0011. Stateless JWT Authentication

Status: Accepted Date: 2025-12-10 Context: Migrate from hybrid JWT plus sessions to fully stateless JWT authentication for horizontal scaling.

Context

The application initially used a hybrid authentication system:

• Backend services used JWT-based authentication (stateless)
• UI modules used session-based authentication (stateful)
• Both mechanisms coexisted, with sessions taking precedence for UI

This hybrid approach created several issues:

• Required sticky sessions or shared session stores for horizontal scaling
• Increased complexity with two authentication mechanisms
• Session state management overhead
• Inconsistent authentication patterns across modules

The system needed to support true horizontal scaling without session affinity requirements.

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Decision

We will use fully stateless JWT-based authentication across all modules (backend services and frontend UI modules).

All authentication flows return JWT tokens that are:

• Stored client-side (localStorage for web applications)
• Included in API requests via Authorization: Bearer <token> header
• Validated server-side by TokenAuthenticationFilter
• Enforced by @Secured annotation via UserTokenAuthorizationInterceptor

Key Changes

1. Removed Session Support:

   • Deleted security-web module
   • Removed SessionAuthenticationFilter ✅ (completed 2025-12-11)
   • Removed SessionAuthResource ✅ (completed 2025-12-11)
   • Removed CognitoFormLoginResource ✅ (completed 2025-12-11)
   • Removed SessionAttribute enum ✅ (completed 2025-12-11)
   • Removed PageProtectionRouteHandler
   • Removed session-related CORS configuration

2. Unified Authentication Model:

   • Single @Secured annotation for all authentication
   • JWT tokens for all modules (backend and frontend)
   • Client-side token storage and management
   • Automatic token validation via JAX-RS filter

3. Frontend Authentication:

   • Login returns JWT tokens (not session cookies)
   • Tokens stored in localStorage
   • JavaScript handles page protection
   • Automatic token refresh on expiration

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Consequences

Positive:

• True Stateless: No server-side session state required
• Horizontal Scaling: No sticky sessions or shared session stores needed
• Simplified Architecture: Single authentication mechanism across all modules
• Better Performance: No session lookups required
• Mobile-Friendly: JWT tokens work well for mobile applications
• Consistent Security Model: Same @Secured annotation everywhere

Negative / Tradeoffs:

• Client-Side Token Management: Frontend must handle token storage, expiration, and refresh
• Token Security: Tokens stored in localStorage are vulnerable to XSS attacks (mitigated by proper CSP headers)
• No Server-Side Revocation: JWT tokens cannot be revoked until expiration (acceptable tradeoff for stateless design)

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Implementation

Backend

All REST endpoints use @Secured annotation:

• TokenAuthenticationFilter validates tokens from Authorization header
• UserTokenAuthorizationInterceptor enforces authorization for @Secured methods
• Returns 401 Unauthorized if token is missing or invalid

Frontend

JavaScript handles authentication:

• Login via POST /auth/login (returns JWT tokens)
• Store tokens in localStorage
• Include Authorization: Bearer <token> in all API requests
• Check token expiration and refresh automatically
• Protect pages by checking for valid token on load

Request Flow

All frontend requests route through BFF on port N:

• POST /api/session → bff → auth-service

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