ThumbnailEntryPoint.php

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<?php
namespace MediaWiki\FileRepo;
 
use Exception;
use File;
use InvalidArgumentException;
use MediaTransformInvalidParametersException;
use MediaTransformOutput;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiEntryPoint;
use MediaWiki\MediaWikiServices;
use MediaWiki\Permissions\PermissionStatus;
use MediaWiki\PoolCounter\PoolCounterWorkViaCallback;
use MediaWiki\Profiler\ProfilingContext;
use MediaWiki\Request\HeaderCallback;
use MediaWiki\Status\Status;
use MediaWiki\Title\Title;
use MessageSpecifier;
use MWException;
use ObjectCache;
use UnregisteredLocalFile;
use Wikimedia\AtEase\AtEase;
 
class ThumbnailEntryPoint extends MediaWikiEntryPoint {
 
    public function execute() {
        global $wgTrivialMimeDetection;
 
        ProfilingContext::singleton()->init(
            MW_ENTRY_POINT,
            'stream'
        );
 
        // Don't use fancy MIME detection, just check the file extension for jpg/gif/png.
        // NOTE: This only works as long as to StreamFile::contentTypeFromPath
        //       get this setting from global state. When StreamFile gets refactored,
        //       we need to find a better way.
        $wgTrivialMimeDetection = true;
 
        $this->handleRequest();
    }
 
    protected function doPrepareForOutput() {
        // No-op.
        // Do not call parent::doPrepareForOutput() to avoid
        // commitMainTransaction() getting called.
    }
 
    protected function handleRequest() {
        $this->streamThumb( $this->getRequest()->getQueryValuesOnly() );
    }
 
    protected function streamThumb( array $params ) {
        $varyOnXFP = $this->getConfig( MainConfigNames::VaryOnXFP );
 
        $headers = []; // HTTP headers to send
 
        $fileName = $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
 
        $services = MediaWikiServices::getInstance();
 
        // Some basic input validation
        $fileName = strtr( $fileName, '\\/', '__' );
        $localRepo = $services->getRepoGroup()->getLocalRepo();
        $archiveTimestamp = null;
 
        // Actually fetch the image. Method depends on whether it is archived or not.
        if ( $isTemp ) {
            $repo = $localRepo->getTempRepo();
            $img = new UnregisteredLocalFile( false, $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 ) {
                $this->thumbError( 404, $this->getContext()->msg( 'badtitletext' )->parse() );
                return;
            }
            $archiveTimestamp = $bits[0];
            $title = Title::makeTitleSafe( NS_FILE, $bits[1] );
            if ( !$title ) {
                $this->thumbError( 404, $this->getContext()->msg( 'badtitletext' )->parse() );
                return;
            }
            $img = $localRepo->newFromArchiveName( $title, $fileName );
        } else {
            $img = $localRepo->newFile( $fileName );
        }
 
        // Check the source file title
        if ( !$img ) {
            $this->thumbError( 404, $this->getContext()->msg( 'badtitletext' )->parse() );
            return;
        }
 
        // Check permissions if there are read restrictions
        $varyHeader = [];
        if ( !$services->getGroupPermissionsLookup()->groupHasPermission( '*', 'read' ) ) {
            $authority = $this->getContext()->getAuthority();
            $imgTitle = $img->getTitle();
 
            if ( !$imgTitle || !$authority->authorizeRead( 'read', $imgTitle ) ) {
                $this->thumbErrorText( 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 ) ) {
            $this->thumbErrorText( 404, "The source file '$fileName' does not exist." );
            return;
        }
 
        // Do rendering parameters extraction from thumbnail name.
        if ( isset( $params['thumbName'] ) ) {
            $params = $this->extractThumbParams( $img, $params );
        }
        if ( $params == null ) {
            $this->thumbErrorText( 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 = $localRepo->findFile( $img->getName() );
                if ( $possRedirFile && $possRedirFile->getRedirected() !== null ) {
                    $redirTarget = $possRedirFile->getName();
                    $targetFile = $localRepo->newFile( Title::makeTitleSafe( NS_FILE, $redirTarget ) );
                    if ( $targetFile->exists() ) {
                        $newThumbName = $targetFile->thumbName( $params );
                        if ( $isOld ) {
                            $newThumbUrl = $targetFile->getArchiveThumbUrl(
                                $archiveTimestamp . '!' . $targetFile->getName(), $newThumbName );
                        } else {
                            $newThumbUrl = $targetFile->getThumbUrl( $newThumbName );
                        }
                        $redirectedLocation = wfExpandUrl( $newThumbUrl, PROTO_CURRENT );
                    }
                }
            }
 
