Added Modbus over TCP dissector

1 files changed, 72 insertions, 0 deletions

diff --git a/src/lib/protocols/modbus.c b/src/lib/protocols/modbus.c
new file mode 100644
index 000000000..2a6dd2a49
--- /dev/null
+++ b/src/lib/protocols/modbus.c
@@ -0,0 +1,72 @@
+
+/*
+ * modbus.c
+ *
+ * Copyright (C) 2018 - ntop.org
+ *
+ * This file is part of nDPI, an open source deep packet inspection
+ * library based on the OpenDPI and PACE technology by ipoque GmbH
+ *
+ * nDPI is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * nDPI is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with nDPI.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+
+#include "ndpi_protocol_ids.h"
+#include "ndpi_api.h"
+
+#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_MODBUS
+
+void ndpi_search_modbus_tcp(struct ndpi_detection_module_struct *ndpi_struct,
+                            struct ndpi_flow_struct *flow) {
+  struct ndpi_packet_struct *packet = &flow->packet;
+  NDPI_LOG_DBG(ndpi_struct, "search Modbus\n");
+  u_int16_t modbus_port = htons(502); // port used by modbus
+
+  /* Check connection over TCP */
+    
+  if(packet->tcp) {
+    /* The payload of Modbus-TCP segment must be at least 8 bytes (7 bytes of header application 
+       packet plus 1 byte of minimum payload of application packet)
+    */
+    if((packet->payload_packet_len >= 8) 
+       &&((packet->tcp->dest == modbus_port) || (packet->tcp->source == modbus_port))) {
+      // Modbus uses the port 502		
+      u_int16_t modbus_len = htons(*((u_int16_t*)&packet->payload[4]));
+
+      // the fourth parameter of the payload is the length of the segment            
+      if((modbus_len-1) == (packet->payload_packet_len - 7 /* ModbusTCP header len */)) {
+	NDPI_LOG_INFO(ndpi_struct, "found MODBUS\n");
+	ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MODBUS, NDPI_PROTOCOL_UNKNOWN);
+	return;
+      }
+    }
+  }
+  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+   
+}
+
+
+
+void init_modbus_dissector(struct ndpi_detection_module_struct *ndpi_struct,
+                           u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask) {
+	
+  ndpi_set_bitmask_protocol_detection("Modbus", ndpi_struct, detection_bitmask, *id,
+				      NDPI_PROTOCOL_MODBUS,
+				      ndpi_search_modbus_tcp,
+				      NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
+				      SAVE_DETECTION_BITMASK_AS_UNKNOWN,
+				      ADD_TO_DETECTION_BITMASK);
+  *id += 1;
+}