fix(kuma-cp): guard the nil version in metadata (#3969)

Signed-off-by: Jakub Dyszkiewicz <jakub.dyszkiewicz@gmail.com>
(cherry picked from commit 7f5ae2b)

pkg/core/xds/metadata.go

@@ -131,6 +131,9 @@ func (m *DataplaneMetadata) GetVersion() *mesh_proto.Version {
 }
 
 func DataplaneMetadataFromXdsMetadata(xdsMetadata *structpb.Struct) *DataplaneMetadata {
+	// Be extra careful here about nil checks since xdsMetadata is a "user" input.
+	// Even if we know that something should not be nil since we are generating metadata,
+	// the DiscoveryRequest can still be crafted manually to crash the CP.
 	metadata := DataplaneMetadata{}
 	if xdsMetadata == nil {
 		return &metadata
@@ -172,7 +175,9 @@ func DataplaneMetadataFromXdsMetadata(xdsMetadata *structpb.Struct) *DataplaneMe
 		for field, val := range value.GetStructValue().GetFields() {
 			if strings.HasPrefix(field, FieldPrefixDependenciesVersion) {
 				dependencyName := strings.TrimPrefix(field, FieldPrefixDependenciesVersion+".")
-				metadata.Version.Dependencies[dependencyName] = val.GetStringValue()
+				if metadata.GetVersion().GetDependencies() != nil {
+					metadata.Version.Dependencies[dependencyName] = val.GetStringValue()
+				}
 			} else {
 				dynamicMetadata[field] = val.GetStringValue()
 			}

pkg/core/xds/metadata_test.go

@@ -56,6 +56,28 @@ var _ = Describe("DataplaneMetadataFromXdsMetadata", func() {
 				EmptyDNSPort: 8001,
 			},
 		}),
+		Entry("should ignore dependencies version provided through metadata if version is not set at all", testCase{
+			node: &structpb.Struct{
+				Fields: map[string]*structpb.Value{
+					"dynamicMetadata": {
+						Kind: &structpb.Value_StructValue{
+							StructValue: &structpb.Struct{
+								Fields: map[string]*structpb.Value{
+									"version.dependencies.coredns": {
+										Kind: &structpb.Value_StringValue{
+											StringValue: "8000",
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+			expected: xds.DataplaneMetadata{
+				DynamicMetadata: map[string]string{},
+			},
+		}),
 	)
 
 	It("should parse version", func() { // this has to be separate test because Equal does not work on proto