From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp1 ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by ms11 with LMTPS id GA06I7xRGWCkYAAA0tVLHw (envelope-from ) for ; Tue, 02 Feb 2021 13:21:00 +0000 Received: from aspmx1.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp1 with LMTPS id sFjnHrxRGWBrBwAAbx9fmQ (envelope-from ) for ; Tue, 02 Feb 2021 13:21:00 +0000 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 aspmx1.migadu.com (Postfix) with ESMTPS id 4F6789402BD for ; Tue, 2 Feb 2021 13:21:00 +0000 (UTC) Received: from localhost ([::1]:44628 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l6vc3-0003Aw-Af for larch@yhetil.org; Tue, 02 Feb 2021 08:20:59 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:50734) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l6vPK-0003bp-4r for guix-devel@gnu.org; Tue, 02 Feb 2021 08:07:51 -0500 Received: from fencepost.gnu.org ([2001:470:142:3::e]:44851) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l6vPJ-0000lD-2E; Tue, 02 Feb 2021 08:07:49 -0500 Received: from [2a01:e0a:1d:7270:af76:b9b:ca24:c465] (port=54890 helo=ribbon) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1l6vPG-0006sp-BF; Tue, 02 Feb 2021 08:07:48 -0500 From: =?utf-8?Q?Ludovic_Court=C3=A8s?= To: Maxime Devos Subject: Re: Potential security weakness in Guix services References: <87k0rrls0z.fsf@gnu.org> <08F0CD76-DDCF-4CFA-AE8D-5FB165A62B25@lepiller.eu> X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 14 =?utf-8?Q?Pluvi=C3=B4se?= an 229 de la =?utf-8?Q?R=C3=A9volution?= X-PGP-Key-ID: 0x090B11993D9AEBB5 X-PGP-Key: http://www.fdn.fr/~lcourtes/ludovic.asc X-PGP-Fingerprint: 3CE4 6455 8A84 FDC6 9DB4 0CFB 090B 1199 3D9A EBB5 X-OS: x86_64-pc-linux-gnu Date: Tue, 02 Feb 2021 14:07:44 +0100 In-Reply-To: (Maxime Devos's message of "Mon, 01 Feb 2021 17:19:45 +0100") Message-ID: <87o8h2ehy7.fsf@gnu.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: guix-devel@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: guix-devel@gnu.org Errors-To: guix-devel-bounces+larch=yhetil.org@gnu.org Sender: "Guix-devel" X-Migadu-Flow: FLOW_IN X-Migadu-Spam-Score: -1.36 Authentication-Results: aspmx1.migadu.com; dkim=none; dmarc=pass (policy=none) header.from=gnu.org; spf=pass (aspmx1.migadu.com: domain of guix-devel-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=guix-devel-bounces@gnu.org X-Migadu-Queue-Id: 4F6789402BD X-Spam-Score: -1.36 X-Migadu-Scanner: scn1.migadu.com X-TUID: NvjpcaPCh9tY Hi, Maxime Devos skribis: >> > I=E2=80=99m not sure I understand the threat model. If Knot has a RCE >> > vulnerability, it can be exploited to run anything on behalf of the >> > =E2=80=98knot=E2=80=99 user. >> >=20 >> > At that point, all the state associated with Knot in /var/lib should be >> > considered tainted; new keys should be generated, and so on. >> >=20 >> > Why focus on the permissions on /var/lib/knot? >>=20 >> My understanding is that, in case of an RCE in knot, the attacker can >> replace /var/lib/knot/* with symlinks to arbitrary files in the FS. When >> the activation procedure is run afterwards, the files being linked to >> are chowned to the knot user, and the attacker can access them. > > That's exactly what I had in mind! Though I would like to stress that > =E2=80=98access=E2=80=99 here is both reading and writing. OK, I see. Roughly, this symlink chown story would be a local exploit that the attacker can take advantage of after exploiting the RCE to potentially get root access. =E2=80=98mkdir-p/perms=E2=80=99 could check that the directory is not a sym= link, to begin with. Is this what you had in mind, Maxime? Thanks, Ludo=E2=80=99.