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

Harlan Stenn <stenn@nwtime.org> Tue, 04 June 2019 09:47 UTC

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To: Fernando Gont <fgont@si6networks.com>, ntp@ietf.org
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From: Harlan Stenn <stenn@nwtime.org>
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Date: Tue, 4 Jun 2019 02:47:42 -0700
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Subject: Re: [Ntp] 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 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.

I'm happy with what I wrote.

What I think is needed here is robust mechanism, not single-perspective
policy.

> Thanks,
> 

-- 
Harlan Stenn, Network Time Foundation
http://nwtime.org - be a Member!