package main

import (
	"bufio"
	"encoding/binary"
	"flag"
	"fmt"
	"math/rand"
	"net"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
)

var (
	// flags
	cidr     = flag.String("r", "", "")
	targlist = flag.String("l", "", "")
	duration = flag.Int("t", -1, "")
	workers  = flag.Int("c", 10, "")
	delay    = flag.Int("u", 0, "")

	rfc1918 = []string{
		"0.0.0.0/8",
		"10.0.0.0/8",
		"192.168.0.0/16",
		"172.16.0.0/12",
	}

	// colors
	colorReset  = "\033[0m"
	colorRed    = "\033[31m"
	colorPurple = "\033[35m"
	colorCyan   = "\033[36m"
	skull       = "\u2620"

	// target ports
	ports = []int{21, 22, 23, 25, 53, 80, 81, 123, 389, 443, 445, 999, 1080, 1433, 2323, 5555, 5900, 7547, 8080, 8081, 8888}
)

func winsize(system int) uint16 {
	switch system {
	case 1:
		return 29200 // Linux
	case 2:
		return 5840 // Linux
	case 3:
		return 5720 // Linux
	case 4:
		return 10220 // Linux
	case 5:
		return 14600 // Linux
	case 6:
		return 8192 // Windows
	case 7:
		return 65535 // Windows
	case 8:
		return 65535 // MacOS, FreeBSD
	case 9:
		return 16384 // OpenBSD
	case 10:
		return 4128 // Cisco IOS
	case 11:
		return 32850 // Solaris
	case 12:
		return 49640 // Solaris
	default:
		return 8192
	}
}

func ittl(system int) uint8 {
	switch system {
	case 6:
		return 128 // Windows
	case 7:
		return 128 // Windows
	case 10:
		return 255 // Cisco IOS
	default:
		return 64 // Linux, MacOS, FreeBSD, OpenBSD, Solaris
	}
}

func assemble(daddr, saddr string, dport, sport, system int) ([]byte, error) {
	ip := &layers.IPv4{
		SrcIP:    net.ParseIP(saddr).To4(),
		DstIP:    net.ParseIP(daddr).To4(),
		Version:  4,
		TTL:      ittl(system),
		Protocol: layers.IPProtocolTCP,
	}

	tcp := &layers.TCP{
		SrcPort: layers.TCPPort(sport),
		DstPort: layers.TCPPort(dport),
		Window:  winsize(system),
		Seq:     rand.Uint32(),
		SYN:     true,
	}

	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	payload := []byte{}
	pl := gopacket.Payload(payload)

	buf := gopacket.NewSerializeBuffer()

	if err := tcp.SetNetworkLayerForChecksum(ip); err != nil {
		return nil, err
	}

	if err := gopacket.SerializeLayers(buf, opts, ip, tcp, pl); err != nil {
		return nil, err
	}

	packet := buf.Bytes()
	return packet, nil
}

func excluded(ip net.IP) bool {
	for _, ex := range rfc1918 {
		_, cidr, _ := net.ParseCIDR(ex)
		if cidr.Contains(ip) {
			return true
		}
	}

	return false
}

func sendpacket(fd int, packet []byte, addr string) error {
	ip := net.ParseIP(addr)
	dest := format4(ip)
	if err := syscall.Sendto(fd, packet, 0, &dest); err != nil {
		return err
	}

	return nil
}

func rawsocket() (int, error) {
	handler, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
	if err != nil {
		return -1, err
	}
	return handler, nil
}

func format4(ip net.IP) (addr syscall.SockaddrInet4) {
	addr = syscall.SockaddrInet4{Port: 0}
	copy(addr.Addr[:], ip.To4()[0:4])
	return addr
}

func runCIDR(cidr string, out chan string) error {
	ip, ipnet, err := net.ParseCIDR(cidr)
	if err != nil {
		return err
	}

	for target := ip.Mask(ipnet.Mask); ipnet.Contains(target); inc(target) {
		if excluded(target) {
			continue
		}
		addr, _ := net.ResolveIPAddr("ip", target.String())
		out <- addr.String()
	}
	return nil
}

func inc(ip net.IP) {
	for j := len(ip) - 1; j >= 0; j-- {
		ip[j]++
		if ip[j] > 0 {
			break
		}
	}
}

func randIP() string {
	for {
		buf := make([]byte, 4)
		ip := rand.Uint32()
		binary.LittleEndian.PutUint32(buf, ip)
		nip := net.IP(buf)
		if !excluded(nip) {
			return nip.String()
		}
	}
}

