Identify IP prefixes for the firewall allowlist

# Import required modules, functions or classes
from urllib.request import urlopen
import json
import re

# loads IP ranges defined in JSON format from url
ip_ranges = json.loads(urlopen('https://ip-ranges.amazonaws.com/ip-ranges.json').read())

# Option 1: All services
target_prefixes = [prefix['ip_prefix'] for prefix in ip_ranges['prefixes']]

# Option 2: Specific service only

# Filter by service name
# Service name must be modified respectively. Example: S3
target_prefixes = [prefix['ip_prefix'] for prefix in ip_ranges['prefixes'] if prefix['service'] == 'S3'] 

# Option 3: Specific service and region only

# Filter by service name and region
# Service name must be modified respectively. Example: S3
# Pattern to match region name must be modified respectively. 
# Example: eu-west.* for eu-west-1, eu-west-2, eu-west-3
pattern = r"eu-west.*"
target_prefixes = [prefix['ip_prefix'] for prefix in ip_ranges['prefixes'] if (prefix['service'] == 'S3' and re.match(pattern, prefix['region']))]

# Write to file
# Ensure correct path and filename in the open function parameter e.g. C:/data/amazonips.txt
with open('./amazonips.txt', 'w+') as f:
    f.write('\n'.join(target_prefixes))