Bugtraq mailing list archives
Buffer overflow prevention
From: "Eygene A. Ryabinkin" <rea () rea mbslab kiae ru>
Date: Wed, 13 Aug 2003 14:28:33 +0400
Hi! I have an idea on buffer overflow prevention. I doubt that it's new, but I haven't seen an implementation of it in any freely distributable Un*x system. So, I hardly need your comments on it. Preliminary: I'm talking about Intel x86 architecture, but maybe it will be applicable to others as well. The idea itself: all (correct me if I'm wrong) buffer overflows are based on the fact that we're using the stack, referenced by SS:ESP pair, both for procedure return address and for local variables. It seems to me, that would we have two stacks -- one for real stack and one for variables -- it will solve a bunch of problems. So, my suggestion: let us organise two segments: one for normal stack, growing downwards, referenced by SS:ESP pair and the second one, for local variables, referenced by GS:EBP pair, with either upwards or downwards growing. Now, if we use first segment for passing variables and procedure return addresses (normal stack usage), and second segment only for local procedure variables, we will have the following advantages: 1) Local variables and return address will be physically (by means of CPU) divided and it will not be possible to touch the return address by overflowing local buffer. 2) The procedure introduces only one extra register -- GS, since EBP is very often used for the stack frame. Of course, this two segments can be made non-executable, just in case. What we need to implement the idea: first, rewrite kernel to organise two segments for every process and to place proper values into the segment registers upon the program startup. Second, rewrite the compiler to support the new scheme of local variables addresation. So, the changes are minimal, in some sence. As I said, I hardly need your criticism, suggestions, etc. of any type. rea
Current thread:
- Buffer overflow prevention Eygene A. Ryabinkin (Aug 13)
- Re: Buffer overflow prevention Nicholas Weaver (Aug 13)
- Re: Buffer overflow prevention weigelt (Aug 13)
- Re: Buffer overflow prevention Michal Zalewski (Aug 13)
- Re: Buffer overflow prevention weigelt (Aug 13)
- Re: Buffer overflow prevention Crispin Cowan (Aug 13)
- Re: Buffer overflow prevention Michal Zalewski (Aug 13)
- Re: Buffer overflow prevention Sam Baskinger (Aug 14)
- Re: Buffer overflow prevention Crispin Cowan (Aug 15)
- Re: Buffer overflow prevention weigelt (Aug 15)
- Re: Buffer overflow prevention Sam Baskinger (Aug 14)
- Re: Buffer overflow prevention Jonathan A. Zdziarski (Aug 13)
- Re: Buffer overflow prevention Andreas Beck (Aug 14)
(Thread continues...)
- Re: Buffer overflow prevention Nicholas Weaver (Aug 13)