How do you secure JWT tokens in your front-end applications?

1 Choose a secure storage option

One of the most important decisions you have to make is where to store your JWT tokens in the browser. There are three common options: local storage, session storage, and cookies. Each one has its pros and cons, but none of them is completely safe from attacks. Local storage and session storage are vulnerable to cross-site scripting (XSS) attacks, where malicious scripts can access and steal your tokens. Cookies are vulnerable to cross-site request forgery (CSRF) attacks, where malicious requests can use your tokens without your consent. To mitigate these risks, you should choose a storage option that suits your use case, use secure and http-only flags for cookies, and implement anti-CSRF measures.

2 Use short expiration times

Another way to secure your JWT tokens is to use short expiration times. This means that your tokens will become invalid after a certain period of time, reducing the window of opportunity for attackers to use them. You can set the expiration time in the payload of your JWT token, using the exp claim. The value of the exp claim should be a numeric date in seconds since the epoch. For example, if you want your token to expire in 15 minutes, you can set the exp claim to the current time plus 900 seconds. However, using short expiration times also means that you have to refresh your tokens more often, which can affect the user experience and the performance of your application.

3 Use token revocation and blacklisting

Sometimes, you may need to invalidate your JWT tokens before they expire. For example, if a user logs out, changes their password, or reports a security breach, you want to revoke their tokens and prevent them from being used again. However, JWT tokens are stateless, meaning that they do not depend on a server-side session or database to check their validity. Therefore, you need to implement a token revocation and blacklisting mechanism in your application. This can be done by using a separate storage, such as a database or a cache, to keep track of the tokens that have been revoked or blacklisted. Then, you need to check this storage every time you verify a token, and reject it if it is on the list.

4 Use HTTPS and secure headers

Another essential aspect of securing your JWT tokens is to use HTTPS and secure headers. HTTPS is a protocol that encrypts the communication between your browser and your server, preventing anyone from intercepting or tampering with your data. Secure headers are additional information that you can send with your requests and responses, to instruct the browser how to handle your data. For example, you can use the Content-Security-Policy header to restrict the sources of scripts, styles, and images that can be loaded on your page, reducing the risk of XSS attacks. You can also use the Strict-Transport-Security header to enforce HTTPS on your site, preventing downgrade attacks.