HeaderCallback.php

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<?php
 
namespace MediaWiki\Request;
 
use MediaWiki\Debug\MWDebug;
use MediaWiki\Http\Telemetry;
use MediaWiki\Logger\LoggerFactory;
use RuntimeException;
 
class HeaderCallback {
    private static $headersSentException;
    private static $messageSent = false;
 
    public static function register() {
        // T261260 load the WebRequest class, which will be needed in callback().
        // Autoloading seems unreliable in header callbacks, and in the case of a web
        // request (ie. in all cases where the request might be performance-sensitive)
        // it will have to be loaded at some point anyway.
        // This can be removed once we require PHP 8.0+.
        class_exists( WebRequest::class );
        class_exists( Telemetry::class );
 
        header_register_callback( [ __CLASS__, 'callback' ] );
    }
 
    public static function callback() {
        // Prevent caching of responses with cookies (T127993)
        $headers = [];
        foreach ( headers_list() as $header ) {
            $header = explode( ':', $header, 2 );
 
            // Note: The code below (currently) does not care about value-less headers
            if ( isset( $header[1] ) ) {
                $headers[ strtolower( trim( $header[0] ) ) ][] = trim( $header[1] );
            }
        }
 
        if ( isset( $headers['set-cookie'] ) ) {
            $cacheControl = isset( $headers['cache-control'] )
                ? implode( ', ', $headers['cache-control'] )
                : '';
 
            if ( !preg_match( '/(?:^|,)\s*(?:private|no-cache|no-store)\s*(?:$|,)/i',
                $cacheControl )
            ) {
                header( 'Expires: Thu, 01 Jan 1970 00:00:00 GMT' );
                header( 'Cache-Control: private, max-age=0, s-maxage=0' );
                LoggerFactory::getInstance( 'cache-cookies' )->warning(
                    'Cookies set on {url} with Cache-Control "{cache-control}"', [
                        'url' => WebRequest::getGlobalRequestURL(),
                        'set-cookie' => self::sanitizeSetCookie( $headers['set-cookie'] ),
                        'cache-control' => $cacheControl ?: '<not set>',
                    ]
                );
            }
        }
 
        $telemetryHeaders = Telemetry::getInstance()->getRequestHeaders();
        // Set the request ID/trace prams on the response, so edge infrastructure can log it.
        // FIXME this is not an ideal place to do it, but the most reliable for now.
        foreach ( $telemetryHeaders as $header => $value ) {
            if ( !isset( $headers[strtolower( $header )] ) ) {
                header( "$header: $value" );
            }
        }
 
        // Save a backtrace for logging in case it turns out that headers were sent prematurely
        self::$headersSentException = new RuntimeException( 'Headers already sent from this point' );
    }
 
    public static function warnIfHeadersSent() {
        if ( !self::$messageSent && headers_sent( $filename, $line ) ) {
            self::$messageSent = true;
            MWDebug::warning( 'Headers already sent, should send headers earlier than ' .
                wfGetCaller( 3 ) );
            $logger = LoggerFactory::getInstance( 'headers-sent' );
            $logger->error( 'Warning: headers were already sent (output started at ' . $filename . ':' . $line . ')', [
                'exception' => self::$headersSentException,
                'detection-trace' => new RuntimeException( 'Detected here' ),
            ] );
        }
    }
 
    public static function sanitizeSetCookie( array $values ) {
        $sanitizedValues = [];
        foreach ( $values as $value ) {
            // Set-Cookie header format: <cookie-name>=<cookie-value>; <non-sensitive attributes>
            $parts = explode( ';', $value );
            [ $name, $value ] = explode( '=', $parts[0], 2 );
            if ( strlen( $value ) > 8 ) {
                $value = substr( $value, 0, 8 ) . '...';
                $parts[0] = "$name=$value";
            }
            $sanitizedValues[] = implode( ';', $parts );
        }
        return implode( "\n", $sanitizedValues );
    }
}