text: /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   * Copyright (c) 2007-2017, The Tor Project, Inc. */
  /* See LICENSE for licensing information */
  
  /**
   * \file rendcommon.c
   * \brief Rendezvous implementation: shared code between
   * introducers, services, clients, and rendezvous points.
   **/
  
  #include "or.h"
  #include "circuitbuild.h"
  #include "config.h"
  #include "control.h"
  #include "hs_common.h"
  #include "rendclient.h"
  #include "rendcommon.h"
  #include "rendmid.h"
  #include "hs_intropoint.h"
  #include "rendservice.h"
  #include "rephist.h"
  #include "router.h"
  #include "routerlist.h"
  #include "routerparse.h"
  #include "networkstatus.h"
  
  /** Return 0 if one and two are the same service ids, else -1 or 1 */
  int
  rend_cmp_service_ids(const char *one, const char *two)
  {
    return strcasecmp(one,two);
  }
  
  /** Free the storage held by the service descriptor <b>desc</b>.
   */
  void
  rend_service_descriptor_free(rend_service_descriptor_t *desc)
  {
    if (!desc)
      return;
    if (desc->pk)
      crypto_pk_free(desc->pk);
    if (desc->intro_nodes) {
      SMARTLIST_FOREACH(desc->intro_nodes, rend_intro_point_t *, intro,
        rend_intro_point_free(intro););
      smartlist_free(desc->intro_nodes);
    }
    if (desc->successful_uploads) {
      SMARTLIST_FOREACH(desc->successful_uploads, char *, c, tor_free(c););
      smartlist_free(desc->successful_uploads);
    }
    tor_free(desc);
  }
  
  /** Length of the descriptor cookie that is used for versioned hidden
   * service descriptors. */
  #define REND_DESC_COOKIE_LEN 16
  
  /** Length of the replica number that is used to determine the secret ID
   * part of versioned hidden service descriptors. */
  #define REND_REPLICA_LEN 1
  
  /** Compute the descriptor ID for <b>service_id</b> of length
   * <b>REND_SERVICE_ID_LEN</b> and <b>secret_id_part</b> of length
   * <b>DIGEST_LEN</b>, and write it to <b>descriptor_id_out</b> of length
   * <b>DIGEST_LEN</b>. */
  void
  rend_get_descriptor_id_bytes(char *descriptor_id_out,
                               const char *service_id,
                               const char *secret_id_part)
  {
    crypto_digest_t *digest = crypto_digest_new();
    crypto_digest_add_bytes(digest, service_id, REND_SERVICE_ID_LEN);
    crypto_digest_add_bytes(digest, secret_id_part, DIGEST_LEN);
    crypto_digest_get_digest(digest, descriptor_id_out, DIGEST_LEN);
    crypto_digest_free(digest);
  }
  
  /** Compute the secret ID part for time_period,
   * a <b>descriptor_cookie</b> of length
   * <b>REND_DESC_COOKIE_LEN</b> which may also be <b>NULL</b> if no
   * descriptor_cookie shall be used, and <b>replica</b>, and write it to
   * <b>secret_id_part</b> of length DIGEST_LEN. */
  static void
  get_secret_id_part_bytes(char *secret_id_part, uint32_t time_period,
                           const char *descriptor_cookie, uint8_t replica)
  {
    crypto_digest_t *digest = crypto_digest_new();
    time_period = htonl(time_period);
    crypto_digest_add_bytes(digest, (char*)&time_period, sizeof(uint32_t));
    if (descriptor_cookie) {
      crypto_digest_add_bytes(digest, descriptor_cookie,
                              REND_DESC_COOKIE_LEN);
    }
    crypto_digest_add_bytes(digest, (const char *)&replica, REND_REPLICA_LEN);
    crypto_digest_get_digest(digest, secret_id_part, DIGEST_LEN);
    crypto_digest_free(digest);
  }
  
  /** Return the time period for time <b>now</b> plus a potentially
   * intended <b>deviation</b> of one or more periods, based on the first byte
   * of <b>service_id</b>. */
  static uint32_t
  get_time_period(time_t now, uint8_t deviation, const char *service_id)
  {
    /* The time period is the number of REND_TIME_PERIOD_V2_DESC_VALIDITY
     * intervals that have passed since the epoch, offset slightly so that
     * each service's time periods start and end at a fraction of that
     * period based on their first byte. */
    return (uint32_t)
      (now + ((uint8_t) *service_id) * REND_TIME_PERIOD_V2_DESC_VALIDITY / 256)
      / REND_TIME_PERIOD_V2_DESC_VALIDITY + deviation;
  }
  
  /** Compute the time in seconds that a descriptor that is generated
   * <b>now</b> for <b>service_id</b> will be valid. */
  static uint32_t
  get_seconds_valid(time_t now, const char *service_id)
  {
    uint32_t result = REND_TIME_PERIOD_V2_DESC_VALIDITY -
      ((uint32_t)
       (now + ((uint8_t) *service_id) * REND_TIME_PERIOD_V2_DESC_VALIDITY / 256)
       % REND_TIME_PERIOD_V2_DESC_VALIDITY);
    return result;
  }
  
