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Re: [Ntp] I-D Action: draft-ietf-ntp-ntpv5-requirements-02.txt

James <james.ietf@gmail.com> Mon, 14 August 2023 11:48 UTC

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From: James <james.ietf@gmail.com>
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Date: Mon, 14 Aug 2023 13:47:43 +0200
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To: Miroslav Lichvar <mlichvar@redhat.com>
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Subject: Re: [Ntp] I-D Action: draft-ietf-ntp-ntpv5-requirements-02.txt
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Thanks for the feedback.

Comments in-line.

- J

> On 14 Aug 2023, at 10:39, Miroslav Lichvar <mlichvar@redhat.com> wrote:
> 
> On Sat, Jul 29, 2023 at 08:45:52AM -0700, internet-drafts@ietf.org wrote:
>> 
>> A New Internet-Draft is available from the on-line Internet-Drafts
>> directories. This Internet-Draft is a work item of the Network Time Protocols
>> (NTP) WG of the IETF.
>> 
>>   Title           : NTPv5 use cases and requirements
>>   Author          : James Gruessing
>>   Filename        : draft-ietf-ntp-ntpv5-requirements-02.txt
> 
> Thanks for updating the draft.
> 
>> From 3.1:
>  NTPv4 has previously suffered from DDoS amplification attacks using a
>  combination of IP address spoofing and private mode commands used in
>  many NTP implementations,
> 
> I suggest replacing "many" with "some". AFAIK only the ntp.org ntpd
> and its fork ntpsec have this issue.

I intend on updating that section also based on feedback from Ulrich - I've added your suggestion onto the issue https://github.com/fiestajetsam/draft-gruessing-ntp-ntpv5-requirements/issues/24 so I don't lose track.

> 
>> From 4.1:
>   Client and server protocol modes MUST be supported, and other modes
>   such as symmetric and broadcast MAY be supported and SHOULD NOT be
>   required by implementors to implement.  Considerations should be
>   made in these modes to avoid implementations and deployments from
>   vulnerabilities and attacks.
> 
> So we are postponing the decision on which modes to support to the
> protocol specification? I was hoping the requirements draft would
> provide more guidance than "MAY".
> 
> I think I suggested this before. Instead of naming modes, why not
> simply say: "NTPv5 MUST be resilient to off-path and replay attacks"?
> I think that is a reasonable requirement for any internet protocol
> that nobody should have any objections to it.
> 
> The people who think symmetric and/or broadcast need to be
> supported will be forced to find a fix, or if they cannot do that at
> least understand it well enough to realize why they shouldn't be
> supported.

The text that I ended up ultimately putting in was based in part on the discussion at IETF 117. I don't immediately disagree with your proposal, however given as this point went through a consensus call such a change may cause even further discussion being required.

https://github.com/fiestajetsam/draft-gruessing-ntp-ntpv5-requirements/issues/41

> 
> -- 
> Miroslav Lichvar
> 
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