prop224: Support INTRODUCE2 cell replay cache

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

src/or/hs_cell.c

@@ -9,6 +9,7 @@
 #include "or.h"
 #include "config.h"
 #include "rendservice.h"
+#include "replaycache.h"
 
 #include "hs_cell.h"
 #include "hs_ntor.h"
@@ -460,6 +461,7 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data,
                          const hs_service_t *service)
 {
   int ret = -1;
+  time_t elapsed;
   uint8_t *decrypted = NULL;
   size_t encrypted_section_len;
   const uint8_t *encrypted_section;
@@ -477,8 +479,6 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data,
     goto done;
   }
 
-  /* XXX: Add/Test replaycache. */
-
   log_info(LD_REND, "Received a decodable INTRODUCE2 cell on circuit %u "
                     "for service %s. Decoding encrypted section...",
            TO_CIRCUIT(circ)->n_circ_id,
@@ -498,6 +498,15 @@ hs_cell_parse_introduce2(hs_cell_introduce2_data_t *data,
     goto done;
   }
 
+  /* Check our replay cache for this introduction point. */
+  if (replaycache_add_test_and_elapsed(data->replay_cache, encrypted_section,
+                                       encrypted_section_len, &elapsed)) {
+    log_warn(LD_REND, "Possible replay detected! An INTRODUCE2 cell with the"
+                      "same ENCRYPTED section was seen %ld seconds ago. "
+                      "Dropping cell.", elapsed);
+    goto done;
+  }
+
   /* Build the key material out of the key material found in the cell. */
   intro_keys = get_introduce2_key_material(data->auth_pk, data->enc_kp,
                                            data->subcredential,

src/or/hs_cell.h

@@ -47,6 +47,8 @@ typedef struct hs_cell_introduce2_data_t {
   curve25519_public_key_t client_pk;
   /* Link specifiers of the rendezvous point. Contains link_specifier_t. */
   smartlist_t *link_specifiers;
+  /* Replay cache of the introduction point. */
+  replaycache_t *replay_cache;
 } hs_cell_introduce2_data_t;
 
 /* Build cell API. */

src/or/hs_circuit.c

@@ -811,6 +811,7 @@ hs_circ_handle_introduce2(const hs_service_t *service,
   data.payload_len = payload_len;
   data.link_specifiers = smartlist_new();
   data.is_legacy = ip->base.is_only_legacy;
+  data.replay_cache = ip->replay_cache;
 
   if (hs_cell_parse_introduce2(&data, circ, service) < 0) {
     goto done;