text: /* Copyright (c) 2017, The Tor Project, Inc. */
  /* See LICENSE for licensing information */
  
  /**
   * \file hs_circuit.c
   **/
  
  #define HS_CIRCUIT_PRIVATE
  
  #include "or.h"
  #include "circpathbias.h"
  #include "circuitbuild.h"
  #include "circuitlist.h"
  #include "circuituse.h"
  #include "config.h"
  #include "policies.h"
  #include "relay.h"
  #include "rendservice.h"
  #include "rephist.h"
  #include "router.h"
  
  #include "hs_cell.h"
  #include "hs_ident.h"
  #include "hs_ntor.h"
  #include "hs_service.h"
  #include "hs_circuit.h"
  
  /* Trunnel. */
  #include "ed25519_cert.h"
  #include "hs/cell_common.h"
  #include "hs/cell_establish_intro.h"
  
  /* A circuit is about to become an e2e rendezvous circuit. Check
   * <b>circ_purpose</b> and ensure that it's properly set. Return true iff
   * circuit purpose is properly set, otherwise return false. */
  static int
  circuit_purpose_is_correct_for_rend(unsigned int circ_purpose,
                                      int is_service_side)
  {
    if (is_service_side) {
      if (circ_purpose != CIRCUIT_PURPOSE_S_CONNECT_REND) {
        log_warn(LD_BUG,
              "HS e2e circuit setup with wrong purpose (%d)", circ_purpose);
        return 0;
      }
    }
  
    if (!is_service_side) {
      if (circ_purpose != CIRCUIT_PURPOSE_C_REND_READY &&
          circ_purpose != CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED) {
        log_warn(LD_BUG,
              "Client e2e circuit setup with wrong purpose (%d)", circ_purpose);
        return 0;
      }
    }
  
    return 1;
  }
  
  /* Create and return a crypt path for the final hop of a v3 prop224 rendezvous
   * circuit. Initialize the crypt path crypto using the output material from the
   * ntor key exchange at <b>ntor_key_seed</b>.
   *
   * If <b>is_service_side</b> is set, we are the hidden service and the final
   * hop of the rendezvous circuit is the client on the other side. */
  static crypt_path_t *
  create_rend_cpath(const uint8_t *ntor_key_seed, size_t seed_len,
                    int is_service_side)
  {
    uint8_t keys[HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN];
    crypt_path_t *cpath = NULL;
  
    /* Do the key expansion */
    if (hs_ntor_circuit_key_expansion(ntor_key_seed, seed_len,
                                      keys, sizeof(keys)) < 0) {
      goto err;
    }
  
    /* Setup the cpath */
    cpath = tor_malloc_zero(sizeof(crypt_path_t));
    cpath->magic = CRYPT_PATH_MAGIC;
  
    if (circuit_init_cpath_crypto(cpath, (char*)keys, sizeof(keys),
                                  is_service_side, 1) < 0) {
      tor_free(cpath);
      goto err;
    }
  
   err:
    memwipe(keys, 0, sizeof(keys));
    return cpath;
  }
  
  /* We are a v2 legacy HS client: Create and return a crypt path for the hidden
   * service on the other side of the rendezvous circuit <b>circ</b>. Initialize
   * the crypt path crypto using the body of the RENDEZVOUS1 cell at
   * <b>rend_cell_body</b> (which must be at least DH_KEY_LEN+DIGEST_LEN bytes).
   */
  static crypt_path_t *
  create_rend_cpath_legacy(origin_circuit_t *circ, const uint8_t *rend_cell_body)
  {
    crypt_path_t *hop = NULL;
    char keys[DIGEST_LEN+CPATH_KEY_MATERIAL_LEN];
  
    /* first DH_KEY_LEN bytes are g^y from the service. Finish the dh
     * handshake...*/
    tor_assert(circ->build_state);
    tor_assert(circ->build_state->pending_final_cpath);
    hop = circ->build_state->pending_final_cpath;
  
    tor_assert(hop->rend_dh_handshake_state);
    if (crypto_dh_compute_secret(LOG_PROTOCOL_WARN, hop->rend_dh_handshake_state,
                                 (char*)rend_cell_body, DH_KEY_LEN,
                                 keys, DIGEST_LEN+CPATH_KEY_MATERIAL_LEN)<0) {
      log_warn(LD_GENERAL, "Couldn't complete DH handshake.");
      goto err;
    }
    /* ... and set up cpath. */
    if (circuit_init_cpath_crypto(hop,
                                  keys+DIGEST_LEN, sizeof(keys)-DIGEST_LEN,
                                  0, 0) < 0)
      goto err;
  
    /* Check whether the digest is right... */
    if (tor_memneq(keys, rend_cell_body+DH_KEY_LEN, DIGEST_LEN)) {
      log_warn(LD_PROTOCOL, "Incorrect digest of key material.");
      goto err;
    }
  
    /* clean up the crypto stuff we just made */
    crypto_dh_free(hop->rend_dh_handshake_state);
    hop->rend_dh_handshake_state = NULL;
  
    goto done;
  
   err:
    hop = NULL;
  
   done:
    memwipe(keys, 0, sizeof(keys));
    return hop;
  }
  
  /* Append the final <b>hop</b> to the cpath of the rend <b>circ</b>, and mark
   * <b>circ</b> ready for use to transfer HS relay cells. */
  static void
  finalize_rend_circuit(origin_circuit_t *circ, crypt_path_t *hop,
                        int is_service_side)
  {
    tor_assert(circ);
    tor_assert(hop);
  
    /* Notify the circuit state machine that we are splicing this circuit */
    int new_circ_purpose = is_service_side ?
      CIRCUIT_PURPOSE_S_REND_JOINED : CIRCUIT_PURPOSE_C_REND_JOINED;
    circuit_change_purpose(TO_CIRCUIT(circ), new_circ_purpose);
  
