From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932425AbdJYSxz (ORCPT ); Wed, 25 Oct 2017 14:53:55 -0400 Received: from mga04.intel.com ([192.55.52.120]:36672 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932162AbdJYSxw (ORCPT ); Wed, 25 Oct 2017 14:53:52 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,432,1503385200"; d="scan'208";a="913718887" Date: Wed, 25 Oct 2017 20:53:49 +0200 From: Jarkko Sakkinen To: Matthew Garrett Cc: linux-integrity , Kari Hiitola , linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Alexander Steffen Subject: Re: Fixing CVE-2017-15361 Message-ID: <20171025185349.ocptudim3g35j6im@linux.intel.com> References: <20171025134438.vgh6tzkups2tujps@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 25, 2017 at 07:17:17AM -0700, Matthew Garrett wrote: > On Wed, Oct 25, 2017 at 6:44 AM, Jarkko Sakkinen > wrote: > > I'm implementing a fix for CVE-2017-15361 that simply blacklists > > vulnerable FW versions. I think this is the only responsible action from > > my side that I can do. > > I'm not sure this is ideal - do Infineon have any Linux tooling for > performing firmware updates, and if so will that continue working if > the device is blacklisted? It's also a poor user experience to have > systems using TPM-backed disk encryption keys suddenly rendered > unbootable, and making it as easy as possible for people to do an > upgrade and then re-seal secrets with new keys feels like the correct > approach. I talked today with Alexander Steffen in the KS unconference and we concluded that this would be a terrible idea. Alexander stated the following things about FW updates (Alexander, please correct me if I state something incorrectly or if you have something to add): * FW update can be constructed either in a way that the keys in the NVRAM are not cleared or in a way that they are cleared. * FW update cannot be directly applied to the TPM but must come as part of the firmware update from the vendor. I proposed the following as an alternative: * Print a message to the klog (which log level would be appropriate?). * Possibly sleep for few seconds. Is this a good idea? While writing this email yet another alternative popped into my mind: what if we allow only in-kernel use but disallow the use of /dev/tpm0? You could still use trusted keys. Here are all the ideas that I have and I am open for better alternatives. /Jarkko