webdav: refuse MKCOL and PUT under a missing folder with 409 (#12122)

* webdav: refuse MKCOL and PUT under a missing folder with 409

RFC 4918 9.3 and 9.7.1 say a MKCOL or PUT whose parent collection does
not exist must fail with 409 Conflict. The filer creates missing parents,
so both succeeded and made the intermediate folders. Check the parent in
Mkdir and in OpenFile with O_CREATE and return os.ErrNotExist, which
x/net/webdav turns into 409.

* webdav: check the PUT parent before an overwrite deletes the target

OpenFile deleted an existing destination before the new parent lookup,
so a PUT whose parent check failed left the old file gone.

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* webdav: report a missing rename source as not-exist

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* webdav: refuse MOVE to a missing destination folder

AtomicRenameEntry grows any missing parents itself, so a MOVE to
/missing/file created /missing; check the destination parent first.

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* webdav: answer 409 for COPY and MOVE under a missing collection

The webdav handler reports a failed directory Mkdir or Rename as 403,
so the destination parent is checked at the request layer instead.

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* webdav: defer foreign-host MOVE and COPY destinations to the 502 handler

* webdav: only check the destination parent for absolute paths

* webdav: cover foreign-host and relative MOVE destinations in the guard test

---------

Co-authored-by: user.email <chrislusf@users.noreply.github.com>
Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

weed/server/webdav_server.go

@@ -98,6 +98,12 @@ type copyMoveGuardHandler struct {
 
 func (h copyMoveGuardHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if r.Method == "MOVE" || r.Method == "COPY" {
+		// a foreign-host Destination is another server's problem: the webdav
+		// handler answers 502, so the local checks below do not apply
+		if u, err := url.Parse(r.Header.Get("Destination")); err == nil && u.Host != "" && u.Host != r.Host {
+			h.next.ServeHTTP(w, r)
+			return
+		}
 		if u, err := url.Parse(r.Header.Get("Destination")); err == nil {
 			src := strings.Trim(path.Clean(r.URL.Path), "/")
 			dst := strings.Trim(path.Clean(u.Path), "/")
@@ -129,6 +135,25 @@ func (h copyMoveGuardHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)
 				r.Header.Set("Destination", u.String())
 			}
 		}
+		// the destination's parent collection must exist; Mkdir and Rename
+		// errors surface as 403 below, not the 409 a missing parent requires
+		if u, err := url.Parse(r.Header.Get("Destination")); err == nil {
+			if dst := path.Clean(u.Path); strings.HasPrefix(dst, "/") && dst != "/" {
+				if parent := path.Dir(dst); parent != "/" {
+					if pfi, err := h.fs.Stat(r.Context(), parent); err != nil {
+						if os.IsNotExist(err) {
+							w.WriteHeader(http.StatusConflict)
+						} else {
+							w.WriteHeader(http.StatusInternalServerError)
+						}
+						return
+					} else if !pfi.IsDir() {
+						w.WriteHeader(http.StatusConflict)
+						return
+					}
+				}
+			}
+		}
 	}
 	h.next.ServeHTTP(w, r)
 }
@@ -251,8 +276,12 @@ func (fs *WebDavFileSystem) Mkdir(ctx context.Context, fullDirPath string, perm
 		return err
 	}
 
+	dir, name := util.NormalizePath(fullDirPath).DirAndName()
+	if err := fs.checkParentDir(ctx, dir); err != nil {
+		return err
+	}
+
 	return fs.WithFilerClient(false, func(client filer_pb.SeaweedFilerClient) error {
-		dir, name := util.NormalizePath(fullDirPath).DirAndName()
 		request := &filer_pb.CreateEntryRequest{
 			Directory: dir,
 			Entry: &filer_pb.Entry{
@@ -278,6 +307,23 @@ func (fs *WebDavFileSystem) Mkdir(ctx context.Context, fullDirPath string, perm
 	})
 }
 
+// checkParentDir returns os.ErrNotExist, which x/net/webdav answers with 409
+// Conflict, when dir is missing or is not a folder: RFC 4918 9.3 and 9.7.1
+// forbid creating the intermediate collections of a MKCOL or PUT.
+func (fs *WebDavFileSystem) checkParentDir(ctx context.Context, dir string) error {
+	if dir == "/" {
+		return nil
+	}
+	fi, err := fs.stat(ctx, dir)
+	if err != nil {
+		return err
+	}
+	if !fi.IsDir() {
+		return os.ErrNotExist
+	}
+	return nil
+}
+
 func (fs *WebDavFileSystem) OpenFile(ctx context.Context, fullFilePath string, flag int, perm os.FileMode) (webdav.File, error) {
 	glog.V(2).Infof("WebDavFileSystem.OpenFile %v %x", fullFilePath, flag)
 
@@ -291,6 +337,10 @@ func (fs *WebDavFileSystem) OpenFile(ctx context.Context, fullFilePath string, f
 		if strings.HasSuffix(fullFilePath, "/") {
 			return nil, os.ErrInvalid
 		}
+		dir, name := util.FullPath(fullFilePath).DirAndName()
+		if err := fs.checkParentDir(ctx, dir); err != nil {
+			return nil, err
+		}
 		fi, err := fs.stat(ctx, fullFilePath)
 		if err == nil {
 			if flag&os.O_EXCL != 0 || fi.IsDir() {
@@ -301,7 +351,6 @@ func (fs *WebDavFileSystem) OpenFile(ctx context.Context, fullFilePath string, f
 			return nil, err
 		}
 
-		dir, name := util.FullPath(fullFilePath).DirAndName()
 		err = fs.WithFilerClient(false, func(client filer_pb.SeaweedFilerClient) error {
 			if err := filer_pb.CreateEntry(context.Background(), client, &filer_pb.CreateEntryRequest{
 				Directory: dir,
@@ -392,7 +441,7 @@ func (fs *WebDavFileSystem) Rename(ctx context.Context, oldName, newName string)
 	}
 
 	if _, err = fs.stat(ctx, oldName); err != nil {
-		return os.ErrExist
+		return err
 	}
 	oldName = string(util.NormalizePath(oldName))
 	newName = string(util.NormalizePath(newName))
@@ -411,6 +460,10 @@ func (fs *WebDavFileSystem) Rename(ctx context.Context, oldName, newName string)
 	oldDir, oldBaseName := util.FullPath(oldName).DirAndName()
 	newDir, newBaseName := util.FullPath(newName).DirAndName()
 
+	if err := fs.checkParentDir(ctx, newDir); err != nil {
+		return err
+	}
+
 	return fs.WithFilerClient(false, func(client filer_pb.SeaweedFilerClient) error {
 
 		request := &filer_pb.AtomicRenameEntryRequest{