Re: [Int-area] [ietf-privacy] NAT Reveal / Host Identifiers

[Stephen Farrell <[e-mail]>]

Hiya,

On 11/06/14 15:38, [e-mail] wrote:
> Re-,
> 
> Please see inline.
> 
> Cheers, Med
> 
>> -----Message d'origine----- De : ietf-privacy
>> [mailto:[e-mail]] De la part de Stephen
>> Farrell Envoyé : samedi 7 juin 2014 15:21 À : Dan Wing Cc :
>> [e-mail]; Internet Area; Joe Touch Objet : Re:
>> [ietf-privacy] [Int-area] NAT Reveal / Host Identifiers
>> 
>> 
>> Hi Dan,
>> 
>> On 07/06/14 02:38, Dan Wing wrote:
>>> 
>>> Stephen,
>>> 
>>> It seems NAPT has become IETF's privacy feature of 2014 because 
>>> multiple users are sharing one identifier (IP address and
>>> presumably randomized ports [RFC6056], although many NAPT
>>> deployments use address ranges because of fear of compressing log
>>> files).  As a former co-chair of BEHAVE it is refreshing to see
>>> the IETF embracing NAPT as a desirable feature.
>> 
>> Embracing seems like significant overstatement to me, but maybe 
>> that's understandable given how calmly NAT is generally debated.
>> 
>> NATs have both good and bad properties. The slightly better
>> privacy is one of the good ones.
>> 
>> Recognising that reality is neither embracing nor refreshing IMO, 
>> nor does it mean NAPT is (un)desirable overall. (That's an
>> argument I only ever watch from the side-lines thanks:-)
>> 
>>> However, if NAPT provides privacy and NAT Reveal removes it,
>>> where does that leave a host's IPv6 source address with respect
>>> to BCP188?
>>> 
>>> Afterall, an IPv6 address is quite traceable, even with IPv6
>>> privacy addresses (especially as IPv6 privacy addresses are
>>> currently deployed which only obtain a new IPv6 privacy address
>>> every 24 hours or when attaching to a new network).  If BCP188
>>> does not prevent deployment of IPv6, I would like to understand
>>> the additional privacy leakage of IPv4+NAT+NAT_Reveal compared to
>>> the privacy leakage of IPv6+privacy_address.
>> 
>> I'm frankly amazed that that's not crystal clear to anyone who has
>> read all 2.5 non-boilerplate pages of the BCP. Or even just the
>> last two words of the 1-line abstract (hint: those say "where 
>> possible.")
>> 
>> Yes, source addresses leak information that affects privacy. But we
>> do not have a practical way to mitigate that. So therefore BCP188
>> does not call for doing stupid stuff, nor for new laws of physics
>> (unlike -04 of the draft we're discussing;-)
> 
> [Med] FWIW, this draft does not hint solutions but it aims to
> describe scenarios with problems. I understand you have concerns with
> privacy but this is not an excuse to abuse and characterize this
> effort as "stupid". 

Apologies if you took it that way. What I meant was that BCP188
does not call for stupid stuff, I was not characterising the
draft as stupid, but rather the assertion that BCP188 calls for
such.

> Privacy implications should be assess on a per
> use case basis 

Where do I find the per-use-case analysis of privacy implications?

> (see for example cases where all involved entities
> belong to same administrative entity). Furthermore, the document
> (including -04) says the following : "the document does not elaborate
> whether explicit authentication is enabled or not."
> 
>> 
>> Adding new identifiers with privacy impact, as proposed here, is 
>> quite different.
> 
> [Med] I have already clarified this point: the scenario draft does
> not propose any identifier!

I think its unrealistic to assert that any solution is possible
without such. I would be interested in reading about any proposal
that did not require a new identifier. So yes, I do assert that a
need for a new identifier is implicit in the draft, even if that
is not stated explicitly, and would be interested in arguments as
to why I'm wrong about that.

S.

> 
>> 
>> S.
>> 
>> PS: If someone wants to propose what they think is a practical way
>> to mitigate the privacy issues with source addresses, please write
>> a draft first and then start a separate thread somewhere.
>> 
>> 
>>> 
>>> -d
>>> 
>> 
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> 
>