Proxy on cloudflare workers

forward-proxy.js

// URI prefix
const token = TOKEN; // env, like 'https://<your worker domain>.workers.dev/'

const blocked_code = [
	'US', 'UK', 'CA', 'AU', 'RU', 'FR', 'DE'
];

const blocked_hosts = [
	'0.0.0.0',
	'127.0.0.1',
	'localhost'
];

addEventListener('fetch', event => {
	event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
	const region_code = request.headers.get('cf-ipcountry').toUpperCase();
	const ip_address = request.headers.get('cf-connecting-ip');

	if (blocked_code.includes(region_code)) {
		return new Response('Deny', { status: 403 });
	}
	if (! request.url.startsWith(token)) {
		return new Response('Bad request', { status: 400 });
	}

	let url = request.url.substr(token.length);
	try {
		url = new URL(url);
		if (blocked_hosts.includes(url.hostname))
			throw new Error('host is blocked');
	} catch (e) {
		return new Response('Bad request: ' + e.message, { status: 400 });
	}
	let reqhead = new Headers(request.headers);
	// discard real ip
	if (reqhead.has('x-real-ip')) reqhead.delete('x-real-ip');
	for (let [key, val] of reqhead) {
		if (key.startsWith('cf-') || key.startsWith('x-forwarded-'))
			reqhead.delete(key);
	}
	reqhead.set('Host', url.hostname);

	let response = await fetch(url.href, {
		method: request.method,
		headers: reqhead
	});
	return response;
}