On Thu, Mar 12, 2020 at 12:03:10AM +0100, Kurt Roeckx wrote:
> On Wed, Mar 11, 2020 at 02:30:11PM -0700, Hal Murray wrote:
> > 
> > Any thoughts about how to get the pool to support it?
> 
> I think that if we want to use NTS with the pool, that we need a
> secure way of getting the list of servers. That probably means
> either DNSSEC or TLS. Both have their advantages and
> disadvantages.

Can we describe them?

DNSSEC advantages
- smaller load on servers

DNSSEC disadvantages
- additional complexity for NTS clients
- not widely supported (i.e. NTS clients would need to have their own
  full DNS resolver like libunbound)
- not always available (e.g. DNS blocked to Internet and local servers
  don't support it)

TLS advantages
- already used by NTS

TLS disadvantages
- much higher load on servers

Anything important missing?

One of my suggestions was to specify a NTS-KE redirect where the
server wouldn't provide cookies, but a TTL and a list of hostnames and
addresses. It would basically be DNS over NTS-KE. Easy to implement on
both servers and clients. If the clients were caching the results
properly, the load should be a fraction of the NTS-KE load at the NTP
servers. Would that make sense for pool.ntp.org?

There is a different problem that might need to be addressed first.
MITM attackers could circumvent NTS simply by joining the pool. How
could that be prevented or minimized? Not accept any new members and
trust the old ones they won't do any harm? A year long waiting list
for NTS?

-- 
Miroslav Lichvar

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