UDP Hole Punching PoC for bash

udp_punch-out.sh

#!/bin/bash
#
# UDP PUNCH-OUT! UDP-HOLE PUNCHING
# ---------------------------------
#
# local send:  From: 1.1.1.1:13337    -> remote-ip:RANDOM
# remote send: From: remote-ip:RANDOM -> 1.1.1.1:13337
#

_use_udp_hp() 
{
	#SPORT= port to open local
	#DPORT= Random UDP ports on remote (shouln't be in use)
	SPORT=13337
	RANGE=$((64000-4097))
	DPORT=$(($(($RANDOM%$RANGE))+4097))

	if [ "$1" == "local-bhfw" ]; then
		REMOTEHOST=$2

		#Local
		#get_remoteIP()
		LRIP=$(curl -s http://ifconfig.co)
		echo;echo "[*] User on Remote side, ExtIP: $LRIP $DPORT"

		#set hping3 (-2 UDP packets)
		# hping3 -c 1 -2 -s $SPORT -p $DPORT $REMOTEHOST
		nping --udp -c 1 --source-port $SPORT --dest-port $DPORT $REMOTEHOST

		#set nc on localside:
		nc -u -l -p $SPORT

	elif [ "$1" == "remote-nofw" ]; then
		PUNCHPORT=$3
		LRIP=$2

		#set on remote side (openports UDP)
		echo; echo "Got the punch in ur face" | nc -p $PUNCHPORT -u $LRIP $SPORT
	else

		echo; echo "[!] Error no input , exit now.."
		exit 1
	fi

}
echo "^------------------------------------^"
echo "^ UDP PUNCH-OUT v0.1 (c) 2022 suuhm  ^"
echo "^------------------------------------^"
echo
echo "Usage: $0 local-bhfw <REMOTE_IP>|remote-nofw <LO_EXT_IP> <PUNCH_PORT>"
echo
echo "!!!           Needs netcat and / or hping , nping (nmap suite)        !!!"
echo "!!! ----------------------------------------------------------------- !!!"
echo "!!! Run the script 1st on localhost with NAT fw, later than on remote !!!"
echo; sleep 1

_use_udp_hp $1 $2 $3

exit 0