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Re: Buffer overflow prevention
From: Shaun Clowes <shaun () securereality com au>
Date: Fri, 15 Aug 2003 09:27:24 +1000

On Thu, Aug 14, 2003 at 07:26:47PM +0200, Mariusz Woloszyn wrote:
On Thu, 14 Aug 2003, Stephen Clowater wrote:

Also, you can use chpax, and turn on a non-executable stack, and with a small
amount of voodoo (in tracking down the binarys and .so's that need the stack,
wich typically is only a single binary or .so file, wich you can find with
ptrace, strace, or ltrace) you can have all of your stuff run with a
non-executeable stack, thus making stack smashing impossible. Nothing can
execute off your stack so a malicous person can override all the addresses he
wants, his code cant run off your stack.

Perhaps I'm the only one who feels this way, but I believe that the vast
majority of the exploitation of systems is being performed by people
with no knowledge of how to write an exploit and that the vast majority
of exploits are fragile. Doing anything that makes you different from
every other installation of Linux/HPUX/Solaris/InsertOSHere will
drastically decrease the changes of any point and click exploit working
against you.

Could a determined (and knowledgable) attacker still get through? Sure.
But if we're talking protections that take very little effort to
implement, have a minor performance impact and will save your
skin some of the time, it's obvious that it's worth deploying them. As
long as you're not kidding yourself that you're then totally secure.

Its kind of reminiscent of that old joke about the two guys running away
from the lion. You don't have to beat the lion, just the other person. 

Cheers,
Shaun


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