/////////////////////////////////////////////////////////////////////////
//
// hookapi.c
//
// Date   : 04/18/99
//
// oshj add 20040916 有這些現成的函數真爽，原作者好像是個臺灣同胞
//
/////////////////////////////////////////////////////////////////////////

#include <windows.h>
#include "hookapi.h"
#include "string.h"

//#pragma comment(lib, "k32lib.lib")

//extern BOOL g_bCanWrite;

/////////////////////////////////////////////////////////////////////////
// Hook Api
/////////////////////////////////////////////////////////////////////////
FARPROC WINAPI NHGetFuncAddress(HINSTANCE hInst, LPCSTR lpMod, LPCSTR lpFunc)
{
	HMODULE hMod;
	FARPROC procFunc;

	if (NULL != lpMod)
	{
		hMod=GetModuleHandle(lpMod);
		procFunc = GetProcAddress(hMod,lpFunc);
	}
	else
	{
		procFunc = GetProcAddress(hInst,lpFunc);

	}
	
	return  procFunc;
}

void MakeJMPCode(LPBYTE lpJMPCode, LPVOID lpCodePoint)
{
	BYTE temp;
	WORD wHiWord = HIWORD(lpCodePoint);
	WORD wLoWord = LOWORD(lpCodePoint);
	WORD wCS;

	_asm						// 取當前選擇符﹒
	{
		push ax;
		push cs;
		pop  ax;
		mov  wCS, ax;
		pop  ax;
	};
	
	lpJMPCode[0] = 0xea;		// 填入 JMP 指令的機器碼﹒

	temp = LOBYTE(wLoWord);		// -------------------------
	lpJMPCode[1] = temp;
	temp = HIBYTE(wLoWord);
	lpJMPCode[2] = temp;		// 填入地址﹒在內存中的順序為；
	temp = LOBYTE(wHiWord);		// Point: 0x1234
	lpJMPCode[3] = temp;		// 內存： 4321
	temp = HIBYTE(wHiWord);
	lpJMPCode[4] = temp;		// -------------------------
	
	temp = LOBYTE(wCS);			// 填入選擇符﹒
	lpJMPCode[5] = temp;
	temp = HIBYTE(wCS);
	lpJMPCode[6] = temp;

	return;
}

void HookWin32Api(LPAPIHOOKSTRUCT lpApiHook, int nSysMemStatus)
{
	
	DWORD  dwReserved;
	DWORD  dwTemp;
	BYTE   bWin32Api[5];

	bWin32Api[0] = 0x00; 

	//TextOut(GetDC(GetActiveWindow()),2,15,"here",20);

	// 取得被攔截函數地址﹒
	if(lpApiHook->lpWinApiProc == NULL)
	{	
		lpApiHook->lpWinApiProc = (LPVOID)NHGetFuncAddress(lpApiHook->hInst, lpApiHook->lpszApiModuleName,lpApiHook->lpszApiName);
		if (lpApiHook->dwApiOffset != 0)
			lpApiHook->lpWinApiProc = (LPVOID)((DWORD)lpApiHook->lpWinApiProc + lpApiHook->dwApiOffset);
	}
	// 取得替代函數地址﹒
	if(lpApiHook->lpHookApiProc == NULL)
	{
		lpApiHook->lpHookApiProc = (LPVOID)NHGetFuncAddress(lpApiHook->hInst,
			lpApiHook->lpszHookApiModuleName,lpApiHook->lpszHookApiName);
	}
	// 形成 JMP 指令﹒
	if (lpApiHook->HookApiFiveByte[0] == 0x00)
	{
		MakeJMPCode(lpApiHook->HookApiFiveByte, lpApiHook->lpHookApiProc);
	}

	if (!VirtualProtect(lpApiHook->lpWinApiProc, 16, PAGE_READWRITE,
			&dwReserved))
	{
		MessageBox(NULL, "VirtualProtect-READWRITE", NULL, MB_OK);
		return;
	}
	
	if (nSysMemStatus == HOOK_NEED_CHECK)
	{
		memcpy(lpApiHook->lpWinApiProc, (LPVOID)lpApiHook->HookApiFiveByte,BUFFERLEN);
	}
	else
	{
		if (lpApiHook->WinApiFiveByte[0] == 0x00)			// 判斷是否已經攔截﹒
		{
			// 否﹒
			// 備份 API 函數頭五個字節﹒
			memcpy(lpApiHook->WinApiFiveByte,(LPVOID)lpApiHook->lpWinApiProc,BUFFERLEN);
			// 判斷是否重複攔截﹒(即判斷備份的頭五個字節是否為形成的JMP指令)
			if (strncmp((const char*)lpApiHook->WinApiFiveByte, 
				(const char*)lpApiHook->HookApiFiveByte, BUFFERLEN) == 0)
			{
				// 恢復備份的字節﹒
				memcpy(lpApiHook->WinApiFiveByte,(LPVOID)lpApiHook->WinApiBakByte,BUFFERLEN);
			}
		}
		else
		{
			// 是﹒
			memcpy(bWin32Api,(LPVOID)lpApiHook->lpWinApiProc,BUFFERLEN);
		}

		if (strncmp((const char*)bWin32Api, (const char*)lpApiHook->HookApiFiveByte,
			BUFFERLEN) != 0)
		{
			// 將 JMP 指定填入 API 函數的頭﹒
			memcpy(lpApiHook->lpWinApiProc, (LPVOID)lpApiHook->HookApiFiveByte,BUFFERLEN);
		}
	}

	if (!VirtualProtect(lpApiHook->lpWinApiProc, 16, dwReserved, &dwTemp))
	{
		MessageBox(NULL, "VirtualProtect-RESTORE", NULL, MB_OK);
		return;
	}
	
}

void RestoreWin32Api(LPAPIHOOKSTRUCT lpApiHook, int nSysMemStatus)
{
	DWORD dwReserved;
	DWORD dwTemp;

	if (lpApiHook->lpWinApiProc == NULL)
		return;

	if (!VirtualProtect(lpApiHook->lpWinApiProc, 16, PAGE_READWRITE,
			&dwReserved))
	{
		MessageBox(NULL, "VirtualProtect-READWRITE", NULL, MB_OK);
		return;
	}
	memcpy(lpApiHook->lpWinApiProc,(LPVOID)lpApiHook->WinApiFiveByte,BUFFERLEN);
	if (!VirtualProtect(lpApiHook->lpWinApiProc, 16, dwReserved, &dwTemp))
	{
		MessageBox(NULL, "VirtualProtect-RESTORE", NULL, MB_OK);
		return;
	}
}