jsonwebtoken

What is jsonwebtoken?

The jsonwebtoken npm package is used to implement JSON Web Tokens (JWT) in Node.js applications. JWTs are a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted.

What are jsonwebtoken's main functionalities?

Token Signing

This feature allows you to create a digitally signed token. The token consists of a header, a payload, and a signature. The header typically consists of two parts: the type of the token, which is JWT, and the signing algorithm being used, such as HMAC SHA256 or RSA.

{"alg":"HS256","typ":"JWT"}.eyJsub":"1234567890","name":"John Doe","admin":true}.[signature]

Token Verification

This feature is used to verify the signature of an incoming JWT token to ensure that the sender is who they say they are and to ensure that the message wasn't changed along the way.

jwt.verify(token, 'secret', function(err, decoded) { console.log(decoded.foo) // bar })

Token Decoding

This feature allows you to decode a JWT without verifying it. This is useful for cases where you trust the token or have already verified it and just need to read the payload.

jwt.decode(token)

Other packages similar to jsonwebtoken

passport-jwt

A Passport strategy for authenticating with a JSON Web Token. This module lets you authenticate endpoints using a JWT. It is designed to be used with Passport.js. While jsonwebtoken is used for creating and verifying tokens, passport-jwt is used in the context of a web application to protect routes.

jose

JOSE is a comprehensive set of JWT, JWS, and JWE libraries. Compared to jsonwebtoken, it supports a wider range of algorithms and capabilities, including encryption. It is a more complex library that can be used for a broader set of use cases.

README

jsonwebtoken

An implementation of JSON Web Tokens.

This was developed against draft-ietf-oauth-json-web-token-08. It makes use of node-jws

Install

$ npm install jsonwebtoken

Usage

jwt.sign(payload, secretOrPrivateKey, [options, callback])

(Asynchronous) If a callback is supplied, callback is called with the err or the JWT.

(Synchronous) Returns the JsonWebToken as string

payload could be an object literal, buffer or string. Please note that exp is only set if the payload is an object literal.

secretOrPrivateKey is a string, buffer, or object containing either the secret for HMAC algorithms or the PEM encoded private key for RSA and ECDSA. In case of a private key with passphrase an object { key, passphrase } can be used (based on crypto documentation), in this case be sure you pass the algorithm option.

options:

• algorithm (default: HS256)
• expiresIn: expressed in seconds or a string describing a time span zeit/ms. Eg: 60, "2 days", "10h", "7d"
• notBefore: expressed in seconds or a string describing a time span zeit/ms. Eg: 60, "2 days", "10h", "7d"
• audience
• issuer
• jwtid
• subject
• noTimestamp
• header
• keyid

If payload is not a buffer or a string, it will be coerced into a string using JSON.stringify.

There are no default values for expiresIn, notBefore, audience, subject, issuer. These claims can also be provided in the payload directly with exp, nbf, aud, sub and iss respectively, but you can't include in both places.

Remember that exp, nbf and iat are NumericDate, see related Token Expiration (exp claim)

The header can be customized via the option.header object.

Generated jwts will include an iat (issued at) claim by default unless noTimestamp is specified. If iat is inserted in the payload, it will be used instead of the real timestamp for calculating other things like exp given a timespan in options.expiresIn.

Example

// sign with default (HMAC SHA256)
var jwt = require('jsonwebtoken');
var token = jwt.sign({ foo: 'bar' }, 'shhhhh');
//backdate a jwt 30 seconds
var older_token = jwt.sign({ foo: 'bar', iat: Math.floor(Date.now() / 1000) - 30 }, 'shhhhh');

// sign with RSA SHA256
var cert = fs.readFileSync('private.key');  // get private key
var token = jwt.sign({ foo: 'bar' }, cert, { algorithm: 'RS256'});

// sign asynchronously
jwt.sign({ foo: 'bar' }, cert, { algorithm: 'RS256' }, function(err, token) {
  console.log(token);
});

Token Expiration (exp claim)

The standard for JWT defines an exp claim for expiration. The expiration is represented as a NumericDate:

A JSON numeric value representing the number of seconds from 1970-01-01T00:00:00Z UTC until the specified UTC date/time, ignoring leap seconds. This is equivalent to the IEEE Std 1003.1, 2013 Edition [POSIX.1] definition "Seconds Since the Epoch", in which each day is accounted for by exactly 86400 seconds, other than that non-integer values can be represented. See RFC 3339 [RFC3339] for details regarding date/times in general and UTC in particular.

