From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:35902) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hMaOI-0007kd-RX for qemu-devel@nongnu.org; Fri, 03 May 2019 11:46:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hMaOG-0000Nk-LX for qemu-devel@nongnu.org; Fri, 03 May 2019 11:46:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35000) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hMaOG-0000Lo-0H for qemu-devel@nongnu.org; Fri, 03 May 2019 11:46:24 -0400 From: Kashyap Chamarthy Date: Fri, 3 May 2019 17:46:12 +0200 Message-Id: <20190503154613.4192-1-kchamart@redhat.com> Subject: [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: qemu-devel@nongnu.org Cc: amit@kernel.org, armbru@redhat.com, rjones@redhat.com, berrange@redhat.com, Kashyap Chamarthy 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 e2a49b0571d79eab335d5a74841d92c50a727b6a..eff36ef14084bccaad1eabe952e2cf6ffa9a2529 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 51802cbb266a208d70989c4f0ab3317a76edc1ea..a525609149e4d0e4bb60959f029a1a16eb36900d 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} -- 2.17.2 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=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 6D0C1C43219 for ; Fri, 3 May 2019 15:48:12 +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 4385F2081C for ; Fri, 3 May 2019 15:48:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4385F2081C 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]:42482 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hMaPz-0000E2-E1 for qemu-devel@archiver.kernel.org; Fri, 03 May 2019 11:48:11 -0400 Received: from eggs.gnu.org ([209.51.188.92]:35902) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hMaOI-0007kd-RX for qemu-devel@nongnu.org; Fri, 03 May 2019 11:46:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hMaOG-0000Nk-LX for qemu-devel@nongnu.org; Fri, 03 May 2019 11:46:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35000) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hMaOG-0000Lo-0H for qemu-devel@nongnu.org; Fri, 03 May 2019 11:46:24 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 73D22C00735C; Fri, 3 May 2019 15:46:22 +0000 (UTC) Received: from paraplu.redhat.com (ovpn-116-130.ams2.redhat.com [10.36.116.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id 79C3550C55; Fri, 3 May 2019 15:46:19 +0000 (UTC) From: Kashyap Chamarthy To: qemu-devel@nongnu.org Date: Fri, 3 May 2019 17:46:12 +0200 Message-Id: <20190503154613.4192-1-kchamart@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Fri, 03 May 2019 15:46:22 +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: [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: rjones@redhat.com, Kashyap Chamarthy , armbru@redhat.com, amit@kernel.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="UTF-8" Message-ID: <20190503154612.ppgvvV44VeNnObTv63NyNWDHEsUe9L1dR8wMjU2FLGw@z> 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 e2a49b0571d79eab335d5a74841d92c50a727b6a..eff36ef14084bccaad1eabe952e2cf6ffa9a2529 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 51802cbb266a208d70989c4f0ab3317a76edc1ea..a525609149e4d0e4bb60959f029a1a16eb36900d 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} -- 2.17.2