通过TLS回调函数的反调试

下面是TLS数据结构的定义

typedef struct _IMAGE_TLS_DIRECTORY
{
          DWORD StartAddressOfRawData;
          DWORD EndAddressOfRawData;
          DWORD AddressOfIndex;
          DWORD AddressOfCallBacks;  //PIMAGE_TLS_CALLBACK*
          DWORD SizeOfZeroFill;
          DWORD Characteristics;
}IMAGE_TLS_DIRECTORY;

AddressOfCallBacks是一个数组，表示可以有多个TLS回调函数，所谓的TLS回调函数，就是当创建/终止进程的线程时会自动调用的执行的函数。

创建进程的主线程也会自动调用回调函数，且其调用执行先于EP代码，反调试技术利用的就是TLS回调函数这一特性。

回调函数定义如下

typedef VOID 
(NTAPI *PIMAGE_TLS_CALLBACK)(
         PVOID DllHandle,
         DOWRD Reason,  //DLL_PROCESS_ATTACH,DLL_THREAD_ATTACH,DLL_THREAD_DETACH,DLL_PROCESS_DETACH
         PVOID Reserved
); 

进程调用main前，已注册的TLS回调函数会被调用执行，此时Reason为DLL_PROCESS_ATTACH

之后创建线程，结束线程，进程结束都会调用TLS回调函数，进程周期内TLS回调函数会被调用4次。

 

#include "stdafx.h"
#include<windows.h>
#include "tlhelp32.h"


#pragma comment(linker, "/INCLUDE:__tls_used")
VOID NTAPI TLS_CALLBACK(PVOID DllHandle,DWORD Reason,DWORD Reserved)
{
    DWORD Flag;
    __asm{
        mov eax,fs:[0x30]
        movzx eax,BYTE PTR DS:[eax+2]  //PEB.BingDebugged
        mov Flag,eax
    }
    if(Flag==1)
    {
        MessageBox(NULL,L"Error",L"Error",1);
        ULONG nProcessID = 0;
        HWND  hFindWindow = FindWindow(NULL,L"OLLYDBG");
        ::GetWindowThreadProcessId( hFindWindow, &nProcessID );
        HANDLE hProcessHandle = ::OpenProcess( PROCESS_TERMINATE, FALSE,nProcessID );
        TerminateProcess( hProcessHandle, 4 );
        ExitProcess(0);
    }
    else
    {
        MessageBox(NULL,L"OK",L"OK",1);
    }
}


#pragma  data_seg(".CRT$XLX")
    PIMAGE_TLS_CALLBACK pTLS_CALLBACKs[] ={(PIMAGE_TLS_CALLBACK)TLS_CALLBACK,0};
#pragma data_seg()


int _tmain(int argc, _TCHAR* argv[])
{
    MessageBox(NULL,L"HelloWorld",L"Exit",1);
}

这里就是利用TLS回调函数检测是否处于调试状态