Re: [Ntp] Antw: [EXT] Re: Quick review of WGLC for status change for draft‑ietf‑ntp‑update‑registries

[Miroslav Lichvar <[e-mail]>]

On Mon, Aug 08, 2022 at 04:48:16AM -0700, Harlan Stenn wrote:
> I was easily able to have the new code auto-detect if an NTP packet was:
> 
> - just a base packet
> - a base packet with a legacy MAC
> - a base packet with EFs and a legacy MAC
> - a base packet with EFs and a MAC-EF
> 
> No trouble at all.  And none of the above needed the extended EF size
> required by 7822.

We discussed this before, more than once.

If you allow short extension fields, you will not be able to detect
whether a request contains an unknown extension field or an Autokey
MAC using an old cookie. The protocol may be able recover, but that's
not how things should be done.

Here is an example:

04 1b 00 14 cc e2 c8 47 71 95 79 64 c4 71 e8 72 7e bf fb cd

Which of the two is it?

-- 
Miroslav Lichvar