Re: Status of Privacy Extensions for Stateless Address Autoconfiguration in IPv6

[Alexandre Petrescu <[e-mail]>]

Le 02/04/2020 à 14:35, Fernando Gont a écrit :
> On 2/4/20 09:23, Alexandre Petrescu wrote:
>> 
>> 
>> LF/HF
>> 
>> Le 02/04/2020 à 13:36, Fernando Gont a écrit :
>>> Hi, Alexandre,
>>> 
>>> On 2/4/20 07:08, Alexandre Petrescu wrote:
>>>> Hi,
>>>> 
>>>> draft says:
>>>>> This document describes an extension that causes nodes to
>>>>> generate global scope addresses with randomized interface
>>>>> identifiers that change over time.
>>>> 
>>>> It is not sufficient to use randomized IIDs to offer a sense of
>>>>  privacy.
>>>> 
>>>> The network prefix might need to not be fixed either.
>>>> 
>>>> It is not only about changing the IID over time, it is also the
>>>> fact that the length of that IID is likely to be fixed
>>>> forever.
>>>> 
>>>> With these two things at hand: fixed length of IID, and single
>>>>  prefix advertised by the router for SLAAC, an adversary might
>>>> do attacks on privacy, despite the IID changing over time.
>>> 
>>> This was already discussed on the mailing-list, is noted in the
>>> draft,
>> Do you mean this in the draft?
> 
> Yes.
> 
> 
>>> If the network contains a very small number of nodes, say, just
>>> one, changing just the interface identifier will not enhance
>>> privacy, since the prefix serves as a constant identifier.
>> 
>> Would it be possible to specifically say this: "not only the the
>> contents of a prefix is constant, but its length is a constant as
>> well."
>> 
[...]
> Not sure what you mean. At the time of this writing, SLAAC mandates 
> /64s. This document has not say about the prefix length.  Am I
> missing something?

We work on a draft for SLAAC with variable length (not only 64).  You
dont miss anything.  It is an individual proposal.  We have not posted
the draft to IETF because various deadline problems, but it's there on 
github.

The Internet Draft rfc4941bis does say 'length' at several places.

>> Would it be possible to suggest a requirement like this: "It is a
>> requirement that the network accepts a prefix dictated by the UE"

This ^ has nothing to do with SLAAC and 64.  It is about the network 
accepting or refusing that it is the Host who suggests the prefix, not 
the network.

Alex

> 
> 
> Thanks,