Name Resolution issue with one domain

Wed Mar 21 19:27:43 UTC 2012

I don’t think the target is blocking as I get the following:

dig www.dubaiairport.com

; <<>> DiG 9.8.1 <<>> www.dubaiairport.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36668
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0

;; QUESTION SECTION:
;www.dubaiairport.com.          IN      A

;; ANSWER SECTION:
www.dubaiairport.com.   7200    IN      A       213.42.55.169

;; AUTHORITY SECTION:
dubaiairport.com.       172799  IN      NS      dcaowa01.dubaiairport.com.
dubaiairport.com.       172799  IN      NS      svr-b003.dubaiairport.com.

;; Query time: 337 msec
;; SERVER: 192.94.73.20#53(192.94.73.20)
;; WHEN: Wed Mar 21 19:25:08 2012
;; MSG SIZE  rcvd: 100

The point is your firewall should NOT block outbound queries for port 53 or other ports.   There is a well know cache poisoning attack based on knowing the outbound (source) port that is going to be used so the port should be randomized.   Port 53 MUST be accessible on the target DNS server as that is the one that is going to answer the query.

________________________________
From: bind-users-bounces+jlightner=water.com at lists.isc.org [mailto:bind-users-bounces+jlightner=water.com at lists.isc.org] On Behalf Of babu dheen
Sent: Wednesday, March 21, 2012 3:14 PM
To: Matus UHLAR - fantomas; bind-users at lists.isc.org
Subject: Re: Name Resolution issue with one domain

Dear All,

When i executed #dig www.dubaiairport.com<http://www.dubaiairport.com>, i am getting bleow response

; <<>> DiG 9.3.4-P1 <<>> www.dubaiairport.com<http://www.dubaiairport.com>
;; global options:  printcmd
;; connection timed out; no servers could be reached

 When i checked the firewall logs, as you all confirmed, traffic is leaving from both non standard and standard port. But firewall logs clearly shows that traffic from source port =53 and its getting dropped. But other DNS traffic towards various domains also going with source port 53 for which we have no issue.

 Is this port restriction done at remote domain firewall?
 Is there any way to enforce non standard port for this domain query at our BIND level from our side?

Mar 21 21:50:26 start_time="2012-03-21 21:47:54" duration=151 policy_id=20 service=dns proto=17 src zone=Inter-Connect dst zone=External action=Permit sent=403 rcvd=0 src=10.1.1.1 dst=213.42.52.75 src_port=53 dst_port=53 src-xlated ip=10.1.1.1 port=53 dst-xlated ip=213.42.52.75 port=53 session_id=512159 reason=Close - AGE OUT

Mar 21 21:50:46 start_time="2012-03-21 21:49:15" duration=90 policy_id=24 service=dns proto=17 src zone=Inter-Connect dst zone=External action=Permit sent=927 rcvd=0 src=10.1.1.1 dst=213.42.52.79 src_port=53 dst_port=53 src-xlated ip=10.1.1.1 port=53 dst-xlated ip=213.42.52.75  port=53 session_id=451904 reason=Close - AGE OUT

Regards
Babu

From: Matus UHLAR - fantomas <uhlar at fantomas.sk>
To: bind-users at lists.isc.org
Sent: Wednesday, 21 March 2012 11:41 AM
Subject: Re: Name Resolution issue with one domain

On 21.03.12 09:23, Mark Andrews wrote:
>Stupid firewall rules in front of the nameservers.  They block
>traffic sent from port 53 which is the port lots of nameservers
>used to send query traffic.  When will firewall administrators learn
>that the source ports can be anything, that they are not significant,
>and that blocking traffic based on the source port is stupid.

maybe the admin set that up to force local servers using random ports,
instead of 53, for outgoing requests. Nobody should use port 53 for
_ougtoing_ requests.

>bsdi# dig -b 0.0.0.0#53 www.dubaiairport.com @svr-b003.dubaiairport.com
>09:13:17.909493 211.30.172.21.53 > 213.42.52.75.53:  18071+$ [1au] A? www.dubaiairport.com. ar: OPT UDPsize=4096 (49)
>09:13:22.918018 211.30.172.21.53 > 213.42.52.75.53:  18071+$ [1au] A? www.dubaiairport.com. ar: OPT UDPsize=4096 (49)
>09:13:27.928099 211.30.172.21.53 > 213.42.52.75.53:  18071+$ [1au] A? www.dubaiairport.com. ar: OPT UDPsize=4096 (49)
>
>; <<>> DiG 9.9.0rc2 <<>> -b 0.0.0.0#53 www.dubaiairport.com @svr-b003.dubaiairport.com
>;; global options: +cmd
>;; connection timed out; no servers could be reached
>bsdi#

--
Matus UHLAR - fantomas, uhlar at fantomas.sk<mailto:uhlar at fantomas.sk> ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
Quantum mechanics: The dreams stuff is made of.
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