《Windows核心编程》---CAPIHook类

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封装CAPIHook类:(某本书的笔记)

 

1HOOK所有模块

HOOK一个进程对某个API的调用时,不仅要修改主模块的导入表,还必须遍历此进程的所有模块,替换掉每个对目标API的调用:

void CAPIHook::ReplaceIATEntryInOneMod(LPSTR pszExportMod, PROC pfnCurrent,

                            PROC pfnNew, HMODULE hModCaller)

{

       //取得模块的导入表(import descriptor)的首地址

       //ImageDirectoryEntryToData函数可以返回导入表地址

       ULONG ulSize;

       PIMAGE_IMPORT_DESCRIPTOR pImportDesc =

              (PIMAGE_IMPORT_DESCRIPTOR)::ImageDirectoryEntryToData(hModCaller, TRUE,

                                                                             IMAGE_DIRECTORY_ENTRY_IMPORT, &ulSize);

       if(pImportDesc == NULL)      //这个模块没有导入表项

              return;  

       //查找包含pszExportMod模块中函数导入信息的导入表项

       while(pImportDesc->Name != 0)

       {

              LPSTR pszMod = (LPSTR)((DWORD)hModCaller + pImportDesc->Name);

              if (lstrcmpiA(pszMod, pszExportMod) == 0)   //找到

              {

                     break;

              }

              pImportDesc++;

       }

 

       if (pImportDesc->Name == 0)    //hModCaller模块没有从pszExportMod模块导入任何函数

       {

              return;

       }

 

       //取得调用者的导入地址表(import address table, IAT)

       PIMAGE_THUNK_DATA pThunk = (PIMAGE_THUNK_DATA)(pImportDesc->FirstThunk +

                                                                             (DWORD)hModCaller);

       //查找我们要HOOK的函数,将它的地址用新函数的地址替换掉

       while (pThunk->u1.Function)

       {

              //lpAddr指向的内存保存了函数的地址

              PDWORD lpAddr = (PDWORD)&(pThunk->u1.Function);

              if (*lpAddr == (DWORD)pfnCurrent)

              {

                     //修改页的保护属性

                     DWORD dwOldProtect;

                     MEMORY_BASIC_INFORMATION mbi;

                     ::VirtualQuery(lpAddr, &mbi, sizeof(mbi));

                     ::VirtualProtect(lpAddr, sizeof(DWORD), PAGE_READWRITE, &dwOldProtect);

 

                     //修改内存地址,相当于"lpAddr = (DWORD)pfnNew;"

                     ::WriteProcessMemory(::GetCurrentProcess(), lpAddr,

                                   &pfnNew, sizeof(DWORD), NULL);

                     ::VirtualProtect(lpAddr, sizeof(DWORD), dwOldProtect, 0);

                     break;

              }

              pThunk++;

       }

}

 

void CAPIHook::ReplaceIATEntryInAllMods(LPSTR pszExportMod, PROC pfnCurrent,

                                                        PROC pfnNew, BOOL bExcludeAPIHookMod)

{

       //取得当前模块的句柄

       HMODULE hModThis = NULL;

       if(bExcludeAPIHookMod)

       {

              MEMORY_BASIC_INFORMATION mbi;

              if(::VirtualQuery(ReplaceIATEntryInAllMods, &mbi, sizeof(mbi)) != 0)

                     hModThis = (HMODULE)mbi.AllocationBase;

       }

 

       //取得本进程的模块列表

       HANDLE hSnap = ::CreateToolhelp32Snapshot(TH32CS_SNAPMODULE, ::GetCurrentProcessId());

 

       //遍历所有模块,分别对它们调用ReplaceIATEntryInOnMod函数,修改导入地址表

       MODULEENTRY32 me = {sizeof(MODULEENTRY32)};

       BOOL bOK = ::Module32First(hSnap, &me);

       while (bOK)

       {

              //注意,我们不HOOK当前模块的函数

              if (me.hModule != hModThis)

              {

                     ReplaceIATEntryInOneMod(pszExportMod, pfnCurrent, pfnNew, me.hModule);

