linux-kernel - Re: [PATCH 00/12] Add kdbus implementation

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Date:	Wed, 29 Oct 2014 15:36:44 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Linux API <linux-api@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
	Marcel Holtmann <marcel@...tmann.org>,
	Ryan Lortie <desrt@...rt.ca>,
	Bastien Nocera <hadess@...ess.net>,
	David Herrmann <dh.herrmann@...il.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	simon.mcvittie@...labora.co.uk, daniel@...que.org,
	alban.crequy@...labora.co.uk, javier.martinez@...labora.co.uk,
	Tom Gundersen <teg@...m.no>
Subject: Re: [PATCH 00/12] Add kdbus implementation

On Wed, Oct 29, 2014 at 3:28 PM, Andy Lutomirski <luto@...capital.net> wrote:
> On Wed, Oct 29, 2014 at 3:25 PM, Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
>> On Wed, Oct 29, 2014 at 03:19:21PM -0700, Andy Lutomirski wrote:
>>> On Wed, Oct 29, 2014 at 3:00 PM, Greg Kroah-Hartman
>>> <gregkh@...uxfoundation.org> wrote:
>>> >  * Attachment of trustable metadata to each message on demand, such as
>>> >    the sending peer's timestamp, creds, auxgroups, comm, exe, cmdline,
>>> >    cgroup path, capabilities, security label, audit information, etc,
>>> >    each taken at the time the sender issued the ioctl to send the
>>> >    message. Which of those are actually recorded and attached is
>>> >    controlled by the receiving peer.
>>>
>>> I think that each piece of trustable metadata needs to be explicitly
>>> opted-in to by the sender at the time of capture.  Otherwise you're
>>> asking for lots of information leaks and privilege escalations.  This
>>> is especially important given that some of the items in the current
>>> list could be rather sensitive.
>>
>> You do have to opt-in for this information at time of capture, so I
>> don't understand the issue here.  This is the same type of thing that
>> dbus does today, and I don't see the information leaks happening there,
>> do you?
>>
>
> The docs suggest that the *receiver* opts in.
>

So does the code:

+ /*
+ * The first receiver which requests additional
+ * metadata causes the message to carry it; all
+ * receivers after that will see all of the added
+ * data, even when they did not ask for it.
+ */
+ if (conn_src) {
+ /* Check if conn_src is allowed to signal */
+ ret = kdbus_ep_policy_check_broadcast(conn_dst->ep,
+ conn_src,
+ conn_dst);
+ if (ret < 0)
+ continue;
+
+ ret = kdbus_ep_policy_check_src_names(conn_dst->ep,
+ conn_src,
+ conn_dst);
+ if (ret < 0)
+ continue;
+
+ ret = kdbus_kmsg_attach_metadata(kmsg, conn_src,
+ conn_dst);
+ if (ret < 0)
+ goto exit_unlock;
+ }
+

I'd like this if the sender chose the metadata flags.  In fact, I'd
want to make that feature available on regular UNIX sockets, too
(search the archives for SCM_IDENTITY).

--Andy
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