wireguard: add dos mitigation support

Type: feature

With this change:
 - if the number of received handshake messages exceeds the limit
   calculated based on the peers number, under load state will activate;
 - if being under load a handshake message with a valid mac1 is
   received, but mac2 is invalid, a cookie reply will be sent.

Also, cover these with tests.

Signed-off-by: Alexander Chernavin <achernavin@netgate.com>
Change-Id: I3003570a9cf807cfb0b5145b89a085455c30e717

1 files changed, 24 insertions, 6 deletions

diff --git a/src/plugins/wireguard/wireguard_input.c b/src/plugins/wireguard/wireguard_input.c
index ef60d50c3da..3f546cc494f 100644
--- a/src/plugins/wireguard/wireguard_input.c
+++ b/src/plugins/wireguard/wireguard_input.c
@@ -32,6 +32,7 @@
   _ (HANDSHAKE_SEND, "Failed while sending Handshake")                        \
   _ (HANDSHAKE_RECEIVE, "Failed while receiving Handshake")                   \
   _ (COOKIE_DECRYPTION, "Failed during Cookie decryption")                    \
+  _ (COOKIE_SEND, "Failed during sending Cookie")                             \
   _ (TOO_BIG, "Packet too big")                                               \
   _ (UNDEFINED, "Undefined error")                                            \
   _ (CRYPTO_ENGINE_ERROR, "crypto engine error (packet dropped)")
@@ -173,7 +174,6 @@ wg_handshake_process (vlib_main_t *vm, wg_main_t *wmp, vlib_buffer_t *b,
   u16 udp_dst_port = clib_host_to_net_u16 (uhd->dst_port);;
 
   message_header_t *header = current_b_data;
-  under_load = false;
 
   if (PREDICT_FALSE (header->type == MESSAGE_HANDSHAKE_COOKIE))
     {
@@ -211,11 +211,13 @@ wg_handshake_process (vlib_main_t *vm, wg_main_t *wmp, vlib_buffer_t *b,
       if (NULL == wg_if)
 	continue;
 
+      under_load = wg_if_is_under_load (vm, wg_if);
       mac_state = cookie_checker_validate_macs (
 	vm, &wg_if->cookie_checker, macs, current_b_data, len, under_load,
 	&src_ip, udp_src_port);
       if (mac_state == INVALID_MAC)
 	{
+	  wg_if_dec_handshake_num (wg_if);
 	  wg_if = NULL;
 	  continue;
 	}
@@ -241,8 +243,16 @@ wg_handshake_process (vlib_main_t *vm, wg_main_t *wmp, vlib_buffer_t *b,
 
 	if (packet_needs_cookie)
 	  {
-	    // TODO: Add processing
+
+	    if (!wg_send_handshake_cookie (vm, message->sender_index,
+					   &wg_if->cookie_checker, macs,
+					   &ip_addr_46 (&wg_if->src_ip),
+					   wg_if->port, &src_ip, udp_src_port))
+	      return WG_INPUT_ERROR_COOKIE_SEND;
+
+	    return WG_INPUT_ERROR_NONE;
 	  }
+
 	noise_remote_t *rp;
 	if (noise_consume_initiation
 	    (vm, noise_local_get (wg_if->local_idx), &rp,
@@ -271,6 +281,18 @@ wg_handshake_process (vlib_main_t *vm, wg_main_t *wmp, vlib_buffer_t *b,
     case MESSAGE_HANDSHAKE_RESPONSE:
       {
 	message_handshake_response_t *resp = current_b_data;
+
+	if (packet_needs_cookie)
+	  {
+	    if (!wg_send_handshake_cookie (vm, resp->sender_index,
+					   &wg_if->cookie_checker, macs,
+					   &ip_addr_46 (&wg_if->src_ip),
+					   wg_if->port, &src_ip, udp_src_port))
+	      return WG_INPUT_ERROR_COOKIE_SEND;
+
+	    return WG_INPUT_ERROR_NONE;
+	  }
+
 	index_t peeri = INDEX_INVALID;
 	u32 *entry =
 	  wg_index_table_lookup (&wmp->index_table, resp->receiver_index);
@@ -292,10 +314,6 @@ wg_handshake_process (vlib_main_t *vm, wg_main_t *wmp, vlib_buffer_t *b,
 	  {
 	    return WG_INPUT_ERROR_PEER;
 	  }
-	if (packet_needs_cookie)
-	  {
-	    // TODO: Add processing
-	  }
 
 	// set_peer_address (peer, ip4_src, udp_src_port);
 	if (noise_remote_begin_session (vm, &peer->remote))