@isomorphic-git/cors-proxy

This is the software running on https://cors.isomorphic-git.org/ - a free service (generously sponsored by Clever Cloud) for users of isomorphic-git that enables cloning and pushing repos in the browser.

It is derived from https://github.com/wmhilton/cors-buster with added restrictions to reduce the opportunity to abuse the proxy. Namely, it blocks requests that don't look like valid git requests.

Installation

npm install @isomorphic-git/cors-proxy

CLI usage

Start proxy on default port 9999:

cors-proxy start

Start proxy on a custom port:

cors-proxy start -p 9889

Start proxy in daemon mode. It will write the PID of the daemon process to $PWD/cors-proxy.pid:

cors-proxy start -d

Kill the process with the PID specified in $PWD/cors-proxy.pid:

cors-proxy stop

CLI configuration

Environment variables:

• PORT the port to listen to (if run with npm start)
• ALLOW_ORIGIN the value for the 'Access-Control-Allow-Origin' CORS header
• INSECURE_HTTP_ORIGINS comma separated list of origins for which HTTP should be used instead of HTTPS (added to make developing against locally running git servers easier)

Middleware usage

You can also use the cors-proxy as a middleware in your own server.

const express = require('express')
const corsProxy = require('@isomorphic-git/cors-proxy/middleware.js')

const app = express()
const options = {}

app.use(corsProxy(options))

Middleware configuration

The middleware doesn't use the environment variables. The options object supports the following properties:

• origin: string. The value for the 'Access-Control-Allow-Origin' CORS header
• insecure_origins: string[]. Array of origins for which HTTP should be used instead of HTTPS (added to make developing against locally running git servers easier)
• authorization: (req, res, next) => void. A middleware function you can use to handle custom authorization. Is run after filtering for git-like requests and handling CORS but before the request is proxied.

Example:

app.use(
  corsProxy({
    authorization: (req: Request, res: Response, next: NextFunction) => {
      // proxied git HTTP requests already use the Authorization header for git credentials,
      // so their [Company] credentials are inserted in the X-Authorization header instead.
      if (getAuthorizedUser(req, 'X-Authorization')) {
        return next();
      } else {
        return res.status(401).send("Unable to authenticate you with [Company]'s git proxy");
      }
    },
  })
);

// Only requests with a valid JSON Web Token will be proxied
function getAuthorizedUser(req: Request, header: string = 'Authorization') {
  const Authorization = req.get(header);

  if (Authorization) {
    const token = Authorization.replace('Bearer ', '');
    try {
      const verifiedToken = verify(token, env.APP_SECRET) as IToken;
      if (verifiedToken) {
        return {
          id: verifiedToken.userId,
        };
      }
    } catch (e) {
      // noop
    }
  }
}

License

This work is released under The MIT License