Hide your DebugPort in ring0

  标 题: 【原创】Hide your DebugPort in ring0
作 者: wowelf
时 间: 2009-01-26,11:00:30
链 接: http://bbs.pediy.com/showthread.php?t=80971

一个程序被ring3调试器调试时，有很多的调试特征可以检测，本论坛也有专门的帖子详细论述，但有个非常根本的标志ring3也是可以检测的比较少人提及，那就是_EPROCESS.DebugPort。DebugPort对于ring3调试器来说非常重要，没有它正常的ring3调试是无法进行的。当然要检测这个标志的前提是程序能够读取ring0内存，在XP以上的系统有个非常简单的方法就是使用ZwSystemDebugControl的SysDbgReadVirtualMemory方法，我们也可以map physicalmemory来操作。检测DebugPort之前首先要得到进程的eprocess地址，这可以通过ZwQuerySystemInformation的SystemHandleInformation方法得到，也可以直接搜索ring0内存的eprocess结构。

   对于ring3直接检测DebugPort，我们可以通过禁止该进程访问ring0内存来对付，但是目标一旦使用驱动来检测，那么就非常麻烦了。下面介绍一种隐藏_EPROCESS.DebugPort的方法，这种方法的基本思路是，将一个正常被调试进程的DebugPort置零后，修正所有受影响的函数，使我们的调试器能够正常进行。这些函数如下：
    PspCreateProcess、MmCreatePeb 进程创建，设置DebugPort
    DbgkCreateThread 发送线程或者进程创建的调试信息
    KiDispatchException、DbgkForwardException和DbgkpQueueMessage 发送异常调试信息
    PspExitThread、DbgkExitThread和DbgkExitProcess 发送线程退出、进程退出的调试信息
    DbgkMapViewOfSection和DbgkUnMapViewOfSection 发送映像装载卸载调试信息
    DbgkpSetProcessDebugObject和DbgkpMarkProcessPeb 当调试器附加进程时设置DebugPort   

     这类函数非常多的，如果都HOOK处理的话，那太恐怖了，这里使用一个非常简单的办法：偷龙转凤。我们看系统访问DebugPort的代码都是这样的（XP）
         8b89bc000000    mov     ecx,dword ptr [ecx+0BCh] //0BCh就是DebugPort的偏移

     我们可以把DebugPort转移到_EPROCESS的另外一个地方，比如我使用+0x070 CreateTime，它是纪录进程创建时间的，进程创建之后，在进程退出前系统不会对它进行任何修改，而且我们修改后对系统或进程没有任何影响。这样我们可以把上面的代码改成这样
         8b8970000000    mov     ecx,dword ptr [ecx+070h] //指向CreateTime，实际的DebugPort已经被移到这里
     只需要修改一个字节，非常简单。

     当然这种方法最麻烦的地方就是定位引用到DebugPort的函数（本人仅仅针对不同的XP系统制作特征码都累到吐血），这些函数都是不导出的，如果是特定系统，最简单的方法就是WinDbg->uf *** 直接找地址硬编码，只需要几分钟时间。
    

代码:

BOOLEAN InitHackAddress()
{
  _SEH_TRY
  {
    g_KernelBase = GetKernelBaseAndSize( &g_KernelSize );      
    g_HackPspCreateProcess = SearchHackPspCreateProcess( &g_NopPspCreateProcess.Address );
    g_HackKiDispatchException = SearchKiDispatchException( g_KernelBase,g_KernelSize );  
    g_HackDbgkpQueueMessage = SearchDbgkpQueueMessage( g_KernelBase,g_KernelSize );
    g_HackDbgkCreateThread = SearchDbgkCreateThread( g_KernelBase,g_KernelSize );    
    SearchDbgkNotifyRoutine( g_KernelBase,g_KernelSize );
    g_HackPspExitThread = SearchPspExitThread();  
    g_HackMmCreatePeb = SearchMmCreatePeb( g_HackPspCreateProcess );
    SearchDbgkpSetProcessDebugObject( g_KernelBase,g_KernelSize );
    if( g_HackDbgkpSetProcessDebugObject[3] )
      g_HackDbgkpMarkProcessPeb = SearchDbgkpMarkProcessPeb( g_HackDbgkpSetProcessDebugObject[3] ) ;
    
    if( g_NopPspCreateProcess.Address != 0 ){
      RtlFillMemory( g_NopPspCreateProcess.NopCode,sizeof(g_NopPspCreateProcess.NopCode),0x90 ); 
      g_NopPspCreateProcess.Size = 9;
      RtlCopyMemory( g_NopPspCreateProcess.OrigCode,(PVOID)g_NopPspCreateProcess.Address,g_NopPspCreateProcess.Size );
    }

