Merge pull request #67910 from liztio/cert-renewal

Automatic merge from submit-queue (batch tested with PRs 64283, 67910, 67803, 68100). If you want to cherry-pick this change to another branch, please follow the instructions here: https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md.

Kubeadm Cert Renewal

**What this PR does / why we need it**:

adds explicit support for renewal of certificates via command

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes kubernetes/kubeadm#206

**Special notes for your reviewer**:
The targeted documentation is at kubernetes/website#9712

**Release note**:

```release-note
Adds the commands `kubeadm alpha phases renew <cert-name>`
```

cmd/kubeadm/app/cmd/options/BUILD

@@ -3,6 +3,7 @@ load("@io_bazel_rules_go//go:def.bzl", "go_library")
 go_library(
     name = "go_default_library",
     srcs = [
+        "certs.go",
         "generic.go",
         "token.go",
     ],

cmd/kubeadm/app/cmd/options/certs.go

@@ -0,0 +1,24 @@
+/*
+Copyright 2018 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 options
+
+import "github.com/spf13/pflag"
+
+// AddCertificateDirFlag adds the --certs-dir flag to the given flagset
+func AddCertificateDirFlag(fs *pflag.FlagSet, certsDir *string) {
+	fs.StringVar(certsDir, "cert-dir", *certsDir, "The path where to save the certificates")
+}

cmd/kubeadm/app/cmd/phases/BUILD

@@ -93,7 +93,10 @@ filegroup(
 
 filegroup(
     name = "all-srcs",
-    srcs = [":package-srcs"],
+    srcs = [
+        ":package-srcs",
+        "//cmd/kubeadm/app/cmd/phases/certs:all-srcs",
+    ],
     tags = ["automanaged"],
     visibility = ["//visibility:public"],
 )

cmd/kubeadm/app/cmd/phases/certs.go

@@ -25,6 +25,7 @@ import (
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmscheme "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/scheme"
 	kubeadmapiv1alpha3 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha3"
+	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
 	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	certsphase "k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
@@ -184,8 +185,8 @@ func getSANDescription(certSpec *certsphase.KubeadmCert) string {
 }
 
 func addFlags(cmd *cobra.Command, cfgPath *string, cfg *kubeadmapiv1alpha3.InitConfiguration, addAPIFlags bool) {
-	cmd.Flags().StringVar(cfgPath, "config", *cfgPath, "Path to kubeadm config file. WARNING: Usage of a configuration file is experimental")
+	options.AddCertificateDirFlag(cmd.Flags(), &cfg.CertificatesDir)
-	cmd.Flags().StringVar(&cfg.CertificatesDir, "cert-dir", cfg.CertificatesDir, "The path where to save the certificates")
+	options.AddConfigFlag(cmd.Flags(), cfgPath)
 	if addAPIFlags {
 		cmd.Flags().StringVar(&cfg.Networking.DNSDomain, "service-dns-domain", cfg.Networking.DNSDomain, "Alternative domain for services, to use for the API server serving cert")
 		cmd.Flags().StringVar(&cfg.Networking.ServiceSubnet, "service-cidr", cfg.Networking.ServiceSubnet, "Alternative range of IP address for service VIPs, from which derives the internal API server VIP that will be added to the API Server serving cert")

cmd/kubeadm/app/cmd/phases/certs/BUILD

@@ -0,0 +1,50 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["renew.go"],
+    importpath = "k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/certs",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//cmd/kubeadm/app/apis/kubeadm/scheme:go_default_library",
+        "//cmd/kubeadm/app/apis/kubeadm/v1alpha3:go_default_library",
+        "//cmd/kubeadm/app/cmd/options:go_default_library",
+        "//cmd/kubeadm/app/cmd/util:go_default_library",
+        "//cmd/kubeadm/app/constants:go_default_library",
+        "//cmd/kubeadm/app/phases/certs:go_default_library",
+        "//cmd/kubeadm/app/phases/certs/renewal:go_default_library",
+        "//cmd/kubeadm/app/util:go_default_library",
+        "//cmd/kubeadm/app/util/config:go_default_library",
+        "//cmd/kubeadm/app/util/kubeconfig:go_default_library",
+        "//pkg/util/normalizer:go_default_library",
+        "//vendor/github.com/spf13/cobra:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["renewal_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//cmd/kubeadm/app/constants:go_default_library",
+        "//cmd/kubeadm/app/phases/certs/pkiutil:go_default_library",
+        "//cmd/kubeadm/test:go_default_library",
+        "//cmd/kubeadm/test/certs:go_default_library",
+        "//cmd/kubeadm/test/cmd:go_default_library",
+        "//vendor/github.com/spf13/cobra:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

