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 820C8C07E85 for ; Fri, 7 Dec 2018 03:39:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4916E2083D for ; Fri, 7 Dec 2018 03:39:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4916E2083D 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 S1725999AbeLGDjt (ORCPT ); Thu, 6 Dec 2018 22:39:49 -0500 Received: from mga14.intel.com ([192.55.52.115]:2236 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725939AbeLGDjt (ORCPT ); Thu, 6 Dec 2018 22:39:49 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Dec 2018 19:39:48 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,324,1539673200"; d="scan'208";a="98765078" Received: from alison-desk.jf.intel.com ([10.54.74.53]) by orsmga006.jf.intel.com with ESMTP; 06 Dec 2018 19:39:48 -0800 Date: Thu, 6 Dec 2018 19:42:17 -0800 From: Alison Schofield To: "Huang, Kai" Cc: "tglx@linutronix.de" , "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" , "Sakkinen, Jarkko" , "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: <20181207034217.GA13388@alison-desk.jf.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> User-Agent: Mutt/1.5.24 (2015-08-30) 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: 8< ------------ > > 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. Yes, saving the key data exposes it in a cold boot attack. Here we have 2 conflicting requirements. Do not save the data and support CPU hotplug. I don't think CPU hotplug support is budging! If the risk of offering the mktme_savekeys option is too dangerous, then we can't have user type keys. Is mktme_savekeys options too risky to offer? (That's not just a question for you Kai ;). I'll pursue too.) > > Alternatively, we can choose to use per-socket keyID, but not to program keyID globally across all > sockets, so you don't have to save key while still supporting CPU hotplug. An alternative, with a lot of impact to the core linux support for MKTME. I don't think we need to go there. I'll leave this thought for a Kirill or Dave to perhaps elaborate on. Alison > > Thanks, > -Kai