Re: [Resolverless-dns] Paper on Resolver-less DNS

Eric Osterweil <lists@osterweil.net> Sun, 25 August 2019 18:03 UTC

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From: Eric Osterweil <lists@osterweil.net>
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Date: Sun, 25 Aug 2019 14:03:11 -0400
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To: sy@informatik.uni-hamburg.de
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Subject: Re: [Resolverless-dns] Paper on Resolver-less DNS
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> On Aug 23, 2019, at 5:37 AM, Erik Sy <sy@informatik.uni-hamburg.de>; wrote:
> 

<snip>

>>>> the economy depends on them doing so.
>> 
>>> 
>> 
>>> I find that only 0.9% of the .com domains are signed [2] and having a
>> 
>>> signature does not mean that they can be successfully validated.
>> 
>>  
>> 
>> i suggest you broaden your search for knowledge. for example, this web
>> site may be of interest, along with the monthly reports posted to
>> dns-operations@ by the same authors.
>> 
>>  
>> 
>> https://stats.dnssec-tools.org/
>> 
>>  
>> 
> Anyway, lets assume that all domains and resolvers perfectly support
> DNSSEC and that we have transport encryption between the client and the
> resolver. In this scenario, the client still needs to trust the resolver
> to provide the correct address. Furthermore, having a correctly resolved
> IP address does not solve the problem of communicating to the correct
> server, which is usually the intention of the client.
>> 

I feel like this kind of misses the point of DANE.  DANE specifies the authoritative model for creating and verifying security associations.  One of DANE’s core observations is that if the A record is securely resolved, then that same security substrate should be used to resolve the binding of that name to a certificate/key.  Said differently, the binding of a TLS certificate to a domain name (via the TLSA record) gives the client its assurance that is talking to the correct server.

>>>> if RDNS isn't client software from your point of view, you'll dismiss
>> 
>>>> these assertions.
>> 
>>> 
>> 
>>> RDNS requires the client to trust the used recursive resolver.
>> 
>>  
>> 
>> not for DANE work flows. stub validation is not widely implemented or
>> well supported by DNSSEC, but it works, and existing DANE TLSA clients
>> do this.
>> 
> In my view, DANE TLSA is an approach to do public key pinning. The web
> already collected a lot of experience with public key pinning as this
> can be also done using other protocols than DNS. In summary, the Chrome
> browser deprecated this mechanism last year [1]. Assuming that DANE TLSA
> would be widely supported on client systems, I think that Chrome would
> not start using this mechanism to do public key pinning.
> 
> 1:
> https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/he9tr7p3rZ8/eNMwKPmUBAAJ <https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/he9tr7p3rZ8/eNMwKPmUBAAJ>

I would say this argument also misses a fundamental point.  Architecturally, DNSSEC uses a single root TA to make domain names unambiguous (i.e. collision-free) and verifiable, and DANE adds security associations to certificates by the same infrastructure.  It’s the single-rooted verification hierarchy that makes name-to-object verification collision-free and unambiguous, as opposed to solely leaving it the hands of the multi-rooted Web PKI (though DANE's selector field allows synergy w/ that model).  These assurances are not (afaict) provided by key pinning alone.  

There is a fair amount of writing that discusses this, and numerous presentations.  I’m happy to provide pointers if anyone would like.

Eric