cmd/kubeadm/app/cmd/phases/certs/renew.go

@@ -0,0 +1,156 @@
+/*
+Copyright 2018 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 renew
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+
+	kubeadmscheme "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/scheme"
+	kubeadmapiv1alpha3 "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha3"
+	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/options"
+	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
+	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
+	certsphase "k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs/renewal"
+	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
+	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
+	kubeconfigutil "k8s.io/kubernetes/cmd/kubeadm/app/util/kubeconfig"
+	"k8s.io/kubernetes/pkg/util/normalizer"
+)
+
+var (
+	genericLongDesc = normalizer.LongDesc(`
+		Renews the %[1]s, and saves them into %[2]s.cert and %[2]s.key files.
+
+    Extra attributes such as SANs will be based on the existing certificates, there is no need to resupply them.
+`)
+	allLongDesc = normalizer.LongDesc(`
+    Renews all known certificates necessary to run the control plan. Renewals are run unconditionally, regardless
+    of expiration date. Renewals can also be run individually for more control.
+`)
+)
+
+// NewCmdCertsRenewal creates a new `cert renew` command.
+func NewCmdCertsRenewal() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "renew",
+		Short: "Renews certificates for a kubernetes cluster",
+		Long:  cmdutil.MacroCommandLongDescription,
+		RunE:  cmdutil.SubCmdRunE("renew"),
+	}
+
+	cmd.AddCommand(getRenewSubCommands()...)
+
+	return cmd
+}
+
+type renewConfig struct {
+	cfgPath        string
+	kubeconfigPath string
+	cfg            kubeadmapiv1alpha3.InitConfiguration
+	useAPI         bool
+}
+
+func getRenewSubCommands() []*cobra.Command {
+	cfg := &renewConfig{
+		kubeconfigPath: constants.GetAdminKubeConfigPath(),
+	}
+	// Default values for the cobra help text
+	kubeadmscheme.Scheme.Default(&cfg.cfg)
+
+	certTree, err := certsphase.GetDefaultCertList().AsMap().CertTree()
+	kubeadmutil.CheckErr(err)
+
+	cmdList := []*cobra.Command{}
+	allCmds := []func() error{}
+
+	for caCert, certs := range certTree {
+		// Don't offer to renew CAs; would cause serious consequences
+		for _, cert := range certs {
+			cmd := makeCommandForRenew(cert, caCert, cfg)
+			cmdList = append(cmdList, cmd)
+			allCmds = append(allCmds, cmd.Execute)
+		}
+	}
+
+	allCmd := &cobra.Command{
+		Use:   "all",
+		Short: "renew all available certificates",
+		Long:  allLongDesc,
+		Run: func(*cobra.Command, []string) {
+			for _, cmd := range allCmds {
+				err := cmd()
+				kubeadmutil.CheckErr(err)
+			}
+		},
+	}
+	addFlags(allCmd, cfg)
+
+	cmdList = append(cmdList, allCmd)
+	return cmdList
+}
+
+func addFlags(cmd *cobra.Command, cfg *renewConfig) {
+	options.AddConfigFlag(cmd.Flags(), &cfg.cfgPath)
+	options.AddCertificateDirFlag(cmd.Flags(), &cfg.cfg.CertificatesDir)
+	options.AddKubeConfigFlag(cmd.Flags(), &cfg.kubeconfigPath)
+	cmd.Flags().BoolVar(&cfg.useAPI, "use-api", cfg.useAPI, "Use the kubernetes certificate API to renew certificates")
+}
+
+// generateCertCommand takes mostly strings instead of structs to avoid using structs in a for loop
+func generateCertCommand(name, longName, baseName, caCertBaseName string, cfg *renewConfig) *cobra.Command {
+	return &cobra.Command{
+		Use:   name,
+		Short: fmt.Sprintf("Generates the %s", longName),
+		Long:  fmt.Sprintf(genericLongDesc, longName, baseName),
+		Run: func(cmd *cobra.Command, args []string) {
+			internalcfg, err := configutil.ConfigFileAndDefaultsToInternalConfig(cfg.cfgPath, &cfg.cfg)
+			kubeadmutil.CheckErr(err)
+			renewer, err := getRenewer(cfg, caCertBaseName)
+			kubeadmutil.CheckErr(err)
+
+			err = renewal.RenewExistingCert(internalcfg.CertificatesDir, baseName, renewer)
+			kubeadmutil.CheckErr(err)
+		},
+	}
+}
+
+func makeCommandForRenew(cert *certsphase.KubeadmCert, caCert *certsphase.KubeadmCert, cfg *renewConfig) *cobra.Command {
+	certCmd := generateCertCommand(cert.Name, cert.LongName, cert.BaseName, caCert.BaseName, cfg)
+	addFlags(certCmd, cfg)
+	return certCmd
+}
+
+func getRenewer(cfg *renewConfig, caCertBaseName string) (renewal.Interface, error) {
+	if cfg.useAPI {
+		kubeConfigPath := cmdutil.FindExistingKubeConfig(cfg.kubeconfigPath)
+		client, err := kubeconfigutil.ClientSetFromFile(kubeConfigPath)
+		if err != nil {
+			return nil, err
+		}
+		return renewal.NewCertsAPIRenawal(client), nil
+	}
+
+	caCert, caKey, err := certsphase.LoadCertificateAuthority(cfg.cfg.CertificatesDir, caCertBaseName)
+	if err != nil {
+		return nil, err
+	}
+
+	return renewal.NewFileRenewal(caCert, caKey), nil
+}

