How to invalidate a JWT token

Question

I'm using JWTs for user authentication, but I'm facing challenges in invalidating tokens before their expiration time, such as when a user logs out or a token needs to be revoked. Since JWTs are stateless and don’t have a built-in invalidation mechanism, what are the recommended methods for ensuring that a token can be invalidated effectively?

Any insights on common practices or practical examples of implementing JWT invalidation would be helpful.

Answer 1

To invalidate a JWT token effectively, here are some common methods:

1. Blacklist Tokens:

• Store invalidated tokens in a database or cache (e.g., Redis).
• Check this blacklist on each request to verify if the token is revoked.

const token = "user_jwt_token";
blacklist.add(token);

2. Token Versioning:

• Include a version or session_id in the user’s JWT claims.
• Store the current version/session ID in the database, updating it on logout or token reset.
• During authentication, compare the token’s version/session ID to the stored value.

if (tokenVersion !== storedTokenVersion) {
  throw new Error("Token invalidated");
}

3. Short Token Expiration with Refresh Tokens:

• Use short-lived access tokens and issue long-lived refresh tokens.
• Re-authenticate or reissue the token when the access token expires, requiring server validation.

const accessToken = generateAccessToken(user, { expiresIn: "15m" });

4. Revoke All Tokens by Updating User Secrets:

• Update a “secret” or “salt” stored in the user’s database record upon logout or revocation.
• Use this updated secret to sign new tokens, invalidating old ones.

const newSecret = generateNewSecret();

5. Use Token Revocation Lists in Auth Servers:

If using a centralized authentication server, leverage its built-in mechanisms for token revocation, which often include revocation lists or caches.

Comments

Token versioning is a robust solution, but it assumes a database lookup for every authentication request. You might want to discuss caching strategies or the trade-off between performance and security when implementing this method.