includes/StreamFile.php

   1 <?php
   2 /**
   3  * Functions related to the output of file content.
   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  */
  22
  23 /**
  24  * Functions related to the output of file content
  25  */
  26 class StreamFile {
  27         const READY_STREAM = 1;
  28         const NOT_MODIFIED = 2;
  29
  30         /**
  31          * Stream a file to the browser, adding all the headings and fun stuff.
  32          * Headers sent include: Content-type, Content-Length, Last-Modified,
  33          * and Content-Disposition.
  34          *
  35          * @param string $fname Full name and path of the file to stream
  36          * @param array $headers Any additional headers to send
  37          * @param bool $sendErrors Send error messages if errors occur (like 404)
  38          * @throws MWException
  39          * @return bool Success
  40          */
  41         public static function stream( $fname, $headers = array(), $sendErrors = true ) {
  42
  43                 if ( FileBackend::isStoragePath( $fname ) ) { // sanity
  44                         throw new MWException( __FUNCTION__ . " given storage path '$fname'." );
  45                 }
  46
  47                 MediaWiki\suppressWarnings();
  48                 $stat = stat( $fname );
  49                 MediaWiki\restoreWarnings();
  50
  51                 $res = self::prepareForStream( $fname, $stat, $headers, $sendErrors );
  52                 if ( $res == self::NOT_MODIFIED ) {
  53                         $ok = true; // use client cache
  54                 } elseif ( $res == self::READY_STREAM ) {
  55                         $ok = readfile( $fname );
  56                 } else {
  57                         $ok = false; // failed
  58                 }
  59
  60                 return $ok;
  61         }
  62
  63         /**
  64          * Call this function used in preparation before streaming a file.
  65          * This function does the following:
  66          * (a) sends Last-Modified, Content-type, and Content-Disposition headers
  67          * (b) cancels any PHP output buffering and automatic gzipping of output
  68          * (c) sends Content-Length header based on HTTP_IF_MODIFIED_SINCE check
  69          *
  70          * @param string $path Storage path or file system path
  71          * @param array|bool $info File stat info with 'mtime' and 'size' fields
  72          * @param array $headers Additional headers to send
  73          * @param bool $sendErrors Send error messages if errors occur (like 404)
  74          * @return int|bool READY_STREAM, NOT_MODIFIED, or false on failure
  75          */
  76         public static function prepareForStream(
  77                 $path, $info, $headers = array(), $sendErrors = true
  78         ) {
  79                 if ( !is_array( $info ) ) {
  80                         if ( $sendErrors ) {
  81                                 HttpStatus::header( 404 );
  82                                 header( 'Cache-Control: no-cache' );
  83                                 header( 'Content-Type: text/html; charset=utf-8' );
  84                                 $encFile = htmlspecialchars( $path );
  85                                 $encScript = htmlspecialchars( $_SERVER['SCRIPT_NAME'] );
  86                                 echo "<html><body>
  87                                         <h1>File not found</h1>
  88                                         <p>Although this PHP script ($encScript) exists, the file requested for output
  89                                         ($encFile) does not.</p>
  90                                         </body></html>
  91                                         ";
  92                         }
  93                         return false;
  94                 }
  95
  96                 // Sent Last-Modified HTTP header for client-side caching
  97                 header( 'Last-Modified: ' . wfTimestamp( TS_RFC2822, $info['mtime'] ) );
  98
  99                 // Cancel output buffering and gzipping if set
 100                 wfResetOutputBuffers();
 101
 102                 $type = self::contentTypeFromPath( $path );
 103                 if ( $type && $type != 'unknown/unknown' ) {
 104                         header( "Content-type: $type" );
 105                 } else {
 106                         // Send a content type which is not known to Internet Explorer, to
 107                         // avoid triggering IE's content type detection. Sending a standard
 108                         // unknown content type here essentially gives IE license to apply
 109                         // whatever content type it likes.
 110                         header( 'Content-type: application/x-wiki' );
 111                 }
 112
 113                 // Don't stream it out as text/html if there was a PHP error
 114                 if ( headers_sent() ) {
 115                         echo "Headers already sent, terminating.\n";
 116                         return false;
 117                 }
 118
 119                 // Send additional headers
 120                 foreach ( $headers as $header ) {
 121                         header( $header );
 122                 }
 123
 124                 // Don't send if client has up to date cache
 125                 if ( !empty( $_SERVER['HTTP_IF_MODIFIED_SINCE'] ) ) {
 126                         $modsince = preg_replace( '/;.*$/', '', $_SERVER['HTTP_IF_MODIFIED_SINCE'] );
 127                         if ( wfTimestamp( TS_UNIX, $info['mtime'] ) <= strtotime( $modsince ) ) {
 128                                 ini_set( 'zlib.output_compression', 0 );
 129                                 HttpStatus::header( 304 );
 130                                 return self::NOT_MODIFIED; // ok
 131                         }
 132                 }
 133
 134                 header( 'Content-Length: ' . $info['size'] );
 135
 136                 return self::READY_STREAM; // ok
 137         }
 138
 139         /**
 140          * Determine the file type of a file based on the path
 141          *
 142          * @param string $filename Storage path or file system path
 143          * @param bool $safe Whether to do retroactive upload blacklist checks
 144          * @return null|string
 145          */
 146         public static function contentTypeFromPath( $filename, $safe = true ) {
 147                 global $wgTrivialMimeDetection;
 148
 149                 $ext = strrchr( $filename, '.' );
 150                 $ext = $ext === false ? '' : strtolower( substr( $ext, 1 ) );
 151
 152                 # trivial detection by file extension,
 153                 # used for thumbnails (thumb.php)
 154                 if ( $wgTrivialMimeDetection ) {
 155                         switch ( $ext ) {
 156                                 case 'gif':
 157                                         return 'image/gif';
 158                                 case 'png':
 159                                         return 'image/png';
 160                                 case 'jpg':
 161                                         return 'image/jpeg';
 162                                 case 'jpeg':
 163                                         return 'image/jpeg';
 164                         }
 165
 166                         return 'unknown/unknown';
 167                 }
 168
 169                 $magic = MimeMagic::singleton();
 170                 // Use the extension only, rather than magic numbers, to avoid opening
 171                 // up vulnerabilities due to uploads of files with allowed extensions
 172                 // but disallowed types.
 173                 $type = $magic->guessTypesForExtension( $ext );
 174
 175                 /**
 176                  * Double-check some security settings that were done on upload but might
 177                  * have changed since.
 178                  */
 179                 if ( $safe ) {
 180                         global $wgFileBlacklist, $wgCheckFileExtensions, $wgStrictFileExtensions,
 181                                 $wgFileExtensions, $wgVerifyMimeType, $wgMimeTypeBlacklist;
 182                         list( , $extList ) = UploadBase::splitExtensions( $filename );
 183                         if ( UploadBase::checkFileExtensionList( $extList, $wgFileBlacklist ) ) {
 184                                 return 'unknown/unknown';
 185                         }
 186                         if ( $wgCheckFileExtensions && $wgStrictFileExtensions
 187                                 && !UploadBase::checkFileExtensionList( $extList, $wgFileExtensions )
 188                         ) {
 189                                 return 'unknown/unknown';
 190                         }
 191                         if ( $wgVerifyMimeType && in_array( strtolower( $type ), $wgMimeTypeBlacklist ) ) {
 192                                 return 'unknown/unknown';
 193                         }
 194                 }
 195                 return $type;
 196         }
 197 }