WTF-539 Add missing vendored dependencies back

vendor/k8s.io/client-go/util/cert/pem.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2014 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 cert
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+)
+
+const (
+	// CertificateBlockType is a possible value for pem.Block.Type.
+	CertificateBlockType = "CERTIFICATE"
+	// CertificateRequestBlockType is a possible value for pem.Block.Type.
+	CertificateRequestBlockType = "CERTIFICATE REQUEST"
+)
+
+// ParseCertsPEM returns the x509.Certificates contained in the given PEM-encoded byte array
+// Returns an error if a certificate could not be parsed, or if the data does not contain any certificates
+func ParseCertsPEM(pemCerts []byte) ([]*x509.Certificate, error) {
+	ok := false
+	certs := []*x509.Certificate{}
+	for len(pemCerts) > 0 {
+		var block *pem.Block
+		block, pemCerts = pem.Decode(pemCerts)
+		if block == nil {
+			break
+		}
+		// Only use PEM "CERTIFICATE" blocks without extra headers
+		if block.Type != CertificateBlockType || len(block.Headers) != 0 {
+			continue
+		}
+
+		cert, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			return certs, err
+		}
+
+		certs = append(certs, cert)
+		ok = true
+	}
+
+	if !ok {
+		return certs, errors.New("data does not contain any valid RSA or ECDSA certificates")
+	}
+	return certs, nil
+}