From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5634BC07E85 for ; Fri, 7 Dec 2018 06:39:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1AC7C20838 for ; Fri, 7 Dec 2018 06:39:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1AC7C20838 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-security-module-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725950AbeLGGjZ (ORCPT ); Fri, 7 Dec 2018 01:39:25 -0500 Received: from mga05.intel.com ([192.55.52.43]:58382 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725948AbeLGGjZ (ORCPT ); Fri, 7 Dec 2018 01:39:25 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Dec 2018 22:39:24 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,324,1539673200"; d="scan'208";a="116762644" Received: from makoli-mobl1.amr.corp.intel.com (HELO localhost) ([10.254.201.154]) by orsmga001.jf.intel.com with ESMTP; 06 Dec 2018 22:39:20 -0800 Date: Thu, 6 Dec 2018 22:39:19 -0800 From: Jarkko Sakkinen To: "Huang, Kai" Cc: "tglx@linutronix.de" , "Schofield, Alison" , "dhowells@redhat.com" , "kirill.shutemov@linux.intel.com" , "peterz@infradead.org" , "jmorris@namei.org" , "keyrings@vger.kernel.org" , "linux-mm@kvack.org" , "linux-security-module@vger.kernel.org" , "Williams, Dan J" , "x86@kernel.org" , "hpa@zytor.com" , "mingo@redhat.com" , "luto@kernel.org" , "bp@alien8.de" , "Hansen, Dave" , "Nakajima, Jun" Subject: Re: [RFC v2 12/13] keys/mktme: Save MKTME data if kernel cmdline parameter allows Message-ID: <20181207063918.GB12969@intel.com> References: <1544148839.28511.28.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1544148839.28511.28.camel@intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Thu, Dec 06, 2018 at 06:14:03PM -0800, Huang, Kai wrote: > On Mon, 2018-12-03 at 23:39 -0800, Alison Schofield wrote: > > MKTME (Multi-Key Total Memory Encryption) key payloads may include > > data encryption keys, tweak keys, and additional entropy bits. These > > are used to program the MKTME encryption hardware. By default, the > > kernel destroys this payload data once the hardware is programmed. > > > > However, in order to fully support CPU Hotplug, saving the key data > > becomes important. The MKTME Key Service cannot allow a new physical > > package to come online unless it can program the new packages Key Table > > to match the Key Tables of all existing physical packages. > > > > With CPU generated keys (a.k.a. random keys or ephemeral keys) the > > saving of user key data is not an issue. The kernel and MKTME hardware > > can generate strong encryption keys without recalling any user supplied > > data. > > > > With USER directed keys (a.k.a. user type) saving the key programming > > data (data and tweak key) becomes an issue. The data and tweak keys > > are required to program those keys on a new physical package. > > > > In preparation for adding CPU hotplug support: > > > > Add an 'mktme_vault' where key data is stored. > > > > Add 'mktme_savekeys' kernel command line parameter that directs > > what key data can be stored. If it is not set, kernel does not > > store users data key or tweak key. > > > > Add 'mktme_bitmap_user_type' to track when USER type keys are in > > use. If no USER type keys are currently in use, a physical package > > may be brought online, despite the absence of 'mktme_savekeys'. > > Overall, I am not sure whether saving key is good idea, since it > breaks coldboot attack IMHO. We need to tradeoff between supporting > CPU hotplug and security. I am not sure whether supporting CPU hotplug > is that important, since for some other features such as SGX, we don't > support CPU hotplug anyway. What is the application for saving the key anyway? With my current knowledge, I'm not even sure what is the application for user provided keys. /Jarkko