95 lines
2.0 KiB
Go
95 lines
2.0 KiB
Go
package main
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import (
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"fmt"
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"io"
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"net"
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"github.com/mkideal/cli"
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)
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type knockArguments struct {
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cli.Helper
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WhitelistPort int `cli:'wp' usage:'The port to launch the whitelist server on'`
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GatewayPort int `cli:'gp' usage:'The port to protect'`
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Destination string `cli:'d' usage:'The destination to relay traffic to'`
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}
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var whitelist []string
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var arguments *knockArguments
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func main() {
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cli.Run(new(knockArguments), func(ctx *cli.Context) error {
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arguments = ctx.Argv() . (*knockArguments)
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return nil
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})
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go listener(arguments.WhitelistPort, whitelist_handler)
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listener(arguments.GatewayPort, gateway_handler)
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}
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func listener(port int, listen_func func(c net.Conn)) {
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ln, err := net.Listen("tcp", fmt.Sprintf(":%d", port))
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if err != nil {
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fmt.Println("[ERR] Creating listener for Port ", port)
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fmt.Println(" Error is ", err)
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} else {
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fmt.Println("[OK ] Creating listener for Port ", port)
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for {
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conn, err := ln.Accept()
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if err != nil {
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fmt.Println("[ERR] Accepting on Port ", port)
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} else {
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go listen_func(conn)
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}
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}
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}
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}
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func whitelist_handler(c net.Conn) {
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host, _, _ := net.SplitHostPort(c.RemoteAddr().String())
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io.WriteString(c, fmt.Sprintf("Knock Knock, %s.", host))
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add_to_whitelist(host)
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c.Close()
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}
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func gateway_handler(c net.Conn) {
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host, _, _ := net.SplitHostPort(c.RemoteAddr().String())
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if is_whitelisted(host) {
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fmt.Println("[OK ] Whitelisted host ", host, " connected")
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proxy(c)
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} else {
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fmt.Println("[BLK] Blocking host ", host)
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}
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c.Close()
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}
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func add_to_whitelist(addr string) {
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if ! is_whitelisted(addr) {
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whitelist = append(whitelist, addr)
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}
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}
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func is_whitelisted(addr string) bool {
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for i:=0; i < len(whitelist); i++ {
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if whitelist[i] == addr {
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return true
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}
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}
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return false
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}
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func proxy(c net.Conn) {
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ln, err := net.Dial("tcp", arguments.Destination)
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if err != nil {
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fmt.Println("[ERR] Proxy connection to server failed")
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fmt.Println(" Error is ", err)
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} else {
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go io.Copy(c, ln)
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io.Copy(ln, c)
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}
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}
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