browser-acl 🔒

Simple access control (ACL) library for the browser inspired by Laravel's guards and policies.

Go to vue-browser-acl for the official Vue package.

Install

yarn add browser-acl

Setup

import Acl from 'browser-acl'
const acl = new Acl()

acl.rule('view', Post)
acl.rule('moderate', Post, (user) => user.isModerator())
acl.rule(['edit', 'delete'], Post, (user, post) => post.userId === user.id)
acl.rule('purgeInactive', user => user.isAdmin)

Policies are also supported:

acl.policy({
  view: true,
  edit: (user, post) => post.userId === user.id),
}, Post)

Note: policies takes precedence over rules.

Usage

// true if user owns post
acl.can(user, 'edit', post)

// true if user owns at least posts
acl.some(user, 'edit', posts)

// true if user owns all posts
acl.every(user, 'edit', posts)

You can add mixins to your user class:

acl.mixin(User) // class not instance

user.can('edit', post)
user.can.some('edit', posts)
user.can.every('edit', posts)

Subject mapping

The process of mapping input to rules

The default subject mapper makes use of "poor-man's reflection", meaning it will use the name of the input subject's constructor to group the rules.

When using webpack or similar this method can break if you are not careful. Since code minifiers will rename functions you have to make sure you only rely on the function to set up your rules and asking for permission.

Meeeh

1: acl.rule('edit', 'Post')
2: ...
3: acl.can(user, post) 

If your build process minifies your code (specifically mangling of function and class names), this will break in line 3 since the constructor of post will likely not be Post but rather a single letter or a name prefixed with __WEBPACK_IMPORTED_MODULE.

Better

1: acl.rule('edit', Post)
2: ...
3: acl.can(user, post) 

Here Post in line 1 the class or constructor function is passed in, and whatever that name is after minification, is used to register the rules. As long as the same import is used throughout your code base it will work.

Best

1: acl.register(Post, 'Post')
2: ...
3: acl.rule('create', 'Post') // <-- works as expected
4: ...
5: acl.rule('edit', Post)     // <-- and so does this
6: acl.rule('edit', post)     // <-- and so does this

This basically sets up an alias for Post the class or constructor function, so that you can refer to it as 'Post'.

Alternatives to classes and constructor functions

You can also override the subjectMapper function and a property to you objects with the subject name.

See subjectMapper

Additional Parameters and Global Rules

You can define global rules by omitting the subject when defining rules.

acl.rule('purgeInactive', user => user.admin)
acl.can('purgeInactive')

Also you can pass additional parameters to the handler like this:

acl.rule('edit', Post, (user, post, verb, additionalParameter) => true)
acl.can('edit', post, additionalParameter)

However, you cannot combine the two without explicitly stating that you are defining a global rule. You do this by importing the special GlobalRule subject.

import {GlobalRule} from 'browser-acl'
acl.rule('purgeInactive', GlobalRule, user => user.admin)
acl.can('purgeInactive', GlobalRule, additionalParameter)

Note: When defining the rule you can omit it, but is is required for can. This is only in the case when you need to pass additional parameters.

API

Table of Contents

• Acl
  • rule
  • policy
  • register
  • can
  • some
  • every
  • mixin
  • subjectMapper
  • reset
  • removeRules
  • removePolicy
  • removeAll

Acl

Simple ACL library for the browser inspired by Laravel's guards and policies.

Parameters

• $0 Object (optional, default {})
  • $0.strict (optional, default false)
• options Object
• null Boolean {strict=false}={} Errors out on unknown verbs when true

rule

You add rules by providing a verb, a subject and an optional test (that otherwise defaults to true).

If the test is a function it will be evaluated with the params: user, subject, and subjectName. The test value is ultimately evaluated for truthiness.

