A method for signing BunnyCDN URLS using Token Authentication

bunny-sign.ts

import { add } from "npm:date-fns";

/**
 * references
 *   - https://write.corbpie.com/how-to-do-token-authentication-urls-with-bunnycdn/
 *   - https://git.sr.ht/~jamesponddotco/bunnysign
 *   - https://bunny.net/blog/were-bringing-token-authentication-to-the-next-level/
 * 
 */

async function signUrl(url: string, securityKey: string): string {
  const parsedUrl = new URL(url);
  const expirationDate = add(new Date(), { weeks: 1 })
  const hashBase = securityKey + parsedUrl.pathname + expirationDate.getTime();
  const data = new TextEncoder().encode(hashBase);
  const hashBuffer = await crypto.subtle.digest('SHA-256', data);
  const hashArray = Array.from(new Uint8Array(hashBuffer));
  const hash = hashArray.map(byte => String.fromCharCode(byte)).join('');
  const b64 = btoa(hash);
  const formattedToken = b64.replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
  return `${url}?token=${formattedToken}&expires=${expirationDate.getTime()}`;
}


export async function main(
  url: string,
  securityKey: string
) {
  if (!url) throw new Error('url arg missing');
  if (!securityKey) throw new Error('securityKey arg missing');
  return await signUrl(url, securityKey);
}