cmd/kubeadm/app/cmd/phases/certs/renewal_test.go

@@ -0,0 +1,222 @@
+/*
+Copyright 2018 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 renew
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"fmt"
+	"math/big"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/spf13/cobra"
+
+	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs/pkiutil"
+	testutil "k8s.io/kubernetes/cmd/kubeadm/test"
+	certstestutil "k8s.io/kubernetes/cmd/kubeadm/test/certs"
+	cmdtestutil "k8s.io/kubernetes/cmd/kubeadm/test/cmd"
+)
+
+func TestCommandsGenerated(t *testing.T) {
+	expectedFlags := []string{
+		"cert-dir",
+		"config",
+		"use-api",
+	}
+
+	expectedCommands := []string{
+		"renew all",
+
+		"renew apiserver",
+		"renew apiserver-kubelet-client",
+		"renew apiserver-etcd-client",
+
+		"renew front-proxy-client",
+
+		"renew etcd-server",
+		"renew etcd-peer",
+		"renew etcd-healthcheck-client",
+	}
+
+	renewCmd := NewCmdCertsRenewal()
+
+	fakeRoot := &cobra.Command{}
+	fakeRoot.AddCommand(renewCmd)
+
+	for _, cmdPath := range expectedCommands {
+		t.Run(cmdPath, func(t *testing.T) {
+			cmd, rem, _ := fakeRoot.Find(strings.Split(cmdPath, " "))
+			if cmd == nil || len(rem) != 0 {
+				t.Fatalf("couldn't locate command %q (%v)", cmdPath, rem)
+			}
+
+			for _, flag := range expectedFlags {
+				if cmd.Flags().Lookup(flag) == nil {
+					t.Errorf("couldn't find expected flag --%s", flag)
+				}
+			}
+		})
+	}
+}
+
+func TestRunRenewCommands(t *testing.T) {
+	tests := []struct {
+		command     string
+		baseNames   []string
+		caBaseNames []string
+	}{
+		{
+			command: "all",
+			baseNames: []string{
+				kubeadmconstants.APIServerCertAndKeyBaseName,
+				kubeadmconstants.APIServerKubeletClientCertAndKeyBaseName,
+				kubeadmconstants.APIServerEtcdClientCertAndKeyBaseName,
+				kubeadmconstants.FrontProxyClientCertAndKeyBaseName,
+				kubeadmconstants.EtcdServerCertAndKeyBaseName,
+				kubeadmconstants.EtcdPeerCertAndKeyBaseName,
+				kubeadmconstants.EtcdHealthcheckClientCertAndKeyBaseName,
+			},
+			caBaseNames: []string{
+				kubeadmconstants.CACertAndKeyBaseName,
+				kubeadmconstants.FrontProxyCACertAndKeyBaseName,
+				kubeadmconstants.EtcdCACertAndKeyBaseName,
+			},
+		},
+		{
+			command:     "apiserver",
+			baseNames:   []string{kubeadmconstants.APIServerCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.CACertAndKeyBaseName},
+		},
+		{
+			command:     "apiserver-kubelet-client",
+			baseNames:   []string{kubeadmconstants.APIServerKubeletClientCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.CACertAndKeyBaseName},
+		},
+		{
+			command:     "apiserver-etcd-client",
+			baseNames:   []string{kubeadmconstants.APIServerEtcdClientCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.EtcdCACertAndKeyBaseName},
+		},
+		{
+			command:     "front-proxy-client",
+			baseNames:   []string{kubeadmconstants.FrontProxyClientCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.FrontProxyCACertAndKeyBaseName},
+		},
+		{
+			command:     "etcd-server",
+			baseNames:   []string{kubeadmconstants.EtcdServerCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.EtcdCACertAndKeyBaseName},
+		},
+		{
+			command:     "etcd-peer",
+			baseNames:   []string{kubeadmconstants.EtcdPeerCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.EtcdCACertAndKeyBaseName},
+		},
+		{
+			command:     "etcd-healthcheck-client",
+			baseNames:   []string{kubeadmconstants.EtcdHealthcheckClientCertAndKeyBaseName},
+			caBaseNames: []string{kubeadmconstants.EtcdCACertAndKeyBaseName},
+		},
+	}
+
+	renewCmds := getRenewSubCommands()
+
+	for _, test := range tests {
+		t.Run(test.command, func(t *testing.T) {
+			tmpDir := testutil.SetupTempDir(t)
+			defer os.RemoveAll(tmpDir)
+
+			caCert, caKey := certstestutil.SetupCertificateAuthorithy(t)
+
+			for _, caBaseName := range test.caBaseNames {
+				if err := pkiutil.WriteCertAndKey(tmpDir, caBaseName, caCert, caKey); err != nil {
+					t.Fatalf("couldn't write out CA: %v", err)
+				}
+			}
+
+			certTmpl := x509.Certificate{
+				Subject: pkix.Name{
+					CommonName:   "test-cert",
+					Organization: []string{"sig-cluster-lifecycle"},
+				},
+				DNSNames:     []string{"test-domain.space"},
+				SerialNumber: new(big.Int).SetInt64(0),
+				NotBefore:    time.Now().Add(-time.Hour * 24 * 365),
+				NotAfter:     time.Now().Add(-time.Hour),
+				KeyUsage:     x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+				ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+			}
+
+			key, err := rsa.GenerateKey(rand.Reader, 2048)
+			if err != nil {
+				t.Fatalf("couldn't generate private key: %v", err)
+			}
+
+			certDERBytes, err := x509.CreateCertificate(rand.Reader, &certTmpl, caCert, key.Public(), caKey)
+			if err != nil {
+				t.Fatalf("couldn't generate private key: %v", err)
+			}
+			cert, err := x509.ParseCertificate(certDERBytes)
+			if err != nil {
+				t.Fatalf("couldn't generate private key: %v", err)
+			}
+
+			for _, baseName := range test.baseNames {
+				if err := pkiutil.WriteCertAndKey(tmpDir, baseName, cert, key); err != nil {
+					t.Fatalf("couldn't write out initial certificate")
+				}
+			}
+
+			cmdtestutil.RunSubCommand(t, renewCmds, test.command, fmt.Sprintf("--cert-dir=%s", tmpDir))
+
+			for _, baseName := range test.baseNames {
+				newCert, newKey, err := pkiutil.TryLoadCertAndKeyFromDisk(tmpDir, baseName)
+				if err != nil {
+					t.Fatalf("couldn't load renewed certificate: %v", err)
+				}
+
+				certstestutil.AssertCertificateIsSignedByCa(t, newCert, caCert)
+
+				pool := x509.NewCertPool()
+				pool.AddCert(caCert)
+
+				_, err = newCert.Verify(x509.VerifyOptions{
+					DNSName:   "test-domain.space",
+					Roots:     pool,
+					KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+				})
+				if err != nil {
+					t.Errorf("couldn't verify renewed cert: %v", err)
+				}
+
+				pubKey, ok := newCert.PublicKey.(*rsa.PublicKey)
+				if !ok {
+					t.Errorf("unknown public key type %T", newCert.PublicKey)
+				} else if pubKey.N.Cmp(newKey.N) != 0 {
+					t.Error("private key does not match public key")
+				}
+			}
+
+		})
+	}
+}