  /** Compute the binary <b>desc_id_out</b> (DIGEST_LEN bytes long) for a given
   * base32-encoded <b>service_id</b> and optional unencoded
   * <b>descriptor_cookie</b> of length REND_DESC_COOKIE_LEN,
   * at time <b>now</b> for replica number
   * <b>replica</b>. <b>desc_id</b> needs to have <b>DIGEST_LEN</b> bytes
   * free. Return 0 for success, -1 otherwise. */
  int
  rend_compute_v2_desc_id(char *desc_id_out, const char *service_id,
                          const char *descriptor_cookie, time_t now,
                          uint8_t replica)
  {
    char service_id_binary[REND_SERVICE_ID_LEN];
    char secret_id_part[DIGEST_LEN];
    uint32_t time_period;
    if (!service_id ||
        strlen(service_id) != REND_SERVICE_ID_LEN_BASE32) {
      log_warn(LD_REND, "Could not compute v2 descriptor ID: "
                        "Illegal service ID: %s",
               safe_str(service_id));
      return -1;
    }
    if (replica >= REND_NUMBER_OF_NON_CONSECUTIVE_REPLICAS) {
      log_warn(LD_REND, "Could not compute v2 descriptor ID: "
                        "Replica number out of range: %d", replica);
      return -1;
    }
    /* Convert service ID to binary. */
    if (base32_decode(service_id_binary, REND_SERVICE_ID_LEN,
                      service_id, REND_SERVICE_ID_LEN_BASE32) < 0) {
      log_warn(LD_REND, "Could not compute v2 descriptor ID: "
                        "Illegal characters in service ID: %s",
               safe_str_client(service_id));
      return -1;
    }
    /* Calculate current time-period. */
    time_period = get_time_period(now, 0, service_id_binary);
    /* Calculate secret-id-part = h(time-period | desc-cookie | replica). */
    get_secret_id_part_bytes(secret_id_part, time_period, descriptor_cookie,
                             replica);
    /* Calculate descriptor ID: H(permanent-id | secret-id-part) */
    rend_get_descriptor_id_bytes(desc_id_out, service_id_binary, secret_id_part);
    return 0;
  }
  
  /** Encode the introduction points in <b>desc</b> and write the result to a
   * newly allocated string pointed to by <b>encoded</b>. Return 0 for
   * success, -1 otherwise. */
  static int
  rend_encode_v2_intro_points(char **encoded, rend_service_descriptor_t *desc)
  {
    size_t unenc_len;
    char *unenc = NULL;
    size_t unenc_written = 0;
    int i;
    int r = -1;
    /* Assemble unencrypted list of introduction points. */
    unenc_len = smartlist_len(desc->intro_nodes) * 1000; /* too long, but ok. */
    unenc = tor_malloc_zero(unenc_len);
    for (i = 0; i < smartlist_len(desc->intro_nodes); i++) {
      char id_base32[REND_INTRO_POINT_ID_LEN_BASE32 + 1];
      char *onion_key = NULL;
      size_t onion_key_len;
      crypto_pk_t *intro_key;
      char *service_key = NULL;
      char *address = NULL;
      size_t service_key_len;
      int res;
      rend_intro_point_t *intro = smartlist_get(desc->intro_nodes, i);
      /* Obtain extend info with introduction point details. */
      extend_info_t *info = intro->extend_info;
      /* Encode introduction point ID. */
      base32_encode(id_base32, sizeof(id_base32),
                    info->identity_digest, DIGEST_LEN);
      /* Encode onion key. */
      if (crypto_pk_write_public_key_to_string(info->onion_key, &onion_key,
                                               &onion_key_len) < 0) {
        log_warn(LD_REND, "Could not write onion key.");
        goto done;
      }
      /* Encode intro key. */
      intro_key = intro->intro_key;
      if (!intro_key ||
        crypto_pk_write_public_key_to_string(intro_key, &service_key,
                                             &service_key_len) < 0) {
        log_warn(LD_REND, "Could not write intro key.");
        tor_free(onion_key);
        goto done;
      }
      /* Assemble everything for this introduction point. */
      address = tor_addr_to_str_dup(&info->addr);
      res = tor_snprintf(unenc + unenc_written, unenc_len - unenc_written,
                           "introduction-point %s\n"
                           "ip-address %s\n"
                           "onion-port %d\n"
                           "onion-key\n%s"
                           "service-key\n%s",
                         id_base32,
                         address,
                         info->port,
                         onion_key,
                         service_key);
      tor_free(address);
      tor_free(onion_key);
      tor_free(service_key);
      if (res < 0) {
        log_warn(LD_REND, "Not enough space for writing introduction point "
                          "string.");
        goto done;
      }
      /* Update total number of written bytes for unencrypted intro points. */
      unenc_written += res;
    }
    /* Finalize unencrypted introduction points. */
    if (unenc_len < unenc_written + 2) {
      log_warn(LD_REND, "Not enough space for finalizing introduction point "
                        "string.");
      goto done;
    }
    unenc[unenc_written++] = '\n';
    unenc[unenc_written++] = 0;
    *encoded = unenc;
    r = 0;
   done:
    if (r<0)
      tor_free(unenc);
    return r;
  }
  
