Add server signed response

README.md

@@ -248,6 +248,30 @@ def api_authenticate
 end
 ```
 
+### Server signing response
+
+The server can perform a validation of the response.
+
+You can add the validation in the controller :
+
+```ruby
+   class ApplicationController < ActiveController::Base
+     validation_with_api_auth(access_id: 'test', secret_key: 'test', options: { digest: 'sha256' } )
+   end
+```
+
+or specified at every render
+
+```ruby
+   class ApplicationController < ActiveController::Base
+     validation_with_api_auth()
+
+     def index
+       render json: @users, api_auth: { access_id: 'test', secret_key: 'test', options: { digest: 'sha256' }}
+     end
+   end
+```
+
 ## Development
 
 ApiAuth uses bundler for gem dependencies and RSpec for testing. Developing the

lib/api_auth/headers.rb

@@ -30,6 +30,8 @@ def initialize_request_driver(request)
           GrapeRequest.new(request)
         when /ActionDispatch::Request/
           ActionDispatchRequest.new(request)
+        when /ActionDispatch::Response/
+          ActionDispatchRequest.new(request)
         when /ActionController::CgiRequest/
           ActionControllerRequest.new(request)
         when /HTTPI::Request/

lib/api_auth/railtie.rb

@@ -13,7 +13,40 @@ def api_authenticated?(secret_key)
         end
       end
 
+      module ClassMethods
+        def validation_with_api_auth(api_auth_options = nil)
+          ActionController.add_renderer(:json) do |json, options|
+            api_auth_options ||= options[:api_auth]
+            options.delete(:api_auth)
+
+            json = json.to_json(options) unless json.is_a?(String)
+
+            if options[:callback].present?
+              self.content_type = Mime[:js] if content_type.nil? || content_type == Mime[:json]
+
+              "/**/#{options[:callback]}(#{json})"
+            else
+              self.content_type ||= Mime[:json]
+
+              # API AUTH addition headers
+              if api_auth_options
+                response.headers['CONTENT-MD5'] ||= Digest::MD5.base64digest(json)
+                response.headers['Authorization'] ||= ApiAuth.sign!(
+                  request,
+                  api_auth_options[:access_id],
+                  api_auth_options[:secret_key],
+                  api_auth_options[:options] || {}
+                ).env['Authorization']
+              end
+
+              json
+            end
+          end
+        end
+      end
+
       ActionController::Base.send(:include, ControllerMethods::InstanceMethods) if defined?(ActionController::Base)
+      ActionController::Base.send(:extend, ControllerMethods::ClassMethods) if defined?(ActionController::Base)
     end # ControllerMethods
 
     module ActiveResourceExtension # :nodoc: