Proxying to proxy ... how?

[InputOutput]

Expected behavior

I want to have requests between our middleware using Express & http-proxy-middleware to be proxied to another debugging proxy (in this case OWASP ZAP) to be able to easily debug the traffic between middleware and API.

Actual behavior

I am unable to find the correct setup to achieve this. I have activated the toProxy, xvfb and changeOrigin options but have no idea how to actually tell the proxy to proxy via OWASP.

Setup

• http-proxy-middleware: 0.17.4
• server: express 4.16.2
• other relevant modules

proxy middleware configuration

const proxyDefaults = {
    target: `${config.api.root}`,
    toProxy: true,
    xfwb: true,
    logLevel: config.loglevel.proxy,
    changeOrigin: true,
    secure: config.api.secure,
    pathRewrite: {
        '^/express': '/v2'
    },
    logProvider: function() {
        return logger;
    }
};

server mounting

router.all('*', authenticationMiddleware, proxy(Object.assign({}, injectAccessToken, proxyDefaults)));

app.use('/express', router);

[markbjerke]

I would settle for using Fiddler for monitoring the usage of this package. I agree with you there doesn't seem to be enough config since the toProxy is a boolean?

[AlbinoDrought]

Here's what I used to forward to OWASP ZAP, using the http-proxy-agent package (also see node-proxy-agent for SOCKS, PAC, HTTPS proxy support). I didn't actually need the toProxy option, not sure why, but I successfully see the requests in ZAP anyways.

const express = require('express');
const proxy = require('http-proxy-middleware');
const ProxyAgent = require('http-proxy-agent');

// proxy to chain through (OWASP ZAP)
const proxyUrl = 'http://127.0.0.1:8000';

const app = express();

app.use(proxy({
  agent: new ProxyAgent(proxyUrl),
  target: 'http://example.com/',
  changeOrigin: true,
}));

[aquillano]

@AlbinoDrought I tried your solution to proxy to mitmproxy, but it didn't work. I wonder what the difference is between ZAP ant mitmproxy?