    /* All is well. Extend the circuit. */
    hop->state = CPATH_STATE_OPEN;
    /* Set the windows to default. */
    hop->package_window = circuit_initial_package_window();
    hop->deliver_window = CIRCWINDOW_START;
  
    /* Now that this circuit has finished connecting to its destination,
     * make sure circuit_get_open_circ_or_launch is willing to return it
     * so we can actually use it. */
    circ->hs_circ_has_timed_out = 0;
  
    /* Append the hop to the cpath of this circuit */
    onion_append_to_cpath(&circ->cpath, hop);
  
    /* In legacy code, 'pending_final_cpath' points to the final hop we just
     * appended to the cpath. We set the original pointer to NULL so that we
     * don't double free it. */
    if (circ->build_state) {
      circ->build_state->pending_final_cpath = NULL;
    }
  
    /* Finally, mark circuit as ready to be used for client streams */
    if (!is_service_side) {
      circuit_try_attaching_streams(circ);
    }
  }
  
  /* For a given circuit and a service introduction point object, register the
   * intro circuit to the circuitmap. This supports legacy intro point. */
  static void
  register_intro_circ(const hs_service_intro_point_t *ip,
                      origin_circuit_t *circ)
  {
    tor_assert(ip);
    tor_assert(circ);
  
    if (ip->base.is_only_legacy) {
      uint8_t digest[DIGEST_LEN];
      if (BUG(crypto_pk_get_digest(ip->legacy_key, (char *) digest) < 0)) {
        return;
      }
      hs_circuitmap_register_intro_circ_v2_service_side(circ, digest);
    } else {
      hs_circuitmap_register_intro_circ_v3_service_side(circ,
                                           &ip->auth_key_kp.pubkey);
    }
  }
  
  /* Return the number of opened introduction circuit for the given circuit that
   * is matching its identity key. */
  static unsigned int
  count_opened_desc_intro_point_circuits(const hs_service_t *service,
                                         const hs_service_descriptor_t *desc)
  {
    unsigned int count = 0;
  
    tor_assert(service);
    tor_assert(desc);
  
    DIGEST256MAP_FOREACH(desc->intro_points.map, key,
                         const hs_service_intro_point_t *, ip) {
      const circuit_t *circ;
      const origin_circuit_t *ocirc = hs_circ_service_get_intro_circ(ip);
      if (ocirc == NULL) {
        continue;
      }
      circ = TO_CIRCUIT(ocirc);
      tor_assert(circ->purpose == CIRCUIT_PURPOSE_S_ESTABLISH_INTRO ||
                 circ->purpose == CIRCUIT_PURPOSE_S_INTRO);
      /* Having a circuit not for the requested service is really bad. */
      tor_assert(ed25519_pubkey_eq(&service->keys.identity_pk,
                                   &ocirc->hs_ident->identity_pk));
      /* Only count opened circuit and skip circuit that will be closed. */
      if (!circ->marked_for_close && circ->state == CIRCUIT_STATE_OPEN) {
        count++;
      }
    } DIGEST256MAP_FOREACH_END;
    return count;
  }
  
  /* From a given service, rendezvous cookie and handshake info, create a
   * rendezvous point circuit identifier. This can't fail. */
  STATIC hs_ident_circuit_t *
  create_rp_circuit_identifier(const hs_service_t *service,
                               const uint8_t *rendezvous_cookie,
                               const curve25519_public_key_t *server_pk,
                               const hs_ntor_rend_cell_keys_t *keys)
  {
    hs_ident_circuit_t *ident;
    uint8_t handshake_info[CURVE25519_PUBKEY_LEN + DIGEST256_LEN];
  
    tor_assert(service);
    tor_assert(rendezvous_cookie);
    tor_assert(server_pk);
    tor_assert(keys);
  
    ident = hs_ident_circuit_new(&service->keys.identity_pk,
                                 HS_IDENT_CIRCUIT_RENDEZVOUS);
    /* Copy the RENDEZVOUS_COOKIE which is the unique identifier. */
    memcpy(ident->rendezvous_cookie, rendezvous_cookie,
           sizeof(ident->rendezvous_cookie));
    /* Build the HANDSHAKE_INFO which looks like this:
     *    SERVER_PK        [32 bytes]
     *    AUTH_INPUT_MAC   [32 bytes]
     */
    memcpy(handshake_info, server_pk->public_key, CURVE25519_PUBKEY_LEN);
    memcpy(handshake_info + CURVE25519_PUBKEY_LEN, keys->rend_cell_auth_mac,
           DIGEST256_LEN);
    tor_assert(sizeof(ident->rendezvous_handshake_info) ==
               sizeof(handshake_info));
    memcpy(ident->rendezvous_handshake_info, handshake_info,
           sizeof(ident->rendezvous_handshake_info));
    /* Finally copy the NTOR_KEY_SEED for e2e encryption on the circuit. */
    tor_assert(sizeof(ident->rendezvous_ntor_key_seed) ==
               sizeof(keys->ntor_key_seed));
    memcpy(ident->rendezvous_ntor_key_seed, keys->ntor_key_seed,
           sizeof(ident->rendezvous_ntor_key_seed));
    return ident;
  }
  
