狸猫换太子：动态替换WinCE的原生驱动
//=====================================================================
//TITLE:
// 狸猫换太子：动态替换WinCE的原生驱动！
//AUTHOR:
// norains
//DATE:
// Friday 23-April-2010
//Environment:
// Windows CE 5.0 + TCC7901
//=====================================================================
大家应该都知道，WinCE系统的驱动是可以非常方便地动态加载和卸载的（如果对此不清楚，可以参考我之前写的两篇文章。《WinCE驱动的动态加载》：http://blog.csdn.net/norains/archive/2010/02/22/5316923.aspx《WinCE驱动的动态卸载》：http://blog.csdn.net/norains/archive/2010/04/22/5514351.aspx），如果我们善加利用，完全可以神不知鬼不觉地进行狸猫换太子--不必重新编译系统，就可以在应用程序完全不知情地情况下，将原生驱动偷梁换柱成我们自己的冒牌货！
听起来很有意思，是吧？那么，让我们开始这次奇妙的旅程吧。
能达到的目标才有动力，这次我们拿WinCE设备最常用的最基本的串口驱动开刀。我们要做的事情也很简单，如果通过Read读取回来的字符超过五个，那么我们就将最前面的五个字符替换为"abcde"。
如果要达成这个目标，我们需要两个程序：
1． 伪驱动DLL。它负责替换读取回来的数据
2． 驱动加载程序。
第二点比较简单，我们先来看看第一点。
首先我们来了解一下WinCE驱动的基本情况。WinCE的驱动，说白了，就是一个dll文件。它和普通的dll唯一不同的是，它规定了导出函数的形式，比如XXX_Init，XXX_Deinit等等。其中的XXX，是不同驱动的前缀，就像串口驱动为COM_Init一样。更为严格的是，像COM_Init这样的函数，无论是返回值，还是形参的类型乃至于个数，都是规定死的，否则WinCE不会正常加载。
而在这一框框条条之下，带给我们的是另外的一种机会：我们的伪驱动向上实现微软规定的接口，向下则调用原生的驱动。
听起来是不是有点迷糊？没关系，我们以COM_Read函数举个例子。
我们的伪驱动名为FakeDriver.dll，导出了一个函数叫COM_Read。我这里的平台是Telechips的TCC7901，它的驱动文件为tcc_serial.dll。接下来需要做的是，从tcc_serial.dll中获得其COM_Read的地址，以方便我们在伪驱动中调用。
对于大家来说，对于下面调用dll函数的代码应该不会陌生：
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//显式加载DLL文件
g_hCoreDll = LoadLibrary(TEXT("tcc_serial.dll"));
...
//获取DLL文件的COM_Read函数地址
typedef ULONG (WINAPI *DLL_COM_READ)(HANDLE pHead,PUCHAR pTargetBuffer,ULONG BufferLength);
DLL_COM_READ DLL_COM_Read = (DLL_COM_READ)GetProcAddress(g_hCoreDll, _T("COM_Read"));
...
ULONG COM_Read(HANDLE pHead,PUCHAR pTargetBuffer,ULONG BufferLength)
{
//直接调用DLL的COM_Read函数
return DLL_COM_Read(pHead,pTargetBuffer,BufferLength);
}
没错，就是这么简单。我们的伪驱动，其实只是在原生驱动之上封装了一层，骨子里还是调用的原生驱动。只不过我们可以在这封装的一层中，可以做太多的事情了。对于本文前面的目标，我们的伪驱动的代码完整实现如下：
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#include "serpriv.h"
//------------------------------------------------------------
//导出函数的定义
typedef HANDLE (WINAPI *DLL_COM_INIT)(ULONG Identifier);
typedef BOOL (WINAPI *DLL_COM_DEINIT)(PHW_INDEP_INFO pSerialHead);
typedef BOOL (WINAPI *DLL_COM_IOCONTROL)(PHW_OPEN_INFO pOpenHead,DWORD dwCode, PBYTE pBufIn,DWORD dwLenIn, PBYTE pBufOut, DWORD dwLenOut,PDWORD pdwActualOut);
typedef void (WINAPI *DLL_COM_PRECLOSE)(PHW_OPEN_INFO pOpenHead);
typedef BOOL (WINAPI *DLL_COM_PREDEINIT)(PHW_INDEP_INFO pSerialHead);
typedef HANDLE (WINAPI *DLL_COM_OPEN)(HANDLE pHead, DWORD AccessCode,DWORD ShareMode);
typedef BOOL (WINAPI *DLL_COM_CLOSE)(PHW_OPEN_INFO pOpenHead);
typedef BOOL (WINAPI *DLL_COM_POWERDOWN)(HANDLE pHead);
typedef BOOL (WINAPI *DLL_COM_POWERUP)(HANDLE pHead);
typedef ULONG (WINAPI *DLL_COM_READ)(HANDLE pHead,PUCHAR pTargetBuffer,ULONG BufferLength);
