg ) = wfGenerateThumbnail( $img, $params, $thumbName, $thumbPath );
+	}
+
+	/** @var MediaTransformOutput|MediaTransformError|bool $thumb */
+
+	// Check for thumbnail generation errors...
+	$msg = wfMessage( 'thumbnail_error' );
+	$errorCode = 500;
+
+	if ( !$thumb ) {
+		$errorMsg = $errorMsg ?: $msg->rawParams( 'File::transform() returned false' )->escaped();
+		if ( $errorMsg instanceof MessageSpecifier &&
+			$errorMsg->getKey() === 'thumbnail_image-failure-limit'
+		) {
+			$errorCode = 429;
+		}
+	} elseif ( $thumb->isError() ) {
+		$errorMsg = $thumb->getHtmlMsg();
+		$errorCode = $thumb->getHttpStatusCode();
+	} elseif ( !$thumb->hasFile() ) {
+		$errorMsg = $msg->rawParams( 'No path supplied in thumbnail object' )->escaped();
+	} elseif ( $thumb->fileIsSource() ) {
+		$errorMsg = $msg
+			->rawParams( 'Image was not scaled, is the requested width bigger than the source?' )
+			->escaped();
+		$errorCode = 400;
+	}
+
+	if ( $errorMsg !== false ) {
+		wfThumbError( $errorCode, $errorMsg, null, [ 'file' => $thumbName, 'path' => $thumbPath ] );
+	} else {
+		// Stream the file if there were no errors
+		$status = $thumb->streamFileWithStatus( $headers );
+		if ( !$status->isOK() ) {
+			wfThumbError( 500, 'Could not stream the file', null, [
+				'file' => $thumbName, 'path' => $thumbPath,
+				'error' => $status->getWikiText( false, false, 'en' ) ] );
+		}
+	}
+}
+
+/**
+ * Proxies thumbnail request to a service that handles thumbnailing
+ *
+ * @param File $img
+ * @param string $thumbName
+ */
+function wfProxyThumbnailRequest( $img, $thumbName ) {
+	$thumbProxyUrl = $img->getRepo()->getThumbProxyUrl();
+
+	// Instead of generating the thumbnail ourselves, we proxy the request to another service
+	$thumbProxiedUrl = $thumbProxyUrl . $img->getThumbRel( $thumbName );
+
+	$req = MWHttpRequest::factory( $thumbProxiedUrl );
+	$secret = $img->getRepo()->getThumbProxySecret();
+
+	// Pass a secret key shared with the proxied service if any
+	if ( strlen( $secret ) ) {
+		$req->setHeader( 'X-Swift-Secret', $secret );
+	}
+
+	// Send request to proxied service
+	$status = $req->execute();
+
+	// Simply serve the response from the proxied service as-is
+	header( 'HTTP/1.1 ' . $req->getStatus() );
+
+	$headers = $req->getResponseHeaders();
+
+	foreach ( $headers as $key => $values ) {
+		foreach ( $values as $value ) {
+			header( $key . ': ' . $value, false );
+		}
+	}
+
+	echo $req->getContent();
+}
+
+/**
+ * Actually try to generate a new thumbnail
+ *
+ * @param File $file
+ * @param array $params
+ * @param string $thumbName
+ * @param string $thumbPath
+ * @return array (MediaTransformOutput|bool, string|bool error message HTML)
+ */
+function wfGenerateThumbnail( File $file, array $params, $thumbName, $thumbPath ) {
+	global $wgAttemptFailureEpoch;
+
+	$cache = ObjectCache::getLocalClusterInstance();
+	$key = $cache->makeKey(
+		'attempt-failures',
+		$wgAttemptFailureEpoch,
+		$file->getRepo()->getName(),
+		$file->getSha1(),
+		md5( $thumbName )
+	);
+
+	// Check if this file keeps failing to render
+	if ( $cache->get( $key ) >= 4 ) {
+		return [ false, wfMessage( 'thumbnail_image-failure-limit', 4 ) ];
+	}
+
+	$done = false;
+	// Record failures on PHP fatals in addition to caching exceptions
+	register_shutdown_function( function () use ( $cache, &$done, $key ) {
+		if ( !$done ) { // transform() gave a fatal
+			// Randomize TTL to reduce stampedes
+			$cache->incrWithInit( $key, $cache::TTL_HOUR + mt_rand( 0, 300 ) );
+		}
+	} );
+
+	$thumb = false;
+	$errorHtml = false;
+
+	// guard thumbnail rendering with PoolCounter to avoid stampedes
+	// expensive files use a separate PoolCounter config so it is possible
+	// to set up a global limit on them
+	if ( $file->isExpensiveToThumbnail() ) {
+		$poolCounterType = 'FileRenderExpensive';
+	} else {
+		$poolCounterType = 'FileRender';
+	}
+
+	// Thumbnail isn't already there, so create the new thumbnail...
