auth-patterns

name	auth-patterns
description	Autenticación en Next.js: NextAuth v5 (Auth.js), JWT, sesiones, middleware y RBAC. Stack: Next.js App Router + NextAuth v5 / Supabase Auth / JWT custom. Usar cuando: "NextAuth", "Auth.js", "login", "sesión", "JWT", "middleware de auth", "proteger rutas", "RBAC", "roles y permisos", "OAuth", "credentials provider", "useSession", "getServerSession", "auth middleware", "redirect si no autenticado".

Auth Patterns — Next.js App Router

Stack: NextAuth v5 (Auth.js) + Prisma / Supabase como adapter.

Para proyectos con Supabase como DB principal, ver también supabase-stack (tiene su propio sistema de auth con RLS).

---

1. Decision Tree

¿Usas Supabase como DB?
├── SÍ → Supabase Auth (ver supabase-stack)
└── NO
    ├── ¿OAuth (Google, GitHub) + credentials?  → NextAuth v5
    ├── ¿Solo JWT custom (API/Express)?          → JWT manual (Sección 6)
    └── ¿Solo sesiones simples?                  → iron-session

---

2. NextAuth v5 — Setup

npm install next-auth@beta @auth/prisma-adapter

// auth.ts (raíz del proyecto)
import NextAuth from 'next-auth'
import Credentials from 'next-auth/providers/credentials'
import Google from 'next-auth/providers/google'
import { PrismaAdapter } from '@auth/prisma-adapter'
import { prisma } from '@/lib/prisma'
import { z } from 'zod'
import bcrypt from 'bcryptjs'

export const { handlers, auth, signIn, signOut } = NextAuth({
  adapter: PrismaAdapter(prisma),
  session: { strategy: 'jwt' },
  pages: {
    signIn: '/login',
    error: '/login',
  },
  providers: [
    Google({
      clientId: process.env.GOOGLE_CLIENT_ID!,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET!,
    }),
    Credentials({
      async authorize(credentials) {
        const parsed = z.object({
          email: z.string().email(),
          password: z.string().min(6),
        }).safeParse(credentials)

        if (!parsed.success) return null

        const user = await prisma.user.findUnique({
          where: { email: parsed.data.email },
        })
        if (!user?.password) return null

        const valid = await bcrypt.compare(parsed.data.password, user.password)
        if (!valid) return null

        return { id: user.id, email: user.email, name: user.name, role: user.role }
      },
    }),
  ],
  callbacks: {
    jwt({ token, user }) {
      if (user) {
        token.id = user.id
        token.role = user.role  // extender token con campos custom
      }
      return token
    },
    session({ session, token }) {
      session.user.id = token.id as string
      session.user.role = token.role as string
      return session
    },
  },
})

// app/api/auth/[...nextauth]/route.ts
export { handlers as GET, handlers as POST } from '@/auth'

---

3. Middleware — Proteger rutas

// middleware.ts (raíz del proyecto)
import { auth } from '@/auth'
import { NextResponse } from 'next/server'

const PUBLIC_ROUTES = ['/', '/login', '/register', '/api/auth']
const ADMIN_ROUTES = ['/admin']

export default auth((req) => {
  const { pathname } = req.nextUrl
  const isPublic = PUBLIC_ROUTES.some((r) => pathname.startsWith(r))

  if (!req.auth && !isPublic) {
    return NextResponse.redirect(new URL('/login', req.url))
  }

  // RBAC: solo admins en /admin
  if (ADMIN_ROUTES.some((r) => pathname.startsWith(r))) {
    if (req.auth?.user?.role !== 'admin') {
      return NextResponse.redirect(new URL('/dashboard', req.url))
    }
  }

  return NextResponse.next()
})

export const config = {
  matcher: ['/((?!_next/static|_next/image|favicon.ico|images/).*)'],
}

