express-ramses-auth

Express implementation of RAMSES - Robust Access Model for Securing Exposed Services

1. Introduction
2. Installation
3. Usage
4. Testing
5. Contribution
6. License

Introduction

RAMSES is an easily adoptable, customizable and robust security model which will not consider any trusted zones. It proposes an authentication and authorization pattern for inter-service communication utilizing and extending JSON Web Signatures (JWS) as tickets. RAMSES includes various extensions for individual security levels and requirements, like access capabilities, ticket invalidation, usage limitation and payload encryption.

A detailed explanation of RAMSES will follow.

This library copied a lot of code from this awesome library express-jwt.

Installation

For installation use the Node Package Manager:

$ npm install --save express-ramses-auth

or clone the repository:

$ git clone https://github.com/KorbinianKuhn/express-ramses-auth

Usage

The RAMSES authentication middleware authenticates callers using a JWT. If the token is valid, req.user will be set with the decoded JSON object to be used by later middleware for authorization and access control.

For example,

const ramses = require('express-ramses-auth');
const publicKey = fs.readFileSync('/path/to/public.pub');
 
app.get('/protected',
  ramses({key: publicKey}),
  function(req, res) {
    if (!req.user) return res.sendStatus(401);
    res.sendStatus(200);
  });

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

ramses({ key: publicKey, requestProperty: 'auth' });

The token can also be attached to the result object with the resultProperty option.

ramses({ key: publicKey, resultProperty: 'locals.user' });

The full decoded token (header, payload and signature) can be attached with the attachFullToken option.

ramses({ key: publicKey, attachFullToken: true });

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

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-ramses-auth.

app.use(ramses({
  key: publicKey,
  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 key used to sign tokens is not static, you can provide a callback function as the key parameter. The function has the signature: function(req, dtoken):

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

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

const ramses = require('express-ramses-auth');
const data = require('./data');
const utilities = require('./utilities');
 
const keyCallback = function(req, dtoken, done){
  const issuer = dtoken.payload.iss;
 
  data.getTenantByIdentifier(issuer, function(err, tenant){
    if (err) { return done(err); }
    if (!tenant) { return done(new Error('missing_key')); }
 
    const key = utilities.decrypt(tenant.key);
    done(null, key);
  });
};
 
app.get('/protected',
  ramses({key: keyCallback}),
  function(req, res) {
    if (!req.user) return res.sendStatus(401);
    res.sendStatus(200);
  });

Optionally you can make some paths unprotected as follows:

app.use(ramses({ key: publicKey}).unless({path: ['/skip']}));

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.

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.
• dtoken (Object) - An object with the decoded JWT header, payload and signature.
• 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:

const ramses = require('express-ramses-auth');
const data = require('./data');
const utilities = require('./utilities');
 
const isRevokedCallback = function(req, dtoken, done){
  const issuer = dtoken.payload.iss;
  const tokenId = dtoken.payload.jti;
 
  data.getRevokedToken(issuer, tokenId, function(err, token){
    if (err) { return done(err); }
    return done(null, !!token);
  });
};
 
app.get('/protected',
  ramses({key: publicKey,
    isRevoked: isRevokedCallback}),
  function(req, res) {
    if (!req.user) 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(ramses({
  key: publicKey,
  credentialsRequired: false
}));

Ticket validation

The middleware maps all options of the ramses-auth package:

aud (String): Audience that must be part of the aud claim. azp (String): Authorized party that must be part of the azp claim.

RAMSES functions

The middleware exports all functions of the ramses-auth package:

• sign(payload, key, options, callback)
• verify(ticket, key, options, callback)
• decode(ticket, options)

Proof of possession

The middleware provides two functions to create and verify a proof of possession, that is necessary to create an AccessTicket from an AccessTicket. As RAMSES specifies, the jti claim should of the ticket shoud be signed with the services private key.

ramses.createProof(message, key, function(err, proof) {
  console.log(proof);
});
 
ramses.createProof(message, proof, key, function(err, valid) {
  console.log(valid);
});

Testing

First you have to install all dependencies:

$ npm install

To execute all unit tests once, use:

$ npm test

To get information about the test coverage, use:

$ npm run coverage

Contribution

Fork this repository and push in your ideas.

Do not forget to add corresponding tests to keep up 100% test coverage.

License

The MIT License

Copyright (c) 2017 Korbinian Kuhn, Tobias Eberle, Christof Kost, Steffen Mauser, Marc Schelling

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.