Building a Secure PKCE Flow with Kotlin and Spring Boot
Visual Overview: sequenceDiagram participant User participant App as Client App participant AuthServer as Authorization Server participant Resource as Resource Server User->>App: 1. Click Login App->>AuthServer: 2. Authorization Request AuthServer->>User: 3. Login Page User->>AuthServer: 4. Authenticate AuthServer->>App: 5. Authorization Code App->>AuthServer: 6. Exchange Code for Token AuthServer->>App: 7. Access Token + Refresh Token App->>Resource: 8. API Request with Token Resource->>App: 9. Protected Resource Proof Key for Code Exchange (PKCE) has become a standard security enhancement to the OAuth 2.0 Authorization Code Flow—especially in public clients like mobile and single-page applications. But PKCE isn’t just for frontend apps. When combined with a stateless backend built with Kotlin and Spring Boot, it strengthens your security posture, particularly when you’re avoiding client secrets. ...