Add mutating webhook to set fsGroupChangePolicy field (#582)

* Add mutating webhook to set fsGroupChangePolicy field

* Added decoder, debug logging

* Fix path

* Add missing name

* Fix typo

* Add sample podAnnotator

* Try defaulter

* Do webhook registration earlier

* Add webhook server configuration annotations

* Test cert-dir annotation

* Remove webhook-server annotation

* Fix typo

* Logging

* Add webhook server

* Naming

* Formatting

* Try different registration

* Move registration after start

* Try registering FsGroupPolicySetter again

* Move registration back up again

* ...

* use port 9443 again

* Update annotation

* Add scheme

* Fix setting FSGroupChangePolicy

* Remove samples

* Make webhook configurable

* Remove useless check

* Since fsGroup is set by default, also enable webhook by default

* Move code

* Remove  webhook.Options (we're using the default port anyway)

main.go

@@ -17,19 +17,23 @@ import (
 	"github.com/metal-stack/v"
 	coreosv1 "github.com/prometheus-operator/prometheus-operator/pkg/apis/monitoring/v1"
 	zalando "github.com/zalando/postgres-operator/pkg/apis/acid.zalan.do/v1"
+	appsv1 "k8s.io/api/apps/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	clientgoscheme "k8s.io/client-go/kubernetes/scheme"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
 	"k8s.io/client-go/tools/clientcmd"
 	ctrl "sigs.k8s.io/controller-runtime"
 	"sigs.k8s.io/controller-runtime/pkg/log/zap"
 	metricsserver "sigs.k8s.io/controller-runtime/pkg/metrics/server"
+	"sigs.k8s.io/controller-runtime/pkg/webhook"
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
 
 	databasev1 "github.com/fi-ts/postgreslet/api/v1"
 	"github.com/fi-ts/postgreslet/controllers"
 	"github.com/fi-ts/postgreslet/pkg/etcdmanager"
 	"github.com/fi-ts/postgreslet/pkg/lbmanager"
 	"github.com/fi-ts/postgreslet/pkg/operatormanager"
+	"github.com/fi-ts/postgreslet/pkg/webhooks"
 	firewall "github.com/metal-stack/firewall-controller/api/v1"
 	"github.com/spf13/viper"
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
@@ -84,6 +88,7 @@ const (
 	tlsClusterIssuerFlg                    = "tls-cluster-issuer"
 	tlsSubDomainFlg                        = "tls-sub-domain"
 	enablePatroniFailsafeModeFlg           = "enable-patroni-failsafe-mode"
+	enableFsGroupChangePolicyWebhookFlg    = "enable-fsgroup-change-policy-webhook"
 )
 
 var (
@@ -98,6 +103,7 @@ func init() {
 	_ = firewall.AddToScheme(scheme)
 	_ = zalando.AddToScheme(scheme)
 	_ = coreosv1.AddToScheme(scheme)
+	_ = appsv1.AddToScheme(scheme)
 	// +kubebuilder:scaffold:scheme
 	_ = cmapi.AddToScheme(scheme)
 }
@@ -143,6 +149,7 @@ func main() {
 		enableBootstrapStandbyFromS3        bool
 		enableSuperUserForDBO               bool
 		enablePatroniFailsafeMode           bool
+		enableFsGroupChangePolicyWebhook    bool
 
 		portRangeStart                        int
 		portRangeSize                         int
@@ -305,6 +312,9 @@ func main() {
 	viper.SetDefault(enablePatroniFailsafeModeFlg, true)
 	enablePatroniFailsafeMode = viper.GetBool(enablePatroniFailsafeModeFlg)
 
+	viper.SetDefault(enableFsGroupChangePolicyWebhookFlg, true)
+	enableFsGroupChangePolicyWebhook = viper.GetBool(enableFsGroupChangePolicyWebhookFlg)
+
 	ctrl.Log.Info("flag",
 		metricsAddrSvcMgrFlg, metricsAddrSvcMgr,
 		metricsAddrCtrlMgrFlg, metricsAddrCtrlMgr,
@@ -349,6 +359,7 @@ func main() {
 		tlsClusterIssuerFlg, tlsClusterIssuer,
 		tlsSubDomainFlg, tlsSubDomain,
 		enablePatroniFailsafeModeFlg, enablePatroniFailsafeMode,
+		enableFsGroupChangePolicyWebhookFlg, enableFsGroupChangePolicyWebhook,
 	)
 
 	svcClusterConf := ctrl.GetConfigOrDie()
@@ -486,6 +497,19 @@ func main() {
 	}
 	// +kubebuilder:scaffold:builder
 
+	if enableFsGroupChangePolicyWebhook {
+		svcClusterMgr.GetWebhookServer().Register(
+			"/mutate-apps-v1-statefulset",
+			&webhook.Admission{
+				Handler: &webhooks.FsGroupChangePolicySetter{
+					SvcClient: svcClusterMgr.GetClient(),
+					Decoder:   admission.NewDecoder(svcClusterMgr.GetScheme()),
+					Log:       ctrl.Log.WithName("webhooks").WithName("FsGroupChangePolicySetter"),
+				},
+			},
+		)
+	}
+
 	ctx := context.Background()
 
 	// update all existing operators to the current version
@@ -506,4 +530,5 @@ func main() {
 		setupLog.Error(err, "problem running control plane cluster manager")
 		os.Exit(1)
 	}
+
 }

pkg/webhooks/fsGroupChangePolicySetter.go

@@ -0,0 +1,51 @@
+package webhooks
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+
+	"github.com/go-logr/logr"
+	appsv1 "k8s.io/api/apps/v1"
+	v1 "k8s.io/api/core/v1"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+)
+
+// +kubebuilder:webhook:path=/mutate-apps-v1-statefulset,mutating=true,failurePolicy=ignore,groups=apps,resources=statefulsets,verbs=create;update,versions=v1,name=fsgroupchangepolicy.postgres.fits.cloud
+
+// FsGroupChangePolicySetter Adds securityContext.fsGroupChangePolicy=OnRootMismatch when the securityContext.fsGroup field is set
+type FsGroupChangePolicySetter struct {
+	SvcClient client.Client
+	Decoder   *admission.Decoder
+	Log       logr.Logger
+}
+
+func (a *FsGroupChangePolicySetter) Handle(ctx context.Context, req admission.Request) admission.Response {
+	log := a.Log.WithValues("name", req.Name, "ns", req.Namespace)
+	log.V(1).Info("handling admission request")
+
+	sts := &appsv1.StatefulSet{}
+	err := a.Decoder.Decode(req, sts)
+	if err != nil {
+		log.Error(err, "failed to decode request")
+		return admission.Errored(http.StatusBadRequest, err)
+	}
+
+	// when the fsGroup field is set, also set the fsGroupChangePolicy to OnRootMismatch
+	if sts.Spec.Template.Spec.SecurityContext != nil && sts.Spec.Template.Spec.SecurityContext.FSGroup != nil {
+		p := v1.FSGroupChangeOnRootMismatch
+		sts.Spec.Template.Spec.SecurityContext.FSGroupChangePolicy = &p
+		log.V(1).Info("Mutating StatefulSet", "sts", sts)
+	}
+
+	marshaledSts, err := json.Marshal(sts)
+	if err != nil {
+		log.Error(err, "failed to marshal response")
+		return admission.Errored(http.StatusInternalServerError, err)
+	}
+
+	log.V(1).Info("done")
+	return admission.PatchResponseFromRaw(req.Object.Raw, marshaledSts)
+}