  /* From a given service and service intro point, create an introduction point
   * circuit identifier. This can't fail. */
  static hs_ident_circuit_t *
  create_intro_circuit_identifier(const hs_service_t *service,
                                  const hs_service_intro_point_t *ip)
  {
    hs_ident_circuit_t *ident;
  
    tor_assert(service);
    tor_assert(ip);
  
    ident = hs_ident_circuit_new(&service->keys.identity_pk,
                                 HS_IDENT_CIRCUIT_INTRO);
    ed25519_pubkey_copy(&ident->intro_auth_pk, &ip->auth_key_kp.pubkey);
  
    return ident;
  }
  
  /* For a given introduction point and an introduction circuit, send the
   * ESTABLISH_INTRO cell. The service object is used for logging. This can fail
   * and if so, the circuit is closed and the intro point object is flagged
   * that the circuit is not established anymore which is important for the
   * retry mechanism. */
  static void
  send_establish_intro(const hs_service_t *service,
                       hs_service_intro_point_t *ip, origin_circuit_t *circ)
  {
    ssize_t cell_len;
    uint8_t payload[RELAY_PAYLOAD_SIZE];
  
    tor_assert(service);
    tor_assert(ip);
    tor_assert(circ);
  
    /* Encode establish intro cell. */
    cell_len = hs_cell_build_establish_intro(circ->cpath->prev->rend_circ_nonce,
                                             ip, payload);
    if (cell_len < 0) {
      log_warn(LD_REND, "Unable to encode ESTABLISH_INTRO cell for service %s "
                        "on circuit %u. Closing circuit.",
               safe_str_client(service->onion_address),
               TO_CIRCUIT(circ)->n_circ_id);
      goto err;
    }
  
    /* Send the cell on the circuit. */
    if (relay_send_command_from_edge(CONTROL_CELL_ID, TO_CIRCUIT(circ),
                                     RELAY_COMMAND_ESTABLISH_INTRO,
                                     (char *) payload, cell_len,
                                     circ->cpath->prev) < 0) {
      log_info(LD_REND, "Unable to send ESTABLISH_INTRO cell for service %s "
                        "on circuit %u.",
               safe_str_client(service->onion_address),
               TO_CIRCUIT(circ)->n_circ_id);
      /* On error, the circuit has been closed. */
      goto done;
    }
  
    /* Record the attempt to use this circuit. */
    pathbias_count_use_attempt(circ);
    goto done;
  
   err:
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
   done:
    memwipe(payload, 0, sizeof(payload));
  }
  
  /* Return a string constant describing the anonymity of service. */
  static const char *
  get_service_anonymity_string(const hs_service_t *service)
  {
    if (service->config.is_single_onion) {
      return "single onion";
    } else {
      return "hidden";
    }
  }
  
  /* For a given service, the ntor onion key and a rendezvous cookie, launch a
   * circuit to the rendezvous point specified by the link specifiers. On
   * success, a circuit identifier is attached to the circuit with the needed
   * data. This function will try to open a circuit for a maximum value of
   * MAX_REND_FAILURES then it will give up. */
  static void
  launch_rendezvous_point_circuit(const hs_service_t *service,
                                  const hs_service_intro_point_t *ip,
                                  const hs_cell_introduce2_data_t *data)
  {
    int circ_needs_uptime;
    time_t now = time(NULL);
    extend_info_t *info = NULL;
    origin_circuit_t *circ;
  
    tor_assert(service);
    tor_assert(ip);
    tor_assert(data);
  
    circ_needs_uptime = hs_service_requires_uptime_circ(service->config.ports);
  
    /* Get the extend info data structure for the chosen rendezvous point
     * specified by the given link specifiers. */
    info = hs_get_extend_info_from_lspecs(data->link_specifiers,
                                          &data->onion_pk,
                                          service->config.is_single_onion);
    if (info == NULL) {
      /* We are done here, we can't extend to the rendezvous point.
       * If you're running an IPv6-only v3 single onion service on 0.3.2 or with
       * 0.3.2 clients, and somehow disable the option check, it will fail here.
       */
      log_fn(LOG_PROTOCOL_WARN, LD_REND,
             "Not enough info to open a circuit to a rendezvous point for "
             "%s service %s.",
             get_service_anonymity_string(service),
             safe_str_client(service->onion_address));
      goto end;
    }
  
    for (int i = 0; i < MAX_REND_FAILURES; i++) {
      int circ_flags = CIRCLAUNCH_NEED_CAPACITY | CIRCLAUNCH_IS_INTERNAL;
      if (circ_needs_uptime) {
        circ_flags |= CIRCLAUNCH_NEED_UPTIME;
      }
      /* Firewall and policies are checked when getting the extend info. */
      if (service->config.is_single_onion) {
        circ_flags |= CIRCLAUNCH_ONEHOP_TUNNEL;
      }
  
      circ = circuit_launch_by_extend_info(CIRCUIT_PURPOSE_S_CONNECT_REND, info,
                                           circ_flags);
      if (circ != NULL) {
        /* Stop retrying, we have a circuit! */
        break;
      }
    }
    if (circ == NULL) {
      log_warn(LD_REND, "Giving up on launching a rendezvous circuit to %s "
                        "for %s service %s",
               safe_str_client(extend_info_describe(info)),
               get_service_anonymity_string(service),
               safe_str_client(service->onion_address));
      goto end;
    }
    log_info(LD_REND, "Rendezvous circuit launched to %s with cookie %s "
                      "for %s service %s",
             safe_str_client(extend_info_describe(info)),
             safe_str_client(hex_str((const char *) data->rendezvous_cookie,
                                     REND_COOKIE_LEN)),
             get_service_anonymity_string(service),
             safe_str_client(service->onion_address));
    tor_assert(circ->build_state);
    /* Rendezvous circuit have a specific timeout for the time spent on trying
     * to connect to the rendezvous point. */
    circ->build_state->expiry_time = now + MAX_REND_TIMEOUT;
  
