response-policy {

                zone “rpz”;

        };

Then add the correspondingly named zone at the end of the file. For purposes of testing, I added a zone as a forward only zone so I could perform a network capture to see what exactly transpires when a name in the RPZ is resolved.

zone “rpz” {

      type master;

      file “rpz.db”;

      allow-query { none; };

      allow-transfer { none; };

};

Then you just have to make a rpz.db where you store your named files:

$TTL 60
$ORIGIN rpz.
@            IN    SOA  localhost. root.localhost.  (
                          2   ; serial
                          3H  ; refresh
                          1H  ; retry
                          1W  ; expiry
                          1H) ; minimum
                  IN    NS    localhost.

www.windstream.com    CNAME    www.yahoo.com.

Restarted named and ran “rndc flush” to avoid serving cached content instead of the RPZ host data. Then ran a few tests and confirmed that the resolution configured in the rpz zone:

[lisa@fedora02 named]# dig +short www.windstream.com @localhost

www.yahoo.com.

atsv2-fp.wg1.b.yahoo.com.

98.139.183.24

98.138.252.30

98.139.180.149

98.138.253.109

[lisa@fedora02 named]# dig +short dell905.windstream.com @localhost

ns4.windstream.com.

173.186.244.139

[lisa@fedora02 named]# dig +short www.google.com @localhost

216.58.218.228

In this process, I learnt something interesting about ICS’s implementation of RPZ: it still performs the query and then overrides the results. Odd waste of cycles, but the resolution that was subsequently turned into yahoo’s address from the rpz zone. Looking up a windstream.com host that isn’t in my RPZ and I got another query out to 8.8.8.8 which was expected. Query to something not in the forward zone and not in the rpz zone and I get no traffic to 8.8.8.8 (because it follows my normal forwarding which is to our ISP’s DNS).

I was curious if this meant rpz could not be used to publish a bad hostname locally – but attempting to resolve a bad hostname (added abadhost.windstream.com with the same CNAME to Yahoo and reloaded my zone) worked just fine.

[root@fedora02 ~]# dig abadhost.windstream.com @localhost

; <<>> DiG 9.11.1-P2-RedHat-9.11.1-2.P2.fc26 <<>> abadhost.windstream.com @localhost
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8382
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 4, ADDITIONAL: 3

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: 1aa34751c5df7f78857a921259a8706fb5e1741a46eb5352 (good)
;; QUESTION SECTION:
;abadhost.windstream.com. IN A

;; ANSWER SECTION:
abadhost.windstream.com. 5 IN CNAME www.yahoo.com.
www.yahoo.com. 1800 IN CNAME atsv2-fp.wg1.b.yahoo.com.
atsv2-fp.wg1.b.yahoo.com. 60 IN A 98.139.180.149
atsv2-fp.wg1.b.yahoo.com. 60 IN A 98.138.253.109
atsv2-fp.wg1.b.yahoo.com. 60 IN A 98.139.183.24
atsv2-fp.wg1.b.yahoo.com. 60 IN A 98.138.252.30

;; AUTHORITY SECTION:
wg1.b.yahoo.com. 172800 IN NS yf3.a1.b.yahoo.net.
wg1.b.yahoo.com. 172800 IN NS yf4.a1.b.yahoo.net.
wg1.b.yahoo.com. 172800 IN NS yf1.yahoo.com.
wg1.b.yahoo.com. 172800 IN NS yf2.yahoo.com.

;; ADDITIONAL SECTION:
yf1.yahoo.com. 86400 IN A 68.142.254.15
yf2.yahoo.com. 86400 IN A 68.180.130.15

;; Query time: 1204 msec
;; SERVER: ::1#53(::1)
;; WHEN: Thu Aug 31 16:24:15 EDT 2017
;; MSG SIZE rcvd: 315

But there is a query that goes out to the name server and a ‘no such name’ result returned. Odd.