# Rajska
Rajska is an elixir authorization library for [Absinthe](https://github.com/absinthe-graphql/absinthe).
It provides the following middlewares:
- [Query Authorization](#query-authorization)
- [Scope Authorization](#scope-authorization)
- [Object Authorization](#object-authorization)
- [Field Authorization](#field-authorization)
Documentation can be found at [https://hexdocs.pm/rajska/](https://hexdocs.pm/rajska).
## Installation
The package can be installed by adding `rajska` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:rajska, "~> 0.1.0"},
]
end
```
## Usage
Create your Authorization module, which will implement the [Rajska Authorization](https://hexdocs.pm/rajska/Rajska.Authorization.html) behaviour and contain the logic to validate user permissions and will be called by Rajska middlewares. Rajska provides some helper functions by default, such as [is_role_authorized?/2](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:is_role_authorized?/2), [has_user_access?/3](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:has_user_access?/3) and [is_field_authorized?/3](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:is_field_authorized?/3), but you can override them with your application needs.
```elixir
defmodule Authorization do
use Rajska,
roles: [:user, :admin]
end
```
Note: if you pass a non Keyword list to `roles`, as above, Rajska will assume your roles are in ascending order and the last one is the super role. You can override this behavior by defining your own `is_super_role?/1` function or define your `roles` as a Keyword list in the format `[user: 0, admin: 1]`.
Add your [Authorization](https://hexdocs.pm/rajska/Rajska.Authorization.html) module to your `Absinthe.Schema` [context/1](https://hexdocs.pm/absinthe/Absinthe.Schema.html#c:context/1) callback and the desired middlewares to the [middleware/3](https://hexdocs.pm/absinthe/Absinthe.Middleware.html#module-the-middleware-3-callback) callback:
```elixir
def context(ctx), do: Map.put(ctx, :authorization, Authorization)
def middleware(middleware, field, %Absinthe.Type.Object{identifier: identifier})
when identifier in [:query, :mutation] do
middleware
|> Rajska.add_query_authorization(field, Authorization)
|> Rajska.add_object_authorization()
end
def middleware(middleware, field, object) do
Rajska.add_field_authorization(middleware, field, object)
end
```
You can also add all Rajska middlewares at once by calling [add_middlewares/4](https://hexdocs.pm/rajska/Rajska.Schema.html#add_middlewares/4):
```elixir
def context(ctx), do: Map.put(ctx, :authorization, Authorization)
def middleware(middleware, field, object) do
Rajska.add_middlewares(middleware, field, object, Authorization)
end
```
Since Scope Authorization middleware must be used with Query Authorization, it is automatically called when adding the former.
Middlewares usage can be found below.
## Middlewares
### Query Authorization
Ensures Absinthe's queries can only be accessed by determined users.
Usage:
[Create your Authorization module and add it and QueryAuthorization to your Absinthe.Schema](#usage). Then set the permitted role to access a query or mutation:
```elixir
mutation do
field :create_user, :user do
arg :params, non_null(:user_params)
middleware Rajska.QueryAuthorization, permit: :all
resolve &AccountsResolver.create_user/2
end
field :update_user, :user do
arg :id, non_null(:integer)
arg :params, non_null(:user_params)
middleware Rajska.QueryAuthorization, [permit: :user, scoped: User] # same as {User, :id}
resolve &AccountsResolver.update_user/2
end
field :delete_user, :user do
arg :id, non_null(:integer)
middleware Rajska.QueryAuthorization, permit: :admin
resolve &AccountsResolver.delete_user/2
end
end
```
Query authorization will call [is_role_authorized?/2](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:is_role_authorized?/2) to check if the [user](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:get_current_user/1) [role](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:get_user_role/1) is authorized to perform the query.
### Scope Authorization
Provides scoping to Absinthe's queries, as seen above in [Query Authorization](#query-authorization).
In the above example, `:all` and `:admin` permissions don't require the `:scoped` keyword, as defined in the [not_scoped_roles/0](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:not_scoped_roles/0) function, but you can modify this behavior by overriding it.
Valid values for the `:scoped` keyword are:
- `false`: disables scoping
- `User`: a module that will be passed to [has_user_access?/3](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:has_user_access?/3). It must implement a [Authorization behaviour](https://hexdocs.pm/rajska/Rajska.Authorization.html) and a `__schema__(:source)` function (used to check if the module is valid in [validate_query_auth_config!/2](https://hexdocs.pm/rajska/Rajska.Schema.html#validate_query_auth_config!/2))
- `{User, :id}`: where `:id` is the query argument that will also be passed to [has_user_access?/3](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:has_user_access?/3)
- `{User, [:params, :id]}`: where `id` is the query argument as above, but it's not defined directly as an `arg` for the query. Instead, it's nested inside the `params` argument.
- `{User, :user_group_id, :optional}`: where `user_group_id` (it could also be a nested argument) is an optional argument for the query. If it's present, the scoping will be applied, otherwise no scoping is applied.
### Object Authorization
Authorizes all Absinthe's [objects](https://hexdocs.pm/absinthe/Absinthe.Schema.Notation.html#object/3) requested in a query by checking the permission defined in each object meta `authorize`.
Usage:
[Create your Authorization module and add it and ObjectAuthorization to your Absinthe.Schema](#usage). Then set the permitted role to access an object:
```elixir
object :wallet_balance do
meta :authorize, :admin
field :total, :integer
end
object :company do
meta :authorize, :user
field :name, :string
field :wallet_balance, :wallet_balance
end
object :user do
meta :authorize, :all
field :email, :string
field :company, :company
end
```
With the permissions above, a query like the following would only be allowed by an admin user:
```graphql
{
userQuery {
name
email
company {
name
walletBalance { total }
}
}
}
```
Object Authorization middleware runs after Query Authorization middleware (if added) and before the query is resolved by recursively checking the requested objects permissions in the [is_role_authorized?/2](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:is_role_authorized?/2) function (which is also used by Query Authorization). It can be overridden by your own implementation.
### Field Authorization
Authorizes Absinthe's object [field](https://hexdocs.pm/absinthe/Absinthe.Schema.Notation.html#field/4) according to the result of the [is_field_authorized?/3](https://hexdocs.pm/rajska/Rajska.Authorization.html#c:is_field_authorized?/3) function, which receives the user role, the meta `scope_by` atom defined in the object schema and the `source` object that is resolving the field.
Usage:
[Create your Authorization module and add it and FieldAuthorization to your Absinthe.Schema](#usage). Then add the meta `scope_by` to an object and meta `private` to your sensitive fields:
```elixir
object :user do
meta :scope_by, :id
field :name, :string
field :is_email_public, :boolean
field :phone, :string, meta: [private: true]
field :email, :string, meta: [private: & !&1.is_email_public]
end
```
As seen in the example above, a function can also be passed as value to the meta `:private` key, in order to check if a field is private dynamically, depending of the value of another field.
## Related Projects
[Crudry](https://github.com/gabrielpra1/crudry) is an elixir library for DRYing CRUD of Phoenix Contexts and Absinthe Resolvers.
## License
MIT License.
See [LICENSE](./LICENSE) for more information.
