Merge pull request #51253 from nextcloud/backport/50989/stable29

[stable29] fix: Use case insensitive check when validating login name

Author: AndyScherzinger

lib/private/User/Session.php

@@ -810,7 +810,7 @@ private function validateToken($token, $user = null) {
 	 * Check if login names match
 	 */
 	private function validateTokenLoginName(?string $loginName, IToken $token): bool {
-		if ($token->getLoginName() !== $loginName) {
+		if (mb_strtolower($token->getLoginName()) !== mb_strtolower($loginName ?? '')) {
 			// TODO: this makes it impossible to use different login names on browser and client
 			// e.g. login by e-mail 'user@example.com' on browser for generating the token will not
 			//      allow to use the client token with the login name 'user'.