              }

 

              bOK = ::Module32Next(hSnap, &me);

       }

       ::CloseHandle(hSnap);

}

ReplaceIATEntryInOneMod函数修改hModCaller模块的IAT,将所有对pfnCurrent函数的调用改为对pfnNew函数的调用,参数pszExportMod是目标API所在的模块。例如,为了将自定义的函数AceMessageBoxA替换当前模块中的MessageBoxA函数,可以调用如下:

CAPIHOOK::ReplaceIATEntryInOneMod("User32.dll",

       (PROC)AceMessageBoxA, (PROC)MessageBoxA, ::GetModuleHandle(NULL));

ReplaceIATEntryInAllMods函数修改进程内所有模块的IAT,挂钩用户指定的API函数,最后一个参数bExcludeAPIHookMod指定是否将负责HOOK API的模块排除在外。

由于CAPIHook类工作在一个单独的DLL中,为了在此模块中方便地调用原来的API函数,一般选择不HOOK当前模块的函数,即将bExcludeAPIHookMod设为TRUE

 

2)防止程序在运行期间动态加载模块

HOOK完目标进程当前所有模块之后,目标进程还可以调用LoadLibrary函数加载新的模块。为了将今后目标进程动态加载的模块也HOOK掉,我们可以默认挂钩LoadLibrary之类的函数。方法就是在代理函数中首先调用原来的LoadLibrary函数,然后再对新加载的模块调用ReplaceIATEntryInOneMod函数。

我们设替换LoadLibrary的自定义函数是HookNewlyLoadedModule。一个CAPIHook对象仅能够挂钩一个API函数,为了挂钩多个API,用户很可能申请了多个CAPIHook对象,所以,在自定义函数HookNewlyLoadedModule中,必须为每个CAPIHook对象调用ReplaceIATEntryInOneMod函数才能确保新模块中相应的IAT项被修改。因此,我们需要记录用户申请的所有CAPIHook对象的指针。

比较简单的方法是将所有CAPIHook对象连成一个链表,用一个静态变量记录下表头地址,在每个CAPIHook对象中再记录表中下一个CAPIHook对象的地址:

class CAPIHook

{

       //这两个指针用来将当前模块中所有的CAPIHook对象连在一起

       static CAPIHook *sm_pHeader;

       CAPIHook *m_pNext;

}

静态函数HookNewlyLoadedModule的实现代码如下:

void WINAPI CAPIHook::HookNewlyLoadedModule(HMODULE hModule, DWORD dwFlags)

{

       //如果一个新的模块被加载,挂钩各CAPIHook对象要求的API函数

       if((hModule != NULL) && ((dwFlags&LOAD_LIBRARY_AS_DATAFILE) == 0 ))

       {

              CAPIHook *p = sm_pHeader;

              while(p != NULL)

              {

                     ReplaceIATEntryInOneMod(p->m_pszModName, p->m_pfnOrig,

                                   p->m_pfnHook, hModule);

                     p = p->m_pNext;   

              }

       }

}

其中,dwFlagsLoadLibraryEx函数的一个附加参数,它指定了加载时采取的行动,只要它的值中不包含LOAD_LIBRARY_AS_DATAFILE标记,就说明文件要以镜像方式映射到内存中。

 

3)防止程序在运行期间动态调用API函数

并不是只有经过导入表才能调用API函数,应用程序可以在运行期间调用GetProcAddress函数取得API函数的地址再调用它,因此,我们也需要默认挂钩GetProcAddress函数。CAPIHook类的静态成员函数GetProcAddress将替换这个API

FARPROC WINAPI CAPIHook::GetProcAddress(HMODULE hModule, PCSTR pszProcName)

{

       //得到这个函数的真实地址

       FARPROC pfn = ::GetProcAddress(hModule, pszProcName);

       //看它是不是我们要hook的函数

       CAPIHook *p = sm_pHeader;

       while(p != NULL)

       {

              if(p->m_pfnOrig == pfn)

