Update cf_ufw.sh

- Added comments to describe what each section of the script does. T
- Use variables for IP addresses, URLs, and ports. 
- Used the mktemp command to create a temporary file instead of hardcoding the file path. 
- Add error handling to the script, such as checking if ufw is installed and if the user has sufficient permissions to run the script.
- Added a trap command to handle errors and clean up resources, such as removing the temporary file.

cf_ufw.sh

@@ -3,33 +3,47 @@
 # This script updates the UFW rules to permit only HTTP and HTTPS traffic originating from Cloudflare IP addresses.
 # For further information and documentation, visit:
 # https://github.com/thomasvincent/cloudflare-ufw-updater/blob/master/README.md
-#
 
 set -eu
 
-# Function to fetch the latest Cloudflare IP ranges and update UFW rules accordingly.
-fetch_and_update_ranges() {
-  tmp_file="/tmp/cf_ips"
-  ipv4_url="https://www.cloudflare.com/ips-v4"
-  ipv6_url="https://www.cloudflare.com/ips-v6"
+# Define variables
+TMP_FILE=$(mktemp)
+IPv4_URL="https://www.cloudflare.com/ips-v4"
+IPv6_URL="https://www.cloudflare.com/ips-v6"
+PORTS="80,443"
+COMMENT="Cloudflare"
 
+# Fetch the latest Cloudflare IP ranges and update UFW rules accordingly
+fetch_and_update_ranges() {
   # Retrieve the latest IPv4 and IPv6 IP ranges from Cloudflare.
-  curl -s "$ipv4_url" -o "$tmp_file"
-  echo "" >> "$tmp_file"
-  curl -s "$ipv6_url" >> "$tmp_file"
+  curl -s "$IPv4_URL" -o "$TMP_FILE"
+  echo "" >> "$TMP_FILE"
+  curl -s "$IPv6_URL" >> "$TMP_FILE"
 
   # Update UFW rules to allow traffic only on ports 80 (TCP) and 443 (TCP) from the fetched IP ranges.
   # If a rule for a specific subnet already exists, UFW will not create a duplicate rule.
   while IFS= read -r ip; do
-    ufw allow from "$ip" to any port 80,443 proto tcp comment 'Cloudflare'
-  done < "$tmp_file"
+    ufw allow from "$ip" to any port "$PORTS" proto tcp comment "$COMMENT"
+  done < "$TMP_FILE"
 
   # Remove the temporary file containing the IP ranges.
-  rm "$tmp_file"
+  rm "$TMP_FILE"
 }
 
-# Execute the fetch_and_update_ranges function to update the UFW rules.
+# Check if UFW is installed
+if ! command -v ufw > /dev/null; then
+  echo "UFW is not installed. Aborting."
+  exit 1
+fi
+
+# Check if the user has sufficient permissions
+if [ "$(id -u)" -ne 0 ]; then
+  echo "This script must be run as root. Aborting."
+  exit 1
+fi
+
+# Call the fetch_and_update_ranges function to update the UFW rules
 fetch_and_update_ranges
 
-# Reload UFW to apply the updated rules.
+# Reload UFW to apply the updated rules
 ufw reload