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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B04A9C47DD3 for ; Mon, 22 Jan 2024 20:20:59 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rS0m0-0007wn-4Z; Mon, 22 Jan 2024 15:20:00 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rS0lx-0007wE-SX for qemu-devel@nongnu.org; Mon, 22 Jan 2024 15:19:57 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rS0lv-0006pc-SQ for qemu-devel@nongnu.org; Mon, 22 Jan 2024 15:19:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705954794; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=8NDP6GWEpopIKfodKNhjQVPUZP2gJpifnyTanF9jIfo=; b=igX8J/AdDwBiEOtc9QmoXQntRmjGfoCzN5mXmyBRzObP2fx+fPtnhCwcqsvmCSQaOl9+Vk h3P++ug/Qd2SlHwErcI6ckEliJbUnJtGnq0kwo929YfTx4j5frEZkBLcPZlodmVuG/wpnD id9PvbED6sVRVpC7QVj5XamShhD0v9E= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-314-V2EOq_VfNP6EVHmOax0P2w-1; Mon, 22 Jan 2024 15:19:50 -0500 X-MC-Unique: V2EOq_VfNP6EVHmOax0P2w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 92139848A11; Mon, 22 Jan 2024 20:19:46 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.36]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9D9C6295C; Mon, 22 Jan 2024 20:19:45 +0000 (UTC) Date: Mon, 22 Jan 2024 20:19:42 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Cristian =?utf-8?Q?Rodr=C3=ADguez?= Cc: "open list:All patches CC here" , "Jason A. Donenfeld" Subject: Re: [PATCH] crypto/gcrypt: prefer kernel as direct source of entropy Message-ID: References: <20240119203950.6434-1-cristian@rodriguez.im> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.10 (2023-03-25) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.289, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jan 22, 2024 at 05:08:16PM -0300, Cristian Rodríguez wrote: > On Mon, Jan 22, 2024 at 11:48 AM Daniel P. Berrangé > wrote: > > > On Fri, Jan 19, 2024 at 05:39:40PM -0300, Cristian Rodríguez wrote: > > > gcrypt by default uses an userspace RNG, which cannot know > > > when it is time to discard/invalidate its buffer > > > (suspend, resume, vm forks, other corner cases) > > > as a "when to discard" event is unavailable to userspace. > > > > So in this scenario QEMU is impacted when QEMU is running inside > > another VM. ie the L0 QEMU "forks" the guest, and the L1 QEMU > > needs to re-init its RNG. > > > > > Set GCRYCTL_SET_PREFERRED_RNG_TYPE to GCRY_RNG_TYPE_SYSTEM > > > which must be done before the first call to gcry_check_version() > > > > QEMU is just one out of many applications that use libgcrypt and > > I see no reason why QEMU should be special cased in this respect. > > > > Updating each application to hardcode use of GCRY_RNG_TYPE_SYSTEM > > does not feel like a good solution. If this was a good default > > to use everywhere, then gcrypt should have set this default > > already, rather than requiring every app to solve the forking > > problem itself. > > > > this default is because either other OSs had problems or in the past the > linux rng was not as performant as it is right now, > now it outputs 100's of MB per second on a potato. > > Updating every app that uses gcrypt is not really practical > > in terms of time investment anyway. > > > > Yeah, it will be pretty time consuming so I have so far only sent a few > patches for things I consider important. > > > > > If gcrypt doesn't want to make this its global default, then > > I would suggest that gcrypt should make its default be > > configurable. I see from its docs: > > > > > > https://gnupg.org/documentation/manuals/gcrypt/Configuration.html#Configuration > > > > that it already supports a /etc/gcrypt/random.conf file. > > Perhaps they would extend that to allow selection of the > > default RNG backend, system-wide. > > > And things will remain problematic by default , because of all the > obscurity and that FIPS mode overrides > all defaults you choose anyways, including if I hardcode the preference in > the source code like I did here. If the DRBG is required for FIPS compliance, and QEMU hardcoded the system RNG, then QEMU can't be used in a FIPS environment. So I still think this question of defaults is something to be fixed in the gcrypt code centrally, not in individual apps. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|