@labshare/express-jwt

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', algorithms: ['HS256'] }),
  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.

Required Parameters

The algorithms parameter is required to prevent potential downgrade attacks when providing third party libraries as secrets.

:warning: Do not mix symmetric and asymmetric (ie HS256/RS256) algorithms: Mixing algorithms without further validation can potentially result in downgrade vulnerabilities.

jwt({
  secret: 'shhhhhhared-secret',
  algorithms: ['HS256']
  //algorithms: ['RS256']
})

Additional Options

You can specify audience and/or issuer as well, which is highly recommended for security purposes:

jwt({
  secret: 'shhhhhhared-secret',
  audience: 'http://myapi/protected',
  issuer: 'http://issuer',
  algorithms: ['HS256']
})

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: Buffer.from('shhhhhhared-secret', 'base64'),
      algorithms: ['RS256'] })

Optionally you can make some paths unprotected as follows:

app.use(jwt({ secret: 'shhhhhhared-secret', algorithms: ['HS256']}).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, algorithms: ['RS256'] });

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, algorithms: ['RS256'], 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, algorithms: ['RS256'], 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 !',
  algorithms: ['HS256'],
  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, algorithms: ['HS256'] }),
  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',
    algorithms: ['HS256'],
    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 !',
  algorithms: ['HS256'],
  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.