Is it possible to use a Cloudflare Service Worker as a proxy web server?

Question

this is just a beginner level question looking for some advice, which the following may misuse some key terms as well because of lacking knowledge, but hopefully can deliver the key message to all of you:

Background:
my company is hosting a website in AWS, everything works fine except it cannot be loaded in China because of the well known Chinese Great Firewall that will block all unregistered/unlicensed websites outside of China; the best solution is perhaps to host a server in China and get an ICP license to be approved by the Chinese government, but that will take time and many other considerations. So we are now looking for some alternatives to let our customers from China able to read content from our site.

Main idea:
use a Cloudflare service worker to fetch HTTP resources from a given webpage first and then send the HTTP content to users by the Service Worker (since Cloudflare is accessible in China)

Example:
Let Cloudflare's registered Service Worker URL be: sample.workers.dev
Target website content to serve: google.com
When user tries to access this domain (sample.workers.dev), the service worker should try to load all HTTP content including images and scripts and css from google.com in backend, then return HTTP content to the users directly

This will work for my company's clients because we will usually generate a url and send over to the user by email or some other means, so we can send them a third party url that is accessible in China while actually loading content from our original website.

I tried all examples given by Cloudflare already: https://developers.cloudflare.com/workers/templates/ But so far no luck to archive what I want exactly.

Any thoughts?

Answer 1

yes, it's possible. i remember someone from Cloudflare implements it as an example.

Found it: https://github.com/lebinh/cloudflare-workers/blob/master/src/proxy.ts

However, Cloudflare workers does support streaming API now IIRC so there's a better way to do it.

/**
 * HTTP Proxy to arbitrary URL with Cloudflare Worker.
 */

/**
 * Cloudflare Worker entrypoint
 */
if (typeof addEventListener === 'function') {
    addEventListener('fetch', (e: Event): void => {
        // work around as strict typescript check doesn't allow e to be of type FetchEvent
        const fe = e as FetchEvent
        fe.respondWith(proxyRequest(fe.request))
    });
}

async function proxyRequest(r: Request): Promise<Response> {
    const url = new URL(r.url)
    const prefix = '/worker/proxy/'
    if (url.pathname.startsWith(prefix)) {
        const remainingUrl = url.pathname.replace(new RegExp('^' + prefix), '')
        let targetUrl = decodeURIComponent(remainingUrl)
        if (!targetUrl.startsWith('http://') && !targetUrl.startsWith('https://')) {
            targetUrl = url.protocol + '//' + targetUrl
        }
        return fetch(targetUrl)
    } else {
        return new Response('Bad Request', {status: 400, statusText: 'Bad Request'})
    }
}

interface FetchEvent extends Event {
    request: Request;

    respondWith(r: Promise<Response> | Response): Promise<Response>;
}