telebit-relay.js/lib/relay.js

'use strict';

var url = require('url');
var PromiseA = require('bluebird');
var jwt = require('jsonwebtoken');
var Packer = require('proxy-packer');
var portServers = {};

function timeoutPromise(duration) {
  return new PromiseA(function (resolve) {
    setTimeout(resolve, duration);
  });
}

var Devices = require('./device-tracker');
var pipeWs = require('./pipe-ws.js');

module.exports.store = { Devices: Devices };
module.exports.create = function (state) {
  state.deviceLists = {};
  //var deviceLists = {};
  var activityTimeout = state.activityTimeout || 2*60*1000;
  var pongTimeout = state.pongTimeout || 10*1000;
  state.Devices = Devices;
  var onTcpConnection = require('./unwrap-tls').createTcpConnectionHandler(state);

  // TODO Use a Single TCP Handler
  // Issues:
  //   * dynamic ports are dedicated to a device or cluster
  //   * servernames could come in on ports that belong to a different device
  //   * servernames could come in that belong to no device
  //   * this could lead to an attack / security vulnerability with ACME certificates
  // Solutions
  //   * Restrict dynamic ports to a particular device
  //   * Restrict the use of servernames
  function onDynTcpConn(conn) {
    var serviceport = this.address().port;
    console.log('[DynTcpConn] new connection on', serviceport);
    var remote = Devices.next(state.deviceLists, serviceport)

    if (!remote) {
      conn.write("[Sanity Error] I've got a blank space baby, but nowhere to write your name.");
      conn.end();
      try {
        this.close();
      } catch(e) {
        console.error("[DynTcpConn] failed to close server:", e);
      }
      return;
    }

    conn.once('data', function (firstChunk) {
      if (state.debug) { console.log("[DynTcp]", serviceport, "examining firstChunk from", Packer.socketToId(conn)); }
      conn.pause();
      //conn.unshift(firstChunk);
      conn._handle.onread(firstChunk.length, firstChunk);

      var servername;
      var hostname;
      var str;
      var m;

      if (22 === firstChunk[0]) {
        servername = (sni(firstChunk)||'').toLowerCase();
      } else if (firstChunk[0] > 32 && firstChunk[0] < 127) {
        str = firstChunk.toString();
        m = str.match(/(?:^|[\r\n])Host: ([^\r\n]+)[\r\n]*/im);
        hostname = (m && m[1].toLowerCase() || '').split(':')[0];
      }

      if (servername || hostname) {
        if (servername) {
          conn.write("TLS with sni is allowed only on standard ports. If you've registered '" + servername + "' use port 443.");
        } else {
          conn.write("HTTP with Host headers is not allowed on dynamic ports. If you've registered '" + hostname + "' use port 80.");
        }
        conn.end();
        return;
      }

      // pipeWs(servername, servicename, client, remote, serviceport)
      // remote.clients is managed as part of the piping process
      if (state.debug) { console.log("[DynTcp]", serviceport, "piping to remote"); }
      pipeWs(null, 'tcp', conn, remote, serviceport)

      process.nextTick(function () { conn.resume(); });
    });
  }

  function onWsConnection(ws, upgradeReq) {
    var socketId = Packer.socketToId(upgradeReq.socket);
    if (state.debug) { console.log('[ws] connection', socketId); }

    var remotes = {};
    var firstToken;
    var authn = (upgradeReq.headers.authorization||'').split(/\s+/);
    if (authn[0] && 'basic' === authn[0].toLowerCase()) {
      try {
        authn = new Buffer(authn[1], 'base64').toString('ascii').split(':');
        firstToken = authn[1];
      } catch (err) { }
    }

    if (!firstToken) {
      firstToken = url.parse(upgradeReq.url, true).query.access_token;
    }
    if (!firstToken) {
      next();
      return;
    }
    if (firstToken) {
      return addToken(firstToken, true).then(next).catch(function (err) {
        sendTunnelMsg(null, [0, err], 'control');
        ws.close();
      });
    }

    function logName() {
      var result = Object.keys(remotes).map(function (jwtoken) {
        return remotes[jwtoken].deviceId;
      }).join(';');

      return result || socketId;
    }

    function sendTunnelMsg(addr, data, service) {
      ws.send(Packer.pack(addr, data, service), {binary: true});
    }

    function getBrowserConn(cid) {
      var browserConn;
      Object.keys(remotes).some(function (jwtoken) {
        if (remotes[jwtoken].clients[cid]) {
          browserConn = remotes[jwtoken].clients[cid];
          return true;
        }
      });

      return browserConn;
    }

    function closeBrowserConn(cid) {
      var remote;
      Object.keys(remotes).some(function (jwtoken) {
        if (remotes[jwtoken].clients[cid]) {
          remote = remotes[jwtoken];
          return true;
        }
      });
      if (!remote) {
        return;
      }

      PromiseA.resolve().then(function () {
        var conn = remote.clients[cid];
        conn.tunnelClosing = true;
        conn.end();

        // If no data is buffered for writing then we don't need to wait for it to drain.
        if (!conn.bufferSize) {
          return timeoutPromise(500);
        }
        // Otherwise we want the connection to be able to finish, but we also want to impose
        // a time limit for it to drain, since it shouldn't have more than 1MB buffered.
        return new PromiseA(function (resolve) {
          var timeoutId = setTimeout(resolve, 60*1000);
          conn.once('drain', function () {
            clearTimeout(timeoutId);
            setTimeout(resolve, 500);
          });
        });
      }).then(function () {
        if (remote.clients[cid]) {
          console.warn(cid, 'browser connection still present after calling `end`');
          remote.clients[cid].destroy();
          return timeoutPromise(500);
        }
      }).then(function () {
        if (remote.clients[cid]) {
          console.error(cid, 'browser connection still present after calling `destroy`');
          delete remote.clients[cid];
        }
      }).catch(function (err) {
        console.warn('failed to close browser connection', cid, err);
      });
    }

    function addToken(jwtoken) {

      function onAuth(token) {
        if ('string' !== typeof jwtoken) {
          jwtoken = JSON.stringify(jwtoken);
        }
        var err;
        if (!token) {
          err = new Error("invalid access token");
          err.code = "E_INVALID_TOKEN";
          return state.Promise.reject(err);
        }

        if (token.jwt && jwtoken !== token.jwt) {
          // Access Token
          sendTunnelMsg(
            null
          , [ 3
            , 'access_token'
            , { jwt: token.jwt }
            ]
          , 'control'
          );
          // these aren't needed internally once they're sent
          token.jwt = null;
        }

        if (!Array.isArray(token.domains)) {
          if ('string' === typeof token.name) {
            token.domains = [ token.name ];
          }
        }

        if (!Array.isArray(token.domains) || !token.domains.length) {
          err = new Error("invalid domains array");
          err.code = "E_INVALID_NAME";
          return state.Promise.reject(err);
        }
        if (token.domains.some(function (name) { return typeof name !== 'string'; })) {
          err = new Error("invalid domain name(s)");
          err.code = "E_INVALID_NAME";
          return state.Promise.reject(err);
        }

        // Add the custom properties we need to manage this remote, then add it to all the relevant
        // domains and the list of all this websocket's remotes.
        token.deviceId = (token.device && (token.device.id || token.device.hostname)) || token.domains.join(',');
        token.ws = ws;
        token.upgradeReq = upgradeReq;
        token.clients = {};

        token.pausedConns = [];
        ws._socket.on('drain', function () {
          // the websocket library has it's own buffer apart from node's socket buffer, but that one
          // is much more difficult to watch, so we watch for the lower level buffer to drain and
          // then check to see if the upper level buffer is still too full to write to. Note that
          // the websocket library buffer has something to do with compression, so I'm not requiring
          // that to be 0 before we start up again.
          if (ws.bufferedAmount > 128*1024) {
            return;
          }

          token.pausedConns.forEach(function (conn) {
            if (!conn.manualPause) {
              // console.log('resuming', conn.tunnelCid, 'now that the web socket has caught up');
              conn.resume();
            }
          });
          token.pausedConns.length = 0;
        });

        token.domains.forEach(function (domainname) {
          Devices.add(state.deviceLists, domainname, token);
        });

        function onDynTcpReadyHelper(serviceport) {
          //token.dynamicPorts.push(serviceport);
          Devices.add(state.deviceLists, serviceport, token);
          //var hri = require('human-readable-ids').hri;
          //var hrname = hri.random() + '.telebit.cloud';
          //token.dynamicNames.push(hrname);
          // TODO restrict to authenticated device
          // TODO pull servername from config
          // TODO remove hrname on disconnect
          //Devices.add(state.deviceLists, hrname, token);
          sendTunnelMsg(
            null
          , [ 2
            , 'grant'
            , [ ['ssh+https', token.domains[0], 443 ]
              , ['ssh', 'ssh.telebit.cloud', serviceport ]
              , ['tcp', 'tcp.telebit.cloud', serviceport]
              , ['https', token.domains[0] ]
              ]
            ]
          , 'control'
          );
        }

        console.log('[DEBUG] got to firstToken check');

        if (!token.ports) {
          token.ports = [];
        }
        if (!firstToken || firstToken === jwtoken) {
          if (!token.ports.length) {
            token.ports.push( 0 );
          }
          firstToken = token.jwt || jwtoken;
        }

