Express-bitmask-permissions

Middleware that takes:
- On middleware construction:
- A route sections object defining a route group affinity
- generic-bitmask descriptor body defining a bitmask bit permission affinity
- Runtime:
- An array of user bitmasks

And produces an array of permission in req.permissions for requested route based on its predefined section

Installation

``sh
npm install git+ssh://git@code.42px.org:42px/express-bitmask-permissions.git --save
`

Usage

$3

`JS
import PBM from 'express-bitmask-permissions';
import * as jwt from 'express-jwt';

const app = express();

const options = {
// (required) Route section affinity
sections: {
'/cats': 0,
'/dogs': 1
},
// (required) Bit permission affinity
// Starts with 1
descriptorBody: {
'feed': 1,
'pet': 2,
'play': 3
}
// (optional) JWT field with bitmasks array
// 'masks' by default
masksField: 'masks'
};

app.use(PBM(options));

...

app.post('/cats/:name/pet', function(req, res, next) {

// req.permissions is now array of values
// from descriptor, or is empty

if (!req.permissions.includes('pet'))
return res
.status(403)
.send(You're not allowed to pet ${req.params.name});

pet.cat(name);

res.send(Cat ${req.params.name} purrs);

})

`

How it works

Middleware does following:

- Takes sections definition from options to decide which particular bitmask to check against
- 'cats': 0 will check any request starting with url element '/cats' against req.user.masks[0]
- Extracts bitmask array from req.user using default masks field or one provided in masksField option
- Selects particular bitmask from array based on request url section base element match
- e.g. '/cats' is a base element for a '/cats/43/kitties?fluffy=yes'
- Descriptor is used to extract human-readable permissions from the bitmask

Sections:
`JS
{
'/cats': 0,
'/dogs': 1
}
`

Descriptor:
`JS
{
'feed': 1,
'pet': 2,
'play': 3
}
`

Bitmask array:
`JS
[ 777, 0 ]
`

On init middleware with predefined section and descriptor defnition is produced

On request:
- POST /cats/17/pet
- Express req provides an array of user bitmasks extracted by other middleware
- req.user.masks === [ 777, 0 ]
- Bitmask selected from an array with the help of a section definition
- req.user.masks[sections[req.baseUrl]] === 777
- generic-bitmask is used to extract an array of permissions from the bitmask 777 to the array description
- req.permissions === [ 'feed', 'pet', 'play' ]`
- Access control happens downstream