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Next.js 13 Routes Part 2: Implementing Protected Routes

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Learn how to create protected routes using React Context as well as how using Clerk makes this process easier.

In part one of this series, you learned about Next.js API routes and how to protect API routes with JWT authentication. In this part, you'll learn how to create protected routes using React Context as well as how using Clerk makes this process easier.

Exploring the Starter App

To get started, a starter app already has been made that you can clone from GitHub:

git clone https://github.com/heraldofsolace/NextJS-protected-routes-demo.git
cd NextJS-protected-routes-demo
yarn install
yarn dev

The app will start running at localhost:3000.

The posts page can be found at http://localhost:3000/posts, which shows a list of all the posts.

List of all posts

This page has a companion API route that returns all the posts in JSON:

$ curl "http://localhost:3000/api/posts"
[{"id":1,"userId":1,"text":"Hello, World!"},{"id":2,"userId":2,"text":"Hello, NextJS"},{"id":3,"userId":1,"text":"Lorem ipsum dolor sit amet. "},{"id":4,"userId":3,"text":"Lorem ipsum dolor sit amet, consectetur adipiscing elit. Curabitur ut rhoncus neque. Sed lacinia magna a mi tincidunt, ac interdum."}]

The data for posts is stored in data.js.

The /api/auth/login route implements JWT authentication and returns a JWT when the correct username and password combination is supplied:

$ curl -X POST "http://localhost:3000/api/auth/login" -d '{"username": "john", "password": "password"}' -H 'Content-Type: application/json'
{"token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjMsImxvY2F0aW9uIjoiRnJhbmNlIiwibmFtZSI6IkpvaG4iLCJpYXQiOjE2Njk0NDUzMDQsImV4cCI6MTY2OTUzMTcwNH0.mlShbJr6xG8TIOyY6B2gD0c-leoyw1T3Sr5EncTgl00"}

Finally, the /api/users/me route returns the currently authenticated user, provided a valid JWT is passed in the header:

$ curl http://localhost:3000/api/users/me -H "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjMsImxvY2F0aW9uIjoiRnJhbmNlIiwibmFtZSI6IkpvaG4iLCJpYXQiOjE2Njk0NDUzMDQsImV4cCI6MTY2OTUzMTcwNH0.mlShbJr6xG8TIOyY6B2gD0c-leoyw1T3Sr5EncTgl00"
{"id":3,"username":"john","name":"John","location":"France"}

The user profiles can also be found in data.js.

The goal of the article is to protect the /api/posts API route and the /posts page using the JWT authentication strategy. In part one, you saw how JWT authentication can be added to API routes using the jwt.verify method. However, it's resource intensive to manually verify and decode the JWT in every single API route. It's also tedious to manually include the authentication header in every request that you make from a page.

In this article, you'll learn how to "share" an authenticated session across all pages by using an AuthContext. You'll also refactor the JWT verification to a withAuth wrapper that will make it easy to protect API routes. Finally, you'll see how using Clerk makes this process smooth and seamless.

Implementing AuthContext

AuthContext is simply a React Context that will make it easy to pass required authentication parameters throughout the app. To implement this, first install the required libraries:

yarn add js-cookie axios

js-cookie will be used to store the JWT in the browser's cookie. axios makes it easy to preconfigure a default API service with headers. You'll use this to include the token in the headers once the user logs in.

Create a file named api.js in the project root:

import Axios from 'axios'

const api = Axios.create({
  baseURL: 'http://localhost:3000',
  headers: {
    Accept: 'application/json',
    'Content-Type': 'application/json',
  },
})

export default api

Here, an instance of axios is created that will be used to make API calls later.

Create the file auth_context.js:

import React, { createContext, useState, useContext, useEffect } from 'react'
import Cookies from 'js-cookie'
import api from './api'
import jwt from 'jsonwebtoken'

const JWT_KEY = process.env.JWT_SECRET_KEY
const AuthContext = createContext({})

export const AuthProvider = ({ children }) => {
  const [user, setUser] = useState(null)
  const [isLoading, setIsLoading] = useState(true)

  useEffect(() => {
    async function fetchUserFromCookie() {
      const token = Cookies.get('token')
      if (token) {
        api.defaults.headers.Authorization = `Bearer ${token}`
        const { data: user } = await api.get('api/users/me')
        if (user) setUser(user)
      }
      setIsLoading(false)
    }
    fetchUserFromCookie()
  }, [])

