fix: Make user removal more resilient

Currently there is a problem if an exception is thrown in `User::delete`,
because at that point the user is already removed from the backend,
but not all data is deleted.

There is no way to recover from this state, as the user is gone no information is available anymore.
This means the data is still available on the server but can not removed by any API anymore.

The solution here is to first set a flag and backup the user home,
this can be used to recover failed user deletions in a way the delete can be re-tried.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

1 files changed, 14 insertions, 8 deletions

diff --git a/lib/private/Authentication/Listeners/UserDeletedFilesCleanupListener.php b/lib/private/Authentication/Listeners/UserDeletedFilesCleanupListener.php
index 8523fb6abc7..a619021d192 100644
--- a/lib/private/Authentication/Listeners/UserDeletedFilesCleanupListener.php
+++ b/lib/private/Authentication/Listeners/UserDeletedFilesCleanupListener.php
@@ -16,27 +16,31 @@ use OCP\Files\Config\IMountProviderCollection;
 use OCP\Files\Storage\IStorage;
 use OCP\User\Events\BeforeUserDeletedEvent;
 use OCP\User\Events\UserDeletedEvent;
+use Psr\Log\LoggerInterface;
 
 /** @template-implements IEventListener<BeforeUserDeletedEvent|UserDeletedEvent> */
 class UserDeletedFilesCleanupListener implements IEventListener {
 	/** @var array<string,IStorage> */
 	private $homeStorageCache = [];
 
-	/** @var IMountProviderCollection */
-	private $mountProviderCollection;
-
-	public function __construct(IMountProviderCollection $mountProviderCollection) {
-		$this->mountProviderCollection = $mountProviderCollection;
+	public function __construct(
+		private IMountProviderCollection $mountProviderCollection,
+		private LoggerInterface $logger,
+	) {
 	}
 
 	public function handle(Event $event): void {
+		$user = $event->getUser();
+
 		// since we can't reliably get the user home storage after the user is deleted
 		// but the user deletion might get canceled during the before event
 		// we only cache the user home storage during the before event and then do the
 		// action deletion during the after event
 
 		if ($event instanceof BeforeUserDeletedEvent) {
-			$userHome = $this->mountProviderCollection->getHomeMountForUser($event->getUser());
+			$this->logger->debug('Prepare deleting storage for user {userId}', ['userId' => $user->getUID()]);
+
+			$userHome = $this->mountProviderCollection->getHomeMountForUser($user);
 			$storage = $userHome->getStorage();
 			if (!$storage) {
 				throw new \Exception('Account has no home storage');
@@ -51,12 +55,14 @@ class UserDeletedFilesCleanupListener implements IEventListener {
 			$this->homeStorageCache[$event->getUser()->getUID()] = $storage;
 		}
 		if ($event instanceof UserDeletedEvent) {
-			if (!isset($this->homeStorageCache[$event->getUser()->getUID()])) {
+			if (!isset($this->homeStorageCache[$user->getUID()])) {
 				throw new \Exception('UserDeletedEvent fired without matching BeforeUserDeletedEvent');
 			}
-			$storage = $this->homeStorageCache[$event->getUser()->getUID()];
+			$storage = $this->homeStorageCache[$user->getUID()];
 			$cache = $storage->getCache();
 			$storage->rmdir('');
+			$this->logger->debug('Deleted storage for user {userId}', ['userId' => $user->getUID()]);
+
 			if ($cache instanceof Cache) {
 				$cache->clear();
 			} else {