express-jwt

What is express-jwt?

The express-jwt package is a middleware for Express.js that allows you to validate JSON Web Tokens (JWTs) in your HTTP requests. It is commonly used for securing routes and ensuring that only authenticated users can access certain endpoints.

What are express-jwt's main functionalities?

JWT Validation

This feature allows you to validate JWTs in incoming requests. The middleware checks the token's validity and ensures it is signed with the correct secret key and algorithm.

const express = require('express');
const jwt = require('express-jwt');
const app = express();

const jwtMiddleware = jwt({
  secret: 'your-secret-key',
  algorithms: ['HS256']
});

app.use('/protected', jwtMiddleware, (req, res) => {
  res.send('This is a protected route');
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Error Handling

This feature allows you to handle errors that occur during JWT validation. For example, you can send a 401 Unauthorized response if the token is invalid.

const express = require('express');
const jwt = require('express-jwt');
const app = express();

const jwtMiddleware = jwt({
  secret: 'your-secret-key',
  algorithms: ['HS256']
});

app.use('/protected', jwtMiddleware, (err, req, res, next) => {
  if (err.name === 'UnauthorizedError') {
    res.status(401).send('Invalid token');
  } else {
    next(err);
  }
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Token Decoding

This feature allows you to decode the JWT and attach the payload to the request object. You can then access the decoded information in your route handlers.

const express = require('express');
const jwt = require('express-jwt');
const app = express();

const jwtMiddleware = jwt({
  secret: 'your-secret-key',
  algorithms: ['HS256'],
  requestProperty: 'auth'
});

app.use('/protected', jwtMiddleware, (req, res) => {
  res.send(`Hello, ${req.auth.name}`);
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Other packages similar to express-jwt

jsonwebtoken

The jsonwebtoken package is a popular library for creating and verifying JSON Web Tokens. Unlike express-jwt, it does not provide middleware for Express.js, but it offers more flexibility for handling tokens in various contexts.

passport-jwt

The passport-jwt package is a Passport.js strategy for authenticating with a JSON Web Token. It integrates with Passport.js, a popular authentication middleware for Node.js, and provides more comprehensive authentication solutions compared to express-jwt.

koa-jwt

The koa-jwt package is similar to express-jwt but is designed for Koa.js applications. It provides middleware for validating JWTs in Koa.js, making it a suitable alternative for developers using the Koa framework.

README

express-jwt

This module provides Express middleware for validating JWTs (JSON Web Tokens) through the jsonwebtoken module. The decoded JWT payload is available on the request object.

Install

$ npm install express-jwt

Usage

Basic usage using an HS256 secret:

var jwt = require('express-jwt');

app.get('/protected',
  jwt({ secret: 'shhhhhhared-secret' }),
  function(req, res) {
    if (!req.user.admin) return res.sendStatus(401);
    res.sendStatus(200);
  });

The decoded JWT payload is available on the request via the user property. This can be configured using the requestProperty option (see below).

The default behavior of the module is to extract the JWT from the Authorization header as an OAuth2 Bearer token.

Additional Options

You can specify audience and/or issuer as well:

jwt({
  secret: 'shhhhhhared-secret',
  audience: 'http://myapi/protected',
  issuer: 'http://issuer'
})

If the JWT has an expiration (exp), it will be checked.

If you are using a base64 URL-encoded secret, pass a Buffer with base64 encoding as the secret instead of a string:

jwt({ secret: new Buffer('shhhhhhared-secret', 'base64') })

Optionally you can make some paths unprotected as follows:

app.use(jwt({ secret: 'shhhhhhared-secret'}).unless({path: ['/token']}));

This is especially useful when applying to multiple routes. In the example above, path can be a string, a regexp, or an array of any of those.

For more details on the .unless syntax including additional options, please see express-unless.