+	try {
+		$work = new PoolCounterWorkViaCallback( $poolCounterType, sha1( $file->getName() ),
+			[
+				'doWork' => function () use ( $file, $params ) {
+					return $file->transform( $params, File::RENDER_NOW );
+				},
+				'doCachedWork' => function () use ( $file, $params, $thumbPath ) {
+					// If the worker that finished made this thumbnail then use it.
+					// Otherwise, it probably made a different thumbnail for this file.
+					return $file->getRepo()->fileExists( $thumbPath )
+						? $file->transform( $params, File::RENDER_NOW )
+						: false; // retry once more in exclusive mode
+				},
+				'error' => function ( Status $status ) {
+					return wfMessage( 'generic-pool-error' )->parse() . '<hr>' . $status->getHTML();
+				}
+			]
+		);
+		$result = $work->execute();
+		if ( $result instanceof MediaTransformOutput ) {
+			$thumb = $result;
+		} elseif ( is_string( $result ) ) { // error
+			$errorHtml = $result;
+		}
+	} catch ( Exception $e ) {
+		// Tried to select a page on a non-paged file?
+	}
+
+	/** @noinspection PhpUnusedLocalVariableInspection */
+	$done = true; // no PHP fatal occured
+
+	if ( !$thumb || $thumb->isError() ) {
+		// Randomize TTL to reduce stampedes
+		$cache->incrWithInit( $key, $cache::TTL_HOUR + mt_rand( 0, 300 ) );
+	}
+
+	return [ $thumb, $errorHtml ];
+}
+
+/**
+ * Convert pathinfo type parameter, into normal request parameters
+ *
+ * So for example, if the request was redirected from
+ * /w/images/thumb/a/ab/Foo.png/120px-Foo.png. The $thumbRel parameter
+ * of this function would be set to "a/ab/Foo.png/120px-Foo.png".
+ * This method is responsible for turning that into an array
+ * with the folowing keys:
+ *  * f => the filename (Foo.png)
+ *  * rel404 => the whole thing (a/ab/Foo.png/120px-Foo.png)
+ *  * archived => 1 (If the request is for an archived thumb)
+ *  * temp => 1 (If the file is in the "temporary" zone)
+ *  * thumbName => the thumbnail name, including parameters (120px-Foo.png)
+ *
+ * Transform specific parameters are set later via wfExtractThumbParams().
+ *
+ * @param string $thumbRel Thumbnail path relative to the thumb zone
+ * @return array|null Associative params array or null
+ */
+function wfExtractThumbRequestInfo( $thumbRel ) {
+	$repo = RepoGroup::singleton()->getLocalRepo();
+
+	$hashDirReg = $subdirReg = '';
+	$hashLevels = $repo->getHashLevels();
+	for ( $i = 0; $i < $hashLevels; $i++ ) {
+		$subdirReg .= '[0-9a-f]';
+		$hashDirReg .= "$subdirReg/";
+	}
+
+	// Check if this is a thumbnail of an original in the local file repo
+	if ( preg_match( "!^((archive/)?$hashDirReg([^/]*)/([^/]*))$!", $thumbRel, $m ) ) {
+		list( /*all*/, $rel, $archOrTemp, $filename, $thumbname ) = $m;
+	// Check if this is a thumbnail of an temp file in the local file repo
+	} elseif ( preg_match( "!^(temp/)($hashDirReg([^/]*)/([^/]*))$!", $thumbRel, $m ) ) {
+		list( /*all*/, $archOrTemp, $rel, $filename, $thumbname ) = $m;
+	} else {
+		return null; // not a valid looking thumbnail request
+	}
+
+	$params = [ 'f' => $filename, 'rel404' => $rel ];
+	if ( $archOrTemp === 'archive/' ) {
+		$params['archived'] = 1;
+	} elseif ( $archOrTemp === 'temp/' ) {
+		$params['temp'] = 1;
+	}
+
+	$params['thumbName'] = $thumbname;
+	return $params;
+}
+
+/**
+ * Convert a thumbnail name (122px-foo.png) to parameters, using
+ * file handler.