              {

                     pfn = p->m_pfnHook;

                     break;   

              }     

              p = p->m_pNext;

       }     

       return pfn;

}

 

下面是完整的CAPIHook类的实现:

=====================APIHook.h============================

#ifndef __APIHOOK_H__

#define __APIHOOK_H__

#include <windows.h>

class CAPIHook 

{

public:

       CAPIHook(LPSTR  pszModName, LPSTR pszFuncName,

                            PROC pfnHook, BOOL bExcludeAPIHookMod=TRUE);

       virtual ~CAPIHook();

       operator PROC() {return m_pfnOrig;}

 

private:

       LPSTR m_pszModName;        //导出要HOOK函数的模块的名字

       LPSTR m_pszFuncName;  //HOOK的函数的名字

       PROC m_pfnOrig;                  //API函数地址

       PROC m_pfnHook;                //HOOK后函数的地址

       BOOL m_bExcludeAPIHookMod; //是否将HOOK API的模块本身排除在外

 

private:

       static void ReplaceIATEntryInAllMods(LPSTR pszExportMod, PROC pfnCurrent,

                     PROC pfnNew, BOOL bExcludeAPIHookMod);

       static void ReplaceIATEntryInOneMod(LPSTR pszExportMod, PROC pfnCurrent,

                     PROC pfnNew, HMODULE hModCaller);

 

       //下面的代码用来解决其他模块动态加载DLL的问题

private:

       //这两个指针用来将所有的CAPIHook对象连在一起

       static CAPIHook *sm_pHeader;

       CAPIHook *m_pNext;

 

private:

       //当一个新的DLL被加载时,调用此函数

       static void WINAPI HookNewlyLoadedModule(HMODULE hModule, DWORD dwFlags);

       //用来跟踪当前进程加载新的DLL

       static HMODULE WINAPI LoadLibraryA(PCSTR pszModulePath);

       static HMODULE WINAPI LoadLibraryW(PCWSTR pszModulePath);

       static HMODULE WINAPI LoadLibraryExA(PCSTR pszModulePath, HANDLE hFile, DWORD dwFlags);

       static HMODULE WINAPI LoadLibraryExW(PCWSTR pszModulePath, HANDLE hFile, DWORD dwFlags);

       //如果请求已HOOKAPI函数,则返回用户自定义函数的地址

       static FARPROC WINAPI GetProcAddress(HMODULE hModule, PCSTR pszProcName);

 

private:

       //自动对这些函数进行挂钩

       static CAPIHook sm_LoadLibraryA;

       static CAPIHook sm_LoadLibraryW;

       static CAPIHook sm_LoadLibraryExA;

       static CAPIHook sm_LoadLibraryExW;

       static CAPIHook sm_GetProcAddress;

 

};

#endif

 

========================APIHook.cpp========================

#include "APIHook.h"

#include "Tlhelp32.h"

#include <ImageHlp.h>  //为了调用ImageDirectoryEntryToData函数

#pragma comment(lib, "ImageHlp")

 

//CAPIHook对象链表的头指针

CAPIHook *CAPIHook::sm_pHeader = NULL;

 

//////////////////////////////////////////////////////////////////////

// Construction/Destruction

//////////////////////////////////////////////////////////////////////

 

CAPIHook::CAPIHook(LPSTR pszModName, LPSTR pszFuncName,

                               PROC pfnHook, BOOL bExcludeAPIHookMod/* =TRUE */)

{

       //保存这个Hook函数的信息

       m_bExcludeAPIHookMod = bExcludeAPIHookMod;

       m_pszModName = pszModName;

       m_pszFuncName = pszFuncName;

       m_pfnHook = pfnHook;

       m_pfnOrig = ::GetProcAddress(::GetModuleHandle(pszModName), pszFuncName);

 

       //将此对象添加到链表中

       m_pNext = sm_pHeader;

       sm_pHeader = this;

       //在所有当前已加载的模块中HOOK这个函数

       ReplaceIATEntryInAllMods(m_pszModName, m_pfnOrig, m_pfnHook,

                     bExcludeAPIHookMod);

