1 files changed, 21 insertions, 22 deletions

diff --git a/lib/private/User/DisplayNameCache.php b/lib/private/User/DisplayNameCache.php
index 22a79863e49..4321d95f88e 100644
--- a/lib/private/User/DisplayNameCache.php
+++ b/lib/private/User/DisplayNameCache.php
@@ -1,34 +1,20 @@
 <?php
 
 declare(strict_types=1);
-
 /**
- * @copyright Copyright 2022 Carl Schwan <carl@carlschwan.eu>
- * @license AGPL-3.0-or-later
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
+ * SPDX-FileCopyrightText: 2022 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-
-
 namespace OC\User;
 
 use OCP\EventDispatcher\Event;
 use OCP\EventDispatcher\IEventListener;
 use OCP\ICache;
 use OCP\ICacheFactory;
+use OCP\IUser;
 use OCP\IUserManager;
 use OCP\User\Events\UserChangedEvent;
+use OCP\User\Events\UserDeletedEvent;
 
 /**
  * Class that cache the relation UserId -> Display name
@@ -36,8 +22,11 @@ use OCP\User\Events\UserChangedEvent;
  * This saves fetching the user from a user backend and later on fetching
  * their preferences. It's generally not an issue if this data is slightly
  * outdated.
+ * @template-implements IEventListener<UserChangedEvent|UserDeletedEvent>
  */
 class DisplayNameCache implements IEventListener {
+	private const CACHE_TTL = 24 * 60 * 60; // 1 day
+
 	private array $cache = [];
 	private ICache $memCache;
 	private IUserManager $userManager;
@@ -47,10 +36,15 @@ class DisplayNameCache implements IEventListener {
 		$this->userManager = $userManager;
 	}
 
-	public function getDisplayName(string $userId) {
+	public function getDisplayName(string $userId): ?string {
 		if (isset($this->cache[$userId])) {
 			return $this->cache[$userId];
 		}
+
+		if (strlen($userId) > IUser::MAX_USERID_LENGTH) {
+			return null;
+		}
+
 		$displayName = $this->memCache->get($userId);
 		if ($displayName) {
 			$this->cache[$userId] = $displayName;
@@ -61,10 +55,10 @@ class DisplayNameCache implements IEventListener {
 		if ($user) {
 			$displayName = $user->getDisplayName();
 		} else {
-			$displayName = $userId;
+			$displayName = null;
 		}
 		$this->cache[$userId] = $displayName;
-		$this->memCache->set($userId, $displayName, 60 * 10); // 10 minutes
+		$this->memCache->set($userId, $displayName, self::CACHE_TTL);
 
 		return $displayName;
 	}
@@ -79,7 +73,12 @@ class DisplayNameCache implements IEventListener {
 			$userId = $event->getUser()->getUID();
 			$newDisplayName = $event->getValue();
 			$this->cache[$userId] = $newDisplayName;
-			$this->memCache->set($userId, $newDisplayName, 60 * 10); // 10 minutes
+			$this->memCache->set($userId, $newDisplayName, self::CACHE_TTL);
+		}
+		if ($event instanceof UserDeletedEvent) {
+			$userId = $event->getUser()->getUID();
+			unset($this->cache[$userId]);
+			$this->memCache->remove($userId);
 		}
 	}
 }