  /** Encrypt the encoded introduction points in <b>encoded</b> using
   * authorization type  'basic' with <b>client_cookies</b> and write the
   * result to a newly allocated string pointed to by <b>encrypted_out</b> of
   * length <b>encrypted_len_out</b>. Return 0 for success, -1 otherwise. */
  static int
  rend_encrypt_v2_intro_points_basic(char **encrypted_out,
                                     size_t *encrypted_len_out,
                                     const char *encoded,
                                     smartlist_t *client_cookies)
  {
    int r = -1, i, pos, enclen, client_blocks;
    size_t len, client_entries_len;
    char *enc = NULL, iv[CIPHER_IV_LEN], *client_part = NULL,
         session_key[CIPHER_KEY_LEN];
    smartlist_t *encrypted_session_keys = NULL;
    crypto_digest_t *digest;
    crypto_cipher_t *cipher;
    tor_assert(encoded);
    tor_assert(client_cookies && smartlist_len(client_cookies) > 0);
  
    /* Generate session key. */
    crypto_rand(session_key, CIPHER_KEY_LEN);
  
    /* Determine length of encrypted introduction points including session
     * keys. */
    client_blocks = 1 + ((smartlist_len(client_cookies) - 1) /
                         REND_BASIC_AUTH_CLIENT_MULTIPLE);
    client_entries_len = client_blocks * REND_BASIC_AUTH_CLIENT_MULTIPLE *
                         REND_BASIC_AUTH_CLIENT_ENTRY_LEN;
    len = 2 + client_entries_len + CIPHER_IV_LEN + strlen(encoded);
    if (client_blocks >= 256) {
      log_warn(LD_REND, "Too many clients in introduction point string.");
      goto done;
    }
    enc = tor_malloc_zero(len);
    enc[0] = 0x01; /* type of authorization. */
    enc[1] = (uint8_t)client_blocks;
  
    /* Encrypt with random session key. */
    enclen = crypto_cipher_encrypt_with_iv(session_key,
        enc + 2 + client_entries_len,
        CIPHER_IV_LEN + strlen(encoded), encoded, strlen(encoded));
  
    if (enclen < 0) {
      log_warn(LD_REND, "Could not encrypt introduction point string.");
      goto done;
    }
    memcpy(iv, enc + 2 + client_entries_len, CIPHER_IV_LEN);
  
    /* Encrypt session key for cookies, determine client IDs, and put both
     * in a smartlist. */
    encrypted_session_keys = smartlist_new();
    SMARTLIST_FOREACH_BEGIN(client_cookies, const char *, cookie) {
      client_part = tor_malloc_zero(REND_BASIC_AUTH_CLIENT_ENTRY_LEN);
      /* Encrypt session key. */
      cipher = crypto_cipher_new(cookie);
      if (crypto_cipher_encrypt(cipher, client_part +
                                    REND_BASIC_AUTH_CLIENT_ID_LEN,
                                session_key, CIPHER_KEY_LEN) < 0) {
        log_warn(LD_REND, "Could not encrypt session key for client.");
        crypto_cipher_free(cipher);
        tor_free(client_part);
        goto done;
      }
      crypto_cipher_free(cipher);
  
      /* Determine client ID. */
      digest = crypto_digest_new();
      crypto_digest_add_bytes(digest, cookie, REND_DESC_COOKIE_LEN);
      crypto_digest_add_bytes(digest, iv, CIPHER_IV_LEN);
      crypto_digest_get_digest(digest, client_part,
                               REND_BASIC_AUTH_CLIENT_ID_LEN);
      crypto_digest_free(digest);
  
      /* Put both together. */
      smartlist_add(encrypted_session_keys, client_part);
    } SMARTLIST_FOREACH_END(cookie);
  
    /* Add some fake client IDs and encrypted session keys. */
    for (i = (smartlist_len(client_cookies) - 1) %
             REND_BASIC_AUTH_CLIENT_MULTIPLE;
         i < REND_BASIC_AUTH_CLIENT_MULTIPLE - 1; i++) {
      client_part = tor_malloc_zero(REND_BASIC_AUTH_CLIENT_ENTRY_LEN);
      crypto_rand(client_part, REND_BASIC_AUTH_CLIENT_ENTRY_LEN);
      smartlist_add(encrypted_session_keys, client_part);
    }
    /* Sort smartlist and put elements in result in order. */
    smartlist_sort_digests(encrypted_session_keys);
    pos = 2;
    SMARTLIST_FOREACH(encrypted_session_keys, const char *, entry, {
      memcpy(enc + pos, entry, REND_BASIC_AUTH_CLIENT_ENTRY_LEN);
      pos += REND_BASIC_AUTH_CLIENT_ENTRY_LEN;
    });
    *encrypted_out = enc;
    *encrypted_len_out = len;
    enc = NULL; /* prevent free. */
    r = 0;
   done:
    tor_free(enc);
    if (encrypted_session_keys) {
      SMARTLIST_FOREACH(encrypted_session_keys, char *, d, tor_free(d););
      smartlist_free(encrypted_session_keys);
    }
    return r;
  }
  
