text: // Copyright (c) 2015-2021 The Bitcoin Core developers
  // Copyright (c) 2017 The Zcash developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <torcontrol.h>
  
  #include <chainparams.h>
  #include <chainparamsbase.h>
  #include <compat.h>
  #include <crypto/hmac_sha256.h>
  #include <net.h>
  #include <netaddress.h>
  #include <netbase.h>
  #include <util/readwritefile.h>
  #include <util/strencodings.h>
  #include <util/syscall_sandbox.h>
  #include <util/system.h>
  #include <util/thread.h>
  #include <util/time.h>
  
  #include <deque>
  #include <functional>
  #include <set>
  #include <vector>
  
  #include <event2/buffer.h>
  #include <event2/bufferevent.h>
  #include <event2/event.h>
  #include <event2/thread.h>
  #include <event2/util.h>
  
  /** Default control port */
  const std::string DEFAULT_TOR_CONTROL = "127.0.0.1:9051";
  /** Tor cookie size (from control-spec.txt) */
  static const int TOR_COOKIE_SIZE = 32;
  /** Size of client/server nonce for SAFECOOKIE */
  static const int TOR_NONCE_SIZE = 32;
  /** For computing serverHash in SAFECOOKIE */
  static const std::string TOR_SAFE_SERVERKEY = "Tor safe cookie authentication server-to-controller hash";
  /** For computing clientHash in SAFECOOKIE */
  static const std::string TOR_SAFE_CLIENTKEY = "Tor safe cookie authentication controller-to-server hash";
  /** Exponential backoff configuration - initial timeout in seconds */
  static const float RECONNECT_TIMEOUT_START = 1.0;
  /** Exponential backoff configuration - growth factor */
  static const float RECONNECT_TIMEOUT_EXP = 1.5;
  /** Maximum length for lines received on TorControlConnection.
   * tor-control-spec.txt mentions that there is explicitly no limit defined to line length,
   * this is belt-and-suspenders sanity limit to prevent memory exhaustion.
   */
  static const int MAX_LINE_LENGTH = 100000;
  static const uint16_t DEFAULT_TOR_SOCKS_PORT = 9050;
  
  /****** Low-level TorControlConnection ********/
  
  TorControlConnection::TorControlConnection(struct event_base *_base):
      base(_base), b_conn(nullptr)
  {
  }
  
  TorControlConnection::~TorControlConnection()
  {
      if (b_conn)
          bufferevent_free(b_conn);
  }
  
  void TorControlConnection::readcb(struct bufferevent *bev, void *ctx)
  {
      TorControlConnection *self = static_cast<TorControlConnection*>(ctx);
      struct evbuffer *input = bufferevent_get_input(bev);
      size_t n_read_out = 0;
      char *line;
      assert(input);
      //  If there is not a whole line to read, evbuffer_readln returns nullptr
      while((line = evbuffer_readln(input, &n_read_out, EVBUFFER_EOL_CRLF)) != nullptr)
      {
          std::string s(line, n_read_out);
          free(line);
          if (s.size() < 4) // Short line
              continue;
          // <status>(-|+| )<data><CRLF>
          self->message.code = LocaleIndependentAtoi<int>(s.substr(0,3));
          self->message.lines.push_back(s.substr(4));
          char ch = s[3]; // '-','+' or ' '
          if (ch == ' ') {
              // Final line, dispatch reply and clean up
              if (self->message.code >= 600) {
                  // Dispatch async notifications to async handler
                  // Synchronous and asynchronous messages are never interleaved
                  self->async_handler(*self, self->message);
              } else {
                  if (!self->reply_handlers.empty()) {
                      // Invoke reply handler with message
                      self->reply_handlers.front()(*self, self->message);
                      self->reply_handlers.pop_front();
                  } else {
                      LogPrint(BCLog::TOR, "Received unexpected sync reply %i\n", self->message.code);
                  }
              }
              self->message.Clear();
          }
      }
      //  Check for size of buffer - protect against memory exhaustion with very long lines
      //  Do this after evbuffer_readln to make sure all full lines have been
      //  removed from the buffer. Everything left is an incomplete line.
      if (evbuffer_get_length(input) > MAX_LINE_LENGTH) {
          LogPrintf("tor: Disconnecting because MAX_LINE_LENGTH exceeded\n");
          self->Disconnect();
      }
  }
  
