DIY RFC2136 dyndns with bind

This is an old revision of the document!

ever since dyndns stopped to be completely free (including hassle-free) i was looking for alternatives. i recently stumbled across RFC2136 which can be used to provide dynamic dns services. since i have access to two nameservers running bind i decided to try it out.. it works pretty nicely :)

there is a howto in the pfsense wiki, however, that did not work for me. i had to use allow-update reather than update-policy.. don't know why, somehow it just seemed to have been ignored by the version of bind9 i am running on the servers.

so here is how i did it: first of all i wanted to be able to have a simple script that would allow me to add new hosts with a minimum amount of work. so i split my config into different files, so i could later edit them automatically. also, you want to make sure the file where the keys are stored is not world readable..

create a directory that holds all the dynamic dns stuff:
```
mkdir /etc/bind/dyn
cd /etc/bind/dyn
```
create a basic zonefile for the dynamic dns zone. Important, you should use a dedicated subdomain with its own zone file for the dyndns stuff, as the zone file will be rewritten by bind later on and after that it is an absolute mess. so make sure you don't do this with your main zone file for your main domain! save the file as db.dyn.mydomain.ch in your dyn directory. here are the contents:
```
$ORIGIN .
$TTL 30	; 30 seconds
dyn.mydomain.ch		IN SOA	ns1.mydomain.ch. hostmaster.mydomain.ch. (
				2013102704 ; serial
				900        ; refresh (15 minutes)
				600        ; retry (10 minutes)
				2600       ; expire (43 minutes 20 seconds)
				30         ; minimum (30 seconds)
				)
			NS	ns1.mydomain.ch.
			NS	ns3.mydomain.ch.
```
create an empty keys.conf file
```
touch keys.conf
```

create a file named.conf with the following contents

include "/etc/bind/dyn/keys.conf";

zone "dyn.mydomain.ch" {
	type master; 
	file "/etc/bind/dyn/dyn.mydomain.ch"; 
	allow-update { 
		//add_keys_here//
	}; 
	allow-query { 
		ANY;
	}; 
};

note keep the add_keys_here comment exactly as it is, this is the marker for our script so it knows where to add new keys

edit your main named.conf file, usually in /etc/bind/named.conf and add an include line at the end of your zone definitions like so:
```
include "/etc/bind/dyn/named.conf";
```

create the “add_new_host.sh” script that will add new hosts to our setup. here are the contents of the script:

#!/bin/bash
if [ -z "$1" -o "$1" == " " ]; then
        echo "usage: add_new_host.sh <hostname>"
        echo "EXAMPLE: add_new_host.sh myhost will add myhost.dyn.mydomain.ch"
        exit 1
fi
cd /etc/bind/dyn/
mkdir tmp
cd tmp
hostname=${1}.dyn.mydomain.ch.
echo "generating key for ${hostname}"
keyfile=`dnssec-keygen -a HMAC-MD5 -b 128 -n HOST ${hostname}`
key=`grep "Key" ${keyfile}.private | awk '{ print $2; }'`
echo "here is the key i have generated, use this to configure your client: $key"
cd ..
rm -rf tmp
echo "adding key to named.conf..."
cat named.conf | sed -e "s/\/\/add_keys_here\/\//key ${hostname};\n\t\t\/\/add_keys_here\/\//" | tee named.conf > /dev/null
echo "key ${hostname} { algorithm hmac-md5; secret \"${key}\"; };" >> keys.conf
echo "done"
echo "reload bind";
/etc/init.d/bind9 reload
echo "currently active hosts:"
grep "key " named.conf | awk '{ print $2; }' | tr -d ";"