Add tests for the new cert controllers and some other small refactorings

- Add a unit test for each cert controller
- Make DynamicTLSServingCertProvider an interface and use a mutex
  internally
- Create a shared ToPEM function instead of having two very similar
  functions
- Move the ObservableWithInformerOption test helper to testutils
- Rename some variables and imports

internal/autoregistration/autoregistration_test.go

@@ -17,7 +17,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	kubetesting "k8s.io/client-go/testing"
 	apiregistrationv1 "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1"
-	aggregationv1fake "k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset/fake"
+	aggregatorv1fake "k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset/fake"
 )
 
 func TestUpdateAPIService(t *testing.T) {
@@ -25,14 +25,14 @@ func TestUpdateAPIService(t *testing.T) {
 
 	tests := []struct {
 		name        string
-		mocks       func(*aggregationv1fake.Clientset)
+		mocks       func(*aggregatorv1fake.Clientset)
 		caInput     []byte
 		wantObjects []apiregistrationv1.APIService
 		wantErr     string
 	}{
 		{
 			name: "happy path update when the pre-existing APIService did not already have a CA bundle",
-			mocks: func(c *aggregationv1fake.Clientset) {
+			mocks: func(c *aggregatorv1fake.Clientset) {
 				_ = c.Tracker().Add(&apiregistrationv1.APIService{
 					ObjectMeta: metav1.ObjectMeta{Name: apiServiceName},
 					Spec: apiregistrationv1.APIServiceSpec{
@@ -52,7 +52,7 @@ func TestUpdateAPIService(t *testing.T) {
 		},
 		{
 			name: "happy path update when the pre-existing APIService already had a CA bundle",
-			mocks: func(c *aggregationv1fake.Clientset) {
+			mocks: func(c *aggregatorv1fake.Clientset) {
 				_ = c.Tracker().Add(&apiregistrationv1.APIService{
 					ObjectMeta: metav1.ObjectMeta{Name: apiServiceName},
 					Spec: apiregistrationv1.APIServiceSpec{
@@ -72,7 +72,7 @@ func TestUpdateAPIService(t *testing.T) {
 		},
 		{
 			name: "error on update",
-			mocks: func(c *aggregationv1fake.Clientset) {
+			mocks: func(c *aggregatorv1fake.Clientset) {
 				_ = c.Tracker().Add(&apiregistrationv1.APIService{
 					ObjectMeta: metav1.ObjectMeta{Name: apiServiceName},
 					Spec:       apiregistrationv1.APIServiceSpec{},
@@ -85,7 +85,7 @@ func TestUpdateAPIService(t *testing.T) {
 		},
 		{
 			name: "error on get",
-			mocks: func(c *aggregationv1fake.Clientset) {
+			mocks: func(c *aggregatorv1fake.Clientset) {
 				_ = c.Tracker().Add(&apiregistrationv1.APIService{
 					ObjectMeta: metav1.ObjectMeta{Name: apiServiceName},
 					Spec:       apiregistrationv1.APIServiceSpec{},
@@ -99,7 +99,7 @@ func TestUpdateAPIService(t *testing.T) {
 		},
 		{
 			name: "conflict error on update, followed by successful retry",
-			mocks: func(c *aggregationv1fake.Clientset) {
+			mocks: func(c *aggregatorv1fake.Clientset) {
 				_ = c.Tracker().Add(&apiregistrationv1.APIService{
 					ObjectMeta: metav1.ObjectMeta{Name: apiServiceName},
 					Spec: apiregistrationv1.APIServiceSpec{
@@ -148,7 +148,7 @@ func TestUpdateAPIService(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			ctx := context.Background()
 
-			client := aggregationv1fake.NewSimpleClientset()
+			client := aggregatorv1fake.NewSimpleClientset()
 			if tt.mocks != nil {
 				tt.mocks(client)
 			}

internal/certauthority/certauthority.go

@@ -195,6 +195,16 @@ func toPEM(cert *tls.Certificate, err error) ([]byte, []byte, error) {
 		return nil, nil, err
 	}
 
+	certPEM, keyPEM, err := ToPEM(cert)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return certPEM, keyPEM, nil
+}
+
+// Encode a tls.Certificate into a private key PEM and a cert chain PEM.
+func ToPEM(cert *tls.Certificate) ([]byte, []byte, error) {
 	// Encode the certificate(s) to PEM.
 	certPEMBlocks := make([][]byte, 0, len(cert.Certificate))
 	for _, c := range cert.Certificate {

internal/controller/apicerts/certs_manager.go

@@ -6,10 +6,7 @@ SPDX-License-Identifier: Apache-2.0
 package apicerts
 
 import (
-	"crypto/tls"
-	"crypto/x509"
 	"crypto/x509/pkix"
-	"encoding/pem"
 	"fmt"
 	"time"
 
