2 files changed, 29 insertions, 0 deletions
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 4db30e64b4..b64617d084 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -613,6 +613,13 @@ module ActionController
 
     undef_method :to_param
 
+    # Returns duplicate of object including all parameters
+    def deep_dup
+      self.class.new(@parameters.deep_dup).tap do |duplicate|
+        duplicate.permitted = @permitted
+      end
+    end
+
     protected
       attr_reader :parameters
 
diff --git a/actionpack/test/controller/parameters/dup_test.rb b/actionpack/test/controller/parameters/dup_test.rb
index d88891ca30..fb707a1354 100644
--- a/actionpack/test/controller/parameters/dup_test.rb
+++ b/actionpack/test/controller/parameters/dup_test.rb
@@ -1,5 +1,6 @@
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
+require "active_support/core_ext/object/deep_dup"
 
 class ParametersDupTest < ActiveSupport::TestCase
   setup do
@@ -40,4 +41,25 @@ class ParametersDupTest < ActiveSupport::TestCase
     dupped_params.permit!
     assert_not_equal @params, dupped_params
   end
+
+  test "deep_dup content" do
+    dupped_params = @params.deep_dup
+    dupped_params[:person][:age] = "45"
+    dupped_params[:person][:addresses].clear
+
+    assert_not_equal @params[:person][:age], dupped_params[:person][:age]
+    assert_not_equal @params[:person][:addresses], dupped_params[:person][:addresses]
+  end
+
+  test "deep_dup @permitted" do
+    dupped_params = @params.deep_dup
+    dupped_params.permit!
+
+    assert_not @params.permitted?
+  end
+
+  test "deep_dup @permitted is being copied" do
+    @params.permit!
+    assert @params.deep_dup.permitted?
+  end
 end