Remove option to disable http2 for metrics server (#143)

HTTP2 was disabled to mitigate security risks from CVE-2023-44487 and
CVE-2023-39325 which have long since been fixed in Go. Removing the
option that was false by default enables http2 and also reduces some
confusion about why it is an option in the first place.

Signed-off-by: Philip Laine <philip.laine@gmail.com>

cmd/main.go

@@ -112,9 +112,7 @@ func main() {
 		webhookCertKey       string
 		enableLeaderElection bool
 		probeAddr            string
-		enableHTTP2          bool
 		enableWebhooks       bool
-		tlsOpts              []func(*tls.Config)
 	)
 
 	flag.StringVar(&metricsAddr, "metrics-bind-address", "0", "The address the metrics endpoint binds to. "+
@@ -126,8 +124,6 @@ func main() {
 	flag.StringVar(&webhookCertPath, "webhook-cert-path", "", "The directory that contains the webhook certificate.")
 	flag.StringVar(&webhookCertName, "webhook-cert-name", "tls.crt", "The name of the webhook certificate file.")
 	flag.StringVar(&webhookCertKey, "webhook-cert-key", "tls.key", "The name of the webhook key file.")
-	flag.BoolVar(&enableHTTP2, "enable-http2", false,
-		"If set, HTTP/2 will be enabled for the metrics and webhook servers")
 	flag.BoolVar(&enableWebhooks, "enable-webhooks", true, "If set, enable Mutating and Validating webhooks.")
 	opts := zap.Options{
 		Development: true,
@@ -135,6 +131,8 @@ func main() {
 	opts.BindFlags(flag.CommandLine)
 	flag.Parse()
 
+	ctrl.SetLogger(zap.New(zap.UseFlagOptions(&opts)))
+
 	defaultLabelsMap := make(map[string]string)
 	if defaultLabels != "" {
 		for s := range strings.SplitSeq(defaultLabels, ",") {
@@ -146,54 +144,39 @@ func main() {
 		}
 	}
 
-	ctrl.SetLogger(zap.New(zap.UseFlagOptions(&opts)))
+	// Setup webhook server.
+	type TLSOption = func(*tls.Config)
+	certWatcher, tlsOpt, err := func() (*certwatcher.CertWatcher, TLSOption, error) {
+		if webhookCertPath == "" {
+			return nil, nil, nil
+		}
 
-	disableHTTP2 := func(c *tls.Config) {
-		setupLog.Info("disabling http/2")
-		c.NextProtos = []string{"http/1.1"}
-	}
-
-	if !enableHTTP2 {
-		tlsOpts = append(tlsOpts, disableHTTP2)
-	}
-
-	// Create watcher for webhooks certificates
-	var webhookCertWatcher *certwatcher.CertWatcher
-
-	// Initial webhook TLS options
-	webhookTLSOpts := tlsOpts
-
-	if len(webhookCertPath) > 0 {
-		setupLog.Info("Initializing webhook certificate watcher using provided certificates",
-			"webhook-cert-path", webhookCertPath, "webhook-cert-name", webhookCertName, "webhook-cert-key", webhookCertKey)
-
-		var err error
-		webhookCertWatcher, err = certwatcher.New(
+		certWatcher, err := certwatcher.New(
 			filepath.Join(webhookCertPath, webhookCertName),
 			filepath.Join(webhookCertPath, webhookCertKey),
 		)
 		if err != nil {
-			setupLog.Error(err, "Failed to initialize webhook certificate watcher")
-			os.Exit(1)
+			return nil, nil, err
 		}
 
-		webhookTLSOpts = append(webhookTLSOpts, func(config *tls.Config) {
-			config.GetCertificate = webhookCertWatcher.GetCertificate
-		})
-	}
+		tlsOpt := func(config *tls.Config) {
+			config.GetCertificate = certWatcher.GetCertificate
+		}
 
-	webhookServer := webhook.NewServer(webhook.Options{
-		TLSOpts: webhookTLSOpts,
-	})
-
-	metricsServerOptions := metricsserver.Options{
-		BindAddress: metricsAddr,
-		TLSOpts:     tlsOpts,
+		return certWatcher, tlsOpt, nil
+	}()
+	if err != nil {
+		setupLog.Error(err, "Failed to initialize webhook certificate watcher")
+		os.Exit(1)
 	}
+	webhookServer := webhook.NewServer(webhook.Options{TLSOpts: []TLSOption{tlsOpt}})
 
+	// Setup controller manager.
 	mgr, err := ctrl.NewManager(ctrl.GetConfigOrDie(), ctrl.Options{
-		Scheme:                 scheme,
-		Metrics:                metricsServerOptions,
+		Scheme: scheme,
+		Metrics: metricsserver.Options{
+			BindAddress: metricsAddr,
+		},
 		WebhookServer:          webhookServer,
 		HealthProbeBindAddress: probeAddr,
 		LeaderElection:         enableLeaderElection,
@@ -296,9 +279,9 @@ func main() {
 	}
 	// +kubebuilder:scaffold:builder
 
-	if webhookCertWatcher != nil {
+	if certWatcher != nil {
 		setupLog.Info("Adding webhook certificate watcher to manager")
-		if err := mgr.Add(webhookCertWatcher); err != nil {
+		if err := mgr.Add(certWatcher); err != nil {
 			setupLog.Error(err, "unable to add webhook certificate watcher to manager")
 			os.Exit(1)
 		}
@@ -308,7 +291,11 @@ func main() {
 		setupLog.Error(err, "unable to set up health check")
 		os.Exit(1)
 	}
-	if err := mgr.AddReadyzCheck("readyz", mgr.GetWebhookServer().StartedChecker()); err != nil {
+	readyChecker := healthz.Ping
+	if certWatcher != nil {
+		readyChecker = mgr.GetWebhookServer().StartedChecker()
+	}
+	if err := mgr.AddReadyzCheck("readyz", readyChecker); err != nil {
 		setupLog.Error(err, "unable to set up ready check")
 		os.Exit(1)
 	}