@@ -25,7 +22,6 @@ import (
 	"github.com/suzerain-io/placeholder-name/internal/autoregistration"
 	"github.com/suzerain-io/placeholder-name/internal/certauthority"
 	placeholdernamecontroller "github.com/suzerain-io/placeholder-name/internal/controller"
-	placeholderv1alpha1 "github.com/suzerain-io/placeholder-name/kubernetes/1.19/api/apis/placeholder/v1alpha1"
 )
 
 const (
@@ -38,28 +34,25 @@ const (
 
 type certsManagerController struct {
 	namespace        string
-	apiServiceName   string
 	k8sClient        kubernetes.Interface
-	aggregatorClient *aggregatorclient.Clientset
+	aggregatorClient aggregatorclient.Interface
 	secretInformer   corev1informers.SecretInformer
 }
 
 func NewCertsManagerController(
 	namespace string,
 	k8sClient kubernetes.Interface,
-	aggregationClient *aggregatorclient.Clientset,
+	aggregatorClient aggregatorclient.Interface,
 	secretInformer corev1informers.SecretInformer,
 	withInformer placeholdernamecontroller.WithInformerOptionFunc,
 ) controller.Controller {
-	apiServiceName := placeholderv1alpha1.SchemeGroupVersion.Version + "." + placeholderv1alpha1.GroupName
 	return controller.New(
 		controller.Config{
 			Name: "certs-manager-controller",
 			Syncer: &certsManagerController{
-				apiServiceName:   apiServiceName,
 				namespace:        namespace,
 				k8sClient:        k8sClient,
-				aggregatorClient: aggregationClient,
+				aggregatorClient: aggregatorClient,
 				secretInformer:   secretInformer,
 			},
 		},
@@ -108,7 +101,7 @@ func (c *certsManagerController) Sync(ctx controller.Context) error {
 	}
 
 	// Write the CA's public key bundle and the serving certs to a secret.
-	tlsPrivateKeyPEM, tlsCertChainPEM, err := pemEncode(aggregatedAPIServerTLSCert)
+	tlsPrivateKeyPEM, tlsCertChainPEM, err := certauthority.ToPEM(aggregatedAPIServerTLSCert)
 	if err != nil {
 		return fmt.Errorf("could not PEM encode serving certificate: %w", err)
 	}
@@ -137,28 +130,3 @@ func (c *certsManagerController) Sync(ctx controller.Context) error {
 	klog.Info("certsManagerController Sync successfully created secret and updated API service")
 	return nil
 }
-
-// Encode a tls.Certificate into a private key PEM and a cert chain PEM.
-func pemEncode(cert *tls.Certificate) ([]byte, []byte, error) {
-	privateKeyDER, err := x509.MarshalPKCS8PrivateKey(cert.PrivateKey)
-	if err != nil {
-		return nil, nil, fmt.Errorf("error marshalling private key: %w", err)
-	}
-	privateKeyPEM := pem.EncodeToMemory(&pem.Block{
-		Type:    "PRIVATE KEY",
-		Headers: nil,
-		Bytes:   privateKeyDER,
-	})
-
-	certChainPEM := make([]byte, 0)
-	for _, certFromChain := range cert.Certificate {
-		certPEMBytes := pem.EncodeToMemory(&pem.Block{
-			Type:    "CERTIFICATE",
-			Headers: nil,
-			Bytes:   certFromChain,
-		})
-		certChainPEM = append(certChainPEM, certPEMBytes...)
-	}
-
-	return privateKeyPEM, certChainPEM, nil
-}