  /** Encrypt the encoded introduction points in <b>encoded</b> using
   * authorization type 'stealth' with <b>descriptor_cookie</b> of length
   * REND_DESC_COOKIE_LEN and write the result to a newly allocated string
   * pointed to by <b>encrypted_out</b> of length <b>encrypted_len_out</b>.
   * Return 0 for success, -1 otherwise. */
  static int
  rend_encrypt_v2_intro_points_stealth(char **encrypted_out,
                                       size_t *encrypted_len_out,
                                       const char *encoded,
                                       const char *descriptor_cookie)
  {
    int r = -1, enclen;
    char *enc;
    tor_assert(encoded);
    tor_assert(descriptor_cookie);
  
    enc = tor_malloc_zero(1 + CIPHER_IV_LEN + strlen(encoded));
    enc[0] = 0x02; /* Auth type */
    enclen = crypto_cipher_encrypt_with_iv(descriptor_cookie,
                                           enc + 1,
                                           CIPHER_IV_LEN+strlen(encoded),
                                           encoded, strlen(encoded));
    if (enclen < 0) {
      log_warn(LD_REND, "Could not encrypt introduction point string.");
      goto done;
    }
    *encrypted_out = enc;
    *encrypted_len_out = enclen;
    enc = NULL; /* prevent free */
    r = 0;
   done:
    tor_free(enc);
    return r;
  }
  
  /** Attempt to parse the given <b>desc_str</b> and return true if this
   * succeeds, false otherwise. */
  static int
  rend_desc_v2_is_parsable(rend_encoded_v2_service_descriptor_t *desc)
  {
    rend_service_descriptor_t *test_parsed = NULL;
    char test_desc_id[DIGEST_LEN];
    char *test_intro_content = NULL;
    size_t test_intro_size;
    size_t test_encoded_size;
    const char *test_next;
    int res = rend_parse_v2_service_descriptor(&test_parsed, test_desc_id,
                                           &test_intro_content,
                                           &test_intro_size,
                                           &test_encoded_size,
                                           &test_next, desc->desc_str, 1);
    rend_service_descriptor_free(test_parsed);
    tor_free(test_intro_content);
    return (res >= 0);
  }
  
  /** Free the storage held by an encoded v2 service descriptor. */
  void
  rend_encoded_v2_service_descriptor_free(
    rend_encoded_v2_service_descriptor_t *desc)
  {
    if (!desc)
      return;
    tor_free(desc->desc_str);
    tor_free(desc);
  }
  
  /** Free the storage held by an introduction point info. */
  void
  rend_intro_point_free(rend_intro_point_t *intro)
  {
    if (!intro)
      return;
  
    extend_info_free(intro->extend_info);
    crypto_pk_free(intro->intro_key);
  
    if (intro->accepted_intro_rsa_parts != NULL) {
      replaycache_free(intro->accepted_intro_rsa_parts);
    }
  