This means that the exp field should contain the number of seconds since the epoch.

Signing a token with 1 hour of expiration:

jwt.sign({
  exp: Math.floor(Date.now() / 1000) + (60 * 60),
  data: 'foobar'
}, 'secret');

Another way to generate a token like this with this library is:

jwt.sign({
  data: 'foobar'
}, 'secret', { expiresIn: 60 * 60 });

//or even better:

jwt.sign({
  data: 'foobar'
}, 'secret', { expiresIn: '1h' });

jwt.verify(token, secretOrPublicKey, [options, callback])

(Asynchronous) If a callback is supplied, function acts asynchronously. Callback is passed the decoded payload if the signature and optional expiration, audience, or issuer are valid. If not, it will be passed the error.

(Synchronous) If a callback is not supplied, function acts synchronously. Returns the payload decoded if the signature (and, optionally, expiration, audience, issuer) are valid. If not, it will throw the error.

token is the JsonWebToken string

secretOrPublicKey is a string or buffer containing either the secret for HMAC algorithms, or the PEM encoded public key for RSA and ECDSA.

As mentioned in this comment, there are other libraries that expect base64 encoded secrets (random bytes encoded using base64), if that is your case you can pass new Buffer(secret, 'base64'), by doing this the secret will be decoded using base64 and the token verification will use the original random bytes.

options

• algorithms: List of strings with the names of the allowed algorithms. For instance, ["HS256", "HS384"].
• audience: if you want to check audience (aud), provide a value here
• issuer (optional): string or array of strings of valid values for the iss field.
• ignoreExpiration: if true do not validate the expiration of the token.
• ignoreNotBefore...
• subject: if you want to check subject (sub), provide a value here
• clockTolerance: number of seconds to tolerate when checking the nbf and exp claims, to deal with small clock differences among different servers
• maxAge: the maximum allowed age for tokens to still be valid. Currently it is expressed in milliseconds or a string describing a time span zeit/ms. Eg: 1000, "2 days", "10h", "7d". We advise against using milliseconds precision, though, since JWTs can only contain seconds. The maximum precision might be reduced to seconds in the future.
• clockTimestamp: the time in seconds that should be used as the current time for all necessary comparisons (also against maxAge, so our advise is to avoid using clockTimestamp and a maxAge in milliseconds together)

// verify a token symmetric - synchronous
var decoded = jwt.verify(token, 'shhhhh');
console.log(decoded.foo) // bar

// verify a token symmetric
jwt.verify(token, 'shhhhh', function(err, decoded) {
  console.log(decoded.foo) // bar
});

// invalid token - synchronous
try {
  var decoded = jwt.verify(token, 'wrong-secret');
} catch(err) {
  // err
}

// invalid token
jwt.verify(token, 'wrong-secret', function(err, decoded) {
  // err
  // decoded undefined
});

// verify a token asymmetric
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, function(err, decoded) {
  console.log(decoded.foo) // bar
});

// verify audience
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo' }, function(err, decoded) {
  // if audience mismatch, err == invalid audience
});

// verify issuer
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo', issuer: 'urn:issuer' }, function(err, decoded) {
  // if issuer mismatch, err == invalid issuer
});

// verify jwt id
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo', issuer: 'urn:issuer', jwtid: 'jwtid' }, function(err, decoded) {
  // if jwt id mismatch, err == invalid jwt id
});