cmd/kubeadm/app/phases/certs/BUILD

@@ -52,6 +52,7 @@ filegroup(
     srcs = [
         ":package-srcs",
         "//cmd/kubeadm/app/phases/certs/pkiutil:all-srcs",
+        "//cmd/kubeadm/app/phases/certs/renewal:all-srcs",
     ],
     tags = ["automanaged"],
 )

cmd/kubeadm/app/phases/certs/certs.go

@@ -137,7 +137,7 @@ func CreateCertAndKeyFilesWithCA(certSpec *KubeadmCert, caCertSpec *KubeadmCert,
 		return fmt.Errorf("Expected CAname for %s to be %q, but was %s", certSpec.Name, certSpec.CAName, caCertSpec.Name)
 	}
 
-	caCert, caKey, err := loadCertificateAuthority(cfg.CertificatesDir, caCertSpec.BaseName)
+	caCert, caKey, err := LoadCertificateAuthority(cfg.CertificatesDir, caCertSpec.BaseName)
 	if err != nil {
 		return fmt.Errorf("Couldn't load CA certificate %s: %v", caCertSpec.Name, err)
 	}
@@ -158,7 +158,8 @@ func newCertAndKeyFromSpec(certSpec *KubeadmCert, cfg *kubeadmapi.InitConfigurat
 	return cert, key, err
 }
 
-func loadCertificateAuthority(pkiDir string, baseName string) (*x509.Certificate, *rsa.PrivateKey, error) {
+// LoadCertificateAuthority tries to load a CA in the given directory with the given name.
+func LoadCertificateAuthority(pkiDir string, baseName string) (*x509.Certificate, *rsa.PrivateKey, error) {
 	// Checks if certificate authority exists in the PKI directory
 	if !pkiutil.CertOrKeyExist(pkiDir, baseName) {
 		return nil, nil, fmt.Errorf("couldn't load %s certificate authority from %s", baseName, pkiDir)

cmd/kubeadm/app/phases/certs/pkiutil/pki_helpers.go

@@ -130,7 +130,7 @@ func WritePublicKey(pkiPath, name string, key *rsa.PublicKey) error {
 
 // CertOrKeyExist returns a boolean whether the cert or the key exists
 func CertOrKeyExist(pkiPath, name string) bool {
-	certificatePath, privateKeyPath := pathsForCertAndKey(pkiPath, name)
+	certificatePath, privateKeyPath := PathsForCertAndKey(pkiPath, name)
 
 	_, certErr := os.Stat(certificatePath)
 	_, keyErr := os.Stat(privateKeyPath)
@@ -234,7 +234,8 @@ func TryLoadPrivatePublicKeyFromDisk(pkiPath, name string) (*rsa.PrivateKey, *rs
 	return k, p, nil
 }
 
