Initial Backupper Unraid plugin

internal/platform/paths.go

@@ -0,0 +1,61 @@
+package platform
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func ValidateRestoreTarget(target, restoreRoot string, inPlace, confirmed bool) (string, error) {
+	if !filepath.IsAbs(target) {
+		return "", errors.New("validation: restore target must be absolute")
+	}
+	clean := filepath.Clean(target)
+	if clean == "/" || clean == "/boot" || clean == "/etc" || clean == "/usr" || clean == "/var" {
+		return "", errors.New("validation: protected system restore target")
+	}
+	if !inPlace {
+		root := filepath.Clean(restoreRoot)
+		if clean != root && !strings.HasPrefix(clean, root+string(os.PathSeparator)) {
+			return "", errors.New("validation: staging restore must remain below restoreRoot")
+		}
+		if err := rejectSymlinks(root, clean); err != nil {
+			return "", err
+		}
+	} else if !confirmed {
+		return "", errors.New("validation: in-place restore requires explicit confirmation")
+	}
+	if inPlace {
+		anchor := string(os.PathSeparator) + strings.Split(strings.TrimPrefix(clean, string(os.PathSeparator)), string(os.PathSeparator))[0]
+		if err := rejectSymlinks(anchor, clean); err != nil {
+			return "", err
+		}
+	}
+	return clean, nil
+}
+
+func rejectSymlinks(root, target string) error {
+	relative, err := filepath.Rel(root, target)
+	if err != nil {
+		return err
+	}
+	current := root
+	for _, component := range strings.Split(relative, string(os.PathSeparator)) {
+		if component == "." || component == "" {
+			continue
+		}
+		current = filepath.Join(current, component)
+		info, err := os.Lstat(current)
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
+		if err != nil {
+			return err
+		}
+		if info.Mode()&os.ModeSymlink != 0 {
+			return errors.New("validation: restore target traverses a symlink")
+		}
+	}
+	return nil
+}