hs_pow: add per-circuit effort information to control port

This lets controller apps see the outgoing PoW effort on client
circuits, and the validated effort received on an incoming service
circuit.

Signed-off-by: Micah Elizabeth Scott <beth@torproject.org>

src/core/or/origin_circuit_st.h

@@ -212,6 +212,10 @@ struct origin_circuit_t {
    * (in host byte order) for response comparison. */
   uint32_t pathbias_probe_nonce;
 
+  /** This is nonzero iff hs_with_pow_circ is set and there was a valid proof
+   * of work solution associated with this circuit. */
+  uint32_t hs_pow_effort;
+
   /** Set iff this is a hidden-service circuit for a HS with PoW defenses
    * enabled, so that we know to be more lenient with timing out the
    * circuit-build to allow the service time to work through the queue of

src/feature/control/control_fmt.c

@@ -153,6 +153,13 @@ circuit_describe_status_for_controller(origin_circuit_t *circ)
     tor_free(socks_password_escaped);
   }
 
+  /* Attach the proof-of-work solution effort, if it's nonzero. Clients set
+   * this to the effort they've chosen, services set this to a value that
+   * was provided by the client and then verified by the service. */
+  if (circ->hs_pow_effort > 0) {
+    smartlist_add_asprintf(descparts, "HS_POW=v1,%u", circ->hs_pow_effort);
+  }
+
   rv = smartlist_join_strings(descparts, " ", 0, NULL);
 
   SMARTLIST_FOREACH(descparts, char *, cp, tor_free(cp));

src/feature/hs/hs_circuit.c

@@ -429,6 +429,13 @@ launch_rendezvous_point_circuit,(const hs_service_t *service,
     tor_assert(circ->hs_ident);
   }
 
+  /* Remember PoW state if this introduction included a valid proof of work
+   * client puzzle extension. */
+  if (rdv_data->pow_effort > 0) {
+    circ->hs_pow_effort = rdv_data->pow_effort;
+    circ->hs_with_pow_circ = 1;
+  }
+
   /* Setup congestion control if asked by the client from the INTRO cell. */
   if (rdv_data->cc_enabled) {
     hs_circ_setup_congestion_control(circ, congestion_control_sendme_inc(),

src/feature/hs/hs_pow.c

@@ -446,6 +446,9 @@ pow_worker_replyfn(void *work_)
      * timing out while waiting for the service-side circuit to be built. */
     rend_circ->hs_with_pow_circ = 1;
 
+    /* Remember the PoW effort we chose, for client-side rend circuits. */
+    rend_circ->hs_pow_effort = job->pow_inputs.effort;
+
     // and then send that intro cell
     if (send_introduce1(intro_circ, rend_circ,
                         desc, job->pow_solution_out, ip) < 0) {