fix: Allow read-only filename validation to allow reading files

Needed to read files with the "Windows compatibility" feature.

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

apps/dav/lib/Connector/Sabre/Directory.php

@@ -173,7 +173,7 @@ class Directory extends \OCA\DAV\Connector\Sabre\Node implements \Sabre\DAV\ICol
 		$path = $this->path . '/' . $name;
 		if (is_null($info)) {
 			try {
-				$this->fileView->verifyPath($this->path, $name);
+				$this->fileView->verifyPath($this->path, $name, true);
 				$info = $this->fileView->getFileInfo($path);
 			} catch (\OCP\Files\StorageNotAvailableException $e) {
 				throw new \Sabre\DAV\Exception\ServiceUnavailable($e->getMessage(), 0, $e);

lib/private/Files/View.php

@@ -1826,15 +1826,26 @@ class View {
 	/**
 	 * @param string $path
 	 * @param string $fileName
+	 * @param bool $readonly Check only if the path is allowed for read-only access
 	 * @throws InvalidPathException
 	 */
-	public function verifyPath($path, $fileName): void {
+	public function verifyPath($path, $fileName, $readonly = false): void {
 		// All of the view's functions disallow '..' in the path so we can short cut if the path is invalid
 		if (!Filesystem::isValidPath($path ?: '/')) {
 			$l = \OCP\Util::getL10N('lib');
 			throw new InvalidPathException($l->t('Path contains invalid segments'));
 		}
 
+		// Short cut for read-only validation
+		if ($readonly) {
+			$validator = \OCP\Server::get(FilenameValidator::class);
+			if ($validator->isForbidden($fileName)) {
+				$l = \OCP\Util::getL10N('lib');
+				throw new InvalidPathException($l->t('Filename is a reserved word'));
+			}
+			return;
+		}
+
 		try {
 			/** @type \OCP\Files\Storage $storage */
 			[$storage, $internalPath] = $this->resolvePath($path);