#!/usr/bin/env bash
# Script to check if specified IP is on common known dns blacklists
# Copyright (C) 2018  Aaron Ball <nullspoon@oper.io>
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

# Default to opendns main nameserver if the NS variable isn't set
export NS=${NS:-208.67.220.220}

# Pertinent color escape sequences
export CGREEN=$'\e[32m'
export CRED=$'\e[31m'
export CRESET=$'\e[0m'

# is_ipv4:
# Checks if the provided string is a valid IPv4 address.
#
# @str   String to check
# @return (stdout) 1 == valid ip, 0 == invalid ip
is_ipv4() {
  local str="${1}"
  local match
  match=$(printf "${str}" | grep -E '^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$')
  if [ "${match}" = "${str}" ]; then
    printf 1
    return 0;
  fi
  printf 0;
  return 1;
}


usage() {
  printf "Usage:\n  %s [options] <ip>\n\n" "$(basename ${0})"
  printf "Options:\n"
  printf "  -h,--help       Print this help text\n"
  printf "  -m,--manifest   Path to file containing DNSBL manifest\n"
  printf "  -s,--summary    Print only number of lists IP was found on\n"
}


parseargs() {
  local args=("${@}")
  for (( i = 0; i < ${#args[@]}; i++ )); do
    if [ "${args[$i]}" = '-h' ] || [ "${args[$i]}" = '-h' ]; then
      usage
      exit 0
    elif [ "${args[$i]}" = '-s' ] || [ "${args[$i]}" = '--summary' ]; then
      _SUMMARY=1
    elif [ "${args[$i]}" = '-m' ] || [ "${args[$i]}" = '--manifest' ]; then
      i=$(( i + 1 ))
      _MANIFEST="${args[$i]}"
    else
      _IP="${args[$i]}"
    fi
  done

  if [ -z "${_IP}" ]; then
    printf "IP address required\n"
    return 1
  fi

  if [ $(is_ipv4 "${_IP}") = 0 ]; then
    printf "Provided IP '%s' is not a valid IPv4 address\n" "${_IP}"
    return 1
  fi
}


# main:
# Ye olde' main.
#
# @ip   IP address to check for blacklist
main() {
  local rev       # IP address, reversed for dns lookup (dig)
  local resp      # Response from dns query
  local dnsbls    # Array of dns blacklist endpoints
  local found     # Number of times the ip was found in blacklists

  local _IP=''       # IP to query DNSBLs for
  local _SUMMARY=0   # Print only DNSBL count summary (number of lists
                     # blacklisting the ip)
  local _MANIFEST='' # Manifest of DNSBLs to check

  # Set defaults
  _MANIFEST="dnsbls.txt"

  # Parse cli args into arg variables
  parseargs ${@} || return $?

  # If the terminal is not a char terminal (eg: someone is using less, more,
  # cat, etc), we don't want to print escape codes because they will get
  # mangled by the tool most likely.
  if [ ! -t 1 ]; then
    unset CGREEN
    unset CRED
    unset CRESET
  fi

  # Reverse the ip address
  rev=$(printf '%s.' "${_IP}" | tac -s.)

  # Some basic information
  if [ "${_SUMMARY}" -eq 0 ]; then
    printf "Checking %s\n" "${_IP}"
    printf "Reverse DNS: %s\n\n" "$(dig @${NS} +short -x ${_IP})"
  fi

  if [ ! -f "${_MANIFEST}" ]; then
    printf "ERROR: DNSBL manifest '%s' not accessible.\n" "${_MANIFEST}"
    printf "Please set LIST environment variable to file that exists\n"
    return 1
  else
    dnsbls=($(grep -v '^#' "${_MANIFEST}"))
  fi

  found=0
  for bl in ${dnsbls[@]}; do
    # I can dig it
    resp="$(dig @${NS} +short -t a ${rev}${bl})"
    [ "${_SUMMARY}" -eq 0 ] && printf "%-25s: " "${bl}"
    if [ -z "${resp}" ]; then
      [ "${_SUMMARY}" -eq 0 ] && printf "%bNot found%b\n" "${CGREEN}" "${CRESET}"
    else
      [ "${_SUMMARY}" -eq 0 ] && printf "%bFound%b\n" "${CRED}" "${CRESET}"
      found=$((found + 1))
    fi
  done

  if [ ${_SUMMARY} -eq 0 ]; then
    printf "\nFound %s on %d lists\n" "${_IP}" "${found}"
  else
    printf "%d\n" "${found}"
  fi
}

main ${@}