Re: Clever ways to hide a compare


David J. Craig yazdi:
> I did say if you are using DOS. This won't work for Windows NT unless you
> know a lot about the internals of the kernel and then even self modifying
> code is possible with device driver support. How can you have a buffer
> overflow if you write the code correctly. You are setting things based upon

I was talking about writing some code in a way to make it possible a
buffer overflow attack. And then you yourself do the attack against
your own code.

> decisions you have made and not on user input. It might be a side effect of
> user input in that you might change the code flow based upon that input, but
> you will have checked and validated the input before you start making these
> type of modifications.
>
> "Aslan" <spamtrap@xxxxxxxxxx> wrote in message
> news:1127634980.916261.122630@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > David J. Craig yazdi:
> >> Depending upon the register/data size, you can use a subtract, add,
> >> multiply, or divide. You can do a translate and come up with some
> >> interesting possibilities. If this is DOS and not Windows NT, you can
> >> have
> >> self modifying code that can do wonderful things. Translate an
> >> instruction
> >
> > Isn't is possible under Windows NT? How 'bout a buffer overflow attack
> > against your code on purpose? Is it a good idea or bad idea?
> >
> >> to something good if the value is good. Otherwise change it to something
> >> that will lead to headaches.
> >>
> >> "jonathon" <spamtrap@xxxxxxxxxx> wrote in message
> >> news:1127603005.082317.85010@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> >
> >> > Suppose you are writing a protection scheme, and need to compare 2
> >> > values. Is there a clever way to do this without an outright 'cmp'
> >> > instruction? Of course it's always possible to use the value in a
> >> > calculation that is needed for correct functionality of the program,
> >> > but I was wondering if there is a way to have 2 values compared in a
> >> > sneaky way where it is not immediately evident what is happening.
> >> >
> >

.

Relevant Pages

  • Re: Clever ways to hide a compare
    ... I did say if you are using DOS. ... decisions you have made and not on user input. ... If this is DOS and not Windows NT, ... >>> Suppose you are writing a protection scheme, and need to compare 2 ...
    (comp.lang.asm.x86)
  • JOptionPane
    ... i do a simple program which runs in Dos. ... When user input a keyword, ... dialog box will pop up but it hides behind all the windows forms i have ...
    (comp.lang.java.programmer)
  • Re: Clever ways to hide a compare
    ... > I did say if you are using DOS. ... This won't work for Windows NT ... It might be a side effect of user input in that you might ... You can do self modifying code on NT without any problems, ...
    (comp.lang.asm.x86)
  • ~~~~~~~~~~~~~~ FILE NAME ~~~~~~~~~~~~~~
    ... adapter description file file name extension ... apple script to change file names ... batching file name changes in windows ... change short file names in dos ...
    (sci.misc)
  • Re: Linux syscalls
    ... > A device driver or a rewrite of DOS could permit this, ... really "DOS inside Windows" or "Windows inside DOS"? ... > DOS interrupts are revectored... ... if you re-write DOS to use the _Windows device drivers_ ...
    (alt.lang.asm)