fix: harden webdav directory copies

chfs-ng/internal/api/server.go

@@ -1236,19 +1236,28 @@ func (f *webdavStorageFS) Copy(ctx context.Context, name, dest string, opts *web
 		return false, err
 	}
 	if info.IsDir() {
+		if opts != nil && opts.NoOverwrite {
+			if err := preflightCopyNoOverwrite(f.store, src, dst); err != nil {
+				return false, err
+			}
+		}
 		if err := f.store.MkdirAll(dst); err != nil {
 			return false, err
 		}
 		items, err := f.store.List(src)
 		if err != nil {
+			if !dstExists {
+				_ = f.store.Remove(dst)
+			}
 			return false, err
 		}
 		for _, item := range items {
-			created, err := f.Copy(ctx, path.Join(src, item.Name()), path.Join(dst, item.Name()), opts)
-			if err != nil {
+			if _, err := f.Copy(ctx, path.Join(src, item.Name()), path.Join(dst, item.Name()), opts); err != nil {
+				if !dstExists {
+					_ = f.store.Remove(dst)
+				}
 				return false, err
 			}
-			_ = created
 		}
 		return !dstExists, nil
 	}
@@ -1257,26 +1266,59 @@ func (f *webdavStorageFS) Copy(ctx context.Context, name, dest string, opts *web
 		return false, err
 	}
 	defer in.Close()
-	if err := copyFileToDestination(f.store, in, dst, dstExists); err != nil {
+	if err := copyFileToDestination(f.store, in, dst); err != nil {
 		return false, err
 	}
 	return !dstExists, nil
 }
 
-func copyFileToDestination(st storage.Storage, src io.Reader, dst string, dstExists bool) error {
-	tmp := fmt.Sprintf("%s.chfs-copy-%d", dst, time.Now().UnixNano())
-	for i := 0; i < 16; i++ {
-		if _, err := st.Stat(tmp); os.IsNotExist(err) {
-			break
-		} else if err != nil {
-			return err
-		}
-		tmp = fmt.Sprintf("%s.chfs-copy-%d-%d", dst, time.Now().UnixNano(), i)
+func preflightCopyNoOverwrite(st storage.Storage, src, dst string) error {
+	if _, err := st.Stat(dst); err == nil {
+		return webdav.NewHTTPError(http.StatusPreconditionFailed, fmt.Errorf("destination exists"))
+	} else if !os.IsNotExist(err) {
+		return err
 	}
-	out, err := createExclusive(st, tmp)
+	info, err := st.Stat(src)
 	if err != nil {
 		return err
 	}
+	if !info.IsDir() {
+		return nil
+	}
+	items, err := st.List(src)
+	if err != nil {
+		return err
+	}
+	for _, item := range items {
+		if err := preflightCopyNoOverwrite(st, path.Join(src, item.Name()), path.Join(dst, item.Name())); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func copyFileToDestination(st storage.Storage, src io.Reader, dst string) error {
+	var tmp string
+	var out *os.File
+	for i := 0; i < 16; i++ {
+		suffix := fmt.Sprintf("%d", time.Now().UnixNano())
+		if i > 0 {
+			suffix = fmt.Sprintf("%s-%d", suffix, i)
+		}
+		candidate := fmt.Sprintf("%s.chfs-copy-%s", dst, suffix)
+		var err error
+		out, err = createExclusive(st, candidate)
+		if err == nil {
+			tmp = candidate
+			break
+		}
+		if !os.IsExist(err) {
+			return err
+		}
+	}
+	if out == nil {
+		return fmt.Errorf("unable to allocate temporary copy path")
+	}
 	_, copyErr := io.Copy(out, src)
 	closeErr := out.Close()
 	if copyErr != nil {
@@ -1291,7 +1333,6 @@ func copyFileToDestination(st storage.Storage, src io.Reader, dst string, dstExi
 		_ = st.Remove(tmp)
 		return err
 	}
-	_ = dstExists
 	return nil
 }