internal/controller/apicerts/certs_manager_test.go

@@ -0,0 +1,333 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package apicerts
+
+import (
+	"context"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	kubeinformers "k8s.io/client-go/informers"
+	kubernetesfake "k8s.io/client-go/kubernetes/fake"
+	coretesting "k8s.io/client-go/testing"
+	apiregistrationv1 "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1"
+	aggregatorfake "k8s.io/kube-aggregator/pkg/client/clientset_generated/clientset/fake"
+
+	"github.com/suzerain-io/controller-go"
+	"github.com/suzerain-io/placeholder-name/internal/testutil"
+	placeholderv1alpha1 "github.com/suzerain-io/placeholder-name/kubernetes/1.19/api/apis/placeholder/v1alpha1"
+)
+
+func TestManagerControllerInformerFilters(t *testing.T) {
+	spec.Run(t, "informer filters", func(t *testing.T, when spec.G, it spec.S) {
+		const installedInNamespace = "some-namespace"
+
+		var r *require.Assertions
+		var observableWithInformerOption *testutil.ObservableWithInformerOption
+		var secretsInformerFilter controller.Filter
+
+		it.Before(func() {
+			r = require.New(t)
+			observableWithInformerOption = testutil.NewObservableWithInformerOption()
+			secretsInformer := kubeinformers.NewSharedInformerFactory(nil, 0).Core().V1().Secrets()
+			_ = NewCertsManagerController(
+				installedInNamespace,
+				nil,
+				nil,
+				secretsInformer,
+				observableWithInformerOption.WithInformer, // make it possible to observe the behavior of the Filters
+			)
+			secretsInformerFilter = observableWithInformerOption.GetFilterForInformer(secretsInformer)
+		})
+
+		when("watching Secret objects", func() {
+			var subject controller.Filter
+			var target, wrongNamespace, wrongName, unrelated *corev1.Secret
+
+			it.Before(func() {
+				subject = secretsInformerFilter
+				target = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "api-serving-cert", Namespace: installedInNamespace}}
+				wrongNamespace = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "api-serving-cert", Namespace: "wrong-namespace"}}
+				wrongName = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "wrong-name", Namespace: installedInNamespace}}
+				unrelated = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "wrong-name", Namespace: "wrong-namespace"}}
+			})
+
+			when("the target Secret changes", func() {
+				it("returns true to trigger the sync method", func() {
+					r.True(subject.Add(target))
+					r.True(subject.Update(target, unrelated))
+					r.True(subject.Update(unrelated, target))
+					r.True(subject.Delete(target))
+				})
+			})
+
+			when("a Secret from another namespace changes", func() {
+				it("returns false to avoid triggering the sync method", func() {
+					r.False(subject.Add(wrongNamespace))
+					r.False(subject.Update(wrongNamespace, unrelated))
+					r.False(subject.Update(unrelated, wrongNamespace))
+					r.False(subject.Delete(wrongNamespace))
+				})
+			})
+
+			when("a Secret with a different name changes", func() {
+				it("returns false to avoid triggering the sync method", func() {
+					r.False(subject.Add(wrongName))
+					r.False(subject.Update(wrongName, unrelated))
+					r.False(subject.Update(unrelated, wrongName))
+					r.False(subject.Delete(wrongName))
+				})
+			})
+
+			when("a Secret with a different name and a different namespace changes", func() {
+				it("returns false to avoid triggering the sync method", func() {
+					r.False(subject.Add(unrelated))
+					r.False(subject.Update(unrelated, unrelated))
+					r.False(subject.Delete(unrelated))
+				})
+			})
+		})
+	}, spec.Parallel(), spec.Report(report.Terminal{}))
+}
+
+func TestManagerControllerSync(t *testing.T) {
+	spec.Run(t, "Sync", func(t *testing.T, when spec.G, it spec.S) {
+		const installedInNamespace = "some-namespace"
+
+		var r *require.Assertions
+
+		var subject controller.Controller
+		var kubeAPIClient *kubernetesfake.Clientset
+		var aggregatorAPIClient *aggregatorfake.Clientset
+		var kubeInformerClient *kubernetesfake.Clientset
+		var kubeInformers kubeinformers.SharedInformerFactory
+		var timeoutContext context.Context
+		var timeoutContextCancel context.CancelFunc
+		var syncContext *controller.Context
+
+		// Defer starting the informers until the last possible moment so that the
+		// nested Before's can keep adding things to the informer caches.
+		var startInformersAndController = func() {
+			// Set this at the last second to allow for injection of server override.
+			subject = NewCertsManagerController(
+				installedInNamespace,
+				kubeAPIClient,
+				aggregatorAPIClient,
+				kubeInformers.Core().V1().Secrets(),
+				controller.WithInformer,
+			)
+
+			// Set this at the last second to support calling subject.Name().
+			syncContext = &controller.Context{
+				Context: timeoutContext,
+				Name:    subject.Name(),
+				Key: controller.Key{
+					Namespace: installedInNamespace,
+					Name:      "api-serving-cert",
+				},
+			}
+
+			// Must start informers before calling TestRunSynchronously()
+			kubeInformers.Start(timeoutContext.Done())
+			controller.TestRunSynchronously(t, subject)
+		}
+
+		it.Before(func() {
+			r = require.New(t)
+
+			timeoutContext, timeoutContextCancel = context.WithTimeout(context.Background(), time.Second*3)
+
+			kubeInformerClient = kubernetesfake.NewSimpleClientset()
+			kubeInformers = kubeinformers.NewSharedInformerFactory(kubeInformerClient, 0)
+			kubeAPIClient = kubernetesfake.NewSimpleClientset()
+			aggregatorAPIClient = aggregatorfake.NewSimpleClientset()
+		})
+
+		it.After(func() {
+			timeoutContextCancel()
+		})
+
+		when("there is not yet an api-serving-cert Secret in the installation namespace or it was deleted", func() {
+			it.Before(func() {
+				unrelatedSecret := &corev1.Secret{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "some other secret",
+						Namespace: installedInNamespace,
+					},
+				}
