Subject: [babel] Comments about rfc7298bis

From: Juliusz Chroboczek <[email-masked]>
Date: Fri, 30 Mar 2018 21:37:32 +0200

Dear all,

The following is a summary of discussions that I've had with David
Schinazi, Clara Dô, and Weronika Kołodziejak.  I'm no longer sure who made
which comment, so I'll just summarise the discussion.

1. We still don't have a clear and concise description of the attack
against 7298.  That would be helpful, especially if we are meant to work
together.

2. The procedure that consists in putting the source IP into the HMAC
field before hashing is bizarre.  A more straightforward solution would be
to prepend the source IP to the whole Babel packet, similarly to the TCP
pseudo-header.  Note that this does not break the ability to have multiple
HMACs.

3. I think it is necessary to protect the destination IP in addition to
the source IP.  This prevents some pretty obvious attacks against IHU, Ack
and Unicast Hello TLVs, and might in the future prevent attacks against
extensions.

4. For clarity, the TC/PC sub-TLV should be renamed to TC/PC Echo.

5. It's not clear to me what happens when a diskless clock-less node
reboots and loses its sequence number.  I'm sure it's described somewhere
in the document, please point me at the right place.

6. I'm not sure that the IHU TLV is the right place to put the TC/PC
echo -- what about putting it in a sub-TLV of TC/PC itself?

7. What's the fragmentation procedure when the whole set of TC/PC echos
exceeds the size of a packet?

-- Juliusz