typedef ULONG (WINAPI *DLL_COM_SEEK)(HANDLE pHead,LONG Position,DWORD Type);
typedef ULONG (WINAPI *DLL_COM_WRITE)(HANDLE pHead,PUCHAR pSourceBytes,ULONG NumberOfBytes);
//----------------------------------------------------------
//全局变量
DLL_COM_INIT DLL_COM_Init = NULL;
DLL_COM_DEINIT DLL_COM_Deinit = NULL;
DLL_COM_IOCONTROL DLL_COM_IOControl = NULL;
DLL_COM_PRECLOSE DLL_COM_PreClose = NULL;
DLL_COM_PREDEINIT DLL_COM_PreDeinit = NULL;
DLL_COM_OPEN DLL_COM_Open = NULL;
DLL_COM_CLOSE DLL_COM_Close = NULL;
DLL_COM_POWERDOWN DLL_COM_PowerDown = NULL;
DLL_COM_POWERUP DLL_COM_PowerUp = NULL;
DLL_COM_READ DLL_COM_Read = NULL;
DLL_COM_SEEK DLL_COM_Seek = NULL;
DLL_COM_WRITE DLL_COM_Write = NULL;
HINSTANCE g_hCoreDll = NULL;
//----------------------------------------------------------
//获取所有导出函数的地址
BOOL InitFuncAddr()
{
BOOL bRes = FALSE;
__try
{
g_hCoreDll = LoadLibrary(TEXT("tcc_serial.dll"));
if (g_hCoreDll == NULL)
{
__leave;
}
DLL_COM_Init = (DLL_COM_INIT)GetProcAddress(g_hCoreDll, _T("COM_Init"));
if(DLL_COM_Init == NULL)
{
__leave;
}
DLL_COM_Deinit = (DLL_COM_DEINIT)GetProcAddress(g_hCoreDll, _T("COM_Deinit"));
if(DLL_COM_Deinit == NULL)
{
__leave;
}
DLL_COM_IOControl = (DLL_COM_IOCONTROL)GetProcAddress(g_hCoreDll, _T("COM_IOControl"));
if(DLL_COM_IOControl == NULL)
{
__leave;
}
DLL_COM_PreClose = (DLL_COM_PRECLOSE)GetProcAddress(g_hCoreDll, _T("COM_PreClose"));
if(DLL_COM_PreClose == NULL)
{
__leave;
}
DLL_COM_PreDeinit = (DLL_COM_PREDEINIT)GetProcAddress(g_hCoreDll, _T("COM_PreDeinit"));
if(DLL_COM_PreDeinit == NULL)
{
__leave;
}
DLL_COM_Open = (DLL_COM_OPEN)GetProcAddress(g_hCoreDll, _T("COM_Open"));
if(DLL_COM_Open == NULL)
{
__leave;
}
DLL_COM_Close = (DLL_COM_CLOSE)GetProcAddress(g_hCoreDll, _T("COM_Close"));
if(DLL_COM_Close == NULL)
{
__leave;
}
DLL_COM_PowerDown = (DLL_COM_POWERDOWN)GetProcAddress(g_hCoreDll, _T("COM_PowerDown"));
if(DLL_COM_PowerDown == NULL)
{
__leave;
}
DLL_COM_PowerUp = (DLL_COM_POWERUP)GetProcAddress(g_hCoreDll, _T("COM_PowerUp"));
if(DLL_COM_PowerUp == NULL)
{
__leave;
}
DLL_COM_Read = (DLL_COM_READ)GetProcAddress(g_hCoreDll, _T("COM_Read"));
if(DLL_COM_Read == NULL)
{
__leave;
}
DLL_COM_Seek = (DLL_COM_SEEK)GetProcAddress(g_hCoreDll, _T("COM_Seek"));
if(DLL_COM_Seek == NULL)
{
__leave;
}
DLL_COM_Write = (DLL_COM_WRITE)GetProcAddress(g_hCoreDll, _T("COM_Write"));
if(DLL_COM_Write == NULL)
{
__leave;
}
bRes = TRUE;
}
__finally
{
if(bRes == FALSE)
{
if(g_hCoreDll != NULL)
{
FreeLibrary(g_hCoreDll);
}
}
}
return bRes;
}
BOOL WINAPI DllEntry(HANDLE hInstDll, DWORD dwReason, LPVOID lpvReserved)
{
switch ( dwReason )
{
case DLL_PROCESS_ATTACH:
break;
}
return TRUE;
}
