MWExceptionRenderer.php

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<?php
use MediaWiki\Html\Html;
use MediaWiki\Language\RawMessage;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Request\WebRequest;
use Wikimedia\AtEase;
use Wikimedia\Rdbms\DBConnectionError;
use Wikimedia\Rdbms\DBExpectedError;
use Wikimedia\Rdbms\DBReadOnlyError;
use Wikimedia\RequestTimeout\RequestTimeoutException;
 
class MWExceptionRenderer {
    public const AS_RAW = 1; // show as text
    public const AS_PRETTY = 2; // show as HTML
 
    private static $showExceptionDetails = false;
 
    public static function shouldShowExceptionDetails(): bool {
        return self::$showExceptionDetails;
    }
 
    public static function setShowExceptionDetails( bool $showDetails ): void {
        self::$showExceptionDetails = $showDetails;
    }
 
    public static function output( Throwable $e, $mode, Throwable $eNew = null ) {
        $showExceptionDetails = self::shouldShowExceptionDetails();
        if ( $e instanceof RequestTimeoutException && headers_sent() ) {
            // Excimer's flag check happens on function return, so, a timeout
            // can be thrown after exiting, say, `doPostOutputShutdown`, where
            // headers are sent.  In which case, it's probably fine not to
            // report this in any user visible way.  The general question of
            // what to do about reporting an exception when headers have been
            // sent is still unclear, but you probably don't want to
            // `useOutputPage`.
            return;
        }
 
        if ( function_exists( 'apache_setenv' ) ) {
            // The client should not be blocked on "post-send" updates. If apache decides that
            // a response should be gzipped, it will wait for PHP to finish since it cannot gzip
            // anything until it has the full response (even with "Transfer-Encoding: chunked").
            AtEase\AtEase::suppressWarnings();
            apache_setenv( 'no-gzip', '1' );
            AtEase\AtEase::restoreWarnings();
        }
 
        if ( defined( 'MW_API' ) ) {
            self::header( 'MediaWiki-API-Error: internal_api_error_' . get_class( $e ) );
        }
 
        if ( self::isCommandLine() ) {
            self::printError( self::getText( $e ) );
        } elseif ( $mode === self::AS_PRETTY ) {
            self::statusHeader( 500 );
            ob_start();
            if ( $e instanceof DBConnectionError ) {
                self::reportOutageHTML( $e );
            } else {
                self::reportHTML( $e );
            }
            self::header( "Content-Length: " . ob_get_length() );
            ob_end_flush();
        } else {
            ob_start();
            self::statusHeader( 500 );
            self::header( 'Content-Type: text/html; charset=UTF-8' );
            if ( $eNew ) {
                $message = "MediaWiki internal error.\n\n";
                if ( $showExceptionDetails ) {
                    $message .= 'Original exception: ' .
                        MWExceptionHandler::getLogMessage( $e ) .
                        "\nBacktrace:\n" . MWExceptionHandler::getRedactedTraceAsString( $e ) .
                        "\n\nException caught inside exception handler: " .
                            MWExceptionHandler::getLogMessage( $eNew ) .
                        "\nBacktrace:\n" . MWExceptionHandler::getRedactedTraceAsString( $eNew );
                } else {
                    $message .= 'Original exception: ' .
                        MWExceptionHandler::getPublicLogMessage( $e );
                    $message .= "\n\nException caught inside exception handler.\n\n" .
                        self::getShowBacktraceError();
                }
                $message .= "\n";
            } elseif ( $showExceptionDetails ) {
                $message = MWExceptionHandler::getLogMessage( $e ) .
                    "\nBacktrace:\n" .
                    MWExceptionHandler::getRedactedTraceAsString( $e ) . "\n";
            } else {
                $message = MWExceptionHandler::getPublicLogMessage( $e );
            }
            print nl2br( htmlspecialchars( $message ) ) . "\n";
            self::header( "Content-Length: " . ob_get_length() );
            ob_end_flush();
        }
    }
 
    private static function useOutputPage( Throwable $e ) {
        // Can the exception use the Message class/wfMessage to get i18n-ed messages?
        foreach ( $e->getTrace() as $frame ) {
            if ( isset( $frame['class'] ) && $frame['class'] === LocalisationCache::class ) {
                return false;
            }
        }
 
        // Don't even bother with OutputPage if there's no Title context set,
        // (e.g. we're in RL code on load.php) - the Skin system (and probably
        // most of MediaWiki) won't work.
 