    /* Create circuit identifier and key material. */
    {
      hs_ntor_rend_cell_keys_t keys;
      curve25519_keypair_t ephemeral_kp;
      /* No need for extra strong, this is only for this circuit life time. This
       * key will be used for the RENDEZVOUS1 cell that will be sent on the
       * circuit once opened. */
      curve25519_keypair_generate(&ephemeral_kp, 0);
      if (hs_ntor_service_get_rendezvous1_keys(&ip->auth_key_kp.pubkey,
                                               &ip->enc_key_kp,
                                               &ephemeral_kp, &data->client_pk,
                                               &keys) < 0) {
        /* This should not really happened but just in case, don't make tor
         * freak out, close the circuit and move on. */
        log_info(LD_REND, "Unable to get RENDEZVOUS1 key material for "
                          "service %s",
                 safe_str_client(service->onion_address));
        circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
        goto end;
      }
      circ->hs_ident = create_rp_circuit_identifier(service,
                                                    data->rendezvous_cookie,
                                                    &ephemeral_kp.pubkey, &keys);
      memwipe(&ephemeral_kp, 0, sizeof(ephemeral_kp));
      memwipe(&keys, 0, sizeof(keys));
      tor_assert(circ->hs_ident);
    }
  
   end:
    extend_info_free(info);
  }
  
  /* Return true iff the given service rendezvous circuit circ is allowed for a
   * relaunch to the rendezvous point. */
  static int
  can_relaunch_service_rendezvous_point(const origin_circuit_t *circ)
  {
    tor_assert(circ);
    /* This is initialized when allocating an origin circuit. */
    tor_assert(circ->build_state);
    tor_assert(TO_CIRCUIT(circ)->purpose == CIRCUIT_PURPOSE_S_CONNECT_REND);
  
    /* XXX: Retrying under certain condition. This is related to #22455. */
  
    /* Avoid to relaunch twice a circuit to the same rendezvous point at the
     * same time. */
    if (circ->hs_service_side_rend_circ_has_been_relaunched) {
      log_info(LD_REND, "Rendezvous circuit to %s has already been retried. "
                        "Skipping retry.",
               safe_str_client(
                    extend_info_describe(circ->build_state->chosen_exit)));
      goto disallow;
    }
  
    /* We check failure_count >= hs_get_service_max_rend_failures()-1 below, and
     * the -1 is because we increment the failure count for our current failure
     * *after* this clause. */
    int max_rend_failures = hs_get_service_max_rend_failures() - 1;
  
    /* A failure count that has reached maximum allowed or circuit that expired,
     * we skip relaunching. */
    if (circ->build_state->failure_count > max_rend_failures ||
        circ->build_state->expiry_time <= time(NULL)) {
      log_info(LD_REND, "Attempt to build a rendezvous circuit to %s has "
                        "failed with %d attempts and expiry time %ld. "
                        "Giving up building.",
               safe_str_client(
                    extend_info_describe(circ->build_state->chosen_exit)),
               circ->build_state->failure_count,
               (long int) circ->build_state->expiry_time);
      goto disallow;
    }
  
    /* Allowed to relaunch. */
    return 1;
   disallow:
    return 0;
  }
  
  /* Retry the rendezvous point of circ by launching a new circuit to it. */
  static void
  retry_service_rendezvous_point(const origin_circuit_t *circ)
  {
    int flags = 0;
    origin_circuit_t *new_circ;
    cpath_build_state_t *bstate;
  
    tor_assert(circ);
    /* This is initialized when allocating an origin circuit. */
    tor_assert(circ->build_state);
    tor_assert(TO_CIRCUIT(circ)->purpose == CIRCUIT_PURPOSE_S_CONNECT_REND);
  
    /* Ease our life. */
    bstate = circ->build_state;
  
    log_info(LD_REND, "Retrying rendezvous point circuit to %s",
             safe_str_client(extend_info_describe(bstate->chosen_exit)));
  
    /* Get the current build state flags for the next circuit. */
    flags |= (bstate->need_uptime) ? CIRCLAUNCH_NEED_UPTIME : 0;
    flags |= (bstate->need_capacity) ? CIRCLAUNCH_NEED_CAPACITY : 0;
    flags |= (bstate->is_internal) ? CIRCLAUNCH_IS_INTERNAL : 0;
  
    /* We do NOT add the onehop tunnel flag even though it might be a single
     * onion service. The reason is that if we failed once to connect to the RP
     * with a direct connection, we consider that chances are that we will fail
     * again so try a 3-hop circuit and hope for the best. Because the service
     * has no anonymity (single onion), this change of behavior won't affect
     * security directly. */
  
    new_circ = circuit_launch_by_extend_info(CIRCUIT_PURPOSE_S_CONNECT_REND,
                                             bstate->chosen_exit, flags);
    if (new_circ == NULL) {
      log_warn(LD_REND, "Failed to launch rendezvous circuit to %s",
               safe_str_client(extend_info_describe(bstate->chosen_exit)));
      goto done;
    }
  
    /* Transfer build state information to the new circuit state in part to
     * catch any other failures. */
    new_circ->build_state->failure_count = bstate->failure_count+1;
    new_circ->build_state->expiry_time = bstate->expiry_time;
    new_circ->hs_ident = hs_ident_circuit_dup(circ->hs_ident);
  
   done:
    return;
  }
  
  /* Using an extend info object ei, set all possible link specifiers in lspecs.
   * legacy ID is mandatory thus MUST be present in ei. If IPv4 is not present,
   * logs a BUG() warning, and returns an empty smartlist. Clients never make
   * direct connections to rendezvous points, so they should always have an
   * IPv4 address in ei. */
  static void
  get_lspecs_from_extend_info(const extend_info_t *ei, smartlist_t *lspecs)
  {
    link_specifier_t *ls;
  
    tor_assert(ei);
    tor_assert(lspecs);
  
    /* We require IPv4, we will add IPv6 support in a later tor version */
    if (BUG(!tor_addr_is_v4(&ei->addr))) {
      return;
    }
  
    ls = link_specifier_new();
    link_specifier_set_ls_type(ls, LS_IPV4);
    link_specifier_set_un_ipv4_addr(ls, tor_addr_to_ipv4h(&ei->addr));
    link_specifier_set_un_ipv4_port(ls, ei->port);
    /* Four bytes IPv4 and two bytes port. */
    link_specifier_set_ls_len(ls, sizeof(ei->addr.addr.in_addr) +
                              sizeof(ei->port));
    smartlist_add(lspecs, ls);
  
