Node Js: JWT best practices

Using JWTs(json web tokens) for authentication is common but certain best practices should be followed to ensure the security of your application. Here are some of them:

1. Keep JWTs Short-lived: It's crucial to ensure that your JWTs have a short lifespan to reduce the risk if a token is compromised. A common strategy is to use a refresh token, which can be kept in a secure, httpOnly, sameSite cookie, and can be used to generate a new JWT when the old one expires.

2. Use Strong Secret Keys: The secret key used to sign the JWT should be long and complex to prevent brute force attacks. For even better security, consider using asymmetric encryption (with RS256, ES256, etc.) where a private key is used to sign the token and a public key is used to verify it.

3. Don't Store Sensitive Data: Avoid storing sensitive information in the payload of a JWT. Even though the information is encoded, it can be easily decoded since JWTs are not encrypted.

4. Use HttpOnly Cookies: Consider storing JWTs in HttpOnly cookies, as opposed to local storage or session storage in the browser, to protect against XSS attacks.

5. Use Secure Cookies: If your application is served over HTTPS, make sure to set the Secure flag for cookies which ensures that the cookie is only sent over an HTTPS connection.

6. Use SameSite Cookies: The SameSite attribute can help to protect against CSRF attacks. With SameSite=Lax, the cookie is only sent with same-site requests or with navigational requests (like clicking a link). With SameSite=Strict, the cookie is only sent with same-site requests.

7. Handle Token Expiration: Make sure your application handles token expiration appropriately. The user should be logged out or a new token should be issued when the old token expires.

8. Use Appropriate Error Handling: Ensure your application handles errors correctly. If a token is invalid or expired, the server should respond with a 401 Unauthorized status code.

9. Use Middleware for Protected Routes: In Node.js, you can use middleware to protect routes that should only be accessible with a valid token.

10. Rotate Refresh Tokens: Whenever a refresh token is used to get a new access token, invalidate the old refresh token and issue a new one. This way, if a refresh token is stolen, it will be usable only once.

This is by no means an exhaustive list of all the best practices and the right measures depend on the specifics of your application and its threat model. It's also a good idea to stay updated on the latest security best practices and vulnerabilities related to JWTs.