Re: [tor-dev] Support for full DNS resolution and DNSSEC validation

[nusenu <nusenu-lists@xxxxxxxxxx>]

Christian Hofer:
> On Sat, 2020-05-16 at 01:37 +0200, nusenu wrote:
>> Alexander Færøy:
>>> I wonder if it would make more sense to have an onion-aware
>>> DNSSEC-enabled resolver *outside* of the Tor binary and have a way
>>> for
>>> Tor to query an external tool for DNS lookups. 
>>
>> I'm also in favor of this approach,
>> and you can do this today with no code changes to tor at all.
>>
>> CF demonstrated it even before DoH/RFC8484 was finalized:
>> https://blog.cloudflare.com/welcome-hidden-resolver/
>>
> 
> Do you have DNSSEC validation in this approach? 

That is up to you. If you use a stub resolver that has DNSSEC support (like 
stubby) you have DNSSEC validation.


>> + 1 for DoT and DoH over tor, especially due to the DoH
>> implementation that is
>> available in firefox (it would still require work on stream isolation
>> and caching
>> risks to ensure the usual first party isolation).
>> In terms of achieving a big improvement on tor browser users in the
>> context of DNS
>> this would be the most effective path to spend coding resources on in
>> my opinion.
>>
>>
> 
> It seems that Firefox's DoH implementation does not employ DNSSEC
> validation, see [2]. They trust CF doing it for them. Be careful here.

I'm aware that firefox does not perform DNSSEC validation. I don't think
the tor project would enable DNSSEC in Tor Browser without a good use-case or a (future) TLS extensions solving
the latency issue. Since DANE for HTTPS does not appear to be a thing and there is no DANE support in firefox
I'm also wondering about the specific use-cases for DNSSEC in Tor Browser.

> Furthermore, there are privacy concerns about additional metadata
> regarding the use of DoH (agent headers,

solved since https://bugzilla.mozilla.org/show_bug.cgi?id=1543201

> language settings, 

solved since https://bugzilla.mozilla.org/show_bug.cgi?id=1544724

> and cookies) 

I don't think firefox sends cookies in DoH requests.


I'm still curious about the underlying threat model and use-cases (my first questions in this thread), 
since that would help with trying to understand what you are trying to achieve.

kind regards,
nusenu

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