    /* Legacy ID is mandatory. */
    ls = link_specifier_new();
    link_specifier_set_ls_type(ls, LS_LEGACY_ID);
    memcpy(link_specifier_getarray_un_legacy_id(ls), ei->identity_digest,
           link_specifier_getlen_un_legacy_id(ls));
    link_specifier_set_ls_len(ls, link_specifier_getlen_un_legacy_id(ls));
    smartlist_add(lspecs, ls);
  
    /* ed25519 ID is only included if the extend_info has it. */
    if (!ed25519_public_key_is_zero(&ei->ed_identity)) {
      ls = link_specifier_new();
      link_specifier_set_ls_type(ls, LS_ED25519_ID);
      memcpy(link_specifier_getarray_un_ed25519_id(ls), &ei->ed_identity,
             link_specifier_getlen_un_ed25519_id(ls));
      link_specifier_set_ls_len(ls, link_specifier_getlen_un_ed25519_id(ls));
      smartlist_add(lspecs, ls);
    }
  }
  
  /* Using the given descriptor intro point ip, the extend information of the
   * rendezvous point rp_ei and the service's subcredential, populate the
   * already allocated intro1_data object with the needed key material and link
   * specifiers.
   *
   * This can't fail but the ip MUST be a valid object containing the needed
   * keys and authentication method. */
  static void
  setup_introduce1_data(const hs_desc_intro_point_t *ip,
                        const extend_info_t *rp_ei,
                        const uint8_t *subcredential,
                        hs_cell_introduce1_data_t *intro1_data)
  {
    smartlist_t *rp_lspecs;
  
    tor_assert(ip);
    tor_assert(rp_ei);
    tor_assert(subcredential);
    tor_assert(intro1_data);
  
    /* Build the link specifiers from the extend information of the rendezvous
     * circuit that we've picked previously. */
    rp_lspecs = smartlist_new();
    get_lspecs_from_extend_info(rp_ei, rp_lspecs);
  
    /* Populate the introduce1 data object. */
    memset(intro1_data, 0, sizeof(hs_cell_introduce1_data_t));
    if (ip->legacy.key != NULL) {
      intro1_data->is_legacy = 1;
      intro1_data->legacy_key = ip->legacy.key;
    }
    intro1_data->auth_pk = &ip->auth_key_cert->signed_key;
    intro1_data->enc_pk = &ip->enc_key;
    intro1_data->subcredential = subcredential;
    intro1_data->onion_pk = &rp_ei->curve25519_onion_key;
    intro1_data->link_specifiers = rp_lspecs;
  }
  
  /* ========== */
  /* Public API */
  /* ========== */
  
  /* Return an introduction point circuit matching the given intro point object.
   * NULL is returned is no such circuit can be found. */
  origin_circuit_t *
  hs_circ_service_get_intro_circ(const hs_service_intro_point_t *ip)
  {
    origin_circuit_t *circ = NULL;
  
    tor_assert(ip);
  
    if (ip->base.is_only_legacy) {
      uint8_t digest[DIGEST_LEN];
      if (BUG(crypto_pk_get_digest(ip->legacy_key, (char *) digest) < 0)) {
        goto end;
      }
      circ = hs_circuitmap_get_intro_circ_v2_service_side(digest);
    } else {
      circ = hs_circuitmap_get_intro_circ_v3_service_side(
                                          &ip->auth_key_kp.pubkey);
    }
   end:
    return circ;
  }
  
  /* Called when we fail building a rendezvous circuit at some point other than
   * the last hop: launches a new circuit to the same rendezvous point. This
   * supports legacy service.
   *
   * We currently relaunch connections to rendezvous points if:
   * - A rendezvous circuit timed out before connecting to RP.
   * - The redenzvous circuit failed to connect to the RP.
   *
   * We avoid relaunching a connection to this rendezvous point if:
   * - We have already tried MAX_REND_FAILURES times to connect to this RP.
   * - We've been trying to connect to this RP for more than MAX_REND_TIMEOUT
   *   seconds
   * - We've already retried this specific rendezvous circuit.
   */
  void
  hs_circ_retry_service_rendezvous_point(origin_circuit_t *circ)
  {
    tor_assert(circ);
    tor_assert(TO_CIRCUIT(circ)->purpose == CIRCUIT_PURPOSE_S_CONNECT_REND);
  
    /* Check if we are allowed to relaunch to the rendezvous point of circ. */
    if (!can_relaunch_service_rendezvous_point(circ)) {
      goto done;
    }
  
    /* Flag the circuit that we are relaunching so to avoid to relaunch twice a
     * circuit to the same rendezvous point at the same time. */
    circ->hs_service_side_rend_circ_has_been_relaunched = 1;
  
    /* Legacy service don't have an hidden service ident. */
    if (circ->hs_ident) {
      retry_service_rendezvous_point(circ);
    } else {
      rend_service_relaunch_rendezvous(circ);
    }
  
   done:
    return;
  }
  
  /* For a given service and a service intro point, launch a circuit to the
   * extend info ei. If the service is a single onion, a one-hop circuit will be
   * requested. Return 0 if the circuit was successfully launched and tagged
   * with the correct identifier. On error, a negative value is returned. */
  int
  hs_circ_launch_intro_point(hs_service_t *service,
                             const hs_service_intro_point_t *ip,
                             extend_info_t *ei)
  {
    /* Standard flags for introduction circuit. */
    int ret = -1, circ_flags = CIRCLAUNCH_NEED_UPTIME | CIRCLAUNCH_IS_INTERNAL;
    origin_circuit_t *circ;
  
    tor_assert(service);
    tor_assert(ip);
    tor_assert(ei);
  
