Spring Boot Example OpenID Connect Relying Party for Singpass/Corppass

This project is an example implementation of a OpenID Connect Relying Party built using Spring Boot and Spring Security OAuth2 Client.

MockPass is used as the public Identity Provider for testing purposes

Quick Start

Configuring MockPass as the Identity Provider

The Spring Boot application exposes its JWKS at http://localhost:8080/oauth2/jwks

set SHOW_LOGIN_PAGE=true
set SP_RP_JWKS_ENDPOINT=http://localhost:8080/oauth2/jwks
set CP_RP_JWKS_ENDPOINT=http://localhost:8080/oauth2/jwks
npx --y @opengovsg/mockpass

Installing and running the Relying Party Spring Boot application

mvn spring-boot:run

Testing the example Relying Party

Description	Endpoint
Access the application	http://localhost:8080/login-user
Logout from the application	http://localhost:8080/logout
View the public keys	http://localhost:8080/oauth2/jwks
View Mockpass public keys	http://localhost:5156/singpass/v2/.well-known/keys
View Mockpass OpenID configuration	http://localhost:5156/singpass/v2/.well-known/openid-configuration

Integration Details

The following things are needed to be configured in Spring for the integration

• Exposing the signature and encryption public keys via a JWKS endpoint
• Use private_key_jwt client authentication with the aud claim set to the iss value and the typ header set to JWT
• ID token needs to be decrypted with the private decryption key and signature verified against the Identity Provider's JWKS endpoint

Note that this example does not securely store the private keys which are located in src/main/resources/jwks.json. This should be securely stored and rotated, for instance on AWS this should be stored in AWS Secrets Manager with a Secrets Manager Rotation Lambda. This can be configured in Spring using Spring Cloud AWS Secrets Manager.

Json Web Key Sets

Mockpass will call the endpoint http://localhost:8080/oauth2/jwks in order to get the public keys of the application

• The public encryption key used for Mockpass to encrypt the ID Token to send to the application
• The public verification key used for Mockpass to verify the signature for the private_key_jwt client assertion

The JWKSet @Bean used by the application is produced in WebSecurityConfiguration and its public keys are exposed using the @RestController JwksController. Note that JWKSet.toString() removes the private components of the keys.

Client Authentication

Mockpass requires the use of private_key_jwt client authentication.

Spring needs to be configured to use this client authentication method, and the token response client needs to be configured to use the appropriate private key to perform the signing as well as to set the aud claim to the issuer value.

spring:
  security:
    oauth2:
      client:
        registration:
          mockpass:
            client-id: mockpass-spring-boot-example
            client-authentication-method: private_key_jwt
            authorization-grant-type: authorization_code
            scope:
            - openid

The DefaultAuthorizationCodeTokenResponseClient is used with the NimbusJwtClientAuthenticationParametersConverter configured with the private key and NimbusJwtClientAuthenticationParametersConverter used to customize the claims and headers on the client assertion.

Decrypting ID Token

A JwtDecoderFactory<ClientRegistration> @Bean needs to be exposed to customize how the ID Token is decoded. A DefaultJWTProcessor<SecurityContext> is used with the JWEKeySelector and JWSKeySelector with the application's private decryption key to decrypt the ID Token and Mockpass's verification key to verify the signature on the ID Token. The verification keys from Mockpass are obtained by querying Mockpass's JWKS endpoint.

Flow

sequenceDiagram
    autonumber

    participant User
    participant Browser
    participant Application Server
    participant Mockpass

    User->>Browser: Navigate to user information page

    Browser->>Application Server: Send request for user information page (/login-user)

    Application Server->>Application Server: Not authenticated, determine provider to redirect to

    Application Server-->>Browser: Redirect to Application for Mockpass provider

    Browser->>Application Server: Send request for Mockpass provider (/oauth2/authorization/mockpass)

    Application Server->>Application Server: Generate Authorization Request

    Application Server-->>Browser: Redirect to Mockpass with Authorization Request

    Browser->>Mockpass: Send Authorization Request (/singpass/v2/authorize)

    Mockpass->>Mockpass: Generate login page

    Mockpass-->>Browser: Return login page

    User->>Browser: Enter login credentials and sign in

    Browser->>Mockpass: Send login credentials 

    Mockpass->>Mockpass: Process login credentials

    Mockpass-->>Browser: Redirect to Application with Authorization Response with code

    Browser->>Application Server: Send Authorization Response with code (/login/oauth2/code/mockpass)

    Application Server->>Application Server: Generate Token Request and client credentials

    Application Server->>Mockpass: Send Token Request with client credentials (/singpass/v2/token)

    Mockpass->>Application Server: Send request for client json web key set (/oauth2/jwks)

    Application Server-->>Mockpass: Return client json web key set

    Mockpass->>Mockpass: Process client credentials and create tokens

    Mockpass-->>Application Server: Return Token Response with access and id tokens

    Application Server-->>Browser: Redirect to user information page

    Browser->>Application Server: Send request for user information page (/login-user)

    Application Server->>Application Server: Authenticated

    Application Server-->>Browser: Return user information page

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