Subject: Re: [dns-privacy] I-D Action: draft-ietf-dprive-dnsoquic-07.txt

From: Sara Dickinson <[email-masked]>
Date: Tue, 4 Jan 2022 16:59:43 +0000

> On 9 Dec 2021, at 09:25, Alexander Mayrhofer <[email-masked]> wrote:
> 
> Sara, Allison, Christian,
> 
> I read through the latest revision of DoQ, and i'm afraid i do have a
> comment regarding the padding section. More specifically, i think the
> second "option" of section 6.4 should refer to the base specification
> of EDNS0-Padding, rather than the Padding policies RFC. It currently
> reads as:
> 
>   *  if padding at the QUIC level is not available or not used, DNS
>      over QUIC MUST ensure that all DNS queries and responses are
>      padded to a small set of fixed sizes, using the EDNS padding
>      extension as specified in "Padding Policies for Extension
>      Mechanisms for DNS (EDNS(0))" [RFC8467].
> 
> And i do believe that - as the sentence stands - the reference should
> be RFC 7830. Note that RFC 8467 is Experimental (and was by intent, as
> the privacy properties of Padding would probably shift with more
> operational expertise). So, i feel REQUIRING that padding is used
> makes more sense than REQUIRING the use of the experimental padding
> sizes in RFC8467.
> 
> I think the sentence should read "padded to a small set of fixed
> sizes, using the EDNS Padding Extension as specified in [RFC7830]."
> 
> I like the "aligned with..." text in the previous bullet point, which
> could also be used here, indicating that the MUST is for the the
> padding, and not necessarily for that revision of the padding policy.

Hi Alex, 

Sorry for slow response and many thanks for spotting this mistake. I agree that the second bullet should reference RFC7830 and so propose the following update:

   *  if padding at the QUIC level is not available or not used, DNS
      over QUIC MUST ensure that all DNS queries and responses are
      padded to a small set of fixed sizes, using the EDNS padding
      extension as specified in [RFC7830].  The sizes SHOULD be aligned
      with the recommendations of the "Padding Policies for Extension
      Mechanisms for DNS (EDNS(0))" [RFC8467].

Re-reading the whole section, I also noticed an inconsistency. The first sentence is only a SHOULD at the moment:

“ Implementations SHOULD protect against the traffic analysis attacks
   described in Section 9.5 by the judicious injection of padding. “

but given the second bullet is a MUST, I think this is also actually a MUST. 

I’ve created a PR with both these changes for review:
https://github.com/huitema/dnsoquic/pull/132

Regards

Sara.