feat: add native WebDAV submodule

This commit introduces a new, high-performance, and extensible WebDAV submodule, implemented natively without external dependencies.

The submodule includes:
- A core WebDAV handler that supports essential methods: PROPFIND, MKCOL, GET, PUT, DELETE, COPY, MOVE, LOCK, and UNLOCK.
- An extensible design using a `FileSystem` interface to decouple the protocol logic from the storage backend.
- Two `FileSystem` implementations:
  - `MemFS`: An in-memory, tree-based filesystem for testing and ephemeral storage. It correctly handles path segments like `.` and `..`.
  - `OSFS`: A secure, OS-based filesystem that interacts with the local disk. It includes robust path traversal protection that correctly handles symbolic links.
- A `LockSystem` interface with an in-memory implementation (`MemLock`) to support resource locking (DAV Class 2). It includes a graceful shutdown mechanism to prevent goroutine leaks.
- RFC 4918 compliance for core operations, including correct status codes for `COPY`/`MOVE` and preventing `DELETE` on non-empty collections.
- Comprehensive unit tests covering all major functionalities.
- A working example application demonstrating how to mount and use the submodule with a local directory.

The Touka framework's core has been updated to recognize WebDAV-specific HTTP methods.

This implementation addresses numerous points from detailed code reviews, including security vulnerabilities, memory leaks, RFC compliance issues, and path handling bugs.

webdav/memfs.go

@@ -36,7 +36,13 @@ func (fs *MemFS) findNode(path string) (*memNode, error) {
 	current := fs.root
 	parts := strings.Split(path, "/")
 	for _, part := range parts {
-		if part == "" {
+		if part == "" || part == "." {
+			continue
+		}
+		if part == ".." {
+			if current.parent != nil {
+				current = current.parent
+			}
 			continue
 		}
 		if current.children == nil {
@@ -105,6 +111,7 @@ func (fs *MemFS) OpenFile(ctx context.Context, name string, flag int, perm os.Fi
 
 	if flag&os.O_TRUNC != 0 {
 		node.data = nil
+		node.size = 0
 	}
 
 	return &memFile{
@@ -234,14 +241,21 @@ func (f *memFile) Write(p []byte) (n int, err error) {
 func (f *memFile) Seek(offset int64, whence int) (int64, error) {
 	f.fs.mu.Lock()
 	defer f.fs.mu.Unlock()
+	var newOffset int64
 	switch whence {
-	case 0:
+	case io.SeekStart:
-		f.offset = offset
+		newOffset = offset
-	case 1:
+	case io.SeekCurrent:
-		f.offset += offset
+		newOffset = f.offset + offset
-	case 2:
+	case io.SeekEnd:
-		f.offset = int64(len(f.node.data)) + offset
+		newOffset = f.node.size + offset
+	default:
+		return 0, os.ErrInvalid
 	}
+	if newOffset < 0 {
+		return 0, os.ErrInvalid
+	}
+	f.offset = newOffset
 	return f.offset, nil
 }
 

webdav/memlock.go

@@ -17,6 +17,7 @@ import (
 type MemLock struct {
 	mu    sync.RWMutex
 	locks map[string]*lock
+	stop  chan struct{}
 }
 
 type lock struct {
@@ -28,8 +29,35 @@ type lock struct {
 
 // NewMemLock creates a new in-memory lock system.
 func NewMemLock() *MemLock {
-	return &MemLock{
+	l := &MemLock{
 		locks: make(map[string]*lock),
+		stop:  make(chan struct{}),
+	}
+	go l.cleanup()
+	return l
+}
+
+// Close stops the cleanup goroutine.
+func (l *MemLock) Close() {
+	close(l.stop)
+}
+
+func (l *MemLock) cleanup() {
+	ticker := time.NewTicker(1 * time.Minute)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			l.mu.Lock()
+			for token, lock := range l.locks {
+				if time.Now().After(lock.expires) {
+					delete(l.locks, token)
+				}
+			}
+			l.mu.Unlock()
+		case <-l.stop:
+			return
+		}
 	}
 }
 
@@ -39,7 +67,9 @@ func (l *MemLock) Create(ctx context.Context, path string, info LockInfo) (strin
 	defer l.mu.Unlock()
 
 	token := make([]byte, 16)
-	rand.Read(token)
+	if _, err := rand.Read(token); err != nil {
+		return "", err
+	}
 	tokenStr := hex.EncodeToString(token)
 
 	l.locks[tokenStr] = &lock{

webdav/osfs.go

@@ -26,10 +26,37 @@ func NewOSFS(rootDir string) (*OSFS, error) {
 }
 
 func (fs *OSFS) resolve(name string) (string, error) {
+	if filepath.IsAbs(name) || strings.Contains(name, "..") {
+		return "", os.ErrPermission
+	}
+
 	path := filepath.Join(fs.RootDir, name)
+
+	// Evaluate symlinks, but only if the path exists.
+	if _, err := os.Lstat(path); err == nil {
+		path, err = filepath.EvalSymlinks(path)
+		if err != nil {
+			return "", err
+		}
+	} else if !os.IsNotExist(err) {
+		return "", err
+		// For non-existent paths (like for PUT or MKCOL), we can't EvalSymlinks the full path.
+		// Instead, we resolve the parent and ensure it's within the root.
+	} else {
+		parentDir := filepath.Dir(path)
+		if _, err := os.Stat(parentDir); err == nil {
+			parentDir, err = filepath.EvalSymlinks(parentDir)
+			if err != nil {
+				return "", err
+			}
+			path = filepath.Join(parentDir, filepath.Base(path))
+		}
+	}
+
 	if !strings.HasPrefix(path, fs.RootDir) {
 		return "", os.ErrPermission
 	}
+
 	return path, nil
 }
 

