How to use Omniauth Asana with Rails API only app - ruby-on-rails

Question

I have a Rails 5 API only app and an Angular JS Frontend app and would like to integrate with Asana API. I'm using the ruby-asana, omniauth and omniauth-asana gems.
I start the request using Asana's JS library like so:
var client = Asana.Client.create({
clientId: 172706773623703,
clientSecret: '<client_secret>',
redirectUri: '<redirect_url>'
});
client.useOauth({
flowType: Asana.auth.PopFlow
});
And the above does redirect me to Asana where I can login. On the redirectUri I'm giving a backend route (Rails 5 API only) which should handle the remaining on the authentication (using the JS only I get only a temporary token that cannot be self renewed meaning the user will have to authenticate every time the token expires. This is if I understood the documentation correctly).
So, on the controller I've created to handle the route, I have the following (from an example on Asana's documentation):
require 'omniauth-asana'
use OmniAuth::Strategies::Asana, <secret>, <secret>
creds = request.env["omniauth.auth"]["credentials"].tap { |h| h.delete('expires') }
strategy = request.env["omniauth.strategy"]
access_token = OAuth2::AccessToken.from_hash(strategy.client, creds).refresh!
$client = Asana::Client.new do |c|
c.authentication :oauth2, access_token
end
Now, the above doesn't work because 1) there's no request.env as this is an API only app, so I've followed the instruction on Omniauth and have added the following to my config/application.rb:
config.session_store :cookie_store, key: '_interslice_session'
config.middleware.use ActionDispatch::Cookies # Required for all session management
config.middleware.use ActionDispatch::Session::CookieStore, config.session_options
Now, in the request.headers I have _interslice_session which has some numbers. How can I create a Asana client with the above?
Any ideas?

Answer 1

OK, I think I see what you're attempting to do here; I think the best way forward is to start with how OAuth's Authorization Code Grant happens in general, then move into specifics for OmniAuth.
You send the user to a URL that Asana owns; that is, your goal is to get the user to visit a particular url. For Asana, this is https://app.asana.com/-/oauth_authorize. (Note that we respond with an error if you don't sent a correct client_id param, but feel free to check that link if you want). Do not send the client_secret during this request - it is intended to never be involved in client-side code, as this is insecure.
If they agree to give access, Asana sends back a redirect request to the user's browser with a short-lived code. That then means that your server will be called from the user's browser with this code as a parameter, so has to handle a new incoming request from the browser to whatever you specified as your redirect URI. Also, this location must be accessible by all users of your integration wherever they are.
You send this code from your server as a POST request to https://app.asana.com/-/oauth_token with your client_secret to Asana for a refresh token. This is where your application actually asks for credentials; the token given in the previous phases simply acknowledges that for a short time, the user has given your app permission to ask for these credentials, and your client_secret assures Asana that, for this server-side request, your app really is yours (it's like your application's password).
We send back an access_token which represents (approximately) a client-user credential pair that is valid for an hour.
You use these credentials to access our API on behalf of this user. We also send back a refresh_token which is long-lived, and used to get new short-lived access_tokens after they expire in a very similar way.
OK, so how this works with OmniAuth if I grok it correctly is that it expects to handle almost all of it. I'll be working through our omniauth example in our ruby-asana client library here: https://github.com/Asana/ruby-asana/blob/master/examples/omniauth_integration.rb
You set up OmniAuth with your client id and client secret
use OmniAuth::Strategies::Asana, <client_id>, <client_secret>
A request comes in, and you don't have credentials for it.
get '/' do
if $client
...
else
'sign in to asana'
end
end
The user clicks the sign in link, which (code omitted) sends them to the sign_in endpoint. This endpoint issues a redirect to /auth/asana
The browser requests /auth/asana from our server. If you look at that example, it's not implemented in our code. That's because the /auth/:provider is magically handled by OmniAuth.
This is where all the magic happens. OmniAuth handles the entire login flow above: send browser to our oauth_authorize above, then receive the callback and sticks the relevant params in the environment such that it knows "we just got the short lived code". By the time these lines get hit:
creds = request.env["omniauth.auth"]["credentials"].tap { |h| h.delete('expires') }
strategy = request.env["omniauth.strategy"]
you are inside a callback that OmniAuth has intercepted, gotten the needed creds, and set the creds in the environment. You shouldn't have to handle the oauth callback and token exchange manually.
Now, with the code you provided, I notice a few things right off:
You are causing the popup cycle to happen client side. It may be (and I strongly suspect) that this won't work with OmniAuth - it expects to handle the whole OAuth flow.
Based on the code snippet you provided, you aren't serving this out of a request-response cycle in the controller, rather, it appears that this is in the controller body and not out of an instance method. It may be a typo, but this needs to be in a method that is called back to outside of Rails (that is, a route must point to this a controller method that Asana can use to handle the browser request).
You shouldn't have to look at request.headers, I think - I'm not sure what the issues might be with request.env, but I suspect they may be unrelated to the API-only nature of your app. Are you sure that this is because it's API-only? After adding in the middleware, did you double-check that you can't access request.env? My hunch would be that persistent data in request.env will still be there, only it would require on the middleware being added in to do this. The instructions on OmniAuth simply say that you need to have a session store for your API - which makes sense to me, because APIs don't necessarily need to store state across requests, OmniAuth is telling you to put a session store back in.
I know this is a lot of info, but hopefully it helps you get on the right track. Cheers!