How to test if Rails rack-cors gem is working

Question

I am trying to build a React - Rails API project. I added gem 'rack-cors' and created the config/initializers/cors.rb file:

Rails.application.config.middleware.insert_before 0, Rack::Cors do
    allow do
      origins "http://localhost:3001" 
      # The React part will be on port 3001 so thats way we add it
      # Change it to the production url when going on production
  
      resource "*",
        headers: :any,
        methods: [:get, :post, :put, :patch, :delete, :options, :head]
    end
end

I would only like to allow the port 3001 since thats the port my React front-end will be served at. Now I would like to test if this is actually working and blocking other requests.

Up until now, I have been using Postman to test the API (had to download it to work with http). I thought that because I added the filter to only a specific port, it would block the requests from Postman but it is still showing the data requested in the API call.

Also if I try reaching it like this on the browser:

http://localhost:3000/api/v1/users

It is still giving the data, which should be blocked to every port except 3001.

Why is it happening? Is there any other way to double check if it is working? NOTE: I killed the server and restarted it again and it is still behaving the same

Answer 1

To test CORS locally, I found this repo: https://github.com/njgibbon/nicks-cors-test

Just clone it, and click on the html file so it opens in your browser. By default it is calling the github API (https://api.github.com) and fetching info from there. You can open the console and check it. If you change it to https://google.com it will throw a CORS restriction.

Similarly, you can change it to http://localhost:3000/api/v1/users (in my case) and it will throw a CORS error with the config I have now.

To double-check, just go to cors.rb and put origins "*". Restart the app server and try running again the html file. Now we won't be blocked.

Answer 2

Make an API call from browser (Not from URL and Not from postman). May be through ajax to test.

Postman does not implement the CORS restrictions

Answer 3

just solved it by adding
gem 'rack-cors', require: 'rack/cors' after adding the require bit it worked

Answer 4

try this

curl -I -X OPTIONS \
  -H "Origin: https://ORIGIN.com" \
  -H 'Access-Control-Request-Method: POST' \
  "https://URL_YOU_WANT_TO_TEST" 2>&1 | grep -i 'Access-Control-Allow-Origin'

if it returns https://ORIGIN.com , it works.