Self-deleting file

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Rookie

Joined: 21 Aug 2003
Posts: 44
Location: Planet Romania

Rookie 02 Aug 2004, 19:42

Can anyone give a piece of code of an exe that can do this?
Although I haven't tried it, common sense tells me that DeleteFile would cause a 'File In Use' error or something like that. I remember seeing somewhere something about it. The exe would copy itself somewhere in memory and run from there, thus being able to delete itself (they reffered to it as virus coding, I think). But I can't remember where. Nor how they did it (it was written in C, and I was just getting aquainted with it). Or maybe it's much simpler than that, but I haven't got a clue on how to do it. So, can anybody help me please?

PS: the 'virus coding' I mentioned earlier, I think it's a programming technique. I don't really know. I say this only to assure you that I'm not trying to write 'malicious code'. I'm working on a scriptable install system, and need the self-deleting capabilites for the uninstall.exe.

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02 Aug 2004, 19:42

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 02 Aug 2004, 20:25

There are a lot of solutions (including with .bat files), but the only two pure assembly solutions I saw was:
1. Using stack for creating code that to be executed from kernel (on some ret) after terminating process.
2. Code injection in another process, that works in memory (for example explorer.exe) that to wait for base process termination and to delete the file.
AFAIK, comrade was the author of one example about something similar: writing data in self executable: http://comrade64.cjb.net/src-asm.en.htm

Regards.

02 Aug 2004, 20:25

silkodyssey

Joined: 02 Oct 2003
Posts: 198
Location: St.Vincent & the Grenadines

silkodyssey 02 Aug 2004, 22:12

Some of the programs here may be helpful to you.
http://www.ols-lab.com/devcorner/tasm32/

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silkodyssey

02 Aug 2004, 22:12

comrade

Joined: 16 Jun 2003
Posts: 1150
Location: Russian Federation

comrade 03 Aug 2004, 00:07

It is possible in Windows 2000 (not sure about NT4), but not Windows XP. The trick is to destroy the kernel object (a section object) that locks the file, and then do a trick with a chained call that would delete the file and quit immediately. This does not work in XP because the handle for the section object is random and unknown, but is fixed and known in Windows 2000.

More info here:
http://www.catch22.org.uk/tuts/selfdel.asp

and here:
http://www.wasm.ru/forum/index.php?action=vthread&forum=4&topic=2569&page=1

You are interested in the .zip attachment in Four-F's post.

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comrade (comrade64@live.com; http://comrade.ownz.com/)

03 Aug 2004, 00:07

Rookie

Joined: 21 Aug 2003
Posts: 44
Location: Planet Romania

Rookie 03 Aug 2004, 22:53

Thanx! A lot! Now to get to work... (If anybody's interested in taking a look at the project, just say so)

03 Aug 2004, 22:53

Rookie

Joined: 21 Aug 2003
Posts: 44
Location: Planet Romania

Rookie 05 Aug 2004, 11:54

I used the 5th example from http://www.catch22.org.uk/tuts/selfdel.asp
I made an asm version of it (which I also attached). Unfortunately, it doesn't seem to work. I traced the problem to the VirtualProtectEx call, which fails. I think it's because entrypoint is not calculated corectly.
In the C source code it's something like this:

Code:

entrypoint = (context.Esp - sizeof(SELFDEL)) & ~0x1F

which I translated as

Code:

        mov     eax,1Fh
        not     eax
        mov     ebx,[context.Esp]
        sub     ebx,sizeof.SELFDEL
        and     eax,ebx
        mov     [entrypoint],eax

Did I do it right? And if so, can anybody tell me where's the bug?

Description:		Download
Filename:	selfdel.zip
Filesize:	6.41 KB
Downloaded:	403 Time(s)

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05 Aug 2004, 11:54

rwalt

Joined: 27 Apr 2004
Posts: 19
Location: Illinois, USA

rwalt 07 Sep 2004, 00:13

I translated a TASM example ( which I believe is the only example in assembler ) of an self-deleteing EXE. Using OllyDbg I finally got this to work...

Code:

include '%fasminc%/win32ax.inc'

MAX_PATH = 104h
STACK_CODE_SIZE = 9h

.code
stack_code:
        pop     eax
        call    eax ;call FreeLibrary
        pop     eax
        call    eax ;call DeleteFile
        ret     (MAX_PATH + STACK_CODE_SIZE - 4h)

start:
        sub     esp, (MAX_PATH + STACK_CODE_SIZE)
        mov     edi, esp

        mov     ebx, edi
        mov     ecx, STACK_CODE_SIZE
        mov     esi, stack_code
        rep     movsb

        push    MAX_PATH
        push    edi
        push    ecx
        call    L1

        mov     eax, L2
        mov     eax, [eax + 2h]
        push    dword [eax]

        push    edi

        mov     eax, L3
        mov     eax, [eax + 2h]
        push    dword [eax]

        push    0h
        call    L4

        push    eax

        mov     eax, L5
        mov     eax, [eax + 2h]
        push    dword [eax]

        jmp     ebx

    L1: jmp     [GetModuleFileName]
    L2: jmp     [ExitProcess]
    L3: jmp     [DeleteFile]
    L4: jmp     [GetModuleHandle]
    L5: jmp     [FreeLibrary]

.end start

This will work on both 9x and ME. To possibly get it to work on NT you will have to replace FreeLibrary with UnmapViewOfFile.