    /* Update circuit flags in case of a single onion service that requires a
     * direct connection. */
    if (service->config.is_single_onion) {
      circ_flags |= CIRCLAUNCH_ONEHOP_TUNNEL;
    }
  
    log_info(LD_REND, "Launching a circuit to intro point %s for service %s.",
             safe_str_client(extend_info_describe(ei)),
             safe_str_client(service->onion_address));
  
    /* Note down the launch for the retry period. Even if the circuit fails to
     * be launched, we still want to respect the retry period to avoid stress on
     * the circuit subsystem. */
    service->state.num_intro_circ_launched++;
    circ = circuit_launch_by_extend_info(CIRCUIT_PURPOSE_S_ESTABLISH_INTRO,
                                         ei, circ_flags);
    if (circ == NULL) {
      goto end;
    }
  
    /* Setup the circuit identifier and attach it to it. */
    circ->hs_ident = create_intro_circuit_identifier(service, ip);
    tor_assert(circ->hs_ident);
    /* Register circuit in the global circuitmap. */
    register_intro_circ(ip, circ);
  
    /* Success. */
    ret = 0;
   end:
    return ret;
  }
  
  /* Called when a service introduction point circuit is done building. Given
   * the service and intro point object, this function will send the
   * ESTABLISH_INTRO cell on the circuit. Return 0 on success. Return 1 if the
   * circuit has been repurposed to General because we already have too many
   * opened. */
  int
  hs_circ_service_intro_has_opened(hs_service_t *service,
                                   hs_service_intro_point_t *ip,
                                   const hs_service_descriptor_t *desc,
                                   origin_circuit_t *circ)
  {
    int ret = 0;
    unsigned int num_intro_circ, num_needed_circ;
  
    tor_assert(service);
    tor_assert(ip);
    tor_assert(desc);
    tor_assert(circ);
  
    /* Cound opened circuits that have sent ESTABLISH_INTRO cells or are already
     * established introduction circuits */
    num_intro_circ = count_opened_desc_intro_point_circuits(service, desc);
    num_needed_circ = service->config.num_intro_points;
    if (num_intro_circ > num_needed_circ) {
      /* There are too many opened valid intro circuit for what the service
       * needs so repurpose this one. */
  
      /* XXX: Legacy code checks options->ExcludeNodes and if not NULL it just
       * closes the circuit. I have NO idea why it does that so it hasn't been
       * added here. I can only assume in case our ExcludeNodes list changes but
       * in that case, all circuit are flagged unusable (config.c). --dgoulet */
  
      log_info(LD_CIRC | LD_REND, "Introduction circuit just opened but we "
                                  "have enough for service %s. Repurposing "
                                  "it to general and leaving internal.",
               safe_str_client(service->onion_address));
      tor_assert(circ->build_state->is_internal);
      /* Remove it from the circuitmap. */
      hs_circuitmap_remove_circuit(TO_CIRCUIT(circ));
      /* Cleaning up the hidden service identifier and repurpose. */
      hs_ident_circuit_free(circ->hs_ident);
      circ->hs_ident = NULL;
      circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_C_GENERAL);
      /* Inform that this circuit just opened for this new purpose. */
      circuit_has_opened(circ);
      /* This return value indicate to the caller that the IP object should be
       * removed from the service because it's corresponding circuit has just
       * been repurposed. */
      ret = 1;
      goto done;
    }
  
    log_info(LD_REND, "Introduction circuit %u established for service %s.",
             TO_CIRCUIT(circ)->n_circ_id,
             safe_str_client(service->onion_address));
    circuit_log_path(LOG_INFO, LD_REND, circ);
  
    /* Time to send an ESTABLISH_INTRO cell on this circuit. On error, this call
     * makes sure the circuit gets closed. */
    send_establish_intro(service, ip, circ);
  
   done:
    return ret;
  }
  
  /* Called when a service rendezvous point circuit is done building. Given the
   * service and the circuit, this function will send a RENDEZVOUS1 cell on the
   * circuit using the information in the circuit identifier. If the cell can't
   * be sent, the circuit is closed. */
  void
  hs_circ_service_rp_has_opened(const hs_service_t *service,
                                origin_circuit_t *circ)
  {
    size_t payload_len;
    uint8_t payload[RELAY_PAYLOAD_SIZE] = {0};
  
    tor_assert(service);
    tor_assert(circ);
    tor_assert(circ->hs_ident);
  
    /* Some useful logging. */
    log_info(LD_REND, "Rendezvous circuit %u has opened with cookie %s "
                      "for service %s",
             TO_CIRCUIT(circ)->n_circ_id,
             hex_str((const char *) circ->hs_ident->rendezvous_cookie,
                     REND_COOKIE_LEN),
             safe_str_client(service->onion_address));
    circuit_log_path(LOG_INFO, LD_REND, circ);
  
    /* This can't fail. */
    payload_len = hs_cell_build_rendezvous1(
                          circ->hs_ident->rendezvous_cookie,
                          sizeof(circ->hs_ident->rendezvous_cookie),
                          circ->hs_ident->rendezvous_handshake_info,
                          sizeof(circ->hs_ident->rendezvous_handshake_info),
                          payload);
  
    /* Pad the payload with random bytes so it matches the size of a legacy cell
     * which is normally always bigger. Also, the size of a legacy cell is
     * always smaller than the RELAY_PAYLOAD_SIZE so this is safe. */
    if (payload_len < HS_LEGACY_RENDEZVOUS_CELL_SIZE) {
      crypto_rand((char *) payload + payload_len,
                  HS_LEGACY_RENDEZVOUS_CELL_SIZE - payload_len);
      payload_len = HS_LEGACY_RENDEZVOUS_CELL_SIZE;
    }
  
    if (relay_send_command_from_edge(CONTROL_CELL_ID, TO_CIRCUIT(circ),
                                     RELAY_COMMAND_RENDEZVOUS1,
                                     (const char *) payload, payload_len,
                                     circ->cpath->prev) < 0) {
      /* On error, circuit is closed. */
      log_warn(LD_REND, "Unable to send RENDEZVOUS1 cell on circuit %u "
                        "for service %s",
               TO_CIRCUIT(circ)->n_circ_id,
               safe_str_client(service->onion_address));
      goto done;
    }
  