+				err := kubeInformerClient.Tracker().Add(unrelatedSecret)
+				r.NoError(err)
+			})
+
+			when("the APIService exists", func() {
+				it.Before(func() {
+					apiService := &apiregistrationv1.APIService{
+						ObjectMeta: metav1.ObjectMeta{
+							Name: placeholderv1alpha1.SchemeGroupVersion.Version + "." + placeholderv1alpha1.GroupName,
+						},
+						Spec: apiregistrationv1.APIServiceSpec{
+							CABundle:        nil,
+							VersionPriority: 1234,
+						},
+					}
+					err := aggregatorAPIClient.Tracker().Add(apiService)
+					r.NoError(err)
+				})
+
+				it("creates the api-serving-cert Secret and updates the APIService's ca bundle", func() {
+					startInformersAndController()
+					err := controller.TestSync(t, subject, *syncContext)
+					r.NoError(err)
+
+					// Check all the relevant fields from the create Secret action
+					r.Len(kubeAPIClient.Actions(), 1)
+					actualAction := kubeAPIClient.Actions()[0].(coretesting.CreateActionImpl)
+					r.Equal(schema.GroupVersionResource{Group: "", Version: "v1", Resource: "secrets"}, actualAction.GetResource())
+					r.Equal(installedInNamespace, actualAction.GetNamespace())
+					actualSecret := actualAction.GetObject().(*corev1.Secret)
+					r.Equal("api-serving-cert", actualSecret.Name)
+					r.Equal(installedInNamespace, actualSecret.Namespace)
+					actualCACert := actualSecret.StringData["caCertificate"]
+					actualPrivateKey := actualSecret.StringData["tlsPrivateKey"]
+					actualCertChain := actualSecret.StringData["tlsCertificateChain"]
+					r.NotEmpty(actualCACert)
+					r.NotEmpty(actualPrivateKey)
+					r.NotEmpty(actualCertChain)
+
+					// Validate the created cert using the CA, and also validate the cert's hostname
+					roots := x509.NewCertPool()
+					ok := roots.AppendCertsFromPEM([]byte(actualCACert))
+					r.True(ok)
+					block, _ := pem.Decode([]byte(actualPrivateKey))
+					r.NotNil(block)
+					parsedCert, err := x509.ParseCertificate(block.Bytes)
+					r.NoError(err)
+					opts := x509.VerifyOptions{
+						DNSName: "placeholder-name-api." + installedInNamespace + ".svc",
+						Roots:   roots,
+					}
+					_, err = parsedCert.Verify(opts)
+					r.NoError(err)
+
+					// Check the created cert's validity bounds
+					r.WithinDuration(time.Now(), parsedCert.NotBefore, time.Minute*2)
+					r.WithinDuration(time.Now().Add(24*365*time.Hour), parsedCert.NotAfter, time.Minute*2)
+
+					// TODO How can we validate the tlsCertificateChain?
+
+					// Make sure we updated the APIService caBundle and left it otherwise unchanged
+					r.Len(aggregatorAPIClient.Actions(), 2)
+					r.Equal("get", aggregatorAPIClient.Actions()[0].GetVerb())
+					expectedAPIServiceName := placeholderv1alpha1.SchemeGroupVersion.Version + "." + placeholderv1alpha1.GroupName
+					expectedUpdateAction := coretesting.NewUpdateAction(
+						schema.GroupVersionResource{
+							Group:    apiregistrationv1.GroupName,
+							Version:  "v1",
+							Resource: "apiservices",
+						},
+						"",
+						&apiregistrationv1.APIService{
+							ObjectMeta: metav1.ObjectMeta{
+								Name:      expectedAPIServiceName,
+								Namespace: "",
+							},
+							Spec: apiregistrationv1.APIServiceSpec{
+								VersionPriority: 1234, // only the CABundle is updated, this other field is left unchanged
+								CABundle:        []byte(actualCACert),
+							},
+						},
+					)
+					r.Equal(expectedUpdateAction, aggregatorAPIClient.Actions()[1])
+				})
+
+				when("updating the APIService fails", func() {
+					it.Before(func() {
+						aggregatorAPIClient.PrependReactor(
+							"update",
+							"apiservices",
+							func(_ coretesting.Action) (bool, runtime.Object, error) {
+								return true, nil, errors.New("update failed")
+							},
+						)
+					})
+
+					it("returns the update error", func() {
+						startInformersAndController()
+						err := controller.TestSync(t, subject, *syncContext)
+						r.EqualError(err, "could not update the API service: could not update API service: update failed")
+					})
+				})
+			})
+
+			when("the APIService does not exist", func() {
+				it.Before(func() {
+					unrelatedAPIService := &apiregistrationv1.APIService{
+						ObjectMeta: metav1.ObjectMeta{Name: "some other api service"},
+						Spec:       apiregistrationv1.APIServiceSpec{},
+					}
+					err := aggregatorAPIClient.Tracker().Add(unrelatedAPIService)
+					r.NoError(err)
+				})
+
+				it("returns an error", func() {
+					startInformersAndController()
+					err := controller.TestSync(t, subject, *syncContext)
+					r.Error(err)
+					r.Regexp("could not get existing version of API service: .* not found", err.Error())
+				})
+			})
+
+			when("creating the Secret fails", func() {
+				it.Before(func() {
+					kubeAPIClient.PrependReactor(
+						"create",
+						"secrets",
+						func(_ coretesting.Action) (bool, runtime.Object, error) {
+							return true, nil, errors.New("create failed")
+						},
+					)
+				})
+
+				it("returns the create error", func() {
+					startInformersAndController()
+					err := controller.TestSync(t, subject, *syncContext)
+					r.EqualError(err, "could not create secret: create failed")
+				})
+			})
+		})
+
+		when("there is an api-serving-cert Secret already in the installation namespace", func() {
+			it.Before(func() {
+				apiServingCertSecret := &corev1.Secret{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "api-serving-cert",
+						Namespace: installedInNamespace,
+					},
+				}
+				err := kubeInformerClient.Tracker().Add(apiServingCertSecret)
+				r.NoError(err)
+			})
+
+			it("does not need to make any API calls with its API clients", func() {
+				startInformersAndController()
+				err := controller.TestSync(t, subject, *syncContext)
+				r.NoError(err)
+				r.Empty(kubeAPIClient.Actions())
+				r.Empty(aggregatorAPIClient.Actions())
+			})
+		})
+	}, spec.Parallel(), spec.Report(report.Terminal{}))
+}

