[trill] TRILL IPsec encapsulation
Yaron Sheffer <firstname.lastname@example.org> Wed, 22 July 2015 17:48 UTC
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Date: Wed, 22 Jul 2015 19:48:34 +0200
From: Yaron Sheffer <email@example.com>
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Cc: firstname.lastname@example.org, Stephen Farrell <email@example.com>
Subject: [trill] TRILL IPsec encapsulation
List-Id: "Developing a hybrid router/bridge." <trill.ietf.org>
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So here are some comments:
- The draft currently uses IPsec but not IKE or any kind of key management. The end result is that data is being encrypted by very long-lived keys, not enjoying the benefit of forward secrecy etc. Please use IKEv2 and do NOT use IPsec directly. RFC 4107 explains why.
- There is in fact IPsec-with-multicast, but it's not widely deployed and is based on the obsolete IKEv1. Instead, I suggest to use unicast encapsulation with IKEv2. I suppose this means that you'd want to only encapsulate data but not IS-IS frames.
- The draft currently derives encryption keys from IS-IS keys. This is problematic at several levels:
* The IS-IS key is common to a large group of devices (a.k.a. "a group key") and so is likely to be compromised.
* The key is used directly for encryption, as noted.
* The key is derived using HMAC, which is specified incorrectly in the draft (one parameter instead of two).
* The derived key is identical for all routers/links.
- I would suggest to use a derived key for authentication only, and to derive it differently for each link - although I realize that this does not raise the security level significantly. Something like: link-psk = HMAC(IS-IS-key, 6-byte-system-id-1 | 6-byte-system-id-2).
- Note that IKE generates a different encryption key for each link even if everybody is using the same authentication key (pre-shared secret). But it's still a bad practice for all principals to have the same key...
- Longer term it would improve security hugely if each router had an authenticated identity of its own. In other words, its own certificate and private key.
- Please don't define your own MTI algorithms. Just use RFC 7321.