twitter_auth

A library to add the Sign in with Twitter functionality to your Crystal web app, in a few lines of code.

Installation

1. Add the dependency to your shard.yml:

dependencies:
  twitter_auth:
    github: lbarasti/twitter_auth

2. Run shards install

Usage

Initializing a Twitter authorization client

Twitter apps are assigned a consumer key and a consumer secret. These are used to sign any request to the Twitter API. Here is how you create a Twitter authorization client:

require "twitter_auth"

auth_client = TwitterAPI.new(consumer_key, consumer_secret, callback_url)

Requesting an OAuth Request Token

When a user requests to sign in with Twitter, the first step for your app is to ask Twitter for an OAuth Requests Token.

request_token = auth_client.get_token

Your app will then redirect the user to a Twitter-owned login screen - TwitterAPI.authenticate_url(request_token) - where they can authorize your app to issue requests on their behalf.

Upgrading to an OAuth Access Token

After the sign-in, the user is redirected to your app via a whitelisted callback URL. With the parameters included in the request, your app can now upgrade the request token to an access one.

access_token = auth_client.upgrade_token(request_token, verifier)

Verifying a user's identity

Now that you have an OAuth Access Token, you can verify the identity of the user who signed in.

auth_client.verify(access_token)

When successful, this returns a String in JSON format, containing information about the user, e.g. user id, Twitter handle and description.

Invalidating an OAuth Access Token

By design, a Twitter user's access token never expires. Nonetheless, it's likely that your app will need to invalidate the access token at some point.

auth_client.invalidate_token(access_token)

This will require the user to authorize your app again, next time they try to sign in with Twitter.

---

For more info on the twitter_auth API you can browse the API docs pages.

3-legged OAuth flow

When a user clicks on the button your application will initiate a 3-legged OAuth flow.

For a minimal implementation, you just need to define the following endpoints.

get "/authenticate" do |ctx|
  request_token = auth_client.get_token.oauth_token
  <your-code-here> # store the request token for later verification in the /callback-url step
  ctx.redirect TwitterAPI.authenticate_url(request_token)
end

get "/callback-url" do |ctx|
  token = ctx.params.query["oauth_token"]
  <your-code-here> # verify that the token matches the request token stored in the step above
  verifier = ctx.params.query["oauth_verifier"]
  token, secret = auth_client.upgrade_token(token, verifier)
  <your-code-here> # store the access token and secret - to be used for future authenticated requests to the TwitterAPI
  ctx.redirect "/#some-token-here"
end

Remember to configure your Twitter app to whitelist the callback URL.

Demo

You can play with a demo of the example app on heroku.

FAQ

Why do I want this?

Your users will authenticate to your app via Twitter, so that your app does not have to deal with user management and forgotten passwords.

Is it authentication or authorization?

The OAuth flow lets the user authorize your app to read information about them, so that you can authenticate the user into your app.

Can I use my own HTTP client to issue calls to the Twitter API?

Yes, you can. Just subclass TwitterAPI and override the exec method.

Development

Running the tests

crystal spec

Running the example app

Before running the example app, make sure the following environment variables are defined consistently with your Twitter app settings - you can define a new Twitter app here:

TWITTER_CONSUMER_KEY
TWITTER_CONSUMER_SECRET
TWITTER_CALLBACK_URL

Mind that, in order to get the app to work locally, you'll need to have localhost:8090/your-callback-path in the app's callback URL list.

Next, run the following.

$ cd examples/kemal_integration
$ shards install
$ crystal src/server.cr

Now open your browser to http://0.0.0.0:8090 and follow your instinct 🚀

Contributing

1. Fork it (https://github.com/lbarasti/twitter_auth/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• lbarasti - creator and maintainer