    tor_free(intro);
  }
  
  /** Encode a set of rend_encoded_v2_service_descriptor_t's for <b>desc</b>
   * at time <b>now</b> using <b>service_key</b>, depending on
   * <b>auth_type</b> a <b>descriptor_cookie</b> and a list of
   * <b>client_cookies</b> (which are both <b>NULL</b> if no client
   * authorization is performed), and <b>period</b> (e.g. 0 for the current
   * period, 1 for the next period, etc.) and add them to the existing list
   * <b>descs_out</b>; return the number of seconds that the descriptors will
   * be found by clients, or -1 if the encoding was not successful. */
  int
  rend_encode_v2_descriptors(smartlist_t *descs_out,
                             rend_service_descriptor_t *desc, time_t now,
                             uint8_t period, rend_auth_type_t auth_type,
                             crypto_pk_t *client_key,
                             smartlist_t *client_cookies)
  {
    char service_id[DIGEST_LEN];
    char service_id_base32[REND_SERVICE_ID_LEN_BASE32+1];
    uint32_t time_period;
    char *ipos_base64 = NULL, *ipos = NULL, *ipos_encrypted = NULL,
         *descriptor_cookie = NULL;
    size_t ipos_len = 0, ipos_encrypted_len = 0;
    int k;
    uint32_t seconds_valid;
    crypto_pk_t *service_key;
    if (!desc) {
      log_warn(LD_BUG, "Could not encode v2 descriptor: No desc given.");
      return -1;
    }
    service_key = (auth_type == REND_STEALTH_AUTH) ? client_key : desc->pk;
    tor_assert(service_key);
    if (auth_type == REND_STEALTH_AUTH) {
      descriptor_cookie = smartlist_get(client_cookies, 0);
      tor_assert(descriptor_cookie);
    }
    /* Obtain service_id from public key. */
    if (crypto_pk_get_digest(service_key, service_id) < 0) {
      log_warn(LD_BUG, "Couldn't compute service key digest.");
      return -1;
    }
    /* Calculate current time-period. */
    time_period = get_time_period(now, period, service_id);
    /* Determine how many seconds the descriptor will be valid. */
    seconds_valid = period * REND_TIME_PERIOD_V2_DESC_VALIDITY +
                    get_seconds_valid(now, service_id);
    /* Assemble, possibly encrypt, and encode introduction points. */
    if (smartlist_len(desc->intro_nodes) > 0) {
      if (rend_encode_v2_intro_points(&ipos, desc) < 0) {
        log_warn(LD_REND, "Encoding of introduction points did not succeed.");
        return -1;
      }
      switch (auth_type) {
        case REND_NO_AUTH:
          ipos_len = strlen(ipos);
          break;
        case REND_BASIC_AUTH:
          if (rend_encrypt_v2_intro_points_basic(&ipos_encrypted,
                                                 &ipos_encrypted_len, ipos,
                                                 client_cookies) < 0) {
            log_warn(LD_REND, "Encrypting of introduction points did not "
                              "succeed.");
            tor_free(ipos);
            return -1;
          }
          tor_free(ipos);
          ipos = ipos_encrypted;
          ipos_len = ipos_encrypted_len;
          break;
        case REND_STEALTH_AUTH:
          if (rend_encrypt_v2_intro_points_stealth(&ipos_encrypted,
                                                   &ipos_encrypted_len, ipos,
                                                   descriptor_cookie) < 0) {
            log_warn(LD_REND, "Encrypting of introduction points did not "
                              "succeed.");
            tor_free(ipos);
            return -1;
          }
          tor_free(ipos);
          ipos = ipos_encrypted;
          ipos_len = ipos_encrypted_len;
          break;
        default:
          log_warn(LD_REND|LD_BUG, "Unrecognized authorization type %d",
                   (int)auth_type);
          tor_free(ipos);
          return -1;
      }
      /* Base64-encode introduction points. */
      ipos_base64 = tor_calloc(ipos_len, 2);
      if (base64_encode(ipos_base64, ipos_len * 2, ipos, ipos_len,
                        BASE64_ENCODE_MULTILINE)<0) {
        log_warn(LD_REND, "Could not encode introduction point string to "
                 "base64. length=%d", (int)ipos_len);
        tor_free(ipos_base64);
        tor_free(ipos);
        return -1;
      }
      tor_free(ipos);
    }
    /* Encode REND_NUMBER_OF_NON_CONSECUTIVE_REPLICAS descriptors. */
    for (k = 0; k < REND_NUMBER_OF_NON_CONSECUTIVE_REPLICAS; k++) {
      char secret_id_part[DIGEST_LEN];
      char secret_id_part_base32[REND_SECRET_ID_PART_LEN_BASE32 + 1];
      char desc_id_base32[REND_DESC_ID_V2_LEN_BASE32 + 1];
      char *permanent_key = NULL;
      size_t permanent_key_len;
      char published[ISO_TIME_LEN+1];
      int i;
      char protocol_versions_string[16]; /* max len: "0,1,2,3,4,5,6,7\0" */
      size_t protocol_versions_written;
      size_t desc_len;
      char *desc_str = NULL;
      int result = 0;
      size_t written = 0;
      char desc_digest[DIGEST_LEN];
      rend_encoded_v2_service_descriptor_t *enc =
        tor_malloc_zero(sizeof(rend_encoded_v2_service_descriptor_t));
      /* Calculate secret-id-part = h(time-period | cookie | replica). */
      get_secret_id_part_bytes(secret_id_part, time_period, descriptor_cookie,
                               k);
      base32_encode(secret_id_part_base32, sizeof(secret_id_part_base32),
                    secret_id_part, DIGEST_LEN);
      /* Calculate descriptor ID. */
      rend_get_descriptor_id_bytes(enc->desc_id, service_id, secret_id_part);
      base32_encode(desc_id_base32, sizeof(desc_id_base32),
                    enc->desc_id, DIGEST_LEN);
      /* PEM-encode the public key */
      if (crypto_pk_write_public_key_to_string(service_key, &permanent_key,
                                               &permanent_key_len) < 0) {
        log_warn(LD_BUG, "Could not write public key to string.");
        rend_encoded_v2_service_descriptor_free(enc);
        goto err;
      }
      /* Encode timestamp. */
      format_iso_time(published, desc->timestamp);
      /* Write protocol-versions bitmask to comma-separated value string. */
      protocol_versions_written = 0;
      for (i = 0; i < 8; i++) {
        if (desc->protocols & 1 << i) {
          tor_snprintf(protocol_versions_string + protocol_versions_written,
                       16 - protocol_versions_written, "%d,", i);
          protocol_versions_written += 2;
        }
      }
      if (protocol_versions_written)
        protocol_versions_string[protocol_versions_written - 1] = '\0';
      else
        protocol_versions_string[0]= '\0';
      /* Assemble complete descriptor. */
      desc_len = 2000 + smartlist_len(desc->intro_nodes) * 1000; /* far too long,
                                                                    but okay.*/
      enc->desc_str = desc_str = tor_malloc_zero(desc_len);
      result = tor_snprintf(desc_str, desc_len,
               "rendezvous-service-descriptor %s\n"
               "version 2\n"
               "permanent-key\n%s"
               "secret-id-part %s\n"
               "publication-time %s\n"
               "protocol-versions %s\n",
          desc_id_base32,
          permanent_key,
          secret_id_part_base32,
          published,
          protocol_versions_string);
      tor_free(permanent_key);
      if (result < 0) {
        log_warn(LD_BUG, "Descriptor ran out of room.");
        rend_encoded_v2_service_descriptor_free(enc);
        goto err;
      }
      written = result;
      /* Add introduction points. */
      if (ipos_base64) {
        result = tor_snprintf(desc_str + written, desc_len - written,
                              "introduction-points\n"
                              "-----BEGIN MESSAGE-----\n%s"
                              "-----END MESSAGE-----\n",
                              ipos_base64);
        if (result < 0) {
          log_warn(LD_BUG, "could not write introduction points.");
          rend_encoded_v2_service_descriptor_free(enc);
          goto err;
        }
        written += result;
      }
      /* Add signature. */
      strlcpy(desc_str + written, "signature\n", desc_len - written);
      written += strlen(desc_str + written);
      if (crypto_digest(desc_digest, desc_str, written) < 0) {
        log_warn(LD_BUG, "could not create digest.");
        rend_encoded_v2_service_descriptor_free(enc);
        goto err;
      }
      if (router_append_dirobj_signature(desc_str + written,
                                         desc_len - written,
                                         desc_digest, DIGEST_LEN,
                                         service_key) < 0) {
        log_warn(LD_BUG, "Couldn't sign desc.");
        rend_encoded_v2_service_descriptor_free(enc);
        goto err;
      }
      written += strlen(desc_str+written);
      if (written+2 > desc_len) {
          log_warn(LD_BUG, "Could not finish desc.");
          rend_encoded_v2_service_descriptor_free(enc);
          goto err;
      }
      desc_str[written++] = 0;
      /* Check if we can parse our own descriptor. */
      if (!rend_desc_v2_is_parsable(enc)) {
        log_warn(LD_BUG, "Could not parse my own descriptor: %s", desc_str);
        rend_encoded_v2_service_descriptor_free(enc);
        goto err;
      }
      smartlist_add(descs_out, enc);
      /* Add the uploaded descriptor to the local service's descriptor cache */
      rend_cache_store_v2_desc_as_service(enc->desc_str);
      base32_encode(service_id_base32, sizeof(service_id_base32),
            service_id, REND_SERVICE_ID_LEN);
      control_event_hs_descriptor_created(service_id_base32, desc_id_base32, k);
    }
  
