express-permissions

Easy to use permissions system for Express

Install

npm install express-permissions --save

Usage

Require express-permissions and load it as middleware.

ExpressPermissions = require('express-permissions')

app.use(ExpressPermissions.middleware())

Middleware is executed in order from first to last, make sure any middleware you will need to run first is added before express-permissions.

Defining permissions

Permissions are defined by calling ExpressPermissions.add() which takes 4 arguments

• The express app
• The path you want to match
• The boolean/object/function
• True/False should this be wrapped in a promise (defaults to false)

Examples of all the permission types are below:

//Allways allow requests to /
ExpressPermissions.add(app, '/', true)
//Allow access to /admin if response.local.current_user.admin == 1
ExpressPermissions.add(app, '/admin', {current_user: {admin: 1}})
//Allow access to /admin/reboot if the supplied function returns true
ExpressPermissions.add(app, '/admin/reboot', function (req, res){
  return (req.ip == '127.0.0.1')
})

//Allow access if this promise resolves true
ExpressPermissions.add(app, '/project/:id/edit', function (req, res, resolve, reject){
  MyDatabase.query("SELECT * FROM `projects` WHERE `id` = '" + req.params.id + "' LIMIT 1").then(function(project){
      resolve(project.editable)
  })
}, true)

Permission checks travel upwards, in this example a request for /admin/index would see no permission itself and then try /admin. Due to this it is highly reccomended that you define something for / otherwise you may end up with routes that have no permissions.

Handling Error 403s

By default express-permissions ends the response preventing it from traveling any further this leaves the user with an empty reply which isn't really any good.

If you define app.permissionDenied it will be called when an error 403 is triggered instead of ending the response.

app.permissionDenied needs to take 2 arguments req and res and should work like any other express method.