dissalow symlinks in local storages that point outside the datadir

lib/private/Files/Storage/Local.php

@@ -33,20 +33,31 @@
  */
 
 namespace OC\Files\Storage;
+
+use OCP\Files\ForbiddenException;
+
 /**
  * for local filestore, we only have to map the paths
  */
 class Local extends \OC\Files\Storage\Common {
 	protected $datadir;
 
+	protected $dataDirLength;
+
+	protected $allowSymlinks = false;
+
+	protected $realDataDir;
+
 	public function __construct($arguments) {
 		if (!isset($arguments['datadir']) || !is_string($arguments['datadir'])) {
 			throw new \InvalidArgumentException('No data directory set for local storage');
 		}
 		$this->datadir = $arguments['datadir'];
+		$this->realDataDir = rtrim(realpath($this->datadir), '/') . '/';
 		if (substr($this->datadir, -1) !== '/') {
 			$this->datadir .= '/';
 		}
+		$this->dataDirLength = strlen($this->realDataDir);
 	}
 
 	public function __destruct() {
@@ -337,10 +348,27 @@ class Local extends \OC\Files\Storage\Common {
 	 *
 	 * @param string $path
 	 * @return string
+	 * @throws ForbiddenException
 	 */
 	public function getSourcePath($path) {
 		$fullPath = $this->datadir . $path;
-		return $fullPath;
+		if ($this->allowSymlinks || $path === '') {
+			return $fullPath;
+		}
+		$pathToResolve = $fullPath;
+		$realPath = realpath($pathToResolve);
+		while ($realPath === false) { // for non existing files check the parent directory
+			$pathToResolve = dirname($pathToResolve);
+			$realPath = realpath($pathToResolve);
+		}
+		if ($realPath) {
+			$realPath = $realPath . '/';
+		}
+		if (substr($realPath, 0, $this->dataDirLength) === $this->realDataDir) {
+			return $fullPath;
+		} else {
+			throw new ForbiddenException("Following symlinks is not allowed ('$fullPath' -> '$realPath' not inside '{$this->realDataDir}')", false);
+		}
 	}
 
 	/**

lib/private/legacy/helper.php

@@ -206,7 +206,9 @@ class OC_Helper {
 
 			foreach ($files as $fileInfo) {
 				/** @var SplFileInfo $fileInfo */
-				if ($fileInfo->isDir()) {
+				if ($fileInfo->isLink()) {
+					unlink($fileInfo->getPathname());
+				} else if ($fileInfo->isDir()) {
 					rmdir($fileInfo->getRealPath());
 				} else {
 					unlink($fileInfo->getRealPath());

tests/lib/Files/Storage/LocalTest.php

@@ -84,5 +84,36 @@ class LocalTest extends Storage {
 	public function testInvalidArgumentsNoArray() {
 		new \OC\Files\Storage\Local(null);
 	}
+
+	/**
+	 * @expectedException \OCP\Files\ForbiddenException
+	 */
+	public function testDisallowSymlinksOutsideDatadir() {
+		$subDir1 = $this->tmpDir . 'sub1';
+		$subDir2 = $this->tmpDir . 'sub2';
+		$sym = $this->tmpDir . 'sub1/sym';
+		mkdir($subDir1);
+		mkdir($subDir2);
+
+		symlink($subDir2, $sym);
+
+		$storage = new \OC\Files\Storage\Local(['datadir' => $subDir1]);
+
+		$storage->file_put_contents('sym/foo', 'bar');
+	}
+
+	public function testDisallowSymlinksInsideDatadir() {
+		$subDir1 = $this->tmpDir . 'sub1';
+		$subDir2 = $this->tmpDir . 'sub1/sub2';
+		$sym = $this->tmpDir . 'sub1/sym';
+		mkdir($subDir1);
+		mkdir($subDir2);
+
+		symlink($subDir2, $sym);
+
+		$storage = new \OC\Files\Storage\Local(['datadir' => $subDir1]);
+
+		$storage->file_put_contents('sym/foo', 'bar');
+	}
 }