node-slowloris/index.js

helps aliviate slow loris attack by giving developer 2 extra options, 1- headerTimeout, the timeout to receive the headers. 2- minRate the minimum rate (bytes/second) with rateOverhead to compensate for initial delay to receive data

var _default = {
  headerTimeout: 2500,
  minRate: 500,
  rateOverhead: 50
};
module.exports = function(server, options) {
  options = options || _default;
  var headerTimeout = options.headerTimeout === undefined ? _default.headerTimeout : options.headerTimeout;
  var minRate = options.minRate === undefined ? _default.minRate : options.minRate;

  if(!headerTimeout && !minRate) {
    return;
  }

  var rateOverhead = options.rateOverhead === undefined ? _default.rateOverhead : options.rateOverhead;

  server.keepAliveTimeout = 0.00001;
  server.on('connection', function(socket) {
    var socketData = {
      received: 0,
      headerTimeoutTimer: headerTimeout ? setTimeout(function() {
        if(socketData.headerTimeoutTimer) {
          socket.write('HTTP/1.1 504 Gateway Timeout\r\n\r\n');
          socket.end();
          socketData.headerTimeoutTimer = false;
        }
      }, headerTimeout) : false
    };
    socket.on('close', function(chunk) {
      if(socketData.headerTimeoutTimer) {
        clearTimeout(socketData.headerTimeoutTimer);
        socketData.headerTimeoutTimer = false;
      }
    });
    socket.on('data', function(chunk) {
      if(socketData.headerTimeoutTimer) {
        clearTimeout(socketData.headerTimeoutTimer);
        socketData.headerTimeoutTimer = false;
      }
      if(minRate) {
        socketData.received += chunk.length;
        if(!socketData.start) {
          socketData.start = Date.now();
        }
        else {
          var delTime = Date.now() - socketData.start - rateOverhead;
          if(delTime > 0) {
            var rate = socketData.received / delTime;
            if(rate < minRate) {
              socket.write('HTTP/1.1 504 Gateway Timeout\r\n\r\n');
              socket.end();
            }
          }
        }
      }
    });
  });
};