    /* Setup end-to-end rendezvous circuit between the client and us. */
    if (hs_circuit_setup_e2e_rend_circ(circ,
                         circ->hs_ident->rendezvous_ntor_key_seed,
                         sizeof(circ->hs_ident->rendezvous_ntor_key_seed),
                         1) < 0) {
      log_warn(LD_GENERAL, "Failed to setup circ");
      goto done;
    }
  
   done:
    memwipe(payload, 0, sizeof(payload));
  }
  
  /* Circ has been expecting an INTRO_ESTABLISHED cell that just arrived. Handle
   * the INTRO_ESTABLISHED cell payload of length payload_len arriving on the
   * given introduction circuit circ. The service is only used for logging
   * purposes. Return 0 on success else a negative value. */
  int
  hs_circ_handle_intro_established(const hs_service_t *service,
                                   const hs_service_intro_point_t *ip,
                                   origin_circuit_t *circ,
                                   const uint8_t *payload, size_t payload_len)
  {
    int ret = -1;
  
    tor_assert(service);
    tor_assert(ip);
    tor_assert(circ);
    tor_assert(payload);
  
    if (BUG(TO_CIRCUIT(circ)->purpose != CIRCUIT_PURPOSE_S_ESTABLISH_INTRO)) {
      goto done;
    }
  
    /* Try to parse the payload into a cell making sure we do actually have a
     * valid cell. For a legacy node, it's an empty payload so as long as we
     * have the cell, we are good. */
    if (!ip->base.is_only_legacy &&
        hs_cell_parse_intro_established(payload, payload_len) < 0) {
      log_warn(LD_REND, "Unable to parse the INTRO_ESTABLISHED cell on "
                        "circuit %u for service %s",
               TO_CIRCUIT(circ)->n_circ_id,
               safe_str_client(service->onion_address));
      goto done;
    }
  
    /* Switch the purpose to a fully working intro point. */
    circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_S_INTRO);
    /* Getting a valid INTRODUCE_ESTABLISHED means we've successfully used the
     * circuit so update our pathbias subsystem. */
    pathbias_mark_use_success(circ);
    /* Success. */
    ret = 0;
  
   done:
    return ret;
  }
  
  /* We just received an INTRODUCE2 cell on the established introduction circuit
   * circ.  Handle the INTRODUCE2 payload of size payload_len for the given
   * circuit and service. This cell is associated with the intro point object ip
   * and the subcredential. Return 0 on success else a negative value. */
  int
  hs_circ_handle_introduce2(const hs_service_t *service,
                            const origin_circuit_t *circ,
                            hs_service_intro_point_t *ip,
                            const uint8_t *subcredential,
                            const uint8_t *payload, size_t payload_len)
  {
    int ret = -1;
    time_t elapsed;
    hs_cell_introduce2_data_t data;
  
    tor_assert(service);
    tor_assert(circ);
    tor_assert(ip);
    tor_assert(subcredential);
    tor_assert(payload);
  
    /* Populate the data structure with everything we need for the cell to be
     * parsed, decrypted and key material computed correctly. */
    data.auth_pk = &ip->auth_key_kp.pubkey;
    data.enc_kp = &ip->enc_key_kp;
    data.subcredential = subcredential;
    data.payload = payload;
    data.payload_len = payload_len;
    data.link_specifiers = smartlist_new();
    data.replay_cache = ip->replay_cache;
  
    if (hs_cell_parse_introduce2(&data, circ, service) < 0) {
      goto done;
    }
  
    /* Check whether we've seen this REND_COOKIE before to detect repeats. */
    if (replaycache_add_test_and_elapsed(
             service->state.replay_cache_rend_cookie,
             data.rendezvous_cookie, sizeof(data.rendezvous_cookie),
             &elapsed)) {
      /* A Tor client will send a new INTRODUCE1 cell with the same REND_COOKIE
       * as its previous one if its intro circ times out while in state
       * CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT. If we received the first
       * INTRODUCE1 cell (the intro-point relay converts it into an INTRODUCE2
       * cell), we are already trying to connect to that rend point (and may
       * have already succeeded); drop this cell. */
      log_info(LD_REND, "We received an INTRODUCE2 cell with same REND_COOKIE "
                        "field %ld seconds ago. Dropping cell.",
               (long int) elapsed);
      goto done;
    }
  
    /* At this point, we just confirmed that the full INTRODUCE2 cell is valid
     * so increment our counter that we've seen one on this intro point. */
    ip->introduce2_count++;
  
    /* Launch rendezvous circuit with the onion key and rend cookie. */
    launch_rendezvous_point_circuit(service, ip, &data);
    /* Success. */
    ret = 0;
  
   done:
    SMARTLIST_FOREACH(data.link_specifiers, link_specifier_t *, lspec,
                      link_specifier_free(lspec));
    smartlist_free(data.link_specifiers);
    memwipe(&data, 0, sizeof(data));
    return ret;
  }
  