    log_info(LD_REND, "Successfully encoded a v2 descriptor and "
                      "confirmed that it is parsable.");
    goto done;
  
   err:
    SMARTLIST_FOREACH(descs_out, rend_encoded_v2_service_descriptor_t *, d,
                      rend_encoded_v2_service_descriptor_free(d););
    smartlist_clear(descs_out);
    seconds_valid = -1;
  
   done:
    tor_free(ipos_base64);
    return seconds_valid;
  }
  
  /** Sets <b>out</b> to the first 10 bytes of the digest of <b>pk</b>,
   * base32 encoded.  NUL-terminates out.  (We use this string to
   * identify services in directory requests and .onion URLs.)
   */
  int
  rend_get_service_id(crypto_pk_t *pk, char *out)
  {
    char buf[DIGEST_LEN];
    tor_assert(pk);
    if (crypto_pk_get_digest(pk, buf) < 0)
      return -1;
    base32_encode(out, REND_SERVICE_ID_LEN_BASE32+1, buf, REND_SERVICE_ID_LEN);
    return 0;
  }
  
  /** Return true iff <b>query</b> is a syntactically valid service ID (as
   * generated by rend_get_service_id).  */
  int
  rend_valid_service_id(const char *query)
  {
    if (strlen(query) != REND_SERVICE_ID_LEN_BASE32)
      return 0;
  
    if (strspn(query, BASE32_CHARS) != REND_SERVICE_ID_LEN_BASE32)
      return 0;
  
    return 1;
  }
  
  /** Return true iff <b>query</b> is a syntactically valid descriptor ID.
   * (as generated by rend_get_descriptor_id_bytes). */
  int
  rend_valid_descriptor_id(const char *query)
  {
    if (strlen(query) != REND_DESC_ID_V2_LEN_BASE32) {
      goto invalid;
    }
    if (strspn(query, BASE32_CHARS) != REND_DESC_ID_V2_LEN_BASE32) {
      goto invalid;
    }
  
    return 1;
  
   invalid:
    return 0;
  }
  
  /** Return true iff <b>client_name</b> is a syntactically valid name
   * for rendezvous client authentication. */
  int
  rend_valid_client_name(const char *client_name)
  {
    size_t len = strlen(client_name);
    if (len < 1 || len > REND_CLIENTNAME_MAX_LEN) {
      return 0;
    }
    if (strspn(client_name, REND_LEGAL_CLIENTNAME_CHARACTERS) != len) {
      return 0;
    }
  
    return 1;
  }
  
  /** Called when we get a rendezvous-related relay cell on circuit
   * <b>circ</b>.  Dispatch on rendezvous relay command. */
  void
  rend_process_relay_cell(circuit_t *circ, const crypt_path_t *layer_hint,
                          int command, size_t length,
                          const uint8_t *payload)
  {
    or_circuit_t *or_circ = NULL;
    origin_circuit_t *origin_circ = NULL;
    int r = -2;
    if (CIRCUIT_IS_ORIGIN(circ)) {
      origin_circ = TO_ORIGIN_CIRCUIT(circ);
      if (!layer_hint || layer_hint != origin_circ->cpath->prev) {
        log_fn(LOG_PROTOCOL_WARN, LD_APP,
               "Relay cell (rend purpose %d) from wrong hop on origin circ",
               command);
        origin_circ = NULL;
      }
    } else {
      or_circ = TO_OR_CIRCUIT(circ);
    }
  
