harden storage paths and trash handling

chfs-ng/internal/storage/storage.go

@@ -3,10 +3,13 @@ package storage
 import (
 	"errors"
 	"fmt"
+	"io"
 	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
+	"syscall"
+	"time"
 
 	"github.com/Bios-Marcel/wastebasket"
 )
@@ -33,6 +36,10 @@ func (s Local) real(path string) (string, error) {
 	if err != nil {
 		return "", err
 	}
+	root, err = filepath.EvalSymlinks(root)
+	if err != nil {
+		return "", err
+	}
 	p := strings.TrimPrefix(filepath.Clean("/"+path), string(filepath.Separator))
 	full := filepath.Join(root, p)
 	rel, err := filepath.Rel(root, full)
@@ -42,6 +49,25 @@ func (s Local) real(path string) (string, error) {
 	if rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
 		return "", errors.New("path escapes storage root")
 	}
+	check := full
+	for {
+		if _, err = os.Lstat(check); !os.IsNotExist(err) {
+			break
+		}
+		next := filepath.Dir(check)
+		if next == check {
+			break
+		}
+		check = next
+	}
+	resolved, err := filepath.EvalSymlinks(check)
+	if err != nil {
+		return "", err
+	}
+	resolvedRel, err := filepath.Rel(root, resolved)
+	if err != nil || resolvedRel == ".." || strings.HasPrefix(resolvedRel, ".."+string(filepath.Separator)) {
+		return "", errors.New("path escapes storage root")
+	}
 	return full, nil
 }
 func (s Local) Stat(path string) (os.FileInfo, error) {
@@ -89,19 +115,121 @@ func (s Local) MoveToTrash(path, trashRoot string) error {
 	if e != nil {
 		return e
 	}
+	root, e := filepath.Abs(s.Root)
+	if e != nil {
+		return e
+	}
+	rel, e := filepath.Rel(root, p)
+	if e != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
+		return errors.New("path escapes storage root")
+	}
 	if e = os.MkdirAll(trashRoot, 0755); e != nil {
 		return e
 	}
-	name := filepath.Base(p)
-	target := filepath.Join(trashRoot, name)
+	// Preserve the original relative path under the CHFS trash root so
+	// identically named files from different directories cannot collide.
+	target := filepath.Join(trashRoot, rel)
+	if e = os.MkdirAll(filepath.Dir(target), 0755); e != nil {
+		return e
+	}
 	for i := 1; ; i++ {
 		if _, e = os.Lstat(target); os.IsNotExist(e) {
 			break
 		}
-		target = filepath.Join(trashRoot, fmt.Sprintf("%s.%d", name, i))
+		target = filepath.Join(filepath.Dir(target), fmt.Sprintf("%s.%d", filepath.Base(p), i))
 	}
-	return os.Rename(p, target)
+	if e = movePath(p, target); e != nil {
+		return e
+	}
+	return cleanupTrash(trashRoot, 30*24*time.Hour)
 }
+
+func cleanupTrash(root string, maxAge time.Duration) error {
+	now := time.Now()
+	return filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if path == root || d.IsDir() {
+			return nil
+		}
+		info, err := d.Info()
+		if err != nil {
+			return err
+		}
+		if now.Sub(info.ModTime()) > maxAge {
+			return os.Remove(path)
+		}
+		return nil
+	})
+}
+
+func movePath(src, dst string) error {
+	if err := os.Rename(src, dst); err == nil {
+		return nil
+	} else if !errors.Is(err, syscall.EXDEV) {
+		return err
+	}
+	if _, err := os.Lstat(dst); err == nil {
+		return fmt.Errorf("destination already exists: %s", dst)
+	} else if !os.IsNotExist(err) {
+		return err
+	}
+	if err := copyPath(src, dst); err != nil {
+		return err
+	}
+	return os.RemoveAll(src)
+}
+
+func copyPath(src, dst string) error {
+	info, err := os.Lstat(src)
+	if err != nil {
+		return err
+	}
+	if info.Mode()&os.ModeSymlink != 0 {
+		target, err := os.Readlink(src)
+		if err != nil {
+			return err
+		}
+		return os.Symlink(target, dst)
+	}
+	if info.IsDir() {
+		if err := os.MkdirAll(dst, info.Mode().Perm()); err != nil {
+			return err
+		}
+		entries, err := os.ReadDir(src)
+		if err != nil {
+			return err
+		}
+		for _, entry := range entries {
+			if err := copyPath(filepath.Join(src, entry.Name()), filepath.Join(dst, entry.Name())); err != nil {
+				return err
+			}
+		}
+		return os.Chtimes(dst, info.ModTime(), info.ModTime())
+	}
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+	out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_EXCL, info.Mode().Perm())
+	if err != nil {
+		return err
+	}
+	_, copyErr := io.Copy(out, in)
+	closeErr := out.Close()
+	if copyErr != nil {
+		_ = os.Remove(dst)
+		return copyErr
+	}
+	if closeErr != nil {
+		_ = os.Remove(dst)
+		return closeErr
+	}
+	return os.Chtimes(dst, info.ModTime(), info.ModTime())
+}
+
 func (s Local) Rename(a, b string) error {
 	pa, e := s.real(a)
 	if e != nil {
@@ -111,7 +239,7 @@ func (s Local) Rename(a, b string) error {
 	if e != nil {
 		return e
 	}
-	return os.Rename(pa, pb)
+	return movePath(pa, pb)
 }
 func (s Local) MkdirAll(path string) error {
 	p, e := s.real(path)