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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>
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