  void TorControlConnection::eventcb(struct bufferevent *bev, short what, void *ctx)
  {
      TorControlConnection *self = static_cast<TorControlConnection*>(ctx);
      if (what & BEV_EVENT_CONNECTED) {
          LogPrint(BCLog::TOR, "Successfully connected!\n");
          self->connected(*self);
      } else if (what & (BEV_EVENT_EOF|BEV_EVENT_ERROR)) {
          if (what & BEV_EVENT_ERROR) {
              LogPrint(BCLog::TOR, "Error connecting to Tor control socket\n");
          } else {
              LogPrint(BCLog::TOR, "End of stream\n");
          }
          self->Disconnect();
          self->disconnected(*self);
      }
  }
  
  bool TorControlConnection::Connect(const std::string& tor_control_center, const ConnectionCB& _connected, const ConnectionCB& _disconnected)
  {
      if (b_conn) {
          Disconnect();
      }
  
      CService control_service;
      if (!Lookup(tor_control_center, control_service, 9051, fNameLookup)) {
          LogPrintf("tor: Failed to look up control center %s\n", tor_control_center);
          return false;
      }
  
      struct sockaddr_storage control_address;
      socklen_t control_address_len = sizeof(control_address);
      if (!control_service.GetSockAddr(reinterpret_cast<struct sockaddr*>(&control_address), &control_address_len)) {
          LogPrintf("tor: Error parsing socket address %s\n", tor_control_center);
          return false;
      }
  
      // Create a new socket, set up callbacks and enable notification bits
      b_conn = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);
      if (!b_conn) {
          return false;
      }
      bufferevent_setcb(b_conn, TorControlConnection::readcb, nullptr, TorControlConnection::eventcb, this);
      bufferevent_enable(b_conn, EV_READ|EV_WRITE);
      this->connected = _connected;
      this->disconnected = _disconnected;
  
      // Finally, connect to tor_control_center
      if (bufferevent_socket_connect(b_conn, reinterpret_cast<struct sockaddr*>(&control_address), control_address_len) < 0) {
          LogPrintf("tor: Error connecting to address %s\n", tor_control_center);
          return false;
      }
      return true;
  }
  
  void TorControlConnection::Disconnect()
  {
      if (b_conn)
          bufferevent_free(b_conn);
      b_conn = nullptr;
  }
  
  bool TorControlConnection::Command(const std::string &cmd, const ReplyHandlerCB& reply_handler)
  {
      if (!b_conn)
          return false;
      struct evbuffer *buf = bufferevent_get_output(b_conn);
      if (!buf)
          return false;
      evbuffer_add(buf, cmd.data(), cmd.size());
      evbuffer_add(buf, "\r\n", 2);
      reply_handlers.push_back(reply_handler);
      return true;
  }
  
  /****** General parsing utilities ********/
  
  /* Split reply line in the form 'AUTH METHODS=...' into a type
   * 'AUTH' and arguments 'METHODS=...'.
   * Grammar is implicitly defined in https://spec.torproject.org/control-spec by
   * the server reply formats for PROTOCOLINFO (S3.21) and AUTHCHALLENGE (S3.24).
   */
  std::pair<std::string,std::string> SplitTorReplyLine(const std::string &s)
  {
      size_t ptr=0;
      std::string type;
      while (ptr < s.size() && s[ptr] != ' ') {
          type.push_back(s[ptr]);
          ++ptr;
      }
      if (ptr < s.size())
          ++ptr; // skip ' '
      return make_pair(type, s.substr(ptr));
  }
  
