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From: Richard Guy Briggs <rgb@redhat.com>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: Paul Moore <paul@paul-moore.com>,
	containers@lists.linux-foundation.org, linux-api@vger.kernel.org,
	Linux-Audit Mailing List <linux-audit@redhat.com>,
	linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org, netfilter-devel@vger.kernel.org,
	sgrubb@redhat.com, omosnace@redhat.com, dhowells@redhat.com,
	simo@redhat.com, Eric Paris <eparis@parisplace.org>,
	Serge Hallyn <serge@hallyn.com>,
	ebiederm@xmission.com, Dan Walsh <dwalsh@redhat.com>,
	mpatel@redhat.com
Subject: Re: [PATCH ghak90 V7 20/21] audit: add capcontid to set contid outside init_user_ns
Date: Tue, 22 Oct 2019 16:06:32 -0400
Message-ID: <20191022200632.al5ajlaahsvjeuma@madcap2.tricolour.ca> (raw)
In-Reply-To: <20191022121302.GA9397@hmswarspite.think-freely.org>

On 2019-10-22 08:13, Neil Horman wrote:
> On Mon, Oct 21, 2019 at 08:31:37PM -0400, Paul Moore wrote:
> > On Mon, Oct 21, 2019 at 7:58 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > On 2019-10-21 17:43, Paul Moore wrote:
> > > > On Mon, Oct 21, 2019 at 5:38 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > > On 2019-10-21 15:53, Paul Moore wrote:
> > > > > > On Fri, Oct 18, 2019 at 9:39 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > > > > > On 2019-09-18 21:22, Richard Guy Briggs wrote:
> > > > > > > > Provide a mechanism similar to CAP_AUDIT_CONTROL to explicitly give a
> > > > > > > > process in a non-init user namespace the capability to set audit
> > > > > > > > container identifiers.
> > > > > > > >
> > > > > > > > Use audit netlink message types AUDIT_GET_CAPCONTID 1027 and
> > > > > > > > AUDIT_SET_CAPCONTID 1028.  The message format includes the data
> > > > > > > > structure:
> > > > > > > > struct audit_capcontid_status {
> > > > > > > >         pid_t   pid;
> > > > > > > >         u32     enable;
> > > > > > > > };
> > > > > > >
> > > > > > > Paul, can I get a review of the general idea here to see if you're ok
> > > > > > > with this way of effectively extending CAP_AUDIT_CONTROL for the sake of
> > > > > > > setting contid from beyond the init user namespace where capable() can't
> > > > > > > reach and ns_capable() is meaningless for these purposes?
> > > > > >
> > > > > > I think my previous comment about having both the procfs and netlink
> > > > > > interfaces apply here.  I don't see why we need two different APIs at
> > > > > > the start; explain to me why procfs isn't sufficient.  If the argument
> > > > > > is simply the desire to avoid mounting procfs in the container, how
> > > > > > many container orchestrators can function today without a valid /proc?
> > > > >
> > > > > Ok, sorry, I meant to address that question from a previous patch
> > > > > comment at the same time.
> > > > >
> > > > > It was raised by Eric Biederman that the proc filesystem interface for
> > > > > audit had its limitations and he had suggested an audit netlink
> > > > > interface made more sense.
> > > >
> > > > I'm sure you've got it handy, so I'm going to be lazy and ask: archive
> > > > pointer to Eric's comments?  Just a heads-up, I'm really *not* a fan
> > > > of using the netlink interface for this, so unless Eric presents a
> > > > super compelling reason for why we shouldn't use procfs I'm inclined
> > > > to stick with /proc.
> > >
> > > It was actually a video call with Eric and Steve where that was
> > > recommended, so I can't provide you with any first-hand communication
> > > about it.  I'll get more details...
> > 
> > Yeah, that sort of information really needs to be on the list.
> > 
> > > So, with that out of the way, could you please comment on the general
> > > idea of what was intended to be the central idea of this mechanism to be
> > > able to nest containers beyond the initial user namespace (knowing that
> > > a /proc interface is available and the audit netlink interface isn't
> > > necessary for it to work and the latter can be easily removed)?
> > 
> > I'm not entirely clear what you are asking about, are you asking why I
> > care about nesting container orchestrators?  Simply put, it is not
> > uncommon for the LXC/LXD folks to see nested container orchestrators,
> > so I felt it was important to support that use case.  When we
> > originally started this effort we probably should have done a better
> > job reaching out to the LXC/LXD folks, we may have caught this
> > earlier.  Regardless, we caught it, and it looks like we are on our
> > way to supporting it (that's good).
> > 
> > Are you asking why I prefer the procfs approach to setting/getting the
> > audit container ID?  For one, it makes it easier for a LSM to enforce
> > the audit container ID operations independent of the other audit
> > control APIs.  It also provides a simpler interface for container
> > orchestrators.  Both seem like desirable traits as far as I'm
> > concerned.
> 
> I agree that one api is probably the best approach here, but I actually
> think that the netlink interface is the more flexible approach.  Its a
> little more work for userspace (you have to marshal your data into a
> netlink message before sending it, and wait for an async response), but
> thats a well known pattern, and it provides significantly more
> flexibility for the kernel.  LSM already has a hook to audit netlink
> messages in sock_sendmsg, so thats not a problem, and if you use
> netlink, you get the advantage of being able to broadcast messages
> within your network namespaces, facilitating any needed orchestrator
> co-ordination.  To do the same thing with a filesystem api, you need to
> use the fanotify api, which IIRC doesn't work on proc.

