DNS Inspection Denial of Service Vulnerability

Question

Advisory ID: cisco-sa-20131009-asa
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20131009-asa
I have a Pix running version 8.0.4 with the following configuration:
inside interface:      192.168.231.254/255.255.255.0
outside interface:     10.100.2.254/255.255.255.0
no nat-control
access-list test permit ip any any log
access-group test in interface outside
access-group test in interface inside
I have a window 2008R2 residing on the Internal interface of the firewall.  The domain controller resides on the outside interface of the firewall.
I went ahead and implement the change recommended by Cisco
access-list DNS_INSPECT extended permit udp any any
class-map DNS_INSPECT_CP
   match access-list  DNS_INSPECT
policy-map global_policy
   class DNS_INSPECT_CP
     inspect dns preset_dns_map
However, after implement the workaround, my windows 2008R2 machine on the inside network can NOT join with AD on the outside network.
on the log of the firewall I see this:
Oct 31 14:34:09 192.168.231.254 %PIX-4-410001: Dropped UDP DNS request from inside:192.168.231.180/61780 to outside:10.100.2.128/389; label length 132 bytes exceeds protocol limit of 63 bytes
Oct 31 14:34:17 192.168.231.254 %PIX-4-410001: Dropped UDP DNS request from inside:192.168.231.180/61780 to outside:10.100.2.128/389; label length 132 bytes exceeds protocol limit of 63 bytes
I even change the DNS maximum length to 8192 but it still does not work. 
I remove the recommendation from the configuration, everything works fine after that.
Anyone knows why?
Thanks in advance

Answer 1

Julio Carvajal wrote:U do not have this command right available at the CLI rightmessage-length maximum client auto
     I do
CiscoPix# sh run policy-map
policy-map type inspect dns preset_dns_map
parameters
  message-length maximum 1024
  message-length maximum client auto
policy-map global_policy
class inspection_default
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect rtsp
  inspect skinny
  inspect esmtp
  inspect sunrpc
  inspect tftp
  inspect sip
  inspect xdmcp
  inspect sqlnet
  inspect dns preset_dns_map
class class_sunrpc_tcp
  inspect sunrpc
class DNS_INSPECT_CP
  inspect dns preset_dns_map
CiscoPix#
Julio Carvajal wrote: Then clear-local host try one more time and provide the logs.Note:access-list test permit ip any any logaccess-group test in interface outsideaccess-group test in interface insideThat ACL means u have no firewall in place
I am very aware of this.  At this point, it does not matter, it just want the firewall to function like a routing device.
It still does NOT work.  Here is the log:
Oct 31 17:57:25 192.168.231.254 %PIX-6-106100: access-list test permitted udp inside/192.168.231.180(61982) -> outside/10.100.2.128(53) hit-cnt 1 first hit [0x63a9cac7, 0x0]
Oct 31 17:57:25 192.168.231.254 %PIX-6-106100: access-list test permitted udp inside/192.168.231.180(61983) -> outside/10.100.2.128(389) hit-cnt 1 first hit [0x63a9cac7, 0x0]
Oct 31 17:57:25 192.168.231.254 %PIX-4-410001: Dropped UDP DNS request from inside:192.168.231.180/61983 to outside:10.100.2.128/389; label length 132 bytes exceeds protocol limit of 63 bytes
Oct 31 17:57:32 192.168.231.254 %PIX-4-410001: Dropped UDP DNS request from inside:192.168.231.180/61983 to outside:10.100.2.128/389; label length 132 bytes exceeds protocol limit of 63 bytes
Oct 31 17:57:33 192.168.231.254 %PIX-6-106100: access-list test permitted udp inside/192.168.231.180(50955) -> outside/10.100.2.128(53) hit-cnt 1 first hit [0x63a9cac7, 0x0]