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name: auth-patterns description: This skill should be used when the user asks to "add authentication", "protect an endpoint", "implement OAuth", "set up OIDC", "handle JWT tokens", "implement RBAC", "add permissions", "secure API routes", "implement 2FA", "add role-based access", or needs guidance on authentication flows, token management, or authorization patterns. version: 1.0.0

Authentication & Authorization Patterns

Secure authentication flows, token management, and role-based access control.

Core Concepts

Concept	Description
Authentication	Verify identity (who you are)
Authorization	Verify permissions (what you can do)
OAuth 2.0	Delegated authorization framework
OIDC	Identity layer on top of OAuth 2.0
JWT	Stateless token format for claims
RBAC	Role-Based Access Control

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Authentication Patterns

JWT Authentication Flow

1. User submits credentials
2. Server validates credentials
3. Server generates JWT (access + refresh tokens)
4. Store tokens in HttpOnly cookies (preferred) or secure storage
5. Client sends token with each request
6. Server validates token and extracts claims

Token Storage Strategy

Location	Security	Use Case
HttpOnly Cookie	High	Web apps (CSRF protection needed)
Memory	High	SPAs (lost on refresh)
localStorage	Low	Avoid (XSS vulnerable)
Secure Cookie + Memory	Highest	Hybrid approach

Token Refresh Pattern

Access Token: Short-lived (15-30 min)
Refresh Token: Long-lived (7-30 days)

1. Access token expires
2. Client sends refresh token
3. Server validates refresh token
4. Server issues new access token
5. Optionally rotate refresh token

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Authorization Patterns

RBAC Implementation

User → UserRole → Role → RolePermission → Permission

Component	Responsibility
Permission	Granular action (e.g., users.create)
Role	Collection of permissions
UserRole	Assignment of roles to users

Permission Middleware Pattern

// Middleware chain
authenticate → extractTenant → checkPermission → handler

Permission Naming Convention

resource.action

Examples:
- users.create
- users.read
- users.update
- users.delete
- roles.assign
- applications.manage

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OAuth 2.0 / OIDC Flows

Authorization Code + PKCE (Recommended)

1. Generate code_verifier (random string)
2. Create code_challenge = SHA256(code_verifier)
3. Redirect to /authorize with code_challenge
4. User authenticates
5. Receive authorization code
6. Exchange code + code_verifier for tokens

OIDC Endpoints

Endpoint	Purpose
/.well-known/openid-configuration	Discovery document
/.well-known/jwks.json	Public keys for verification
/authorize	Start auth flow
/token	Exchange code for tokens
/userinfo	Get user claims
/revoke	Revoke tokens
/end_session	Logout

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Security Best Practices

Token Security

• Store in HttpOnly cookies with Secure flag
• Implement token blacklist for logout
• Use short expiration for access tokens
• Rotate refresh tokens on use
• Validate token signature and claims

Password Security

• Hash with bcrypt (cost factor 12+)
• Enforce complexity requirements
• Implement rate limiting on login
• Add account lockout after failures

2FA Implementation

1. User enables 2FA
2. Generate TOTP secret
3. Store encrypted secret
4. User scans QR code
5. Verify initial code
6. On login: verify password + TOTP

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Multi-Tenancy Considerations

Tenant Isolation

// Always scope queries by tenantId
const users = await prisma.user.findMany({
  where: { tenantId: currentTenant.id }
});

Tenant-Aware Auth

1. Extract tenant from subdomain/header/token
2. Validate user belongs to tenant
3. Scope all queries to tenant
4. Include tenantId in JWT claims

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Additional Resources

Reference Files

For detailed implementation patterns, consult:

• references/jwt-implementation.md - JWT generation, validation, refresh flows
• references/oauth-oidc-flows.md - Complete OAuth/OIDC implementation guide
• references/rbac-patterns.md - RBAC schema design and permission checking

Example Files

Working examples in examples/:

• auth-middleware.ts - Express authentication middleware
• permission-middleware.ts - RBAC permission checking
• oauth-client.ts - OAuth client implementation

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Quick Decision Guide

Need	Solution
Simple API auth	JWT in HttpOnly cookies
Third-party login	OAuth 2.0 Authorization Code + PKCE
Microservices	JWT with shared secret or JWKS
Role-based access	RBAC with permission middleware
Extra security	Add 2FA (TOTP)
Multi-tenant	Tenant-scoped tokens and queries

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Validation Checklist

Before completing auth implementation:

• Tokens stored securely (HttpOnly cookies)
• Password hashing with bcrypt
• Rate limiting on auth endpoints
• Token expiration configured
• Refresh token rotation enabled
• CSRF protection for cookies
• Permission checks on protected routes
• Tenant isolation verified
• Logout invalidates tokens