Api Hijacking (sample included-优快云博客

something i've written for w3hackit (www.gamehackers.net),
thought some of you might find this code interesting.

hijacking api is a good way to control how external dll's manipulate a program.
you can write a universal keybind feature or even a speed hack.
but this all really comes down to how much a game depends on function imports.

normally i wouldn't use the C-lib *hides*, but i wanted to write a quick sample to explain whats going on in the background.

Code:

#include<windows.h>
#include<stdio.h>

union BaseData {
PBYTE       pImageBase;
PIMAGE_DOS_HEADER pImageHeader;
};

typedef BaseData* pBaseData;
typedef PIMAGE_FILE_HEADER pFileHeader;
typedef PIMAGE_OPTIONAL_HEADER pExtraHeader;
typedef PIMAGE_SECTION_HEADER pSectionHeader;
#define InitConsts()/
m_BaseData(*pBaseData(&pImageBase)),/
m_pFileHeader(pFileHeader(DWORD(m_BaseData.pImageBase)+DWORD(m_BaseData.pImageHeader->e_lfanew)+sizeof(DWORD))),/
m_pExtraHeader(pExtraHeader(DWORD(m_pFileHeader) + sizeof(IMAGE_FILE_HEADER))),/
m_pSectionHeader(pSectionHeader(DWORD(m_pExtraHeader) + sizeof(IMAGE_OPTIONAL_HEADER)))

//macro from bo2k [RVATOVA updated for our C++ class]
#define RVATOVA(type,offset) ((type)((DWORD)(PBYTE(*this))+(DWORD)(offset)))

class peControl {
public:
peControl(PBYTE pImageBase);
virtual ~peControl();

//returns original.
FARPROC InterceptImport(FARPROC pFuncOrigApi, FARPROC pFuncNewApi);
FARPROC InterceptImport(LPCSTR pDllName, LPCSTR pApiName, FARPROC pFuncNewApi);

operator PBYTE() const { return m_BaseData.pImageBase; }
operator PIMAGE_FILE_HEADER() const { return m_pFileHeader; }
operator PIMAGE_OPTIONAL_HEADER() const { return m_pExtraHeader; }
operator PIMAGE_SECTION_HEADER() const { return m_pSectionHeader; }

protected:

private:

const BaseData m_BaseData;
const pFileHeader m_pFileHeader;
const pExtraHeader m_pExtraHeader;
const pSectionHeader m_pSectionHeader;

};

peControl::peControl(PBYTE pImageBase) : InitConsts() {
return;
}

peControl::~peControl() {
return;
}

//InterceptImport concept by goldfinder
FARPROC peControl::InterceptImport(FARPROC pFuncOrigApi, FARPROC pFuncNewApi) {
PIMAGE_IMPORT_DESCRIPTOR pImportDesc = RVATOVA(PIMAGE_IMPORT_DESCRIPTOR, PIMAGE_OPTIONAL_HEADER(*this)->DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);
if(PBYTE(pImportDesc) == PBYTE(*this)) return NULL;

for(;pImportDesc->Name; pImportDesc++) {
   for(PIMAGE_THUNK_DATA pThunk = RVATOVA(PIMAGE_THUNK_DATA, pImportDesc->FirstThunk);
      pThunk->u1.Function; pThunk++) {

      if (FARPROC(pThunk->u1.Function) == pFuncOrigApi) {
            DWORD dwProtect;
            __try {
               pThunk->u1.Function = DWORD(pFuncNewApi);
            } __except(EXCEPTION_EXECUTE_HANDLER) {
               if(!VirtualProtect((LPVOID)(&pThunk->u1.Function), sizeof(DWORD), PAGE_EXECUTE_READWRITE, &dwProtect)) return NULL;
               pThunk->u1.Function = DWORD(pFuncNewApi);
            }
            VirtualProtect((LPVOID)(&pThunk->u1.Function), sizeof(DWORD), PAGE_EXECUTE, &dwProtect);
            return pFuncOrigApi;
      }
   }

}
return NULL;
}

FARPROC peControl::InterceptImport(LPCSTR pDllName, LPCSTR pApiName, FARPROC pFuncNewApi) {
FARPROC pCurrentApi = GetProcAddress(GetModuleHandle(pDllName), pApiName);
if(pCurrentApi) {
   return InterceptImport(pCurrentApi, pFuncNewApi);
}
return NULL;
}

DWORD WINAPI newGetTickCount(VOID) {
return 0x31337;
}

int main(void) {
class peControl *pe = new peControl(PBYTE(GetModuleHandle(NULL)));
FARPROC pOriginalGTC;
printf("hijacking GetTickCount.../n");
printf("original GetTickCount address = 0x%X/n", pOriginalGTC=pe->InterceptImport("kernel32","GetTickCount", FARPROC(newGetTickCount)));
printf("GetTickCount() returned 0x%X/n", GetTickCount());

printf("recalling old GetTickCount.../n");
pe->InterceptImport( FARPROC(newGetTickCount), pOriginalGTC);
printf("GetTickCount() returned 0x%X/n", GetTickCount());
delete pe;

return 0;
}

console output wrote:

hijacking GetTickCount...
original GetTickCount address = 0x77E7A29B
GetTickCount() returned 0x31337
recalling old GetTickCount...
GetTickCount() returned 0xEC9319