Re: allow-query does not seem to be working
On 08/08/2016 20:59, Frank Even wrote: > Thanks for the info. Also I'll have to note that I completely missed > that the "offending IP" is one of the .uk root servers so the next > logical conclusion is I've probably got a box in one of my environments > driving an amplification attack of some sort or something at those IPs > that I need to figure out. Sorry for the bother and thanks for the > feedback. Much appreciated. The host in question (156.154.100.3) is nsa.nic.uk, but is actually operated by UltraDNS / Neustar. However to me it looks like _you're_ the one sending the queries, as evidenced by the 'A?' in your tcpdump log (where the ? indicates query, and 'A' on its own would be the response) and also the destination port of 53. Ray ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
Re: allow-query does not seem to be working
Thanks for the info. Also I'll have to note that I completely missed that the "offending IP" is one of the .uk root servers so the next logical conclusion is I've probably got a box in one of my environments driving an amplification attack of some sort or something at those IPs that I need to figure out. Sorry for the bother and thanks for the feedback. Much appreciated. On Mon, Aug 8, 2016 at 10:51 AM, Ray Bellis wrote: > On 08/08/2016 18:43, Darcy Kevin (FCA) wrote: > > As already noted, allow-query will cause you to send back a REFUSED > > response. That’s sort of the whole point of the REFUSED RCODE. > > > > > > > > If you want to not send back any response **whatsoever**, then take a > > look at the “blackhole” statement, but, honestly, this kind of “drop” > > function may, depending on network topology, be more efficiently > > performed in your firewall or IDS/IPS. > > > > > > > > Be aware that a client that doesn’t get a response may retry the query, > > so simply “dropping” queries may ultimately prove counter-productive. > > and also see Mark Andrew's Internet Draft on this very topic: > > https://tools.ietf.org/html/draft-ietf-dnsop-no-response-issue-03 > > Ray > > ___ > Please visit https://lists.isc.org/mailman/listinfo/bind-users to > unsubscribe from this list > > bind-users mailing list > bind-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/bind-users > ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
Re: allow-query does not seem to be working
On 08/08/2016 18:43, Darcy Kevin (FCA) wrote: > As already noted, allow-query will cause you to send back a REFUSED > response. That’s sort of the whole point of the REFUSED RCODE. > > > > If you want to not send back any response **whatsoever**, then take a > look at the “blackhole” statement, but, honestly, this kind of “drop” > function may, depending on network topology, be more efficiently > performed in your firewall or IDS/IPS. > > > > Be aware that a client that doesn’t get a response may retry the query, > so simply “dropping” queries may ultimately prove counter-productive. and also see Mark Andrew's Internet Draft on this very topic: https://tools.ietf.org/html/draft-ietf-dnsop-no-response-issue-03 Ray ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
RE: allow-query does not seem to be working
As already noted, allow-query will cause you to send back a REFUSED response.
That’s sort of the whole point of the REFUSED RCODE.
If you want to not send back any response *whatsoever*, then take a look at the
“blackhole” statement, but, honestly, this kind of “drop” function may,
depending on network topology, be more efficiently performed in your firewall
or IDS/IPS.
Be aware that a client that doesn’t get a response may retry the query, so
simply “dropping” queries may ultimately prove counter-productive.
- Kevin
[FCA_Pantone_email]
--
Kevin Darcy
NAFTA Information Security Projects
FCA US LLC
1075 W Entrance Dr,
Auburn Hills, MI 48326
USA
Telephone: +1 (248) 838-6601
Mobile: +1 (810) 397-0103
Email: kevin.da...@fcagroup.com
From: bind-users [mailto:bind-users-boun...@lists.isc.org] On Behalf Of Frank
Even
Sent: Saturday, August 06, 2016 4:42 PM
To: bind-users
Subject: allow-query does not seem to be working
I have a group of servers serving out multiple addresses via anycast. I've
been made aware that an IP outside of our network is hitting the boxes with
queries, and we're returning data to the client.
With allow-query and allow-recursion locked to our subnets, this outside host
is still getting responses, and I'm trying to figure out why.
named.conf snippet:
allow-query { mynets; };
allow-recursion { mynets; };
Yet in response to a host not from one of the subnets allowed, we're getting
requests and returning some kind of response:
# tcpdump -i any -nvv src $myhost and dst 156.154.100.3
tcpdump: listening on any, link-type LINUX_SLL (Linux cooked), capture size
65535 bytes
13:37:30.578020 IP (tos 0x0, ttl 64, id 5059, offset 0, flags [none], proto UDP
(17), length 81)
$myhost.33941 > 156.154.100.3.domain: [bad udp cksum f39c!] 54976 [1au] A?
www.sparknewspaper.co.uk. ar: . OPT
UDPsize=4096 OK (53)
13:37:30.578025 IP (tos 0x0, ttl 64, id 5059, offset 0, flags [none], proto UDP
(17), length 81)
$myhost.33941 > 156.154.100.3.domain: [bad udp cksum f39c!] 54976 [1au] A?
www.sparknewspaper.co.uk. ar: . OPT
UDPsize=4096 OK (53)
13:37:30.644502 IP (tos 0x0, ttl 64, id 5060, offset 0, flags [none], proto UDP
(17), length 79)
$myhost.61737 > 156.154.100.3.domain: [bad udp cksum fef9!] 7832 [1au] A?
silverstonepaint.co.uk. ar: . OPT UDPsize=4096
OK (51)
13:37:30.644505 IP (tos 0x0, ttl 64, id 5060, offset 0, flags [none], proto UDP
(17), length 79)
$myhost.61737 > 156.154.100.3.domain: [bad udp cksum fef9!] 7832 [1au] A?
silverstonepaint.co.uk. ar: . OPT UDPsize=4096
OK (51)
13:37:30.722628 IP (tos 0x0, ttl 64, id 5061, offset 0, flags [none], proto UDP
(17), length 68)
If an IP is not allowed as part of an "allow-query" statement, should the name
server still be returning any responses?
BIND version - BIND 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6
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Re: allow-query does not seem to be working
On 6 August 2016 at 21:41, Frank Even wrote: > If an IP is not allowed as part of an "allow-query" statement, should the > name server still be returning any responses? I would have expected the response to be one of REFUSED. ___ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