  /** Parse reply arguments in the form 'METHODS=COOKIE,SAFECOOKIE COOKIEFILE=".../control_auth_cookie"'.
   * Returns a map of keys to values, or an empty map if there was an error.
   * Grammar is implicitly defined in https://spec.torproject.org/control-spec by
   * the server reply formats for PROTOCOLINFO (S3.21), AUTHCHALLENGE (S3.24),
   * and ADD_ONION (S3.27). See also sections 2.1 and 2.3.
   */
  std::map<std::string,std::string> ParseTorReplyMapping(const std::string &s)
  {
      std::map<std::string,std::string> mapping;
      size_t ptr=0;
      while (ptr < s.size()) {
          std::string key, value;
          while (ptr < s.size() && s[ptr] != '=' && s[ptr] != ' ') {
              key.push_back(s[ptr]);
              ++ptr;
          }
          if (ptr == s.size()) // unexpected end of line
              return std::map<std::string,std::string>();
          if (s[ptr] == ' ') // The remaining string is an OptArguments
              break;
          ++ptr; // skip '='
          if (ptr < s.size() && s[ptr] == '"') { // Quoted string
              ++ptr; // skip opening '"'
              bool escape_next = false;
              while (ptr < s.size() && (escape_next || s[ptr] != '"')) {
                  // Repeated backslashes must be interpreted as pairs
                  escape_next = (s[ptr] == '\\' && !escape_next);
                  value.push_back(s[ptr]);
                  ++ptr;
              }
              if (ptr == s.size()) // unexpected end of line
                  return std::map<std::string,std::string>();
              ++ptr; // skip closing '"'
              /**
               * Unescape value. Per https://spec.torproject.org/control-spec section 2.1.1:
               *
               *   For future-proofing, controller implementors MAY use the following
               *   rules to be compatible with buggy Tor implementations and with
               *   future ones that implement the spec as intended:
               *
               *     Read \n \t \r and \0 ... \377 as C escapes.
               *     Treat a backslash followed by any other character as that character.
               */
              std::string escaped_value;
              for (size_t i = 0; i < value.size(); ++i) {
                  if (value[i] == '\\') {
                      // This will always be valid, because if the QuotedString
                      // ended in an odd number of backslashes, then the parser
                      // would already have returned above, due to a missing
                      // terminating double-quote.
                      ++i;
                      if (value[i] == 'n') {
                          escaped_value.push_back('\n');
                      } else if (value[i] == 't') {
                          escaped_value.push_back('\t');
                      } else if (value[i] == 'r') {
                          escaped_value.push_back('\r');
                      } else if ('0' <= value[i] && value[i] <= '7') {
                          size_t j;
                          // Octal escape sequences have a limit of three octal digits,
                          // but terminate at the first character that is not a valid
                          // octal digit if encountered sooner.
                          for (j = 1; j < 3 && (i+j) < value.size() && '0' <= value[i+j] && value[i+j] <= '7'; ++j) {}
                          // Tor restricts first digit to 0-3 for three-digit octals.
                          // A leading digit of 4-7 would therefore be interpreted as
                          // a two-digit octal.
                          if (j == 3 && value[i] > '3') {
                              j--;
                          }
                          const auto end{i + j};
                          uint8_t val{0};
                          while (i < end) {
                              val *= 8;
                              val += value[i++] - '0';
                          }
                          escaped_value.push_back(char(val));
                          // Account for automatic incrementing at loop end
                          --i;
                      } else {
                          escaped_value.push_back(value[i]);
                      }
                  } else {
                      escaped_value.push_back(value[i]);
                  }
              }
              value = escaped_value;
          } else { // Unquoted value. Note that values can contain '=' at will, just no spaces
              while (ptr < s.size() && s[ptr] != ' ') {
                  value.push_back(s[ptr]);
                  ++ptr;
              }
          }
          if (ptr < s.size() && s[ptr] == ' ')
              ++ptr; // skip ' ' after key=value
          mapping[key] = value;
      }
      return mapping;
  }
  
  TorController::TorController(struct event_base* _base, const std::string& tor_control_center, const CService& target):
      base(_base),
      m_tor_control_center(tor_control_center), conn(base), reconnect(true), reconnect_timeout(RECONNECT_TIMEOUT_START),
      m_target(target)
  {
      reconnect_ev = event_new(base, -1, 0, reconnect_cb, this);
      if (!reconnect_ev)
          LogPrintf("tor: Failed to create event for reconnection: out of memory?\n");
      // Start connection attempts immediately
      if (!conn.Connect(m_tor_control_center, std::bind(&TorController::connected_cb, this, std::placeholders::_1),
           std::bind(&TorController::disconnected_cb, this, std::placeholders::_1) )) {
          LogPrintf("tor: Initiating connection to Tor control port %s failed\n", m_tor_control_center);
      }
      // Read service private key if cached
      std::pair<bool,std::string> pkf = ReadBinaryFile(GetPrivateKeyFile());
      if (pkf.first) {
          LogPrint(BCLog::TOR, "Reading cached private key from %s\n", fs::PathToString(GetPrivateKeyFile()));
          private_key = pkf.second;
      }
  }
  
