x64 code in x86 file

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roxaz

Joined: 27 Jul 2008
Posts: 25

roxaz

http://vx.netlux.org/lib/vrg02.html

maybe we can hope fasm to support this too? ^_^

12 Jul 2009, 15:41

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17628
Location: In your JS exploiting you and your system

revolution

fasm already supports mixed 32/64 code. Has done for a long time.

12 Jul 2009, 15:55

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7782
Location: Kraków, Poland

Tomasz Grysztar

And with fasm you really don't have to use "db" directives to build jumps. Wink

12 Jul 2009, 15:56

bitRAKE

Joined: 21 Jul 2003
Posts: 3018
Location: vpcmipstrm

bitRAKE

Syntax is a little different:

Code:

     format PE GUI 4.0
   include 'win32wxp.inc'
    .end start

      use64
in64:
  mov rax, qword [gs:30h] ;gs not fs
      mov rax, qword [rax+60h]
    mov rax, qword [rax+18h]
    mov rax, qword [rax+30h]
    mov rax, qword [rax+10h]

; use native 64-bit interface

   retfd
       use32


start:
 call 33h:in64
   ;32-bit code continues here
 
        invoke ExitProcess, 0

Edit: Thanks, Tomasz

Last edited by bitRAKE on 12 Jul 2009, 19:07; edited 1 time in total

12 Jul 2009, 16:02

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 7782
Location: Kraków, Poland

Tomasz Grysztar

bitRAKE: still one thing could use small correction - put USE32 after RETF instead of before (because return instruction still belongs to a 64-bit world) and change RETF to RETFD to get same result in a more "proper" way.

12 Jul 2009, 16:07

roxaz

Joined: 27 Jul 2008
Posts: 25

roxaz

heh noob me... should have checked before posting ^_^

12 Jul 2009, 17:43

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4633
Location: Argentina

LocoDelAssembly

I hope the people who asked about mixing 32- and 64-bit code is looking at this right now. Any comments about the reliability of this method?

12 Jul 2009, 17:43

Borsuc

Joined: 29 Dec 2005
Posts: 2466
Location: Bucharest, Romania

Borsuc

What's with the 33h after the call? Is that a segment? How does it work anyway? Confused

(btw is hard-coding segment values reliable?)

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Previously known as The_Grey_Beast

12 Jul 2009, 22:07

windwakr

Joined: 30 Jun 2004
Posts: 827
Location: Michigan, USA

windwakr

website at top of thread wrote:

Heaven's Gate

The jump in wow64cpu.dll is a 64-bit gate. We can jump through it into the world of 64-bit code: 64-bit address space, 64-bit registers, 64-bit calls. We might think that jumping into wow64cpu.dll is useless because we cannot control where it goes after that, but of course we can change the address ourself to anywhere we like. We can alter the address inside wow64cpu.dll, we can alter the address at fs:[0c0h], or we can just call through the gate on our own. The gate maps the entire 4Gb of memory, and the selector value is always 33h.

12 Jul 2009, 22:33

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 17628
Location: In your JS exploiting you and your system

revolution

LocoDelAssembly wrote:

Any comments about the reliability of this method?

Since MS have in no way said that all the various offset and/or segment values will remain static then this method could well fail on some future Windows version. Plus the fact that the native interface is also not-documented (a deliberate decision by MS so that they can change if they need to) so basically, use with caution and if it bombs then tough, you won't get help from any official documents.

12 Jul 2009, 23:44

Borsuc

Joined: 29 Dec 2005
Posts: 2466
Location: Bucharest, Romania

Borsuc

Exactly that was the point of my question.

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Previously known as The_Grey_Beast

12 Jul 2009, 23:48

Madis731

Joined: 25 Sep 2003
Posts: 2140
Location: Estonia

Madis731

shouldn't it be 4 giga BYTES? http://xkcd.com/394/
I hate when they get it wrong Sad

13 Jul 2009, 09:25

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