07 Sep 2004, 00:13

Madis731

Joined: 25 Sep 2003
Posts: 2139
Location: Estonia

Madis731 08 Sep 2004, 20:59

nope, it doesn't work that way:(

08 Sep 2004, 20:59

rwalt

Joined: 27 Apr 2004
Posts: 19
Location: Illinois, USA

rwalt 09 Sep 2004, 16:08

Madis731 wrote:

nope, it doesn't work that way:(

I think I have got it to work, try this code...

Code:

; SELF-DEL.ASM
; Self-deleting executable file code
; For Windows 9x/ME/NT

include '%fasminc%/win32ax.inc'

.code
main:
    push    ebp
 mov     ebp, esp

        sub     esp, 10Ch

       push    0
   call    @1
  mov     [ebp-4], eax

    push    104h
        lea     eax, [ebp-108h]
     push    eax
 mov     eax, [ebp-4]
        push    eax
 call    @2

      call    @3
  and     eax, 80000000h
      cmp     eax, 0
      jz      winnt

   mov     eax, [FreeLibrary]
  mov     [ebp-10Ch], eax
     jmp     delete

    winnt:
        mov     eax, [UnmapViewOfFile]
      mov     [ebp-10Ch], eax
     push    4
   call    @4

    delete:
   lea     eax, [ebp-108h]
     push    0
   push    0
   push    eax
 push    dword [ExitProcess]
 push    dword [ebp-4]
       push    dword [DeleteFile]
  push    dword [ebp-10Ch]
    ret

    @1: jmp      dword [GetModuleHandle]
    @2: jmp      dword [GetModuleFileName]
    @3: jmp    dword [GetVersion]
    @4: jmp   dword [CloseHandle]

.end main

This might possibly work for Win2K, but will never work at all for XP/2K3.

09 Sep 2004, 16:08

Matrix

Joined: 04 Sep 2004
Posts: 1166
Location: Overflow

Matrix 09 Sep 2004, 16:16

Its all right on win 98 se

MATRIX

09 Sep 2004, 16:16

Madis731

Joined: 25 Sep 2003
Posts: 2139
Location: Estonia

Madis731 11 Sep 2004, 08:39

Works on 2K SP4

11 Sep 2004, 08:39

Nikolay Petrov

Joined: 22 Apr 2004
Posts: 101
Location: Bulgaria

Nikolay Petrov 11 Sep 2004, 18:53

Code:

;selfdel.asm
;The COMSPEC method - use cmd.exe command line
format PE GUI 4.0

include '%fasminc%\win32a.inc'

section '.code' code readable executable
entry start
start:
;--------------- Follow Code -----------------
    invoke GetModuleFileName,0,szCmd,255
    invoke GetShortPathName,szCmd,szFile,255
    invoke wsprintf,szCmd,szFormat,szFile
    invoke GetEnvironmentVariable,Cmd,szFile,255
    invoke MessageBox,0,message,title,MB_ICONINFORMATION
    invoke ShellExecute,0,0,szFile,szCmd,0,SW_HIDE
    invoke ExitProcess,0

;--------------- Follow Data -----------------
section '.data' data readable writeable

Cmd db "ComSpec",0
szFormat db "/c del %s >> NUL",0
title db "SelfDelete Demo",0
message db "When you press OK - file selfdel.exe will be delete.",0
szFile rb 255
szCmd  rb 255


;------------- Follow Import section --------------
section '.idata' import data readable writeable

 library kernel32,'kernel32.dll',\
         user32,  'user32.dll',\
         shell32, 'shell32.dll'

        include '%fasminc%\apia\kernel32.inc'
        include '%fasminc%\apia\user32.inc'
        include '%fasminc%\apia\shell32.inc'

11 Sep 2004, 18:53

asmdemon

Joined: 18 Jan 2004
Posts: 97
Location: Virginia Beach, VA

asmdemon 12 Sep 2004, 02:28

works on xp sp2

12 Sep 2004, 02:28

Rookie

Joined: 21 Aug 2003
Posts: 44
Location: Planet Romania

Rookie 01 Oct 2004, 21:19

Hey, guys, sooory it took me so long to get back to you. Thank you for your solutions. I haven't tested them yet to see if they'll do the trick for me, but I'd still like to thank you.

01 Oct 2004, 21:19

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