  TorController::~TorController()
  {
      if (reconnect_ev) {
          event_free(reconnect_ev);
          reconnect_ev = nullptr;
      }
      if (service.IsValid()) {
          RemoveLocal(service);
      }
  }
  
  void TorController::get_socks_cb(TorControlConnection& _conn, const TorControlReply& reply)
  {
      // NOTE: We can only get here if -onion is unset
      std::string socks_location;
      if (reply.code == 250) {
          for (const auto& line : reply.lines) {
              if (0 == line.compare(0, 20, "net/listeners/socks=")) {
                  const std::string port_list_str = line.substr(20);
                  std::vector<std::string> port_list = SplitString(port_list_str, ' ');
  
                  for (auto& portstr : port_list) {
                      if (portstr.empty()) continue;
                      if ((portstr[0] == '"' || portstr[0] == '\'') && portstr.size() >= 2 && (*portstr.rbegin() == portstr[0])) {
                          portstr = portstr.substr(1, portstr.size() - 2);
                          if (portstr.empty()) continue;
                      }
                      socks_location = portstr;
                      if (0 == portstr.compare(0, 10, "127.0.0.1:")) {
                          // Prefer localhost - ignore other ports
                          break;
                      }
                  }
              }
          }
          if (!socks_location.empty()) {
              LogPrint(BCLog::TOR, "Get SOCKS port command yielded %s\n", socks_location);
          } else {
              LogPrintf("tor: Get SOCKS port command returned nothing\n");
          }
      } else if (reply.code == 510) {  // 510 Unrecognized command
          LogPrintf("tor: Get SOCKS port command failed with unrecognized command (You probably should upgrade Tor)\n");
      } else {
          LogPrintf("tor: Get SOCKS port command failed; error code %d\n", reply.code);
      }
  
      CService resolved;
      Assume(!resolved.IsValid());
      if (!socks_location.empty()) {
          resolved = LookupNumeric(socks_location, DEFAULT_TOR_SOCKS_PORT);
      }
      if (!resolved.IsValid()) {
          // Fallback to old behaviour
          resolved = LookupNumeric("127.0.0.1", DEFAULT_TOR_SOCKS_PORT);
      }
  
      Assume(resolved.IsValid());
      LogPrint(BCLog::TOR, "Configuring onion proxy for %s\n", resolved.ToStringIPPort());
      Proxy addrOnion = Proxy(resolved, true);
      SetProxy(NET_ONION, addrOnion);
  
      const auto onlynets = gArgs.GetArgs("-onlynet");
  
      const bool onion_allowed_by_onlynet{
          !gArgs.IsArgSet("-onlynet") ||
          std::any_of(onlynets.begin(), onlynets.end(), [](const auto& n) {
              return ParseNetwork(n) == NET_ONION;
          })};
  
      if (onion_allowed_by_onlynet) {
          // If NET_ONION is reachable, then the below is a noop.
          //
          // If NET_ONION is not reachable, then none of -proxy or -onion was given.
          // Since we are here, then -torcontrol and -torpassword were given.
          SetReachable(NET_ONION, true);
      }
  }
  
  void TorController::add_onion_cb(TorControlConnection& _conn, const TorControlReply& reply)
  {
      if (reply.code == 250) {
          LogPrint(BCLog::TOR, "ADD_ONION successful\n");
          for (const std::string &s : reply.lines) {
              std::map<std::string,std::string> m = ParseTorReplyMapping(s);
              std::map<std::string,std::string>::iterator i;
              if ((i = m.find("ServiceID")) != m.end())
                  service_id = i->second;
              if ((i = m.find("PrivateKey")) != m.end())
                  private_key = i->second;
          }
          if (service_id.empty()) {
              LogPrintf("tor: Error parsing ADD_ONION parameters:\n");
              for (const std::string &s : reply.lines) {
                  LogPrintf("    %s\n", SanitizeString(s));
              }
              return;
          }
          service = LookupNumeric(std::string(service_id+".onion"), Params().GetDefaultPort());
          LogPrintf("tor: Got service ID %s, advertising service %s\n", service_id, service.ToString());
          if (WriteBinaryFile(GetPrivateKeyFile(), private_key)) {
              LogPrint(BCLog::TOR, "Cached service private key to %s\n", fs::PathToString(GetPrivateKeyFile()));
          } else {
              LogPrintf("tor: Error writing service private key to %s\n", fs::PathToString(GetPrivateKeyFile()));
          }
          AddLocal(service, LOCAL_MANUAL);
          // ... onion requested - keep connection open
      } else if (reply.code == 510) { // 510 Unrecognized command
          LogPrintf("tor: Add onion failed with unrecognized command (You probably need to upgrade Tor)\n");
      } else {
          LogPrintf("tor: Add onion failed; error code %d\n", reply.code);
      }
  }
  
  void TorController::auth_cb(TorControlConnection& _conn, const TorControlReply& reply)
  {
      if (reply.code == 250) {
          LogPrint(BCLog::TOR, "Authentication successful\n");
  
