authorization

Authorization is a role-based-access-control (RBAC) library, to find permission for the logged-user on a resource.

A resource can be a check box, button, or textarea in html page.

Permissions can be used to enable/disable/view/hide components such as checkbox, input text, buttons, ... in html pages.

mappings of user - roles - permissions

Following two mapping files are used; they are external; they can be edited in any text editor:
* user to roles mapping file (refer sampleuser-roles.json)
* for each resources, a role to permissions mapping is added. (refer sampleresource_permissions.json)

permissions

A resource can have one or more of the following permission type:
* C reate (also known as Add)
* R ead (aka View)
* U pdate (aka Edit)
* D elete (aka Remove)

explanations

• user to roles mapping

  Let's say, an user to have a view only role, a mapping can be made like:
  ``` {
  "user_id": "1000",
  "roles": ["viewer"]
  }

  Note: More than one role can be assigned within square bracket, like ["viewer", "supervisor"].
  ```

• resource's role to permissions mapping
  Let's say resource is a checkbox. Permission is required to enable/disable it.

  role to permissions mapping can be like:

{ "resource": "cb_enable", "description": "enable or disable this checkbox", "role2permissions": [ {"role": "viewer", "permission": "R", "condition": "{{resource_owner_id}} == {{session_user_id}}" }, {"role": "editor", "permission": "RU", "condition": "{{resource_owner_id}} == {{session_user_id}}" }, {"role": "admin", "permission": "CRUD" }] }

Note:
a. In the above JSON notation, for a cb_enable resource, three roles to permissions mapping are made.

b. First role is a viewer role, for which, permission is assigned as R, that means READ-ONLY permission, on a condition that only owner of the resource, can view this check box.

• each resource, when created by an user, s/he becomes owner of it, his/her user id is stored/persisted as owner_id.

• when s/he login the application at later point in time, s/he will be identified through session user details.

• so, a comparision between stored owner_id is made with currently logged user (also referred as session user).

• a Handlebars Template notation is used in defining this condition.

• variables in this condition are resolved, and then comparision is done. For now, only simple comparision is possible, such as: a == b, a < b, ...

  c. Second role is an editor role, which is assigned with RU, that means READ and UPDATE permissions, on condition that only owner of the resource, can view and update.

  d. Third role is an admin role, which is assinged with CRUD, that means All permissions: CREATE, READ, UPDATE, DELETE. No condition is needed here.

how to use it

Refer sample code below: ``` let mut authzn = Authorization::load("./sampleresourcepermissions.json", "./sampleuserroles.json");

let user_id = "1002";
authzn.set_permissions_for(user_id);

let resource = "cb_enable";
let owner_id = "1001";
let mut data = Map::new();

data.insert("resource_owner_id".to_string(), to_json( &owner_id ) );
data.insert("session_user_id".to_string(), to_json( &user_id) );    

let mut permitted = authzn.allows_add(&user_id, &resource, &data);
if permitted { println!("CREATE PERMITTED"); } else { println!("Create NOT Permitted");}

permitted = authzn.allows_view(&user_id, &resource, &data);
if permitted { println!("VIEW PERMITTED"); } else { println!("View NOT Permitted");}

permitted = authzn.allows_edit(&user_id, &resource, &data);
if permitted { println!("EDIT PERMITTED"); } else { println!("Edit NOT Permitted"); }

permitted = authzn.allows_delete(&user_id, &resource, &data);
if permitted { println!("DELETE PERMITTED"); } else { println!("Delete NOT Permitted"); }

```