cando

An authorization module

CanDo

This module creates a dynamic handler for matching and authorizing routes.

In order, to perform an authorization for a given user, you must have access to the user, model, url, and method.

   +-------------------------+
   |       Request           |
   |                         |
   +----------+--------------+
              |
              |
   +----------+--------------+
   |                         |
   |                         |
   |     Authentication      |
   |                         |
   +-----------+-------------+
               |
               |
               |
   +-----------v-------------+
   |                         |
   |                         |
   |     Authorization       |
   |        (CanDo)          |
   +-----------+-------------+
               |
               |
   +-----------v-------------+
   |                         |
   |     app.router          |
   |                         |
   +-------------------------+

Here is a diagram of the middleware stack, the CanDo module can be placed between the Authentication and App.router. It needs the user, model, url, and method;

The concept behind the cando module is to give you the ability to create custom based authorization rules in a sharable javascript file that can be provided to both the server and the client. THis way our authorization rules are in one place and applied to the front-end to hide and show functionality and applied to the back-end to allow or deny actions.

var cando = require('cando');
 
cando
  .define('/api/users', function() {
    this.user.role === 'admin' ? this.allow() : this.deny();
    this.next();
  })
  .define('/api/users/:id', 'PUT', function() {
    this.user.id === this.model.user_id ? this.allow() : this.deny();
    this.next();
  });
 
app.use(...); //authentication 
app.use(function(reqresnext) {
  // /api/:model/:id 
  var id = req.url.split('/')[3];
  db.get(id, function(errdoc) {
    if (err) { return res.send(500, err); }
    req.model = doc;
    next();
  });
});
 
app.use(function(reqresnext) {
  var data = {
    user: req.session.user,
    model: req.model,
    req: req
  };
  
  cando.verify(data, function(errauthorized) {
    if (err) { return res.send(500, err); }
    if (!authorized) { return res.send(403, { status: 'Not Authorized' }); }
    console.log('authorized');
    next();
  });
});

Cando

Is an authorization module that includes a micro-router for matching defined routes and providing authorization logic to confirm the user has the right to execute the requested api function.

There are two endpoints, #define and #verify.

[define] takes a url pattern, a optional verb array, if null, then it is assumed you want to match against all verbs, and is the default verbs are GET, POST, PUT, DELETE. the last parameter is the function you want to be invoked on match in that function you will have access to the following:

  • this.user [object] if set
  • this.model [object] if set
  • this.url [string] - url of the request
  • this.method [string] - method of the request
  • this.params [object] if using colon patterns
  • this.set is the function you call to specify if the request is authorized or not. this.allow() or this.deny();
  • this.next to continue to the next match

[verify] is the function that performs the match against all of your defined patterns. So you normally call this in the middleware stack or on the client before you want to execute your application code.


  • cando.js
  • mapleTree
  • NodeJS