Use SpringSecurity's OAuth2 functionality on demand on custom endpoint

Question

We have a Spring Boot web app which uses JWT based authentication/authorisation. Now, we want to add OAuth2 support so that users can login using their Google account. That would be easy to do using Spring Security .

However, the requirement is a bit different.

If the user wants to use the Google login functionality, he first needs to link their Google account. Basically login into our application using his/her credentials, and on their profile page link their Google account.

The flow would be something like the following:

1. Click the “ Link Google account ” button on user's profile which redirects them to Google
2. In Google choose the account you want
3. Google returns with a code. After that, make a request to our backend, on an authenticated endpoint eg POST /users/{userId}/accounts which will receive the token returned by Google
4. In the backend, verify this token by making a request to Google
5. If all is good, link user's account with Google by updating the db accordingly

My question is, for step 4 , what is the best practice for that? How can I use all the stuff that Spring Security is offering to achieve this?

Thank you in advance,

Answer 1

You have the authorization code and you exchange for access token all over https and all in backend.

There is no need to validate access token ( I don't think spring security even does this part for integration with google ) at your end.

This should be done by google when you request its resource.