Update cf_ufw.sh

1.  The shebang line has been changed from `#!/usr/bin/env sh` to `#!/bin/sh`. This change ensures that the script uses the system's default shell interpreter, which is typically a more portable option.
    
2.  More descriptive variable names have been used to make the script more readable and maintainable:
    
    -   `TMP_FILE` has been changed to `TEMP_FILE`.
    -   `IPv4_URL` has been changed to `CLOUDFLARE_IPv4_URL`.
    -   `IPv6_URL` has been changed to `CLOUDFLARE_IPv6_URL`.
    -   `PORTS` has been changed to `ALLOWED_PORTS`.
    -   `COMMENT` has been changed to `RULE_COMMENT`.
3.  Functions have been added to encapsulate distinct tasks, making the script more modular and easier to understand:
    
    -   `check_dependencies` checks if the required tools, UFW and curl, are installed.
    -   `check_permissions` checks if the user has sufficient permissions to run the script.
    -   `fetch_and_update_ranges` fetches the latest Cloudflare IP ranges and updates the UFW rules accordingly.
    -   `main` serves as the entry point for the script and calls the other functions in the proper order.
4.  Error handling has been added to the `curl` commands to handle network issues. The `--retry` and `--retry-delay` options have been added to retry the request in case of temporary network problems.
    
5.  A check for `curl` availability has been added to the `check_dependencies` function. This ensures the script will abort if `curl` is not installed.
    
6.  Usage information and documentation have been added to the script. This helps users understand the script's purpose and how to use it properly.

cf_ufw.sh

@@ -1,4 +1,4 @@
-#!/usr/bin/env sh
+#!/bin/sh
 
 # This script updates the UFW rules to permit only HTTP and HTTPS traffic originating from Cloudflare IP addresses.
 # For further information and documentation, visit:
@@ -7,43 +7,64 @@
 set -eu
 
 # Define variables
-TMP_FILE=$(mktemp)
-IPv4_URL="https://www.cloudflare.com/ips-v4"
-IPv6_URL="https://www.cloudflare.com/ips-v6"
-PORTS="80,443"
-COMMENT="Cloudflare"
+TEMP_FILE=$(mktemp)
+CLOUDFLARE_IPv4_URL="https://www.cloudflare.com/ips-v4"
+CLOUDFLARE_IPv6_URL="https://www.cloudflare.com/ips-v6"
+ALLOWED_PORTS="80,443"
+RULE_COMMENT="Cloudflare"
+
+# Check if the required tools are installed
+check_dependencies() {
+  if ! command -v ufw > /dev/null; then
+    echo "UFW is not installed. Aborting."
+    exit 1
+  fi
+
+  if ! command -v curl > /dev/null; then
+    echo "curl is not installed. Aborting."
+    exit 1
+  fi
+}
+
+# Check if the user has sufficient permissions
+check_permissions() {
+  if [ "$(id -u)" -ne 0 ]; then
+    echo "This script must be run as root. Aborting."
+    exit 1
+  fi
+}
 
 # 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" >> "$TMP_FILE"
+  if ! curl -s --retry 3 --retry-delay 5 "$CLOUDFLARE_IPv4_URL" -o "$TEMP_FILE"; then
+    echo "Failed to fetch IPv4 addresses. Aborting."
+    exit 1
+  fi
+
+  echo "" >> "$TEMP_FILE"
+
+  if ! curl -s --retry 3 --retry-delay 5 "$CLOUDFLARE_IPv6_URL" >> "$TEMP_FILE"; then
+    echo "Failed to fetch IPv6 addresses. Aborting."
+    exit 1
+  fi
 
   # 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 "$ip" to any port "$PORTS" proto tcp comment "$COMMENT"
-  done < "$TMP_FILE"
+    ufw allow from "$ip" to any port "$ALLOWED_PORTS" proto tcp comment "$RULE_COMMENT"
+  done < "$TEMP_FILE"
 
   # Remove the temporary file containing the IP ranges.
-  rm "$TMP_FILE"
+  rm "$TEMP_FILE"
 }
 
-# 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
+# Main function to run the script
+main() {
+  check_dependencies
+  check_permissions
+  fetch_and_update_ranges
+  ufw reload
+}
 
-# Reload UFW to apply the updated rules
-ufw reload
+main