Thread: Problem with keyboard hook

Ok I thought the following would hook the keyboard input for only the one process but its getting it for all. Is there a way I can limit it to just one process?

File: dll.h

Code:

#ifndef _DLL_H_
#define _DLL_H_
#include <windows.h>

#define EXPORT __declspec (dllexport)

#if BUILDING_DLL
# define DLLIMPORT __declspec (dllexport)
#else /* Not BUILDING_DLL */
# define DLLIMPORT __declspec (dllimport)
#endif /* Not BUILDING_DLL */


EXPORT LRESULT CALLBACK KbProc(int, WPARAM, LPARAM);
EXPORT BOOL WINAPI InstallHook(HWND);
EXPORT void WINAPI RemoveHook(void);
#endif /* _DLL_H_ */

File: dllmain.c

Code:

#include "dll.h"
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>


#pragma data_seg("shared_data")
// Superglobals
HHOOK hookdata = 0;
#pragma data_seg()
#pragma comment(linker, "/SECTION:shared_data,S")

HMODULE hmodule = 0;
HWND hwindow = 0;
BOOL recycle = FALSE;
BOOL running = FALSE;
UINT timerid = 0;
void CALLBACK TimerProc(HWND hwnd, UINT uMsg, UINT idEvent, DWORD dwTime);

EXPORT LRESULT CALLBACK KbProc(int code, WPARAM w, LPARAM l)
{
  if ( code < 0 || code != HC_ACTION )
    return CallNextHookEx(hookdata,code,w,l);

  char buff[100];

  sprintf(buff,"Values are: %d %u %u\n", code, w, l);

  MessageBox(0, buff, "ok", 0);

  switch(w)
  {
    default: return CallNextHookEx(hookdata,code,w,l);
  }
  return TRUE;
}

BOOL APIENTRY DllMain (HMODULE hmod,
                       DWORD reason,
                       LPVOID na)
{
    switch (reason)
    {
      case DLL_PROCESS_ATTACH:
           hmodule = hmod;
        break;

      case DLL_PROCESS_DETACH:
        break;

      case DLL_THREAD_ATTACH:
        break;

      case DLL_THREAD_DETACH:
        break;
    }

    /* Returns TRUE on success, FALSE on failure */
    return TRUE;
}

EXPORT BOOL WINAPI InstallHook(HWND hwnd)
{
  if ( hookdata != 0 )
     return FALSE;
  hwindow = hwnd;
  hookdata = SetWindowsHookEx(WH_KEYBOARD, KbProc, hmodule, 0);
  if ( !hookdata )
     MessageBox(0, TEXT("Hook failed."), TEXT("Error"), MB_ICONEXCLAMATION); 
  return hookdata != 0;
}

EXPORT void WINAPI RemoveHook(void)
{
  if ( hookdata != 0 )
  {
    UnhookWindowsHookEx(hookdata);
  }
}

void CALLBACK TimerProc(HWND hwnd, UINT uMsg, UINT idEvent, DWORD dwTime)
{
}

File: main.c (its in one directory deeper then the other two)

Code:

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include "..\dll.h"

typedef BOOL (WINAPI *INST)(HWND);
typedef void (WINAPI *UNINST)(void);

int main(int argc, char *argv[])
{
  HWND hwindow = FindWindow(NULL,"Untitled - Notepad");
  if ( !hwindow )
  {
     MessageBox(0, TEXT("Could not locate notepad"), TEXT("Error"), MB_ICONEXCLAMATION);
     system("pause");
     return EXIT_FAILURE;
  }

  HMODULE hmod = LoadLibrary(TEXT("..\\Hooks.dll")); 
  if ( hmod == 0 )
  {
     MessageBox(0, TEXT("Could not load library"), TEXT("Error"), MB_ICONEXCLAMATION);
     system("pause");
     return EXIT_FAILURE;
  }

  INST InHook = (void*)GetProcAddress(hmod, TEXT("InstallHook"));
  UNINST UnHook = (void*)GetProcAddress(hmod, TEXT("RemoveHook"));
  
  if ( InHook && UnHook )
  {
     InHook(hwindow);
     printf("Please press enter to terminate: ");
     fflush(stdout);
     getchar();
     UnHook();
  }

  FreeLibrary(hmod);
  
  system("pause");
  return 0;
};

References: http://cboard.cprogramming.com/showthread.php?t=60642
http://cboard.cprogramming.com/showt...t=windows+hook

As I said it is getting info from all processes which is ok if I can filter them out and send them on their way.

Also is there a way to get the HWND using the process name and not the the window name?

To retrieve a list of processes you can use CreateToolhelp32Snapshot with TH32CS_SNAPPROCESS. One of the entries in the PROCESSENTRY32 structure that is returned for every process is szExeFile. Once you have found a target process, you can either match up its process id with the one returned from GetWindowThreadProcessId, as suggested by bithub, or enumerate its threads with TH32CS_SNAPTHREAD.

Shared segments are bad.