fix(sftp): fix OpenSSH key auth and password fallback after asyncssh migration

src/portkeydrop/protocols.py

@@ -444,12 +444,10 @@ def connect(self) -> None:
                         f"SFTP connection failed: key file not found: {self._info.key_path}"
                     )
                 # asyncssh handles OpenSSH + PPK v2/v3 natively
-                passphrase = self._info.password if self._info.password else None
                 connect_kwargs["client_keys"] = [key_path]
-                connect_kwargs["passphrase"] = passphrase
                 connect_kwargs["agent_path"] = None  # disable agent
                 auth_methods = [f"key-file:{self._info.key_path}"]
-            elif self._info.password:
+            if self._info.password:
                 connect_kwargs["password"] = self._info.password
                 auth_methods.append("password")
 
@@ -488,7 +486,14 @@ async def _connect():
                 self._info.host,
                 auth_methods,
             )
-            if self._info.key_path:
+            if self._info.key_path and self._info.password:
+                message = (
+                    f"Authentication failed with key file '{self._info.key_path}' "
+                    "and password fallback. "
+                    "Check key permissions, server authorized_keys, and verify "
+                    "username/password."
+                )
+            elif self._info.key_path:
                 message = (
                     f"Authentication failed with key file '{self._info.key_path}'. "
                     "Check key permissions, passphrase, and server authorized_keys."

tests/test_sftp_client.py

@@ -79,6 +79,57 @@ def test_connect_with_key_file(self, mock_connect: AsyncMock, _mock_exists: Magi
         call_kwargs = mock_connect.call_args[1]
         assert call_kwargs["client_keys"] == ["/path/to/key"]
         assert call_kwargs["agent_path"] is None
+        assert "passphrase" not in call_kwargs
+        assert "password" not in call_kwargs
+
+    @patch("os.path.exists", return_value=True)
+    @patch("asyncssh.connect", new_callable=AsyncMock)
+    def test_connect_with_key_and_password_fallback(
+        self, mock_connect: AsyncMock, _mock_exists: MagicMock
+    ) -> None:
+        """When both key_path and password are set, password is passed for
+        fallback auth and passphrase is omitted."""
+        info = ConnectionInfo(
+            protocol=Protocol.SFTP,
+            host="example.com",
+            username="user",
+            password="secret",
+            key_path="/path/to/key",
+        )
+        mock_conn, mock_sftp = _make_mock_conn()
+        mock_connect.return_value = mock_conn
+
+        client = SFTPClient(info)
+        client.connect()
+
+        call_kwargs = mock_connect.call_args[1]
+        assert call_kwargs["client_keys"] == ["/path/to/key"]
+        assert call_kwargs["password"] == "secret"
+        assert "passphrase" not in call_kwargs
+        assert client._connected is True
+
+    @patch("os.path.exists", return_value=True)
+    @patch("asyncssh.connect", new_callable=AsyncMock)
+    def test_connect_with_key_and_password_logs_both_methods(
+        self, mock_connect: AsyncMock, _mock_exists: MagicMock, caplog: pytest.LogCaptureFixture
+    ) -> None:
+        info = ConnectionInfo(
+            protocol=Protocol.SFTP,
+            host="example.com",
+            username="user",
+            password="secret",
+            key_path="/path/to/key",
+        )
+        mock_conn, mock_sftp = _make_mock_conn()
+        mock_connect.return_value = mock_conn
+
+        caplog.set_level(logging.DEBUG, logger="portkeydrop.protocols")
+
+        client = SFTPClient(info)
+        client.connect()
+
+        assert "key-file:/path/to/key" in caplog.text
+        assert "password" in caplog.text
 
     @patch("asyncssh.connect", new_callable=AsyncMock)
     def test_connect_agent_only(self, mock_connect: AsyncMock) -> None:
@@ -163,6 +214,27 @@ def test_auth_failure_message_for_agent_and_password(self, mock_connect: AsyncMo
         ):
             client.connect()
 
+    @patch("os.path.exists", return_value=True)
+    @patch("asyncssh.connect", new_callable=AsyncMock)
+    def test_auth_failure_message_for_key_and_password(
+        self, mock_connect: AsyncMock, _mock_exists: MagicMock
+    ) -> None:
+        import asyncssh
+
+        mock_connect.side_effect = asyncssh.PermissionDenied("denied")
+
+        info = ConnectionInfo(
+            protocol=Protocol.SFTP,
+            host="example.com",
+            username="user",
+            password="secret",
+            key_path="/path/to/key",
+        )
+        client = SFTPClient(info)
+
+        with pytest.raises(ConnectionError, match="and password fallback"):
+            client.connect()
+
     @patch("asyncssh.connect", new_callable=AsyncMock)
     def test_auth_failure_message_for_agent_only(self, mock_connect: AsyncMock) -> None:
         import asyncssh