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 42CB7CCF9FA for ; Fri, 31 Oct 2025 11:28:44 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vEnIY-0005Vy-9z; Fri, 31 Oct 2025 07:28:02 -0400 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 1vEnIR-0005US-14 for qemu-devel@nongnu.org; Fri, 31 Oct 2025 07:27:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vEnI1-0001PN-9i for qemu-devel@nongnu.org; Fri, 31 Oct 2025 07:27:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761910037; 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=4L7lG7MOoqNduW6iirv7mIZh/hXVcTgK8iZWKB338Qk=; b=Zv2pDyqlMfWHqtFFk+Vrz2xxN0PbhlmeTpsvIJPmBipkiaADrMEqULi5NUtpbpePmNrEMc WqNyu9Zs6XNtQ+CBiR1yUY3eYdp9p2isZLg93XGAlb/0Ht5AV5YiG5LBCfT/RcyPiFxKdd NfON1qaO5KoGa7xUPd76SNclyRP7a+I= Received: from mx-prod-mc-03.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-399-SGLWdyOrNJ2qMdWboLSUNA-1; Fri, 31 Oct 2025 07:27:16 -0400 X-MC-Unique: SGLWdyOrNJ2qMdWboLSUNA-1 X-Mimecast-MFC-AGG-ID: SGLWdyOrNJ2qMdWboLSUNA_1761910035 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5AAE81956076; Fri, 31 Oct 2025 11:27:15 +0000 (UTC) Received: from redhat.com (dhcp-17-192.lcy.redhat.com [10.42.17.192]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2EAFA1800451; Fri, 31 Oct 2025 11:27:13 +0000 (UTC) Date: Fri, 31 Oct 2025 11:27:10 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Cc: qemu-devel@nongnu.org, devel@lists.libvirt.org Subject: Re: [PATCH 13/21] crypto: introduce a wrapper around gnutls credentials Message-ID: References: <20251030144927.2241109-1-berrange@redhat.com> <20251030144927.2241109-14-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: pass client-ip=170.10.129.124; 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-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 Fri, Oct 31, 2025 at 03:23:51PM +0400, Marc-André Lureau wrote: > Hi > > On Thu, Oct 30, 2025 at 6:49 PM Daniel P. Berrangé > wrote: > > > The gnutls_credentials_set() method has a very suprising API contract > > that requires the caller to preserve the passed in credentials pointer > > for as long as the gnutls_session_t object is alive. QEMU is failing > > to ensure this happens. > > > > In QEMU the GNUTLS credentials object is owned by the QCryptoTLSCreds > > object instance while the GNUTLS session object is owned by the > > QCryptoTLSSession object instance. Their lifetimes are not guaranteed > > to be the same, though in most common usage the credentials will outlive > > the session. This is notably not the case, however, after the VNC server > > gained the ability to reload credentials on the fly with: > > > > commit 1f08e3415120637cad7f540d9ceb4dba3136dbdd > > Author: Zihao Chang > > Date: Tue Mar 16 15:58:44 2021 +0800 > > > > vnc: support reload x509 certificates for vnc > > > > If that is triggered while a VNC client is in the middle of performing > > a TLS handshake, we might hit a use-after-free. > > > > It is difficult to correct this problem because there's no way to deep- > > clone a GNUTLS credentials object, nor is it reference counted. Thus we > > introduce a QCryptoTLSCredsBox object whose only purpose is to add > > reference counting around the GNUTLS credentials object. > > > > The DH parameters set against a credentials object also have to be kept > > alive for as long as the credentials exist. So the box must also hold > > the DH parameters pointer. > > > > Signed-off-by: Daniel P. Berrangé > > > > Reviewed-by: Marc-André Lureau > > +#ifndef QCRYPTO_TLSCREDS_BOX_H > > +#define QCRYPTO_TLSCREDS_BOX_H > > + > > +#include "qom/object.h" > > + > > +#ifdef CONFIG_GNUTLS > > +#include > > +#endif > > + > > +typedef struct QCryptoTLSCredsBox QCryptoTLSCredsBox; > > + > > +struct QCryptoTLSCredsBox { > > + uint32_t ref; > > + bool server; > > + int type; > > + union { > > + void *any; > > > > since any is used in code to cast the variant to a void *, it may be worth > a comment to say that all fields are expected to be pointers. Yep, in practice almost all gnutls _t types are pointers, but I'll explain that here since it is not obvious to casual observers. > > > > +#ifdef CONFIG_GNUTLS > > + gnutls_anon_server_credentials_t anonserver; > > + gnutls_anon_client_credentials_t anonclient; > > + gnutls_psk_server_credentials_t pskserver; > > + gnutls_psk_client_credentials_t pskclient; > > + gnutls_certificate_credentials_t cert; > > +#endif > > + } data; > > +#ifdef CONFIG_GNUTLS > > + gnutls_dh_params_t dh_params; > > +#endif > > +}; > > + 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 :|