Authentication & Authorization Implementation Patterns
Build secure, scalable authentication and authorization systems using industry-standard patterns and modern best practices.
When to Use This Skill
- Implementing user authentication systems
- Securing REST or GraphQL APIs
- Adding OAuth2/social login
- Implementing role-based access control (RBAC)
- Designing session management
- Migrating authentication systems
- Debugging auth issues
- Implementing SSO or multi-tenancy
Core Concepts
1. Authentication vs Authorization
Authentication (AuthN): Who are you?
- Verifying identity (username/password, OAuth, biometrics)
- Issuing credentials (sessions, tokens)
- Managing login/logout
Authorization (AuthZ): What can you do?
- Permission checking
- Role-based access control (RBAC)
- Resource ownership validation
- Policy enforcement
2. Authentication Strategies
Session-Based:
- Server stores session state
- Session ID in cookie
- Traditional, simple, stateful
Token-Based (JWT):
- Stateless, self-contained
- Scales horizontally
- Can store claims
OAuth2/OpenID Connect:
- Delegate authentication
- Social login (Google, GitHub)
- Enterprise SSO
Detailed patterns and worked examples
Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.
Best Practices
- Never Store Plain Passwords: Always hash with bcrypt/argon2
- Use HTTPS: Encrypt data in transit
- Short-Lived Access Tokens: 15-30 minutes max
- Secure Cookies: httpOnly, secure, sameSite flags
- Validate All Input: Email format, password strength
- Rate Limit Auth Endpoints: Prevent brute force attacks
- Implement CSRF Protection: For session-based auth
- Rotate Secrets Regularly: JWT secrets, session secrets
- Log Security Events: Login attempts, failed auth
- Use MFA When Possible: Extra security layer
Common Pitfalls
- Weak Passwords: Enforce strong password policies
- JWT in localStorage: Vulnerable to XSS, use httpOnly cookies
- No Token Expiration: Tokens should expire
- Client-Side Auth Checks Only: Always validate server-side
- Insecure Password Reset: Use secure tokens with expiration
- No Rate Limiting: Vulnerable to brute force
- Trusting Client Data: Always validate on server