-func pathsForCertAndKey(pkiPath, name string) (string, string) {
+// PathsForCertAndKey returns the paths for the certificate and key given the path and basename.
+func PathsForCertAndKey(pkiPath, name string) (string, string) {
 	return pathForCert(pkiPath, name), pathForKey(pkiPath, name)
 }
 

cmd/kubeadm/app/phases/certs/pkiutil/pki_helpers_test.go

@@ -405,7 +405,7 @@ func TestTryLoadKeyFromDisk(t *testing.T) {
 }
 
 func TestPathsForCertAndKey(t *testing.T) {
-	crtPath, keyPath := pathsForCertAndKey("/foo", "bar")
+	crtPath, keyPath := PathsForCertAndKey("/foo", "bar")
 	if crtPath != "/foo/bar.crt" {
 		t.Errorf("unexpected certificate path: %s", crtPath)
 	}

cmd/kubeadm/app/phases/certs/renewal/BUILD

@@ -0,0 +1,60 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "certsapi.go",
+        "filerenewal.go",
+        "interface.go",
+        "renewal.go",
+    ],
+    importpath = "k8s.io/kubernetes/cmd/kubeadm/app/phases/certs/renewal",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//cmd/kubeadm/app/phases/certs/pkiutil:go_default_library",
+        "//staging/src/k8s.io/api/certificates/v1beta1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/fields:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/watch:go_default_library",
+        "//staging/src/k8s.io/client-go/kubernetes:go_default_library",
+        "//staging/src/k8s.io/client-go/kubernetes/typed/certificates/v1beta1:go_default_library",
+        "//staging/src/k8s.io/client-go/util/cert:go_default_library",
+        "//vendor/github.com/pkg/errors:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = [
+        "filerenewal_test.go",
+        "renewal_test.go",
+    ],
+    embed = [":go_default_library"],
+    deps = [
+        "//cmd/kubeadm/app/phases/certs:go_default_library",
+        "//cmd/kubeadm/app/phases/certs/pkiutil:go_default_library",
+        "//cmd/kubeadm/test:go_default_library",
+        "//cmd/kubeadm/test/certs:go_default_library",
+        "//staging/src/k8s.io/api/certificates/v1beta1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/watch:go_default_library",
+        "//staging/src/k8s.io/client-go/kubernetes/typed/certificates/v1beta1/fake:go_default_library",
+        "//staging/src/k8s.io/client-go/testing:go_default_library",
+        "//staging/src/k8s.io/client-go/util/cert:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

cmd/kubeadm/app/phases/certs/renewal/certsapi.go

@@ -0,0 +1,152 @@
+/*
+Copyright 2018 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 renewal
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"fmt"
+	"time"
+
+	"github.com/pkg/errors"
+
+	certsapi "k8s.io/api/certificates/v1beta1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/fields"
+	"k8s.io/apimachinery/pkg/watch"
+	"k8s.io/client-go/kubernetes"
+	certstype "k8s.io/client-go/kubernetes/typed/certificates/v1beta1"
+	certutil "k8s.io/client-go/util/cert"
+)
+
+const (
+	certAPIPrefixName = "kubeadm-cert"
+)
+
+var (
+	watchTimeout = 5 * time.Minute
+)
+
+// CertsAPIRenewal creates new certificates using the certs API
+type CertsAPIRenewal struct {
+	client certstype.CertificatesV1beta1Interface
+}
+
+// NewCertsAPIRenawal takes a Kubernetes interface and returns a renewal Interface.
+func NewCertsAPIRenawal(client kubernetes.Interface) Interface {
+	return &CertsAPIRenewal{
+		client: client.CertificatesV1beta1(),
+	}
+}
+
+// Renew takes a certificate using the cert and key.
+func (r *CertsAPIRenewal) Renew(cfg *certutil.Config) (*x509.Certificate, *rsa.PrivateKey, error) {
+	reqTmp := &x509.CertificateRequest{
+		Subject: pkix.Name{
+			CommonName:   cfg.CommonName,
+			Organization: cfg.Organization,
+		},
+		DNSNames:    cfg.AltNames.DNSNames,
+		IPAddresses: cfg.AltNames.IPs,
+	}
+
+	key, err := certutil.NewPrivateKey()
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "couldn't create new private key")
+	}
+
+	csr, err := x509.CreateCertificateRequest(rand.Reader, reqTmp, key)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "couldn't create certificate signing request")
+	}
+
+	usages := make([]certsapi.KeyUsage, len(cfg.Usages))
+	for i, usage := range cfg.Usages {
+		certsAPIUsage, ok := usageMap[usage]
+		if !ok {
+			return nil, nil, fmt.Errorf("unknown key usage: %v", usage)
+		}
+		usages[i] = certsAPIUsage
+	}
+
+	k8sCSR := &certsapi.CertificateSigningRequest{
+		ObjectMeta: metav1.ObjectMeta{
+			GenerateName: certAPIPrefixName,
+		},
+		Spec: certsapi.CertificateSigningRequestSpec{
+			Request: csr,
+			Usages:  usages,
+		},
+	}
+
+	req, err := r.client.CertificateSigningRequests().Create(k8sCSR)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "couldn't create certificate signing request")
+	}
+
+	watcher, err := r.client.CertificateSigningRequests().Watch(metav1.ListOptions{
+		Watch:         true,
+		FieldSelector: fields.Set{"metadata.name": req.Name}.String(),
+	})
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "couldn't watch for certificate creation")
+	}
+	defer watcher.Stop()
+
+	select {
+	case ev := <-watcher.ResultChan():
+		if ev.Type != watch.Modified {
+			return nil, nil, fmt.Errorf("unexpected event received: %q", ev.Type)
+		}
+	case <-time.After(watchTimeout):
+		return nil, nil, errors.New("timeout trying to sign certificate")
+	}
+
+	req, err = r.client.CertificateSigningRequests().Get(req.Name, metav1.GetOptions{})
+	if len(req.Status.Conditions) < 1 {
+		return nil, nil, errors.New("certificate signing request has no statuses")
+	}
+
+	// TODO: under what circumstances are there more than one?
+	if status := req.Status.Conditions[0].Type; status != certsapi.CertificateApproved {
+		return nil, nil, fmt.Errorf("unexpected certificate status: %v", status)
+	}
+
+	cert, err := x509.ParseCertificate(req.Status.Certificate)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "couldn't parse issued certificate")
+	}
+
+	return cert, key, nil
+}
+
+var usageMap = map[x509.ExtKeyUsage]certsapi.KeyUsage{
+	x509.ExtKeyUsageAny:                        certsapi.UsageAny,
+	x509.ExtKeyUsageServerAuth:                 certsapi.UsageServerAuth,
+	x509.ExtKeyUsageClientAuth:                 certsapi.UsageClientAuth,
+	x509.ExtKeyUsageCodeSigning:                certsapi.UsageCodeSigning,
+	x509.ExtKeyUsageEmailProtection:            certsapi.UsageEmailProtection,
+	x509.ExtKeyUsageIPSECEndSystem:             certsapi.UsageIPsecEndSystem,
+	x509.ExtKeyUsageIPSECTunnel:                certsapi.UsageIPsecTunnel,
+	x509.ExtKeyUsageIPSECUser:                  certsapi.UsageIPsecUser,
+	x509.ExtKeyUsageTimeStamping:               certsapi.UsageTimestamping,
+	x509.ExtKeyUsageOCSPSigning:                certsapi.UsageOCSPSigning,
+	x509.ExtKeyUsageMicrosoftServerGatedCrypto: certsapi.UsageMicrosoftSGC,
+	x509.ExtKeyUsageNetscapeServerGatedCrypto:  certsapi.UsageNetscapSGC,
+}

