Add OAuth scopes

https://github.com/foodcoops/foodsoft/issues/582#issuecomment-442513237

app/controllers/api/v1/base_controller.rb

@@ -1,4 +1,6 @@
 class Api::V1::BaseController < ApplicationController
+  include Concerns::AuthApi
+
   protect_from_forgery with: :null_session
 
   before_action :skip_session
@@ -11,16 +13,6 @@ class Api::V1::BaseController < ApplicationController
 
   private
 
-  def authenticate
-    doorkeeper_authorize!
-    super if current_user
-  end
-
-  # @return [User] Current user, or +nil+ if no valid token.
-  def current_user
-    @current_user ||= User.undeleted.find(doorkeeper_token.resource_owner_id) if doorkeeper_token
-  end
-
   # @return [Ordergroup] Current user's ordergroup, or +nil+ if no valid token or user has no ordergroup.
   def current_ordergroup
     current_user.try(:ordergroup)
@@ -28,7 +20,9 @@ class Api::V1::BaseController < ApplicationController
 
   def require_ordergroup
     authenticate
-    raise Api::Errors::PermissionRequired unless current_user.ordergroup.present?
+    unless current_ordergroup.present?
+      raise Api::Errors::PermissionRequired.new('Forbidden, must be in an ordergroup')
+    end
   end
 
   def skip_session
@@ -42,13 +36,18 @@ class Api::V1::BaseController < ApplicationController
   end
 
   def not_acceptable_handler(e)
-    render status: 422, json: {error: 'not_acceptable', error_description: e.message || 'Data not acceptable' }
+    msg = e.message || 'Data not acceptable'
+    render status: 422, json: {error: 'not_acceptable', error_description: msg}
   end
 
   def doorkeeper_unauthorized_render_options(error:)
     {json: {error: error.name, error_description: error.description}}
   end
 
+  def doorkeeper_forbidden_render_options(error:)
+    {json: {error: error.name, error_description: error.description}}
+  end
+
   def permission_required_handler(e)
     msg = e.message || 'Forbidden, user has no access'
     render status: 403, json: {error: 'forbidden', error_description: msg}
@@ -58,5 +57,4 @@ class Api::V1::BaseController < ApplicationController
   def show_user(user = current_user, **options)
     user.display
   end
-
 end

app/controllers/api/v1/configs_controller.rb

@@ -1,5 +1,7 @@
 class Api::V1::ConfigsController < Api::V1::BaseController
 
+  before_action ->{ doorkeeper_authorize! 'config:user', 'config:read', 'config:write' }
+
   def show
     render json: FoodsoftConfig, serializer: ConfigSerializer, root: 'config'
   end

app/controllers/api/v1/user/users_controller.rb

@@ -0,0 +1,9 @@
+class Api::V1::User::UsersController < Api::V1::BaseController
+
+  before_action ->{ doorkeeper_authorize! 'user:read', 'user:write' }
+
+  def show
+    render json: current_user
+  end
+
+end

app/controllers/api/v1/users_controller.rb

@@ -1,7 +0,0 @@
-class Api::V1::UsersController < Api::V1::BaseController
-
-  def show
-    render json: current_user
-  end
-
-end

app/controllers/concerns/auth_api.rb

@@ -0,0 +1,66 @@
+# Controller concern for authentication methods
+#
+# Split off from main +ApplicationController+ to allow e.g.
+# Doorkeeper to use it too.
+module Concerns::AuthApi
+  extend ActiveSupport::Concern
+
+  protected
+
+  def authenticate
+    # authenticate does not look at scopes, we just want to know if there's a valid token
+    # @see https://github.com/doorkeeper-gem/doorkeeper/blob/v5.0.1/lib/doorkeeper/models/access_token_mixin.rb#L218
+    doorkeeper_render_error unless doorkeeper_token && doorkeeper_token.accessible?
+    super if current_user
+  end
+
+  # @return [User] Current user, or +nil+ if no valid token.
+  def current_user
+    @current_user ||= User.undeleted.find(doorkeeper_token.resource_owner_id) if doorkeeper_token
+  end
+
+  def doorkeeper_authorize!(*scopes)
+    super(*scopes)
+    # In addition to Doorkeeper's authorization and scope check, we also verify
+    # that the user has permissions for the scope (through its workgroups).
+    # Unless no scopes were supplied, which means we only want to make sure there
+    # is a valid user.
+    #
+    # If Doorkeeper's +handle_auth_errors+ is set to +:raise+, we don't get here,
+    # but otherwise we need to check whether +super+ rendered an error.
+    doorkeeper_authorize_roles!(*scopes) if scopes.present? && !performed?
+  end
+
+  private
+
+  # Make sure that at least one the given OAuth scopes is valid for the current user's permissions.
+  # @raise Api::Errors::PermissionsRequired
+  def doorkeeper_authorize_roles!(*scopes)
+    unless scopes.any? {|scope| doorkeeper_scope_permitted?(scope) }
+      raise Api::Errors::PermissionRequired.new('Forbidden, no permission')
+    end
+  end
+
+  # Check whether a given OAuth scope is permitted for the current user.
+  # @note This does not validate whether the given scope is a valid scope.
+  # @return [Boolean] Whether the given scope is valid for the current user.
+  # @see https://github.com/foodcoops/foodsoft/issues/582#issuecomment-442513237
+  def doorkeeper_scope_permitted?(scope)
+    scope_parts = scope.split(':')
+    # user sub-scopes like +config:user+ are always permitted
+    if scope_parts.last == 'user'
+      return true
+    end
+
+    case scope_parts.first
+    when 'user'           then true # access to the current user's own profile
+    when 'config'         then current_user.role_admin?
+    when 'users'          then current_user.role_admin?
+    when 'workgroups'     then current_user.role_admin?
+    when 'suppliers'      then current_user.role_suppliers?
+    when 'group_orders'   then current_user.role_orders?
+    when 'finance'        then current_user.role_finance?
+    # please note that offline_access does not belong here, since it is not used for permission checking
+    end
+  end
+end