Re: [PATCH 00/12] Add kdbus implementation

[Andy Lutomirski <luto@amacapital.net>]

On Wed, Oct 29, 2014 at 3:28 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Wed, Oct 29, 2014 at 3:25 PM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.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@linuxfoundation.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