HANDLE COM_Init(ULONG Identifier)
{
if(InitFuncAddr() != FALSE)
{
RETAILMSG(TRUE,(TEXT("InitFuncAddr Succeeded\r\n")));
return DLL_COM_Init(Identifier);
//return TRUE;
}
else
{
RETAILMSG(TRUE,(TEXT("InitFuncAddr Failed\r\n")));
return FALSE;
}
}
BOOL COM_Deinit(PHW_INDEP_INFO pSerialHead)
{
BOOL bRes = DLL_COM_Deinit(pSerialHead);
if(g_hCoreDll != NULL)
{
FreeLibrary(g_hCoreDll);
}
RETAILMSG(TRUE,(TEXT("COM_Deinit\r\n")));
return bRes;
}
BOOL COM_IOControl(PHW_OPEN_INFO pOpenHead,
DWORD dwCode, PBYTE pBufIn,
DWORD dwLenIn, PBYTE pBufOut, DWORD dwLenOut,
PDWORD pdwActualOut)
{
return DLL_COM_IOControl(pOpenHead,dwCode,pBufIn,dwLenIn,pBufOut,dwLenOut,pdwActualOut);
}
void COM_PreClose(PHW_OPEN_INFO pOpenHead)
{
DLL_COM_PreClose(pOpenHead);
}
BOOL COM_PreDeinit(PHW_INDEP_INFO pSerialHead)
{
return DLL_COM_PreDeinit(pSerialHead);
}
HANDLE COM_Open(HANDLE pHead, DWORD AccessCode,DWORD ShareMode)
{
return DLL_COM_Open(pHead,AccessCode,ShareMode);
}
BOOL COM_Close(PHW_OPEN_INFO pOpenHead)
{
return DLL_COM_Close(pOpenHead);
}
BOOL COM_PowerDown(HANDLE pHead)
{
return DLL_COM_PowerDown(pHead);
}
BOOL COM_PowerUp(HANDLE pHead)
{
return DLL_COM_PowerUp(pHead);
}
ULONG COM_Read(HANDLE pHead,PUCHAR pTargetBuffer,ULONG BufferLength)
{
ULONG ulRead = DLL_COM_Read(pHead,pTargetBuffer,BufferLength);
//将前面的五个字符替换为abced
if(ulRead > 5)
{
pTargetBuffer[0] = 'a';
pTargetBuffer[1] = 'b';
pTargetBuffer[2] = 'c';
pTargetBuffer[3] = 'd';
pTargetBuffer[4] = 'e';
}
return ulRead;
}
ULONG COM_Seek(HANDLE pHead,LONG Position,DWORD Type)
{
return DLL_COM_Seek(pHead,Position,Type);
}
ULONG COM_Write(HANDLE pHead,PUCHAR pSourceBytes,ULONG NumberOfBytes)
{
return DLL_COM_Write(pHead,pSourceBytes,NumberOfBytes);
}
代码中的DLL_COM_XXX函数其实全部都是原生驱动的导出函数，如果我们将COM_Read的替换代码注释掉，那么这个伪驱动的表现将和原生驱动一模一样，没有任何区别。
伪驱动DLL已经完成，剩下的就是临门一脚。先看看TCC7901的COM1的注册表：
如图中所示，为了要让我们的伪驱动能够正常加载，需要将注册表的dll字段更改为我们伪驱动的文件名。
所以，加载的应用程序就只有如下几行（代码中所提到的Unload函数，请参考本文开头的两篇文章）：
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//卸载原来的COM1驱动
Unload(TEXT("COM1:"));
//更改注册表中DLL的文件名
CReg reg;
reg.Create(HKEY_LOCAL_MACHINE,TEXT("Drivers\\BuiltIn\\Serial1"));
reg.SetSZ(TEXT("Dll"),TEXT("FakeDriver.dll"));
//动态加载伪驱动
ActivateDeviceEx(TEXT("Drivers\\BuiltIn\\Serial1",NULL,0,pParam);
最后我们需要做的就是，将伪驱动FakeDriver.dll拷贝到windows文件夹，运行我们的加载程序，就可以用如下代码进行测试：
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HANDLE hCom = CreateFile(TEXT("COM1:"),GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);
std::vector<BYTE> vtBuf(MAX_PATH,0);
DWORD dwRead = 0;
BOOL bRes = ReadFile(hCom,&vtBuf[0],vtBuf.size(),&dwRead,NULL);
CloseHandle(hCom);
如果不出意外的话，那么读取回来的数据前面五个字符将是我们所期望的abcde！
本文所提到的伪驱动源代码可于此下载：http://download.csdn.net/source/2275520