prop224: Build ESTABLISH_RENDEZVOUS cell and logic

Add a function to build the cell.

Add a the logic to send the cell when the rendezvous circuit opens.

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

5 files changed, 74 insertions, 1 deletions

diff --git a/src/or/hs_cell.c b/src/or/hs_cell.c
index 889cf7749b..64e164c061 100644
--- a/src/or/hs_cell.c
+++ b/src/or/hs_cell.c
@@ -847,3 +847,20 @@ hs_cell_build_introduce1(const hs_cell_introduce1_data_t *data,
   return cell_len;
 }
 
+/* Build an ESTABLISH_RENDEZVOUS cell from the given rendezvous_cookie. The
+ * encoded cell is put in cell_out which must be of at least
+ * RELAY_PAYLOAD_SIZE. On success, the encoded length is returned and the
+ * caller should clear up the content of the cell.
+ *
+ * This function can't fail. */
+ssize_t
+hs_cell_build_establish_rendezvous(const uint8_t *rendezvous_cookie,
+                                   uint8_t *cell_out)
+{
+  tor_assert(rendezvous_cookie);
+  tor_assert(cell_out);
+
+  memcpy(cell_out, rendezvous_cookie, HS_REND_COOKIE_LEN);
+  return HS_REND_COOKIE_LEN;
+}
+
diff --git a/src/or/hs_cell.h b/src/or/hs_cell.h
index a72009510c..29e451cf0f 100644
--- a/src/or/hs_cell.h
+++ b/src/or/hs_cell.h
@@ -93,6 +93,8 @@ ssize_t hs_cell_build_rendezvous1(const uint8_t *rendezvous_cookie,
                                   uint8_t *cell_out);
 ssize_t hs_cell_build_introduce1(const hs_cell_introduce1_data_t *data,
                                  uint8_t *cell_out);
+ssize_t hs_cell_build_establish_rendezvous(const uint8_t *rendezvous_cookie,
+                                           uint8_t *cell_out);
 
 /* Parse cell API. */
 ssize_t hs_cell_parse_intro_established(const uint8_t *payload,
diff --git a/src/or/hs_circuit.c b/src/or/hs_circuit.c
index 95100e9b3a..ee453d0d52 100644
--- a/src/or/hs_circuit.c
+++ b/src/or/hs_circuit.c
@@ -1084,3 +1084,54 @@ hs_circ_send_introduce1(origin_circuit_t *intro_circ,
   return ret;
 }
 
+/* Send an ESTABLISH_RENDEZVOUS cell along the rendezvous circuit circ. On
+ * success, 0 is returned else -1 and the circuit is marked for close. */
+int
+hs_circ_send_establish_rendezvous(origin_circuit_t *circ)
+{
+  ssize_t cell_len = 0;
+  uint8_t cell[RELAY_PAYLOAD_SIZE] = {0};
+
+  tor_assert(circ);
+  tor_assert(TO_CIRCUIT(circ)->purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND);
+
+  log_info(LD_REND, "Send an ESTABLISH_RENDEZVOUS cell on circuit %u",
+           TO_CIRCUIT(circ)->n_circ_id);
+
+  /* Set timestamp_dirty, because circuit_expire_building expects it,
+   * and the rend cookie also means we've used the circ. */
+  TO_CIRCUIT(circ)->timestamp_dirty = time(NULL);
+
+  /* We've attempted to use this circuit. Probe it if we fail */
+  pathbias_count_use_attempt(circ);
+
+  /* Generate the RENDEZVOUS_COOKIE and place it in the identifier so we can
+   * complete the handshake when receiving the acknowledgement. */
+  crypto_rand((char *) circ->hs_ident->rendezvous_cookie, HS_REND_COOKIE_LEN);
+  /* Generate the client keypair. No need to be extra strong, not long term */
+  curve25519_keypair_generate(&circ->hs_ident->rendezvous_client_kp, 0);
+
+  cell_len =
+    hs_cell_build_establish_rendezvous(circ->hs_ident->rendezvous_cookie,
+                                       cell);
+  if (BUG(cell_len < 0)) {
+    goto err;
+  }
+
+  if (relay_send_command_from_edge(CONTROL_CELL_ID, TO_CIRCUIT(circ),
+                                   RELAY_COMMAND_ESTABLISH_RENDEZVOUS,
+                                   (const char *) cell, cell_len,
+                                   circ->cpath->prev) < 0) {
+    /* Circuit has been marked for close */
+    log_warn(LD_REND, "Unable to send ESTABLISH_RENDEZVOUS cell on "
+                      "circuit %u", TO_CIRCUIT(circ)->n_circ_id);
+    memwipe(cell, 0, cell_len);
+    goto err;
+  }
+
+  memwipe(cell, 0, cell_len);
+  return 0;
+ err:
+  return -1;
+}
+
diff --git a/src/or/hs_circuit.h b/src/or/hs_circuit.h
index f35ebf17db..3b0e3aca1c 100644
--- a/src/or/hs_circuit.h
+++ b/src/or/hs_circuit.h
@@ -48,6 +48,7 @@ int hs_circ_send_introduce1(origin_circuit_t *intro_circ,
                             origin_circuit_t *rend_circ,
                             const hs_desc_intro_point_t *ip,
                             const uint8_t *subcredential);
+int hs_circ_send_establish_rendezvous(origin_circuit_t *circ);
 
 /* e2e circuit API. */
 
diff --git a/src/or/hs_client.c b/src/or/hs_client.c
index b06f3d9355..8865bb5fb5 100644
--- a/src/or/hs_client.c
+++ b/src/or/hs_client.c
@@ -381,7 +381,9 @@ client_rendezvous_circ_has_opened(origin_circuit_t *circ)
            safe_str_client(
                 extend_info_describe(circ->build_state->chosen_exit)));
 
-  /* XXX Send ESTABLISH REND cell. */
+  /* Ignore returned value, nothing we can really do. On failure, the circuit
+   * will be marked for close. */
+  hs_circ_send_establish_rendezvous(circ);
 }
 
 /* ========== */