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Re: [Ntp] Antw: Re: Antw: Re: New rev of the NTP port randomization I-D (Fwd: New Version Notification for draft-gont-ntp-port-randomization-01.txt)

Miroslav Lichvar <mlichvar@redhat.com> Wed, 29 May 2019 10:17 UTC

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Date: Wed, 29 May 2019 12:16:54 +0200
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Harlan Stenn <stenn@nwtime.org>
Cc: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, "ntp@ietf.org" <ntp@ietf.org>
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Subject: Re: [Ntp] Antw: Re: Antw: Re: New rev of the NTP port randomization I-D (Fwd: New Version Notification for draft-gont-ntp-port-randomization-01.txt)
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On Wed, May 29, 2019 at 03:02:49AM -0700, Harlan Stenn wrote:
> On 5/29/2019 2:39 AM, Ulrich Windl wrote:
> >>>> Harlan Stenn <stenn@nwtime.org> schrieb am 29.05.2019 um 11:31 in
> > Nachricht
> >> - the window of time where an attack is possible starts when the client
> >>   sends its request, and ends when a valid response is received.

The attacker can prevent the valid responses from being received or
processed simply by sending the client more packets that it can
handle.

> OK, so what?  Low end normal machines might handle 2k packets/second,
> and low end slow machines are lucky to be able to handle 200 packets per
> second.

Your figures are off by several orders of magnitude.

I suspect the attack is practical, at least for clients using only one
server, but nobody has tried it (and published the results) yet.

-- 
Miroslav Lichvar

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