On Tue, 2 Oct 2001, Javier wrote:

I was wondering about the possiblity of moving the return addresses out of the stack completely (even hashed & check summed so that its not a simple matter of just writing a new return address over the existing one). Im not a complier or assembler writer, but it seems that this should be possible. Of course, as soon as it was made public exploits could be immediatly developed.

> For exploit buffer overflow you needn't know the distances you say, it helps
> but it's not essential. Once you know (or suspect) the program is weak you
> can try with differet sizes till you get the good one. If you want keep
> yourself safe from this kind of exploiting, make sure that you control
> buffer sizes. It is a simple and efficient method.
>
> PD: Excuse my english but it is not my parent tongue.
>
> ----- Original Message -----
> From: "Justin R. Smith" <jsmith@mcs.drexel.edu>
> To: <selinux@tycho.nsa.gov>
> Sent: Tuesday, October 02, 2001 10:42 AM
> Subject: A notion
>
>
> > It occurred to me that custom versions of software can be more secure
> > than standard versions because various exploits (like stack smashing,
> > etc.) require precise knowledge of certain sizes and distances in RAM
> > (for instance, the distance from the end of a buffer to the return
> > point...).
> >
> > Isn't it possible to develop a "randomizing C compiler" that randomly
> > varies these distances every time it compiles a program? No two compiles
> > of the same source code would be exactly the same (but they would
> > execute the same way).
> >
> > This might involve inserting small random-sized blocks of dead code, or
> > doing returns from subroutines through a level of indirection (i.e.,
> > putting the actual return at some random location in the object code
> > with a branch to it).
> >
> > Done right, this might not degrade performance significantly.
> >
> >
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