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SubjectRe: Unexecutable Stack / Buffer Overflow Exploits...
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Robert Dinse <nanook@eskimo.com> said:

> Boy, I'd kill for some generic buffer overflow exploit prevention
> that was 100% foolproof and didn't depend on applications being written
> properly, while still maintaining reasonable functionality of the
> computing environment. I.E. turning the power off and locking the
> machine in a physically secured environment would be secure but not very
> functional.

That is sysadmins "better mousetrap" ;-)

> To the person that said most modern clients are smart enough to
> change UID before accepting user input, I have to ask, how many times
> have you had to upgrade sendmail, bind, ftpd, popd, imapd, rstatd,
> rlockd, portmap, .... because of buffer overflow exploits that keep
> popping up?

Far too many times, but the rate _has_ slowed down significantly in the
last few years. Might be my imagination, though.

> And even for example, if you run bind non-root, if they can
> clobber your name server files and screw up name service, even that will
> suffice to raise major havoc. Besides if they can get a shell as ANY UID
> that gives them an inside base from which to advance their attack.

No such attack has been posted recently...

> It's pretty clear to me that applications programmers will never
> adequately secure their code; and it's beyond the scope of what I can do
> to re-write every application I use or to be absolutely sure there are no
> buffer overflow or other exploits.

There are audit projects around, the software _is_ getting fixed, server
stuff is being designed/programmed more carefully these days. Sure, you
could decree that all servers must be written in Java or some other "safe"
language, but that will just shift the problems to the implementation of
the language, and have a huge cost in rewriting and retesting. Plus cost a
bundle in performance...

> If you can stop the script kiddies; that's about 99.99% of the problem
> solved.

Where do you think script kiddies get their exploit scripts from? They
don't write them themselves: The real crackers share them with the
community. Just like the hacker community shares patches and cool
programs. So you can keep out 99.99% only until one of the 0.01% finds out
a way around it. The danger of "nonexecutable stack" is that it creates a
sense of security, which might be justified as long as it is rare. Once it
becomes widespread, it will be useless in short time, and _everybody_ will
have to pay the cost for nothing at all, while feeling smugly secure.
--
Dr. Horst H. von Brand mailto:vonbrand@inf.utfsm.cl
Departamento de Informatica Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria +56 32 654239
Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513

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