From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753500AbbFQK40 (ORCPT ); Wed, 17 Jun 2015 06:56:26 -0400 Received: from 251.110.2.81.in-addr.arpa ([81.2.110.251]:41530 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751095AbbFQK4S (ORCPT ); Wed, 17 Jun 2015 06:56:18 -0400 Date: Wed, 17 Jun 2015 11:55:20 +0100 From: One Thousand Gnomes To: "Theodore Ts'o" Cc: Josh Boyer , Eric Biederman , David Howells , kexec , "Linux-Kernel@Vger. Kernel. Org" Subject: Re: kexec_load(2) bypasses signature verification Message-ID: <20150617115520.5eec8224@lxorguk.ukuu.org.uk> In-Reply-To: <20150615200115.GG5003@thunk.org> References: <20150615035051.GA2634@thunk.org> <20150615131728.GK15793@thunk.org> <20150615200115.GG5003@thunk.org> Organization: Intel Corporation X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.28; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > [1] Yes, it doesn't buy all that much, since if the system is rooted > the adversary can just replace the kernel in /boot and force a normal, > slower reboot, but the same could be said for signed modules --- the > adversary could just replace all of /boot/vmlinux- and > /lib/modules/. But both measures make it a tad more bit > difficult, especially for the adversary to do this replacement without > being noticed (for example linode will send me e-mail if the system > reboots normally, but not with a kexec-mediated reboot), and for cloud > systems where we don't have secure boot anyway, it's about the best we > can do. It's about the same as the protection offered by the "secure" boot patches I've seen because they don't block all kernel boot parameters except a whitelist and because there are a pile of other fairly fundamental problems that probably require you also sign the root file system, which is itself a world of pain. Alan From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from 7.3.c.8.2.a.e.f.f.f.8.1.0.3.2.0.9.6.0.7.2.3.f.b.0.b.8.0.1.0.0.2.ip6.arpa ([2001:8b0:bf32:7069:230:18ff:fea2:8c37] helo=lxorguk.ukuu.org.uk) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Z5B0s-0003Na-AY for kexec@lists.infradead.org; Wed, 17 Jun 2015 10:56:11 +0000 Date: Wed, 17 Jun 2015 11:55:20 +0100 From: One Thousand Gnomes Subject: Re: kexec_load(2) bypasses signature verification Message-ID: <20150617115520.5eec8224@lxorguk.ukuu.org.uk> In-Reply-To: <20150615200115.GG5003@thunk.org> References: <20150615035051.GA2634@thunk.org> <20150615131728.GK15793@thunk.org> <20150615200115.GG5003@thunk.org> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Theodore Ts'o Cc: David Howells , Josh Boyer , kexec , Eric Biederman , "Linux-Kernel@Vger. Kernel. Org" > [1] Yes, it doesn't buy all that much, since if the system is rooted > the adversary can just replace the kernel in /boot and force a normal, > slower reboot, but the same could be said for signed modules --- the > adversary could just replace all of /boot/vmlinux- and > /lib/modules/. But both measures make it a tad more bit > difficult, especially for the adversary to do this replacement without > being noticed (for example linode will send me e-mail if the system > reboots normally, but not with a kexec-mediated reboot), and for cloud > systems where we don't have secure boot anyway, it's about the best we > can do. It's about the same as the protection offered by the "secure" boot patches I've seen because they don't block all kernel boot parameters except a whitelist and because there are a pile of other fairly fundamental problems that probably require you also sign the root file system, which is itself a world of pain. Alan _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec