Opendir return an error status when not found

The initial Opendir packet is supposed to repond with an error status if
the directory wasn't found. It was just returning a handle without
checking, now it does a Stat on the path and only returns the handle if
the Stat is successful and it indicates it is a directory, otherwise it
returns an error.

request-server.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding"
 	"io"
+	"os"
 	"path"
 	"path/filepath"
 	"strconv"
@@ -172,9 +173,19 @@ func (rs *RequestServer) packetWorker(
 		case *sshFxpRealpathPacket:
 			rpkt = cleanPacketPath(pkt)
 		case *sshFxpOpendirPacket:
+			request := requestFromPacket(ctx, pkt)
+			rpkt = request.call(rs.Handlers, pkt)
+			request.close()
+			if stat, ok := rpkt.(*sshFxpStatResponse); ok {
+				if stat.info.IsDir() {
 					request := requestFromPacket(ctx, pkt)
 					handle := rs.nextRequest(request)
 					rpkt = sshFxpHandlePacket{pkt.id(), handle}
+				} else {
+					rpkt = statusFromError(pkt, &os.PathError{
+						Path: request.Filepath, Err: syscall.ENOTDIR})
+				}
+			}
 		case *sshFxpOpenPacket:
 			request := requestFromPacket(ctx, pkt)
 			handle := rs.nextRequest(request)

request-server_test.go

@@ -355,6 +355,11 @@ func TestRequestReaddir(t *testing.T) {
 		_, err := putTestFile(p.cli, fname, fname)
 		assert.Nil(t, err)
 	}
+	_, err := p.cli.ReadDir("/foo_01")
+	assert.Equal(t, &StatusError{Code: ssh_FX_FAILURE,
+		msg: " /foo_01: not a directory"}, err)
+	_, err = p.cli.ReadDir("/does_not_exist")
+	assert.Equal(t, os.ErrNotExist, err)
 	di, err := p.cli.ReadDir("/")
 	assert.Nil(t, err)
 	assert.Len(t, di, 100)

request.go

@@ -338,8 +338,10 @@ func requestMethod(p requestPacket) (method string) {
 		method = "Put"
 	case *sshFxpReaddirPacket:
 		method = "List"
-	case *sshFxpOpenPacket, *sshFxpOpendirPacket:
+	case *sshFxpOpenPacket:
 		method = "Open"
+	case *sshFxpOpendirPacket:
+		method = "Stat"
 	case *sshFxpSetstatPacket, *sshFxpFsetstatPacket:
 		method = "Setstat"
 	case *sshFxpRenamePacket:

server.go

@@ -240,6 +240,12 @@ func handlePacket(s *Server, p interface{}) error {
 			}},
 		})
 	case *sshFxpOpendirPacket:
+		if stat, err := os.Stat(p.Path); err != nil {
+			return s.sendError(p, err)
+		} else if !stat.IsDir() {
+			return s.sendError(p, &os.PathError{
+				Path: p.Path, Err: syscall.ENOTDIR})
+		}
 		return sshFxpOpenPacket{
 			ID:     p.ID,
 			Path:   p.Path,