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AA with SEH Structured Exception Handling (for advanced)

 
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GH*master
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Posts: 149
Location: Russia

PostPosted: Tue Feb 02, 2016 8:04 am    Post subject: AA with SEH Structured Exception Handling (for advanced) Reply with quote

This Auto Assembler tutorials about

Structured Exception Handling (for advanced)

Ooh yeah...

If you wish, you can will bypass the application crashes when doing something wrong


Code:

label(Handler)
label(NoException)
label(ExceptionHandled)
label(lpCaption)
label(lpText)

00270000:  // you need create thread on 00270000
   pushad
   mov esi, Handler
   push esi
   push fs:[0]
   mov fs:[0], esp

   mov ecx, [0]   // Oh my God, what is it? EXEPTION! Do not worry about it! We have SEH

   Jmp NoException
Handler:
   mov esp,[esp+0x08]
   pop fs:[0]
   add esp, 4
   popad

   // This point if we have exception runnig
   Jmp ExceptionHandled
   Jmp NoException

NoException:
   pop fs:[0]         // restore the old EXEPTION
   add esp, 0x24 //32+4
   ret

ExceptionHandled:
   // the exception was eaten
   push 0             //uType  (0=mb_ok)
   push lpCaption
   push lpText
   push 0           //hWnd
   call MessageBoxA
   ret

lpCaption:
   db 'Exception!' 0

lpText:
   db 'You have exception' 0
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Redouane
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Joined: 05 Sep 2013
Posts: 355
Location: Algeria

PostPosted: Tue Feb 02, 2016 8:56 am    Post subject: Re: AA with SEH Structured Exception Handling (for advanc Reply with quote

Can you please explain the following lines?
GH*master wrote:

Code:

Handler:
   mov esp,[esp+0x08]
   pop fs:[0]
   add esp, 4
   popad

before executing the first Handler Instruction,the stack should look like this :
Code:

----------------------------------------------------------<ESP
|address of the instruction that comes after mov ecx, [0]|
----------------------------------------------------------<ESP+4
|Address to previous handler (previous FS:[0])           |
----------------------------------------------------------<ESP+8
|address of Handler (new handler)                        |
----------------------------------------------------------<ESP+0xC
|All the saved registers                                 |

So [esp+8] should be the address of the new handler,why are you moving it to esp?
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