    if( g_NopDbgkForwardException.Address != 0 ){      
      RtlFillMemory( g_NopDbgkForwardException.NopCode,sizeof(g_NopDbgkForwardException.NopCode),0x90 );
      RtlCopyMemory( g_NopDbgkForwardException.OrigCode,(PVOID)g_NopDbgkForwardException.Address,g_NopDbgkForwardException.Size );
    }

    if( g_NopDbgkExitThread.Address != 0 ){      
      RtlFillMemory( g_NopDbgkExitThread.NopCode,sizeof(g_NopDbgkExitThread.NopCode),0x90 );
      RtlCopyMemory( g_NopDbgkExitThread.OrigCode,(PVOID)g_NopDbgkExitThread.Address,g_NopDbgkExitThread.Size );
    }

    if( g_NopDbgkExitProcess.Address != 0 ){
      RtlFillMemory( g_NopDbgkExitProcess.NopCode,sizeof(g_NopDbgkExitProcess.NopCode),0x90 );
      RtlCopyMemory( g_NopDbgkExitProcess.OrigCode,(PVOID)g_NopDbgkExitProcess.Address,g_NopDbgkExitProcess.Size );
    }

    if( g_NopDbgkMapViewOfSection.Address != 0){
      RtlFillMemory( g_NopDbgkMapViewOfSection.NopCode,sizeof(g_NopDbgkMapViewOfSection.NopCode),0x90 );
      RtlCopyMemory( g_NopDbgkMapViewOfSection.OrigCode,(PVOID)g_NopDbgkMapViewOfSection.Address,g_NopDbgkMapViewOfSection.Size );
    }

    if( g_NopDbgkUnMapViewOfSection.Address != 0 ){
      RtlFillMemory( g_NopDbgkUnMapViewOfSection.NopCode,sizeof(g_NopDbgkUnMapViewOfSection.NopCode),0x90 );
      RtlCopyMemory( g_NopDbgkUnMapViewOfSection.OrigCode,(PVOID)g_NopDbgkUnMapViewOfSection.Address,g_NopDbgkUnMapViewOfSection.Size );
    }     
    
    
  }
  _SEH_HANDLER
  {    
    DbgPrint( "InitHackAddress Exception!\n" );
  }

  return ( g_HackPspCreateProcess != 0 &&
         g_HackKiDispatchException != 0 &&
       g_HackDbgkForwardException != 0 &&
       g_HackDbgkpQueueMessage != 0 && 
       g_NopPspCreateProcess.Address != 0 &&
       g_NopDbgkForwardException.Address != 0 &&
       g_HackDbgkCreateThread != 0 &&
       g_HackDbgkExitThread != 0 &&
       g_NopDbgkExitThread.Address != 0 &&
       g_HackDbgkExitProcess != 0 &&
       g_NopDbgkExitProcess.Address != 0 &&
       g_HackDbgkMapViewOfSection != 0 &&
       g_NopDbgkMapViewOfSection.Address != 0 &&
       g_HackDbgkUnMapViewOfSection != 0 &&
       g_NopDbgkUnMapViewOfSection.Address != 0 &&
       g_HackPspExitThread != 0 &&
       g_HackMmCreatePeb != 0 &&
       g_HackDbgkpSetProcessDebugObject[0] != 0 &&
       g_HackDbgkpSetProcessDebugObject[1] != 0 &&
       g_HackDbgkpSetProcessDebugObject[2] != 0 &&
       g_HackDbgkpSetProcessDebugObject[3] != 0 &&
       g_HackDbgkpMarkProcessPeb != 0 );
}

代码:

 

//修改已经运行进程的DebugPort位置
BOOLEAN ChangeProcessDebugPort( BOOLEAN Hide )
{
  ULONG eProcess = (ULONG)PsInitialSystemProcess;
  PLIST_ENTRY pListHead,pListWalk;
  ULONG DebugObject;

  if( !g_bIsAddressStartup ){
    return FALSE;
  }

  pListHead = (PLIST_ENTRY)( eProcess + ACTIVE_LINKS_OFFSET );
  pListWalk = pListHead;