cmd/kubeadm/app/phases/certs/renewal/filerenewal.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2018 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 renewal
+
+import (
+	"crypto/rsa"
+	"crypto/x509"
+
+	certutil "k8s.io/client-go/util/cert"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs/pkiutil"
+)
+
+// FileRenewal renews a certificate using local certs
+type FileRenewal struct {
+	caCert *x509.Certificate
+	caKey  *rsa.PrivateKey
+}
+
+// NewFileRenewal takes a certificate pair to construct the Interface.
+func NewFileRenewal(caCert *x509.Certificate, caKey *rsa.PrivateKey) Interface {
+	return &FileRenewal{
+		caCert: caCert,
+		caKey:  caKey,
+	}
+}
+
+// Renew takes a certificate using the cert and key
+func (r *FileRenewal) Renew(cfg *certutil.Config) (*x509.Certificate, *rsa.PrivateKey, error) {
+	return pkiutil.NewCertAndKey(r.caCert, r.caKey, cfg)
+}

cmd/kubeadm/app/phases/certs/renewal/filerenewal_test.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2018 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 renewal
+
+import (
+	"crypto/x509"
+	"testing"
+
+	certutil "k8s.io/client-go/util/cert"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
+)
+
+func TestFileRenew(t *testing.T) {
+	caCertCfg := &certutil.Config{CommonName: "kubernetes"}
+	caCert, caKey, err := certs.NewCACertAndKey(caCertCfg)
+	if err != nil {
+		t.Fatalf("couldn't create CA: %v", err)
+	}
+
+	fr := NewFileRenewal(caCert, caKey)
+
+	certCfg := &certutil.Config{
+		CommonName: "test-certs",
+		AltNames: certutil.AltNames{
+			DNSNames: []string{"test-domain.space"},
+		},
+		Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+	}
+
+	cert, _, err := fr.Renew(certCfg)
+	if err != nil {
+		t.Fatalf("unexpected error renewing cert: %v", err)
+	}
+
+	pool := x509.NewCertPool()
+	pool.AddCert(caCert)
+
+	_, err = cert.Verify(x509.VerifyOptions{
+		DNSName:   "test-domain.space",
+		Roots:     pool,
+		KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+	})
+	if err != nil {
+		t.Errorf("couldn't verify new cert: %v", err)
+	}
+
+}

cmd/kubeadm/app/phases/certs/renewal/interface.go

@@ -0,0 +1,29 @@
+/*
+Copyright 2018 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 renewal
+
+import (
+	"crypto/rsa"
+	"crypto/x509"
+
+	certutil "k8s.io/client-go/util/cert"
+)
+
+// Interface represents a standard way to renew a certificate.
+type Interface interface {
+	Renew(*certutil.Config) (*x509.Certificate, *rsa.PrivateKey, error)
+}

