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Re: PointGuard: It's not the Size of the Buffer, it's the Address of the Pointer
From: Crispin Cowan <crispin () immunix com>
Date: Fri, 15 Aug 2003 11:00:04 -0700
Florian Weimer wrote:
Please address technical commentary to the paper (which addresses this
point) and not to the cute tag line.
Crispin Cowan <crispin () immunix com> writes:
Thanks to Snax and the Shmoo for a better tag line: It's not the Size
of the Buffer, it's the Address of the Pointer
This is not true. There are buffer overflow exploits which do not
modify pointers, but other objects. The most prominent example is
probably the "c c c c c..." exploit for the Solaris /bin/login
WRT this point: correct, PointGuard does not stop all buffer overflows.
IMHO it *nearly* stops all shell code. To bypass PointGuard, you have to
corrupt the logic of the program itself to get its own code to do what
you want; you can't readily generate a jump to arbitrary code.
Caveat: I can't prove the above, and someone may generate a bypass. But
I don't know of one.
Crispin Cowan, Ph.D. http://immunix.com/~crispin/
Chief Scientist, Immunix http://immunix.com