Custom Credential Provider with NextAuth.js

In this guide, we will explore how to implement a custom credential provider in NextAuth.js for user authentication using an email and password combination. This setup allows you to authenticate users against your own API endpoint.

Configuration Overview

To get started, ensure you have NextAuth.js installed in your Next.js application. You can do this by running:

npm install next-auth

Next, create or update your [...nextauth].js file in the pages/api/auth directory with the following configuration:

import NextAuth from 'next-auth';
import CredentialsProvider from 'next-auth/providers/credentials';
import axios from 'axios';

const YOUR_API_ENDPOINT = `${process.env.NEXT_PUBLIC_API_ROOT}auth/store`;

export default NextAuth({
  providers: [
    CredentialsProvider({
      name: 'Credentials',
      async authorize(credentials) {
        try {
          // Sending a POST request to the API endpoint with user credentials
          const response = await axios.post(YOUR_API_ENDPOINT, {
            username: credentials.email,
            password: credentials.password,
          }, {
            headers: {
              'Content-Type': 'application/json',
            },
          });

          // If the response contains user data, return it
          if (response.data) {
            return { status: 'success', data: response.data };
          }
        } catch (error) {
          // Handle errors and throw an error with a message
          const errorMessage = error.response?.data?.message || 'Login failed';
          throw new Error(`${errorMessage}&email=${credentials.email}`);
        }
      },
    }),
  ],
  callbacks: {
    async jwt(token, user) {
      // Store the access token in the JWT
      if (user) {
        token.accessToken = user.data.access_token;
      }
      return token;
    },
    async session(session, token) {
      // Attach the access token to the session
      session.accessToken = token.accessToken;

      // Fetch user data using the access token
      const config = {
        headers: { Authorization: `Bearer ${token.accessToken}` },
      };

      const userData = await axios.get('http://localhost:3000/api/user', config);
      session.user = userData.data;

      return session;
    },
  },
});

Explanation of the Code

  • Providers: We define a custom credential provider that accepts an email and password. The authorize method is responsible for authenticating the user by sending their credentials to the specified API endpoint.
  • Error Handling: If the authentication fails, an error is thrown with a message that can be displayed on the login page.
  • Callbacks: The jwt callback is used to store the access token in the JWT, while the session callback attaches the access token to the session and fetches additional user data from your API.

Conclusion

This setup allows you to authenticate users using a custom credential provider in NextAuth.js. Make sure to handle user data securely and consider implementing additional security measures, such as rate limiting and account lockout mechanisms, to protect against brute-force attacks.

Tags

  • NextAuth
  • Authentication
  • Next.js

Meta Description

Learn to implement custom email and password authentication using NextAuth.js in your Next.js application.