ancoleman/ai-design-components/securing-authentication

┌─────────────────────────────────────────────────────────────┐
│           OAuth 2.1 MANDATORY REQUIREMENTS                  │
│                   (RFC 9798 - 2025)                         │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  ✅ REQUIRED (Breaking Changes from OAuth 2.0)             │
│  ├─ PKCE (Proof Key for Code Exchange) MANDATORY           │
│  │   └─ S256 method (SHA-256), minimum entropy 43 chars   │
│  ├─ Exact redirect URI matching                            │
│  │   └─ No wildcard matching, no substring matching       │
│  ├─ Authorization code flow ONLY for public clients       │
│  │   └─ All other flows require confidential client       │
│  └─ TLS 1.2+ required for all endpoints                   │
│                                                             │
│  ❌ REMOVED (No Longer Supported)                          │
│  ├─ Implicit grant (security vulnerabilities)             │
│  ├─ Resource Owner Password Credentials grant              │
│  │   └─ Use OAuth 2.0 Device Flow (RFC 8628) instead      │
│  └─ Bearer token in query parameters                       │
│      └─ Must use Authorization header or POST body        │
│                                                             │
└─────────────────────────────────────────────────────────────┘

{
  "iss": "https://auth.example.com",
  "sub": "user-id-123",
  "aud": "api.example.com",
  "exp": 1234567890,
  "iat": 1234567890,
  "jti": "unique-token-id",
  "scope": "read:profile write:data"
}

Algorithm: Argon2id
Memory cost (m): 64 MB (65536 KiB)
Time cost (t): 3 iterations
Parallelism (p): 4 threads
Salt length: 16 bytes (128 bits)
Target hash time: 150-250ms

┌─────────────────────────────────────────────────────────────┐
│                Authorization Model Selection                │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  Simple Roles (<20 roles)                                  │
│  └─ RBAC with Casbin (embedded, any language)              │
│      Example: Admin, User, Guest                           │
│                                                             │
│  Complex Attribute Rules                                    │
│  └─ ABAC with OPA or Cerbos                                │
│      Example: "Allow if user.clearance >= doc.level        │
│                AND user.dept == doc.dept"                   │
│                                                             │
│  Relationship-Based (Multi-Tenant, Collaborative)          │
│  └─ ReBAC with SpiceDB (Zanzibar model)                    │
│      Example: "Can edit if member of doc's workspace       │
│                AND workspace.plan includes feature"         │
│      Use cases: Notion-like, GitHub-like permissions       │
│                                                             │
│  Kubernetes / Infrastructure Policies                       │
│  └─ OPA (Gatekeeper for admission control)                 │
│      Example: Enforce pod security policies                │
│                                                             │
└─────────────────────────────────────────────────────────────┘

// Tiered rate limiting (per IP + per user)
const rateLimits = {
  anonymous: '10 requests/minute',
  authenticated: '100 requests/minute',
  premium: '1000 requests/minute',
}

// Restrictive CORS (production)
const corsOptions = {
  origin: ['https://app.example.com'],
  credentials: true,
  maxAge: 86400, // 24 hours
  allowedHeaders: ['Content-Type', 'Authorization'],
  methods: ['GET', 'POST', 'PUT', 'DELETE', 'PATCH'],
}
// NEVER use origin: '*' with credentials: true

const securityHeaders = {
  'Strict-Transport-Security': 'max-age=63072000; includeSubDomains; preload',
  'X-Frame-Options': 'DENY',
  'X-Content-Type-Options': 'nosniff',
  'Referrer-Policy': 'strict-origin-when-cross-origin',
  'Permissions-Policy': 'geolocation=(), microphone=(), camera=()',
  'Content-Security-Policy': "default-src 'self'; script-src 'self'",
}

// middleware.ts
import { withAuth } from 'next-auth/middleware'
export default withAuth({
  callbacks: {
    authorized: ({ token, req }) => {
      if (req.nextUrl.pathname.startsWith('/dashboard')) {
        return !!token
      }
      if (req.nextUrl.pathname.startsWith('/admin')) {
        return token?.role === 'admin'
      }
      return true
    },
  },
})
export const config = {
  matcher: ['/dashboard/:path*', '/admin/:path*'],
}

import { useSession } from 'next-auth/react'
export function AdminPanel() {
  const { data: session } = useSession()
  if (session?.user?.role !== 'admin') {
    return null
  }
  return <div>Admin Controls</div>
}