CORS Proxy

cors-proxy is a Cloudflare Worker for proxying CORS requests to resources that do not support CORS. It may also work with resources that do support CORS, but not for your origin. There are probably better, more technically correct solutions available -- this was a project to learn about Cloudflare and to be used with other pet projects.

Requirements

• Rust
• wasm-pack
• worker-build
• Node.js

Initial Setup and Deployment

The following steps are needed to deploy cors-proxy to Cloudflare.

1. Install dependencies.

   npm install
   

2. Login to Cloudflare

   npx wrangler login
   

3. Create a namespace and replace the current kv_namespaces in wrangler.toml with the output.

   npx wrangler kv:namespace create default
   

4. Create allowed_hostnames key. This key is a comma separated list of hostnames that are allowed to use the cors-proxy worker.

   npx wrangler kv:key put --preview false --binding default allowed_hostnames "localhost,some.example.com"
   

5. Publish to Cloudflare.

   npx wrangler publish
   

Development Setup

npm install

Optionally swap the command under [build] in wrangler.toml for better debugging.

Wrangler

You will need to create a preview version of the namespace and replace preview_id of kv_namespaces in wrangler.toml with the output.

npx wrangler kv:namespace create --preview default

Add a preview version of the allowed_hostnames key.

npx wrangler kv:key put --binding default --preview allowed_hostnames "localhost,some.example.com"

Run npx wrangler dev and it will build the project and allow you to preview it "locally". Remember that it is running on the Cloudflare servers and not your local machine.

Miniflare

Miniflare will run the worker on your local machine and it is built in to wrangler. Namespaces work differently with Miniflare. To update the allowed_hostnames key, modify .wrangler/state/kv/default/allowed_hostnames.

Then run miniflare.

npx wrangler dev --local --persist

Docker

A Docker image that hosts cors-proxy with miniflare is available.

docker container run --publish 8787:8787 --rm -i -t unixgeek2/cors-proxy

This is useful when working on an application that uses cors-proxy as it will save requests to your production deployed worker. It probably isn't useful outside that use case.

Resources

Cloudflare Workers
Cloudflare worker crate
Miniflare