Npm JWT Libraries

When are JWT Libraries useful?

JSON Web Tokens (JWT) libraries are highly useful when there is a need to securely transmit information between parties in a compact, URL-safe manner. This information can be verified and trusted as it is digitally signed. JWT libraries are particularly beneficial in the following scenarios:

• Authentication: After the user is logged in, each subsequent request will include the JWT, allowing the user to access routes, services, and resources permitted with that token. This makes session state completely unnecessary on the server side.

• Information Exchange: JWTs are a good way of securely transmitting information between users securely. Because they can be signed—for example, using a public/private key pair—you can be sure the senders are who they claim to be.

What Functionalities do JWT Libraries Usually Have?

JWT libraries offer a suite of functionalities that allow for easy generation, verification, and management of JWTs. Here is an overview of the standard functionalities:

• Token Generation: The core functionality of JWT libraries is the capability to create new tokens. These tokens can have custom payloads that are signed with a private key.

• Token Verification: JWT libraries typically include functions to verify tokens, checking the signature with a public key and ensuring the payload has not been tampered with.

• Token Decoding: If you need to inspect a token without verifying it, JWT libraries will generally present decode functions.

• Claims Checking: Most libraries offer a way to check standard claims in tokens such as iss, exp, sub, etc. This can be used to validate if the token has expired, to verify the issuer, and so on.

Gotchas/Pitfalls to Look Out For

Using JWTs and JWT libraries are not without their challenges. Here are some pitfalls to be aware of:

• Token Storage: Storing JWTs securely is a challenge. If stored in local storage, they are vulnerable to XSS attacks. Conversely, if stored in cookies, they are susceptible to CSRF attacks.

• Token Expiration: It's important to set an expiration time for your tokens. Tokens that don't expire can pose a security risk if they fall into the wrong hands.

• No State: JWTs are stateless. This means if a token is stolen, it can be used as long as it's valid. There is no universal way to revoke tokens.

• Package Selection: Not all JWT libraries are created equal, and some may be better suited for your needs than others. Always make sure to review the documentation and updates when using npm packages to ensure they are still being maintained and that there are no known security issues.