Add NoMachine NX protocol dissector (#2234)

* Add NoMachine protocol dissector

* Fix detection on big endian architectures

* Make NoMachine over UDP check more strict

* Small fixes

1 files changed, 82 insertions, 0 deletions

diff --git a/src/lib/protocols/nomachine.c b/src/lib/protocols/nomachine.c
new file mode 100644
index 000000000..33cf71dc9
--- /dev/null
+++ b/src/lib/protocols/nomachine.c
@@ -0,0 +1,82 @@
+/*
+ * nomachine.c
+ *
+ * Copyright (C) 2023 - ntop.org
+ * Copyright (C) 2023 - V.G <jacendi@protonmail.com>
+ *
+ * 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"
+
+#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_NOMACHINE
+
+#include "ndpi_api.h"
+#include "ndpi_private.h"
+
+static void ndpi_int_nomachine_add_connection(struct ndpi_detection_module_struct *ndpi_struct, 
+                                              struct ndpi_flow_struct *flow)
+{
+  NDPI_LOG_INFO(ndpi_struct, "found NoMachine\n");
+  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_NOMACHINE,
+                             NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);
+  ndpi_set_risk(ndpi_struct, flow, NDPI_DESKTOP_OR_FILE_SHARING_SESSION, "Found NoMachine");
+}
+
+static void ndpi_search_nomachine(struct ndpi_detection_module_struct *ndpi_struct,
+                                  struct ndpi_flow_struct *flow)
+{
+  struct ndpi_packet_struct const * const packet = &ndpi_struct->packet;
+
+  NDPI_LOG_DBG(ndpi_struct, "search NoMachine\n");
+
+  if (packet->tcp != NULL) {
+    /* A NoMachine connection starts with a handshake that contains 
+     * only the characters NXSH (request) & NXD (response) and a version 
+     * number. After that it is followed by a TLS handshake. */
+    if ((packet->payload_packet_len > 10 && packet->payload_packet_len < 15) &&
+        ((memcmp(packet->payload, "NXSH-", 5) == 0) || (memcmp(packet->payload, "NXD-", 4) == 0)))
+    {
+      ndpi_int_nomachine_add_connection(ndpi_struct, flow);
+      return;
+    }
+  } else if (packet->udp != NULL) {
+    /* NoMachine uses UDP for multimedia data */
+    if (packet->payload_packet_len > 9 && /* Shortest valid packet is 10 bytes long, probably it's keep-alive */
+        le16toh(get_u_int16_t(packet->payload, 2)) == 1 &&
+        le16toh(get_u_int16_t(packet->payload, 4)) == packet->payload_packet_len &&
+        get_u_int16_t(packet->payload, 8) == 0)
+    {
+      ndpi_int_nomachine_add_connection(ndpi_struct, flow);
+      return;
+    }
+  }
+
+  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+}
+void init_nomachine_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id)
+{
+  ndpi_set_bitmask_protocol_detection("NoMachine", ndpi_struct, *id,
+                                      NDPI_PROTOCOL_NOMACHINE,
+                                      ndpi_search_nomachine,
+                                      NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD_WITHOUT_RETRANSMISSION,
+                                      SAVE_DETECTION_BITMASK_AS_UNKNOWN,
+                                      ADD_TO_DETECTION_BITMASK);
+
+  *id += 1;
+}