cmd/kubeadm/app/phases/certs/renewal/renewal.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2018 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 renewal
+
+import (
+	"crypto/x509"
+	"fmt"
+
+	"github.com/pkg/errors"
+	certutil "k8s.io/client-go/util/cert"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs/pkiutil"
+)
+
+// RenewExistingCert loads a certificate file, uses the renew interface to renew it,
+// and saves the resulting certificate and key over the old one.
+func RenewExistingCert(certsDir, baseName string, impl Interface) error {
+	certificatePath, _ := pkiutil.PathsForCertAndKey(certsDir, baseName)
+	certs, err := certutil.CertsFromFile(certificatePath)
+	if err != nil {
+		return fmt.Errorf("failed to load existing certificate %s: %v", baseName, err)
+	}
+
+	if len(certs) != 1 {
+		return fmt.Errorf("wanted exactly one certificate, got %d", len(certs))
+	}
+
+	cfg := certToConfig(certs[0])
+	newCert, newKey, err := impl.Renew(cfg)
+	if err != nil {
+		return errors.Wrapf(err, "failed to renew certificate %s", baseName)
+	}
+
+	if err := pkiutil.WriteCertAndKey(certsDir, baseName, newCert, newKey); err != nil {
+		return errors.Wrapf(err, "failed to write new certificate %s", baseName)
+	}
+	return nil
+}
+
+func certToConfig(cert *x509.Certificate) *certutil.Config {
+	return &certutil.Config{
+		CommonName:   cert.Subject.CommonName,
+		Organization: cert.Subject.Organization,
+		AltNames: certutil.AltNames{
+			IPs:      cert.IPAddresses,
+			DNSNames: cert.DNSNames,
+		},
+		Usages: cert.ExtKeyUsage,
+	}
+}

