Re: [Homenet-babel-sec] [babel] What's up with HNCP security?

Juliusz Chroboczek <jch@irif.fr> Mon, 29 May 2017 01:19 UTC

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Date: Mon, 29 May 2017 03:19:12 +0200
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From: Juliusz Chroboczek <jch@irif.fr>
To: Ted Lemon <mellon@fugue.com>
Cc: Markus Stenberg <markus.stenberg@iki.fi>, homenet-babel-sec@ietf.org, babel@ietf.org
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Subject: Re: [Homenet-babel-sec] [babel] What's up with HNCP security?
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> The idea is to have key pairs, not network wide keys

If it can be done without too much complexity, sure.

> (this is why Juiliusz needs unicast hellos in Babel).

I was under the (perhaps mistaken) impression that asymmetric signing can
be done just as well over multicast.  The reasons people want unicast
hellos are multiple:

  - leverage DTLS (Stenberg-style) or IKE (Schinazi-style);
  - run Babel over NBMA (Cullen-style);
  - avoid multicast noise (Taht-Høiland-style).

Even for Stenberg-Schinazi security, it's not obvious to me why we need
unicast Hellos -- it's only Updates that really need to be protected, if
an attacker manages to fake a Hello he'll only be able to disrupt the
link-quality estimation algorithm (which is only a DoS vector).

And Margaret is doing NBMA in RFC 6126 just fine, by sending unicast
Hellos simultaneously to all neighbours and hence avoiding seqno
desyncrhonisation.

In short -- if we don't get unicast Hellos into 6126bis, I'll be happy
enough.  If we do, and they're done well, I'll be happier.

> Network wide keys are useless.

Depends on the size of the network, I guess.

-- Juliusz