From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:42543) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hMami-0006ZN-AY for qemu-devel@nongnu.org; Fri, 03 May 2019 12:11:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hMamg-0005In-VF for qemu-devel@nongnu.org; Fri, 03 May 2019 12:11:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42158) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hMamg-0005Hs-Pt for qemu-devel@nongnu.org; Fri, 03 May 2019 12:11:38 -0400 Date: Fri, 3 May 2019 17:11:35 +0100 From: "Richard W.M. Jones" Message-ID: <20190503161135.GW3926@redhat.com> References: <20190503154613.4192-1-kchamart@redhat.com> <20190503154613.4192-2-kchamart@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190503154613.4192-2-kchamart@redhat.com> Subject: Re: [Qemu-devel] [PATCH] VirtIO-RNG: Update default entropy source to `/dev/urandom` List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kashyap Chamarthy Cc: qemu-devel@nongnu.org, amit@kernel.org, armbru@redhat.com, berrange@redhat.com On Fri, May 03, 2019 at 05:46:13PM +0200, Kashyap Chamarthy wrote: > When QEMU exposes a VirtIO-RNG device to the guest, that device needs a > source of entropy, and that source needs to be "non-blocking", like > `/dev/urandom`. However, currently QEMU defaults to the problematic > `/dev/random`, which is "blocking" (as in, it waits until sufficient > entropy is available). > > So change the entropy source to the recommended `/dev/urandom`. > > Related discussion in these[1][2] past threads. > > [1] https://lists.nongnu.org/archive/html/qemu-devel/2018-06/msg08335.html > -- "RNG: Any reason QEMU doesn't default to `/dev/urandom`?" > [2] https://lists.nongnu.org/archive/html/qemu-devel/2018-09/msg02724.html > -- "[RFC] Virtio RNG: Consider changing the default entropy source to > /dev/urandom" > > Signed-off-by: Kashyap Chamarthy > --- > backends/rng-random.c | 2 +- > qemu-options.hx | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/backends/rng-random.c b/backends/rng-random.c > index e2a49b0571..eff36ef140 100644 > --- a/backends/rng-random.c > +++ b/backends/rng-random.c > @@ -112,7 +112,7 @@ static void rng_random_init(Object *obj) > rng_random_set_filename, > NULL); > > - s->filename = g_strdup("/dev/random"); > + s->filename = g_strdup("/dev/urandom"); > s->fd = -1; > } > > diff --git a/qemu-options.hx b/qemu-options.hx > index 51802cbb26..a525609149 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -4276,7 +4276,7 @@ Creates a random number generator backend which obtains entropy from > a device on the host. The @option{id} parameter is a unique ID that > will be used to reference this entropy backend from the @option{virtio-rng} > device. The @option{filename} parameter specifies which file to obtain > -entropy from and if omitted defaults to @option{/dev/random}. > +entropy from and if omitted defaults to @option{/dev/urandom}. > > @item -object rng-egd,id=@var{id},chardev=@var{chardevid} I think this is a very sensible change, removing a bit of superstition about randomness. Reviewed-by: Richard W.M. Jones Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW 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=-7.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, URIBL_SBL,URIBL_SBL_A,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 5B0E6C43219 for ; Fri, 3 May 2019 16:12:52 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2836C20651 for ; Fri, 3 May 2019 16:12:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2836C20651 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:43072 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hManr-00076l-Ay for qemu-devel@archiver.kernel.org; Fri, 03 May 2019 12:12:51 -0400 Received: from eggs.gnu.org ([209.51.188.92]:42543) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hMami-0006ZN-AY for qemu-devel@nongnu.org; Fri, 03 May 2019 12:11:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hMamg-0005In-VF for qemu-devel@nongnu.org; Fri, 03 May 2019 12:11:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42158) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hMamg-0005Hs-Pt for qemu-devel@nongnu.org; Fri, 03 May 2019 12:11:38 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5C9FAC05E76E; Fri, 3 May 2019 16:11:37 +0000 (UTC) Received: from localhost (ovpn-116-243.ams2.redhat.com [10.36.116.243]) by smtp.corp.redhat.com (Postfix) with ESMTP id DCED860BFB; Fri, 3 May 2019 16:11:36 +0000 (UTC) Date: Fri, 3 May 2019 17:11:35 +0100 From: "Richard W.M. Jones" To: Kashyap Chamarthy Message-ID: <20190503161135.GW3926@redhat.com> References: <20190503154613.4192-1-kchamart@redhat.com> <20190503154613.4192-2-kchamart@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190503154613.4192-2-kchamart@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 03 May 2019 16:11:37 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH] VirtIO-RNG: Update default entropy source to `/dev/urandom` X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: armbru@redhat.com, qemu-devel@nongnu.org, amit@kernel.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Message-ID: <20190503161135.fAqvMMNREPL2wWQJrnUzcd1rB6I313flp7wgb43FVuY@z> On Fri, May 03, 2019 at 05:46:13PM +0200, Kashyap Chamarthy wrote: > When QEMU exposes a VirtIO-RNG device to the guest, that device needs a > source of entropy, and that source needs to be "non-blocking", like > `/dev/urandom`. However, currently QEMU defaults to the problematic > `/dev/random`, which is "blocking" (as in, it waits until sufficient > entropy is available). > > So change the entropy source to the recommended `/dev/urandom`. > > Related discussion in these[1][2] past threads. > > [1] https://lists.nongnu.org/archive/html/qemu-devel/2018-06/msg08335.html > -- "RNG: Any reason QEMU doesn't default to `/dev/urandom`?" > [2] https://lists.nongnu.org/archive/html/qemu-devel/2018-09/msg02724.html > -- "[RFC] Virtio RNG: Consider changing the default entropy source to > /dev/urandom" > > Signed-off-by: Kashyap Chamarthy > --- > backends/rng-random.c | 2 +- > qemu-options.hx | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/backends/rng-random.c b/backends/rng-random.c > index e2a49b0571..eff36ef140 100644 > --- a/backends/rng-random.c > +++ b/backends/rng-random.c > @@ -112,7 +112,7 @@ static void rng_random_init(Object *obj) > rng_random_set_filename, > NULL); > > - s->filename = g_strdup("/dev/random"); > + s->filename = g_strdup("/dev/urandom"); > s->fd = -1; > } > > diff --git a/qemu-options.hx b/qemu-options.hx > index 51802cbb26..a525609149 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -4276,7 +4276,7 @@ Creates a random number generator backend which obtains entropy from > a device on the host. The @option{id} parameter is a unique ID that > will be used to reference this entropy backend from the @option{virtio-rng} > device. The @option{filename} parameter specifies which file to obtain > -entropy from and if omitted defaults to @option{/dev/random}. > +entropy from and if omitted defaults to @option{/dev/urandom}. > > @item -object rng-egd,id=@var{id},chardev=@var{chardevid} I think this is a very sensible change, removing a bit of superstition about randomness. Reviewed-by: Richard W.M. Jones Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW