fix: guard short frames and validate mbap pid in TLS framer

pymodbus/framer/tls.py

@@ -20,9 +20,11 @@ class FramerTLS(FramerBase):
 
     def decode(self, data: bytes) -> tuple[int, int, int, bytes]:
         """Decode MDAP+payload."""
+        if (data_len := len(data)) < self.MIN_SIZE:
+            return data_len, 0, 0, self.EMPTY
         tid = int.from_bytes(data[0:2], 'big')
         dev_id = int(data[6])
-        return len(data), dev_id, tid, data[7:]
+        return data_len, dev_id, tid, data[7:]
 
     def encode(self, payload: bytes, device_id: int, tid: int) -> bytes:
         """Encode MDAP+payload."""

test/framer/test_framer.py

@@ -489,6 +489,16 @@ def test_invalid_protocol_id_for_framer_socket(self):
         assert tid == 0
         assert pdu == framer.EMPTY
 
+    def test_short_packet_for_framer_tls(self):
+        """Test that FramerTLS handles short packets without raising."""
+        framer = FramerTLS(DecodePDU(False))
+        data = b"\x00\x01\x00\x00\x00"
+        data_len, dev_id, tid, pdu = framer.decode(data)
+        assert data_len == len(data)
+        assert dev_id == 0
+        assert tid == 0
+        assert pdu == framer.EMPTY
+
     @pytest.mark.parametrize(("entry"), [FramerType.ASCII])
     @pytest.mark.parametrize(("is_server"), [False, True])
     @pytest.mark.parametrize(("msg"), [