From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp0 ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by ms11 with LMTPS id 0MNiIiQgGGCxDAAA0tVLHw (envelope-from ) for ; Mon, 01 Feb 2021 15:37:08 +0000 Received: from aspmx1.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp0 with LMTPS id 6PvzHSQgGGCwUAAA1q6Kng (envelope-from ) for ; Mon, 01 Feb 2021 15:37:08 +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 24D9E9402C2 for ; Mon, 1 Feb 2021 15:37:08 +0000 (UTC) Received: from localhost ([::1]:46618 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l6bGF-00063H-3s for larch@yhetil.org; Mon, 01 Feb 2021 10:37:07 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:39718) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l6bFB-0005Q4-Ce for guix-devel@gnu.org; Mon, 01 Feb 2021 10:36:04 -0500 Received: from fencepost.gnu.org ([2001:470:142:3::e]:54207) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l6bF9-0001bp-Rt; Mon, 01 Feb 2021 10:35:59 -0500 Received: from [2a01:e0a:1d:7270:af76:b9b:ca24:c465] (port=56252 helo=ribbon) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1l6bF8-0007bv-1J; Mon, 01 Feb 2021 10:35:59 -0500 From: =?utf-8?Q?Ludovic_Court=C3=A8s?= To: Leo Famulari , Maxime Devos Subject: Re: Potential security weakness in Guix services References: X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 13 =?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: Mon, 01 Feb 2021 16:35:56 +0100 In-Reply-To: (Leo Famulari's message of "Thu, 28 Jan 2021 16:53:49 -0500") Message-ID: <87k0rrls0z.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: -2.86 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: 24D9E9402C2 X-Spam-Score: -2.86 X-Migadu-Scanner: scn0.migadu.com X-TUID: fewYntnnlInJ Hi, Leo Famulari skribis: > For clarification: the scenario I currently have in mind, is that noone > has intentionally introduced a security hole in a service, but rather > there's an accidental security bug somewhere in service package, that > allows an attacker (I'm assuming the service is accessible from the > network) arbitrary code execution *within* the service's process. > > As it is now, the attacker could overtake the service process, then chown > and chmod arbitrary directories from there. As a particular example, I'm > considering e.g. a hypothetical ipfs-service-type. A compromised IPFS pro= cess > shouldn't be able to change /etc/passwd entries. The security of the IPFS > service itself shouldn't be critical to the security of the system as a > whole. > ----- > > A more specific exapmle: > > ----- Forwarded message from Maxime Devos ----- > I seem to have stumbled upon a potential security issue, it has to > do with how some services use mkdir-p/perms. For example, in knot-activat= ion: > > (define (knot-activation config) > #~(begin > (use-modules (guix build utils)) > (mkdir-p/perms #$(knot-configuration-run-directory config) > (getpwnam "knot") #o755) > (mkdir-p/perms "/var/lib/knot" (getpwnam "knot") #o755) > (mkdir-p/perms "/var/lib/knot/keys" (getpwnam "knot") #o755) > (mkdir-p/perms "/var/lib/knot/keys/keys" (getpwnam "knot") #o755= ))) > > /var/lib/knot/keys/keys is chmodded and chowned, which seems innocent eno= ugh. > However, what if knot whas compromised at some point, and the compromised= knot > process has replaced /var/lib/knot/keys with, say, a symlink to /gnu/stor= e? 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. At that point, all the state associated with Knot in /var/lib should be considered tainted; new keys should be generated, and so on. Why focus on the permissions on /var/lib/knot? Also, every time it=E2=80=99s possible and not redundant with measures alre= ady implemented by the daemon itself, we should consider using =E2=80=98make-forkexec-constructor/container=E2=80=99 as a further mitigati= on. WDYT? Ludo=E2=80=99.