feat: Enable strict configuration decoding (#19)

* Enable strict configuration decoding

* Verify API version and kind

hack/boilerplate.go.txt

@@ -0,0 +1,15 @@
+/*
+Copyright YEAR The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/

pkg/config/config.go

@@ -9,7 +9,7 @@ import (
 	"github.com/hsbc/cost-manager/pkg/api/v1alpha1"
 	"github.com/hsbc/cost-manager/pkg/controller"
 	"k8s.io/apimachinery/pkg/runtime"
-	"k8s.io/kubectl/pkg/scheme"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
 )
 
 func Load(configFilePath string) (*v1alpha1.CostManagerConfiguration, error) {
@@ -37,13 +37,24 @@ func Load(configFilePath string) (*v1alpha1.CostManagerConfiguration, error) {
 
 func decode(configData []byte) (*v1alpha1.CostManagerConfiguration, error) {
 	config := &v1alpha1.CostManagerConfiguration{}
-	decoder := scheme.Codecs.UniversalDecoder(v1alpha1.SchemeGroupVersion)
 
+	// We enable strict decoding to ensure that we do not accept unknown fields
+	codecFactory := serializer.NewCodecFactory(runtime.NewScheme(), serializer.EnableStrict)
+
+	decoder := codecFactory.UniversalDecoder(v1alpha1.SchemeGroupVersion)
 	err := runtime.DecodeInto(decoder, configData, config)
 	if err != nil {
 		return nil, fmt.Errorf("failed to decode configuration: %s", err)
 	}
 
+	// Verify that the API version and kind are what we expect
+	if config.APIVersion != v1alpha1.SchemeGroupVersion.String() {
+		return nil, fmt.Errorf("invalid API version: %s", config.APIVersion)
+	}
+	if config.Kind != "CostManagerConfiguration" {
+		return nil, fmt.Errorf("invalid kind: %s", config.Kind)
+	}
+
 	return config, nil
 }
 

pkg/config/config_test.go

@@ -5,18 +5,96 @@ import (
 
 	"github.com/hsbc/cost-manager/pkg/api/v1alpha1"
 	"github.com/stretchr/testify/require"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 )
 
 func TestDecode(t *testing.T) {
-	configData := []byte(`
+	tests := map[string]struct {
+		configData []byte
+		valid      bool
+		config     *v1alpha1.CostManagerConfiguration
+	}{
+		"validCloudProviderField": {
+			configData: []byte(`
 apiVersion: cost-manager.io/v1alpha1
 kind: CostManagerConfiguration
 cloudProvider:
   name: gcp
-`)
-	config, err := decode(configData)
-	require.Nil(t, err)
-	require.Equal(t, "gcp", config.CloudProvider.Name)
+`),
+			valid: true,
+			config: &v1alpha1.CostManagerConfiguration{
+				TypeMeta: metav1.TypeMeta{
+					APIVersion: "cost-manager.io/v1alpha1",
+					Kind:       "CostManagerConfiguration",
+				},
+				CloudProvider: v1alpha1.CloudProvider{
+					Name: "gcp",
+				},
+			},
+		},
+		"validControllersField": {
+			configData: []byte(`
+apiVersion: cost-manager.io/v1alpha1
+kind: CostManagerConfiguration
+controllers:
+- spot-migrator
+`),
+			valid: true,
+			config: &v1alpha1.CostManagerConfiguration{
+				TypeMeta: metav1.TypeMeta{
+					APIVersion: "cost-manager.io/v1alpha1",
+					Kind:       "CostManagerConfiguration",
+				},
+				Controllers: []string{"spot-migrator"},
+			},
+		},
+		"noFields": {
+			configData: []byte(`
+apiVersion: cost-manager.io/v1alpha1
+kind: CostManagerConfiguration
+`),
+			valid: true,
+			config: &v1alpha1.CostManagerConfiguration{
+				TypeMeta: metav1.TypeMeta{
+					APIVersion: "cost-manager.io/v1alpha1",
+					Kind:       "CostManagerConfiguration",
+				},
+			},
+		},
+		"unknownAPIVersion": {
+			configData: []byte(`
+apiVersion: foo.io/v1alpha1
+kind: CostManagerConfiguration
+`),
+			valid: false,
+		},
+		"unknownKind": {
+			configData: []byte(`
+apiVersion: cost-manager.io/v1alpha1
+kind: FooConfiguration
+`),
+			valid: false,
+		},
+		"unknownField": {
+			configData: []byte(`
+apiVersion: cost-manager.io/v1alpha1
+kind: CostManagerConfiguration
+foo: bar
+`),
+			valid: false,
+		},
+	}
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			config, err := decode(test.configData)
+			if test.valid {
+				require.Nil(t, err)
+				require.Equal(t, test.config, config)
+			} else {
+				require.NotNil(t, err)
+			}
+		})
+	}
 }
 
 func TestValidate(t *testing.T) {