          // Now that we know Tor is running setup the proxy for onion addresses
          // if -onion isn't set to something else.
          if (gArgs.GetArg("-onion", "") == "") {
              _conn.Command("GETINFO net/listeners/socks", std::bind(&TorController::get_socks_cb, this, std::placeholders::_1, std::placeholders::_2));
          }
  
          // Finally - now create the service
          if (private_key.empty()) { // No private key, generate one
              private_key = "NEW:ED25519-V3"; // Explicitly request key type - see issue #9214
          }
          // Request onion service, redirect port.
          // Note that the 'virtual' port is always the default port to avoid decloaking nodes using other ports.
          _conn.Command(strprintf("ADD_ONION %s Port=%i,%s", private_key, Params().GetDefaultPort(), m_target.ToStringIPPort()),
              std::bind(&TorController::add_onion_cb, this, std::placeholders::_1, std::placeholders::_2));
      } else {
          LogPrintf("tor: Authentication failed\n");
      }
  }
  
  /** Compute Tor SAFECOOKIE response.
   *
   *    ServerHash is computed as:
   *      HMAC-SHA256("Tor safe cookie authentication server-to-controller hash",
   *                  CookieString | ClientNonce | ServerNonce)
   *    (with the HMAC key as its first argument)
   *
   *    After a controller sends a successful AUTHCHALLENGE command, the
   *    next command sent on the connection must be an AUTHENTICATE command,
   *    and the only authentication string which that AUTHENTICATE command
   *    will accept is:
   *
   *      HMAC-SHA256("Tor safe cookie authentication controller-to-server hash",
   *                  CookieString | ClientNonce | ServerNonce)
   *
   */
  static std::vector<uint8_t> ComputeResponse(const std::string &key, const std::vector<uint8_t> &cookie,  const std::vector<uint8_t> &clientNonce, const std::vector<uint8_t> &serverNonce)
  {
      CHMAC_SHA256 computeHash((const uint8_t*)key.data(), key.size());
      std::vector<uint8_t> computedHash(CHMAC_SHA256::OUTPUT_SIZE, 0);
      computeHash.Write(cookie.data(), cookie.size());
      computeHash.Write(clientNonce.data(), clientNonce.size());
      computeHash.Write(serverNonce.data(), serverNonce.size());
      computeHash.Finalize(computedHash.data());
      return computedHash;
  }
  
  void TorController::authchallenge_cb(TorControlConnection& _conn, const TorControlReply& reply)
  {
      if (reply.code == 250) {
          LogPrint(BCLog::TOR, "SAFECOOKIE authentication challenge successful\n");
          std::pair<std::string,std::string> l = SplitTorReplyLine(reply.lines[0]);
          if (l.first == "AUTHCHALLENGE") {
              std::map<std::string,std::string> m = ParseTorReplyMapping(l.second);
              if (m.empty()) {
                  LogPrintf("tor: Error parsing AUTHCHALLENGE parameters: %s\n", SanitizeString(l.second));
                  return;
              }
              std::vector<uint8_t> serverHash = ParseHex(m["SERVERHASH"]);
              std::vector<uint8_t> serverNonce = ParseHex(m["SERVERNONCE"]);
              LogPrint(BCLog::TOR, "AUTHCHALLENGE ServerHash %s ServerNonce %s\n", HexStr(serverHash), HexStr(serverNonce));
              if (serverNonce.size() != 32) {
                  LogPrintf("tor: ServerNonce is not 32 bytes, as required by spec\n");
                  return;
              }
  
              std::vector<uint8_t> computedServerHash = ComputeResponse(TOR_SAFE_SERVERKEY, cookie, clientNonce, serverNonce);
              if (computedServerHash != serverHash) {
                  LogPrintf("tor: ServerHash %s does not match expected ServerHash %s\n", HexStr(serverHash), HexStr(computedServerHash));
                  return;
              }
  
