Cloudflare Workers: block proxy IPs

Aworker.js

// Using a global variable so we aren't
// pulling from the proxy API on each 
// and every subsequent request
// (note that the Workers billing still applies here)
//
// This could be "truly global" with KV but 
// it's not really needed here unless the proxy list
// starts blocking CF ips.
// 
// 
var ips = [];

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

/**
 * Fetch and log a given request object
 * @param {Request} request
 */
async function handleRequest(request) {
  // check if the IP list is already populated
  if(this.ips.length == 0) {
    try {
      const proxyResponse = await fetch("https://www.proxy-list.download/api/v0/get?l=en&t=https")
      const proxyJson = await proxyResponse.json()
      proxyJson[0]["LISTA"].forEach(proxyItem => {
        this.ips.push(proxyItem["IP"])
      })
    }
    catch(err) {
      // don't break requsts if there is an error with
      // the json or request failing 
      console.log(err)
    }
  }
  if(this.ips.includes(request.headers.get("CF-Connecting-IP"))) {
    // feel free to customize this
    // you may want to error 400 or 401. 
    return new Response("An unknown error occured", {status: 500, statusText: "Internal Server Error"})
  }
  const response = await fetch(request)
  return response
}

LICENSE.md

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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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