Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755418AbXIFIQs (ORCPT ); Thu, 6 Sep 2007 04:16:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753297AbXIFIQl (ORCPT ); Thu, 6 Sep 2007 04:16:41 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:51487 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753265AbXIFIQk (ORCPT ); Thu, 6 Sep 2007 04:16:40 -0400 Date: Thu, 6 Sep 2007 13:59:50 +0530 (IST) From: Satyam Sharma X-X-Sender: satyam@enigma.security.iitk.ac.in To: "J. Bruce Fields" cc: Trond Myklebust , Jan Engelhardt , Linux Kernel Mailing List Subject: Re: NFS4 authentification / fsuid In-Reply-To: Message-ID: References: <1188484155.6755.38.camel@heimdal.trondhjem.org> <1188484337.6755.41.camel@heimdal.trondhjem.org> <1188486240.6755.51.camel@heimdal.trondhjem.org> <20070830214431.GF10808@fieldses.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1861 Lines: 42 On Thu, 6 Sep 2007, Satyam Sharma wrote: > > On Thu, 30 Aug 2007, J. Bruce Fields wrote: > > > On Thu, Aug 30, 2007 at 11:04:00AM -0400, Trond Myklebust wrote: > > > > > What I'm saying is that the superuser can pretty much do whatever it > > > takes to grab either your kerberos password (e.g. install a keyboard > > > listener), a stored credential (read the contents of your kerberos > > > on-disk credential cache), or s/he can access the cached contents of the > > > file by hunting through /dev/kmem. > > > > > > IOW: There is no such thing as security on a root-compromised machine. > > > > And in theory a kernel could provide *some* guarantees against root, > > right? (Is there some reason a unix-like kernel must provide such > > things as /dev/kmem?) > > /dev/kmem was just an example -- IMHO differentiating between kernel and > userspace from a security p.o.v. is always tricky. Like Trond said, there > are very high number of ways in which privileged userspace can compromise > a running kernel if it really wants to do that, root-is-God has always ^^^^^^^^^^^^^^ Oh and btw, note that we're talking of the (lack of) security of a "running kernel" here -- because across reboots, there is /really/ *absolutely* no such thing as "kernelspace security" because the superuser will simply switch the vmlinuz itself ... > been *the* major problem with Unix :-) > > The only _real_ way a kernel can lock itself completely against malicious > userspace involves trusted tamperproof hardware, but even that only if > you can get yourself to believe such a thing exists in the first place ;-) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/