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Re: [Add] [EXTERNAL] Re: draft-grover-add-policy-detection-00

Eric Rescorla <ekr@rtfm.com> Wed, 17 July 2019 17:24 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 17 Jul 2019 10:24:11 -0700
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To: tirumal reddy <kondtir@gmail.com>
Cc: Rob Sayre <sayrer@gmail.com>, ADD Mailing list <add@ietf.org>, "Dixon, Hugh" <Hugh.Dixon@sky.uk>, Alec Muffett <alec.muffett@gmail.com>
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Subject: Re: [Add] [EXTERNAL] Re: draft-grover-add-policy-detection-00
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On Wed, Jul 17, 2019 at 7:05 AM tirumal reddy <kondtir@gmail.com> wrote:

>
> On Wed, 17 Jul 2019 at 01:41, Eric Rescorla <ekr@rtfm.com> wrote:
>
>>
>>
>> On Tue, Jul 16, 2019 at 1:02 PM Rob Sayre <sayrer@gmail.com> wrote:
>>
>>>
>>>
>>> On Tue, Jul 16, 2019 at 12:53 PM Eric Rescorla <ekr@rtfm.com> wrote:
>>>
>>>>
>>>> Taking a TRR-style system out of the equation for a moment. Suppose
>>>> that what I want is for all devices on my network to use a filtering
>>>> resolver. I don't expect any evasion because they're all my devices, it's
>>>> just a matter of convenience to centrally configure it. So what I do here
>>>> is I configure my DHCP server to provide the IP address of that resolver.
>>>> Now, those devices do unencrypted DNS because that's what everyone does.
>>>> Now, suppose that resolver starts offering DoT. How do my devices learn
>>>> that information? The resolver could tell them over DNS but then we have a
>>>> straightforward downgrade attack from anyone on the network. Do you agree
>>>> with this so far? Do you have a proposed solution?
>>>>
>>>
>>> In fairness, I'm not sure I quite follow. But, if I worked at a browser
>>> vendor, I would be worried about DoH rollout too. I think I'd gradually
>>> ratchet up the security signals in the location bar with the end result of
>>> marking sites insecure if their IP was fetched over DNS in the clear.
>>>
>>
>> Ignoring the UI question, let me push a bit on "in the clear".
>>
>> Currently, resolvers are configured by IP address, not domain name. So
>> absent mechanisms such as TRR, how does the DNS client form a secure
>> connection to the resolver? What domain name is in the certificate and how
>> does the client learn that domain name?
>>
>
> https://tools.ietf.org/html/draft-reddy-dprive-bootstrap-dns-server-04 discusses
> mechanism to automatically bootstrap endpoints to discover and authenticate
> DoT/DoH servers provided by a local network. The client securely learns the
> domain name and DNS server certificate.
>

This draft does not seem like it has the general applicability that would
be required in the scenarios that browsers often face.

-Ekr



> Cheers,
> -Tiru
>
>
>>
>> -Ekr
>>
>>
>>
>>
>>> This is distinct from choosing a DNS vendor.
>>>
>>> thanks,
>>> Rob
>>>
>>>
>>>
>>> --
>> Add mailing list
>> Add@ietf.org
>> https://www.ietf.org/mailman/listinfo/add
>>
>

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