Learn how to implement Role-Based Access Control (RBAC) in Next.js with JWT authentication, refresh tokens, secure API routes, and role-based UI rendering. This step-by-step guide covers authentication, protected routes, middleware security, and dynamic UI updates for a secure Next.js application

📌 Introduction

Managing access control in a Next.js application is crucial, especially for admin dashboards, multi-user systems, and API security. In this guide, we'll implement RBAC (Role-Based Access Control) with:
✅ JWT Authentication (Access & Refresh Tokens)
✅ Local Storage & Cookies for Session Management
✅ Role-Based UI Rendering
✅ Client-Side Protection (HOC: AuthGuard)
✅ Server-Side Middleware for Secure Routing
✅ Secure API Protection

By the end, your app will have secure authentication, refresh token handling, and role-based page access.

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🛠 1️⃣ Authentication System (Login & Refresh Tokens)

🔹 User Authentication with JWT Tokens

We'll generate two JWTs:

• Access Token (expires in 15 min)
• Refresh Token (used to get a new Access Token when expired)

🔹 Mock User Data

We simulate a user database:

const users = [
  { id: 1, username: "admin", password: "admin123", role: "admin" },
  { id: 2, username: "user", password: "user123", role: "user" },
];

---

🔹 2️⃣ Create API Routes for Login & Token Refresh

📌 pages/api/login.js (Generate Access & Refresh Tokens)

import jwt from "jsonwebtoken";
import { serialize } from "cookie";

const SECRET_KEY = "SECRET_KEY";
const REFRESH_SECRET = "REFRESH_SECRET";

export default function handler(req, res) {
  if (req.method !== "POST") return res.status(405).end();

  const { username, password } = req.body;
  const user = users.find(u => u.username === username && u.password === password);

  if (!user) return res.status(401).json({ message: "Invalid credentials" });

  // Generate Tokens
  const accessToken = jwt.sign({ id: user.id, role: user.role }, SECRET_KEY, { expiresIn: "15m" });
  const refreshToken = jwt.sign({ id: user.id, role: user.role }, REFRESH_SECRET, { expiresIn: "7d" });

  res.setHeader("Set-Cookie", serialize("refreshToken", refreshToken, { httpOnly: true, path: "/" }));
  res.status(200).json({ accessToken, role: user.role });
}

✅ Stores refresh token in cookies
✅ Returns access token & user role

---

📌 pages/api/refresh.js (Generate New Access Token)

import jwt from "jsonwebtoken";

const SECRET_KEY = "SECRET_KEY";
const REFRESH_SECRET = "REFRESH_SECRET";

export default function handler(req, res) {
  const refreshToken = req.cookies.refreshToken;
  if (!refreshToken) return res.status(403).json({ message: "No refresh token" });

  try {
    const decoded = jwt.verify(refreshToken, REFRESH_SECRET);
    const newAccessToken = jwt.sign({ id: decoded.id, role: decoded.role }, SECRET_KEY, { expiresIn: "15m" });
    
    res.status(200).json({ accessToken: newAccessToken });
  } catch {
    res.status(403).json({ message: "Invalid refresh token" });
  }
}

✅ Verifies refresh token & issues new access token

---

🔐 3️⃣ Client-Side Authentication

🔹 Create a Login Page

pages/login.js

import { useState } from "react";
import { useRouter } from "next/router";

export default function Login() {
  const [username, setUsername] = useState("");
  const [password, setPassword] = useState("");
  const router = useRouter();

  const handleLogin = async (e) => {
    e.preventDefault();
    const res = await fetch("/api/login", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ username, password }),
    });

    if (res.ok) {
      const data = await res.json();
      localStorage.setItem("accessToken", data.accessToken);
      localStorage.setItem("role", data.role);
      router.push("/dashboard");
    } else {
      alert("Invalid credentials");
    }
  };

  return (
    <form onSubmit={handleLogin}>
      <input type="text" placeholder="Username" onChange={(e) => setUsername(e.target.value)} required />
      <input type="password" placeholder="Password" onChange={(e) => setPassword(e.target.value)} required />
      <button type="submit">Login</button>
    </form>
  );
}

🔹 Stores access token & role in localStorage
🔹 Redirects users after login

---

🛡 4️⃣ Implementing Role-Based Page Protection (HOC)

🔹 AuthGuard.js (Restrict Pages Based on Role)

import { useRouter } from "next/router";
import { useEffect, useState } from "react";

const AuthGuard = ({ children, allowedRoles }) => {
  const [authenticated, setAuthenticated] = useState(false);
  const router = useRouter();

  useEffect(() => {
    const token = localStorage.getItem("accessToken");
    const role = localStorage.getItem("role");

    if (!token || !allowedRoles.includes(role)) {
      router.push("/login");
    } else {
      setAuthenticated(true);
    }
  }, []);

  if (!authenticated) return null;

  return children;
};

export default AuthGuard;

✅ Restricts pages based on roles

---

🎯 5️⃣ Role-Based UI Rendering

📌 components/Navbar.js

import { useEffect, useState } from "react";

export default function Navbar() {
  const [role, setRole] = useState("");

  useEffect(() => {
    setRole(localStorage.getItem("role"));
  }, []);

  return (
    <nav>
      <a href="/">Home</a>
      {role === "admin" && <a href="/admin-dashboard">Admin Panel</a>}
      {role && <a href="/user-dashboard">User Dashboard</a>}
      {!role && <a href="/login">Login</a>}
    </nav>
  );
}

✅ Dynamically updates UI based on role

---

⚙ 6️⃣ Secure Route Protection Using Middleware

📌 middleware.js

import { NextResponse } from "next/server";
import jwt from "jsonwebtoken";

const SECRET_KEY = "SECRET_KEY";

export function middleware(req) {
  const token = req.cookies.get("token");

  try {
    if (token) {
      const decoded = jwt.verify(token, SECRET_KEY);
      
      if (req.nextUrl.pathname.startsWith("/admin-dashboard") && decoded.role !== "admin") {
        return NextResponse.redirect(new URL("/login", req.url));
      }
    } else {
      return NextResponse.redirect(new URL("/login", req.url));
    }
  } catch {
    return NextResponse.redirect(new URL("/login", req.url));
  }

  return NextResponse.next();
}

✅ Prevents direct access even if localStorage is modified

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✅ Conclusion

🎯 Built a Secure Authentication System
🔹 Implemented JWT with Refresh Tokens
🔹 Added Role-Based Page & UI Protection
🔹 Secured API & Middleware for route protection

Now your Next.js app is fully secured with RBAC & Refresh Tokens! 🚀