        //token.dynamicPorts = [];
        //token.dynamicNames = [];

        var onePortForNow = parseInt(token.ports[0], 10) || 0;
        if (portServers[onePortForNow]) {
          //token.ports = [];
          token.server = portServers[onePortForNow];
          token.server.on('connection', onDynTcpConn);
          onDynTcpReadyHelper(onePortForNow);
        } else {
          try {
            token.server = require('net').createServer(onDynTcpConn).listen(onePortForNow, function () {
              var serviceport = this.address().port;
              portServers[serviceport] = this;
              console.info('[DynTcpConn] Port', serviceport, 'now open for', token.deviceId);
              onDynTcpReadyHelper(serviceport);
            });
            token.server.on('error', function (e) {
              // TODO try again with random port
              console.error("Server Error assigning a dynamic port to a new connection:", e);
            });
          } catch(e) {
            // what a wonderful problem it will be the day that this bug needs to be fixed
            // (i.e. there are enough users to run out of ports)
            console.error("Error assigning a dynamic port to a new connection:", e);
          }
        }

        remotes[jwtoken] = token;
        console.info("[ws] authorized", socketId, "for", token.deviceId);
        return null;
      }

      if (remotes[jwtoken]) {
        // return { message: "token sent multiple times", code: "E_TOKEN_REPEAT" };
        return state.Promise.resolve(null);
      }

      return state.authenticate({ auth: jwtoken }).then(onAuth);
    }

    function removeToken(jwtoken) {
      var remote = remotes[jwtoken];
      if (!remote) {
        return { message: 'specified token not present', code: 'E_INVALID_TOKEN'};
      }

      // Prevent any more browser connections being sent to this remote, and any existing
      // connections from trying to send more data across the connection.
      remote.domains.forEach(function (domainname) {
        Devices.remove(state.deviceLists, domainname, remote);
      });
      remote.ports.forEach(function (portnumber) {
        Devices.remove(state.deviceLists, portnumber, remote);
      });
      remote.ws = null;
      remote.upgradeReq = null;
      if (remote.server) {
        remote.serverPort = remote.server.address().port;
        remote.server.close(function () {
          console.log("[DynTcpConn] closing server for ", remote.serverPort);
          remote.serverPort = null;
        });
        remote.server = null;
      }

      // Close all of the existing browser connections associated with this websocket connection.
      Object.keys(remote.clients).forEach(function (cid) {
        closeBrowserConn(cid);
      });
      delete remotes[jwtoken];
      console.log("[ws] removed token '" + remote.deviceId + "' from", socketId);
      return null;
    }

    function next() {
      var commandHandlers = {
        add_token: addToken
      , auth: addToken
      , authn: addToken
      , authz: addToken
      , delete_token: function (token) {
          return state.Promise.resolve(function () {
            var err;

            if (token !== '*') {
              err = removeToken(token);
              if (err) { return state.Promise.reject(err); }
            }

            Object.keys(remotes).some(function (jwtoken) {
              err = removeToken(jwtoken);
              return err;
            });
            if (err) { return state.Promise.reject(err); }

            return null;
          });
        }
      };

      var packerHandlers = {
        oncontrol: function (tun) {
          var cmd;
          try {
            cmd = JSON.parse(tun.data.toString());
          } catch (e) {}
          if (!Array.isArray(cmd) || typeof cmd[0] !== 'number') {
            var msg = 'received bad command "' + tun.data.toString() + '"';
            console.warn(msg, 'from websocket', socketId);
            sendTunnelMsg(null, [0, {message: msg, code: 'E_BAD_COMMAND'}], 'control');
            return;
          }

          if (cmd[0] < 0) {
            // We only ever send one command and we send it once, so we just hard coded the ID as 1.
            if (cmd[0] === -1) {
              if (cmd[1]) {
                console.warn('received error response to hello from', socketId, cmd[1]);
              }
            }
            else {
              console.warn('received response to unknown command', cmd, 'from', socketId);
            }
            return;
          }

          if (cmd[0] === 0) {
            console.warn('received dis-associated error from', socketId, cmd[1]);
            return;
          }

          function onSuccess() {
            sendTunnelMsg(null, [-cmd[0], null], 'control');
          }
          function onError(err) {
            sendTunnelMsg(null, [-cmd[0], err], 'control');
          }

          if (!commandHandlers[cmd[1]]) {
            onError({ message: 'unknown command "'+cmd[1]+'"', code: 'E_UNKNOWN_COMMAND' });
            return;
          }

          return commandHandlers[cmd[1]].apply(null, cmd.slice(2)).then(onSuccess, onError);
        }

