Add some safety checks

apps/files_sharing/ajax/external.php

@@ -8,6 +8,7 @@
 
 OCP\JSON::callCheck();
 OCP\JSON::checkLoggedIn();
+OCP\JSON::checkAppEnabled('files_sharing');
 
 $l = OC_L10N::get('files_sharing');
 

apps/files_sharing/ajax/shareinfo.php

@@ -6,9 +6,7 @@
  * See the COPYING-README file.
  */
 
-if (!\OC_App::isEnabled('files_sharing')) {
-	exit;
-}
+OCP\JSON::checkAppEnabled('files_sharing');
 
 if (!isset($_GET['t'])) {
 	\OC_Response::setStatus(400); //400 Bad Request

apps/files_sharing/ajax/testremote.php

@@ -6,12 +6,16 @@
  * See the COPYING-README file.
  */
 
+OCP\JSON::checkAppEnabled('files_sharing');
+OCP\JSON::checkLoggedIn();
+OCP\JSON::callCheck();
+
 $remote = $_GET['remote'];
 
 if (file_get_contents('https://' . $remote . '/status.php')) {
 	echo 'https';
 } elseif (file_get_contents('http://' . $remote . '/status.php')) {
 	echo 'http';
-}else{
+} else {
 	echo 'false';
 }