  _SEH_TRY
  {    
    do{
      if( pListWalk == NULL || eProcess == 0 )
        break;

      eProcess = ( (ULONG)pListWalk - ACTIVE_LINKS_OFFSET );    

      if( Hide ){

        DebugObject = *(ULONG*)( eProcess + DEBUG_PORT_OFFSET );
        *(ULONG*)( eProcess + CREATE_TIME_OFFSET ) = DebugObject;
        *(ULONG*)( eProcess + DEBUG_PORT_OFFSET ) = 0;

      }else{

        DebugObject = *(ULONG*)( eProcess + CREATE_TIME_OFFSET );
        *(ULONG*)( eProcess + DEBUG_PORT_OFFSET ) = DebugObject;
      }

      pListWalk = pListWalk->Flink;

    }while( pListWalk != pListHead );

  }
  _SEH_HANDLER
  {
    DbgPrint( "ChangeProcessDebugPort exception!\n" );
  }
  
  return TRUE;
}

代码:

BOOLEAN ModifyDebugFunction()
{
  if( !g_bIsAddressStartup ){
    return FALSE;
  }

  __asm{
    cli
    mov  eax,cr0
    and  eax,not 10000h
    mov  cr0,eax
  }

  *(ULONG*)g_HackPspCreateProcess = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackKiDispatchException = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkForwardException = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkpQueueMessage = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkCreateThread = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkExitThread = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkExitProcess = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkMapViewOfSection = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkUnMapViewOfSection = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackPspExitThread = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkpMarkProcessPeb = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackMmCreatePeb = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[0] = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[1] = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[2] = CREATE_TIME_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[3] = CREATE_TIME_OFFSET;
    

  RtlCopyMemory( (PVOID)g_NopPspCreateProcess.Address,g_NopPspCreateProcess.NopCode,g_NopPspCreateProcess.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkForwardException.Address,g_NopDbgkForwardException.NopCode,g_NopDbgkForwardException.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkExitThread.Address,g_NopDbgkExitThread.NopCode,g_NopDbgkExitThread.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkExitProcess.Address,g_NopDbgkExitProcess.NopCode,g_NopDbgkExitProcess.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkMapViewOfSection.Address,g_NopDbgkMapViewOfSection.NopCode,g_NopDbgkMapViewOfSection.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkUnMapViewOfSection.Address,g_NopDbgkUnMapViewOfSection.NopCode,g_NopDbgkUnMapViewOfSection.Size );

  __asm{
    mov  eax,cr0
    or   eax,10000h
    mov  cr0,eax
    sti
  }

  return TRUE;

}

BOOLEAN WriteBackDebugFunction()
{
  if( !g_bIsAddressStartup ){
    return FALSE;
  }

  __asm{
    cli
    mov  eax,cr0
    and  eax,not 10000h
    mov  cr0,eax
  }

  *(ULONG*)g_HackPspCreateProcess = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackKiDispatchException = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkForwardException = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkpQueueMessage = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkCreateThread = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkExitThread = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkExitProcess = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkMapViewOfSection = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkUnMapViewOfSection = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackPspExitThread = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkpMarkProcessPeb = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackMmCreatePeb = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[0] = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[1] = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[2] = DEBUG_PORT_OFFSET;
  *(ULONG*)g_HackDbgkpSetProcessDebugObject[3] = DEBUG_PORT_OFFSET;

  RtlCopyMemory( (PVOID)g_NopPspCreateProcess.Address,g_NopPspCreateProcess.OrigCode,g_NopPspCreateProcess.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkForwardException.Address,g_NopDbgkForwardException.OrigCode,g_NopDbgkForwardException.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkExitThread.Address,g_NopDbgkExitThread.OrigCode,g_NopDbgkExitThread.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkExitProcess.Address,g_NopDbgkExitProcess.OrigCode,g_NopDbgkExitProcess.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkMapViewOfSection.Address,g_NopDbgkMapViewOfSection.OrigCode,g_NopDbgkMapViewOfSection.Size );
  RtlCopyMemory( (PVOID)g_NopDbgkUnMapViewOfSection.Address,g_NopDbgkUnMapViewOfSection.OrigCode,g_NopDbgkUnMapViewOfSection.Size );

  __asm{
    mov  eax,cr0
    or   eax,10000h
    mov  cr0,eax
    sti
  }

  return TRUE;
}

     我想再啰嗦一下，上面代码大家看到很多函数有个NOPCode，这个实际上是对付线程PS_CROSS_THREAD_FLAGS_HIDEFROMDBG的，NOP掉相关地方后，就算线程被设置为ThreadHideFromDebugger也无法阻挡调试器接收调试信息。