includes/OutputHandler.php

   1 <?php
   2 /**
   3  * Functions to be used with PHP's output buffer.
   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 namespace MediaWiki;
  24
  25 /**
  26  * @since 1.31
  27  */
  28 class OutputHandler {
  29         /**
  30          * Standard output handler for use with ob_start.
  31          *
  32          * @param string $s Web response output
  33          * @return string
  34          */
  35         public static function handle( $s ) {
  36                 global $wgDisableOutputCompression, $wgMangleFlashPolicy;
  37                 if ( $wgMangleFlashPolicy ) {
  38                         $s = self::mangleFlashPolicy( $s );
  39                 }
  40                 if ( !$wgDisableOutputCompression && !ini_get( 'zlib.output_compression' ) ) {
  41                         if ( !defined( 'MW_NO_OUTPUT_COMPRESSION' ) ) {
  42                                 $s = self::handleGzip( $s );
  43                         }
  44                         if ( !ini_get( 'output_handler' ) ) {
  45                                 self::emitContentLength( strlen( $s ) );
  46                         }
  47                 }
  48                 return $s;
  49         }
  50
  51         /**
  52          * Get the "file extension" that some client apps will estimate from
  53          * the currently-requested URL.
  54          *
  55          * This isn't a WebRequest method, because we need it before the class loads.
  56          * @todo As of 2018, this actually runs after autoloader in Setup.php, so
  57          * WebRequest seems like a good place for this.
  58          *
  59          * @return string
  60          */
  61         private static function findUriExtension() {
  62                 /// @todo FIXME: this sort of dupes some code in WebRequest::getRequestUrl()
  63                 if ( isset( $_SERVER['REQUEST_URI'] ) ) {
  64                         // Strip the query string...
  65                         list( $path ) = explode( '?', $_SERVER['REQUEST_URI'], 2 );
  66                 } elseif ( isset( $_SERVER['SCRIPT_NAME'] ) ) {
  67                         // Probably IIS. QUERY_STRING appears separately.
  68                         $path = $_SERVER['SCRIPT_NAME'];
  69                 } else {
  70                         // Can't get the path from the server? :(
  71                         return '';
  72                 }
  73
  74                 $period = strrpos( $path, '.' );
  75                 if ( $period !== false ) {
  76                         return strtolower( substr( $path, $period ) );
  77                 }
  78                 return '';
  79         }
  80
  81         /**
  82          * Handler that compresses data with gzip if allowed by the Accept header.
  83          *
  84          * Unlike ob_gzhandler, it works for HEAD requests too.
  85          *
  86          * @param string $s Web response output
  87          * @return string
  88          */
  89         private static function handleGzip( $s ) {
  90                 if ( !function_exists( 'gzencode' ) ) {
  91                         wfDebug( __METHOD__ . "() skipping compression (gzencode unavailable)\n" );
  92                         return $s;
  93                 }
  94                 if ( headers_sent() ) {
  95                         wfDebug( __METHOD__ . "() skipping compression (headers already sent)\n" );
  96                         return $s;
  97                 }
  98
  99                 $ext = self::findUriExtension();
 100                 if ( $ext == '.gz' || $ext == '.tgz' ) {
 101                         // Don't do gzip compression if the URL path ends in .gz or .tgz
 102                         // This confuses Safari and triggers a download of the page,
 103                         // even though it's pretty clearly labeled as viewable HTML.
 104                         // Bad Safari! Bad!
 105                         return $s;
 106                 }
 107
 108                 if ( wfClientAcceptsGzip() ) {
 109                         wfDebug( __METHOD__ . "() is compressing output\n" );
 110                         header( 'Content-Encoding: gzip' );
 111                         $s = gzencode( $s, 6 );
 112                 }
 113
 114                 // Set vary header if it hasn't been set already
 115                 $headers = headers_list();
 116                 $foundVary = false;
 117                 foreach ( $headers as $header ) {
 118                         $headerName = strtolower( substr( $header, 0, 5 ) );
 119                         if ( $headerName == 'vary:' ) {
 120                                 $foundVary = true;
 121                                 break;
 122                         }
 123                 }
 124                 if ( !$foundVary ) {
 125                         header( 'Vary: Accept-Encoding' );
 126                         global $wgUseKeyHeader;
 127                         if ( $wgUseKeyHeader ) {
 128                                 header( 'Key: Accept-Encoding;match=gzip' );
 129                         }
 130                 }
 131                 return $s;
 132         }
 133
 134         /**
 135          * Mangle flash policy tags which open up the site to XSS attacks.
 136          *
 137          * @param string $s Web response output
 138          * @return string
 139          */
 140         private static function mangleFlashPolicy( $s ) {
 141                 # Avoid weird excessive memory usage in PCRE on big articles
 142                 if ( preg_match( '/\<\s*cross-domain-policy(?=\s|\>)/i', $s ) ) {
 143                         return preg_replace( '/\<(\s*)(cross-domain-policy(?=\s|\>))/i', '<$1NOT-$2', $s );
 144                 } else {
 145                         return $s;
 146                 }
 147         }
 148
 149         /**
 150          * Add a Content-Length header if possible. This makes it cooperate with CDN better.
 151          *
 152          * @param int $length
 153          */
 154         private static function emitContentLength( $length ) {
 155                 if ( !headers_sent()
 156                         && isset( $_SERVER['SERVER_PROTOCOL'] )
 157                         && $_SERVER['SERVER_PROTOCOL'] == 'HTTP/1.0'
 158                 ) {
 159                         header( "Content-Length: $length" );
 160                 }
 161         }
 162 }