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Date: Sun, 12 Jan 2014 23:15:52 +0100
From: Fabian Wenk <fabian@wenks.ch>
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To: freebsd-security@freebsd.org
Subject: Re: UNS: Re: NTP security hole CVE-2013-5211?
References: <B0F3AA0A-2D23-424B-8A79-817CD2EBB277@FreeBSD.org>
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Hello Xin

On 10.01.2014 06:16, Xin Li wrote:
> On 1/9/14, 7:14 PM, Garrett Wollman wrote:
>> <<On Thu, 09 Jan 2014 21:08:41 +0700, Eugene Grosbein
>> <eugen@grosbein.net> said:
>>
>>> Other than updating ntpd, you can filter out requests to
>>> 'monlist' command with 'restrict ... noquery' option that
>>> disables some queries for the internal ntpd status, including
>>> 'monlist'.
>>
>> For a "pure" client, I would suggest "restrict default ignore"
>> ought to be the norm.  (Followed by entries to unrestrict localhost
>> over v4 and v6.)
>
> That would block clock synchronization too, unless one explicitly
> unrestrict all NTP servers.  With pool.ntp.org, this is not really
> practical.
>
> The current default on head stable branches should work for most people.

I just check out through svnweb, but I would suggest the 
following settings, which will properly work for all versions of 
ntpd. See also the added 'limited' options, it helps to protect 
from spoofed amplification attacks too:

# by default, don't trust and don't allow modifications
# see -> https://support.ntp.org/bugs/show_bug.cgi?id=320
# should be fixed with ntp-4.2.5p178 (or later), eg. -4 / -6 not
# needed any more
restrict -4 default limited kod notrap nomodify nopeer noquery
restrict -6 default limited kod notrap nomodify nopeer noquery
restrict default limited kod notrap nomodify nopeer noquery


bye
Fabian