            if ( $redirectedLocation ) {
                // File has been moved. Give redirect.
                $response = $this->getResponse();
                $response->statusHeader( 302 );
                $response->header( 'Location: ' . $redirectedLocation );
                $response->header( 'Expires: ' .
                    gmdate( 'D, d M Y H:i:s', time() + 12 * 3600 ) . ' GMT' );
                if ( $varyOnXFP ) {
                    $varyHeader[] = 'X-Forwarded-Proto';
                }
                if ( count( $varyHeader ) ) {
                    $response->header( 'Vary: ' . implode( ', ', $varyHeader ) );
                }
                $response->header( 'Content-Length: 0' );
                return;
            }
 
            // If it's not a redirect that has a target as a local file, give 404.
            $this->thumbErrorText( 404, "The source file '$fileName' does not exist." );
            return;
        } elseif ( $img->getPath() === false ) {
            $this->thumbErrorText( 400, "The source file '$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 ( $this->getServerInfo( 'HTTP_IF_MODIFIED_SINCE', '' ) !== '' ) {
            // Fix IE brokenness
            $imsString = preg_replace(
                '/;.*$/',
                '',
                $this->getServerInfo( 'HTTP_IF_MODIFIED_SINCE' ) ?? ''
            );
            // Calculate time
            AtEase::suppressWarnings();
            $imsUnix = strtotime( $imsString );
            AtEase::restoreWarnings();
            if ( wfTimestamp( TS_UNIX, $img->getTimestamp() ) <= $imsUnix ) {
                $this->status( 304 );
                return;
            }
        }
 
        $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 ) {
            $this->thumbErrorText(
                400,
                'The specified thumbnail parameters are not valid: ' . $e->getMessage()
            );
            return;
        } catch ( MWException $e ) {
            $this->thumbError( 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 CDN 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
                $this->status( 301 );
                $this->header( 'Location: ' .
                    wfExpandUrl( $img->getThumbUrl( $thumbName ), PROTO_CURRENT ) );
                $this->header( 'Expires: ' .
                    gmdate( 'D, d M Y H:i:s', time() + 7 * 86400 ) . ' GMT' );
                if ( $varyOnXFP ) {
                    $varyHeader[] = 'X-Forwarded-Proto';
                }
                if ( count( $varyHeader ) ) {
                    $this->header( 'Vary: ' . implode( ', ', $varyHeader ) );
                }
                return;
            } else {
                $this->thumbErrorText( 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() ) {
                $services->getStatsdDataFactory()->timing(
                    'media.thumbnail.stream',
                    $streamtime
                );
            } else {
                $this->thumbError(
                    500,
                    'Could not stream the file',
                    $status->getWikiText( false, false, 'en' ),
                    [
                        'file' => $thumbName,
                        'path' => $thumbPath,
                        'error' => $status->getWikiText( false, false, 'en' ),
                    ]
                );
            }
            return;
        }
 
        $authority = $this->getContext()->getAuthority();
        $status = PermissionStatus::newEmpty();
        if ( !wfThumbIsStandard( $img, $params )
            && !$authority->authorizeAction( 'renderfile-nonstandard', $status )
        ) {
            $statusFormatter = $services->getFormatterFactory()
                ->getStatusFormatter( $this->getContext() );
 
            $this->thumbError( 429, $statusFormatter->getHTML( $status ) );
            return;
        } elseif ( !$authority->authorizeAction( 'renderfile', $status ) ) {
            $statusFormatter = $services->getFormatterFactory()
                ->getStatusFormatter( $this->getContext() );
 
            $this->thumbError( 429, $statusFormatter->getHTML( $status ) );
            return;
        }
 
        $thumbProxyUrl = $img->getRepo()->getThumbProxyUrl();
 
        if ( strlen( $thumbProxyUrl ?? '' ) ) {
            $this->proxyThumbnailRequest( $img, $thumbName );
            // No local fallback when in proxy mode
            return;
        } else {
            // Generate the thumbnail locally
            [ $thumb, $errorMsg ] = $this->generateThumbnail( $img, $params, $thumbName, $thumbPath );
        }
 
        // Check for thumbnail generation errors...
        $msg = $this->getContext()->msg( '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;
        }
 
