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Re: [Ntp] Details of the fragmentation attacks against NTP and port randomization

Danny Mayer <mayer@ntp.org> Wed, 05 June 2019 23:13 UTC

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To: Hal Murray <hmurray@megapathdsl.net>
Cc: NTP WG <ntp@ietf.org>
References: <20190605215710.7A5DB40605C@ip-64-139-1-69.sjc.megapath.net>
From: Danny Mayer <mayer@ntp.org>
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Date: Wed, 05 Jun 2019 19:13:07 -0400
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Subject: Re: [Ntp] Details of the fragmentation attacks against NTP and port randomization
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On 6/5/19 5:57 PM, Hal Murray wrote:
> mayer@pdmconsulting.net said:
>> The opposition is due to the fact that randomizing the ports doesn't solve
>> the underlying security issue. If I'm an attacker off-path and can get to the
>> target system, I can just run nmap and find out all of the open ports leaving
>> just a few ports to check. Randomizing ports by itself solves nothing here. 
> There is an important idea that isn't specified in "randomization".  When does 
> the randomization happen?
>
> Case A: When a client decides to use IP Address a.b.c.d as a server, open a 
> socket.
>
> Case B: When a client decides to send a packet to IP Address a.b.c.d, open a 
> socket.  When the response arrives (or timeout) close the socket.
>
> nmap will find Case A type systems.  It has a small chance of finding systems 
> using Case B.
>
>
Yes, if you are smart you would want case B. Thar's what I am
advocating. I think I put that in my message.

Danny

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