              std::vector<uint8_t> computedClientHash = ComputeResponse(TOR_SAFE_CLIENTKEY, cookie, clientNonce, serverNonce);
              _conn.Command("AUTHENTICATE " + HexStr(computedClientHash), std::bind(&TorController::auth_cb, this, std::placeholders::_1, std::placeholders::_2));
          } else {
              LogPrintf("tor: Invalid reply to AUTHCHALLENGE\n");
          }
      } else {
          LogPrintf("tor: SAFECOOKIE authentication challenge failed\n");
      }
  }
  
  void TorController::protocolinfo_cb(TorControlConnection& _conn, const TorControlReply& reply)
  {
      if (reply.code == 250) {
          std::set<std::string> methods;
          std::string cookiefile;
          /*
           * 250-AUTH METHODS=COOKIE,SAFECOOKIE COOKIEFILE="/home/x/.tor/control_auth_cookie"
           * 250-AUTH METHODS=NULL
           * 250-AUTH METHODS=HASHEDPASSWORD
           */
          for (const std::string &s : reply.lines) {
              std::pair<std::string,std::string> l = SplitTorReplyLine(s);
              if (l.first == "AUTH") {
                  std::map<std::string,std::string> m = ParseTorReplyMapping(l.second);
                  std::map<std::string,std::string>::iterator i;
                  if ((i = m.find("METHODS")) != m.end()) {
                      std::vector<std::string> m_vec = SplitString(i->second, ',');
                      methods = std::set<std::string>(m_vec.begin(), m_vec.end());
                  }
                  if ((i = m.find("COOKIEFILE")) != m.end())
                      cookiefile = i->second;
              } else if (l.first == "VERSION") {
                  std::map<std::string,std::string> m = ParseTorReplyMapping(l.second);
                  std::map<std::string,std::string>::iterator i;
                  if ((i = m.find("Tor")) != m.end()) {
                      LogPrint(BCLog::TOR, "Connected to Tor version %s\n", i->second);
                  }
              }
          }
          for (const std::string &s : methods) {
              LogPrint(BCLog::TOR, "Supported authentication method: %s\n", s);
          }
          // Prefer NULL, otherwise SAFECOOKIE. If a password is provided, use HASHEDPASSWORD
          /* Authentication:
           *   cookie:   hex-encoded ~/.tor/control_auth_cookie
           *   password: "password"
           */
          std::string torpassword = gArgs.GetArg("-torpassword", "");
          if (!torpassword.empty()) {
              if (methods.count("HASHEDPASSWORD")) {
                  LogPrint(BCLog::TOR, "Using HASHEDPASSWORD authentication\n");
                  ReplaceAll(torpassword, "\"", "\\\"");
                  _conn.Command("AUTHENTICATE \"" + torpassword + "\"", std::bind(&TorController::auth_cb, this, std::placeholders::_1, std::placeholders::_2));
              } else {
                  LogPrintf("tor: Password provided with -torpassword, but HASHEDPASSWORD authentication is not available\n");
              }
          } else if (methods.count("NULL")) {
              LogPrint(BCLog::TOR, "Using NULL authentication\n");
              _conn.Command("AUTHENTICATE", std::bind(&TorController::auth_cb, this, std::placeholders::_1, std::placeholders::_2));
          } else if (methods.count("SAFECOOKIE")) {
              // Cookie: hexdump -e '32/1 "%02x""\n"'  ~/.tor/control_auth_cookie
              LogPrint(BCLog::TOR, "Using SAFECOOKIE authentication, reading cookie authentication from %s\n", cookiefile);
              std::pair<bool,std::string> status_cookie = ReadBinaryFile(fs::PathFromString(cookiefile), TOR_COOKIE_SIZE);
              if (status_cookie.first && status_cookie.second.size() == TOR_COOKIE_SIZE) {
                  // _conn.Command("AUTHENTICATE " + HexStr(status_cookie.second), std::bind(&TorController::auth_cb, this, std::placeholders::_1, std::placeholders::_2));
                  cookie = std::vector<uint8_t>(status_cookie.second.begin(), status_cookie.second.end());
                  clientNonce = std::vector<uint8_t>(TOR_NONCE_SIZE, 0);
                  GetRandBytes(clientNonce);
                  _conn.Command("AUTHCHALLENGE SAFECOOKIE " + HexStr(clientNonce), std::bind(&TorController::authchallenge_cb, this, std::placeholders::_1, std::placeholders::_2));
              } else {
                  if (status_cookie.first) {
                      LogPrintf("tor: Authentication cookie %s is not exactly %i bytes, as is required by the spec\n", cookiefile, TOR_COOKIE_SIZE);
                  } else {
                      LogPrintf("tor: Authentication cookie %s could not be opened (check permissions)\n", cookiefile);
                  }
              }
          } else if (methods.count("HASHEDPASSWORD")) {
              LogPrintf("tor: The only supported authentication mechanism left is password, but no password provided with -torpassword\n");
          } else {
              LogPrintf("tor: No supported authentication method\n");
          }
      } else {
          LogPrintf("tor: Requesting protocol info failed\n");
      }
  }
  
