goknockr/knockr.go

package main

import (
	"fmt"
	"io"
	"net"
)

var whitelist []string

func main() {
	go listener(9090, whitelist_handler)
	listener(8080, gateway_handler)
}

func listener(port int, listen_func func(c net.Conn)) {
	ln, err := net.Listen("tcp", fmt.Sprintf(":%d", port))

	if err != nil {
		fmt.Println("Errur on Listening")
	} else {
		fmt.Println("Opened :", port)
		for {
			conn, err := ln.Accept()
			if err != nil {
				fmt.Println("Errur on Accepting")
			} else {
				go listen_func(conn)
			}
		}
	}
}

func whitelist_handler(c net.Conn) {
	host, _, _ := net.SplitHostPort(c.RemoteAddr().String())

	io.WriteString(c, "Knock Knock, ")
	io.WriteString(c, host)
	io.WriteString(c, ". ")

	add_to_whitelist(host)

	c.Close()
}

func gateway_handler(c net.Conn) {
	host, _, _ := net.SplitHostPort(c.RemoteAddr().String())

	if is_whitelisted(host) {
		fmt.Println("OK: ", host)
		proxy(c)
	} else {
		fmt.Println("BLOCK: ", host)
	}
	c.Close()
}

func add_to_whitelist(addr string) {
	if ! is_whitelisted(addr) {
		whitelist = append(whitelist, addr)
	}
}

func is_whitelisted(addr string) bool {
	for i:=0; i < len(whitelist); i++ {
		if whitelist[i] == addr {
			return true
		}
	}

	return false
}

func proxy(c net.Conn) {
	ln, err := net.Dial("tcp", "ip.darknebu.la:443")
	if err != nil {
		fmt.Println("ERR proxy")
	} else {
		go io.Copy(c, ln)
		io.Copy(ln, c)
	}
}