}

 

CAPIHook::~CAPIHook()

{

       //取消对所有模块中函数的HOOK

       ReplaceIATEntryInAllMods(m_pszModName, m_pfnHook, m_pfnOrig,

                     m_bExcludeAPIHookMod);

       CAPIHook *p = sm_pHeader;

       //从链表中移除此对象

       if(p == this)

       {

              sm_pHeader = p->m_pNext;

       }

       else

       {

              while(p != NULL)

              {

                     if(p->m_pNext == this)

                     {

                            p->m_pNext = this->m_pNext;

                            break;

                     }

                     p = p->m_pNext;

              }

       }

      

}

 

void CAPIHook::ReplaceIATEntryInOneMod(LPSTR pszExportMod, PROC pfnCurrent,

                                                               PROC pfnNew, HMODULE hModCaller)

{

       //取得模块的导入表(import descriptor)的首地址

       //ImageDirectoryEntryToData函数可以返回导入表地址

       ULONG ulSize;

       PIMAGE_IMPORT_DESCRIPTOR pImportDesc =

              (PIMAGE_IMPORT_DESCRIPTOR)::ImageDirectoryEntryToData(hModCaller, TRUE,

                                                                             IMAGE_DIRECTORY_ENTRY_IMPORT, &ulSize);

       if(pImportDesc == NULL)      //这个模块没有导入表项

              return;  

       //查找包含pszExportMod模块中函数导入信息的导入表项

       while(pImportDesc->Name != 0)

       {

              LPSTR pszMod = (LPSTR)((DWORD)hModCaller + pImportDesc->Name);

              if (lstrcmpi(pszMod, pszExportMod) == 0)      //找到

              {

                     break;

              }

              pImportDesc++;

       }

 

       if (pImportDesc->Name == 0)    //hModCaller模块没有从pszExportMod模块导入任何函数

       {

              return;

       }

 

       //取得调用者的导入地址表(import address table, IAT)

       PIMAGE_THUNK_DATA pThunk = (PIMAGE_THUNK_DATA)(pImportDesc->FirstThunk +

                                                                             (DWORD)hModCaller);

       //查找我们要HOOK的函数,将它的地址用新函数的地址替换掉

       while (pThunk->u1.Function)

       {

              //lpAddr指向的内存保存了函数的地址

              PDWORD lpAddr = (PDWORD)&(pThunk->u1.Function);

              if (*lpAddr == (DWORD)pfnCurrent)

              {

                     //修改页的保护属性

                     DWORD dwOldProtect;

                     MEMORY_BASIC_INFORMATION mbi;

                     ::VirtualQuery(lpAddr, &mbi, sizeof(mbi));

                     ::VirtualProtect(lpAddr, sizeof(DWORD), PAGE_READWRITE, &dwOldProtect);

 

                     //修改内存地址,相当于"lpAddr = (DWORD)pfnNew;"

                     ::WriteProcessMemory(::GetCurrentProcess(), lpAddr,

                                   &pfnNew, sizeof(DWORD), NULL);

                     ::VirtualProtect(lpAddr, sizeof(DWORD), dwOldProtect, 0);

                     break;

              }

              pThunk++;

       }

}

 

void CAPIHook::ReplaceIATEntryInAllMods(LPSTR pszExportMod, PROC pfnCurrent,

                                                        PROC pfnNew, BOOL bExcludeAPIHookMod)

{

       //取得当前模块的句柄

       HMODULE hModThis = NULL;

       if(bExcludeAPIHookMod)

       {

              MEMORY_BASIC_INFORMATION mbi;

              if(::VirtualQuery(ReplaceIATEntryInAllMods, &mbi, sizeof(mbi)) != 0)

                     hModThis = (HMODULE)mbi.AllocationBase;

       }

 

       //取得本进程的模块列表

       HANDLE hSnap = ::CreateToolhelp32Snapshot(TH32CS_SNAPMODULE, ::GetCurrentProcessId());

 

