s3fetch

This Worker is adapted from the aws4fetch library. It aims to be the simplest possible solution for authenticating requests to S3 buckets from Cloudflare Workers using AWS Signature Version 4

Quickstart • Cache • Advanced

Supports

• Range requests
• Conditional requests (e.g. if-none-match)
• CORS preflight requests

---

Quickstart

1. Get your security credentials from AWS here: https://console.aws.amazon.com/iam/home?#/security_credentials. You'll need the access key ID and secret access key
2. Go to https://dash.cloudflare.com/workers/view, select Create a Worker and name it
3. Paste the contents of index.js in the Worker body, then press Save and Deploy. If you need to modify the behavior of fetch(), skip to the end of index.js
4. Press the back arrow and add the following environment variables (4 total): ACCESS_KEY_ID [🔒 Encrypt], SECRET_ACCESS_KEY [🔒 Encrypt], S3_BUCKET_NAME, and S3_REGION

For bucket name and region, here are three examples. In all cases - so long as the client requests /20806827090258869800702155681/IMG_8799.jpg - the signature will be valid:

# https://{BUCKET_NAME}.s3.{S3_REGION}.amazonaws.com/20806827090258869800702155681/IMG_8799.jpg
# https://s3-{S3_REGION}.amazonaws.com/{S3_BUCKET_NAME}/20806827090258869800702155681/IMG_8799.jpg
# https:/s3.{S3_REGION}.amazonaws.com/{S3_BUCKET_NAME}/20806827090258869800702155681/IMG_8799.jpg
# https://s3.amazonaws.com/{S3_BUCKET_NAME}/20806827090258869800702155681/IMG_8799.jpg (us-east-1 only)

5. When you're done, this is what your configuration should look like:
6. Finally, add a route under the zone/subdomain that you want to listen on for client requests, like https://api.cflr.example.com/* and apply the Worker you just created:

Cache

This Worker does not specify any cache settings. Please refer to Cloudflare's general cache documentation, the Cache API or the Advanced Configuration section below.

Advanced

Note: if you have a more complex workflows or need to sign requests for other AWS services, please use aws4fetch, from which this Worker is adapted.

/**
 * All examples should replace the default Worker method here:
 * https://github.com/shagamemnon/s3workers/blob/ad74086c7b4d36b75b86f881d20ee4278839d8ec/index.js#L257
 */



/** 
 * Example #1
 * Sign the request; don't specify any cache settings
 */
addEventListener('fetch', event => event.respondWith(handle(event.request)))
 
async function handle (request) {
  if (request.method === 'OPTIONS') {
    return new Response('', {
      headers: {
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Headers': 'Content-Type,Authorization',
        'Access-Control-Allow-Methods': 'GET,OPTIONS,POST',
        'Access-Control-Max-Age': 86400
      }
    })
  }
 
  let signedRequest = await AwsClient.sign(request)
 
  return fetch(signedRequest)
}
 



/** 
 * Example #2
 * Sign the request URL only
 * You can just pass the just the eyeball request URL for signing. Note that
 * most headers will be removed prior to the fetch() as AWS will only accept
 * headers that are ordered in a specific way.
 */
addEventListener('fetch', event => event.respondWith(handle(event.request)))
 
async function handle (request) {
  //..
  let signedRequest = await AwsClient.sign(request.url)
 
  return fetch(signedRequest)
}
 
 
 
 
/** 
 * Example #3
 * Cache subrequest using the cf options object
 */
addEventListener('fetch', event => event.respondWith(handle(event.request)))
 
async function handle (request) {
  //..
  let signedRequest = await AwsClient.sign(request.url)
 
  return fetch(signedRequest, {
    cf: {
      cacheTtl: 3600,
      cacheTtlByStatus: {
        "200-299": 86400,
        "404": 1,
        "500-599": 0
      },
      cacheKey: request.url.split('?').pop()
    }
  })
}