cmd/kubeadm/app/phases/certs/renewal/renewal_test.go

@@ -0,0 +1,235 @@
+/*
+Copyright 2018 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 renewal
+
+import (
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"net"
+	"os"
+	"testing"
+	"time"
+
+	certsapi "k8s.io/api/certificates/v1beta1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/watch"
+	fakecerts "k8s.io/client-go/kubernetes/typed/certificates/v1beta1/fake"
+	k8stesting "k8s.io/client-go/testing"
+	certutil "k8s.io/client-go/util/cert"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs"
+	"k8s.io/kubernetes/cmd/kubeadm/app/phases/certs/pkiutil"
+	testutil "k8s.io/kubernetes/cmd/kubeadm/test"
+	certtestutil "k8s.io/kubernetes/cmd/kubeadm/test/certs"
+)
+
+func TestRenewImplementations(t *testing.T) {
+	caCertCfg := &certutil.Config{CommonName: "kubernetes"}
+	caCert, caKey, err := certs.NewCACertAndKey(caCertCfg)
+	if err != nil {
+		t.Fatalf("couldn't create CA: %v", err)
+	}
+
+	client := &fakecerts.FakeCertificatesV1beta1{
+		Fake: &k8stesting.Fake{},
+	}
+	certReq := getCertReq(t, caCert, caKey)
+	client.AddReactor("get", "certificatesigningrequests", defaultReactionFunc(certReq))
+	watcher := watch.NewFakeWithChanSize(1, false)
+	watcher.Modify(certReq)
+	client.AddWatchReactor("certificatesigningrequests", k8stesting.DefaultWatchReactor(watcher, nil))
+
+	// override the timeout so tests are faster
+	watchTimeout = time.Second
+
+	tests := []struct {
+		name string
+		impl Interface
+	}{
+		{
+			name: "filerenewal",
+			impl: NewFileRenewal(caCert, caKey),
+		},
+		{
+			name: "certs api",
+			impl: &CertsAPIRenewal{
+				client: client,
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+
+			certCfg := &certutil.Config{
+				CommonName: "test-certs",
+				AltNames: certutil.AltNames{
+					DNSNames: []string{"test-domain.space"},
+				},
+				Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+			}
+
+			cert, _, err := test.impl.Renew(certCfg)
+			if err != nil {
+				t.Fatalf("unexpected error renewing cert: %v", err)
+			}
+
+			pool := x509.NewCertPool()
+			pool.AddCert(caCert)
+
+			_, err = cert.Verify(x509.VerifyOptions{
+				DNSName:   "test-domain.space",
+				Roots:     pool,
+				KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+			})
+			if err != nil {
+				t.Errorf("couldn't verify new cert: %v", err)
+			}
+		})
+	}
+}
+
+func defaultReactionFunc(obj runtime.Object) k8stesting.ReactionFunc {
+	return func(act k8stesting.Action) (bool, runtime.Object, error) {
+		return true, obj, nil
+	}
+}
+
+func getCertReq(t *testing.T, caCert *x509.Certificate, caKey *rsa.PrivateKey) *certsapi.CertificateSigningRequest {
+	cert, _, err := pkiutil.NewCertAndKey(caCert, caKey, &certutil.Config{
+		CommonName: "testcert",
+		AltNames: certutil.AltNames{
+			DNSNames: []string{"test-domain.space"},
+		},
+		Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+	})
+	if err != nil {
+		t.Fatalf("couldn't generate cert: %v", err)
+	}
+
+	return &certsapi.CertificateSigningRequest{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "testcert",
+		},
+		Status: certsapi.CertificateSigningRequestStatus{
+			Conditions: []certsapi.CertificateSigningRequestCondition{
+				{
+					Type: certsapi.CertificateApproved,
+				},
+			},
+			Certificate: cert.Raw,
+		},
+	}
+}
+
+func TestCertToConfig(t *testing.T) {
+	expectedConfig := &certutil.Config{
+		CommonName:   "test-common-name",
+		Organization: []string{"sig-cluster-lifecycle"},
+		AltNames: certutil.AltNames{
+			IPs:      []net.IP{net.ParseIP("10.100.0.1")},
+			DNSNames: []string{"test-domain.space"},
+		},
+		Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+	}
+
+	cert := &x509.Certificate{
+		Subject: pkix.Name{
+			CommonName:   "test-common-name",
+			Organization: []string{"sig-cluster-lifecycle"},
+		},
+		ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+		DNSNames:    []string{"test-domain.space"},
+		IPAddresses: []net.IP{net.ParseIP("10.100.0.1")},
+	}
+
+	cfg := certToConfig(cert)
+
+	if cfg.CommonName != expectedConfig.CommonName {
+		t.Errorf("expected common name %q, got %q", expectedConfig.CommonName, cfg.CommonName)
+	}
+
+	if len(cfg.Organization) != 1 || cfg.Organization[0] != expectedConfig.Organization[0] {
+		t.Errorf("expected organization %v, got %v", expectedConfig.Organization, cfg.Organization)
+
+	}
+
+	if len(cfg.Usages) != 1 || cfg.Usages[0] != expectedConfig.Usages[0] {
+		t.Errorf("expected ext key usage %v, got %v", expectedConfig.Usages, cfg.Usages)
+	}
+
+	if len(cfg.AltNames.IPs) != 1 || cfg.AltNames.IPs[0].String() != expectedConfig.AltNames.IPs[0].String() {
+		t.Errorf("expected SAN IPs %v, got %v", expectedConfig.AltNames.IPs, cfg.AltNames.IPs)
+	}
+
+	if len(cfg.AltNames.DNSNames) != 1 || cfg.AltNames.DNSNames[0] != expectedConfig.AltNames.DNSNames[0] {
+		t.Errorf("expected SAN DNSNames %v, got %v", expectedConfig.AltNames.DNSNames, cfg.AltNames.DNSNames)
+	}
+}
+
+func TestRenewExistingCert(t *testing.T) {
+	cfg := &certutil.Config{
+		CommonName:   "test-common-name",
+		Organization: []string{"sig-cluster-lifecycle"},
+		AltNames: certutil.AltNames{
+			IPs:      []net.IP{net.ParseIP("10.100.0.1")},
+			DNSNames: []string{"test-domain.space"},
+		},
+		Usages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth},
+	}
+
+	caCertCfg := &certutil.Config{CommonName: "kubernetes"}
+	caCert, caKey, err := certs.NewCACertAndKey(caCertCfg)
+	if err != nil {
+		t.Fatalf("couldn't create CA: %v", err)
+	}
+
+	cert, key, err := pkiutil.NewCertAndKey(caCert, caKey, cfg)
+	if err != nil {
+		t.Fatalf("couldn't generate certificate: %v", err)
+	}
+
+	dir := testutil.SetupTempDir(t)
+	defer os.RemoveAll(dir)
+
+	if err := pkiutil.WriteCertAndKey(dir, "server", cert, key); err != nil {
+		t.Fatalf("couldn't write out certificate")
+	}
+
+	renewer := NewFileRenewal(caCert, caKey)
+
+	if err := RenewExistingCert(dir, "server", renewer); err != nil {
+		t.Fatalf("couldn't renew certificate: %v", err)
+	}
+
+	newCert, err := pkiutil.TryLoadCertFromDisk(dir, "server")
+	if err != nil {
+		t.Fatalf("couldn't load created certificate: %v", err)
+	}
+
+	if newCert.SerialNumber.Cmp(cert.SerialNumber) == 0 {
+		t.Fatal("expected new certificate, but renewed certificate has same serial number")
+	}
+
+	certtestutil.AssertCertificateIsSignedByCa(t, newCert, caCert)
+	certtestutil.AssertCertificateHasClientAuthUsage(t, newCert)
+	certtestutil.AssertCertificateHasOrganizations(t, newCert, cfg.Organization...)
+	certtestutil.AssertCertificateHasCommonName(t, newCert, cfg.CommonName)
+	certtestutil.AssertCertificateHasDNSNames(t, newCert, cfg.AltNames.DNSNames...)
+	certtestutil.AssertCertificateHasIPAddresses(t, newCert, cfg.AltNames.IPs...)
+}

staging/src/k8s.io/client-go/util/cert/cert.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"crypto/ecdsa"
 	"crypto/elliptic"
+	"crypto/rand"
 	cryptorand "crypto/rand"
 	"crypto/rsa"
 	"crypto/x509"
@@ -87,7 +88,7 @@ func NewSelfSignedCACert(cfg Config, key *rsa.PrivateKey) (*x509.Certificate, er
 
 // NewSignedCert creates a signed certificate using the given CA certificate and key
 func NewSignedCert(cfg Config, key *rsa.PrivateKey, caCert *x509.Certificate, caKey *rsa.PrivateKey) (*x509.Certificate, error) {
-	serial, err := cryptorand.Int(cryptorand.Reader, new(big.Int).SetInt64(math.MaxInt64))
+	serial, err := rand.Int(rand.Reader, new(big.Int).SetInt64(math.MaxInt64))
 	if err != nil {
 		return nil, err
 	}