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 lists1p.gnu.org (lists1p.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 6F51EC5AD4E for ; Mon, 10 Aug 2026 08:21:27 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wtLFL-0007Ik-2S; Mon, 10 Aug 2026 04:20:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wtLFC-0007IQ-6b for qemu-devel@nongnu.org; Mon, 10 Aug 2026 04:20:27 -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 1wtLFA-0003UV-D8 for qemu-devel@nongnu.org; Mon, 10 Aug 2026 04:20:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1786350022; 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=BuFT/VHr3JmxsXM1HudEx1ve2NWKe+MnwtZj/hEtwFs=; b=dlRHwPfIexd7QOE1kICfLiXhS036tSBuUBt7bSqxPbGzBE1eE3K3TpF/LSpSyexcYH6qpB hwEVZqg7IP/J4uyCtqqePzkXeOymHeWDjEkvh9uAFXb9j33eipZiNnQHAhY/NRSH6DvPiu Wce/inPJk01ndgu1wdRlZXoqfsApKY0= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-247-RmroBvZzMvuPIi1EOA0y8A-1; Mon, 10 Aug 2026 04:20:18 -0400 X-MC-Unique: RmroBvZzMvuPIi1EOA0y8A-1 X-Mimecast-MFC-AGG-ID: RmroBvZzMvuPIi1EOA0y8A_1786350017 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 375891800653; Mon, 10 Aug 2026 08:20:17 +0000 (UTC) Received: from redhat.com (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BBD721800347; Mon, 10 Aug 2026 08:20:15 +0000 (UTC) Date: Mon, 10 Aug 2026 09:20:12 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Kostiantyn Kostiuk Cc: Valentino Paulon , qemu-devel@nongnu.org, yvugenfi@redhat.com, michael.roth@amd.com Subject: Re: [PATCH] qga: Do not follow symlink in guest-ssh-* commands Message-ID: References: <20260709105707.91209-1-kkostiuk@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/2.4.0 (2026-06-19) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 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: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.827, 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, 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: qemu development 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, Aug 10, 2026 at 11:06:27AM +0300, Kostiantyn Kostiuk wrote: > Hi Valentino, > > Sorry for the long delay. > I have a question for you > > On Tue, Jul 14, 2026 at 7:10 PM Valentino Paulon < > valentino.paulon88@gmail.com> wrote: > > > > > So, you propose to call seteuid/setegid before any I/O operation? > > > > > > Yes, specifically for the SSH commands, because they're unusual in > > > that we're doing stuff on behalf of an unprivileged user. > > > > +1 on the euid/egid direction -- as the reporter that's the outcome I > > was hoping for. It confines every step (read, mkdir, create, rename, > > chown) to what the target user could already do himself, which removes > > the whole TOCTOU class instead of chasing one instance of it. > > > > A few implementation details that tend to bite with this pattern, in > > case they save a round-trip: > > > > - drop the supplementary groups too, not just egid: initgroups() (or > > setgroups() with the user's list) while still root, otherwise the > > agent's effective access won't match the user's in either direction > > > > Technically, there is no limitation to running QGA in unprivileged mode. > Normally, it is a system daemon, but this is not mandatory. > In this case, we can not call initgroups because the caller must > have CAP_SETGID. > We can call initgroups only when QGA runs as root. What do you think? In any practical sense it is a system daemon given the set of commands it is exposing. Thus, IMHO, deploying as an unprivileged user should be considered a broken deployment. We could make that explicit by refusing to launch. With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|