  /* Circuit <b>circ</b> just finished the rend ntor key exchange. Use the key
   * exchange output material at <b>ntor_key_seed</b> and setup <b>circ</b> to
   * serve as a rendezvous end-to-end circuit between the client and the
   * service. If <b>is_service_side</b> is set, then we are the hidden service
   * and the other side is the client.
   *
   * Return 0 if the operation went well; in case of error return -1. */
  int
  hs_circuit_setup_e2e_rend_circ(origin_circuit_t *circ,
                                 const uint8_t *ntor_key_seed, size_t seed_len,
                                 int is_service_side)
  {
    if (BUG(!circuit_purpose_is_correct_for_rend(TO_CIRCUIT(circ)->purpose,
                                          is_service_side))) {
      return -1;
    }
  
    crypt_path_t *hop = create_rend_cpath(ntor_key_seed, seed_len,
                                          is_service_side);
    if (!hop) {
      log_warn(LD_REND, "Couldn't get v3 %s cpath!",
               is_service_side ? "service-side" : "client-side");
      return -1;
    }
  
    finalize_rend_circuit(circ, hop, is_service_side);
  
    return 0;
  }
  
  /* We are a v2 legacy HS client and we just received a RENDEZVOUS1 cell
   * <b>rend_cell_body</b> on <b>circ</b>. Finish up the DH key exchange and then
   * extend the crypt path of <b>circ</b> so that the hidden service is on the
   * other side. */
  int
  hs_circuit_setup_e2e_rend_circ_legacy_client(origin_circuit_t *circ,
                                               const uint8_t *rend_cell_body)
  {
  
    if (BUG(!circuit_purpose_is_correct_for_rend(
                                        TO_CIRCUIT(circ)->purpose, 0))) {
      return -1;
    }
  
    crypt_path_t *hop = create_rend_cpath_legacy(circ, rend_cell_body);
    if (!hop) {
      log_warn(LD_GENERAL, "Couldn't get v2 cpath.");
      return -1;
    }
  
    finalize_rend_circuit(circ, hop, 0);
  
    return 0;
  }
  
  /* Given the introduction circuit intro_circ, the rendezvous circuit
   * rend_circ, a descriptor intro point object ip and the service's
   * subcredential, send an INTRODUCE1 cell on intro_circ.
   *
   * This will also setup the circuit identifier on rend_circ containing the key
   * material for the handshake and e2e encryption. Return 0 on success else
   * negative value. Because relay_send_command_from_edge() closes the circuit
   * on error, it is possible that intro_circ is closed on error. */
  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 ret = -1;
    ssize_t payload_len;
    uint8_t payload[RELAY_PAYLOAD_SIZE] = {0};
    hs_cell_introduce1_data_t intro1_data;
  
    tor_assert(intro_circ);
    tor_assert(rend_circ);
    tor_assert(ip);
    tor_assert(subcredential);
  
    /* This takes various objects in order to populate the introduce1 data
     * object which is used to build the content of the cell. */
    setup_introduce1_data(ip, rend_circ->build_state->chosen_exit,
                          subcredential, &intro1_data);
    /* If we didn't get any link specifiers, it's because our extend info was
     * bad. */
    if (BUG(!intro1_data.link_specifiers) ||
        !smartlist_len(intro1_data.link_specifiers)) {
      log_warn(LD_REND, "Unable to get link specifiers for INTRODUCE1 cell on "
               "circuit %u.", TO_CIRCUIT(intro_circ)->n_circ_id);
      goto done;
    }
  
    /* Final step before we encode a cell, we setup the circuit identifier which
     * will generate both the rendezvous cookie and client keypair for this
     * connection. Those are put in the ident. */
    intro1_data.rendezvous_cookie = rend_circ->hs_ident->rendezvous_cookie;
    intro1_data.client_kp = &rend_circ->hs_ident->rendezvous_client_kp;
  
    memcpy(intro_circ->hs_ident->rendezvous_cookie,
           rend_circ->hs_ident->rendezvous_cookie,
           sizeof(intro_circ->hs_ident->rendezvous_cookie));
  
    /* From the introduce1 data object, this will encode the INTRODUCE1 cell
     * into payload which is then ready to be sent as is. */
    payload_len = hs_cell_build_introduce1(&intro1_data, payload);
    if (BUG(payload_len < 0)) {
      goto done;
    }
  
    if (relay_send_command_from_edge(CONTROL_CELL_ID, TO_CIRCUIT(intro_circ),
                                     RELAY_COMMAND_INTRODUCE1,
                                     (const char *) payload, payload_len,
                                     intro_circ->cpath->prev) < 0) {
      /* On error, circuit is closed. */
      log_warn(LD_REND, "Unable to send INTRODUCE1 cell on circuit %u.",
               TO_CIRCUIT(intro_circ)->n_circ_id);
      goto done;
    }
  
    /* Success. */
    ret = 0;
    goto done;
  
   done:
    hs_cell_introduce1_data_clear(&intro1_data);
    memwipe(payload, 0, sizeof(payload));
    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;
  }
  
  /* We are about to close or free this <b>circ</b>. Clean it up from any
   * related HS data structures. This function can be called multiple times
   * safely for the same circuit. */
  void
  hs_circ_cleanup(circuit_t *circ)
  {
    tor_assert(circ);
  
    /* If it's a service-side intro circ, notify the HS subsystem for the intro
     * point circuit closing so it can be dealt with cleanly. */
    if (circ->purpose == CIRCUIT_PURPOSE_S_ESTABLISH_INTRO ||
        circ->purpose == CIRCUIT_PURPOSE_S_INTRO) {
      hs_service_intro_circ_has_closed(TO_ORIGIN_CIRCUIT(circ));
    }
  
    /* Clear HS circuitmap token for this circ (if any). Very important to be
     * done after the HS subsystem has been notified of the close else the
     * circuit will not be found.
     *
     * We do this at the close if possible because from that point on, the
     * circuit is good as dead. We can't rely on removing it in the circuit
     * free() function because we open a race window between the close and free
     * where we can't register a new circuit for the same intro point. */
    if (circ->hs_token) {
      hs_circuitmap_remove_circuit(circ);
    }
  }
  
  