func thread(addrs chan string) {
	sock, err := rawsocket()
	if err != nil {
		fatal(err.Error())
	}
	defer syscall.Close(sock)
	for addr := range addrs {
		rip := randIP()
		dport := ports[rand.Intn(len(ports))]
		sport := 1024 + rand.Intn(64511)
		syst := 1 + rand.Intn(11)

		pkt, _ := assemble(addr, rip, dport, sport, syst)

		fmt.Printf("[%s%s%s] %s%s:%d%s -> %s%s%s:%s%d%s\n", colorRed, sysident(syst), colorReset, colorCyan, rip, sport, colorReset, colorPurple, addr, colorReset, colorCyan, dport, colorReset)

		sendpacket(sock, pkt, addr)
		time.Sleep(time.Microsecond * time.Duration(*delay))
	}
}

func sysident(id int) string {
	if id >= 1 && id <= 5 {
		return "Linux"
	} else if id >= 6 && id <= 7 {
		return "Windows"
	} else if id == 8 {
		return "MacOS/FreeBSD"
	} else if id == 9 {
		return "OpenBSD"
	} else if id == 10 {
		return "Cisco IOS"
	} else if id >= 11 && id <= 12 {
		return "Solaris"
	} else {
		return "Windows"
	}
}

func banner() {
	fmt.Printf(`
          %sgot some intelligence for u
                  right here%s%s
          _                         _
         |_|                       |_|
         | |         /^^^\         | |
        _| |_      (| "o" |)      _| |_
      _| | | | _    (_---_)    _ | | | |_
     | | | | |' |    _| |_    | '| | | | |
     |          |   /     \   |          |
      \        /  / /(. .)\ \  \        /
        \    /  / /  | . |  \ \  \    /
          \  \/ /    ||Y||    \ \/  /
           \__/      || ||      \__/
                     () ()
                     || ||
                    ooO Ooo

                %s%sg a y n o i s e%s

 sincerely,
    ~ delorean

`, colorRed, colorReset, colorCyan, colorReset, colorPurple, colorReset)
}

func usage() {
	fmt.Fprintf(os.Stderr, `gaynoise:
    (%s-r%s) - cidr range [%s0.0.0.0/0%s]
    (%s-l%s) - target cidr list
    (%s-c%s) - concurrent threads [%s100%s]
    (%s-t%s) - duration [%s-1%s]
    (%s-p%s) - usec delay between sends [%s0%s]
`, colorCyan, colorReset, colorPurple, colorReset, colorCyan, colorReset, colorCyan, colorReset, colorPurple, colorReset, colorCyan, colorReset, colorPurple, colorReset, colorCyan, colorReset, colorPurple, colorReset)
}

func fatal(e string) {
	fmt.Printf("%s %s error:%s %s\n", colorRed, skull, colorReset, e)
	os.Exit(-1)
}

func alarm(secs int) {
	time.Sleep(time.Second * time.Duration(secs))
	os.Exit(0)
}

func parsetargets(list string) []string {
	fd, err := os.Open(list)
	if err != nil {
		fatal(err.Error())
	}
	defer fd.Close()

	var targets []string

	fs := bufio.NewScanner(fd)
	for fs.Scan() {
		line := strings.TrimSpace(fs.Text())
		if len(line) > 0 {
			if _, _, err := net.ParseCIDR(line); err == nil {
				targets = append(targets, line)
			}
		}
	}

	if len(targets) == 0 {
		fatal("no valid ranges parsed from file")
	}
	return targets
}

func main() {
	flag.Usage = usage
	flag.Parse()

	var targets []string
	if *targlist != "" {
		targets = parsetargets(*targlist)
	} else if *cidr == "" {
		targets = []string{"0.0.0.0/0"}
	} else {
		targets = []string{*cidr}
	}

	// signals
	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
	go func() {
		<-sigs
		fmt.Printf("\n%s%s Stopped%s\n", colorRed, skull, colorReset)
		os.Exit(1)
	}()

	// threads
	addrs := make(chan string)
	for x := 0; x < *workers; x++ {
		go thread(addrs)
	}

	// start alarm
	if *duration > 0 {
		go alarm(*duration)
	}

	banner()

	for {
		for _, target := range targets {
			if err := runCIDR(target, addrs); err != nil {
				fatal(err.Error())
			}
		}
	}
}