A workaround for https://github.com/strapi/strapi/issues/13209

http-proxy-workaround.js

#!/usr/bin/env node

// This script allows you to forward http requests to a http proxy. There might not seem like much point to
// a proxy to another proxy but requests to a standard http proxy must be in a certain format. Strapi
// doesn't currently support this so we can use this proxy to forward requests in a format that Strapi
// is capable of sending.
// Requests can be made http://localhost:<port used by this script>/<full url include domain of the target page>
// For example if you start this script with the port 8080 and you ultimately want send a request to 
// https://www.infoxchange.org/au/about-us you would send the request to 
// http://localhost:8080/https://www.infoxchange.org/au/about-us

const http = require("http")
const httpProxy = require("http-proxy")
const URL = require("url").URL;

const args = process.argv.slice(2)

const port = getPortFromArgs('port')
const mockProxyServerPort = getPortFromArgs('mock-proxy-server-port')

const proxyServerUrl = !mockProxyServerPort
  ? process.env.HTTP_PROXY
  : `http://localhost:${mockProxyServerPort}`

if (!port) {
  console.error('Please provide the port to use as a cli flag in the form of: --port=<port>')
  process.exit(1)
}

if (!proxyServerUrl) {
  console.error('Please set the HTTP_PROXY env var to provide URL of the proxy server to forward requests.')
  process.exit(1)
}

function getPortFromArgs(cliFlag) {
  const portArg = args.find(arg => arg.startsWith(`--${cliFlag}=`))
  let port = null
  if (portArg) {
    const [, strPort] = portArg.match(/=(\d+)$/)
    port = parseInt(strPort) || null
  }
  return port
}

const proxy = httpProxy.createProxyServer({});

const server = http.createServer(function (req, res) {
  req.url = req.url.replace(/^\//, '')
  try {
    new URL(req.url)
  } catch (error) {
    res.writeHead(400, { 'Content-Type': 'text/plain' });
    res.write('Invalid request: url should be in the form of <domain of proxy>/<domain of target site><path of target site>');
    res.end();
    return
  }

  proxy.web(
    req,
    res,
    {
      target: proxyServerUrl,
      toProxy: true,
      prependPath: false
    }
  );
})

proxy.on('proxyReq', function(proxyReq, req, res, options) {
  const reqUrl = new URL(req.url)
  proxyReq.setHeader('Host', reqUrl.host);
});

proxy.on('error', function (err, req, res) {
  res.writeHead(500, {
    'Content-Type': 'text/plain'
  });
 
  res.end('Error reaching HTTP_PROXY.');
});


console.log(`Proxy sever listening on port ${port} and sending to ${proxyServerUrl}`)
server.listen(port);

if (mockProxyServerPort) {
  startMockHttpProxy(mockProxyServerPort)
}

// This can be used for testing and will act as a standard http proxy
function startMockHttpProxy(port) {
  const proxy = httpProxy.createProxyServer({});
 
  const server = http.createServer(function(req, res) {
    const reqUrl = new URL(req.url)
    const domainToSendTo = `${reqUrl.protocol}//${reqUrl.host}`

    // req.url is the value used in the path of the http request.
    // Normally this would just be exactly that, a path. But requests
    // to http proxies have the domain of the target site prepending
    // this path. We don't have to worry about striping away the domain
    // when we forward this request to the target site since http-proxy
    // will do this for us so long as the `toProxy` isn't set to true.
    proxy.web(req, res, { target: domainToSendTo });
  });
  
  console.log(`Mock HTTP Proxy sever listening on port ${port}`)
  server.listen(port);
}