internal/controller/apicerts/certs_observer.go

@@ -19,13 +19,13 @@ import (
 
 type certsObserverController struct {
 	namespace           string
-	dynamicCertProvider *provider.DynamicTLSServingCertProvider
+	dynamicCertProvider provider.DynamicTLSServingCertProvider
 	secretInformer      corev1informers.SecretInformer
 }
 
 func NewCertsObserverController(
 	namespace string,
-	dynamicCertProvider *provider.DynamicTLSServingCertProvider,
+	dynamicCertProvider provider.DynamicTLSServingCertProvider,
 	secretInformer corev1informers.SecretInformer,
 	withInformer placeholdernamecontroller.WithInformerOptionFunc,
 ) controller.Controller {
@@ -56,14 +56,12 @@ func (c *certsObserverController) Sync(_ controller.Context) error {
 	if notFound {
 		klog.Info("certsObserverController Sync() found that the secret does not exist yet or was deleted")
 		// The secret does not exist yet or was deleted.
-		c.dynamicCertProvider.CertPEM = nil
-		c.dynamicCertProvider.KeyPEM = nil
+		c.dynamicCertProvider.Set(nil, nil)
 		return nil
 	}
 
 	// Mutate the in-memory cert provider to update with the latest cert values.
-	c.dynamicCertProvider.CertPEM = certSecret.Data[tlsCertificateChainSecretKey]
-	c.dynamicCertProvider.KeyPEM = certSecret.Data[tlsPrivateKeySecretKey]
+	c.dynamicCertProvider.Set(certSecret.Data[tlsCertificateChainSecretKey], certSecret.Data[tlsPrivateKeySecretKey])
 	klog.Info("certsObserverController Sync updated certs in the dynamic cert provider")
 	return nil
 }

