koa-2-acl

Koa 2 Access Control Lists (koa-2-acl) enable you to manage the requests made to your koa server. It makes use of ACL rules to protect your server from unauthorized access. ACLs defines which user groups are granted access and the type of access they have against a specified resource. When a request is received against a resource. koa-2-acl checks the corresponding ACL policy to verify if the requester has the necessary access permissions.

This project refers to express-acl project

I just make the express-acl can run in koa 2.

If this middleware is useful to you and you want, you can star it.

README LANGUAGE

中文文档

What are ACL rules

ACL is a set of rules that tell koa-2-acl how to handle the request made to your server a specific resource. Think of like road signs or traffic lights that control how your traffic flows in your app. ACL rules are defined in JSON or yaml syntax.

Important

Resource property has been changed from using string to routes, this change was made to support subrouting functionality, this means if your resource was users which gave access to all routes starting with users, it should be changed to users/*. The asterisk informs the package to match all the routes that start with users.

The Resource property also can include params i.e /users/:id this will match routes such as users/45, users/42, where 42 and 45 are considered :id section on the resource.

Example

[{  
  "group": "admin",
  "permissions": [{
    "resource": "users/*",
    "methods": [ "POST", "GET", "PUT" ],
    "action": "allow"
  }]
}]

YAML syntax

- group: user
  permissions:
    - resource: users/*
      methods:
        - GET
        - POST
        - DELETE
      action: allow

The contents of this file will be discussed in the usage section

Installation

You can download koa-2-acl from NPM

 
$ npm i koa-2-acl -S
 

then in your project require koa-2-acl

 
const acl = require('koa-2-acl')
 
// ES6
 
import acl from 'koa-2-acl'
 

or GitHub

$ git clone https://github.com/JefferyLiang/koa-2-acl.git

copy the lib folder to your project and then require acl.js

 
const acl = require('./lib')
 
// ES6
 
import acl from './lib/acl'
 

Usage

Koa acl uses the configuration approach to define access levels.

Configuration

The first step is to create a file called nacl.json and place this in the root folder. This is the file where we will define the roles that can access our application and the policies that restrict or give access to a certain resource. Take a look at the example below.

[{
  "group": "admin",
  "permissions": [{
    "resource": "*",
    "methods": "*"
  }],
  "action": "allow"
}, {
  "group": "user",
  "permissions": [{
    "resource": "users/*",
    "methods": [ "POST", "GET", "PUT" ],
    "action": "deny"
  }]
}]

In the example above we have defined an ACL with two policies with roles, user and admin. A valid ACL should be an Array of objects(policies). The properties of the policies are explained below.

Property	Type	Description
group	string	This property defines the access group to which a user can belong to e.g user,guest,admin,tranier. This may vary depending on the architecture of your application.
permissions	Array	This property contains an array of objects that define the resource exposed to a group and the methods allowed/denied.
resource	String	This is the route the permissions will be applied against. This property can be either * which applies to all routes, api/users which will apply permissions to routes api/users or api/users/* which applies permission to all routes that prefix api/users
methods	string or Array	This are http methods that a user is allowed or denied from executing. [ "POST", "GET", "PUT" ]. Use glob * if you want to include all http methods.
action	string	This property tell koa-2-acl what action to perform on the permission given. Using the above example, the user policy specifies a deny action, meaning all traffic on route /api/users for methods GET, PUT, POST is denied, but the rest allowed. And for the admin, all traffic for all resource is allowed.
subRoutes	Array	This is permissions that should be used on subroutes of a specified prefix. It is helpful when certain routes under a prefix require different access definitions.

How to define effective ACL rules

ACLs define the way requests will be handled by koa-2-acl, therefore its important to ensure that they are well designed to maximise efficiency. For more details follow this link

Authentication

koa-2-acl depends on the role of each authenticated user to pick the corresponding ACL policy for each defined user groups. Therefore, you should always place the acl middleware after the authenticate middleware. Example using jsonwebtoken middleware.