       //遍历所有模块,分别对它们调用ReplaceIATEntryInOnMod函数,修改导入地址表

       MODULEENTRY32 me = {sizeof(MODULEENTRY32)};

       BOOL bOK = ::Module32First(hSnap, &me);

       while (bOK)

       {

              //注意,我们不HOOK当前模块的函数

              if (me.hModule != hModThis)

              {

                     ReplaceIATEntryInOneMod(pszExportMod, pfnCurrent, pfnNew, me.hModule);

              }

 

              bOK = ::Module32Next(hSnap, &me);

       }

       ::CloseHandle(hSnap);

}

 

//挂钩LoadLibraryGetProcAddress函数,以便在这些函数被调用以后,挂钩的函数也能够被正确的处理

CAPIHook CAPIHook::sm_LoadLibraryA("Kernel32.dll", "LoadLibraryA",

                                                           (PROC)CAPIHook::LoadLibraryA, TRUE);

CAPIHook CAPIHook::sm_LoadLibraryW("Kernel32.dll", "LoadLibraryW",

                                                           (PROC)CAPIHook::LoadLibraryW, TRUE);

CAPIHook CAPIHook::sm_LoadLibraryExA("Kernel32.dll", "LoadLibraryExA",

                                                                (PROC)CAPIHook::LoadLibraryExA, TRUE);

CAPIHook CAPIHook::sm_LoadLibraryExW("Kernel32.dll", "LoadLibraryExW",

                                                                (PROC)CAPIHook::LoadLibraryExW, TRUE);

CAPIHook CAPIHook::sm_GetProcAddress("Kernel32.dll", "GetProcAddress",

                                                                (PROC)CAPIHook::GetProcAddress, TRUE);

 

void WINAPI CAPIHook::HookNewlyLoadedModule(HMODULE hModule, DWORD dwFlags)

{

       //如果一个新的模块被加载,挂钩各CAPIHook对象要求的API函数

       if((hModule != NULL) && ((dwFlags&LOAD_LIBRARY_AS_DATAFILE) == 0))

       {

              CAPIHook *p = sm_pHeader;

              while (p != NULL)

              {

                     ReplaceIATEntryInOneMod(p->m_pszModName, p->m_pfnOrig,

                                                                      p->m_pfnHook, hModule);

                     p = p->m_pNext;

              }

       }

}

 

HMODULE WINAPI CAPIHook::LoadLibraryA(PCSTR pszModulePath)

{

       HMODULE hModule = ::LoadLibraryA(pszModulePath);

       HookNewlyLoadedModule(hModule, 0);

       return hModule;

}

 

HMODULE WINAPI CAPIHook::LoadLibraryW(PCWSTR pszModulePath)

{

       HMODULE hModule = ::LoadLibraryW(pszModulePath);

       HookNewlyLoadedModule(hModule, 0);

       return hModule;

}

 

HMODULE WINAPI CAPIHook::LoadLibraryExA(PCSTR pszModulePath, HANDLE hFile, DWORD dwFlags)

{

       HMODULE hModule = ::LoadLibraryExA(pszModulePath, hFile, dwFlags);

       HookNewlyLoadedModule(hModule, dwFlags);

       return hModule;

}

 

HMODULE WINAPI CAPIHook::LoadLibraryExW(PCWSTR pszModulePath, HANDLE hFile, DWORD dwFlags)

{

       HMODULE hModule = ::LoadLibraryExW(pszModulePath, hFile, dwFlags);

       HookNewlyLoadedModule(hModule, dwFlags);

       return hModule;

}

 

FARPROC WINAPI CAPIHook::GetProcAddress(HMODULE hModule, PCSTR pszProcName)

{

       //得到函数的真实地址

       FARPROC pfn = ::GetProcAddress(hModule, pszProcName);

       //看它是否我们要HOOK的函数

       CAPIHook *p = sm_pHeader;

       while(p != NULL)

       {

              if (p->m_pfnOrig == pfn)

              {

                     pfn = p->m_pfnHook;

                     break;

              }

              p = p->m_pNext;

       }

       return pfn;

}