Re: [homenet] Kathleen Moriarty's Discuss on draft-ietf-homenet-hncp-09: (with DISCUSS)

Markus Stenberg <markus.stenberg@iki.fi> Fri, 20 November 2015 15:51 UTC

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From: Markus Stenberg <markus.stenberg@iki.fi>
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To: Kathleen Moriarty <kathleen.moriarty.ietf@gmail.com>
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Subject: Re: [homenet] Kathleen Moriarty's Discuss on draft-ietf-homenet-hncp-09: (with DISCUSS)
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> On 20.11.2015, at 17.17, Kathleen Moriarty <kathleen.moriarty.ietf@gmail.com>; wrote:
> 
> Hi Markus,
> 
> Thanks for your quick response, inline,
> 
> On Fri, Nov 20, 2015 at 10:07 AM, Markus Stenberg
> <markus.stenberg@iki.fi>; wrote:
>> On 20.11.2015, at 16.47, Kathleen Moriarty <kathleen.moriarty.ietf@gmail.com>; wrote:
>>>> It is question of threats <-> risks  <-> mitigation analysis. Only thing HNCP security really brings is _in case of insecure L2_ _some_ security for routing/psk state. If we assume every other protocol is secured (e.g. SEND, DHCPv6 ’secure mode’) it may be actually worthwhile, but as long as e.g. DHCPv4 is not secure (and it will never be I suspect), the amount of threats you actually take out of the picture by forcing ’securing’ HNCP alone is not really significant.
>>>> 
>>>> To sum it up: I recommend still SHOULD MTI, MUST MTU _if and only if_ L2, but at least _my_ home does not _have_ any insecure L2, or at least insecure in a sense that HNCP running there would be my greatest worry.
>>> If MTI is not a MUST, how can you MUST the MTU?
>> 
>> The MUST MTU here is only for (relatively small) subset of U cases. Therefore, if a product (or a network) does not see those cases happening, broad MTI/MTU causes extra bloat without any benefit (like my home network case I mentioned).
> Can you propose text that clearly describes this for developers and
> implementors to replace the current text and we'll see where we are
> at?  If it makes enough sense, I may be okay with that.  Stephen also
> supported my discuss, so both of us may need to review and possibly
> tweak it.  The current text isn't clear enough to convey what's been
> described int his thread.

I am not really a wordsmith, and as I am completely happy with the ’security of unicast traffic’ (given the delta in [1]), I am not really sure what is to be done about that. Perhaps Steven can come up with something.

The text currently looks as follows:

12.2.  Security of Unicast Traffic

   Once the homenet border has been established there are several ways
   to secure HNCP against internal threats like manipulation or
   eavesdropping by compromised devices on a link which is enabled for
   HNCP traffic.  If left unsecured, attackers may perform arbitrary
   traffic redirection, eavesdropping, spoofing or denial of service
   attacks on HNCP services such as address assignment or service
   discovery, and the protocols secured using HNCP-derived keys such as
   routing protocols.

   Detailed interface categories like "leaf" or "guest" can be used to
   integrate not fully trusted devices to various degrees into the
   homenet by not exposing them to HNCP traffic or by using firewall
   rules to prevent them from reaching homenet-internal resources.

   On links where this is not practical and lower layers do not provide
   adequate protection from attackers, DTLS-based secure unicast
   transport MUST be used to secure traffic.

Can you and Stephen come up with requirements on what exactly you want in this subsection?

>> Ah, sorry, simply too much mail backlog. ’secure mode’ in that context should be probably just secure _transport_ enabled on that particular link/for a particular remote endpoint, that is,  the {TLS,DTLS} based one described in the rest of the text.
> OK, then for the text where this shows up in this draft, please do
> replace it with what is meant exactly.
>> I wonder if we should edit dncp too, I don’t think that term appears anywhere elsewhere in the document.
> Yes, please.  Since it isn't defined anywhere, just stating what was
> intended would be much better.

Staged [1] for both dncp(-13) and hncp(-10) that removes ‘secure mode’ references. I suspect it is remainder of some much older text where we used the term more :) Good catch, thanks.

Cheers,

-Markus

[1] https://github.com/fingon/ietf-drafts/commit/363bd9b02108b4f05c03eaa68181a0f972de8c6c