  const login = async (username, password) => {
    const {
      data: { token },
    } = await api.post('api/auth/login', { username, password })
    console.log('TOKEN ', token)
    if (token) {
      Cookies.set('token', token, { expires: 60 })
      api.defaults.headers.Authorization = `Bearer ${token}`
      const { data: user } = await api.get('api/users/me')
      setUser(user)
    }
  }

  const logout = () => {
    Cookies.remove('token')
    setUser(null)
    delete api.defaults.headers.Authorization
    window.location.pathname = '/login'
  }

  return (
    <AuthContext.Provider
      value={{
        isAuthenticated: !!user,
        user,
        login,
        loading: isLoading,
        logout,
      }}
    >
      {children}
    </AuthContext.Provider>
  )
}

export const useAuth = () => useContext(AuthContext)

The most important bits in the above Context are the fetchUserFromCookie, login, and logout functions. The fetchUserFromCookie function fetches the token from the cookie and sets the authorization header in the default api instance.

It then makes a call to /api/users/me to retrieve and store the authenticated user. The login function logs in the user through the /api/auth/login route and stores the token in the cookie. The logout function deletes the user, the cookie, and the authorization header.

Finally, create the withAuth function that'll protect the API routes by wrapping the handlers:

export const withAuth = (handler) => {
  return (req, res) => {
    const { authorization } = req.headers
    if (!authorization)
      return res.status(401).json({ error: 'The authorization header is required' })
    const token = authorization.split(' ')[1]

    jwt.verify(token, JWT_KEY, (err, payload) => {
      if (err) return res.status(401).json({ error: 'Unauthorized' })
      req.auth = { user: payload }
      handler(req, res)
    })
  }
}

You can now modify pages/api/posts.js to include withAuth:

import { withAuth } from '../../auth_context'
import { users, posts } from '../../data'

export default withAuth((req, res) => {
  const { userId } = req.auth.user

  const userPosts = posts.filter((post) => {
    return post.userId == userId
  })

  res.status(200).json(userPosts)
})

Note that only the posts by the logged in user are returned. The logged in user is found through req.auth.user.

Let's now create the login page. First, add Formik and Yup. These are not strictly required but will help in creating the login form.

yarn add formik yup

Create pages/login.js:

import React from 'react'
import { Formik, ErrorMessage, Form, Field } from 'formik'
import * as Yup from 'yup'
import { useAuth } from '../auth_context'
import { useRouter } from 'next/router'
import api from '../api'

const LoginForm = () => {
  const { login } = useAuth()
  const router = useRouter()
  return (
    <Formik
      initialValues={{ username: '', password: '' }}
      validationSchema={Yup.object({
        username: Yup.string().required('Required'),
        password: Yup.string().required('Required'),
      })}
      onSubmit={async ({ username, password }, { setSubmitting, setErrors }) => {
        try {
          await login(username, password)
          setSubmitting(false)
          router.push('/posts')
        } catch (error) {
          const formikErrors = { password: error.response.data.error }
          setErrors(formikErrors)
          setSubmitting(false)
        }
      }}
    >
      {({ isSubmitting }) => (
        <Form>
          <div>
            <label>Username</label>
            <br />
            <Field name="username" type="text"></Field>
            <ErrorMessage name="username" component="p"></ErrorMessage>
          </div>
          <div>
            <label>Password</label>
            <br />
            <Field name="password" type="password"></Field>
            <ErrorMessage name="password" component="p"></ErrorMessage>
          </div>
          <button type="submit" disabled={isSubmitting}>
            Login
          </button>
        </Form>
      )}
    </Formik>
  )
}

export default LoginForm

This page uses the login function described above to log in the user.

Now update pages/posts.js to make use of AuthContext:

import { useEffect, useState } from 'react'
import api from '../api'
import { useAuth } from '../auth_context'

export default function Posts() {
  const [posts, setPosts] = useState(null)
  const { user, logout } = useAuth()
  console.log(user)
  useEffect(() => {
    async function fetchPosts() {
      const { data: postsList } = await api.get('api/posts')
      setPosts(postsList)
      console.log(postsList)
    }
    if (user) fetchPosts()
  }, [user])

  return (
    <>
      <ul>
        {posts?.map((post) => {
          return <li key={post.id}>{post.text}</li>
        })}
      </ul>
      <button onClick={logout}>Logout</button>
    </>
  )
}

Finally, update pages/_app.js to wrap everything in AuthProvider:

import '../styles/globals.css'
import { AuthProvider } from '../auth_context'

function MyApp({ Component, pageProps }) {
  return (
    <AuthProvider>
      <Component {...pageProps} />
    </AuthProvider>
  )
}

export default MyApp

Start the server with yarn dev and visit http://localhost:3000/login. Log in with the credentials (you can find the username in data.js and the password is "password") and you'll be redirected to the posts page. You can verify that you're only seeing posts from the logged in user.