internal/controller/apicerts/certs_observer_test.go

@@ -0,0 +1,232 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package apicerts
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	kubeinformers "k8s.io/client-go/informers"
+	kubernetesfake "k8s.io/client-go/kubernetes/fake"
+
+	"github.com/suzerain-io/controller-go"
+	"github.com/suzerain-io/placeholder-name/internal/provider"
+	"github.com/suzerain-io/placeholder-name/internal/testutil"
+)
+
+func TestObserverControllerInformerFilters(t *testing.T) {
+	spec.Run(t, "informer filters", func(t *testing.T, when spec.G, it spec.S) {
+		const installedInNamespace = "some-namespace"
+
+		var r *require.Assertions
+		var observableWithInformerOption *testutil.ObservableWithInformerOption
+		var secretsInformerFilter controller.Filter
+
+		it.Before(func() {
+			r = require.New(t)
+			observableWithInformerOption = testutil.NewObservableWithInformerOption()
+			secretsInformer := kubeinformers.NewSharedInformerFactory(nil, 0).Core().V1().Secrets()
+			_ = NewCertsObserverController(
+				installedInNamespace,
+				nil,
+				secretsInformer,
+				observableWithInformerOption.WithInformer, // make it possible to observe the behavior of the Filters
+			)
+			secretsInformerFilter = observableWithInformerOption.GetFilterForInformer(secretsInformer)
+		})
+
+		when("watching Secret objects", func() {
+			var subject controller.Filter
+			var target, wrongNamespace, wrongName, unrelated *corev1.Secret
+
+			it.Before(func() {
+				subject = secretsInformerFilter
+				target = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "api-serving-cert", Namespace: installedInNamespace}}
+				wrongNamespace = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "api-serving-cert", Namespace: "wrong-namespace"}}
+				wrongName = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "wrong-name", Namespace: installedInNamespace}}
+				unrelated = &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: "wrong-name", Namespace: "wrong-namespace"}}
+			})
+
+			when("the target Secret changes", func() {
+				it("returns true to trigger the sync method", func() {
+					r.True(subject.Add(target))
+					r.True(subject.Update(target, unrelated))
+					r.True(subject.Update(unrelated, target))
+					r.True(subject.Delete(target))
+				})
+			})
+
+			when("a Secret from another namespace changes", func() {
+				it("returns false to avoid triggering the sync method", func() {
+					r.False(subject.Add(wrongNamespace))
+					r.False(subject.Update(wrongNamespace, unrelated))
+					r.False(subject.Update(unrelated, wrongNamespace))
+					r.False(subject.Delete(wrongNamespace))
+				})
+			})
+
+			when("a Secret with a different name changes", func() {
+				it("returns false to avoid triggering the sync method", func() {
+					r.False(subject.Add(wrongName))
+					r.False(subject.Update(wrongName, unrelated))
+					r.False(subject.Update(unrelated, wrongName))
+					r.False(subject.Delete(wrongName))
+				})
+			})
+
+			when("a Secret with a different name and a different namespace changes", func() {
+				it("returns false to avoid triggering the sync method", func() {
+					r.False(subject.Add(unrelated))
+					r.False(subject.Update(unrelated, unrelated))
+					r.False(subject.Delete(unrelated))
+				})
+			})
+		})
+	}, spec.Parallel(), spec.Report(report.Terminal{}))
+}
+
+func TestObserverControllerSync(t *testing.T) {
+	spec.Run(t, "Sync", func(t *testing.T, when spec.G, it spec.S) {
+		const installedInNamespace = "some-namespace"
+
+		var r *require.Assertions
+
+		var subject controller.Controller
+		var kubeInformerClient *kubernetesfake.Clientset
+		var kubeInformers kubeinformers.SharedInformerFactory
+		var timeoutContext context.Context
+		var timeoutContextCancel context.CancelFunc
+		var syncContext *controller.Context
+		var dynamicCertProvider provider.DynamicTLSServingCertProvider
+
+		// Defer starting the informers until the last possible moment so that the
+		// nested Before's can keep adding things to the informer caches.
+		var startInformersAndController = func() {
+			// Set this at the last second to allow for injection of server override.
+			subject = NewCertsObserverController(
+				installedInNamespace,
+				dynamicCertProvider,
+				kubeInformers.Core().V1().Secrets(),
+				controller.WithInformer,
+			)
+
+			// Set this at the last second to support calling subject.Name().
+			syncContext = &controller.Context{
+				Context: timeoutContext,
+				Name:    subject.Name(),
+				Key: controller.Key{
+					Namespace: installedInNamespace,
+					Name:      "api-serving-cert",
+				},
+			}
+
+			// Must start informers before calling TestRunSynchronously()
+			kubeInformers.Start(timeoutContext.Done())
+			controller.TestRunSynchronously(t, subject)
+		}
+
+		it.Before(func() {
+			r = require.New(t)
+
+			timeoutContext, timeoutContextCancel = context.WithTimeout(context.Background(), time.Second*3)
+
+			kubeInformerClient = kubernetesfake.NewSimpleClientset()
+			kubeInformers = kubeinformers.NewSharedInformerFactory(kubeInformerClient, 0)
+			dynamicCertProvider = provider.NewDynamicTLSServingCertProvider()
+		})
+
+		it.After(func() {
+			timeoutContextCancel()
+		})
+
+		when("there is not yet an api-serving-cert Secret in the installation namespace or it was deleted", func() {
+			it.Before(func() {
+				unrelatedSecret := &corev1.Secret{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "some other secret",
+						Namespace: installedInNamespace,
+					},
+				}
+				err := kubeInformerClient.Tracker().Add(unrelatedSecret)
+				r.NoError(err)
+
+				dynamicCertProvider.Set([]byte("some cert"), []byte("some private key"))
+			})
+
+			it("sets the dynamicCertProvider's cert and key to nil", func() {
+				startInformersAndController()
+				err := controller.TestSync(t, subject, *syncContext)
+				r.NoError(err)
+
+				actualCertChain, actualKey := dynamicCertProvider.CurrentCertKeyContent()
+				r.Nil(actualCertChain)
+				r.Nil(actualKey)
+			})
+		})
+
+		when("there is an api-serving-cert Secret with the expected keys already in the installation namespace", func() {
+			it.Before(func() {
+				apiServingCertSecret := &corev1.Secret{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "api-serving-cert",
+						Namespace: installedInNamespace,
+					},
+					Data: map[string][]byte{
+						"caCertificate":       []byte("fake cert"),
+						"tlsPrivateKey":       []byte("fake private key"),
+						"tlsCertificateChain": []byte("fake cert chain"),
+					},
+				}
+				err := kubeInformerClient.Tracker().Add(apiServingCertSecret)
+				r.NoError(err)
+
+				dynamicCertProvider.Set(nil, nil)
+			})
+
+			it("updates the dynamicCertProvider's cert and key", func() {
+				startInformersAndController()
+				err := controller.TestSync(t, subject, *syncContext)
+				r.NoError(err)
+
+				actualCertChain, actualKey := dynamicCertProvider.CurrentCertKeyContent()
+				r.Equal("fake cert chain", string(actualCertChain))
+				r.Equal("fake private key", string(actualKey))
+			})
+		})
+
+		when("the api-serving-cert Secret exists but is missing the expected keys", func() {
+			it.Before(func() {
+				apiServingCertSecret := &corev1.Secret{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "api-serving-cert",
+						Namespace: installedInNamespace,
+					},
+					Data: map[string][]byte{},
+				}
+				err := kubeInformerClient.Tracker().Add(apiServingCertSecret)
+				r.NoError(err)
+
+				dynamicCertProvider.Set(nil, nil)
+			})
+
+			it("set the missing values in the dynamicCertProvider as nil", func() {
+				startInformersAndController()
+				err := controller.TestSync(t, subject, *syncContext)
+				r.NoError(err)
+
+				actualCertChain, actualKey := dynamicCertProvider.CurrentCertKeyContent()
+				r.Nil(actualCertChain)
+				r.Nil(actualKey)
+			})
+		})
+	}, spec.Parallel(), spec.Report(report.Terminal{}))
+}

internal/controller/logindiscovery/publisher_test.go

@@ -24,41 +24,24 @@ import (
 	coretesting "k8s.io/client-go/testing"
 
 	"github.com/suzerain-io/controller-go"
+	"github.com/suzerain-io/placeholder-name/internal/testutil"
 	crdsplaceholderv1alpha1 "github.com/suzerain-io/placeholder-name/kubernetes/1.19/api/apis/crdsplaceholder/v1alpha1"
 	placeholderfake "github.com/suzerain-io/placeholder-name/kubernetes/1.19/client-go/clientset/versioned/fake"
 	placeholderinformers "github.com/suzerain-io/placeholder-name/kubernetes/1.19/client-go/informers/externalversions"
 )
 
