From 6259a6182aa2982da80e6b9ecb49cff35cdfa30c Mon Sep 17 00:00:00 2001
From: hamza <hamzamahjoubi221@gmail.com>
Date: Wed, 28 Oct 2026 17:11:15 +0100
Subject: [PATCH] fix(UserBackend): do not provision accounts that exist in
 another backend

Assisted-by: ClaudeCode:claude-fable-5-1

Signed-off-by: hamza <hamzamahjoubi221@gmail.com>
---
 lib/UserBackend.php                |  6 ++++--
 tests/unit/lib/UserBackendTest.php | 12 ++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/lib/UserBackend.php b/lib/UserBackend.php
index dd9c199..e2e60ec 100644
--- a/lib/UserBackend.php
+++ b/lib/UserBackend.php
@@ -59,10 +59,12 @@ public function getBackendName(): string {
 	}
 
 	/**
-	 * Creates a user if it does not exist.
+	 * Creates a user if it does not exist in this or any other user backend.
 	 */
 	public function createUserIfNotExists(string $uid, bool $firstLoginIfNeeded = true): void {
-		if (!$this->loadUser($uid)) {
+		if (!$this->loadUser($uid) && $this->userManager->userExists($uid)) {
+			$this->logger->warning('Account "' . $uid . '" exists in another user backend, not provisioning it by global scale', ['app' => Application::APP_ID]);
+		} elseif (!$this->loadUser($uid)) {
 			$values = [
 				'uid' => $uid,
 			];
diff --git a/tests/unit/lib/UserBackendTest.php b/tests/unit/lib/UserBackendTest.php
index d1b2525..a12fe97 100644
--- a/tests/unit/lib/UserBackendTest.php
+++ b/tests/unit/lib/UserBackendTest.php
@@ -95,6 +95,18 @@ public function testCreateExistingUserWritesNoAuditLog(): void {
 		$this->getBackend(true)->createUserIfNotExists('alice', false);
 	}
 
+	public function testCreateUserKnownToOtherBackendInsertsNothing(): void {
+		$this->userManager->expects($this->once())
+			->method('userExists')
+			->with('alice')
+			->willReturn(true);
+		$this->db->expects($this->never())->method('getQueryBuilder');
+		$this->auditLogService->expects($this->never())->method('log');
+		$this->stopAtHomeSetup();
+
+		$this->getBackend(false)->createUserIfNotExists('alice', false);
+	}
+
 	private function prepareGroups(array $currentGroups): void {
 		$user = $this->createMock(IUser::class);
 		$user->method('getUID')->willReturn('alice');