    switch (command) {
      case RELAY_COMMAND_ESTABLISH_INTRO:
        if (or_circ)
          r = hs_intro_received_establish_intro(or_circ,payload,length);
        break;
      case RELAY_COMMAND_ESTABLISH_RENDEZVOUS:
        if (or_circ)
          r = rend_mid_establish_rendezvous(or_circ,payload,length);
        break;
      case RELAY_COMMAND_INTRODUCE1:
        if (or_circ)
          r = hs_intro_received_introduce1(or_circ,payload,length);
        break;
      case RELAY_COMMAND_INTRODUCE2:
        if (origin_circ)
          r = rend_service_receive_introduction(origin_circ,payload,length);
        break;
      case RELAY_COMMAND_INTRODUCE_ACK:
        if (origin_circ)
          r = rend_client_introduction_acked(origin_circ,payload,length);
        break;
      case RELAY_COMMAND_RENDEZVOUS1:
        if (or_circ)
          r = rend_mid_rendezvous(or_circ,payload,length);
        break;
      case RELAY_COMMAND_RENDEZVOUS2:
        if (origin_circ)
          r = rend_client_receive_rendezvous(origin_circ,payload,length);
        break;
      case RELAY_COMMAND_INTRO_ESTABLISHED:
        if (origin_circ)
          r = rend_service_intro_established(origin_circ,payload,length);
        break;
      case RELAY_COMMAND_RENDEZVOUS_ESTABLISHED:
        if (origin_circ)
          r = rend_client_rendezvous_acked(origin_circ,payload,length);
        break;
      default:
        tor_fragile_assert();
    }
  
    if (r == -2)
      log_info(LD_PROTOCOL, "Dropping cell (type %d) for wrong circuit type.",
               command);
  }
  
  /** Determine the routers that are responsible for <b>id</b> (binary) and
   * add pointers to those routers' routerstatus_t to <b>responsible_dirs</b>.
   * Return -1 if we're returning an empty smartlist, else return 0.
   */
  int
  hid_serv_get_responsible_directories(smartlist_t *responsible_dirs,
                                       const char *id)
  {
    int start, found, n_added = 0, i;
    networkstatus_t *c = networkstatus_get_latest_consensus();
    if (!c || !smartlist_len(c->routerstatus_list)) {
      log_warn(LD_REND, "We don't have a consensus, so we can't perform v2 "
               "rendezvous operations.");
      return -1;
    }
    tor_assert(id);
    start = networkstatus_vote_find_entry_idx(c, id, &found);
    if (start == smartlist_len(c->routerstatus_list)) start = 0;
    i = start;
    do {
      routerstatus_t *r = smartlist_get(c->routerstatus_list, i);
      if (r->is_hs_dir) {
        smartlist_add(responsible_dirs, r);
        if (++n_added == REND_NUMBER_OF_CONSECUTIVE_REPLICAS)
          return 0;
      }
      if (++i == smartlist_len(c->routerstatus_list))
        i = 0;
    } while (i != start);
  
    /* Even though we don't have the desired number of hidden service
     * directories, be happy if we got any. */
    return smartlist_len(responsible_dirs) ? 0 : -1;
  }
  
  /* Length of the 'extended' auth cookie used to encode auth type before
   * base64 encoding. */
  #define REND_DESC_COOKIE_LEN_EXT (REND_DESC_COOKIE_LEN + 1)
  /* Length of the zero-padded auth cookie when base64 encoded. These two
   * padding bytes always (A=) are stripped off of the returned cookie. */
  #define REND_DESC_COOKIE_LEN_EXT_BASE64 (REND_DESC_COOKIE_LEN_BASE64 + 2)
  
  /** Encode a client authorization descriptor cookie.
   * The result of this function is suitable for use in the HidServAuth
   * option.  The trailing padding characters are removed, and the
   * auth type is encoded into the cookie.
   *
   * Returns a new base64-encoded cookie. This function cannot fail.
   * The caller is responsible for freeing the returned value.
   */
  char *
  rend_auth_encode_cookie(const uint8_t *cookie_in, rend_auth_type_t auth_type)
  {
    uint8_t extended_cookie[REND_DESC_COOKIE_LEN_EXT];
    char *cookie_out = tor_malloc_zero(REND_DESC_COOKIE_LEN_EXT_BASE64 + 1);
    int re;
  
    tor_assert(cookie_in);
  
    memcpy(extended_cookie, cookie_in, REND_DESC_COOKIE_LEN);
    extended_cookie[REND_DESC_COOKIE_LEN] = ((int)auth_type - 1) << 4;
    re = base64_encode(cookie_out, REND_DESC_COOKIE_LEN_EXT_BASE64 + 1,
                       (const char *) extended_cookie, REND_DESC_COOKIE_LEN_EXT,
                       0);
    tor_assert(re == REND_DESC_COOKIE_LEN_EXT_BASE64);
  
    /* Remove the trailing 'A='.  Auth type is encoded in the high bits
     * of the last byte, so the last base64 character will always be zero
     * (A).  This is subtly different behavior from base64_encode_nopad. */
    cookie_out[REND_DESC_COOKIE_LEN_BASE64] = '\0';
    memwipe(extended_cookie, 0, sizeof(extended_cookie));
    return cookie_out;
  }
  
