From owner-freebsd-security Wed May 22 15:43:50 2002 Delivered-To: freebsd-security@freebsd.org Received: from mail.deltanet.com (mail.deltanet.com [216.237.144.132]) by hub.freebsd.org (Postfix) with ESMTP id 95B4437B405 for ; Wed, 22 May 2002 15:43:45 -0700 (PDT) Received: from mammoth.eat.frenchfries.net (da001d0308.lax-ca.osd.concentric.net [64.0.145.53]) by mail.deltanet.com (8.11.6/8.11.6) with ESMTP id g4MMMYO23152 for ; Wed, 22 May 2002 15:22:35 -0700 Received: by mammoth.eat.frenchfries.net (Postfix, from userid 1000) id 6DDF952A6; Wed, 22 May 2002 15:41:53 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by mammoth.eat.frenchfries.net (Postfix) with ESMTP id 6B46A529A; Wed, 22 May 2002 15:41:53 -0700 (PDT) Date: Wed, 22 May 2002 15:41:53 -0700 (PDT) From: Paul Herman X-X-Sender: pherman@mammoth.eat.frenchfries.net To: Stephanie Wehner <_@r4k.net> Cc: freebsd-security@FreeBSD.ORG Subject: Re: file flags in /modules In-Reply-To: <20020522194304.GA70619@r4k.net> Message-ID: <20020522151939.I51256-100000@mammoth.eat.frenchfries.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Wed, 22 May 2002, Stephanie Wehner wrote: > Is there any particular reason why the immutable flag is turned > on for /kernel, but not for any loadable modules ? Facetious answer: Yes. To make you think more about security. :-) Informative answer: What good would it do? Assuming securelevel > 0, the kernel won't let you kldload(2) modules anyway. You could rightly argue that someone could overwrite a particular module and then reboot the machine in order to have it loaded, but then /modules wouldn't be your only worry. You'd have to protect many files, including but not limited to: /modules /etc/rc /etc/rc.* /usr/local/etc/rc.d/* /boot/* /bin, /sbin, /usr/lib, and so on... Which renders systems less usable than most people would like. You don't want to go down that road. securelevel is a nice comprimise for most people, but it has its limitations. If this is important to you, you might look into mandatory access control systems used in trusted systems, like TrustedBSD. -Paul. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message