From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [IPv6:2a0f:8001:1:32::40]) by lore.proxmox.com (Postfix) with ESMTPS id AC66B1FF0E5 for ; Wed, 29 Jul 2026 12:07:57 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 8D8EA213A7; Wed, 29 Jul 2026 12:07:56 +0200 (CEST) Date: Wed, 29 Jul 2026 12:07:29 +0200 From: Fabian =?iso-8859-1?q?Gr=FCnbichler?= Subject: Re: [RFC qemu-server 1/4] remote migrate: drop ineffective fingerprint auto-detection To: Erik Fastermann , Fiona Ebner , pve-devel@lists.proxmox.com References: <20260721115827.163442-1-e.fastermann@proxmox.com> <20260721115827.163442-2-e.fastermann@proxmox.com> In-Reply-To: MIME-Version: 1.0 User-Agent: astroid/0.17.0 (https://github.com/astroidmail/astroid) Message-Id: <1785319378.5wn648ra0k.astroid@yuna.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1785319613803 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.148 Adjusted score from AWL reputation of From: address DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment (newer systems) RCVD_IN_DNSWL_LOW -0.7 Sender listed at https://www.dnswl.org/, low trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: 64CE2KT3J3KMWCQXAHJKFPCUGR5DHXHJ X-Message-ID-Hash: 64CE2KT3J3KMWCQXAHJKFPCUGR5DHXHJ X-MailFrom: f.gruenbichler@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On July 29, 2026 11:56 am, Fiona Ebner wrote: > Am 21.07.26 um 1:58 PM schrieb Erik Fastermann: >> When no fingerprint was supplied, the code fetched the remote node >> certificate and pinned its fingerprint for the migration tunnel. This >> has no functional effect and is removed. >>=20 >> That fetch only succeeds for remotes trusted via the CA store, which >> is exactly the case where pinning is unnecessary: both the API client >> and the websocket tunnel fall back to CA verification on their own. >> For a self-signed remote the fetch itself fails verification, so no >> fingerprint is ever obtained. >=20 > The websocket tunnel checks the pinned fingerprint against the one that > was supplied, so with the current code any weird scenario where the > fingerprint queried from the certificates API endpoint does not match > the one gotten later by the websocket tunnel connection is caught. If > you remove the pinning, such scenarios won't be caught anymore. Not sure > how important that is though. >=20 > @Fabian what do you think? Erik actually asked me about this before sending the RFC (@Erik - feel free to mention such things in the "notes" part of a patch). I don't think it really buys us much, and AFAICT it breaks in the following case with a certificate trusted by the system: - certificate info queried - cert rotated - websocket tunnel established -> wrong fingerprint because the websocket tunnel will only check the fingerprint if one is provided. so IMHO, this should be removed.