Example is taken and adapted from the node-oidc-provider GitHub repository.

Setup

Server

Do a npm install. Install mongodb (or change to a different adapter) and set that up.

In support/configuration.js we need to create a new client:

    {
      client_id: 'f0fd57814c6670254e65510947a06656da6c5b299e98793b8cf1fe095461d9cd',
      client_secret: '26df92eef53fd8cf4554490b81090df591f16738891a2b8cd70bee1b58644385',
      grant_types: ['refresh_token', 'authorization_code'],
      redirect_uris: ['https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID', 'https://oauth-redirect-sandbox.googleusercontent.com/r/YOUR_PROJECT_ID'],
    }

The CLIENT_ID and CLIENT_SECRET you generate yourself. They can be any string, above strings were generated with nodejs require(crypto).randomBytes(32).toString('hex').

For redirect_uris the documentation is here. Specifically point 4:

Confirm that the URL specified by the redirect_uri parameter has the following form:

https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID
https://oauth-redirect-sandbox.googleusercontent.com/r/YOUR_PROJECT_ID

You get the PROJECT_ID from your Google Actions Console, open the project you want and copy the PROJECT_ID from the url.

    https://console.actions.google.com/u/0/project/newagent-xxxxxx/overview
                                                   ^^^^^^^^^^^^^^^

For above example YOUR_PROJECT_ID would be newagent-xxxxxx.

Starting the server

If using MongoDB, start the server with MONGODB_URI=mongodb://localhost/<database-name> PORT=3000 npm start.

Console

Make sure the action you create on the Google Actions Console is of the type "Smart Home".

Account linking

Provide your CLIENT_ID and CLIENT_SECRET in their respective fields.

Authorization url is https://<url-to-server>/auth.

Token url is https://<url-to-server>/token.

Under Configure your client (optional) add the scope profile. If no scopes are provided all requests will fail with access_denied.

Actions

Fill in fulfillment URL: https://<url-to-server>/fulfillment

Testing

Testing needs to be done on your android device:

1. Download Google Home app.
2. In the app click on the + in the top left corner
3. Select Set up device
4. Select Works with Google
5. In the top right corner click on search and search for [test]
6. Select [test] <project-name>
7. The OAuth2 process will now begin. For login provide any username and password (the values are discarded and a "default" user is returned).
8. Once the OAuth2 process is done a request to POST /fulfillment will be received.

If you can't see [test] <project-name>, try going to the Test tab on your Google console and clicking on "Talk to Test", the request will fail. Refresh the list on your device. The project should now be visible, if it is not, good luck. lol