        $this->prepareForOutput();
 
        if ( $errorMsg !== false ) {
            $this->thumbError( $errorCode, $errorMsg, null, [ 'file' => $thumbName, 'path' => $thumbPath ] );
        } else {
            // Stream the file if there were no errors
            '@phan-var MediaTransformOutput $thumb';
            $status = $thumb->streamFileWithStatus( $headers );
            if ( !$status->isOK() ) {
                $this->thumbError( 500, 'Could not stream the file', $status->getWikiText( false, false, 'en' ), [
                    'file' => $thumbName, 'path' => $thumbPath,
                    'error' => $status->getWikiText( false, false, 'en' ) ] );
            }
        }
    }
 
    private function proxyThumbnailRequest( $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 = MediaWikiServices::getInstance()->getHttpRequestFactory()->create( $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
        $req->execute();
 
        HeaderCallback::warnIfHeadersSent();
 
        // Simply serve the response from the proxied service as-is
        $this->header( 'HTTP/1.1 ' . $req->getStatus() );
 
        $headers = $req->getResponseHeaders();
 
        foreach ( $headers as $key => $values ) {
            foreach ( $values as $value ) {
                $this->header( $key . ': ' . $value, false );
            }
        }
 
        $this->print( $req->getContent() );
    }
 
    protected function generateThumbnail( File $file, array $params, $thumbName, $thumbPath ) {
        $attemptFailureEpoch = $this->getConfig( MainConfigNames::AttemptFailureEpoch );
 
        $cache = ObjectCache::getLocalClusterInstance();
        $key = $cache->makeKey(
            'attempt-failures',
            $attemptFailureEpoch,
            $file->getRepo()->getName(),
            $file->getSha1(),
            md5( $thumbName )
        );
 
        // Check if this file keeps failing to render
        if ( $cache->get( $key ) >= 4 ) {
            return [ false, $this->getContext()->msg( 'thumbnail_image-failure-limit', 4 ) ];
        }
 
        $done = false;
        // Record failures on PHP fatals in addition to caching exceptions
        register_shutdown_function( static 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' => static function () use ( $file, $params ) {
                        return $file->transform( $params, File::RENDER_NOW );
                    },
                    'doCachedWork' => static 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 $this->getContext()->msg( '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?
        }
 
        $done = true; // no PHP fatal occurred
 
        if ( !$thumb || $thumb->isError() ) {
            // Randomize TTL to reduce stampedes
            $cache->incrWithInit( $key, $cache::TTL_HOUR + mt_rand( 0, 300 ) );
        }
 
        return [ $thumb, $errorHtml ];
    }
 
    private function extractThumbParams( $file, $params ) {
        if ( !isset( $params['thumbName'] ) ) {
            throw new InvalidArgumentException( "No thumbnail name passed to extractThumbParams" );
        }
 
        $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 ) ) {
            [ /* all */, /* pagefull */, $pagenum, $size ] = $matches;
            $params['width'] = $size;
            if ( $pagenum ) {
                $params['page'] = $pagenum;
            }
            return $params; // valid thumbnail URL
        }
        return null;
    }
 
    protected function thumbErrorText( $status, $msgText ) {
        $this->thumbError( $status, htmlspecialchars( $msgText, ENT_NOQUOTES ) );
    }
 
    protected function thumbError( $status, $msgHtml, $msgText = null, $context = [] ) {
        $showHostnames = $this->getConfig( MainConfigNames::ShowHostnames );
 
        HeaderCallback::warnIfHeadersSent();
 
        if ( $this->getResponse()->headersSent() ) {
            LoggerFactory::getInstance( 'thumbnail' )->error(
                'Error after output had been started. Output may be corrupt or truncated. ' .
                'Original error: ' . ( $msgText ?: $msgHtml ) . " (Status $status)",
                $context
            );
            return;
        }
 
        $this->header( 'Cache-Control: no-cache' );
        $this->header( 'Content-Type: text/html; charset=utf-8' );
        if ( $status == 400 || $status == 404 || $status == 429 ) {
            $this->status( $status );
        } elseif ( $status == 403 ) {
            $this->status( 403 );
            $this->header( 'Vary: Cookie' );
        } else {
            LoggerFactory::getInstance( 'thumbnail' )->error( $msgText ?: $msgHtml, $context );
            $this->status( 500 );
        }
        if ( $showHostnames ) {
            $this->header( 'X-MW-Thumbnail-Renderer: ' . wfHostname() );
            $url = htmlspecialchars(
                $this->getServerInfo( '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;
        $this->header( 'Content-Length: ' . strlen( $content ) );
        $this->print( $content );
    }
 
}