// verify subject
var cert = fs.readFileSync('public.pem');  // get public key
jwt.verify(token, cert, { audience: 'urn:foo', issuer: 'urn:issuer', jwtid: 'jwtid', subject: 'subject' }, function(err, decoded) {
  // if subject mismatch, err == invalid subject
});

// alg mismatch
var cert = fs.readFileSync('public.pem'); // get public key
jwt.verify(token, cert, { algorithms: ['RS256'] }, function (err, payload) {
  // if token alg != RS256,  err == invalid signature
});

jwt.decode(token [, options])

(Synchronous) Returns the decoded payload without verifying if the signature is valid.

Warning: This will not verify whether the signature is valid. You should not use this for untrusted messages. You most likely want to use jwt.verify instead.

token is the JsonWebToken string

options:

• json: force JSON.parse on the payload even if the header doesn't contain "typ":"JWT".
• complete: return an object with the decoded payload and header.

Example

// get the decoded payload ignoring signature, no secretOrPrivateKey needed
var decoded = jwt.decode(token);

// get the decoded payload and header
var decoded = jwt.decode(token, {complete: true});
console.log(decoded.header);
console.log(decoded.payload)

Errors & Codes

Possible thrown errors during verification. Error is the first argument of the verification callback.

TokenExpiredError

Thrown error if the token is expired.

Error object:

• name: 'TokenExpiredError'
• message: 'jwt expired'
• expiredAt: [ExpDate]

jwt.verify(token, 'shhhhh', function(err, decoded) {
  if (err) {
    /*
      err = {
        name: 'TokenExpiredError',
        message: 'jwt expired',
        expiredAt: 1408621000
      }
    */
  }
});

JsonWebTokenError

Error object:

• name: 'JsonWebTokenError'
• message:
  • 'jwt malformed'
  • 'jwt signature is required'
  • 'invalid signature'
  • 'jwt audience invalid. expected: [OPTIONS AUDIENCE]'
  • 'jwt issuer invalid. expected: [OPTIONS ISSUER]'
  • 'jwt id invalid. expected: [OPTIONS JWT ID]'
  • 'jwt subject invalid. expected: [OPTIONS SUBJECT]'

jwt.verify(token, 'shhhhh', function(err, decoded) {
  if (err) {
    /*
      err = {
        name: 'JsonWebTokenError',
        message: 'jwt malformed'
      }
    */
  }
});

Algorithms supported

Array of supported algorithms. The following algorithms are currently supported.

alg Parameter Value	Digital Signature or MAC Algorithm
HS256	HMAC using SHA-256 hash algorithm
HS384	HMAC using SHA-384 hash algorithm
HS512	HMAC using SHA-512 hash algorithm
RS256	RSASSA using SHA-256 hash algorithm
RS384	RSASSA using SHA-384 hash algorithm
RS512	RSASSA using SHA-512 hash algorithm
ES256	ECDSA using P-256 curve and SHA-256 hash algorithm
ES384	ECDSA using P-384 curve and SHA-384 hash algorithm
ES512	ECDSA using P-521 curve and SHA-512 hash algorithm
none	No digital signature or MAC value included

Refreshing JWTs

First of all, we recommend to think carefully if auto-refreshing a JWT will not introduce any vulnerability in your system.

We are not comfortable including this as part of the library, however, you can take a look to this example to show how this could be accomplish. Apart from that example there are an issue and a pull request to get more knowledge about this topic.

TODO

• X.509 certificate chain is not checked

Issue Reporting

If you have found a bug or if you have a feature request, please report them at this repository issues section. Please do not report security vulnerabilities on the public GitHub issue tracker. The Responsible Disclosure Program details the procedure for disclosing security issues.

Author

Auth0

License

This project is licensed under the MIT license. See the LICENSE file for more info.

Changelog

7.4.3 - 2017-08-17

• Fix breaking change on 7.4.2 for empty secret + "none" algorithm (sync code style) (PR 386)