Re: [Doh] [Ext] Fallback to untrusted DOH servers

Mateusz Jończyk <mat.jonczyk@o2.pl> Sun, 15 April 2018 18:39 UTC

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To: Paul Hoffman <paul.hoffman@icann.org>, doh@ietf.org
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From: Mateusz Jończyk <mat.jonczyk@o2.pl>
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Date: Sun, 15 Apr 2018 19:39:11 +0200
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Subject: Re: [Doh] [Ext] Fallback to untrusted DOH servers
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W dniu 14.04.2018 o 22:54, Paul Hoffman pisze:
> On Apr 14, 2018, at 9:36 AM, Mateusz Jończyk <mat.jonczyk@o2.pl> wrote:
>>
>> Hello,
>> Current DOH draft specifies that:
>>
>>   A client MUST
>>   NOT trust a DNS API server simply because it was discovered, or
>>   because the client was told to trust the DNS API server by an
>>   untrusted party.  Instead, a client MUST only trust DNS API server
>>   that is configured as trustworthy.
>>
>> It may happen that either no trustworthy DOH server has been configured, or the
>> configured DOH server is not working. In such cases a DOH client would usually
>> revert to using an untrusted DNS server on port 53, possibly one that was
>> discovered through unsecure DHCP. This DNS resolver would also be able to poison
>> DNS caches then.
> 
> The topic of how a user (well, really, an OS or browser) choose a DNS server to use is a worthy one to look at, but not in this document. If someone wants to start such a document, it needs to deal with trust in DHCP, DHCP MITMs, DNS-over-TLS, DNS-over-TLS policy, DOH, and DOH policy. (There are likely additional topics...)

This draft specifies some limitations on DNS resolvers a client can use.
Therefore - I would argue - it is fine to discuss whether these limitations are
appropriate and not overbroad.

> 
> --Paul Hoffman>

Greetings,
Mateusz Jończyk