      , onmessage: function (tun) {
          var cid = Packer.addrToId(tun);
          if (state.debug) { console.log("remote '" + logName() + "' has data for '" + cid + "'", tun.data.byteLength); }

          var browserConn = getBrowserConn(cid);
          if (!browserConn) {
            sendTunnelMsg(tun, {message: 'no matching connection', code: 'E_NO_CONN'}, 'error');
            return;
          }

          browserConn.write(tun.data);
          // tunnelRead is how many bytes we've read from the tunnel, and written to the browser.
          browserConn.tunnelRead = (browserConn.tunnelRead || 0) + tun.data.byteLength;
          // If we have more than 1MB buffered data we need to tell the other side to slow down.
          // Once we've finished sending what we have we can tell the other side to keep going.
          // If we've already sent the 'pause' message though don't send it again, because we're
          // probably just dealing with data queued before our message got to them.
          if (!browserConn.remotePaused && browserConn.bufferSize > 1024*1024) {
            sendTunnelMsg(tun, browserConn.tunnelRead, 'pause');
            browserConn.remotePaused = true;

            browserConn.once('drain', function () {
              sendTunnelMsg(tun, browserConn.tunnelRead, 'resume');
              browserConn.remotePaused = false;
            });
          }
        }

      , onpause: function (tun) {
          var cid = Packer.addrToId(tun);
          console.log('[TunnelPause]', cid);
          var browserConn = getBrowserConn(cid);
          if (browserConn) {
            browserConn.manualPause = true;
            browserConn.pause();
          } else {
            sendTunnelMsg(tun, {message: 'no matching connection', code: 'E_NO_CONN'}, 'error');
          }
        }

      , onresume: function (tun) {
          var cid = Packer.addrToId(tun);
          console.log('[TunnelResume]', cid);
          var browserConn = getBrowserConn(cid);
          if (browserConn) {
            browserConn.manualPause = false;
            browserConn.resume();
          } else {
            sendTunnelMsg(tun, {message: 'no matching connection', code: 'E_NO_CONN'}, 'error');
          }
        }

      , onend: function (tun) {
          var cid = Packer.addrToId(tun);
          console.log('[TunnelEnd]', cid);
          closeBrowserConn(cid);
        }
      , onerror: function (tun) {
          var cid = Packer.addrToId(tun);
          console.warn('[TunnelError]', cid, tun.message);
          closeBrowserConn(cid);
        }
      };
      var unpacker = Packer.create(packerHandlers);

      function refreshTimeout() {
        lastActivity = Date.now();
      }

      function checkTimeout() {
        // Determine how long the connection has been "silent", ie no activity.
        var silent = Date.now() - lastActivity;

        // If we have had activity within the last activityTimeout then all we need to do is
        // call this function again at the soonest time when the connection could be timed out.
        if (silent < activityTimeout) {
          timeoutId = setTimeout(checkTimeout, activityTimeout-silent);
        }

        // Otherwise we check to see if the pong has also timed out, and if not we send a ping
        // and call this function again when the pong will have timed out.
        else if (silent < activityTimeout + pongTimeout) {
          if (state.debug) { console.log('pinging', logName()); }
          try {
            ws.ping();
          } catch (err) {
            console.warn('failed to ping home cloud', logName());
          }
          timeoutId = setTimeout(checkTimeout, pongTimeout);
        }

        // Last case means the ping we sent before didn't get a response soon enough, so we
        // need to close the websocket connection.
        else {
          console.warn('home cloud', logName(), 'connection timed out');
          ws.close(1013, 'connection timeout');
        }
      }

      function forwardMessage(chunk) {
        refreshTimeout();
        if (state.debug) { console.log('[ws] device => client : demultiplexing message ', chunk.byteLength, 'bytes'); }
        //console.log(chunk.toString());
        unpacker.fns.addChunk(chunk);
      }

      function hangup() {
        clearTimeout(timeoutId);
        console.log('[ws] device hangup', logName(), 'connection closing');
        Object.keys(remotes).forEach(function (jwtoken) {
          removeToken(jwtoken);
        });
        ws.terminate();
      }

      var lastActivity = Date.now();
      var timeoutId;

      timeoutId = setTimeout(checkTimeout, activityTimeout);

      // Note that our websocket library automatically handles pong responses on ping requests
      // before it even emits the event.
      ws.on('ping', refreshTimeout);
      ws.on('pong', refreshTimeout);
      ws.on('message', forwardMessage);
      ws.on('close', hangup);
      ws.on('error', hangup);

      // Status Code '1' for Status 'hello'
      sendTunnelMsg(null, [1, 'hello', [unpacker._version], Object.keys(commandHandlers)], 'control');
    }
  }

  return {
    tcp: onTcpConnection
  , ws: onWsConnection
  , isClientDomain: Devices.exist.bind(null, state.deviceLists)
  };
};