Re: [Doh] WG Review: DNS Over HTTPS (doh)

Adam Roach <adam@nostrum.com> Mon, 25 September 2017 23:38 UTC

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To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
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Subject: Re: [Doh] WG Review: DNS Over HTTPS (doh)
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On 9/25/17 6:16 PM, Stephen Farrell wrote:
> A nit, a question and a comment:
>
> On 26/09/17 00:03, Ted Hardie wrote:
>> Adam,
>>
>> Thanks for summarizing the discussion and its outcomes.  Looking at the
>> revised charter, I noticed that it currently says "The use of HTTPS and its
>> existing PKI provides integrity and confidentiality, and it also allows the
>> transport to interoperate with common HTTPS infrastructure and policy."
> Nit: Not sure if it's worth nothing, but the integrity service here
> is different from DNSSEC, and clients need to be cognizant of that.
> Probably obvious though.

It's not different; it's in addition to. The mechanism being described 
would pass DNSSEC information through unscathed.

>
>> The choice not to specify a particular version means that there may be more
>> than one transport.  You may wish to rephrase this or elide it to reflect
>> the decision taken on that point.
> This para:
>
> "
> While access to DNS-over-HTTPS servers from JavaScript running
> in a typical web browser is not the primary use case for this
> work, precluding the ability to do so would require additional
> preventative design. The Working Group will not engage in such
> preventative design.
> "
>
> ... strikes me as weird, given that it didn't say what is the
> "primary" use-case. I think that needs fixing or may cause
> confusion later. The question is: did I miss where you said what
> was the primary use-case?

It's pretty similar to DPRIVE (or, really, DNS in general). I see that 
DPRIVE does have some text that seems to serve the purpose, so I'll copy 
it over with minor tweaks like so:

> The primary focus of this Working Group is to develop a mechanism that
> provides confidentiality and connectivity between DNS Clients and 
> Iterative
> Resolvers.  While access to DNS-over-HTTPS servers from JavaScript 
> running in
> a typical web browser is not the primary use case for this work, 
> precluding
> the ability to do so would require additional preventative design. The 
> Working
> Group will not engage in such preventative design.




> The comment: I find this version no better than the last in
> terms of saying that the WG needs to consider the scope within
> which DNS answers are used. And that was my major issue with
> the last iteration, so overall, this version doesn't seem that
> much better to me. My suggestion is to add text along these
> lines:
>
> "The WG will analyse the security and privacy issues that could
> arise from accessing DNS in this manner. For example it'd clearly
> be bad if JavaScript from random web sites could poison the OS's
> DNS cache (though hopefully no implementation would allow that).
> The manner in which that analysis is documented will be decided
> by the WG."

What I'm seeing here is that the IETF isn't going to propose any changes 
to the web security model. In most cases, I think this goes without 
saying; but since you and Ted have both raised the issue, I suppose it 
bears mention in the charter. I've tweaked your phrasing a bit:

> The Working Group will analyze the security and privacy issues that could
> arise from accessing DNS over HTTPS. In particular, the Working Group will
> ensure that access to DNS information from a JavaScript context will 
> not have
> adverse impact on the host operating system's DNS cache. The manner in 
> which
> such analysis is performed will be decided by the working group.

/a