Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755082AbXIFIBL (ORCPT ); Thu, 6 Sep 2007 04:01:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752932AbXIFIA6 (ORCPT ); Thu, 6 Sep 2007 04:00:58 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:44312 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752764AbXIFIA5 (ORCPT ); Thu, 6 Sep 2007 04:00:57 -0400 Date: Thu, 6 Sep 2007 13:44:05 +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: <20070830214431.GF10808@fieldses.org> 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: 1750 Lines: 40 On Thu, 30 Aug 2007, J. Bruce Fields wrote: > On Thu, Aug 30, 2007 at 11:04:00AM -0400, Trond Myklebust wrote: > > With CIFS or other password based protocols (including RPCSEC_GSS) > > Well, rpcsec_gss isn't inherently password based, and you can > authenticate in some way that doesn't actually give away your password > (or other long-lived credential). > > > 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 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 ;-) Satyam - 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/