rfc4941bis: temporary addresses as "outgoing-only"?

Fernando Gont <fgont@si6networks.com> Mon, 10 February 2020 09:35 UTC

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To: "6man@ietf.org" <6man@ietf.org>
From: Fernando Gont <fgont@si6networks.com>
Subject: rfc4941bis: temporary addresses as "outgoing-only"?
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Date: Mon, 10 Feb 2020 06:33:19 -0300
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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).

The caveats here are:

1) If a host does temporary-only, these are the only addrs you have, and
hence they should allow incomming connections

2) It could be easily done for connection-oriented protocols such as
TCP, but not so easily (if at all possible) for e.g. connectionless
protocols.


As noted in
https://tools.ietf.org/html/draft-gont-6man-address-usage-recommendations-04#section-4.3
, *in theory* there are other ways in which the same effect could be
achieved... so one could certainly argue that this policy should not be
enforced on the addresses, but rather we should have a more appropriate
API that could allow apps to e.g. bind() subsets of all the available
addresses.

Thoughts?

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492