Configuring basic DNS service with bind

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Basic Bind configuration

1. yum -y install bind bind-utils
2. yum remove bind-chroot
3. Edit /etc/named.conf and append following lines:

   zone "rekallsoftware.com." IN {
   type master;
   file "rekallsoftware.com.forward";
   };

4. In '/etc/named.conf' make following modifications:
   1. listen-on port 53 {127.0.0.1; any;};
   2. allow-query {localhost; 10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16;};
   3. dnssec-enable no;
   4. dnssec-validation no;
5. Go to /var/named and create rekallsoftware.com.forward with contents similar to:

   $TTL 3600
   @ SOA ns.rekallsoftware.com. root.rekallsoftware.com. (1 15m 5m 30d 1h)
   NS ns.rekallsoftware.com.
   A 10.1.2.3
   ns              IN      A       10.1.1.1
   www             IN      A       10.1.2.3

6. Start or restart DNS with "service named restart" command.
7. Try "nslookup rekallsoftware.com 127.0.0.1"
8. Try "nslookup www.google.co.in 127.0.0.1". This will only work if machine has direct access to Internet at least for outgoing UDP port 53.

Setup bind on CentOS 7

For CentOS 7 following small differences are important:

1. For starting bind after configuring as suggested above use:

   systemctl enable bind
   systemctl start bind

2. For allowing port 53 in firewall use:

   firewall-cmd --permanent --add-port=53/tcp
   firewall-cmd --permanent --add-port=53/udp
   firewall-cmd --reload
   firewall-cmd --list-all

   Add '--zone=internal' if zones are being used

Refer http://www.unixmen.com/setting-dns-server-centos-7/ for information including SELinux commands to setup bind with SELinux enabled.

Automated bind configuration

For automated bind configuration using ansible playbooks use:

---
  - name: Configure DNS using bind
    hosts: dns_servers
    remote_user: root
 
    vars:
      zone_names: 
        - rekallsoftware.com.
      zone_address: 1.1.1.1
      allow_query_from: "10.0.0.0/8; 172.16.0.0/12; 192.168.0.0/16;"
      name_server: private-dns
      recursion: yes
      servers:
        - { hostname: base1, ip: 10.3.1.23 }
        - { hostname: ansible, ip: 192.168.122.101 }
        - { hostname: private-dns, ip: 192.168.122.102 }
        - { hostname: ldap, ip: 192.168.122.103 }
        - { hostname: git, ip: 192.168.122.104 }
        - { hostname: wiki, ip: 192.168.122.105 }
        - { hostname: redmine, ip: 192.168.122.106 }

    tasks:
    - name: Install bind and bind-utils package
      yum: name="{{item}}" state=present
      with_items:
        - bind
        - bind-utils

    - name: Create custom named.conf with desired zone
      template: src=named.conf dest=/etc/named.conf owner=root group=named mode=640
      notify:
        - restart bind

    - name: Copy zone forward files for all zones to /var/named
      template: src="zone.forward" dest="/var/named/{{item}}forward" owner=root group=named mode=640
      with_items: zone_names
      notify:
        - restart bind

    - name: Disable IPv6 support
      lineinfile: dest=/etc/sysconfig/named line='OPTIONS="-4"' regexp="^OPTIONS" 
      notify:
        - restart bind

    - name: Start and enable bind service
      service: name=named state=started enabled=yes

    - name: Configure strong firewall on bind/named server
      template: src=named_iptables dest=/etc/sysconfig/iptables 
      notify:
        - restart iptables

    handlers:
    - name: restart bind
      service: name=named state=restarted

    - name: restart iptables
      service: name=iptables state=restarted
 

The playbook requires a named.conf template with following contents:

options {
	listen-on port 53 { 127.0.0.1; any; };
	listen-on-v6 port 53 { ::1; };
	directory 	"/var/named";
	dump-file 	"/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
	allow-query     { localhost; {{allow_query_from}} };
	recursion {{recursion}};

	dnssec-enable no;
	dnssec-validation no;
	dnssec-lookaside auto;

	/* Path to ISC DLV key */
	bindkeys-file "/etc/named.iscdlv.key";

	managed-keys-directory "/var/named/dynamic";
};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

{% for item in zone_names  %}

zone "{{item}}" IN {
   type master;
   file "{{item}}forward";
};

{% endfor %}


zone "." IN {
	type hint;
	file "named.ca";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

The playbook requires zone.forward file present in the same folder. The file should have following contents:

$TTL 3600 
@ SOA ns.{{item}} root.{{item}} (1 15m 5m 30d 1h) 
		IN	NS	{{name_server}}
		IN	A 	{{zone_address}}

{% for server1 in servers %}

{{server1.hostname}}	IN	A	{{server1.ip}}

{% endfor %}

Finally a named_iptables file with following contents should also be present:

*filter
:INPUT ACCEPT [-1:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
#Accept loopback connections
-A INPUT -i lo -d 127.0.0.0/8 -j ACCEPT
#Rate limit new connections to 20 new connections per 30 seconds
-A INPUT ! -p udp -m state --state NEW -m recent --name new_limit --set
-A INPUT ! -p udp -m state --state NEW -m recent --name new_limit --rcheck --seconds 30 --hitcount 20 -m limit --limit 2/min -j LOG --log-prefix "new_limit_"
-A INPUT ! -p udp -m state --state NEW -m recent --name ssh_limit --rcheck --seconds 30 --hitcount 20 -j DROP
#Accept ICMP ping requests at limited rate
-A INPUT -p icmp --icmp-type echo-request -m limit --limit 60/minute --limit-burst 120 -j ACCEPT
-A INPUT -p icmp --icmp-type echo-request -m limit --limit 1/minute --limit-burst 2 -j LOG
-A INPUT -p icmp --icmp-type echo-request -j DROP
#Allow ongoing connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
#Allow incoming SSH connections
-A INPUT -m state --state NEW -p tcp -m tcp --dport 22 -j ACCEPT
#Allow access to DNS from everywhere.  The allow_query option in DNS will take care of limiting clients. 
-A INPUT -m state --state NEW -p udp -m udp --dport 53 -j ACCEPT
#Log all other "blocked_input_" attempts with rate limiting
-A INPUT -m state --state NEW -m limit --limit 2/min -j LOG --log-prefix "blocked_input_"
#Reply with proper ICMP error message and reject the connection
-A INPUT -j REJECT --reject-with icmp-host-prohibited
#Disable packet forwarding through firewall
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
#
#
##Output rules
#Allow outgoing connections to localhost
-A OUTPUT -s 127.0.0.0/8 -o lo -j ACCEPT
#Allow ongoing connections
-A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
#Allow DNS queries
-A OUTPUT -p udp -m udp --dport 53 -j ACCEPT
#Allow server to send emails.  Required for sending logwatch emails
-A OUTPUT -p tcp -m tcp --dport 25 -j ACCEPT
#Allow server to contact web-servers.  Required for yum update and installation
#For restrictive configurations this can be disabled after install
-A OUTPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 443 -j ACCEPT
#Allow outgoing ping requests
-A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT
#Log all other "blocked_output_" attempts
-A OUTPUT -m state --state NEW -m limit --limit 2/min -j LOG --log-prefix "blocked_output_"
#Reply with proper ICMP error message and reject the connection
-A OUTPUT -j REJECT --reject-with icmp-host-prohibited
COMMIT
#

Ansible named-server role for both public and private DNS

For automated bind configuration for multiple DNS using same role refer to Ansible named-server role for both public and private DNS

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