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 /**
  24  * Standard output handler for use with ob_start
  25  *
  26  * @param $s string
  27  *
  28  * @return string
  29  */
  30 function wfOutputHandler( $s ) {
  31         global $wgDisableOutputCompression, $wgValidateAllHtml;
  32         $s = wfMangleFlashPolicy( $s );
  33         if ( $wgValidateAllHtml ) {
  34                 $headers = apache_response_headers();
  35                 $isHTML = true;
  36                 foreach ( $headers as $name => $value ) {
  37                         if ( strtolower( $name ) == 'content-type' && strpos( $value, 'text/html' ) === false && strpos( $value, 'application/xhtml+xml' ) === false ) {
  38                                 $isHTML = false;
  39                                 break;
  40                         }
  41                 }
  42                 if ( $isHTML ) {
  43                         $s = wfHtmlValidationHandler( $s );
  44                 }
  45         }
  46         if ( !$wgDisableOutputCompression && !ini_get( 'zlib.output_compression' ) ) {
  47                 if ( !defined( 'MW_NO_OUTPUT_COMPRESSION' ) ) {
  48                         $s = wfGzipHandler( $s );
  49                 }
  50                 if ( !ini_get( 'output_handler' ) ) {
  51                         wfDoContentLength( strlen( $s ) );
  52                 }
  53         }
  54         return $s;
  55 }
  56
  57 /**
  58  * Get the "file extension" that some client apps will estimate from
  59  * the currently-requested URL.
  60  * This isn't on WebRequest because we need it when things aren't initialized
  61  * @private
  62  *
  63  * @return string
  64  */
  65 function wfRequestExtension() {
  66         /// @todo FIXME: this sort of dupes some code in WebRequest::getRequestUrl()
  67         if( isset( $_SERVER['REQUEST_URI'] ) ) {
  68                 // Strip the query string...
  69                 list( $path ) = explode( '?', $_SERVER['REQUEST_URI'], 2 );
  70         } elseif( isset( $_SERVER['SCRIPT_NAME'] ) ) {
  71                 // Probably IIS. QUERY_STRING appears separately.
  72                 $path = $_SERVER['SCRIPT_NAME'];
  73         } else {
  74                 // Can't get the path from the server? :(
  75                 return '';
  76         }
  77
  78         $period = strrpos( $path, '.' );
  79         if( $period !== false ) {
  80                 return strtolower( substr( $path, $period ) );
  81         }
  82         return '';
  83 }
  84
  85 /**
  86  * Handler that compresses data with gzip if allowed by the Accept header.
  87  * Unlike ob_gzhandler, it works for HEAD requests too.
  88  *
  89  * @param $s string
  90  *
  91  * @return string
  92  */
  93 function wfGzipHandler( $s ) {
  94         if( !function_exists( 'gzencode' ) ) {
  95                 wfDebug( __FUNCTION__ . "() skipping compression (gzencode unavailable)\n" );
  96                 return $s;
  97         }
  98         if( headers_sent() ) {
  99                 wfDebug( __FUNCTION__ . "() skipping compression (headers already sent)\n" );
 100                 return $s;
 101         }
 102
 103         $ext = wfRequestExtension();
 104         if( $ext == '.gz' || $ext == '.tgz' ) {
 105                 // Don't do gzip compression if the URL path ends in .gz or .tgz
 106                 // This confuses Safari and triggers a download of the page,
 107                 // even though it's pretty clearly labeled as viewable HTML.
 108                 // Bad Safari! Bad!
 109                 return $s;
 110         }
 111
 112         if( wfClientAcceptsGzip() ) {
 113                 wfDebug( __FUNCTION__ . "() is compressing output\n" );
 114                 header( 'Content-Encoding: gzip' );
 115                 $s = gzencode( $s, 6 );
 116         }
 117
 118         // Set vary header if it hasn't been set already
 119         $headers = headers_list();
 120         $foundVary = false;
 121         foreach ( $headers as $header ) {
 122                 if ( substr( $header, 0, 5 ) == 'Vary:' ) {
 123                         $foundVary = true;
 124                         break;
 125                 }
 126         }
 127         if ( !$foundVary ) {
 128                 header( 'Vary: Accept-Encoding' );
 129                 global $wgUseXVO;
 130                 if ( $wgUseXVO ) {
 131                         header( 'X-Vary-Options: Accept-Encoding;list-contains=gzip' );
 132                 }
 133         }
 134         return $s;
 135 }
 136
 137 /**
 138  * Mangle flash policy tags which open up the site to XSS attacks.
 139  *
 140  * @param $s string
 141  *
 142  * @return string
 143  */
 144 function wfMangleFlashPolicy( $s ) {
 145         # Avoid weird excessive memory usage in PCRE on big articles
 146         if ( preg_match( '/\<\s*cross-domain-policy\s*\>/i', $s ) ) {
 147                 return preg_replace( '/\<\s*cross-domain-policy\s*\>/i', '<NOT-cross-domain-policy>', $s );
 148         } else {
 149                 return $s;
 150         }
 151 }
 152
 153 /**
 154  * Add a Content-Length header if possible. This makes it cooperate with squid better.
 155  *
 156  * @param $length int
 157  */
 158 function wfDoContentLength( $length ) {
 159         if ( !headers_sent() && isset( $_SERVER['SERVER_PROTOCOL'] ) && $_SERVER['SERVER_PROTOCOL'] == 'HTTP/1.0' ) {
 160                 header( "Content-Length: $length" );
 161         }
 162 }
 163
 164 /**
 165  * Replace the output with an error if the HTML is not valid
 166  *
 167  * @param $s string
 168  *
 169  * @return string
 170  */
 171 function wfHtmlValidationHandler( $s ) {
 172
 173         $errors = '';
 174         if ( MWTidy::checkErrors( $s, $errors ) ) {
 175                 return $s;
 176         }
 177
 178         header( 'Cache-Control: no-cache' );
 179
 180         $out = <<<EOT
 181 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 182 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" dir="ltr">
 183 <head>
 184 <title>HTML validation error</title>
 185 <style>
 186 .highlight { background-color: #ffc }
 187 li { white-space: pre }
 188 </style>
 189 </head>
 190 <body>
 191 <h1>HTML validation error</h1>
 192 <ul>
 193 EOT;
 194
 195         $error = strtok( $errors, "\n" );
 196         $badLines = array();
 197         while ( $error !== false ) {
 198                 if ( preg_match( '/^line (\d+)/', $error, $m ) ) {
 199                         $lineNum = intval( $m[1] );
 200                         $badLines[$lineNum] = true;
 201                         $out .= "<li><a href=\"#line-{$lineNum}\">" . htmlspecialchars( $error ) . "</a></li>\n";
 202                 }
 203                 $error = strtok( "\n" );
 204         }
 205
 206         $out .= '</ul>';
 207         $out .= '<pre>' . htmlspecialchars( $errors ) . '</pre>';
 208         $out .= "<ol>\n";
 209         $line = strtok( $s, "\n" );
 210         $i = 1;
 211         while ( $line !== false ) {
 212                 if ( isset( $badLines[$i] ) ) {
 213                         $out .= "<li class=\"highlight\" id=\"line-$i\">";
 214                 } else {
 215                         $out .= '<li>';
 216                 }
 217                 $out .= htmlspecialchars( $line ) . "</li>\n";
 218                 $line = strtok( "\n" );
 219                 $i++;
 220         }
 221         $out .= '</ol></body></html>';
 222         return $out;
 223 }