# Converting a Rails App: Omniath CAS
**URL:** https://discourse.hanakai.org/t/converting-a-rails-app-omniath-cas/1276
**Category:** sharing
**Created:** [July 14, 2025, 8:45pm UTC](https://discourse.hanakai.org/t/converting-a-rails-app-omniath-cas/1276 "2025-07-14T20:45:29Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@carolync](https://discourse.hanakai.org/u/carolync)
#### Post date: [July 14, 2025, 8:45pm UTC](https://discourse.hanakai.org/t/converting-a-rails-app-omniath-cas/1276/1 "2025-07-14T20:45:29Z")
Configuring Devise with CAS in my Rails application was as simple as install the devise gem, running the generator and then adding `config.omniauth :cas, host: "...", url: "..."` to my [devise configuration](https://github.com/pulibrary/orcid_princeton/blob/97244c18a4e9e12fae31b4dd283fd769f0d4cd89/config/initializers/devise.rb#L292C3-L292C88). Then I had to implement a call back and I was “done”. Devise did most of the rest of the lift.
In Hanami I was still able to utilize the same Omniath cas gem. It took me a bit to figure out all the correct configuration, so I thought I would put it out here for other folks.
I had to configure the gem as middleware. I missed adding Warden first and it took me a bit to find the syntax to provide the provider variables.
```auto
# config/application.rb
config.middleware.use Warden::Manager
config.middleware.use OmniAuth::Builder do
provider :cas, host: Hanami.app.settings.cas_host, url: Hanami.app.settings.cas_url
end
```
I had to make sure to include my callback location (and service url) when I redirecting to the CAS server.
```auto
# app/actions/sessions/new
OmniAuth.strategies.first.configure(host: Hanami.app.settings.cas_host, url: Hanami.app.settings.cas_url)
omniauth_strategy = OmniAuth.strategies.first.new(Hanami.app)
service_url = omniauth_strategy.append_params(routes.url(:auth_callback, provider: 'cas'),
{ url: request.referer })
omniauth_strategy.login_url(service_url)
```
And then finally I got back the same token that I had in my rails application so I could parse it and know who is logged in. This code was copied directly from my rails application.
```auto
# app/actions/session/create
auth_hash = request.env['omniauth.auth']
user = user_repo.from_cas(auth_hash)
```
Next, I put the current\_user method in the base action and exposed it in the base view so I could show the logged in user in my main menu bar.
```auto
# app/action.rb
before :current_user
def current_user(request, response)
if request.env['warden']
response[:current_user] = user_repo.find_by_uid(request.env['warden'].user)
end
end
```
```auto
# app/view
expose :current_user, layout: true
```
I will also have to check that the user is present for each action that requires a login and redirect to my session/new action if needed, but accessing single sign on and knowing who is logged in was a huge step!
---
### Author:  [@carolync](https://discourse.hanakai.org/u/carolync)
#### Post date: [July 21, 2025, 5:28pm UTC](https://discourse.hanakai.org/t/converting-a-rails-app-omniath-cas/1276/2 "2025-07-21T17:28:56Z")
Hi All!
I realized I was missing some automation that Omniauth included in the above post.
If you add `get` to `allowed_request_methods` then Omniauth will intercept get requests to `/auth/cas` and you did not need the session.new action. session.new had some complex code I did not love and didn’t really want to maintain. Luckily for me it can be removed.
```auto
# config/app.rb
OmniAuth.config.allowed_request_methods = %i[get post]
```
All my login links then needed to link to `'auth/cas'` as the href location
```auto
<%= link_to("Log-in", '/auth/cas',id: "login-button", class: "button" %>
```
On a side note, I tried to utilize post and I got some browsers that redirected correctly and others that did not. Firefox was the one that redirected consistently and Chrome did not for the posts to /auth/cas. In the browsers that did not redirect it looked entirely like omniauth was doing nothing until I looked at the network traffic and saw the 301 response with the correct url.