[solved] having trouble with locals

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DergMoney

Joined: 29 Apr 2015
Posts: 34

DergMoney 07 Jun 2015, 08:21

Hi,

Can anyone explain why this fails to assemble? I get an 'invalid value' error from fasm for

invoke FindFirstFile, fffStr, wfd

??

Code:

proc threadCheckForFiles

    locals
        wfd                    WIN32_FIND_DATA
        fffStr                 db "*.txt", 00
        searchingForFilesStr   db "Searching for files...", 00
        fnfHnd                 dd ?
    endl

        invoke  SetWindowText, [hWndMain], searchingForFileStr
        cmp     eax, TRUE
        je      .start
        call    showError
    .start:
        invoke  FindFirstFile, fffStr, wfd
        cmp     eax, INVALID_HANDLE_VALUE
        jne     @f
        jne     .start
        jmp     .finish
      @@:
        ; save FindNext handle
        mov     [fnfHnd], eax
    .finish:
        ret
endp

07 Jun 2015, 08:21

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20628
Location: In your JS exploiting you and your system

revolution 07 Jun 2015, 08:34

You need to make it an address because of the implicit EBP offset:

Code:

invoke  SetWindowText, [hWndMain], addr searchingForFileStr
;...
invoke  FindFirstFile, addr fffStr, addr wfd

07 Jun 2015, 08:34

DergMoney

Joined: 29 Apr 2015
Posts: 34

DergMoney 07 Jun 2015, 09:14

Thanks for the quick reply revolution. Unfortunately it didn't work Sad

flat assembler version 1.71.39 (1048576 kilobytes memory)
test.asm [72]:
invoke FindFirstFile, addr fffStr, addr wfd
D:\Program Files (x86)\Fasm\INCLUDE\macro/proc32.inc [17] invoke [3]:
pushd arg
error: invalid value.

Code:

proc threadCheckForFiles

    locals
        wfd                    WIN32_FIND_DATA
        fffStr                 db "*.txt", 00
        searchingForFilesStr   db "Searching for files...", 00
        fnfHnd                 dd ?
    endl

        invoke  SetWindowText, [hWndMain], addr searchingForFileStr
        cmp     eax, TRUE
        je      .start
        call    showError
    .start:
        invoke  FindFirstFile, addr fffStr, addr wfd
        cmp     eax, INVALID_HANDLE_VALUE
        jne     @f
        jne     .start
        jmp     .finish
      @@:
        ; save FindNext handle
        mov     [fnfHnd], eax
    .finish:
        ret
endp

07 Jun 2015, 09:14

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20628
Location: In your JS exploiting you and your system

revolution 07 Jun 2015, 09:19

Are you including the win32ax.inc file?

07 Jun 2015, 09:19

DergMoney

Joined: 29 Apr 2015
Posts: 34

DergMoney 07 Jun 2015, 09:27

All the code is is a simple window that sets up a thread 'threadCheckForFiles'

If I comment out the two 'offensive' lines Rolling Eyes

Code:

invoke  SetWindowText, [hWndMain], addr searchingForFileStr
.
.
invoke  FindFirstFile, addr fffStr, addr wfd

it assembles without issue Question

Full code...

Code:

format PE GUI 4.0
entry start

include "%fasminc%\win32a.inc"

section '.code' code readable executable

    start:
        invoke  GetModuleHandle, 0
        mov         [wc.hInstance], eax
        invoke  LoadIcon, 0, IDI_APPLICATION
        mov         [wc.hIcon], eax
        invoke  LoadCursor, 0, IDC_ARROW
        mov         [wc.hCursor], eax
        invoke  RegisterClass, wc
        or          eax,eax
        jz          showError
        invoke  CreateWindowEx, NULL, ClassMain, AppName, WS_OVERLAPPEDWINDOW or WS_VISIBLE, 100, 100, 600, 200, NULL, NULL, [wc.hInstance], NULL
        test    eax,eax
        jz          showError
        mov     [hWndMain], eax
        invoke  CreateThread, NULL, 0, threadCheckForFiles, NULL,NORMAL_PRIORITY_CLASS, tcffId
        invoke  CloseHandle, eax

