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

Fernando Gont <fgont@si6networks.com> Wed, 29 May 2019 04:39 UTC

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To: "Majdi S. Abbas" <msa@latt.net>
Cc: "Gary E. Miller" <gem@rellim.com>, ntp@ietf.org
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From: Fernando Gont <fgont@si6networks.com>
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Message-ID: <2107d74d-02da-cbd7-7a12-2837cb2e47a2@si6networks.com>
Date: Wed, 29 May 2019 00:37:17 -0400
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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 28/5/19 23:20, Majdi S. Abbas wrote:
> Fernando,
> 
>     Randomizing the source port is pointless.  As Danny has noted, t1 already acts as a 2^64 nonce on each client mode chime request.  This sufficiently hardens the unauthenticated case to an off path attacker.  If additional security is required, authentication (via classic PSK, or NTS modes) should be used.
> 
>     Per session randomization doesn't resolve these issues -- the stated rationale for both the draft and filed CVE is hardening to off path attacks, which we've just covered.
> 
>     "Because it's best practice" isn't a reason -- it's a crutch to save a draft that was filed due to an insufficient understanding of RFC 5905 and current implementations of NTPv4.  

Oh, by the way. While you enlighten me why you need a fixed well-known
port number for the client, and how necessary this is, please also
elaborate on how I'm running multiple NTP clients behind a NAT box.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
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