Negating Past Mistakes


    2.7.1 • Public • Published


    This is the software running on - 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 with added restrictions to reduce the opportunity to abuse the proxy. Namely, it blocks requests that don't look like valid git requests.


    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 start -d

    Kill the process with the PID specified in $PWD/

    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 = {}

    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.


        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


    This work is released under The MIT License




    npm i @isomorphic-git/cors-proxy

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