Spring OAuth2 Single Page Application Integration to Azure - azure-active-directory

Question

I have been tasked with integrating Azure Active Directory Authorization into one of our applications and have tried out some of the samples with relative success.
I have a Javascript SPA application (GoogleWebToolkit) that communicates with a Spring REST (not Boot) API. The Rest API is currently secured with Spring Security and login URL username/password etc.
I want to change this to use Azure OAuth2.
Being new to OAuth2 I'm trying to figure out if I should be using either of the following Spring options.
With this option all the configuration is done at the server side, client id,secret
If I do a href from the SPA front end to 'oauth2/authorization/AzureAD' URL, its sends a redirect to the Azure Login page, allows authentication and redirects back to what redirect URL I enter into the Azure AD console configuration. This works to a degree but trying to extract the token and pass it back is not working so far.
http.oauth2Login()
.clientRegistrationRepository(clientRegistrationRepository())
.authorizedClientService(authorizedClientService())
.authorizationEndpoint()
.authorizationRequestResolver(
new CustomAuthorizationRequestResolver(
clientRegistrationRepository(),
#Bean
public ClientRegistration clientRegistration() {
ClientRegistration.Builder builder = ClientRegistration.withRegistrationId("AzureAD");
builder.clientAuthenticationMethod(ClientAuthenticationMethod.CLIENT_SECRET_POST);
builder.authorizationGrantType(AuthorizationGrantType.AUTHORIZATION_CODE);
........................
or
I haven't fully tried this option yet, but I think it involves doing the authorization directly from the SPA javascript front end, put all the values for the client id/secret into the javascript FE etc, and then passing the once acquired token via the Auth header for validation by the server side. Like at https://www.baeldung.com/spring-security-oauth-jwt
.oauth2ResourceServer()
.jwt()
.jwkSetUri("https://login.microsoftonline.com/common/discovery/v2.0/keys");
Could someone confirm where I should be using Option 1 or 2, and if I am understanding things properly?

Answer 1

Your understanding is correct in option 2. As per above scenario, let’s consider Front End Application which is Single Page Application (Java Script) to be OAuth Client App to orchestrate the process of obtaining access token and then grant access to resources from Spring back-end application.
So, here client Application need to be registered in Azure AD to acquire the access token secured by Azure AD.
We recommended MSAL libraries which helps to acquire tokens from the Microsoft identity platform and handle token in many ways to authenticate users and access secured web APIs.
Both the applications (front end and back end) need to register in Azure AD based on the scenario.
Update client-id, tenant-id, redirect URI to front end application configuration file based on application registration in Azure AD.
Back-end application also need to be registered in Azure Ad to secure by Microsoft Identity which can then define the delegated permissions(scopes) your API exposes.
Then business logic needs to add in back-end application to determine what is allowed or prohibited based on these scopes in access token.
To authorize the client request in Spring application:
Users will start by authenticating with a username and password in front end application.
Once authenticated, the client will receive a JWT representing an access token.
The client will include the access token in the authorization header of every request to a secure endpoint.
The resource server will validate the access token and determine if it has the right permissions, using the information within the token.
In this case, Spring serves as resource server and not acquiring any token in the back-end application .
Security Configuration in Spring provides numerous methods to add filters to the HTTP request to authenticate each request.
Here,
http.cors() will allows Cross-Origin Resource Sharing (CORS) checks to succeed.
All the requests need to authenticate before passing to the application(controllers).
Spring application serve as a resource server and authentication should be provided via JWT access tokens and further validate the roles and scopes in the application’s controller using #AllowedRoles annotation.
Our JWT access tokens are signed by Azure AD and application should check if their signature is correct. Azure AD has an endpoint with the public key to do so, which need to configure in spring application.
Also, as mentioned, we will need access token to call the protected back-end application because contents of the token are intended for the resource (back-end API) to perform authentication and authorization.
To validate the token, you can search the keys endpoint in the discovery document and then provide this JSON web key (JWK) endpoint straight away where JWK URI can be found.
# application.properties
spring.security.oauth2.resourceserver.jwt.jwk-set-uri=https://login.windows.net/common/discovery/keys
Note: The flow would be same to get the access token while integrating with Azure AD. i.e in Spring boot or in spring.