add switch to enable/disable the possibility to change the display name by the user

config/config.sample.php

@@ -114,6 +114,9 @@ $CONFIG = array(
 /* How long should ownCloud keep deleted files in the trash bin, default value:  180 days */
 'trashbin_retention_obligation' => 180,
 
+/* allow user to change his display name, if it is supported by the back-end */
+'allow_user_to_change_display_name' => true,
+
 /* Check 3rdparty apps for malicious code fragments */
 "appcodechecker" => "",
 

lib/user.php

@@ -445,10 +445,12 @@ class OC_User {
 	 * Check whether a specified user can change his display name
 	 */
 	public static function canUserChangeDisplayName($uid) {
-		foreach(self::$_usedBackends as $backend) {
-			if($backend->implementsActions(OC_USER_BACKEND_SET_DISPLAYNAME)) {
-				if($backend->userExists($uid)) {
-					return true;
+		if (OC_Config::getValue('allow_user_to_change_display_name', true)) {
+			foreach(self::$_usedBackends as $backend) {
+				if($backend->implementsActions(OC_USER_BACKEND_SET_DISPLAYNAME)) {
+					if($backend->userExists($uid)) {
+						return true;
+					}
 				}
 			}
 		}

settings/ajax/changedisplayname.php

@@ -15,6 +15,10 @@ if(OC_SubAdmin::isUserAccessible(OC_User::getUser(), $username)) {
 	$userstatus = 'subadmin';
 }
 
+if ($username == OC_User::getUser() && OC_User::canUserChangeDisplayName($username)) {
+	$userstatus = 'changeOwnDisplayName';
+}
+
 if(is_null($userstatus)) {
 	OC_JSON::error( array( "data" => array( "message" => $l->t("Authentication error") )));
 	exit();