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<?php
/**
* Functions to be used with PHP's output buffer.
*
* 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 MediaWiki;
/**
* @since 1.31
*/
class OutputHandler {
/**
* Standard output handler for use with ob_start.
*
* @param string $s Web response output
* @param int $phase Flags indicating the reason for the call
* @return string
*/
public static function handle( $s, $phase ) {
global $wgDisableOutputCompression, $wgMangleFlashPolicy;
if ( $phase | PHP_OUTPUT_HANDLER_CLEAN ) {
// Don't send headers if output is being discarded (T278579)
return $s;
}
if ( $wgMangleFlashPolicy ) {
$s = self::mangleFlashPolicy( $s );
}
if ( !$wgDisableOutputCompression && !ini_get( 'zlib.output_compression' ) ) {
if ( !defined( 'MW_NO_OUTPUT_COMPRESSION' ) ) {
$s = self::handleGzip( $s );
}
if ( !ini_get( 'output_handler' ) ) {
self::emitContentLength( strlen( $s ) );
}
}
return $s;
}
/**
* Get the "file extension" that some client apps will estimate from
* the currently-requested URL.
*
* This isn't a WebRequest method, because we need it before the class loads.
* @todo As of 2018, this actually runs after autoloader in Setup.php, so
* WebRequest seems like a good place for this.
*
* @return string
*/
private static function findUriExtension() {
/// @todo FIXME: this sort of dupes some code in WebRequest::getRequestUrl()
if ( isset( $_SERVER['REQUEST_URI'] ) ) {
// Strip the query string...
$path = explode( '?', $_SERVER['REQUEST_URI'], 2 )[0];
} elseif ( isset( $_SERVER['SCRIPT_NAME'] ) ) {
// Probably IIS. QUERY_STRING appears separately.
$path = $_SERVER['SCRIPT_NAME'];
} else {
// Can't get the path from the server? :(
return '';
}
$period = strrpos( $path, '.' );
if ( $period !== false ) {
return strtolower( substr( $path, $period ) );
}
return '';
}
/**
* Handler that compresses data with gzip if allowed by the Accept header.
*
* Unlike ob_gzhandler, it works for HEAD requests too.
*
* @param string $s Web response output
* @return string
*/
private static function handleGzip( $s ) {
if ( !function_exists( 'gzencode' ) ) {
wfDebug( __METHOD__ . "() skipping compression (gzencode unavailable)" );
return $s;
}
if ( headers_sent() ) {
wfDebug( __METHOD__ . "() skipping compression (headers already sent)" );
return $s;
}
$ext = self::findUriExtension();
if ( $ext == '.gz' || $ext == '.tgz' ) {
// Don't do gzip compression if the URL path ends in .gz or .tgz
// This confuses Safari and triggers a download of the page,
// even though it's pretty clearly labeled as viewable HTML.
// Bad Safari! Bad!
return $s;
}
if ( wfClientAcceptsGzip() ) {
wfDebug( __METHOD__ . "() is compressing output" );
header( 'Content-Encoding: gzip' );
$s = gzencode( $s, 6 );
}
// Set vary header if it hasn't been set already
$headers = headers_list();
$foundVary = false;
foreach ( $headers as $header ) {
$headerName = strtolower( substr( $header, 0, 5 ) );
if ( $headerName == 'vary:' ) {
$foundVary = true;
break;
}
}
if ( !$foundVary ) {
header( 'Vary: Accept-Encoding' );
}
return $s;
}
/**
* Mangle flash policy tags which open up the site to XSS attacks.
*
* @param string $s Web response output
* @return string
*/
private static function mangleFlashPolicy( $s ) {
# Avoid weird excessive memory usage in PCRE on big articles
if ( preg_match( '/\<\s*cross-domain-policy(?=\s|\>)/i', $s ) ) {
return preg_replace( '/\<(\s*)(cross-domain-policy(?=\s|\>))/i', '<$1NOT-$2', $s );
} else {
return $s;
}
}
/**
* Add a Content-Length header if possible. This makes it cooperate with CDN better.
*
* @param int $length
*/
private static function emitContentLength( $length ) {
if ( !headers_sent()
&& isset( $_SERVER['SERVER_PROTOCOL'] )
&& $_SERVER['SERVER_PROTOCOL'] == 'HTTP/1.0'
) {
header( "Content-Length: $length" );
}
}
}
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