The final app for this section can be found in the manual branch of the GitHub repo.

Authentication with Clerk

In this section, you'll replace the manual authentication with Clerk. Before starting with Clerk, you should revert the changes you've made so far. You can simply run git stash && git clean -fdx to stash your changes.

First, create an application in Clerk. You can keep all the default options.

Creating an application in Clerk

Once the application is created, go to the API keys page and copy the frontend API key, the backend API key, and the JWT verification key. Paste these into .env:

NEXT_PUBLIC_CLERK_FRONTEND_API=your_frontend_api_key
CLERK_API_KEY=your_backend_api_key
CLERK_JWT_KEY=your_jwt_key

Install the required library:

yarn add @clerk/nextjs

Wrap pages/_app.js with Clerkprovider:

import { ClerkProvider, SignedIn, SignedOut, RedirectToSignIn } from '@clerk/nextjs'
import { useRouter } from 'next/router'

const publicPages = ['/']

function MyApp({ Component, pageProps }) {
  const { pathname } = useRouter()
  const isPublicPage = publicPages.includes(pathname)

  return (
    <ClerkProvider {...pageProps}>
      {isPublicPage ? (
        <Component {...pageProps} />
      ) : (
        <>
          <SignedIn>
            <Component {...pageProps} />
          </SignedIn>
          <SignedOut>
            <RedirectToSignIn />
          </SignedOut>
        </>
      )}
    </ClerkProvider>
  )
}

export default MyApp

The publicPages array decides which pages will not be protected under authentication. For a protected page, if the user is not signed in, they will be redirected to the login page.

Create the file middleware.js in the project route:

import { withClerkMiddleware } from '@clerk/nextjs/server'
import { NextResponse } from 'next/server'

export default withClerkMiddleware((req) => {
  return NextResponse.next()
})

// Stop Middleware running on static files
export const config = { matcher: '/((?!.*\\.).*)' }

Modify pages/api/posts.js to include the getAuth function that authenticates the user with Clerk:

import { posts } from '../../data'
import { getAuth } from '@clerk/nextjs/server'

export default function handler(req, res) {
  const { userId } = getAuth(req)
  const userPosts = posts.filter((post) => {
    return post.userId == userId
  })

  res.status(200).json(userPosts)
}

In the Clerk dashboard, go to the Users page and create a test user.

Creating a new user

After the user is created, open the record and copy the ID as shown below.

Copying user ID

Open data.js and replace the numeric id field of any one user and the userId field in the posts array:

export const users = [
  {
    id: 'user_2IUxt1YsiCfebtlUwOe5dU91Det',
    username: 'bob',
    name: 'Bob',
    location: 'USA',
    password: '$2y$10$mj1OMFvVmGAR4gEEXZGtA.R5wYWBZTis72hSXzpxEs.QoXT3ifKSq',
  },
  // ...
]

export const posts = [
  {
    id: 1,
    userId: 'user_2IUxt1YsiCfebtlUwOe5dU91Det',
    text: 'Hello, World!',
  },
  // ...
  {
    id: 3,
    userId: 'user_2IUxt1YsiCfebtlUwOe5dU91Det',
    text: 'Lorem ipsum dolor sit amet. ',
  },
  // ...
]

Run the server again with yarn dev. Visit http://localhost:3000/posts and you should be redirected to Clerk's login page.

Clerk's login page

After logging in, you'll be redirected back to the /posts page. Verify that you can see only the posts corresponding to the logged in user.

The posts page

Conclusion

Protecting Next.js routes with authentication is a vital part of developing any web app. However, manually creating authentication mechanisms can be tedious and time-consuming. A solution like Clerk’s Next.js authentication comes with all the bells and whistles so that you don't need to worry about auth and can focus on the core app instead.

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Author
Aniket Bhattacharyea