From 4e12581deaa3a93b22e9b6ec73210e0f89ff007f Mon Sep 17 00:00:00 2001
From: Mike Heier <mike@heier.io>
Date: Wed, 13 Jul 2022 20:39:22 -0400
Subject: [PATCH] Created a script to keep Azure DNS pointed to the public IP

---
 .env-sample   |  9 +++++
 .gitignore    |  1 +
 update-dns.sh | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 102 insertions(+)
 create mode 100644 .env-sample
 create mode 100644 .gitignore
 create mode 100755 update-dns.sh

diff --git a/.env-sample b/.env-sample
new file mode 100644
index 0000000..7e349f4
--- /dev/null
+++ b/.env-sample
@@ -0,0 +1,9 @@
+SUBSCRIPTION_ID=<YOUR_SUBSCRIPTION_ID_GUID>
+CLIENT_ID=<YOUR_CLIENT_ID_GUID>
+CLIENT_SECRET=<YOUR_CLIENT_SECRET>
+TENANT_ID=<YOUR_TENANT_ID_GUID>
+
+RESOURCE_GROUP_NAME=<YOUR_RESOURCE_GROUP_NAME>
+ZONE_NAME=<YOUR_DNS_ZONE_NAME>
+RECORD_TYPE=A
+RELATIVE_RECORD_SET_NAME=@
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2eea525
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.env
\ No newline at end of file
diff --git a/update-dns.sh b/update-dns.sh
new file mode 100755
index 0000000..7c5ff7a
--- /dev/null
+++ b/update-dns.sh
@@ -0,0 +1,92 @@
+#!/usr/bin/env bash
+
+# set -x
+set -e
+
+#
+# Source the environment variables
+#
+if [[ ! -f .env ]]; then
+    echo "MISSING .env FILE!"
+    exit -1
+fi
+source .env
+
+# 
+# CURL to get the bearer token for the following calls
+#
+get_token() {
+    curl -s -X POST \
+        -d "grant_type=client_credentials&client_id=$CLIENT_ID&client_secret=$CLIENT_SECRET&resource=https%3A%2F%2Fmanagement.azure.com%2F" \
+        https://login.microsoftonline.com/9da185bf-c68b-4143-af97-f6744a41c9db/oauth2/token | jq --raw-output '.access_token'
+}
+
+#
+# CURL to get the recordset
+#
+get_recordset() {
+    curl -s -X GET \
+        -H "Authorization: Bearer $ACCESS_TOKEN" \
+        -H "Content-Type: application/json" \
+        https://management.azure.com/subscriptions/$SUBSCRIPTION_ID/resourceGroups/$RESOURCE_GROUP_NAME/providers/Microsoft.Network/dnsZones/$ZONE_NAME/$RECORD_TYPE/$RELATIVE_RECORD_SET_NAME?api-version=2018-05-01 \
+        | jq '.'
+}
+
+#
+# Parses the IPv4 IP Address from the Record Set response
+#
+get_recordset_address() {
+    get_recordset | jq --raw-output '.properties.ARecords[].ipv4Address'
+}
+
+#
+# Updates and formats the record set to be used in the PUT request body
+#
+update_recordset() {
+    echo $AZURE_RECORDSET | jq -r ".properties.ARecords[].ipv4Address = \"$1\" | del(.name,.type,.id,.properties.fqdn,.properties.provisioningState) | @text"
+}
+
+#
+# CURL to PUT the updated record set 
+#
+put_recordset() {
+    curl -s -X PUT \
+        -H "Authorization: Bearer $ACCESS_TOKEN" \
+        -H "Content-Type: application/json" \
+        --data-raw "$1" \
+        https://management.azure.com/subscriptions/$SUBSCRIPTION_ID/resourceGroups/$RESOURCE_GROUP_NAME/providers/Microsoft.Network/dnsZones/$ZONE_NAME/$RECORD_TYPE/$RELATIVE_RECORD_SET_NAME?api-version=2018-05-01
+}
+
+# Get an Accesss Token
+ACCESS_TOKEN=$(get_token)
+# echo $ACCESS_TOKEN
+
+# Get the Record Set
+AZURE_RECORDSET=$(get_recordset)
+echo "Azure Record Set: $AZURE_RECORDSET"
+
+# Parse the Record Set
+AZURE_IP_ADDRESS=$(get_recordset_address)
+echo "Azure IP: $AZURE_IP_ADDRESS"
+
+# Get the currently assigned Public IP
+ISP_IP_ADDRESS=$(dig +short myip.opendns.com @resolver1.opendns.com)
+echo "ISP IP: $ISP_IP_ADDRESS"
+
+# If the currently assigned public IP doesn't match the configured IP address in Azure...
+#  update the Azure record set.
+if [ $AZURE_IP_ADDRESS != $ISP_IP_ADDRESS ]; then
+    echo "IP ADDRESSES DON'T MATCH. UPDATING..."
+
+    # Prepare the request content
+    AZURE_RECORDSET_UPDATE=$(update_recordset $ISP_IP_ADDRESS)
+    echo $AZURE_RECORDSET_UPDATE
+
+    # Perform the Update
+    AZURE_PUT_RESPONSE=$(put_recordset $AZURE_RECORDSET_UPDATE)
+    echo "Azure PUT Response: $AZURE_PUT_RESPONSE"
+
+    echo "Azure IP Address updated successfully"
+else
+    echo "IP Address is up to date."
+fi
\ No newline at end of file