Group-level role authorization in Node.js

I'm using Passport.js for authentication in an Express application.

I need to implement role-based authorization and I'm leaning towards connect-roles for it's easy integration with Passport.

I understand how basic roles are authorized (e.g. Admin, User, Editor), but I need to authroize these roles in the context of a groups.

A simplified use-case would be: An admin of a page can only see and edit details of the page he is managing.

How can the basic roles be combined with group assignment, is it necessarily a roles step or a matter of checking resource access rights in the passport authentication?

That's what I've done. It does not fully uses passport, but it works well (I took inspiration from Ghost). I do not know whether it is a good practise or it is safe, but here it is:

The config.json contains the permissions:

"user_groups": {
    "admin": {
      "full_name": "Administrators",
      "description": "Adminsitators.",
      "allowedActions": "all"
    },
    "modo": {
      "full_name": "Moderators",
      "description": "Moderators.",
      "allowedActions": ["mod:*", "comment:*", "user:delete browse add banish edit"]
    },
    "user": {
      "full_name": "User",
      "description": "User.",
      "allowedActions": ["mod:browse add star", "comment:browse add", "user:browse"]
    },
    "guest": {
      "full_name": "Guest",
      "description": "Guest.",
      "allowedActions": ["mod:browse", "comment:browse", "user:browse add"]
    }
  }

Then there is the permissions.coffee file

mongoose = require("mongoose")
###
This utility function determine whether an user can do this or this
using the permissions. e. g. "mod" "delete"

@param userId the id of the user
@param object the current object name ("mod", "user"...)
@param action to be executed on the object (delete, edit, browse...)
@param owner the optional owner id of the object to be "actionned"
###
exports.canThis = ((userId, object, action, ownerId, callback) ->
  User = mongoose.model("User")
  if typeof ownerId is "function"
    callback = ownerId
    ownerId = undefined
  if userId is ""
    return process(undefined, object, action, ownerId, callback)
  User.findById(userId, (err, user) ->
    if err then return callback err
    process(user, object, action, ownerId, callback)
  )
).toPromise(@)

process = (user, object, action, ownerId, callback) ->
  if user then role = user.role or "user"
  group = config.user_groups[role or "guest"]
  if not group then return callback(new Error "No suitable group")

  # Parses the perms
  actions = group.allowedActions
  for objAction in actions when objAction.indexOf object is 0
    # We get all the allowed actions for the object and group
    act = objAction.split(":")[1]
    obj = objAction.split(":")[0]
    if act.split(" ").indexOf(action) isnt -1 and obj is object
      return callback true

  callback false

config = require "../config"

Then some usage (using Q):

exports.edit = (userid, name) ->
  # Q promise
  deferred = Q.defer()
  # default value
  can = false
  # We check wheteher it can or not
  canThis(userid, "user", "edit").then((can)->
    if not userid
      return deferred.reject(error.throwError "", "UNAUTHORIZED")
    User = mongoose.model "User"
    User.findOne({username: name}).select("username location website public_email company bio").exec()
  ).then((user) ->
    # Can the current user do that?
    if not user._id.equals(userid) and can is false
      return deferred.reject(new Error())
    # Done!
    deferred.resolve user
  ).fail((err) ->
    deferred.reject err
  )
  deferred.promise