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[mediawiki.git] / includes / libs / filebackend / HTTPFileStreamer.php

<?php
/**
 * Functions related to the output of file content.
 *
 * 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
 */

namespace Wikimedia\FileBackend;

use HttpStatus;
use Wikimedia\AtEase\AtEase;
use Wikimedia\Timestamp\ConvertibleTimestamp;

/**
 * Functions related to the output of file content
 *
 * @since 1.28
 */
class HTTPFileStreamer {
        /** @var string */
        protected $path;
        /** @var callable */
        protected $obResetFunc;
        /** @var callable */
        protected $streamMimeFunc;
        /** @var callable */
        protected $headerFunc;

        // Do not send any HTTP headers (i.e. body only)
        public const STREAM_HEADLESS = 1;
        // Do not try to tear down any PHP output buffers
        public const STREAM_ALLOW_OB = 2;

        /**
         * Takes HTTP headers in a name => value format and converts them to the weird format
         * expected by stream().
         * @param string[] $headers
         * @return array[] [ $headers, $optHeaders ]
         * @since 1.34
         */
        public static function preprocessHeaders( $headers ) {
                $rawHeaders = [];
                $optHeaders = [];
                foreach ( $headers as $name => $header ) {
                        $nameLower = strtolower( $name );
                        if ( in_array( $nameLower, [ 'range', 'if-modified-since' ], true ) ) {
                                $optHeaders[$nameLower] = $header;
                        } else {
                                $rawHeaders[] = "$name: $header";
                        }
                }
                return [ $rawHeaders, $optHeaders ];
        }

        /**
         * @param string $path Local filesystem path to a file
         * @param array $params Options map, which includes:
         *   - obResetFunc : alternative callback to clear the output buffer
         *   - streamMimeFunc : alternative method to determine the content type from the path
         *   - headerFunc : alternative method for sending response headers
         */
        public function __construct( $path, array $params = [] ) {
                $this->path = $path;

                $this->obResetFunc = $params['obResetFunc'] ??
                        [ __CLASS__, 'resetOutputBuffers' ];

                $this->streamMimeFunc = $params['streamMimeFunc'] ??
                        [ __CLASS__, 'contentTypeFromPath' ];

                $this->headerFunc = $params['headerFunc'] ?? 'header';
        }

        /**
         * Stream a file to the browser, adding all the headings and fun stuff.
         * Headers sent include: Content-type, Content-Length, Last-Modified,
         * and Content-Disposition.
         *
         * @param array $headers Any additional headers to send if the file exists
         * @param bool $sendErrors Send error messages if errors occur (like 404)
         * @param array $optHeaders HTTP request header map (e.g. "range") (use lowercase keys)
         * @param int $flags Bitfield of STREAM_* constants
         * @return bool Success
         */
        public function stream(
                $headers = [], $sendErrors = true, $optHeaders = [], $flags = 0
        ) {
                $headless = ( $flags & self::STREAM_HEADLESS );

                // Don't stream it out as text/html if there was a PHP error
                if ( $headers && headers_sent() ) {
                        echo "Headers already sent, terminating.\n";
                        return false;
                }

                $headerFunc = $headless
                        ? static function ( $header ) {
                                // no-op
                        }
                        : [ $this, 'header' ];

                AtEase::suppressWarnings();
                $info = stat( $this->path );
                AtEase::restoreWarnings();

                if ( !is_array( $info ) ) {
                        if ( $sendErrors ) {
                                self::send404Message( $this->path, $flags );
                        }
                        return false;
                }

                // Send Last-Modified HTTP header for client-side caching
                $mtimeCT = new ConvertibleTimestamp( $info['mtime'] );
                $headerFunc( 'Last-Modified: ' . $mtimeCT->getTimestamp( TS_RFC2822 ) );

                if ( ( $flags & self::STREAM_ALLOW_OB ) == 0 ) {
                        call_user_func( $this->obResetFunc );
                }

                $type = call_user_func( $this->streamMimeFunc, $this->path );
                if ( $type && $type != 'unknown/unknown' ) {
                        $headerFunc( "Content-type: $type" );
                } else {
                        // Send a content type which is not known to Internet Explorer, to
                        // avoid triggering IE's content type detection. Sending a standard
                        // unknown content type here essentially gives IE license to apply
                        // whatever content type it likes.
                        $headerFunc( 'Content-type: application/x-wiki' );
                }

                // Don't send if client has up to date cache
                if ( isset( $optHeaders['if-modified-since'] ) ) {
                        $modsince = preg_replace( '/;.*$/', '', $optHeaders['if-modified-since'] );
                        if ( $mtimeCT->getTimestamp( TS_UNIX ) <= strtotime( $modsince ) ) {
                                ini_set( 'zlib.output_compression', 0 );
                                $headerFunc( 304 );
                                return true; // ok
                        }
                }

                // Send additional headers
                foreach ( $headers as $header ) {
                        $headerFunc( $header );
                }

                if ( isset( $optHeaders['range'] ) ) {
                        $range = self::parseRange( $optHeaders['range'], $info['size'] );
                        if ( is_array( $range ) ) {
                                $headerFunc( 206 );
                                $headerFunc( 'Content-Length: ' . $range[2] );
                                $headerFunc( "Content-Range: bytes {$range[0]}-{$range[1]}/{$info['size']}" );
                        } elseif ( $range === 'invalid' ) {
                                if ( $sendErrors ) {
                                        $headerFunc( 416 );
                                        $headerFunc( 'Cache-Control: no-cache' );
                                        $headerFunc( 'Content-Type: text/html; charset=utf-8' );
                                        $headerFunc( 'Content-Range: bytes */' . $info['size'] );
                                }
                                return false;
                        } else { // unsupported Range request (e.g. multiple ranges)
                                $range = null;
                                $headerFunc( 'Content-Length: ' . $info['size'] );
                        }
                } else {
                        $range = null;
                        $headerFunc( 'Content-Length: ' . $info['size'] );
                }

                if ( is_array( $range ) ) {
                        $handle = fopen( $this->path, 'rb' );
                        if ( $handle ) {
                                $ok = true;
                                fseek( $handle, $range[0] );
                                $remaining = $range[2];
                                while ( $remaining > 0 && $ok ) {
                                        $bytes = min( $remaining, 8 * 1024 );
                                        $data = fread( $handle, $bytes );
                                        $remaining -= $bytes;
                                        $ok = ( $data !== false );
                                        print $data;
                                }
                        } else {
                                return false;
                        }
                } else {
                        return readfile( $this->path ) !== false; // faster
                }

                return true;
        }

        /**
         * Send out a standard 404 message for a file
         *
         * @param string $fname Full name and path of the file to stream
         * @param int $flags Bitfield of STREAM_* constants
         * @since 1.24
         */
        public static function send404Message( $fname, $flags = 0 ) {
                if ( ( $flags & self::STREAM_HEADLESS ) == 0 ) {
                        HttpStatus::header( 404 );
                        header( 'Cache-Control: no-cache' );
                        header( 'Content-Type: text/html; charset=utf-8' );
                }
                $encFile = htmlspecialchars( $fname );
                $encScript = htmlspecialchars( $_SERVER['SCRIPT_NAME'] );
                echo "<!DOCTYPE html><html><body>
                        <h1>File not found</h1>
                        <p>Although this PHP script ($encScript) exists, the file requested for output
                        ($encFile) does not.</p>
                        </body></html>
                        ";
        }

        /**
         * Convert a Range header value to an absolute (start, end) range tuple
         *
         * @param string $range Range header value
         * @param int $size File size
         * @return array|string Returns error string on failure (start, end, length)
         * @since 1.24
         */
        public static function parseRange( $range, $size ) {
                $m = [];
                if ( preg_match( '#^bytes=(\d*)-(\d*)$#', $range, $m ) ) {
                        [ , $start, $end ] = $m;
                        if ( $start === '' && $end === '' ) {
                                $absRange = [ 0, $size - 1 ];
                        } elseif ( $start === '' ) {
                                $absRange = [ $size - (int)$end, $size - 1 ];
                        } elseif ( $end === '' ) {
                                $absRange = [ (int)$start, $size - 1 ];
                        } else {
                                $absRange = [ (int)$start, (int)$end ];
                        }
                        if ( $absRange[0] >= 0 && $absRange[1] >= $absRange[0] ) {
                                if ( $absRange[0] < $size ) {
                                        $absRange[1] = min( $absRange[1], $size - 1 ); // stop at EOF
                                        $absRange[2] = $absRange[1] - $absRange[0] + 1;
                                        return $absRange;
                                } elseif ( $absRange[0] == 0 && $size == 0 ) {
                                        return 'unrecognized'; // the whole file should just be sent
                                }
                        }
                        return 'invalid';
                }
                return 'unrecognized';
        }

        protected static function resetOutputBuffers() {
                while ( ob_get_status() ) {
                        if ( !ob_end_clean() ) {
                                // Could not remove output buffer handler; abort now
                                // to avoid getting in some kind of infinite loop.
                                break;
                        }
                }
        }

        /**
         * Determine the file type of a file based on the path
         *
         * @param string $filename Storage path or file system path
         * @return null|string
         */
        protected static function contentTypeFromPath( $filename ) {
                $ext = strrchr( $filename, '.' );
                $ext = $ext ? strtolower( substr( $ext, 1 ) ) : '';

                switch ( $ext ) {
                        case 'gif':
                                return 'image/gif';
                        case 'png':
                                return 'image/png';
                        case 'jpg':
                        case 'jpeg':
                                return 'image/jpeg';
                        // T366422: Support webp here as well for consistency
                        case 'webp':
                                return 'image/webp';
                }

                return 'unknown/unknown';
        }

        private function header( $header ) {
                if ( is_int( $header ) ) {
                        $header = HttpStatus::getHeader( $header );
                }

                ( $this->headerFunc )( $header );
        }
}

/** @deprecated class alias since 1.43 */
class_alias( HTTPFileStreamer::class, 'HTTPFileStreamer' );