From 341738e850f1514a164ce37df9dabd855d34a4c8 Mon Sep 17 00:00:00 2001
From: Alexandre CATTEAU <alexandre.catteau@gmail.com>
Date: Fri, 11 Feb 2022 20:24:15 +0100
Subject: [PATCH] Initial commit

---
 .gitignore                           |  2 ++
 README.md                            | 25 ++++++++++++++
 install.sh                           | 15 +++++++++
 main.sh                              | 49 ++++++++++++++++++++++++++++
 systemd-templates/dns-update.service |  6 ++++
 systemd-templates/dns-update.timer   |  9 +++++
 variables.conf.template              |  7 ++++
 7 files changed, 113 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 README.md
 create mode 100644 install.sh
 create mode 100755 main.sh
 create mode 100644 systemd-templates/dns-update.service
 create mode 100644 systemd-templates/dns-update.timer
 create mode 100644 variables.conf.template

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c9242e7
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+variables.conf
+*.key
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c02edd0
--- /dev/null
+++ b/README.md
@@ -0,0 +1,25 @@
+# DNS update script
+
+Source: http://www.btteknik.net/?p=143
+
+### DNSSEC key
+* need to create a dnssec key, so that we can authenticate clients' updates
+```
+# ddns-confgen -s myhost.example.com
+```
+* this key must be:
+  * added to DNS server's `named.conf` and associated to required zones
+  * stored in a text file in the same directory as the script as `dns.key`
+
+### Install script
+You may run `install.sh` (not as root, it includes `sudo`s) to:
+* copy Systemd units templates to system directory
+* enable timer for next reboot
+* NOTE: if you move the script, you need to install again
+
+### Issues
+
+#### Cannot restrict PTR update
+* We meet an issue when trying to use `tcp-self` in BIND9 zone config
+* https://superuser.com/questions/977132/when-using-nsupdate-to-update-both-a-and-ptr-records-why-do-i-get-update-faile
+* http://www.zytrax.com/books/dns/ch7/xfer.html#update-policy
diff --git a/install.sh b/install.sh
new file mode 100644
index 0000000..063bfaa
--- /dev/null
+++ b/install.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+echo "Copying Systemd units to system directory..."
+sudo cp systemd-templates/dns-update.service /etc/systemd/system/
+sudo cp systemd-templates/dns-update.timer /etc/systemd/system/
+sudo sed -i -e "s/PH_USER/$(whoami)/g" /etc/systemd/system/dns-update.service
+sudo sed -i -e "s/PH_DIRECTORY/$(pwd)/g" /etc/systemd/system/dns-update.service
+
+echo "Reloading Systemd..."
+sudo systemctl daemon-reload
+echo "Enabling timer (not starting it, either do it manually or reboot)"
+sudo systemctl enable dns-update.timer
+
+echo "Finished install. Exiting..."
+exit 0
diff --git a/main.sh b/main.sh
new file mode 100755
index 0000000..89f173d
--- /dev/null
+++ b/main.sh
@@ -0,0 +1,49 @@
+#!/bin/bash
+
+source variables.conf
+
+KEY="$(pwd)/dns.key"
+TTL=604800
+
+FQDN=$(hostname)
+MYIP=$(ip route get 8.8.8.8 | grep -oP 'src \K[^ ]+')
+MYNUMBER=$(echo $MYIP | cut -d '.' -f 4) # last byte of IP
+#MYIP=$(dig +short myip.opendns.com @resolver1.opendns.com)
+
+# if $MYIP is not a valid IP, exit
+if [[ ! "$MYIP" =~ ^([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$ ]]; then
+  echo "Invalid IP, aborting"
+  exit 1
+fi
+
+# fetch current record with dig, and choose what to do
+current_ip_record=$(dig $FQDN +short)
+if [[ "$current_ip_record" =~ ^([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$ ]]; then
+  if [[ ! "$MYIP" = "$current_ip_record" ]]; then
+    echo "Updating record"
+  else
+    echo "Record is already up to date, exiting."
+    exit 0
+  fi
+else
+  echo "Server unreachable or no record for $FQDN, exiting."
+  exit 0
+fi
+
+nsupdate -k $KEY -v << EOF
+server $NS
+zone $MAINZONE
+update delete $FQDN. A
+update add $FQDN. $TTL A $MYIP
+send
+EOF
+
+nsupdate -k $KEY -v << EOF
+server $NS
+zone $REVERSEZONE
+update delete $MYNUMBER.$REVERSEZONE PTR
+update add $MYNUMBER.$REVERSEZONE $TTL PTR $FQDN.
+send
+EOF
+
+exit 0
diff --git a/systemd-templates/dns-update.service b/systemd-templates/dns-update.service
new file mode 100644
index 0000000..2cbb707
--- /dev/null
+++ b/systemd-templates/dns-update.service
@@ -0,0 +1,6 @@
+[Unit]
+Description=Update (if needed) name server with our IP
+
+[Service]
+User=PH_USER
+ExecStart=PH_DIRECTORY/main.sh
diff --git a/systemd-templates/dns-update.timer b/systemd-templates/dns-update.timer
new file mode 100644
index 0000000..d8eb1f2
--- /dev/null
+++ b/systemd-templates/dns-update.timer
@@ -0,0 +1,9 @@
+[Unit]
+Description=Run DNS update every 30 minutes
+
+[Timer]
+OnBootSec=1min
+OnUnitActiveSec=30min
+
+[Install]
+WantedBy=timers.target
diff --git a/variables.conf.template b/variables.conf.template
new file mode 100644
index 0000000..d9c9d1f
--- /dev/null
+++ b/variables.conf.template
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Copy this file as variables.conf, with the correct values
+
+NS=dns1.example.com
+MAINZONE=example.com.
+REVERSEZONE=1.168.192.in-addr.arpa.