Re: [Ntp] NTP Security (was NTPv5: big picture)

Miroslav Lichvar <mlichvar@redhat.com> Tue, 19 January 2021 17:26 UTC

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Date: Tue, 19 Jan 2021 18:26:24 +0100
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Magnus Danielson <magnus@rubidium.se>
Cc: ntp@ietf.org
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Subject: Re: [Ntp] NTP Security (was NTPv5: big picture)
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On Tue, Jan 19, 2021 at 05:50:20PM +0100, Magnus Danielson wrote:
> On 2021-01-19 14:51, Miroslav Lichvar wrote:
> > The assumption is that both your DNSSEC and NTS was compromised at
> > some point. You found out and rebuilt your infrastructure from
> > scratch, but the attacker can still perform a MITM attack on your
> > device if it doesn't know the current date in order to validate the
> > certificate/records.
> >
> Outside of our scope. Way outside. We assume we can trust whatever these
> mechanisms provide and our trust becomes tied to them. If you have ways
> to attack that, this is not really the place to document those.

I don't agree. The mechanisms should be trusted only if used as
intended, i.e. a full validation is performed. Skipping the time
checks is a security risk. You seem to be saying that's ok, that you
can combine outputs from two separate mechanisms using untrusted data
and get a trusted output. I don't think that's the case. We can ask
the DNS and CFRG groups.

-- 
Miroslav Lichvar