This module also support tokens signed with public/private key pairs. Instead of a secret, you can specify a Buffer with the public key

var publicKey = fs.readFileSync('/path/to/public.pub');
jwt({ secret: publicKey });

Retrieving the Decoded Payload

By default, the decoded token is attached to req.user but can be configured with the requestProperty option.

jwt({ secret: publicKey, requestProperty: 'auth' });

The token can also be attached to the result object with the resultProperty option. This option will override any requestProperty.

jwt({ secret: publicKey, resultProperty: 'locals.user' });

Both resultProperty and requestProperty utilize lodash.set and will accept nested property paths.

Customizing Token Location

A custom function for extracting the token from a request can be specified with the getToken option. This is useful if you need to pass the token through a query parameter or a cookie. You can throw an error in this function and it will be handled by express-jwt.

app.use(jwt({
  secret: 'hello world !',
  credentialsRequired: false,
  getToken: function fromHeaderOrQuerystring (req) {
    if (req.headers.authorization && req.headers.authorization.split(' ')[0] === 'Bearer') {
        return req.headers.authorization.split(' ')[1];
    } else if (req.query && req.query.token) {
      return req.query.token;
    }
    return null;
  }
}));

Multi-tenancy

If you are developing an application in which the secret used to sign tokens is not static, you can provide a callback function as the secret parameter. The function has the signature: function(req, payload, done):

• req (Object) - The express request object.
• payload (Object) - An object with the JWT claims.
• done (Function) - A function with signature function(err, secret) to be invoked when the secret is retrieved.
  • err (Any) - The error that occurred.
  • secret (String) - The secret to use to verify the JWT.

For example, if the secret varies based on the JWT issuer:

var jwt = require('express-jwt');
var data = require('./data');
var utilities = require('./utilities');

var secretCallback = function(req, payload, done){
  var issuer = payload.iss;

  data.getTenantByIdentifier(issuer, function(err, tenant){
    if (err) { return done(err); }
    if (!tenant) { return done(new Error('missing_secret')); }

    var secret = utilities.decrypt(tenant.secret);
    done(null, secret);
  });
};

app.get('/protected',
  jwt({ secret: secretCallback }),
  function(req, res) {
    if (!req.user.admin) return res.sendStatus(401);
    res.sendStatus(200);
  });

Revoked tokens

It is possible that some tokens will need to be revoked so they cannot be used any longer. You can provide a function as the isRevoked option. The signature of the function is function(req, payload, done):

• req (Object) - The express request object.
• payload (Object) - An object with the JWT claims.
• done (Function) - A function with signature function(err, revoked) to be invoked once the check to see if the token is revoked or not is complete.
  • err (Any) - The error that occurred.
  • revoked (Boolean) - true if the JWT is revoked, false otherwise.

For example, if the (iss, jti) claim pair is used to identify a JWT:

var jwt = require('express-jwt');
var data = require('./data');
var utilities = require('./utilities');

var isRevokedCallback = function(req, payload, done){
  var issuer = payload.iss;
  var tokenId = payload.jti;

  data.getRevokedToken(issuer, tokenId, function(err, token){
    if (err) { return done(err); }
    return done(null, !!token);
  });
};

app.get('/protected',
  jwt({
    secret: 'shhhhhhared-secret',
    isRevoked: isRevokedCallback
  }),
  function(req, res) {
    if (!req.user.admin) return res.sendStatus(401);
    res.sendStatus(200);
  }
);

Error handling

The default behavior is to throw an error when the token is invalid, so you can add your custom logic to manage unauthorized access as follows:

app.use(function (err, req, res, next) {
  if (err.name === 'UnauthorizedError') {
    res.status(401).send('invalid token...');
  }
});

You might want to use this module to identify registered users while still providing access to unregistered users. You can do this by using the option credentialsRequired:

app.use(jwt({
  secret: 'hello world !',
  credentialsRequired: false
}));

Related Modules

• jsonwebtoken — JSON Web Token sign and verification
• express-jwt-permissions - Permissions middleware for JWT tokens

Tests

$ npm install
$ npm test

Contributors

Check them out here

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.