    msgLoop:
        invoke  GetMessage, msg, NULL, 0, 0
        or          eax, eax
        jz          endLoop
        invoke  TranslateMessage, msg
        invoke  DispatchMessage, msg
        jmp         msgLoop
    showError: 
        invoke  GetLastError 
        invoke  FormatMessage, FORMAT_MESSAGE_FROM_SYSTEM or FORMAT_MESSAGE_ALLOCATE_BUFFER, NULL, eax, LANG_NEUTRAL, errStrBuff, 0, NULL
        invoke  MessageBox, HWND_DESKTOP, [errStrBuff], NULL, MB_ICONERROR or MB_OK 
    endLoop:
        invoke  ExitProcess, [msg.wParam]

proc WndProc hwnd, wmsg, wparam, lparam
        push    ebx esi edi
        cmp     [wmsg], WM_DESTROY
        je      .wmDestroy
    .defWndProc:
        invoke  DefWindowProc, [hwnd], [wmsg], [wparam], [lparam]
        jmp     .finish
    .showError:
        invoke  GetLastError 
        invoke  FormatMessage, FORMAT_MESSAGE_FROM_SYSTEM or FORMAT_MESSAGE_ALLOCATE_BUFFER, NULL, eax, LANG_NEUTRAL, errStrBuff, 0, NULL
        invoke  MessageBox, HWND_DESKTOP, [errStrBuff], NULL, MB_ICONERROR or MB_OK 
    .wmDestroy:
        invoke  PostQuitMessage, 0
        xor         eax, eax
    .finish:
        pop     edi esi ebx
        ret
endp

proc threadCheckForFiles

    locals
        wfd                    WIN32_FIND_DATA
        fffStr                 db "*.txt", 00
        searchingForFilesStr   db "Searching for files...", 00
        fnfHnd                 dd ?
    endl

        invoke  SetWindowText, [hWndMain], addr searchingForFileStr
        cmp     eax, TRUE
        je      .start
        call    showError
    .start:
        invoke  FindFirstFile, addr fffStr, addr wfd
        cmp     eax, INVALID_HANDLE_VALUE
        jne     @f
        jne     .start
        jmp     .finish
      @@:
        ; save FindNext handle
        mov     [fnfHnd], eax
    .finish:
        ret
endp




section '.data' data readable writeable
    ClassMain   db "WinClass", 00
    AppName     db "Test App", 00
    hWndMain    dd ?
    wc          WNDCLASS CS_HREDRAW or CS_VREDRAW, WndProc, 0, 0, NULL, NULL, NULL, COLOR_BTNFACE + 1, NULL, ClassMain
    msg         MSG
    errStrBuff  dd ?
    tcffId      dd ?

section '.idata' import data readable writeable 
library kernel32,'KERNEL32.DLL',\ 
        user32,  'USER32.DLL'

include '%fasminc%\api\Kernel32.inc' 
include '%fasminc%\api\User32.inc'

07 Jun 2015, 09:27

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20628
Location: In your JS exploiting you and your system

revolution 07 Jun 2015, 09:29

I see your problem: include "%fasminc%\win32a.inc".

You'll need the "x" version.
include "%fasminc%\win32ax.inc"

07 Jun 2015, 09:29

DergMoney

Joined: 29 Apr 2015
Posts: 34

DergMoney 07 Jun 2015, 09:31

Hadn't noticed you changed your last post.Here's fasm's output using win32ax

flat assembler version 1.71.39 (1048576 kilobytes memory)
test.asm [67]:
invoke SetWindowText, [hWndMain], addr searchingForFileStr
D:\Program Files (x86)\Fasm\INCLUDE\win32ax.inc [41] invoke [0]:
\{ \reverse pushd <arg>
D:\Program Files (x86)\Fasm\INCLUDE\win32ax.inc [37] pushd [27]:
pushd <value>
D:\Program Files (x86)\Fasm\INCLUDE\win32ax.inc [37] match [1]:
pushd <value>
D:\Program Files (x86)\Fasm\INCLUDE\win32ax.inc [78] pushd [6]:
if +var relativeto 0 | +var relativeto $
D:\Program Files (x86)\Fasm\INCLUDE\win32ax.inc [78] match [1]:
if +var relativeto 0 | +var relativeto $
error: undefined symbol 'searchingForFileStr'.

07 Jun 2015, 09:31

DergMoney

Joined: 29 Apr 2015
Posts: 34

DergMoney 07 Jun 2015, 09:34

Duh!

searchingForFileStr vs searchingForFilesStr

sorry to waste your time Embarassed

07 Jun 2015, 09:34

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