  void TorController::connected_cb(TorControlConnection& _conn)
  {
      reconnect_timeout = RECONNECT_TIMEOUT_START;
      // First send a PROTOCOLINFO command to figure out what authentication is expected
      if (!_conn.Command("PROTOCOLINFO 1", std::bind(&TorController::protocolinfo_cb, this, std::placeholders::_1, std::placeholders::_2)))
          LogPrintf("tor: Error sending initial protocolinfo command\n");
  }
  
  void TorController::disconnected_cb(TorControlConnection& _conn)
  {
      // Stop advertising service when disconnected
      if (service.IsValid())
          RemoveLocal(service);
      service = CService();
      if (!reconnect)
          return;
  
      LogPrint(BCLog::TOR, "Not connected to Tor control port %s, trying to reconnect\n", m_tor_control_center);
  
      // Single-shot timer for reconnect. Use exponential backoff.
      struct timeval time = MillisToTimeval(int64_t(reconnect_timeout * 1000.0));
      if (reconnect_ev)
          event_add(reconnect_ev, &time);
      reconnect_timeout *= RECONNECT_TIMEOUT_EXP;
  }
  
  void TorController::Reconnect()
  {
      /* Try to reconnect and reestablish if we get booted - for example, Tor
       * may be restarting.
       */
      if (!conn.Connect(m_tor_control_center, std::bind(&TorController::connected_cb, this, std::placeholders::_1),
           std::bind(&TorController::disconnected_cb, this, std::placeholders::_1) )) {
          LogPrintf("tor: Re-initiating connection to Tor control port %s failed\n", m_tor_control_center);
      }
  }
  
  fs::path TorController::GetPrivateKeyFile()
  {
      return gArgs.GetDataDirNet() / "onion_v3_private_key";
  }
  
  void TorController::reconnect_cb(evutil_socket_t fd, short what, void *arg)
  {
      TorController *self = static_cast<TorController*>(arg);
      self->Reconnect();
  }
  
  /****** Thread ********/
  static struct event_base *gBase;
  static std::thread torControlThread;
  
  static void TorControlThread(CService onion_service_target)
  {
      SetSyscallSandboxPolicy(SyscallSandboxPolicy::TOR_CONTROL);
      TorController ctrl(gBase, gArgs.GetArg("-torcontrol", DEFAULT_TOR_CONTROL), onion_service_target);
  
      event_base_dispatch(gBase);
  }
  
  void StartTorControl(CService onion_service_target)
  {
      assert(!gBase);
  #ifdef WIN32
      evthread_use_windows_threads();
  #else
      evthread_use_pthreads();
  #endif
      gBase = event_base_new();
      if (!gBase) {
          LogPrintf("tor: Unable to create event_base\n");
          return;
      }
  
      torControlThread = std::thread(&util::TraceThread, "torcontrol", [onion_service_target] {
          TorControlThread(onion_service_target);
      });
  }
  
  void InterruptTorControl()
  {
      if (gBase) {
          LogPrintf("tor: Thread interrupt\n");
          event_base_once(gBase, -1, EV_TIMEOUT, [](evutil_socket_t, short, void*) {
              event_base_loopbreak(gBase);
          }, nullptr, nullptr);
      }
  }
  
  void StopTorControl()
  {
      if (gBase) {
          torControlThread.join();
          event_base_free(gBase);
          gBase = nullptr;
      }
  }
  
  CService DefaultOnionServiceTarget()
  {
      struct in_addr onion_service_target;
      onion_service_target.s_addr = htonl(INADDR_LOOPBACK);
      return {onion_service_target, BaseParams().OnionServiceTargetPort()};
  }
  