Improved dnscrypt v1/v2 protocol detection.

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/src/lib/protocols/dnscrypt.c b/src/lib/protocols/dnscrypt.c
new file mode 100644
index 000000000..6c89466f1
--- /dev/null
+++ b/src/lib/protocols/dnscrypt.c
@@ -0,0 +1,69 @@
+/*
+ * dnscrypt.c
+ *
+ * Copyright (C) 2020 - ntop.org
+ *
+ * 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_DNSCRYPT
+
+#include "ndpi_api.h"
+
+static void ndpi_int_dnscrypt_add_connection(struct ndpi_detection_module_struct *ndpi_struct,
+                                             struct ndpi_flow_struct *flow)
+{
+  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_DNSCRYPT, NDPI_PROTOCOL_UNKNOWN);
+}
+
+void ndpi_search_dnscrypt(struct ndpi_detection_module_struct *ndpi_struct,
+                          struct ndpi_flow_struct *flow)
+{
+  struct ndpi_packet_struct *packet = &flow->packet;
+  static char const * const dnscrypt_initial = "2\rdnscrypt";
+
+  NDPI_LOG_DBG(ndpi_struct, "search dnscrypt\n");
+
+  if (flow->packet_counter > 2)
+  {
+    NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+  }
+
+  /* dnscrypt protocol version 1: check magic */
+  if (packet->payload_packet_len >= 64 &&
+      strncmp((char*)packet->payload, "r6fnvWj8", strlen("r6fnvWj8")) == 0)
+  {
+    ndpi_int_dnscrypt_add_connection(ndpi_struct, flow);
+  }
+  /* dnscrypt protocol version 1 and 2: resolver ping */
+  if (packet->payload_packet_len > 13 + strlen(dnscrypt_initial) &&
+      strncasecmp((char*)packet->payload + 13, dnscrypt_initial, strlen(dnscrypt_initial)) == 0)
+  {
+    ndpi_int_dnscrypt_add_connection(ndpi_struct, flow);
+  }
+}
+
+void init_dnscrypt_dissector(struct ndpi_detection_module_struct *ndpi_struct, u_int32_t *id,
+                             NDPI_PROTOCOL_BITMASK *detection_bitmask)
+{
+  ndpi_set_bitmask_protocol_detection(
+    "DNScrypt", ndpi_struct, detection_bitmask, *id,
+    NDPI_PROTOCOL_DNSCRYPT, ndpi_search_dnscrypt, NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_TCP_OR_UDP_WITH_PAYLOAD,
+    SAVE_DETECTION_BITMASK_AS_UNKNOWN, ADD_TO_DETECTION_BITMASK);
+  *id += 1;
+}
+