ssh port knock script

knock.sh

!/bin/bash
#Purpose: Open/close SSH port via port knock
#Author: Mohan Balasundaram
#Date: 24/04/2015
NC="/bin/nc"
OPT="-z -w3"
PORT_OPEN_ORDER="10010 11020 12030"
PORT_CLOSE_ORDER="12030 11020 10010"
HOST="192.168.1.250" #jumpbox host
SSH_PORT="22"

if [ "$#" -ne 1 ]; then
  echo "Usage: $0 open|close"
  exit 2;
fi

if [[ $1 =~ ^([oO][pP][eE][nN])$ ]]; then
  echo "Opening SSH Port"

  for PORT in ${PORT_OPEN_ORDER}; do
    ${NC} ${OPT} ${HOST} ${PORT}
  done

  sleep 2;
  echo "Checking SSH Port"
  ${NC} ${OPT} ${HOST} ${SSH_PORT}

elif [[ $1 =~ ^([cC][lL][oO][Ss][eE])$ ]]; then
  echo "Closing SSH Port"

  for PORT in ${PORT_CLOSE_ORDER}; do
    ${NC} ${OPT} ${HOST} ${PORT}
  done

  sleep 1;
  echo "Checking SSH Port"
    ${NC} ${OPT} ${HOST} ${SSH_PORT} || echo "Connection to ${HOST} ${SSH_PORT} port [tcp/ssh] FAILED!"
else
  echo "Invalid Input: $1"
  echo "Usage: $0 open|close"
fi