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ViewsHandle user session with access token + OAuth provider
I am building a web application with a basic client-server architecure. The frontend runs with react (nextjs) and the backend is on rails. However, the questions will be more about the flow of the authentication/authorization + session handling on the frontend.
I am using an Oauth provider to handle the authentication but don't need any authorization from their part as I don't need the resources of the oauth provider (ex. drive, calendar etc.)
For the authorization, as I want to access resources of my API, it's the API itself that handles authorization on any request made by the client (frontend) to the rails API.
Right now for the initial authentication this is the flow I'm using, Taken from https://blog.prototypr.io/how-to-build-google-login-into-a-react-app-and-node-express-api-821d049ee670 : 
Implementation details important for the following questions :
I am using JWTs as access token (those generated by my API) and I simply sign them using a secret key that's only available on my API so the access token is unreadable from the front end point of view.
On the frontend, it is a react app and I used the following package to handle the OAuth flow google-react-login
Information received, what to use from Google (OAuth provider) 1- I receive(amongst other things) an IdToken and an access token from Google. Also I'm apparently supposed to receive a refresh token (which I didn't see). For my use case, all I need is the idToken from Google is that right?
Revoking of a refresh token (logout), flow for a re-login?
2- From my understanding access tokens need to be short lived for security reasons. So I need to return a refresh token to my client app to be able to generate new access tokens frequently. However, once a refresh token hits its expriy time, do I need to log out the user and prompt him to re-login through Google and basically redo steps 1 through 5 (Please refer to Figure 1)?
How to maintain the session through the access token
3- From the frontend perspective, can I assume that simply having a refresh token means the user is logged in? Once the server revoke the access token and the refresh token that means the user is logged out and I need to ouput a view of the web application for an unauthenticated user? That means after every page reload I need to check for the presence of an access and refresh token?
Thank you
1 answers
Answer question0
I think you could improve your security and lower complexity by one thing - replace issuing of your own JWT tokes by a custom OAuth2 server. This OAuth2 server could use Google as an authentication provider. This way, your would not know about Google and it would just use your own OAuth2 server.
Then you can decide how to use it - whether the frontend will be the OAuth2 client or the backend.
If you choose the frontend, you will use the auth code flow with PKCE (as a public client). The fronend will use an access_token to authorize its requests to the backend. This way, the frontend will handle a session using hidden iframes. See the OpenID Connect Session Management RFC.
If you choose the backend, you will use the auth code flow (with a client secret). This way, your backend can maintain the session using a cookie (with secure, HTTP-only, SameSite options).
You can read the OAuth 2.0 for Browser-Based Apps RFC for the current best practices.