Python code for generating signed urls for Cloudflare Image API

gen_signed_cf_image_url.py

import time
import hmac
import hashlib
from urllib.parse import urlparse, parse_qs, urlencode, urlunparse

# Given test private URL for private image we need to sign
KEY = 'KEY-FROM-CF-IMAGE-DAHSBOARD'
PRIVATE_URL = 'https://imagedelivery.net/abc123/abc123/public'
EXPIRATION = 60 * 60 * 24  # 24 hours in seconds

def buffer_to_hex(buffer):
    return ''.join(format(x, '02x') for x in buffer)

def generate_signed_url(url):
    url = urlparse(url)

    # Attach expiration time to the url
    expiry = int(time.time()) + EXPIRATION
    query = dict(parse_qs(url.query))
    query.update({'exp': expiry})
    
    string_to_sign = url.path + '?' + urlencode(query, doseq=True)
    print("signing string: " + string_to_sign)

    # Generate the signature
    mac = hmac.new(KEY.encode(), string_to_sign.encode(), hashlib.sha256)
    sig = buffer_to_hex(mac.digest())

    # Attach it to the `url`
    query.update({'sig': sig})
    url = url._replace(query=urlencode(query, doseq=True))
    return urlunparse(url)

def fetch_image_delivery_url(event_request_url):
    url = urlparse(event_request_url)
    image_delivery_url = url.path[1:].replace(
        'https:/imagedelivery.net', 'https://imagedelivery.net')

    return generate_signed_url(event_request_url)

# Test it with a URL
signed_url = fetch_image_delivery_url(PRIVATE_URL)

print(signed_url)