Re: [dns-privacy] Direction of draft-mayrhofer-edns0-padding

["Paul Hoffman" <[e-mail]>]

On 29 Jul 2015, at 10:48, Stephen Farrell wrote:

>> Basically, the DNS stack will not know whether or not it is running
>> under TLS/DTLS when the query and reply are formed; TLS/DTLS will be
>> opportunistic. So, to be safe, the DNS client or server will be 
>> forced
>> to add padding even when it is not needed, and thus make every 
>> message
>> longer.
>
> I don't get that. Surely at most 1 query or response will be sent
> when in such a state of ignorance, after which the application layer
> can easily know if a TLS session exists. We are after all still
> talking about stub<->recursive still, right?

We are not defining an API, so there is no way for the application layer 
to know what it is running under.

>
>> We don't know how much padding is required to prevent analysis for
>> particular query/response pairs, and thus need to add lots of
>> random-length padding to each message to prevent the analysis.
>
> I also don't get that. I agree we're not sure how to best use
> padding. But we can define the simple bit of protocol needed now
> and then after folks figure out how best to use it we could have
> some more recommendations to make. And those might end up being
> context dependent. So I see no need to mandate something wasteful
> now.

That would be fine. What I worry about is that people will say "we can 
pad; people tell us to pad liberally; we will pad liberally". It would 
be great for the spec to say "probably don't do this much until more 
research has been done".

--Paul Hoffman