[v0.5] Prevent dropping unknown cluster fields (rancher#516)

* Prevents dropping unknown cluster fields

Signed-off-by: Dharmit Shah <dharmit.shah@suse.com>

* add test for v3 cluster mutator & add rke to replace in go.mod

adding rke to replace section will avoid pulling in rc versions
when updating pkg/apis in webhook

go.mod

@@ -5,6 +5,7 @@ go 1.22.0
 toolchain go1.22.7
 
 replace (
+	github.com/rancher/rke => github.com/rancher/rke v1.6.2
 	k8s.io/api => k8s.io/api v0.30.1
 	k8s.io/apiextensions-apiserver => k8s.io/apiextensions-apiserver v0.30.1
 	k8s.io/apimachinery => k8s.io/apimachinery v0.30.1

pkg/resources/management.cattle.io/v3/cluster/mutator.go

@@ -1,6 +1,7 @@
 package cluster
 
 import (
+	"encoding/json"
 	"fmt"
 	"reflect"
 
@@ -59,6 +60,10 @@ func (m *ManagementClusterMutator) Admit(request *admission.Request) (*admission
 	if err != nil {
 		return nil, fmt.Errorf("failed to get old and new clusters from request: %w", err)
 	}
+	newClusterRaw, err := json.Marshal(newCluster)
+	if err != nil {
+		return nil, fmt.Errorf("unable to re-marshal new cluster: %w", err)
+	}
 	// no need to mutate the local cluster, or imported cluster which represents a KEv2 cluster (GKE/EKS/AKS) or v1 Provisioning Cluster
 	if newCluster.Name == "local" || newCluster.Spec.RancherKubernetesEngineConfig == nil {
 		return admission.ResponseAllowed(), nil
@@ -94,7 +99,9 @@ func (m *ManagementClusterMutator) Admit(request *admission.Request) (*admission
 	}
 
 	response := &admissionv1.AdmissionResponse{}
-	if err := patch.CreatePatch(request.Object.Raw, newCluster, response); err != nil {
+	// we use the re-marshalled new cluster to make sure that the patch doesn't drop "unknown" fields which were
+	// in the json, but not in the cluster struct. This can occur due to out of date RKE versions
+	if err := patch.CreatePatch(newClusterRaw, newCluster, response); err != nil {
 		return response, fmt.Errorf("failed to create patch: %w", err)
 	}
 	response.Allowed = true

pkg/resources/management.cattle.io/v3/cluster/mutator_test.go

@@ -0,0 +1,46 @@
+package cluster
+
+import (
+	"encoding/json"
+	"testing"
+
+	v3 "github.com/rancher/rancher/pkg/apis/management.cattle.io/v3"
+	"github.com/rancher/webhook/pkg/admission"
+	data2 "github.com/rancher/wrangler/v3/pkg/data"
+	"github.com/stretchr/testify/assert"
+	admissionv1 "k8s.io/api/admission/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+func TestAdmitPreserveUnknownFields(t *testing.T) {
+	cluster := &v3.Cluster{}
+	data, err := data2.Convert(cluster)
+	assert.Nil(t, err)
+
+	data.SetNested("test", "spec", "rancherKubernetesEngineConfig", "network", "aciNetworkProvider", "apicUserKeyTest")
+	raw, err := json.Marshal(data)
+	assert.Nil(t, err)
+
+	request := &admission.Request{
+		AdmissionRequest: admissionv1.AdmissionRequest{
+			Object: runtime.RawExtension{
+				Raw: raw,
+			},
+			OldObject: runtime.RawExtension{
+				Raw: raw,
+			},
+		},
+	}
+
+	m := ManagementClusterMutator{}
+
+	request.Operation = admissionv1.Create
+	response, err := m.Admit(request)
+	assert.Nil(t, err)
+	assert.Nil(t, response.Patch)
+
+	request.Operation = admissionv1.Update
+	response, err = m.Admit(request)
+	assert.Nil(t, err)
+	assert.Nil(t, response.Patch)
+}