-type ObservableWithInformerOption struct {
-	InformerToFilterMap map[controller.InformerGetter]controller.Filter
-}
-
-func NewObservableWithInformerOption() *ObservableWithInformerOption {
-	return &ObservableWithInformerOption{
-		InformerToFilterMap: make(map[controller.InformerGetter]controller.Filter),
-	}
-}
-
-func (owi *ObservableWithInformerOption) WithInformer(
-	getter controller.InformerGetter,
-	filter controller.Filter,
-	opt controller.InformerOption) controller.Option {
-	owi.InformerToFilterMap[getter] = filter
-	return controller.WithInformer(getter, filter, opt)
-}
-
 func TestInformerFilters(t *testing.T) {
 	spec.Run(t, "informer filters", func(t *testing.T, when spec.G, it spec.S) {
 		const installedInNamespace = "some-namespace"
 
 		var r *require.Assertions
-		var observableWithInformerOption *ObservableWithInformerOption
+		var observableWithInformerOption *testutil.ObservableWithInformerOption
 		var configMapInformerFilter controller.Filter
 		var loginDiscoveryConfigInformerFilter controller.Filter
 
 		it.Before(func() {
 			r = require.New(t)
-			observableWithInformerOption = NewObservableWithInformerOption()
+			observableWithInformerOption = testutil.NewObservableWithInformerOption()
 			configMapInformer := kubeinformers.NewSharedInformerFactory(nil, 0).Core().V1().ConfigMaps()
 			loginDiscoveryConfigInformer := placeholderinformers.NewSharedInformerFactory(nil, 0).Crds().V1alpha1().LoginDiscoveryConfigs()
 			_ = NewPublisherController(
@@ -69,8 +52,8 @@ func TestInformerFilters(t *testing.T) {
 				loginDiscoveryConfigInformer,
 				observableWithInformerOption.WithInformer, // make it possible to observe the behavior of the Filters
 			)
-			configMapInformerFilter = observableWithInformerOption.InformerToFilterMap[configMapInformer]
-			loginDiscoveryConfigInformerFilter = observableWithInformerOption.InformerToFilterMap[loginDiscoveryConfigInformer]
+			configMapInformerFilter = observableWithInformerOption.GetFilterForInformer(configMapInformer)
+			loginDiscoveryConfigInformerFilter = observableWithInformerOption.GetFilterForInformer(loginDiscoveryConfigInformer)
 		})
 
 		when("watching ConfigMap objects", func() {

internal/controllermanager/prepare_controllers.go

@@ -33,7 +33,7 @@ const (
 func PrepareControllers(
 	serverInstallationNamespace string,
 	discoveryURLOverride *string,
-	dynamicCertProvider *provider.DynamicTLSServingCertProvider,
+	dynamicCertProvider provider.DynamicTLSServingCertProvider,
 ) (func(ctx context.Context), error) {
 	// Create k8s clients.
 	k8sClient, aggregatorClient, placeholderClient, err := createClients()

internal/provider/dynamic_tls_serving_cert_provider.go

@@ -5,15 +5,40 @@ SPDX-License-Identifier: Apache-2.0
 
 package provider
 
-type DynamicTLSServingCertProvider struct {
-	CertPEM []byte
-	KeyPEM  []byte
+import (
+	"sync"
+
+	"k8s.io/apiserver/pkg/server/dynamiccertificates"
+)
+
+type DynamicTLSServingCertProvider interface {
+	dynamiccertificates.CertKeyContentProvider
+	Set(certPEM, keyPEM []byte)
 }
 
-func (*DynamicTLSServingCertProvider) Name() string {
+type dynamicTLSServingCertProvider struct {
+	certPEM []byte
+	keyPEM  []byte
+	mutex   sync.RWMutex
+}
+
+func NewDynamicTLSServingCertProvider() DynamicTLSServingCertProvider {
+	return &dynamicTLSServingCertProvider{}
+}
+
+func (p *dynamicTLSServingCertProvider) Set(certPEM, keyPEM []byte) {
+	p.mutex.Lock() // acquire a write lock
+	defer p.mutex.Unlock()
+	p.certPEM = certPEM
+	p.keyPEM = keyPEM
+}
+
+func (p *dynamicTLSServingCertProvider) Name() string {
 	return "DynamicTLSServingCertProvider"
 }
 
-func (p *DynamicTLSServingCertProvider) CurrentCertKeyContent() (cert []byte, key []byte) {
-	return p.CertPEM, p.KeyPEM
+func (p *dynamicTLSServingCertProvider) CurrentCertKeyContent() (cert []byte, key []byte) {
+	p.mutex.RLock() // acquire a read lock
+	defer p.mutex.RUnlock()
+	return p.certPEM, p.keyPEM
 }

internal/server/server.go

@@ -27,7 +27,7 @@ import (
 
 // App is an object that represents the placeholder-name-server application.
 type App struct {
-	serverCommand *cobra.Command
+	cmd *cobra.Command
 
 	// CLI flags
 	configPath                 string
@@ -48,27 +48,27 @@ func New(ctx context.Context, args []string, stdout, stderr io.Writer) *App {
 }
 