  // jsonwebtoken powered middleware
  const acl = require('koa-2-acl')
  const jwt = require('jsonwebtoken')
  ROUTER.use((ctx, next) => {
    // token like this 'Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjVhMzljYTZkNzliOWZkYmJjZjM1OGI5MiIsIm5pY2tuYW1lIjoieXBhZG1pbiIsInJvbGUiOiJhZG1pbiIsImNvbXBhbnkiOiI1YTM5YzM5MmE1ZmYyMGI2YWI0MmE1NTkiLCJpYXQiOjE1MTc1NTIyMTYsImV4cCI6MTUxNzU5NTQxNn0.M6IqUvKAmnSMJ0Kb-2UIeUmLrv69Kuhf-zibsWt_uYk'
    const token = ctx.request.headers['authorization']
    if (token) {
      let codeStr = token.split(" ")[1]
      jwt.verify(codeStr, key, (err, decoded) => {
        if (err) ctx.throw(err)
        ctx.request.decoded = decoded
      })
    }
    next()
  })
 
  // koa-2-acl middleware depends on the role
  // the role can either be in ctx.request.decoded (jsonwebtoken) or ctx.request.session (koa-session)
 
  ROUTER.use(acl.authorize)

API

There are two API methods for koa-2-acl.

config[type: function, params: config { filename, path, yml, encoding, baseUrl, rules }, response {}]

This method loads the configuration json file. When this method it looks for nacl.json the root folder if path parameter is not specified.

config

• filename: Name of the ACL rule file e.g nacl.json
• path: Location of the ACL rule file
• yml: when set to true means use yaml parser else JSON parser
• baseUrl: The base url of your API e.g /developer/v1
• rules: Allows you to set rules directly without using config file
• defaultRole: The default role to be assigned to users if they have no role defined
• decodedObjectName: The name of the object in the ctx.request where the role resides.
• searchPath: The path in which to look for the role within the ctx.request object

 
  const acl = require('koa-2-acl')
 
  // path not speificed
  // looks for config.json in the root folder
  // if your backend routes have base url prefix e.g /api/<resource>, v1/<resource>, developer/v1/<resource>
  // specify it in the config property baseUrl { baseUrl: 'api' }, { baseUrl: 'v1' }, { baseUrl: 'developer/v1' } respectively
  // else you can specify { baseUrl: '/' } or ignore it entirely
 
  acl.config({
    baseUrl: 'api'
  })
 
  // path specified
  // looks for acl.json in the root folder
 
  acl.config({
    filename: 'acl.json',
    path: 'config'
  })
 
  // When specifying path you can also rename the json file e.g
  // The above file can be acl.json or nacl.json or any_file_name.json
 
  acl.config({
    rules: rulesArray
  })
 
  // When you use rules api, nacl will **not** to find the json/yaml file, so you can save your acl-rules with any Database
  // The default role allows you to specify which role users will assume if they are not assigned any
 
  acl.config({
    defaultRole: 'anonymous'
  })
 
  // By default this module will look for role in decoded object, if you would like to change the name of the object, you can specify this with decodedObjectName property.
  
  // As per the example below, this module will look for ctx.request.user.role as compared to default ctx.request.decoded.role.
 
  acl.config({
    decodedObjectName: 'user'
  })
 
  // You can also specify a deep path in which to look for the role, in case it's not inside the usual locations
 
  acl.config({
    searchPath: 'user.Role.name' // will search for role in ctx.request.user.Role.name
  })
 

authorize [type: middleware]

This is the middleware that manages your application requests based on the role and acl rules.

 
app.use(acl.authorize)
 

unless [type: function, params: function or object]

By default any route that has no defined policy against it is blocked, this means you cannot access this route until you specify a policy. This method enables you to exclude unprotected routes. This method users koa-2-acl package to achieve this functionality. For more details on its usage follow this link koa-unless

 
  // assuming we want to hide /auth/google from koa-2-acl
 
  app.use(acl.authorize.unless({ path: ['/auth/google'] }))
 

Anytime that this route is visited, unless method will exclude it from being passed though our middleware.

N/B You don't have to install koa-unless it has already been included into the project.

Response

This is the custom error you would like returned when a user is defined access to a resource. This error will be bound to the status code of 403

 
  const acl = require('koa-2-acl')
 
  let configObject = {
    filename: 'acl.json',
    path: 'config'
  }
 
  let responseObject = {
    status: 'Access Denied',
    message: 'You are not authorized to access this resource'
  }
 
  acl.config(configObject, responseObject)
 

Example

Install koa-2-acl

 
$ npm i koa-2-acl -S
 

Create nacl.json in your root folder

[{
  "group": "user",
  "permissions": [{
    "resource": "users",
    "methods": [
      "POST",
      "GET",
      "PUT"
    ],
  "action": "allow"
  }]
}]

Require koa-2-acl in your project router file.

 
  const acl = require('koa-2-acl')
 
  // ES6
  import acl from 'koa-2-acl'
 

Call the config method

 
  acl.config({
    //specify your own baseUrl
    baseUrl: 'api'
  })
 

Add the acl middleware

 
  app.use(acl.authorize)
 

Contributions

Pull requests are welcome. If you are adding a new feature or fixing an as-yet-untested use case, please consider writing unit test to cover your change(s).