server/public.php

<?php

try {

	require_once 'lib/base.php';
	if (\OCP\Util::needUpgrade()) {
		// since the behavior of apps or remotes are unpredictable during
		// an upgrade, return a 503 directly
		OC_Response::setStatus(OC_Response::STATUS_SERVICE_UNAVAILABLE);
		OC_Template::printErrorPage('Service unavailable');
		exit;
	}

	OC::checkMaintenanceMode();
	OC::checkSingleUserMode();
	$request = \OC::$server->getRequest();
	$pathInfo = $request->getPathInfo();

	if (!$pathInfo && $request->getParam('service', '') === '') {
		header('HTTP/1.0 404 Not Found');
		exit;
	} elseif ($request->getParam('service', '')) {
		$service = $request->getParam('service', '');
	} else {
		$pathInfo = trim($pathInfo, '/');
		list($service) = explode('/', $pathInfo);
	}
	$file = OCP\CONFIG::getAppValue('core', 'public_' . strip_tags($service));
	if (is_null($file)) {
		header('HTTP/1.0 404 Not Found');
		exit;
	}

	$parts = explode('/', $file, 2);
	$app = $parts[0];

	// Load all required applications
	\OC::$REQUESTEDAPP = $app;
	OC_App::loadApps(array('authentication'));
	OC_App::loadApps(array('filesystem', 'logging'));

	if (!\OC::$server->getAppManager()->isInstalled($app)) {
		throw new Exception('App not installed: ' . $app);
	}
	OC_App::loadApp($app);
	OC_User::setIncognitoMode(true);

	$baseuri = OC::$WEBROOT . '/public.php/' . $service . '/';

	require_once OC_App::getAppPath($app) . '/' . $parts[1];

} catch (\OC\ServiceUnavailableException $ex) {
	//show the user a detailed error page
	OC_Response::setStatus(OC_Response::STATUS_SERVICE_UNAVAILABLE);
	\OCP\Util::writeLog('remote', $ex->getMessage(), \OCP\Util::FATAL);
	OC_Template::printExceptionErrorPage($ex);
} catch (Exception $ex) {
	//show the user a detailed error page
	OC_Response::setStatus(OC_Response::STATUS_INTERNAL_SERVER_ERROR);
	\OCP\Util::writeLog('remote', $ex->getMessage(), \OCP\Util::FATAL);
	OC_Template::printExceptionErrorPage($ex);
}