        // NOTE: keep in sync with MWException::useOutputPage
        return (
            !empty( $GLOBALS['wgFullyInitialised'] ) &&
            !empty( $GLOBALS['wgOut'] ) &&
            RequestContext::getMain()->getTitle() &&
            !defined( 'MEDIAWIKI_INSTALL' ) &&
            // Don't send a skinned HTTP 500 page to API clients.
            !defined( 'MW_API' ) &&
            !defined( 'MW_REST_API' )
        );
    }
 
    private static function reportHTML( Throwable $e ) {
        if ( self::useOutputPage( $e ) ) {
            $out = RequestContext::getMain()->getOutput();
            $out->prepareErrorPage();
            $out->setPageTitleMsg( self::getExceptionTitle( $e ) );
 
            // Show any custom GUI message before the details
            $customMessage = self::getCustomMessage( $e );
            if ( $customMessage !== null ) {
                $out->addHTML( Html::element( 'p', [], $customMessage ) );
            }
            $out->addHTML( self::getHTML( $e ) );
            // Content-Type is set by OutputPage::output
            $out->output();
        } else {
            self::header( 'Content-Type: text/html; charset=UTF-8' );
            $pageTitle = self::msg( 'internalerror', 'Internal error' );
            echo "<!DOCTYPE html>\n" .
                '<html><head>' .
                // Mimic OutputPage::setPageTitle behaviour
                '<title>' .
                htmlspecialchars( self::msg( 'pagetitle', '$1 - MediaWiki', $pageTitle ) ) .
                '</title>' .
                '<style>body { font-family: sans-serif; margin: 0; padding: 0.5em 2em; }</style>' .
                "</head><body>\n";
 
            echo self::getHTML( $e );
 
            echo "</body></html>\n";
        }
    }
 
    public static function getHTML( Throwable $e ) {
        if ( self::shouldShowExceptionDetails() ) {
            $html = Html::errorBox( "<p>" .
                nl2br( htmlspecialchars( MWExceptionHandler::getLogMessage( $e ) ) ) .
                '</p><p>Backtrace:</p><p>' .
                nl2br( htmlspecialchars( MWExceptionHandler::getRedactedTraceAsString( $e ) ) ) .
                "</p>\n",
                '',
                'mw-content-ltr'
            );
        } else {
            $logId = WebRequest::getRequestId();
            $html = Html::errorBox(
                htmlspecialchars(
                    '[' . $logId . '] ' .
                    gmdate( 'Y-m-d H:i:s' ) . ": " .
                    self::msg( "internalerror-fatal-exception",
                        "Fatal exception of type $1",
                        get_class( $e ),
                        $logId,
                        MWExceptionHandler::getURL()
                ) ),
                '',
                'mw-content-ltr'
            ) . "<!-- " . wordwrap( self::getShowBacktraceError(), 50 ) . " -->";
        }
 
        return $html;
    }
 
    public static function msg( $key, $fallback, ...$params ) {
        // NOTE: Keep logic in sync with MWException::msg
        $res = self::msgObj( $key, $fallback, ...$params )->text();
        return strtr( $res, [
            '{{SITENAME}}' => 'MediaWiki',
        ] );
    }
 
    private static function msgObj( string $key, string $fallback, ...$params ): Message {
        // NOTE: Keep logic in sync with MWException::msg.
        try {
            $res = wfMessage( $key, ...$params );
        } catch ( Exception $e ) {
            // Fallback to static message text and generic sitename.
            // Avoid live config as this must work before Setup/MediaWikiServices finish.
            $res = new RawMessage( $fallback, $params );
        }
        return $res;
    }
 
    private static function getText( Throwable $e ) {
        // XXX: do we need a parameter to control inclusion of exception details?
        if ( self::shouldShowExceptionDetails() ) {
            return MWExceptionHandler::getLogMessage( $e ) .
                "\nBacktrace:\n" .
                MWExceptionHandler::getRedactedTraceAsString( $e ) . "\n";
        } else {
            return self::getShowBacktraceError() . "\n";
        }
    }
 
    private static function getShowBacktraceError() {
        $var = '$wgShowExceptionDetails = true;';
        return "Set $var at the bottom of LocalSettings.php to show detailed debugging information.";
    }
 
    private static function getExceptionTitle( Throwable $e ): Message {
        if ( $e instanceof MWException ) {
            return ( new RawMessage( '$1' ) )->plaintextParams(
                $e->getPageTitle() /* convert string title to Message */
            );
        } elseif ( $e instanceof DBReadOnlyError ) {
            return self::msgObj( 'readonly', 'Database is locked' );
        } elseif ( $e instanceof DBExpectedError ) {
            return self::msgObj( 'databaseerror', 'Database error' );
        } elseif ( $e instanceof RequestTimeoutException ) {
            return self::msgObj( 'timeouterror', 'Request timeout' );
        } else {
            return self::msgObj( 'internalerror', 'Internal error' );
        }
    }
 
    private static function getCustomMessage( Throwable $e ) {
        try {
            if ( $e instanceof MessageSpecifier ) {
                $msg = Message::newFromSpecifier( $e );
            } elseif ( $e instanceof RequestTimeoutException ) {
                $msg = wfMessage( 'timeouterror-text', $e->getLimit() );
            } else {
                return null;
            }
            $text = $msg->text();
        } catch ( Exception $e2 ) {
            return null;
        }
        return $text;
    }
 
    private static function isCommandLine() {
        return !empty( $GLOBALS['wgCommandLineMode'] );
    }
 
    private static function header( $header ) {
        if ( !headers_sent() ) {
            header( $header );
        }
    }
 
    private static function statusHeader( $code ) {
        if ( !headers_sent() ) {
            HttpStatus::header( $code );
        }
    }
 
    private static function printError( $message ) {
        // NOTE: STDERR may not be available, especially if php-cgi is used from the
        // command line (T17602). Try to produce meaningful output anyway. Using
        // echo may corrupt output to STDOUT though.
        if ( defined( 'STDERR' ) ) {
            fwrite( STDERR, $message );
        } else {
            echo $message;
        }
    }
 
    private static function reportOutageHTML( Throwable $e ) {
        $mainConfig = MediaWikiServices::getInstance()->getMainConfig();
        $showExceptionDetails = $mainConfig->get( MainConfigNames::ShowExceptionDetails );
        $showHostnames = $mainConfig->get( MainConfigNames::ShowHostnames );
        $sorry = htmlspecialchars( self::msg(
            'dberr-problems',
            'Sorry! This site is experiencing technical difficulties.'
        ) );
        $again = htmlspecialchars( self::msg(
            'dberr-again',
            'Try waiting a few minutes and reloading.'
        ) );
 
        if ( $showHostnames ) {
            $info = str_replace(
                '$1',
                Html::element( 'span', [ 'dir' => 'ltr' ], $e->getMessage() ),
                htmlspecialchars( self::msg( 'dberr-info', '($1)' ) )
            );
        } else {
            $info = htmlspecialchars( self::msg(
                'dberr-info-hidden',
                '(Cannot access the database)'
            ) );
        }
 
        MediaWikiServices::getInstance()->getMessageCache()->disable(); // no DB access
        $html = "<!DOCTYPE html>\n" .
                '<html><head>' .
                '<title>MediaWiki</title>' .
                '<style>body { font-family: sans-serif; margin: 0; padding: 0.5em 2em; }</style>' .
                "</head><body><h1>$sorry</h1><p>$again</p><p><small>$info</small></p>";
 
        if ( $showExceptionDetails ) {
            $html .= '<p>Backtrace:</p><pre>' .
                htmlspecialchars( $e->getTraceAsString() ) . '</pre>';
        }
 
        $html .= '</body></html>';
        self::header( 'Content-Type: text/html; charset=UTF-8' );
        echo $html;
    }
}