Add User Authentication System

Objective

Implement a secure user authentication system with JWT-based token management, password hashing, and session handling. The system should support user registration, login, logout, and token refresh capabilities while maintaining security best practices.

Implementation Plan

• 1. Set up authentication dependencies and configuration

  • Add JWT library (e.g., jsonwebtoken) and bcrypt for password hashing
  • Configure environment variables for JWT secrets and token expiration
  • Rationale: Establishes foundation for secure authentication
  • Dependencies: None - this is the first step

• 2. Create user model and database schema

  • Define User entity with fields: id, email, password_hash, created_at, updated_at
  • Add unique constraint on email field
  • Create database migration for users table
  • Rationale: Provides data structure for storing user credentials
  • Dependencies: Database connection must be configured

• 3. Implement password hashing service

  • Create service to hash passwords using bcrypt with appropriate salt rounds
  • Add password verification function
  • Include unit tests for hashing and verification
  • Rationale: Ensures passwords are never stored in plain text
  • Dependencies: User model must exist

• 4. Build JWT token generation and validation

  • Create service to generate JWT tokens with user claims
  • Implement token verification and decoding logic
  • Add refresh token functionality with longer expiration
  • Rationale: Enables stateless authentication and session management
  • Dependencies: User model and environment configuration

• 5. Create authentication endpoints

  • POST /auth/register - User registration with email/password
  • POST /auth/login - User login returning access and refresh tokens
  • POST /auth/logout - Invalidate user session
  • POST /auth/refresh - Generate new access token from refresh token
  • Rationale: Provides API interface for authentication operations
  • Dependencies: All services from previous steps

• 6. Implement authentication middleware

  • Create middleware to validate JWT tokens on protected routes
  • Extract user information from valid tokens
  • Return 401 for invalid or expired tokens
  • Rationale: Protects routes requiring authentication
  • Dependencies: JWT validation service

• 7. Add rate limiting for authentication endpoints

  • Implement rate limiting on login and registration endpoints
  • Configure appropriate limits (e.g., 5 attempts per 15 minutes)
  • Rationale: Prevents brute force attacks
  • Dependencies: Authentication endpoints must exist

• 8. Write integration tests for authentication flow

  • Test complete registration → login → access protected route flow
  • Test token refresh mechanism
  • Test error cases (invalid credentials, expired tokens)
  • Rationale: Ensures entire authentication system works correctly
  • Dependencies: All implementation steps complete

Verification Criteria

• User can successfully register with valid email and password
• User can login and receive valid JWT tokens
• Protected routes return 401 for unauthenticated requests
• Protected routes allow access with valid JWT token
• Tokens expire after configured duration
• Refresh tokens can generate new access tokens
• Passwords are hashed and never stored in plain text
• Rate limiting prevents excessive authentication attempts
• All unit and integration tests pass
• Security audit shows no critical vulnerabilities

Potential Risks and Mitigations

1. Token Secret Exposure

   • Impact: If JWT secret is exposed, attackers can forge valid tokens
   • Likelihood: Medium
   • Mitigation: Store secrets in environment variables, never commit to repository, rotate secrets periodically
   • Contingency: Implement secret rotation mechanism and token revocation list

2. Weak Password Policy

   • Impact: Users choose weak passwords that are easily compromised
   • Likelihood: High
   • Mitigation: Enforce minimum password requirements (length, complexity), implement password strength meter
   • Contingency: Add option to require password reset for weak passwords

3. Session Hijacking

   • Impact: Attacker steals valid token and impersonates user
   • Likelihood: Medium
   • Mitigation: Use HTTPS only, implement short token expiration, add IP address validation
   • Contingency: Implement token revocation and force logout capability

4. Brute Force Attacks

   • Impact: Attacker attempts many password combinations to gain access
   • Likelihood: High
   • Mitigation: Implement rate limiting, add CAPTCHA after failed attempts, temporary account lockout
   • Contingency: Monitor failed login attempts and alert on suspicious patterns

Alternative Approaches

1. Session-Based Authentication

   • Description: Use traditional server-side sessions with cookies instead of JWT
   • Pros: Easier to invalidate sessions, better for server-rendered applications, no token size limitations
   • Cons: Requires session storage (Redis/database), harder to scale horizontally, not suitable for APIs consumed by multiple clients
   • Recommendation: Not chosen - JWT better suits stateless API architecture

2. OAuth 2.0 / Third-Party Authentication

   • Description: Use OAuth providers (Google, GitHub) for authentication instead of custom system
   • Pros: No password management, better security through established providers, easier for users
   • Cons: Dependency on external services, requires API keys and setup, limited control over authentication flow
   • Recommendation: Consider as future enhancement alongside custom authentication

3. Passwordless Authentication

   • Description: Use magic links or OTP sent via email/SMS instead of passwords
   • Pros: No password management, simpler user experience, eliminates weak password risk
   • Cons: Requires reliable email/SMS delivery, slower authentication flow, potential cost for SMS
   • Recommendation: Consider as alternative authentication method in future iteration

Assumptions

• Application already has database connection configured
• HTTPS/TLS is configured at infrastructure level
• Email service is available for potential password reset features
• Frontend application exists to consume authentication endpoints
• Environment variable management system is in place

Dependencies

• Database system (PostgreSQL, MySQL, or similar)
• JWT library compatible with the programming language
• Password hashing library (bcrypt or argon2)
• HTTP server framework with middleware support
• Environment configuration system

Notes

• Consider implementing password reset functionality in a follow-up iteration
• May want to add two-factor authentication (2FA) as security enhancement
• Monitor token expiration times and adjust based on usage patterns
• Plan for token revocation strategy if needed for security incidents