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 AC825C02194 for ; Tue, 4 Feb 2025 15:11:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tfKa0-0005dd-J5; Tue, 04 Feb 2025 10:11:12 -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 1tfKZx-0005d5-JE for qemu-devel@nongnu.org; Tue, 04 Feb 2025 10:11:09 -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 1tfKZv-0006hD-MP for qemu-devel@nongnu.org; Tue, 04 Feb 2025 10:11:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738681866; 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:in-reply-to:in-reply-to: references:references; bh=QSsQg4uvCIcJhgzplszGguykLuhW0HQivP56iy/FG3Q=; b=UWBj3SqGdC4pm4F9kO5W8qNOcx9lX2nh4xURPKVIr4OrUqiHxLN9x1MCrGlCz2YbW/AE+Z rAj9JLJmE855rJwOVkFrKGfceGWI5uTwbriNcbuuQH1OuKHQMmsO4eStpR43BRkMj4yrHj /8PxMHZFz4yYkMvnWdipipexeBQG/FM= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-244-lUBYEjkWNZuZDgA367ua6g-1; Tue, 04 Feb 2025 10:11:03 -0500 X-MC-Unique: lUBYEjkWNZuZDgA367ua6g-1 X-Mimecast-MFC-AGG-ID: lUBYEjkWNZuZDgA367ua6g Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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 mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6B1171955DBA; Tue, 4 Feb 2025 15:11:02 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.60]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3621E30001BE; Tue, 4 Feb 2025 15:10:56 +0000 (UTC) Date: Tue, 4 Feb 2025 15:10:53 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: "Maciej S. Szmigiero" , Fabiano Rosas , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eric Blake , Markus Armbruster , Avihai Horon , Joao Martins , qemu-devel@nongnu.org Subject: Re: [PATCH v4 08/33] migration/multifd: Allow premature EOF on TLS incoming channels Message-ID: References: <67a7c2ce-2391-4b8e-a5be-bce370fd2e66@maciej.szmigiero.name> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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, Feb 03, 2025 at 03:20:50PM -0500, Peter Xu wrote: > On Mon, Feb 03, 2025 at 07:53:00PM +0100, Maciej S. Szmigiero wrote: > > On 3.02.2025 19:20, Peter Xu wrote: > > > On Thu, Jan 30, 2025 at 11:08:29AM +0100, Maciej S. Szmigiero wrote: > > > > From: "Maciej S. Szmigiero" > > > > > > > > Multifd send channels are terminated by calling > > > > qio_channel_shutdown(QIO_CHANNEL_SHUTDOWN_BOTH) in > > > > multifd_send_terminate_threads(), which in the TLS case essentially > > > > calls shutdown(SHUT_RDWR) on the underlying raw socket. > > > > > > > > Unfortunately, this does not terminate the TLS session properly and > > > > the receive side sees this as a GNUTLS_E_PREMATURE_TERMINATION error. > > > > > > > > The only reason why this wasn't causing migration failures is because > > > > the current migration code apparently does not check for migration > > > > error being set after the end of the multifd receive process. > > > > > > > > However, this will change soon so the multifd receive code has to be > > > > prepared to not return an error on such premature TLS session EOF. > > > > Use the newly introduced QIOChannelTLS method for that. > > > > > > > > It's worth noting that even if the sender were to be changed to terminate > > > > the TLS connection properly the receive side still needs to remain > > > > compatible with older QEMU bit stream which does not do this. > > > > > > If this is an existing bug, we could add a Fixes. > > > > It is an existing issue but only uncovered by this patch set. > > > > As far as I can see it was always there, so it would need some > > thought where to point that Fixes tag. > > If there's no way to trigger a real functional bug anyway, it's also ok we > omit the Fixes. > > > > Two pure questions.. > > > > > > - What is the correct way to terminate the TLS session without this flag? > > > > I guess one would need to call gnutls_bye() like in this GnuTLS example: > > https://gitlab.com/gnutls/gnutls/-/blob/2b8c3e4c71ad380bbbffb32e6003b34ecad596e3/doc/examples/ex-client-anon.c#L102 > > > > > - Why this is only needed by multifd sessions? > > > > What uncovered the issue was switching the load threads to using > > migrate_set_error() instead of their own result variable > > (load_threads_ret) which you had requested during the previous > > patch set version review: > > https://lore.kernel.org/qemu-devel/Z1DbH5fwBaxtgrvH@x1n/ > > > > Turns out that the multifd receive code always returned > > error in the TLS case, just nothing was previously checking for > > that error presence. > > What I was curious is whether this issue also exists for the main migration > channel when with tls, especially when e.g. multifd not enabled at all. As > I don't see anywhere that qemu uses gnutls_bye() for any tls session. We've been lazy and avoided using gnutls_bye because it adds a bunch more complexity to the shutdown sequence, and premature shutdown from an malicious attack would be expected to cause the QEMU protocol in the TLS channel to fail anyway. > Does it mean we need proper gnutls_bye() somewhere? Depends if the protocol we run over TLS can identify premature termination itself, or whether it relies on TLS to identify it. 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 :|