From owner-freebsd-security Tue Dec 19 14:28:59 2000 From owner-freebsd-security@FreeBSD.ORG Tue Dec 19 14:28:57 2000 Return-Path: Delivered-To: freebsd-security@freebsd.org Received: from mailhost01.reflexnet.net (mailhost01.reflexnet.net [64.6.192.82]) by hub.freebsd.org (Postfix) with ESMTP id 6895C37B402 for ; Tue, 19 Dec 2000 14:28:57 -0800 (PST) Received: from rfx-64-6-211-149.users.reflexcom.com ([64.6.211.149]) by mailhost01.reflexnet.net with Microsoft SMTPSVC(5.5.1877.197.19); Tue, 19 Dec 2000 14:27:19 -0800 Received: (from cjc@localhost) by rfx-64-6-211-149.users.reflexcom.com (8.11.0/8.11.0) id eBJMStT26698; Tue, 19 Dec 2000 14:28:55 -0800 (PST) (envelope-from cjc) Date: Tue, 19 Dec 2000 14:28:55 -0800 From: "Crist J. Clark" To: Warner Losh Cc: freebsd-security@FreeBSD.ORG Subject: Re: Read-Only Filesystems Message-ID: <20001219142855.E23819@rfx-64-6-211-149.users.reflexco> Reply-To: cjclark@alum.mit.edu References: <20001219114936.A23819@rfx-64-6-211-149.users.reflexco> <200012192210.PAA03943@harmony.village.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0i In-Reply-To: <200012192210.PAA03943@harmony.village.org>; from imp@village.org on Tue, Dec 19, 2000 at 03:10:34PM -0700 Sender: cjc@rfx-64-6-211-149.users.reflexcom.com Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Tue, Dec 19, 2000 at 03:10:34PM -0700, Warner Losh wrote: > In message <20001219114936.A23819@rfx-64-6-211-149.users.reflexco> "Crist J. Clark" writes: > : I was recently playing around with the idea of having a read-only root > : filesystem. However, it has become clear that there is no way to > : prevent root from changing the mount properties on any filesystem, > : including the root filesystem, provided there is no hardware-level > : block on writing and there is someplace (anyplace) where root can > : write. > > That is correct. mount -uw / works, even at high security levels. You can actually break that (in a dangerous way), but provided there is any other filesystem not blocked by a hardware-level, read-only block, you can then work around it. -- Crist J. Clark cjclark@alum.mit.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message