I am trying create a tool for performing DLL-Injection by writing the the DLL in the Memory of a running process using VirtualAclloc() API and then finding the offset of the entrypoint and passing it to the CreateRemoteThread() API by adding the entry point offset to the base address of the VirtualAlloc function.
As I don't have any arguments that needs to be passed to lpStartAddress while calling CreateRemoteThread(), I initialized lpParameter as NULL.
LPVOID lpParameter = NULL;
...
...
thread_handle = CreateRemoteThread(process_handle, NULL, 0, (LPTHREAD_START_ROUTINE)(base_address + offset), lpParameter, 0, NULL);
While compiling the code I am getting the error :
LPVOID: Unknown Size" and the message "Expression must be a pointer to a complete object type.
Is there a way I can pass the value of lpParameter as NULL?
base_address + offset adds offset*sizeof *base_address bytes to the pointer base_address. But if the type of base_address is LPVOID then *base_address has no size, so this is an error. Have a look at the section on pointer arithmetic in your C++ book.
From the context I guess you should change base_address to be char* instead of LPVOID. Or you could add a cast like this (LPTHREAD_START_ROUTINE)((char*)base_address + offset).