AccessControl

© 2016, Onur Yıldırım (@onury). MIT License.

Role and Attribute based Access Control for Node.js

npm i accesscontrol

Many RBAC (Role-Based Access Control) implementations differ, but the basics is widely adopted since it simulates real life role (job) assignments. But while data is getting more and more complex; you need to define policies on resources, subjects or even environments. This is called ABAC (Attribute-Based Access Control).

With the idea of merging the best features of the two (see this NIST paper); this library implements RBAC basics and also focuses on resource and action attributes.

Core Features

• Role hierarchical inheritance.
• Define grants at once (e.g. from database result) or one by one.
• Grant/deny permissions by attributes defined by glob notation.
• Ability to filter data (model) instance by allowed attributes.
• Nested object support for attributes.
• Chainable, friendly API.

Guide

var AccessControl = require('accesscontrol');

Basic Example

Define roles and grants one by one.

var ac = new AccessControl();
ac.grant('user')                    // define new or modify existing role. also takes an array.
    .createOwn('video')             // equivalent to .createOwn('video', ['*'])
    .deleteOwn('video')
    .readAny('video')
  .grant('admin')                   // switch to another role without breaking the chain
    .extend('user')                 // inherit role capabilities. also takes an array
    .updateAny('video', ['title'])  // explicitly defined attributes
    .deleteAny('video');

var permission = ac.can('user').createOwn('video');
console.log(permission.granted);    // —> true
console.log(permission.attributes); // —> ['*'] (all attributes)

permission = ac.can('admin').updateAny('video');
console.log(permission.granted);    // —> true
console.log(permission.attributes); // —> ['title']

Express.js Example

Check role permissions for the requested resource and action, if granted; respond with filtered attributes.

var ac = new AccessControl(grants);
// ...
router.get('/videos/:title', function (req, res, next) {
    var permission = ac.can(req.user.role).readAny('video');
    if (permission.granted) {
        Video.find(req.params.title, function (err, data) {
            if (err || !data) return res.status(404).end();
            // filter data by permission attributes and send.
            res.json(permission.filter(data));
        });
    } else {
        // resource is forbidden for this user/role
        res.status(403).end();
    }
});

Roles

You can create/define roles simply by calling .grant(<role>) or .deny(<role>) methods on an AccessControl instance.

Roles can extend other roles.

// user role inherits viewer role permissions
ac.grant('user').extend('viewer');
// admin role inherits both user and editor role permissions
ac.grant('admin').extend(['user', 'editor']);
// both admin and superadmin roles inherit moderator permissions
ac.grant(['admin', 'superadmin']).extend('moderator');

Actions and Action-Attributes

CRUD operations are the actions you can perform on a resource. There are two action-attributes which define the possession of the resource: own and any.

For example, an admin role can create, read, update or delete (CRUD) any account resource. But a user role might only read or update its own account resource.

Action	Possession
Create Read Update Delete	Own	The C|R|U|D action is (or not) to be performed on own resource(s) of the current subject.
	Any	The C|R|U|D action is (or not) to be performed on any resource(s); including own.

ac.grant('role').readOwn('resource');
ac.deny('role').deleteAny('resource');

Resources and Resource-Attributes

Multiple roles can have access to a specific resource. But depending on the context, you may need to limit the contents of the resource for specific roles.

This is possible by resource attributes. You can use Glob notation to define allowed or denied attributes.

For example, we have a video resource that has the following attributes: id, title and runtime. All attributes of any video resource can be read by an admin role:

ac.grant('admin').readAny('video', ['*']);
// equivalent to:
// ac.grant('admin').readAny('video');

But the id attribute should not be read by a user role.

ac.grant('user').readOwn('video', ['*', '!id']);
// equivalent to:
// ac.grant('user').readOwn('video', ['title', 'runtime']);

You can also use nested objects (attributes).

ac.grant('user').readOwn('account', ['*', '!record.id']);

Checking Permissions and Filtering Attributes

You can call .can(<role>).<action>(<resource>) on an AccessControl instance to check for granted permissions for a specific resource and action.

var permission = ac.can('user').readOwn('account');
permission.granted;       // true
permission.attributes;    // ['*', '!record.id']
permission.filter(data);  // filtered data (without record.id)

See express.js example.

Defining All Grants at Once

You can pass the grants directly to the AccessControl constructor. It accepts either an Object:

// This is actually how the grants are maintained internally.
var grantsObject = {
    admin: {
        video: {
            'create:any': ['*'],
            'read:any': ['*'],
            'update:any': ['*'],
            'delete:any': ['*']
        }
    },
    user: {
        video: {
            'create:own': ['*'],
            'read:own': ['*'],
            'update:own': ['*'],
            'delete:own': ['*']
        }
    }
};
var ac = new AccessControl(grantsObject);

... or an Array (useful when fetched from a database):

// grant list fetched from DB (to be converted to a valid grants object, internally)
var grantList = [
    { role: 'admin', resource: 'video', action: 'create:any', attributes: ['*'] },
    { role: 'admin', resource: 'video', action: 'read:any', attributes: ['*'] },
    { role: 'admin', resource: 'video', action: 'update:any', attributes: ['*'] },
    { role: 'admin', resource: 'video', action: 'delete:any', attributes: ['*'] },

    { role: 'user', resource: 'video', action: 'create:own', attributes: ['*'] },
    { role: 'user', resource: 'video', action: 'read:any', attributes: ['*'] },
    { role: 'user', resource: 'video', action: 'update:own', attributes: ['*'] },
    { role: 'user', resource: 'video', action: 'delete:own', attributes: ['*'] }
];
var ac = new AccessControl(grantList);

You can set/get grants any time:

var ac = new AccessControl();
ac.setGrants(grantsObject);
console.log(ac.getGrants());

Documentation

You can read the full API reference here.

Change-Log

v1.0.0 (2016-09-10)

• initial release.

License

MIT.