Koa-Authz

Koa-Authz is an authorization middleware for Koa, it's based on Node-Casbin: https://github.com/casbin/node-casbin.

Installation

use casbin v2.x

npm install casbin@2 koa-authz@2 --save

use casbin v3.x

npm install casbin@3 koa-authz@3 --save

Simple Example

const casbin = require('casbin')
const Koa = require('koa')
const app = new Koa()
const authz = require('koa-authz')

// response
app.use(async (ctx, next) => {
  const start = new Date()
  await next()
  console.log(new Date() - start)
})

// use authz middleware
app.use(authz({
  newEnforcer: async() => {
    // load the casbin model and policy from files, database is also supported.
    const enforcer = await casbin.newEnforcer('authz_model.conf', 'authz_policy.csv')
    return enforcer
  }
}))

// reload routes
const router = require('koa-router')({prefix: '/user'})
router.get('/', (ctx) => {
  ctx.body = {name: 'Chalin', age: 26}
})
router.put('/', (ctx) => {
  ctx.body = {status: 'success'}
})
app.use(router.routes(), router.allowedMethods())

app.listen(3000)

Use a customized authorizer

This package provides BasicAuthorizer, it uses HTTP Basic Authentication as the authentication method. If you want to use another authentication method like OAuth, you needs to extends BasicAuthorizer as below:

class MyAuthorizer extends BasicAuthorizer {
  // override function
  getUserName () {
    const { username } = this.ctx.state.user
    return username
  }
}

app.use(authz({
  newEnforcer: async () => {
    // load the casbin model and policy from files, database is also supported.
    const enforcer = await casbin.newEnforcer('examples/authz_model.conf', 'examples/authz_policy.csv')
    return enforcer
  },
  authorizer: (ctx, option) => new MyAuthorizer(ctx, option)
}))

How to control the access

The authorization determines a request based on {subject, object, action}, which means what subject can perform what action on what object. In this plugin, the meanings are:

1. subject: the logged-on user name
2. object: the URL path for the web resource like “dataset1/item1”
3. action: HTTP method like GET, POST, PUT, DELETE, or the high-level actions you defined like “read-file”, “write-blog”

For how to write authorization policy and other details, please refer to the Casbin's documentation.

Getting Help

• Node-Casbin

License

This project is licensed under the Apache 2.0 license.