fix: add some recrusive detection/prevention

Signed-off-by: Robin Appelman <robin@icewind.nl>

apps/files_sharing/lib/SharedStorage.php

@@ -40,6 +40,7 @@
 use OC\Files\Storage\FailedStorage;
 use OC\Files\Storage\Home;
 use OC\Files\Storage\Wrapper\PermissionsMask;
+use OC\Files\Storage\Wrapper\Wrapper;
 use OC\User\DisplayNameCache;
 use OC\User\NoUserException;
 use OCA\Files_External\Config\ExternalMountPoint;
@@ -96,6 +97,8 @@ class SharedStorage extends \OC\Files\Storage\Wrapper\Jail implements ISharedSto
 
 	private string $sourcePath = '';
 
+	private static int $initDepth = 0;
+
 	public function __construct($arguments) {
 		$this->ownerView = $arguments['ownerView'];
 		$this->logger = \OC::$server->get(LoggerInterface::class);
@@ -135,8 +138,15 @@ private function init() {
 		if ($this->initialized) {
 			return;
 		}
+
 		$this->initialized = true;
+		self::$initDepth++;
+
 		try {
+			if (self::$initDepth > 10) {
+				throw new \Exception("Maximum share depth reached");
+			}
+
 			/** @var IRootFolder $rootFolder */
 			$rootFolder = \OC::$server->get(IRootFolder::class);
 			$this->ownerUserFolder = $rootFolder->getUserFolder($this->superShare->getShareOwner());
@@ -149,6 +159,9 @@ private function init() {
 				$this->cache = new FailedCache();
 				$this->rootPath = '';
 			} else {
+				if ($this->nonMaskedStorage instanceof Wrapper && $this->nonMaskedStorage->isWrapperOf($this)) {
+					throw new \Exception('recursive share detected');
+				}
 				$this->nonMaskedStorage = $ownerNode->getStorage();
 				$this->sourcePath = $ownerNode->getPath();
 				$this->rootPath = $ownerNode->getInternalPath();
@@ -177,6 +190,7 @@ private function init() {
 		if (!$this->nonMaskedStorage) {
 			$this->nonMaskedStorage = $this->storage;
 		}
+		self::$initDepth--;
 	}
 
 	/**

lib/private/Files/Storage/Wrapper/Wrapper.php

@@ -654,4 +654,15 @@ public function writeStream(string $path, $stream, int $size = null): int {
 	public function getDirectoryContent($directory): \Traversable {
 		return $this->getWrapperStorage()->getDirectoryContent($directory);
 	}
+
+	public function isWrapperOf(IStorage $storage) {
+		$wrapped = $this->getWrapperStorage();
+		if ($wrapped === $storage) {
+			return true;
+		}
+		if ($wrapped instanceof Wrapper) {
+			return $wrapped->isWrapperOf($storage);
+		}
+		return false;
+	}
 }