Messages in this thread | | | Date | Mon, 27 Dec 1999 18:58:32 -0500 (EST) | From | "Richard B. Johnson" <> | Subject | Re: Unexecutable stack |
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On Mon, 27 Dec 1999, Steve VanDevender wrote:
> Richard B. Johnson writes: > > The notion of a secure stack implies that you get some kind of security > > by making the stack non-executable. This theory has, to the best on > > my knowledge, never been shown to have merit, much less proof. The > > old games of loading executable opcodes into local data on the stack, > > overwriting the return address with that data (to point to the code > > you want to execute), then causing an exception (stack overrun) to > > make it happen, are not something you could encounter with the current > > network daemons. > > > > You would need a local account, with root access, to even experiment. > > I run a couple of large Solaris 7 systems with the > "noexec_user_stack" option enabled. This defeats nearly all root > exploits based on stack overflows; I've tried them and intruders > have tried them without success. Making the stack non-executable > really does help.
So how many root exploits have you actually had? And, how many attempts? I have, at last count, 54 Suns, 126 Alphas, a few hundred ix86/Linux, plus slightly less than 1,000 Win/Win-NT machines on this very site where we have 1,200 engineering employees. Most all the Suns, Alphas, and Linux machines are not filtered by a firewall.
We have never had a known, provable break-in of any kind, not counting the engineers blue-screening the Windows machines by throwing funny packets at them.
> > You don't quite seem to understand the mechanism of stack buffer > overflow exploits. The buffer overflow does not cause an
I understand it exactly and precisely. It is likely that I was the first to demonstrate this in the late '70s.
Cheers, Dick Johnson
Penguin : Linux version 2.3.13 on an i686 machine (400.59 BogoMips). Warning : The end of the world as we know it requires a new calendar. Seconds : 363688 (until Y2K)
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