Hi,
I wrote a piece of code for API hooking.. but I am getting access violation
error.. Please correct me where I went wrong.
#include<stdio.h>
#include<tchar.h>
#include<windows.h>
typedef void (*name)(DWORD );
void printname(DWORD i)
{
printf("\n i is %d",i);
printf("\n Gopi");
}
int main()
{
HMODULE hmod;
IMAGE_DOS_HEADER *DosHeader;
IMAGE_NT_HEADERS32 *NTHeaders;
IMAGE_OPTIONAL_HEADER32 OH;
IMAGE_IMPORT_DESCRIPTOR *ImportDesc,*ImportDesc_Temp;
char *tmp;
char *FuncName;
DWORD *FuncAddr;
int ret=-10;
hmod=LoadLibrary(_T("C:\\Documents and Settings\\PERSONAL\\My Documents\\Visual
Studio 2005\\Projects\\SumDll\\SumDll\\debug\\SumDll.dll"));
DosHeader=(IMAGE_DOS_HEADER *)hmod;
NTHeaders=(IMAGE_NT_HEADERS32 *)(DosHeader->e_lfanew+(BYTE *)DosHeader);
OH=NTHeaders->OptionalHeader;
DWORD IMageBase=OH.ImageBase;
ImportDesc=(IMAGE_IMPORT_DESCRIPTOR *)(OH.DataDirectory[1].VirtualAddress+(BYTE
*)DosHeader);
ImportDesc_Temp=ImportDesc;
DWORD oldprotect,oldprotect_1;
while(ImportDesc_Temp->Name)
{
tmp=(char *)(ImportDesc_Temp->Name+(BYTE *)DosHeader);
printf("\n The name of the Dll is %s",tmp);
IMAGE_THUNK_DATA32 *ThunkData=(IMAGE_THUNK_DATA32
*)(ImportDesc_Temp->OriginalFirstThunk+(BYTE *)DosHeader);
IMAGE_THUNK_DATA32 *FirstThunkData=(IMAGE_THUNK_DATA32
*)(ImportDesc_Temp->FirstThunk+(BYTE *)DosHeader);
int x=0;
while(ThunkData->u1.Function)
{
FuncName=(char *)((BYTE *)DosHeader+ThunkData->u1.AddressOfData+2);
if(!stricmp(FuncName,"Sleep"))
{
FuncAddr = (DWORD *)(FirstThunkData->u1.Function);
ret = VirtualProtect(FuncAddr,4,PAGE_READWRITE,&oldprotect);
*FuncAddr=(DWORD )printname;
ret = VirtualProtect(FuncAddr,4,PAGE_EXECUTE,&oldprotect_1);
}
printf("\n The function name is %s",FuncName);
ThunkData++;
FirstThunkData++;
}
ImportDesc_Temp++;
x++;
}
Sleep(1000); /// getting access violation error here
return 1;
}
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