From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752104AbcFUN1o (ORCPT ); Tue, 21 Jun 2016 09:27:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60243 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752013AbcFUN1m (ORCPT ); Tue, 21 Jun 2016 09:27:42 -0400 Message-ID: <1466515196.17017.8.camel@redhat.com> Subject: Re: [PATCH v4 0/5] /dev/random - a new approach From: Tomas Mraz To: "Austin S. Hemmelgarn" , Stephan Mueller Cc: "Theodore Ts'o" , David =?UTF-8?Q?Ja=C5=A1a?= , Andi Kleen , sandyinchina@gmail.com, Jason Cooper , John Denker , "H. Peter Anvin" , Joe Perches , Pavel Machek , George Spelvin , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 21 Jun 2016 15:19:56 +0200 In-Reply-To: <6b8c8f6a-862a-3e7c-e950-75cd93cdc1f7@gmail.com> References: <1466007463.20087.11.camel@redhat.com> <3381856.qSaz1KcX2Z@positron.chronox.de> <8999970.pstTbGZv5G@positron.chronox.de> <6b8c8f6a-862a-3e7c-e950-75cd93cdc1f7@gmail.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Tue, 21 Jun 2016 13:20:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Út, 2016-06-21 at 09:05 -0400, Austin S. Hemmelgarn wrote: > On 2016-06-20 14:32, Stephan Mueller wrote: > >  > > [1] http://www.chronox.de/jent/doc/CPU-Jitter-NPTRNG.pdf > Specific things I notice about this: > 1. QEMU systems are reporting higher values than almost anything > else  > with the same ISA.  This makes sense, but you don't appear to have  > accounted for the fact that you can't trust almost any of the entropy > in  > a VM unless you have absolute trust in the host system, because the > host  > system can do whatever the hell it wants to you, including > manipulating  > timings directly (with a little patience and some time spent working > on  > it, you could probably get those number to show whatever you want > just  > by manipulating scheduling parameters on the host OS for the VM > software). You have to trust the host for anything, not just for the entropy in timings. This is completely invalid argument unless you can present a method that one guest can manipulate timings in other guest in such a way that _removes_ the inherent entropy from the host. --  Tomas Mraz No matter how far down the wrong road you've gone, turn back. Turkish proverb (You'll never know whether the road is wrong though.)