---

4. Sesión en Server Components y API Routes

// Server Component
import { auth } from '@/auth'

export default async function DashboardPage() {
  const session = await auth()
  if (!session) redirect('/login')

  return <div>Hola {session.user.name}</div>
}

// API Route (Server Action)
import { auth } from '@/auth'

export async function getLeads() {
  const session = await auth()
  if (!session) throw new Error('Unauthorized')

  return prisma.lead.findMany({ where: { userId: session.user.id } })
}

---

5. Sesión en Client Components

'use client'
import { useSession, signIn, signOut } from 'next-auth/react'

export function UserMenu() {
  const { data: session, status } = useSession()

  if (status === 'loading') return <Skeleton />
  if (!session) return <button onClick={() => signIn()}>Login</button>

  return (
    <div>
      <span>{session.user.name}</span>
      <button onClick={() => signOut({ callbackUrl: '/' })}>Logout</button>
    </div>
  )
}

// SessionProvider en layout.tsx
import { SessionProvider } from 'next-auth/react'

export default function RootLayout({ children }) {
  return (
    <html>
      <body>
        <SessionProvider>{children}</SessionProvider>
      </body>
    </html>
  )
}

---

6. JWT Custom (Express / API pura)

// Para backends Express sin NextAuth
import jwt from 'jsonwebtoken'
import bcrypt from 'bcryptjs'

// Generar token en login
export function generateTokens(userId, role) {
  const accessToken = jwt.sign(
    { sub: userId, role },
    process.env.JWT_SECRET,
    { expiresIn: '15m' }
  )
  const refreshToken = jwt.sign(
    { sub: userId },
    process.env.JWT_REFRESH_SECRET,
    { expiresIn: '7d' }
  )
  return { accessToken, refreshToken }
}

// Middleware de verificación
export function requireAuth(req, res, next) {
  const auth = req.headers.authorization
  if (!auth?.startsWith('Bearer ')) {
    return res.status(401).json({ error: 'Token requerido' })
  }
  try {
    const payload = jwt.verify(auth.slice(7), process.env.JWT_SECRET)
    req.user = payload
    next()
  } catch (err) {
    const msg = err.name === 'TokenExpiredError' ? 'Token expirado' : 'Token inválido'
    res.status(401).json({ error: msg })
  }
}

// Middleware de rol
export function requireRole(...roles) {
  return (req, res, next) => {
    if (!roles.includes(req.user?.role)) {
      return res.status(403).json({ error: 'Sin permiso' })
    }
    next()
  }
}

---

7. Schema Prisma para auth

model User {
  id            String    @id @default(cuid())
  email         String    @unique
  password      String?   // null si usa OAuth
  name          String?
  role          Role      @default(USER)
  emailVerified DateTime?
  image         String?
  createdAt     DateTime  @default(now())

  // NextAuth adapter
  accounts Account[]
  sessions Session[]
}

enum Role {
  USER
  ADMIN
  SUPERVISOR
}

// Solo si usas NextAuth con DB adapter
model Account {
  id                String  @id @default(cuid())
  userId            String
  type              String
  provider          String
  providerAccountId String
  refresh_token     String?
  access_token      String?
  expires_at        Int?
  user              User    @relation(fields: [userId], references: [id], onDelete: Cascade)
  @@unique([provider, providerAccountId])
}

---

8. Variables de entorno

# NextAuth v5
AUTH_SECRET=min-32-chars-random-string  # npx auth secret
AUTH_URL=https://yourapp.com            # producción
GOOGLE_CLIENT_ID=...
GOOGLE_CLIENT_SECRET=...

# JWT custom (Express)
JWT_SECRET=min-32-chars
JWT_REFRESH_SECRET=min-32-chars-diferente

---

9. Errores comunes

Error	Causa	Fix
[auth] missing secret	AUTH_SECRET no configurado	Generar con npx auth secret
Session siempre null en RSC	Olvidó await auth()	Usar const session = await auth()
OAuth no redirige	AUTH_URL incorrecto en prod	Configurar AUTH_URL exacto
JWT expirado en cliente	Access token vence rápido	Implementar refresh token rotation
Middleware bloquea assets	matcher muy amplio	Excluir _next/static, images/