dos: Add the DoSRefuseSingleHopClientRendezvous option

This option refuses any ESTABLISH_RENDEZVOUS cell arriving from a client
connection. Its default value is "auto" for which we can turn it on or off
with a consensus parameter. Default value is 0.

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/or/rendmid.c b/src/or/rendmid.c
index ca0ad7b0d4..441d5043ce 100644
--- a/src/or/rendmid.c
+++ b/src/or/rendmid.c
@@ -8,9 +8,11 @@
  **/
 
 #include "or.h"
+#include "channel.h"
 #include "circuitlist.h"
 #include "circuituse.h"
 #include "config.h"
+#include "dos.h"
 #include "relay.h"
 #include "rendmid.h"
 #include "rephist.h"
@@ -246,6 +248,16 @@ rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
     goto err;
   }
 
+  /* Check if we are configured to accept established rendezvous cells from
+   * client or in other words tor2web clients. */
+  if (channel_is_client(circ->p_chan) &&
+      dos_should_refuse_single_hop_client()) {
+    /* Note it down for the heartbeat log purposes. */
+    dos_note_refuse_single_hop_client();
+    /* Silent drop so the client has to time out before moving on. */
+    return 0;
+  }
+
   if (circ->base_.n_chan) {
     log_warn(LD_PROTOCOL,
              "Tried to establish rendezvous on non-edge circuit");