p2p: reject incoming connections to self

src/p2p/net_node.inl

@@ -2227,6 +2227,15 @@ namespace nodetool
 
     network_zone& zone = m_network_zones.at(context.m_remote_address.get_zone());
 
+    // test only the remote end's zone, otherwise an attacker could connect to you on clearnet
+    // and pass in a tor connection's peer id, and deduce the two are the same if you reject it
+    if(arg.node_data.peer_id == zone.m_config.m_peer_id)
+    {
+      LOG_DEBUG_CC(context, "Connection to self detected, dropping connection");
+      drop_connection(context);
+      return 1;
+    }
+
     if (zone.m_current_number_of_in_peers >= zone.m_config.m_net_config.max_in_connection_count) // in peers limit
     {
       LOG_WARNING_CC(context, "COMMAND_HANDSHAKE came, but already have max incoming connections, so dropping this one.");
@@ -2253,7 +2262,7 @@ namespace nodetool
     context.m_in_timedsync = false;
     context.m_rpc_port = arg.node_data.rpc_port;
 
-    if(arg.node_data.peer_id != zone.m_config.m_peer_id && arg.node_data.my_port && zone.m_can_pingback)
+    if(arg.node_data.my_port && zone.m_can_pingback)
     {
       peerid_type peer_id_l = arg.node_data.peer_id;
       uint32_t port_l = arg.node_data.my_port;