+ *
+ * @param File $file File object for file in question
+ * @param array $params Array of parameters so far
+ * @return array Parameters array with more parameters
+ */
+function wfExtractThumbParams( $file, $params ) {
+	if ( !isset( $params['thumbName'] ) ) {
+		throw new InvalidArgumentException( "No thumbnail name passed to wfExtractThumbParams" );
+	}
+
+	$thumbname = $params['thumbName'];
+	unset( $params['thumbName'] );
+
+	// FIXME: Files in the temp zone don't set a MIME type, which means
+	// they don't have a handler. Which means we can't parse the param
+	// string. However, not a big issue as what good is a param string
+	// if you have no handler to make use of the param string and
+	// actually generate the thumbnail.
+	$handler = $file->getHandler();
+
+	// Based on UploadStash::parseKey
+	$fileNamePos = strrpos( $thumbname, $params['f'] );
+	if ( $fileNamePos === false ) {
+		// Maybe using a short filename? (see FileRepo::nameForThumb)
+		$fileNamePos = strrpos( $thumbname, 'thumbnail' );
+	}
+
+	if ( $handler && $fileNamePos !== false ) {
+		$paramString = substr( $thumbname, 0, $fileNamePos - 1 );
+		$extraParams = $handler->parseParamString( $paramString );
+		if ( $extraParams !== false ) {
+			return $params + $extraParams;
+		}
+	}
+
+	// As a last ditch fallback, use the traditional common parameters
+	if ( preg_match( '!^(page(\d*)-)*(\d*)px-[^/]*$!', $thumbname, $matches ) ) {
+		list( /* all */, /* pagefull */, $pagenum, $size ) = $matches;
+		$params['width'] = $size;
+		if ( $pagenum ) {
+			$params['page'] = $pagenum;
+		}
+		return $params; // valid thumbnail URL
+	}
+	return null;
+}
+
+/**
+ * Output a thumbnail generation error message
+ *
+ * @param int $status
+ * @param string $msgText Plain text (will be html escaped)
+ * @return void
+ */
+function wfThumbErrorText( $status, $msgText ) {
+	wfThumbError( $status, htmlspecialchars( $msgText, ENT_NOQUOTES ) );
+}
+
+/**
+ * Output a thumbnail generation error message
+ *
+ * @param int $status
+ * @param string $msgHtml HTML
+ * @param string $msgText Short error description, for internal logging. Defaults to $msgHtml.
+ *   Only used for HTTP 500 errors.
+ * @param array $context Error context, for internal logging. Only used for HTTP 500 errors.
+ * @return void
+ */
+function wfThumbError( $status, $msgHtml, $msgText = null, $context = [] ) {
+	global $wgShowHostnames;
+
+	header( 'Cache-Control: no-cache' );
+	header( 'Content-Type: text/html; charset=utf-8' );
+	if ( $status == 400 || $status == 404 || $status == 429 ) {
+		HttpStatus::header( $status );
+	} elseif ( $status == 403 ) {
+		HttpStatus::header( 403 );
+		header( 'Vary: Cookie' );
+	} else {
+		LoggerFactory::getInstance( 'thumb' )->error( $msgText ?: $msgHtml, $context );
+		HttpStatus::header( 500 );
+	}
+	if ( $wgShowHostnames ) {
+		header( 'X-MW-Thumbnail-Renderer: ' . wfHostname() );
+		$url = htmlspecialchars(
+			isset( $_SERVER['REQUEST_URI'] ) ? $_SERVER['REQUEST_URI'] : '',
+			ENT_NOQUOTES
+		);
+		$hostname = htmlspecialchars( wfHostname(), ENT_NOQUOTES );
+		$debug = "<!-- $url -->\n<!-- $hostname -->\n";
+	} else {
+		$debug = '';
+	}
+	$content = <<<EOT
+<!DOCTYPE html>
+<html><head>
+<meta charset="UTF-8" />
+<title>Error generating thumbnail</title>
+</head>
+<body>
+<h1>Error generating thumbnail</h1>
+<p>
+$msgHtml
+</p>
+$debug
+</body>
+</html>
+
+EOT;
+	header( 'Content-Length: ' . strlen( $content ) );
+	echo $content;
+}