Authorize

Authorize is a rule based authorization module for your elixir app.

Authorize walks through rules your resource to determine if it grands authorization, or not. These rules are easily created using a DSL.

Any rule can return three states:

• :ok: means that this rule grands authorization
• :undecided: it will continue with the following rules to see if it will grand authorization
• :unauthorized: it will not grand authorization and will not look at the following rules

How this translate to code is as follows:

defmodule Item.Authorization do
  use Authorize

  rule [:read], "only admins can read invisible items", struct_or_changeset, actor do
    if !actor.admin? and get_struct(struct_or_changeset).invisible?, do: :unauthorized, else: :ok
  end
end

We can now use this authorization module in the following way:

iex> normal_user = %User{name: "Ed", admin?: false}
...> invisible_item = %Item{readonly?: false, invisible?: true}

...> Item.Authorization.authorize(normal_user, invisible_item, :read)
{:unauthorized, %Item{...}, "only admins can read invisible items"}

iex> admin = %User{name: "Admin", admin?: true}
...> Item.Authorization.authorize(normal_user, invisible_item, :read)
{:ok, %Item{...}}

You can define a rule with rule [action], description, struct_or_changeset, actor

With rule you are defining a rule.

The first argument is the action this rule applies to. I would recommend to use the well known CRUD (create, read, update, and delete) actions, but you can also use something else (Authorize does not care). If you leave the first argument out and start with the description, the rule will apply to all actions.

The second argument is a description, when this rule returns :unauthorized this will be passed as the reason.

struct_or_changeset and actor are the variables that you can use in the rule's body. The struct_or_changeset is the resource, and actor is the actor that tries to perform the action. This can be anything you like. To make it work well with ecto we provide two helper methods is_changeset?/1 and get_struct/1. is_changeset/1 will return true if struct_or_changeset is a changeset. get_struct/1 returns the struct. If the item is a changeset, it will return changeset.data.

If there is no rule found that returns :unauthorized or :ok, the authorize/3 function will return {:unauthorized, _, "no authorization rule found"}

More examples in test/authorize_test.

Installation

If available in Hex, the package can be installed as:

1. Add authorize to your list of dependencies in mix.exs:

```elixir
def deps do
  [{:authorize, "~> 0.1.0"}]
end
```

1. Ensure authorize is started before your application:

```elixir
def application do
  [applications: [:authorize]]
end
```