Move pkg/kubectl/util/certificate to staging

Kubernetes-commit: 541cb300c74c6d9b4d02fa3199f5a100c3108860

pkg/util/certificate/certificate.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2016 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 certificate
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+
+	certificatesv1beta1 "k8s.io/api/certificates/v1beta1"
+)
+
+// TODO(yue9944882): Remove this helper package once it's copied to k/api
+
+// ParseCSR extracts the CSR from the API object and decodes it.
+func ParseCSR(obj *certificatesv1beta1.CertificateSigningRequest) (*x509.CertificateRequest, error) {
+	// extract PEM from request object
+	pemBytes := obj.Spec.Request
+	block, _ := pem.Decode(pemBytes)
+	if block == nil || block.Type != "CERTIFICATE REQUEST" {
+		return nil, errors.New("PEM block type must be CERTIFICATE REQUEST")
+	}
+	csr, err := x509.ParseCertificateRequest(block.Bytes)
+	if err != nil {
+		return nil, err
+	}
+	return csr, nil
+}