Re: Is DEP easily evadable?

[John Richard Moser <nigelenki () comcast net>]

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Ben Pfaff wrote:
> John Richard Moser <nigelenki () comcast net> writes:
>
>
> > PaX does pretty nice randomization.  I think 15/16 for heap and stack
> > and 24 for mmap(), though I could be overshooting the 24.  I'm on amd64
> > so I can't just run paxtest and see; though I could read the source code.
>
>
> In some fairly reasonable circumstances, this may not be enough.
> I wonder whether the security community is generally aware of a
> paper I co-authored on defeating PaX and address space
> randomization in general on 32-bit systems, titled "On the
> Effectiveness of Address Space Randomization".  It was presented
> at CCS 2004 and available on my webpage, among other places:
>         http://www.stanford.edu/~blp/papers/asrandom.pdf

Brad says he's seen it, and that at the time of that writing he'd
already solved that problem.

Apparently in grsecurity, once you've caused a program to segfault or
get a PaX kill, it's flagged to delay all future forks by 30 seconds, or
something like that.  I don't know the exact details.

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