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

Hi All,

For those curious about the success probability of off-path attacks with
randomized transmit timestamps, I would suggest refering to Section 7 of
the paper "Security of NTP's datagram protocol
<https://eprint.iacr.org/2016/1006/20161026:151159>".  It has detailed
analysis of off-path attacks on NTP where attacker tries to predict the
transmit timestamp.

Best,
Aanchal Malhotra.

On Fri, Jun 7, 2019 at 7:05 AM Fernando Gont <fgont@si6networks.com> wrote:

> On 4/6/19 12:47, Harlan Stenn wrote:
> >
> >
> > On 6/3/2019 11:37 PM, Fernando Gont wrote:
> >> On 29/5/19 21:58, Fernando Gont wrote:
> >>> Harlan,
> >>>
> >>> Responding this one in a separate email, since it seems we're
> converging
> >>> on something...
> >>>
> >>> On 29/5/19 13:15, Harlan Stenn wrote:
> >>>>
> >>> [....]>> Using randomized port numbers requires yet additional effort
> on
> >>> the side
> >>>>> of the attacker. And means that the attacker now needs to guess the
> >>>>> client port, or otherwise his packets will not even make it to the
> ntp
> >>>>> process.
> >>>>
> >>>> If your point is to change the last sentence of RFC590 9.1 where it
> says:
> >>>>
> >>>>    srcport: UDP port number of the server or reference clock.  This
> >>>>    becomes the destination port number in packets sent from this
> >>>>    association.  When operating in symmetric modes (1 and 2), this
> field
> >>>>    must contain the NTP port number PORT (123) assigned by the IANA.
> In
> >>>>    other modes, it can contain any number consistent with local
> policy.
> >>>>
> >>>> to:
> >>>>
> >>>>    ... In other modes, it SHOULD contain any number consistent with
> >>>>    local policy.
> >>>>
> >>>> I'm fine with that.>
> >>> Yes. That's the whole point of this document.
> >>
> >>
> >> Sorry. THe point of the document is to change that to "SHOULD randomize
> >> the port number". THat's the BCP of the transport area.
> >
> > If your local policy is randomization, that's fine.
>
>
> The transport area has produced a BCP recommending that ephemeral port
> numbers should be randomized.
>
> Are we just implicitly saying that we don't care about the advice of the
> transport area?
>
>
> --
> Fernando Gont
> SI6 Networks
> e-mail: fgont@si6networks.com
> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
>
>
>
>
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