  /** Decode a base64-encoded client authorization descriptor cookie.
   * The descriptor_cookie can be truncated to REND_DESC_COOKIE_LEN_BASE64
   * characters (as given to clients), or may include the two padding
   * characters (as stored by the service).
   *
   * The result is stored in REND_DESC_COOKIE_LEN bytes of cookie_out.
   * The rend_auth_type_t decoded from the cookie is stored in the
   * optional auth_type_out parameter.
   *
   * Return 0 on success, or -1 on error.  The caller is responsible for
   * freeing the returned err_msg.
   */
  int
  rend_auth_decode_cookie(const char *cookie_in, uint8_t *cookie_out,
                          rend_auth_type_t *auth_type_out, char **err_msg_out)
  {
    uint8_t descriptor_cookie_decoded[REND_DESC_COOKIE_LEN_EXT + 1] = { 0 };
    char descriptor_cookie_base64ext[REND_DESC_COOKIE_LEN_EXT_BASE64 + 1];
    const char *descriptor_cookie = cookie_in;
    char *err_msg = NULL;
    int auth_type_val = 0;
    int res = -1;
    int decoded_len;
  
    size_t len = strlen(descriptor_cookie);
    if (len == REND_DESC_COOKIE_LEN_BASE64) {
      /* Add a trailing zero byte to make base64-decoding happy. */
      tor_snprintf(descriptor_cookie_base64ext,
                   sizeof(descriptor_cookie_base64ext),
                   "%sA=", descriptor_cookie);
      descriptor_cookie = descriptor_cookie_base64ext;
    } else if (len != REND_DESC_COOKIE_LEN_EXT_BASE64) {
      tor_asprintf(&err_msg, "Authorization cookie has wrong length: %s",
                   escaped(cookie_in));
      goto err;
    }
  
    decoded_len = base64_decode((char *) descriptor_cookie_decoded,
                                sizeof(descriptor_cookie_decoded),
                                descriptor_cookie,
                                REND_DESC_COOKIE_LEN_EXT_BASE64);
    if (decoded_len != REND_DESC_COOKIE_LEN &&
        decoded_len != REND_DESC_COOKIE_LEN_EXT) {
      tor_asprintf(&err_msg, "Authorization cookie has invalid characters: %s",
                   escaped(cookie_in));
      goto err;
    }
  
    if (auth_type_out) {
      auth_type_val = (descriptor_cookie_decoded[REND_DESC_COOKIE_LEN] >> 4) + 1;
      if (auth_type_val < 1 || auth_type_val > 2) {
        tor_asprintf(&err_msg, "Authorization cookie type is unknown: %s",
                     escaped(cookie_in));
        goto err;
      }
      *auth_type_out = auth_type_val == 1 ? REND_BASIC_AUTH : REND_STEALTH_AUTH;
    }
  
    memcpy(cookie_out, descriptor_cookie_decoded, REND_DESC_COOKIE_LEN);
    res = 0;
   err:
    if (err_msg_out) {
      *err_msg_out = err_msg;
    } else {
      tor_free(err_msg);
    }
    memwipe(descriptor_cookie_decoded, 0, sizeof(descriptor_cookie_decoded));
    memwipe(descriptor_cookie_base64ext, 0, sizeof(descriptor_cookie_base64ext));
    return res;
  }
  
  /* Is this a rend client or server that allows direct (non-anonymous)
   * connections?
   * Clients must be specifically compiled and configured in this mode.
   * Onion services can be configured to start in this mode.
   * Prefer rend_client_allow_non_anonymous_connection() or
   * rend_service_allow_non_anonymous_connection() whenever possible, so that
   * checks are specific to Single Onion Services or Tor2web. */
  int
  rend_allow_non_anonymous_connection(const or_options_t* options)
  {
    return (rend_client_allow_non_anonymous_connection(options)
            || rend_service_allow_non_anonymous_connection(options));
  }
  
  /* Is this a rend client or server in non-anonymous mode?
   * Clients must be specifically compiled in this mode.
   * Onion services can be configured to start in this mode.
   * Prefer rend_client_non_anonymous_mode_enabled() or
   * rend_service_non_anonymous_mode_enabled() whenever possible, so that checks
   * are specific to Single Onion Services or Tor2web. */
  int
  rend_non_anonymous_mode_enabled(const or_options_t *options)
  {
    return (rend_client_non_anonymous_mode_enabled(options)
            || rend_service_non_anonymous_mode_enabled(options));
  }
  
  /* Make sure that tor only builds one-hop circuits when they would not
   * compromise user anonymity.
   *
   * One-hop circuits are permitted in Tor2web or Single Onion modes.
   *
   * Tor2web or Single Onion modes are also allowed to make multi-hop circuits.
   * For example, single onion HSDir circuits are 3-hop to prevent denial of
   * service.
   */
  void
  assert_circ_anonymity_ok(origin_circuit_t *circ,
                           const or_options_t *options)
  {
    tor_assert(options);
    tor_assert(circ);
    tor_assert(circ->build_state);
  
    if (circ->build_state->onehop_tunnel) {
      tor_assert(rend_allow_non_anonymous_connection(options));
    }
  }
  
  /* Return 1 iff the given <b>digest</b> of a permenanent hidden service key is
   * equal to the digest in the origin circuit <b>ocirc</b> of its rend data .
   * If the rend data doesn't exist, 0 is returned. This function is agnostic to
   * the rend data version. */
  int
  rend_circuit_pk_digest_eq(const origin_circuit_t *ocirc,
                            const uint8_t *digest)
  {
    size_t rend_pk_digest_len;
    const uint8_t *rend_pk_digest;
  
    tor_assert(ocirc);
    tor_assert(digest);
  
    if (ocirc->rend_data == NULL) {
      goto no_match;
    }
  
    rend_pk_digest = rend_data_get_pk_digest(ocirc->rend_data,
                                             &rend_pk_digest_len);
    if (tor_memeq(rend_pk_digest, digest, rend_pk_digest_len)) {
      goto match;
    }
   no_match:
    return 0;
   match:
    return 1;
  }
  
  