From owner-freebsd-performance@FreeBSD.ORG Thu Jun 26 20:06:02 2003 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0553B37B401 for ; Thu, 26 Jun 2003 20:06:02 -0700 (PDT) Received: from stoneport.math.uic.edu (stoneport.math.uic.edu [131.193.178.160]) by mx1.FreeBSD.org (Postfix) with SMTP id 534C043FEC for ; Thu, 26 Jun 2003 20:06:01 -0700 (PDT) (envelope-from djb-dsn-1056683193.18391@cr.yp.to) Received: (qmail 18392 invoked by uid 1017); 27 Jun 2003 03:06:33 -0000 Date: 27 Jun 2003 03:06:33 -0000 Message-ID: <20030627030633.18391.qmail@cr.yp.to> Automatic-Legal-Notices: See http://cr.yp.to/mailcopyright.html. From: "D. J. Bernstein" To: freebsd-performance@freebsd.org References: <20030626220945.75399.qmail@cr.yp.to> <3EFB9C92.4010807@mac.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: Re: sacrificing performance for confusion X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 27 Jun 2003 03:06:02 -0000 Chuck Swiger writes: > However, I will also acknowledge that it may be the case that it may be > possible for code to work around a non-executable stack In every case that I've investigated, not only is it definitely possible to seize control of the process with limited exec, it's actually fairly easy. Maybe there are counterexamples, but you obviously don't know any. (Note to certain people making fools of themselves: that's ``seize control,'' not ``kill.'') If disabling x bits becomes popular, attackers will start working around it, and we'll be back to where we are today. We need to stop the buffer overflows (and other problems) from occurring in the first place. Anyway, it seems unlikely that you believe that stack-x data-non-x makes life any more difficult for the attacker than stack-x data-x; and you obviously think that stack-non-x data-non-x would be the best situation. So why do you object to merging the stack and data segments? ---D. J. Bernstein, Associate Professor, Department of Mathematics, Statistics, and Computer Science, University of Illinois at Chicago