Validate CABundle when writing CRD

Kubernetes-commit: a5791b344c04ded4f443c7e134242a29bd0e2bac

pkg/util/webhook/validation.go

@@ -23,8 +23,18 @@ import (
 
 	"k8s.io/apimachinery/pkg/util/validation"
 	"k8s.io/apimachinery/pkg/util/validation/field"
+	"k8s.io/client-go/transport"
 )
 
+func ValidateCABundle(fldPath *field.Path, caBundle []byte) field.ErrorList {
+	var allErrors field.ErrorList
+	_, err := transport.TLSConfigFor(&transport.Config{TLS: transport.TLSConfig{CAData: caBundle}})
+	if err != nil {
+		allErrors = append(allErrors, field.Invalid(fldPath, caBundle, err.Error()))
+	}
+	return allErrors
+}
+
 // ValidateWebhookURL validates webhook's URL.
 func ValidateWebhookURL(fldPath *field.Path, URL string, forceHttps bool) field.ErrorList {
 	var allErrors field.ErrorList

pkg/util/webhook/validation_test.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package webhook
+
+import (
+	"testing"
+
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+// exampleCert was generated from crypto/tls/generate_cert.go with the following command:
+//
+//	go run generate_cert.go  --rsa-bits 2048 --host example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
+var exampleCert = []byte(`-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`)
+
+func TestValidateCABundle(t *testing.T) {
+	tests := []struct {
+		name      string
+		caBundle  []byte
+		expectErr bool
+	}{
+		{
+			name:      "nil caBundle is valid",
+			caBundle:  nil,
+			expectErr: false,
+		}, {
+			name:      "empty caBundle is valid",
+			caBundle:  []byte(""),
+			expectErr: false,
+		}, {
+			name:      "non empty caBundle with invalid certificate should not validate",
+			caBundle:  []byte("bogus"),
+			expectErr: true,
+		}, {
+			name:      "non empty caBundle with no certificate should not validate",
+			caBundle:  []byte("Cg=="),
+			expectErr: true,
+		}, {
+			name:      "non empty caBundle with valid certificate should validate",
+			caBundle:  exampleCert,
+			expectErr: false,
+		},
+	}
+
+	for _, tc := range tests {
+		errList := ValidateCABundle(field.NewPath(""), tc.caBundle)
+		if len(errList) > 0 && !tc.expectErr {
+			t.Errorf("Expected no error for test %s, got %v", tc.name, errList)
+		} else if len(errList) == 0 && tc.expectErr {
+			t.Errorf("Expected error for test %s, received no error", tc.name)
+		}
+	}
+}