CASL (pronounced /ˈkæsəl/, like castle) is an isomorphic authorization JavaScript library which restricts what resources a given user is allowed to access. It's designed to be incrementally adoptable and can easily scale between a simple claim based and fully featured subject and attribute based authorization. It makes it easy to manage and share permissions across UI components, API services, and database queries.
Heavily inspired by cancan.
- Versatile
An incrementally adoptable and can easily scale between a simple claim based and fully featured subject and attribute based authorization. - Isomorphic
Can be used on frontend and backend and complementary packages make integration with major Frontend Frameworks and Backend ORMs effortless - TypeSafe
Written in TypeScript, what makes your apps safer and developer experience more enjoyable - Tree shakable
The core is only 4KB mingzipped and can be even smaller! - Declarative
Thanks to declarative rules, you can serialize and share permissions between UI and API or microservices
Project | Status | Description | Supported envinronemnts |
---|---|---|---|
@casl/ability | CASL's core package | nodejs 8+ and ES5 compatible browsers (IE 9+) | |
@casl/mongoose | integration with Mongoose | nodejs 8+ | |
@casl/angular | integration with Angular | IE 9+ | |
@casl/react | integration with React | IE 9+ | |
@casl/vue | integration with Vue | IE 11+ (uses WeakMap ) |
|
@casl/aurelia | integration with Aurelia | IE 11+ (uses WeakMap ) |
A lot of detailed information about CASL, integrations and examples can be found in documentation.
Ask it in chat or on stackoverflow. Please don't ask questions in issues, the issue list of this repo is exclusively for bug reports and feature requests. Questions in the issue list may be closed immediately without answers.
CASL operates on the abilities level, that is what a user can actually do in the application. An ability itself depends on the 4 parameters (last 3 are optional):
- User Action
Describes what user can actually do in the app. User action is a word (usually a verb) which depdends on the business logic (e.g.,prolong
,read
). Very often it will be a list of words from CRUD -create
,read
,update
anddelete
. - Subject
The subject or subject type which you want to check user action on. Ussually this is a business (or domain) entity name (e.g.,Subscription
,BlogPost
,User
). - Conditions
An object or function which restricts user action only to matched subjects. This is useful when you need to give a permission on resources created by a user (e.g., to allow user to update and delete ownBlogPost
) - Fields
Can be used to restrict user action only to matched subject's fields (e.g., to allow moderator to updatehidden
field ofBlogPost
but not updatedesription
ortitle
)
Using CASL you can describe abilities using regular and inverted rules. Let's see how
Note: all the examples below will be written in TypeScript but CASL can be used in similar way in ES6+ and Nodejs environments.
Lets define Ability
for a blog website where visitors:
- can read blog posts
- can manage (i.e., do anything) own posts
- cannot delete a post if it was created more than a day ago
import { AbilityBuilder, Ability } from '@casl/ability'
import { User } from '../models'; // application specific interfaces
/**
* @param user contains details about logged in user: its id, name, email, etc
*/
function defineAbilitiesFor(user: User) {
const { can, cannot, rules } = new AbilityBuilder();
// can read blog posts
can('read', 'BlogPost');
// can manage (i.e., do anything) own posts
can('manage', 'BlogPost', { author: user.id });
// cannot delete a post if it was created more than a day ago
cannot('delete', 'BlogPost', {
createdAt: { $lt: Date.now() - 24 * 60 * 60 * 1000 }
});
return new Ability(rules);
});
Do you see how easily business requirements were translated into CASL's rules?
Note: you can use class instead of string as a subject type (e.g., can('read', BlogPost)
)
And yes, Ability
class allow you to use some MongoDB operators to define conditions. Don't worry if you don't know MongoDB, it's not required and explained in details in Defining Abilities
Later on you can check abilities by using can
and cannot
methods of Ability
instance.
import { BlogPost, ForbiddenError } from '../models';
const user = getLoggedInUser(); // app specific function
const ability = defineAbilitiesFor(user)
// true if ability allows to read at least one Post
ability.can('read', 'BlogPost');
// true if there is no ability to read this particular blog post
const post = new BlogPost({ title: 'What is CASL?' });
ability.cannot('read', post);
// you can even throw an error if there is a missed ability
ForbiddenError.from(ability).throwUnlessCan('read', post);
Note: you can use class instead of string as a subject type (e.g., ability.can('read', BlogPost)
)
Of course, you are not restricted to use only class instances in order to check permissions on objects. See Check Abilities for the detailed explanation.
CASL has a complementary package @casl/mongoose which provides easy integration with MongoDB and mongoose.
import { AbilityBuilder } from '@casl/ability';
import { accessibleRecordsPlugin } from '@casl/mongoose';
import mongoose from 'mongoose';
mongoose.plugin(accessibleRecordsPlugin);
const user = getUserLoggedInUser(); // app specific function
const ability = defineAbilitiesFor(user);
const BlogPost = mongoose.model('BlogPost', mongoose.Schema({
title: String,
author: mongoose.Types.ObjectId,
content: String,
createdAt: Date,
hidden: { type: Boolean, default: false }
}))
// returns mongoose Query, so you can chain it with other conditions
const posts = await Post.accessibleBy(ability).where({ hidden: false });
// you can also call it on existing query to enforce permissions
const hiddenPosts = await Post.find({ hidden: true }).accessibleBy(ability);
// you can even pass the action as a 2nd parameter. By default action is "read"
const updatablePosts = await Post.accessibleBy(ability, 'update');
See Database integration for details.
CASL is incrementaly adoptable, that means you can start your project with simple claim (or action) based authorization and evolve it later, when your app functionality evolves.
CASL is composable, that means you can implement alternative conditions matching (e.g., based on joi, ajv or pure functions) and field matching (e.g., to support alternative syntax in fields like addresses.*.street
or addresses[0].street
) logic.
See Advanced usage for details.
Want to file a bug, contribute some code, or improve documentation? Excellent! Read up on guidelines for contributing.
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Copyright (c) 2017-present, Sergii Stotskyi