webdav/webdav.go

@@ -284,7 +284,39 @@ func (h *Handler) handleGetHead(c *touka.Context) {
 
 func (h *Handler) handleDelete(c *touka.Context) {
 	path, _ := c.Get("webdav_path")
-	if err := h.FileSystem.RemoveAll(c.Context(), path.(string)); err != nil {
+	pathStr := path.(string)
+
+	info, err := h.FileSystem.Stat(c.Context(), pathStr)
+	if err != nil {
+		if os.IsNotExist(err) {
+			c.Status(http.StatusNotFound)
+		} else {
+			c.Status(http.StatusInternalServerError)
+		}
+		return
+	}
+
+	if info.IsDir() {
+		file, err := h.FileSystem.OpenFile(c.Context(), pathStr, os.O_RDONLY, 0)
+		if err != nil {
+			c.Status(http.StatusInternalServerError)
+			return
+		}
+		defer file.Close()
+
+		// Check if the directory has any children. Readdir(1) is enough.
+		children, err := file.Readdir(1)
+		if err != nil && err != io.EOF {
+			c.Status(http.StatusInternalServerError)
+			return
+		}
+		if len(children) > 0 {
+			c.Status(http.StatusConflict) // 409 Conflict for non-empty collection
+			return
+		}
+	}
+
+	if err := h.FileSystem.RemoveAll(c.Context(), pathStr); err != nil {
 		if os.IsNotExist(err) {
 			c.Status(http.StatusNotFound)
 		} else {
@@ -347,19 +379,25 @@ func (h *Handler) handleCopy(c *touka.Context) {
         overwrite = "T" // Default is to overwrite
     }
 
-    if overwrite == "F" {
+    // Check for existence before the operation to determine status code later.
-        if _, err := h.FileSystem.Stat(c.Context(), destPath); err == nil {
+	_, err = h.FileSystem.Stat(c.Context(), destPath)
+	existed := err == nil
+
+    if overwrite == "F" && existed {
         c.Status(http.StatusPreconditionFailed)
         return
     }
-    }
 
     if err := h.copy(c.Context(), srcPath.(string), destPath); err != nil {
         c.Status(http.StatusInternalServerError)
         return
     }
 
+	if existed {
+		c.Status(http.StatusNoContent)
+	} else {
 		c.Status(http.StatusCreated)
+	}
 }
 
 func (h *Handler) handleMove(c *touka.Context) {
@@ -382,19 +420,25 @@ func (h *Handler) handleMove(c *touka.Context) {
         overwrite = "T" // Default is to overwrite
     }
 
-    if overwrite == "F" {
+    // Check for existence before the operation to determine status code later.
-        if _, err := h.FileSystem.Stat(c.Context(), destPath); err == nil {
+	_, err = h.FileSystem.Stat(c.Context(), destPath)
+	existed := err == nil
+
+    if overwrite == "F" && existed {
         c.Status(http.StatusPreconditionFailed)
         return
     }
-    }
 
     if err := h.FileSystem.Rename(c.Context(), srcPath.(string), destPath); err != nil {
         c.Status(http.StatusInternalServerError)
         return
     }
 
+	if existed {
+		c.Status(http.StatusNoContent)
+	} else {
 		c.Status(http.StatusCreated)
+	}
 }
 
 func (h *Handler) copy(ctx context.Context, src, dest string) error {
@@ -585,11 +629,11 @@ func (h *Handler) handleProppatch(c *touka.Context) {
 	c.Status(http.StatusNotImplemented)
 }
 
-func (h *Handler) stripPrefix(path string) string {
+func (h *Handler) stripPrefix(p string) string {
 	if h.Prefix == "/" {
-		return path
+		return p
 	}
-	return "/" + strings.TrimPrefix(path, h.Prefix)
+	return strings.TrimPrefix(p, h.Prefix)
 }
 
 func (h *Handler) handleLock(c *touka.Context) {
@@ -599,7 +643,15 @@ func (h *Handler) handleLock(c *touka.Context) {
 	}
 
 	path, _ := c.Get("webdav_path")
-	token := c.GetReqHeader("If")
+	tokenHeader := c.GetReqHeader("If")
+	var token string
+	if tokenHeader != "" {
+		// Basic parsing for <opaquelocktoken:c2134f...>
+		if strings.HasPrefix(tokenHeader, "(<") && strings.HasSuffix(tokenHeader, ">)") {
+			token = strings.TrimPrefix(tokenHeader, "(<")
+			token = strings.TrimSuffix(token, ">)")
+		}
+	}
 
 	// Refresh lock
 	if token != "" {
@@ -666,7 +718,7 @@ func parseTimeout(timeoutStr string) (time.Duration, error) {
 			return seconds, nil
 		}
 	}
-	return 0, nil
+	return 0, os.ErrInvalid
 }
 
 func (h *Handler) handleUnlock(c *touka.Context) {
@@ -675,12 +727,16 @@ func (h *Handler) handleUnlock(c *touka.Context) {
 		return
 	}
 
-	token := c.GetReqHeader("Lock-Token")
+	tokenHeader := c.GetReqHeader("Lock-Token")
-	if token == "" {
+	if tokenHeader == "" {
 		c.Status(http.StatusBadRequest)
 		return
 	}
 
+	// Basic parsing for <urn:uuid:f81d4fae...>
+	token := strings.TrimPrefix(tokenHeader, "<")
+	token = strings.TrimSuffix(token, ">")
+
 	if err := h.LockSystem.Unlock(c.Context(), token); err != nil {
 		c.Status(http.StatusConflict)
 		return