One api was the intent, deprecating proc for loginuid and sessionid if
netlink was the chosen way to go.

I don't think we had discussed the possibility or need to use netlink
multicast for this purpose and see it as a liability to limiting access
to only those processes that need it.

> Neil
> 
> > > > > The intent was to switch to the audit netlink interface for contid,
> > > > > capcontid and to add the audit netlink interface for loginuid and
> > > > > sessionid while deprecating the proc interface for loginuid and
> > > > > sessionid.  This was alluded to in the cover letter, but not very clear,
> > > > > I'm afraid.  I have patches to remove the contid and loginuid/sessionid
> > > > > interfaces in another tree which is why I had forgotten to outline that
> > > > > plan more explicitly in the cover letter.
> > 
> > paul moore

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635


  parent reply index

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-19  1:22 [PATCH ghak90 V7 00/21] audit: implement container identifier Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 01/21] audit: collect audit task parameters Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 02/21] audit: add container id Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 03/21] audit: read container ID of a process Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 04/21] audit: convert to contid list to check for orch/engine ownership Richard Guy Briggs
2019-09-26 14:46   ` Neil Horman
2019-10-25 20:00     ` Richard Guy Briggs
2019-10-28 12:20       ` Neil Horman
2019-10-11  0:38   ` Paul Moore
2019-10-25 21:00     ` Richard Guy Briggs
2019-11-08 18:26       ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 05/21] audit: log drop of contid on exit of last task Richard Guy Briggs
2019-10-11  0:38   ` Paul Moore
2019-10-25 19:43     ` Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 06/21] audit: contid limit of 32k imposed to avoid DoS Richard Guy Briggs
2019-09-27 12:51   ` Neil Horman
2019-10-11  0:38     ` Paul Moore
2019-10-24 21:23       ` Richard Guy Briggs
2019-11-08 17:49         ` Paul Moore
2019-10-25 20:15     ` Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 07/21] audit: log container info of syscalls Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 08/21] audit: add contid support for signalling the audit daemon Richard Guy Briggs
2019-10-11  0:39   ` Paul Moore
2019-10-25 19:20     ` Richard Guy Briggs
2019-11-08 17:41       ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 09/21] audit: add support for non-syscall auxiliary records Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 10/21] audit: add containerid support for user records Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 11/21] audit: add containerid filtering Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 12/21] audit: add support for containerid to network namespaces Richard Guy Briggs
2019-10-11  0:39   ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 13/21] audit: NETFILTER_PKT: record each container ID associated with a netNS Richard Guy Briggs
2019-10-11  0:39   ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 14/21] audit: contid check descendancy and nesting Richard Guy Briggs
2019-10-11  0:40   ` Paul Moore
2019-10-24 22:08     ` Richard Guy Briggs
2019-10-30 20:32       ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 15/21] sched: pull task_is_descendant into kernel/sched/core.c Richard Guy Briggs
2019-10-11  0:40   ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 16/21] audit: add support for contid set/get by netlink Richard Guy Briggs
2019-10-11  0:40   ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 17/21] audit: add support for loginuid/sessionid " Richard Guy Briggs
2019-10-11  0:40   ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 18/21] audit: track container nesting Richard Guy Briggs
2019-10-11  0:40   ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 19/21] audit: check cont depth Richard Guy Briggs
2019-09-19  1:22 ` [PATCH ghak90 V7 20/21] audit: add capcontid to set contid outside init_user_ns Richard Guy Briggs
2019-10-19  1:39   ` Richard Guy Briggs
2019-10-21 19:53     ` Paul Moore
2019-10-21 21:38       ` Richard Guy Briggs
2019-10-21 21:43         ` Paul Moore
2019-10-21 23:57           ` Richard Guy Briggs
2019-10-22  0:31             ` Paul Moore
2019-10-22 12:13               ` Neil Horman
2019-10-22 14:04                 ` Paul Moore
2019-10-22 20:06                 ` Richard Guy Briggs [this message]
2019-10-22 14:27               ` Richard Guy Briggs
2019-10-22 14:34                 ` Paul Moore
2019-10-24 21:00               ` Richard Guy Briggs
2019-10-30 20:27                 ` Paul Moore
2019-10-30 22:03                   ` Richard Guy Briggs
2019-10-31 13:59                     ` Paul Moore
2019-10-31 14:50                     ` Steve Grubb
2019-10-31 23:37                       ` Paul Moore
2019-11-01  1:02                       ` Duncan Roe
2019-11-01 15:09                       ` Richard Guy Briggs
2019-11-01 15:13                         ` Steve Grubb
2019-11-01 15:21                           ` Richard Guy Briggs
2019-11-01 16:22                         ` Paul Moore
2019-09-19  1:22 ` [PATCH ghak90 V7 21/21] audit: add proc interface for capcontid Richard Guy Briggs

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