Re: [dns-privacy] how can we ADoT?

[Tony Finch <[e-mail]>]

Eric Rescorla <[e-mail]> wrote:
> On Wed, Nov 11, 2020 at 11:07 AM Tony Finch <[e-mail]> wrote:
>
> >   2. Signal in an EDNS [@?RFC6891] or DSO [@?RFC8490] option: the
> >     resolver starts by connecting in the clear, and upgrades to an
> >     encrypted connection if the authoritative server supports it.
> >
> >     This is vulnerable to downgrade attacks. The initial cleartext
> >     connection adds latency, and would need to be specified carefully
> >     to avoid privacy leaks.
>
> It's worth noting that one could add an HSTS-like mechanism here. Given
> that a lot of requests are probably return customers, this would likely
> result in quite a lot of lift.

Good point, thanks! I haven't thought about this option enough.

One thing that will make it more tricky is nameserver aliases: it's
relatively common for NS records to refer to servers by names that the
server operator does not know. So I expect that an in-band upgrade to TLS
will have to use IP-address-based authentication, if any.

A nice thing about TLSA records is they also tell the client what name to
look for in the server's cert. (I need to make that more explicit in my
notes.)

Tony.
-- 
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