Re: rfc4941bis: temporary addresses as "outgoing-only"?

[David Farmer <[e-mail]>]

On Mon, Feb 10, 2020 at 11:38 PM Fernando Gont <[e-mail]>
wrote:

> On 11/2/20 02:18, Mark Smith wrote:
> > On Tue, 11 Feb 2020 at 15:32, Fernando Gont <[e-mail]>
> wrote:
> >>
> >> On 10/2/20 19:17, Brian E Carpenter wrote:
> >>> On 11-Feb-20 09:46, Mark Smith wrote:
> >>>>
> >>>>
> >>>> On Tue, 11 Feb 2020, 03:13 Fernando Gont, <[e-mail]
> <mailto:[e-mail]>> wrote:
> >>>>
> >>>>       Folks,
> >>>>
> >>>>       Since we are at it, I wonder if rfc4941bis should say anything
> about the
> >>>>       use of temporary addresses for incoming connections. (see
> >>>>
> https://tools.ietf.org/html/draft-gont-6man-address-usage-recommendations-04#section-4.3
> ).
> >>>>       (e.g., "an implementation MAY....")
> >>>>
> >>>>       Particularly for connection-oriented protocols, hosts that
> prevent
> >>>>       incoming connections on temporary addresses reduce exposure
> even when
> >>>>       their temporary addresses become "exposed" by outgoing sessions.
> >>>>
> >>>>       i.e., if the model is that temporary addresses are employed for
> outgoing
> >>>>       connections, unless a host uses temporary-only, there's no
> reason to
> >>>>       receive incoming connections on temporary addresses. (e.g.,
> browsing the
> >>>>       web or sending email should not be an invitation for folks to
> e.g.
> >>>>       port-scan you).
> >>>>
> >>>>
> >>>> This would prevent peer-to-peer connections between end-user devices,
> as it means devices become clients only, and they therefore cannot provide
> a temporary server/service.
> >>>
> >>> If a node has a stable address as well as a temporary address, that
> isn't the case.
> >>
> >> That's what I had in mind.
> >>
> >
> > So if we want to support adhoc peer-to-peer file transfers between
> > e.g. smartphones via NFC/Bluetooth/Adhoc Wifi, then stable addresses
> > are required, even if the file transfer takes say 30 seconds, well
> > within the valid lifetime of the RFC4291bis temporary addresses?
>
> I see your point. And if one were to implement this policy, yes, stable
> addresses would be required.
>
> That said, it is clear to me that this is out of scope for this document
> (I just wanted to check with the group). Once again, if we had
> appropriate APIs, applying this sort of policy host-wide wouldn't even
> make sense.
>

I think a specific requirement to use temporary addresses for outbound only
is out of scope for this document, if only because it permits the use
only temporary addresses by a node, and doesn't require permanent or stable
addresses. Nevertheless, it is an important point, that how temporary
addresses are used by applications impacts their traceability significantly.

Therefore, I think a recommendation like, temporary addresses are generally
most effective when applications prefer temporary addresses for outbound
connections and use other addresses for inbound connections when feasible,
especially for long-term well-known services, is in scope.

Thanks.




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