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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97E20C46470 for ; Thu, 30 May 2019 17:09:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7123B25DF1 for ; Thu, 30 May 2019 17:09:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727485AbfE3RJR (ORCPT ); Thu, 30 May 2019 13:09:17 -0400 Received: from mail.hallyn.com ([178.63.66.53]:50574 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725961AbfE3RJR (ORCPT ); Thu, 30 May 2019 13:09:17 -0400 Received: by mail.hallyn.com (Postfix, from userid 1001) id 3568262D; Thu, 30 May 2019 12:09:13 -0500 (CDT) Date: Thu, 30 May 2019 12:09:13 -0500 From: "Serge E. Hallyn" To: Paul Moore Cc: Tycho Andersen , Richard Guy Briggs , containers@lists.linux-foundation.org, linux-api@vger.kernel.org, Linux-Audit Mailing List , linux-fsdevel@vger.kernel.org, LKML , netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, sgrubb@redhat.com, omosnace@redhat.com, dhowells@redhat.com, simo@redhat.com, Eric Paris , Serge Hallyn , ebiederm@xmission.com, nhorman@tuxdriver.com Subject: Re: [PATCH ghak90 V6 02/10] audit: add container id Message-ID: <20190530170913.GA16722@mail.hallyn.com> References: <9edad39c40671fb53f28d76862304cc2647029c6.1554732921.git.rgb@redhat.com> <20190529145742.GA8959@cisco> <20190529153427.GB8959@cisco> <20190529222835.GD8959@cisco> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Wed, May 29, 2019 at 06:39:48PM -0400, Paul Moore wrote: > On Wed, May 29, 2019 at 6:28 PM Tycho Andersen wrote: > > On Wed, May 29, 2019 at 12:03:58PM -0400, Paul Moore wrote: > > > On Wed, May 29, 2019 at 11:34 AM Tycho Andersen wrote: > > > > > > > > On Wed, May 29, 2019 at 11:29:05AM -0400, Paul Moore wrote: > > > > > On Wed, May 29, 2019 at 10:57 AM Tycho Andersen wrote: > > > > > > > > > > > > On Mon, Apr 08, 2019 at 11:39:09PM -0400, Richard Guy Briggs wrote: > > > > > > > It is not permitted to unset the audit container identifier. > > > > > > > A child inherits its parent's audit container identifier. > > > > > > > > > > > > ... > > > > > > > > > > > > > /** > > > > > > > + * audit_set_contid - set current task's audit contid > > > > > > > + * @contid: contid value > > > > > > > + * > > > > > > > + * Returns 0 on success, -EPERM on permission failure. > > > > > > > + * > > > > > > > + * Called (set) from fs/proc/base.c::proc_contid_write(). > > > > > > > + */ > > > > > > > +int audit_set_contid(struct task_struct *task, u64 contid) > > > > > > > +{ > > > > > > > + u64 oldcontid; > > > > > > > + int rc = 0; > > > > > > > + struct audit_buffer *ab; > > > > > > > + uid_t uid; > > > > > > > + struct tty_struct *tty; > > > > > > > + char comm[sizeof(current->comm)]; > > > > > > > + > > > > > > > + task_lock(task); > > > > > > > + /* Can't set if audit disabled */ > > > > > > > + if (!task->audit) { > > > > > > > + task_unlock(task); > > > > > > > + return -ENOPROTOOPT; > > > > > > > + } > > > > > > > + oldcontid = audit_get_contid(task); > > > > > > > + read_lock(&tasklist_lock); > > > > > > > + /* Don't allow the audit containerid to be unset */ > > > > > > > + if (!audit_contid_valid(contid)) > > > > > > > + rc = -EINVAL; > > > > > > > + /* if we don't have caps, reject */ > > > > > > > + else if (!capable(CAP_AUDIT_CONTROL)) > > > > > > > + rc = -EPERM; > > > > > > > + /* if task has children or is not single-threaded, deny */ > > > > > > > + else if (!list_empty(&task->children)) > > > > > > > + rc = -EBUSY; > > > > > > > + else if (!(thread_group_leader(task) && thread_group_empty(task))) > > > > > > > + rc = -EALREADY; > > > > > > > + read_unlock(&tasklist_lock); > > > > > > > + if (!rc) > > > > > > > + task->audit->contid = contid; > > > > > > > + task_unlock(task); > > > > > > > + > > > > > > > + if (!audit_enabled) > > > > > > > + return rc; > > > > > > > > > > > > ...but it is allowed to change it (assuming > > > > > > capable(CAP_AUDIT_CONTROL), of course)? Seems like this might be more > > > > > > immediately useful since we still live in the world of majority > > > > > > privileged containers if we didn't allow changing it, in addition to > > > > > > un-setting it. > > > > > > > > > > The idea is that only container orchestrators should be able to > > > > > set/modify the audit container ID, and since setting the audit > > > > > container ID can have a significant effect on the records captured > > > > > (and their routing to multiple daemons when we get there) modifying > > > > > the audit container ID is akin to modifying the audit configuration > > > > > which is why it is gated by CAP_AUDIT_CONTROL. The current thinking > > > > > is that you would only change the audit container ID from one > > > > > set/inherited value to another if you were nesting containers, in > > > > > which case the nested container orchestrator would need to be granted > > > > > CAP_AUDIT_CONTROL (which everyone to date seems to agree is a workable > > > > > compromise). > > > > > > > > But then don't you want some kind of ns_capable() instead (probably > > > > not the obvious one, though...)? With capable(), you can't really nest > > > > using the audit-id and user namespaces together. > > > > > > You want capable() and not ns_capable() because you want to ensure > > > that the orchestrator has the rights in the init_ns as changes to the > > > audit container ID could have an auditing impact that spans the entire > > > system. > > > > Ok but, > > > > > > > The current thinking > > > > > is that you would only change the audit container ID from one > > > > > set/inherited value to another if you were nesting containers, in > > > > > which case the nested container orchestrator would need to be granted > > > > > CAP_AUDIT_CONTROL (which everyone to date seems to agree is a workable > > > > > compromise). > > > > won't work in user namespaced containers, because they will never be > > capable(CAP_AUDIT_CONTROL); so I don't think this will work for > > nesting as is. But maybe nobody cares :) > > That's fun :) > > To be honest, I've never been a big fan of supporting nested > containers from an audit perspective, so I'm not really too upset > about this. The k8s/cri-o folks seem okay with this, or at least I > haven't heard any objections; lxc folks, what do you have to say? I actually thought the answer to this (when last I looked, "some time" ago) was that userspace should track an audit message saying "task X in container Y is changing its auditid to Z", and then decide to also track Z. This should be doable, but a lot of extra work in userspace. Per-userns containerids would also work. So task X1 is in containerid 1 on the host and creates a new task Y in new userns; it continues to be reported in init_user_ns as containerid 1 forever; but in its own userns it can request to be known as some other containerid. Audit socks would be per-userns, allowing root in a container to watch for audit events in its own (and descendent) namespaces. But again I'm sure we've gone over all this in the last few years. I suppose we can look at this as a "first step", and talk about making it user-ns-nestable later. But agreed it's not useful in a lot of situations as is. -serge