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

Erik Sy <sy@informatik.uni-hamburg.de> Thu, 15 August 2019 10:43 UTC

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To: Ben Schwartz <bemasc@google.com>
Cc: resolverless-dns@ietf.org
References: <ec8d77e5-6161-c7e6-3ca8-ccf0a99c1b62@informatik.uni-hamburg.de> <CAHbrMsBhR1yaLxQk7wZk54Jdf5nvkS03KC3UTae0Famu2+SV8g@mail.gmail.com>
From: Erik Sy <sy@informatik.uni-hamburg.de>
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Date: Thu, 15 Aug 2019 12:43:19 +0200
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Subject: Re: [Resolverless-dns] Paper on Resolver-less DNS
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Thank you for your feedback, Ben!

On 8/14/19 23:11, Ben Schwartz wrote:
> Thanks for conducting this investigation, Erik!
>
> In my view, the two main concerns with resolverless architectures have
> been (1) simplifying stolen key attacks and (2) potential interference
> with DNS-based load balancing.
>
> Currently, an attacker who has stolen a TLS private key also needs
> control of the victim's network in order to mount an impersonation
> attack.  Resolverless DNS (especially without DNSSEC, as in your
> model) might make these attacks much easier to execute, by sending the
> victim a DNS record that points the compromised domain to the
> attacker's IP address.
>
The described attack of a compromised TLS private key or even a broken
PKI is quite strong. Certainly, it is not a design goal of DNS to
mitigate these attacks. However, let's assume that this attack is
relevant. In the traditional DNS as well as in the server-less DNS
network paths involving the HTTPS server (victim) and the corresponding
authoritative nameserver are vulnerable to such an impersonation attack
as shown in this figure
(https://erik-sy.de/Resolver-less_DNS_Attack.pdf). Resolver-less DNS
replaces only the vulnerable paths involving the resolver with the paths
involving the HTTP server providing the DNS records. In my view, none of
these DNS designs protects against the described impersonation attacks
and the attack surface remains substantially the same across these designs.

> Domains that rely on DNS-based load balancing have concerns about
> third parties handing out DNS records for their domains.  These third
> parties might (accidentally) provide the same DNS record to all of
> their users, overloading a particular server instead of spreading the
> load across many servers.

I think, that this is not a new problem introduced by the resolver-less
DNS design. Moreover, it describes a general drawback of DNS-based load
balancing that one is dependent on 'unreliable' third parties to spread
the load. For example, it is known that some resolvers ignore small TTLs
of their cached DNS records impacting this load balancing mechanism.

Is anybody interested in co-authoring an ID on resolver-less DNS?

Best regards,
Erik 

> If you're interested in this topic, I hope you'll think a bit about
> these problems, and see if you find a way to solve them.
>
> On Tue, Aug 13, 2019 at 8:07 AM Erik Sy <sy@informatik.uni-hamburg.de
> <mailto:sy@informatik.uni-hamburg.de>> wrote:
>
>     Hi all,
>
>     I wrote a paper to clarify the design of resolver-less DNS and to
>     investigate its feasibility.
>     You can find the paper here:
>     https://svs.informatik.uni-hamburg.de/publications/2019/2019-08-13-Sy-preprint-Enhanced_Performance_and_Privacy_via_Resolver-Less_DNS.pdf
>
>     In total, I think this is a great performance-optimization especially
>     for clients on high-latency access networks. Furthermore, it can
>     improve
>     the client's privacy posture towards the recursive DNS resolver.
>
>     Best regards,
>     Erik
>
>
>     -- 
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>