 // Run the server.
-func (app *App) Run() error {
-	return app.serverCommand.Execute()
+func (a *App) Run() error {
+	return a.cmd.Execute()
 }
 
 // Create the server command and save it into the App.
-func (app *App) addServerCommand(ctx context.Context, args []string, stdout, stderr io.Writer) {
+func (a *App) addServerCommand(ctx context.Context, args []string, stdout, stderr io.Writer) {
 	cmd := &cobra.Command{
 		Use: `placeholder-name-server`,
 		Long: "placeholder-name-server provides a generic API for mapping an external\n" +
 			"credential from somewhere to an internal credential to be used for\n" +
 			"authenticating to the Kubernetes API.",
-		RunE: func(cmd *cobra.Command, args []string) error { return app.runServer(ctx) },
+		RunE: func(cmd *cobra.Command, args []string) error { return a.runServer(ctx) },
 		Args: cobra.NoArgs,
 	}
 
 	cmd.SetArgs(args)
 	cmd.SetOut(stdout)
 	cmd.SetErr(stderr)
-	addCommandlineFlagsToCommand(cmd, app)
+	addCommandlineFlagsToCommand(cmd, a)
 
-	app.serverCommand = cmd
+	a.cmd = cmd
 }
 
 // Define the app's commandline flags.
@@ -104,15 +104,15 @@ func addCommandlineFlagsToCommand(cmd *cobra.Command, app *App) {
 }
 
 // Boot the aggregated API server, which will in turn boot the controllers.
-func (app *App) runServer(ctx context.Context) error {
+func (a *App) runServer(ctx context.Context) error {
 	// Read the server config file.
-	cfg, err := config.FromPath(app.configPath)
+	cfg, err := config.FromPath(a.configPath)
 	if err != nil {
 		return fmt.Errorf("could not load config: %w", err)
 	}
 
 	// Load the Kubernetes cluster signing CA.
-	k8sClusterCA, err := certauthority.Load(app.clusterSigningCertFilePath, app.clusterSigningKeyFilePath)
+	k8sClusterCA, err := certauthority.Load(a.clusterSigningCertFilePath, a.clusterSigningKeyFilePath)
 	if err != nil {
 		return fmt.Errorf("could not load cluster signing CA: %w", err)
 	}
@@ -124,7 +124,7 @@ func (app *App) runServer(ctx context.Context) error {
 	}
 
 	// Discover in which namespace we are installed.
-	podInfo, err := downward.Load(app.downwardAPIPath)
+	podInfo, err := downward.Load(a.downwardAPIPath)
 	if err != nil {
 		return fmt.Errorf("could not read pod metadata: %w", err)
 	}
@@ -135,7 +135,7 @@ func (app *App) runServer(ctx context.Context) error {
 	// is stored in a k8s Secret. Therefore it also effectively acting as
 	// an in-memory cache of what is stored in the k8s Secret, helping to
 	// keep incoming requests fast.
-	dynamicCertProvider := &provider.DynamicTLSServingCertProvider{}
+	dynamicCertProvider := provider.NewDynamicTLSServingCertProvider()
 
 	// Prepare to start the controllers, but defer actually starting them until the
 	// post start hook of the aggregated API server.
@@ -171,7 +171,7 @@ func (app *App) runServer(ctx context.Context) error {
 
 // Create a configuration for the aggregated API server.
 func getAggregatedAPIServerConfig(
-	dynamicCertProvider *provider.DynamicTLSServingCertProvider,
+	dynamicCertProvider provider.DynamicTLSServingCertProvider,
 	webhookTokenAuthenticator *webhook.WebhookTokenAuthenticator,
 	ca *certauthority.CA,
 	startControllersPostStartHook func(context.Context),

internal/server/server_test.go

@@ -78,7 +78,7 @@ func TestCommand(t *testing.T) {
 			stderr := bytes.NewBuffer([]byte{})
 
 			a := New(context.Background(), test.args, stdout, stderr)
-			a.serverCommand.RunE = func(cmd *cobra.Command, args []string) error {
+			a.cmd.RunE = func(cmd *cobra.Command, args []string) error {
 				return nil
 			}
 			err := a.Run()

internal/testutil/observable_with_informer_option.go

@@ -0,0 +1,30 @@
+/*
+Copyright 2020 VMware, Inc.
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package testutil
+
+import "github.com/suzerain-io/controller-go"
+
+type ObservableWithInformerOption struct {
+	InformerToFilterMap map[controller.InformerGetter]controller.Filter
+}
+
+func NewObservableWithInformerOption() *ObservableWithInformerOption {
+	return &ObservableWithInformerOption{
+		InformerToFilterMap: make(map[controller.InformerGetter]controller.Filter),
+	}
+}
+
+func (i *ObservableWithInformerOption) WithInformer(
+	getter controller.InformerGetter,
+	filter controller.Filter,
+	opt controller.InformerOption) controller.Option {
+	i.InformerToFilterMap[getter] = filter
+	return controller.WithInformer(getter, filter, opt)
+}
+
+func (i *ObservableWithInformerOption) GetFilterForInformer(getter controller.InformerGetter) controller.Filter {
+	return i.InformerToFilterMap[getter]
+}