Examples:

acl.rule('create', Post)
acl.rule('edit', Post, (user, post) => post.userId === user.id)
acl.rule('edit', Post, (user, post, verb, additionalParameter, secondAdditionalParameter) => true)
acl.rule('delete', Post, false) // deleting disabled
acl.rule('purgeInactive', user => user.isAdmin) // global rule

Parameters

• verbs (Array<string> | string)
• subject (Function | Object | string) ?
• test (Boolean | Function) =true (optional, default true)

Returns Acl

policy

You can group related rules into policies for a subject. The policies properties are verbs and they can plain values or functions.

If the policy is a function it will be new'ed up before use.

  class Post {
    constructor() {
      this.view = true       // no need for a functon
      this.delete = false    // not really necessary since an abscent
                             // verb has the same result
    }
    beforeAll(verb, user, ...theRest) {
      if (user.isAdmin) {
        return true
      }
      // return nothing (undefined) to pass it on to the other rules
    }
    edit(user, post, verb, additionalParameter, secondAdditionalParameter) {
      return post.id === user.id
    }
  }

Policies are useful for grouping rules and adding more complex logic.

Parameters

• policy Object A policy with properties that are verbs
• subject (Function | Object | string)

Returns Acl

register

Explicitly map a class or constructor function to a name.

You would want to do this in case your code is heavily minified in which case the default mapper cannot use the simple "reflection" to resolve the subject name.

Note: If you override the subjectMapper this is not used, bud it can be used manually through this.registry.

Parameters

• klass Function A class or constructor function
• subjectName string

can

Performs a test if a user can perform action on subject.

The action is a verb and the subject can be anything the subjectMapper can map to a subject name.

E.g. if you can to test if a user can delete a post you would pass the actual post. Where as if you are testing us a user can create a post you would pass the class function or a string.

  acl.can(user, 'create', Post)
  acl.can(user, 'edit', post)
  acl.can(user, 'edit', post, additionalParameter, secondAdditionalParameter)

Note that these are also available on the user if you've used the mixin:

  user.can('create', Post)
  user.can('edit', post)

Parameters

• user Object
• verb string
• subject (Function | Object | string)
• args ...any Any other param is passed into rule

Returns any Boolean

some

Like can but subject is an array where only some has to be true for the rule to match.

Note the subjects do not need to be of the same kind.

Parameters

• user Object
• verb
• subjects Array<(Function | Object | string)>
• args ...any Any other param is passed into rule

Returns any Boolean

every

Like can but subject is an array where all has to be true for the rule to match.

Note the subjects do not need to be of the same kind.

Parameters

• user Object
• verb
• subjects Array<(Function | Object | string)>
• args ...any Any other param is passed into rule

Returns any Boolean

mixin

Mix in augments your user class with a can function object. This is optional and you can always call can directly on your Acl instance.

user.can()
user.can.some()
user.can.every()

Parameters

• User Function A user class or contructor function

subjectMapper

Rules are grouped by subjects and this default mapper tries to map any non falsy input to a subject name.

This is important when you want to try a verb against a rule passing in an instance of a class.

• strings becomes subjects
• function's names are used for subject
• object's constructor name is used for subject

Override this function if your models do not match this approach.

E.g. say that you are using plain data objects with a type property to indicate the type of the object.

  acl.subjectMapper = s => typeof s === 'string' ? s : s.type

can will now use this function when you pass in your objects.

acl.rule('edit', 'book', (user, book) => user.id === book.authorId)
const thing = {title: 'The Silmarillion', authorId: 1, type: 'book'}
acl.can(user, 'edit', thing)

In the example above the 'thing' will follow the rules for 'book'. The user can edit the book if they are the author.

See register() for how to manually map classes to subject name.

Parameters

• subject (Function | Object | string)

Returns string A subject

reset

Removes all rules, policies, and registrations

Returns Acl

removeRules

Remove rules for subject

Optionally limit to a single verb.

Parameters

• subject (Object | Function | String)
• verb String? an optional verb (optional, default null)

Returns Acl

removePolicy

Remove policy for subject

Parameters

• subject (Object | Function | String)

Returns Acl

removeAll

Convenience method for removing all rules and policies for a subject

Parameters

• subject (Object | Function | String)

Returns Acl