Support TLS Server Name overrides in kubeconfig file

Signed-off-by: Suresh Kumar Ponnusamy <[email protected]>

Author: surki

staging/src/k8s.io/cli-runtime/pkg/genericclioptions/config_flags.go

@@ -41,6 +41,7 @@ const (
 	flagContext          = "context"
 	flagNamespace        = "namespace"
 	flagAPIServer        = "server"
+	flagTLSServerName    = "tls-server-name"
 	flagInsecure         = "insecure-skip-tls-verify"
 	flagCertFile         = "client-certificate"
 	flagKeyFile          = "client-key"
@@ -84,6 +85,7 @@ type ConfigFlags struct {
 	Context          *string
 	Namespace        *string
 	APIServer        *string
+	TLSServerName    *string
 	Insecure         *bool
 	CertFile         *string
 	KeyFile          *string
@@ -160,6 +162,9 @@ func (f *ConfigFlags) toRawKubeConfigLoader() clientcmd.ClientConfig {
 	if f.APIServer != nil {
 		overrides.ClusterInfo.Server = *f.APIServer
 	}
+	if f.TLSServerName != nil {
+		overrides.ClusterInfo.TLSServerName = *f.TLSServerName
+	}
 	if f.CAFile != nil {
 		overrides.ClusterInfo.CertificateAuthority = *f.CAFile
 	}
@@ -294,6 +299,9 @@ func (f *ConfigFlags) AddFlags(flags *pflag.FlagSet) {
 	if f.APIServer != nil {
 		flags.StringVarP(f.APIServer, flagAPIServer, "s", *f.APIServer, "The address and port of the Kubernetes API server")
 	}
+	if f.TLSServerName != nil {
+		flags.StringVar(f.TLSServerName, flagTLSServerName, *f.TLSServerName, "Server name to use for server certificate validation. If it is not provided, the hostname used to contact the server is used")
+	}
 	if f.Insecure != nil {
 		flags.BoolVar(f.Insecure, flagInsecure, *f.Insecure, "If true, the server's certificate will not be checked for validity. This will make your HTTPS connections insecure")
 	}
@@ -329,6 +337,7 @@ func NewConfigFlags(usePersistentConfig bool) *ConfigFlags {
 		Context:          stringptr(""),
 		Namespace:        stringptr(""),
 		APIServer:        stringptr(""),
+		TLSServerName:    stringptr(""),
 		CertFile:         stringptr(""),
 		KeyFile:          stringptr(""),
 		CAFile:           stringptr(""),

staging/src/k8s.io/client-go/tools/clientcmd/api/types.go

@@ -70,6 +70,9 @@ type Cluster struct {
 	LocationOfOrigin string
 	// Server is the address of the kubernetes cluster (https://hostname:port).
 	Server string `json:"server"`
+	// TLSServerName is used to check server certificate. If TLSServerName is empty, the hostname used to contact the server is used.
+	// +optional
+	TLSServerName string `json:"tls-server-name,omitempty"`
 	// InsecureSkipTLSVerify skips the validity check for the server's certificate. This will make your HTTPS connections insecure.
 	// +optional
 	InsecureSkipTLSVerify bool `json:"insecure-skip-tls-verify,omitempty"`

staging/src/k8s.io/client-go/tools/clientcmd/api/v1/types.go

@@ -63,6 +63,9 @@ type Preferences struct {
 type Cluster struct {
 	// Server is the address of the kubernetes cluster (https://hostname:port).
 	Server string `json:"server"`
+	// TLSServerName is used to check server certificate. If TLSServerName is empty, the hostname used to contact the server is used.
+	// +optional
+	TLSServerName string `json:"tls-server-name,omitempty"`
 	// InsecureSkipTLSVerify skips the validity check for the server's certificate. This will make your HTTPS connections insecure.
 	// +optional
 	InsecureSkipTLSVerify bool `json:"insecure-skip-tls-verify,omitempty"`

staging/src/k8s.io/client-go/tools/clientcmd/client_config.go

@@ -210,6 +210,7 @@ func getServerIdentificationPartialConfig(configAuthInfo clientcmdapi.AuthInfo,
 	configClientConfig.CAFile = configClusterInfo.CertificateAuthority
 	configClientConfig.CAData = configClusterInfo.CertificateAuthorityData
 	configClientConfig.Insecure = configClusterInfo.InsecureSkipTLSVerify
+	configClientConfig.ServerName = configClusterInfo.TLSServerName
 	mergo.MergeWithOverwrite(mergedConfig, configClientConfig)
 
 	return mergedConfig, nil
@@ -460,6 +461,10 @@ func (config *DirectClientConfig) getCluster() (clientcmdapi.Cluster, error) {
 		mergedClusterInfo.CertificateAuthorityData = config.overrides.ClusterInfo.CertificateAuthorityData
 	}
 
+	if config.overrides.ClusterInfo.TLSServerName != "" {
+		mergedClusterInfo.TLSServerName = config.overrides.ClusterInfo.TLSServerName
+	}
+
 	return *mergedClusterInfo, nil
 }
 

staging/src/k8s.io/client-go/tools/clientcmd/client_config_test.go

@@ -180,6 +180,25 @@ func TestCAOverridesCAData(t *testing.T) {
 	matchByteArg(nil, actualCfg.TLSClientConfig.CAData, t)
 }
 
+func TestTLSServerName(t *testing.T) {
+	config := createValidTestConfig()
+
+	clientBuilder := NewNonInteractiveClientConfig(*config, "clean", &ConfigOverrides{
+		ClusterInfo: clientcmdapi.Cluster{
+			TLSServerName: "overridden-server-name",
+		},
+	}, nil)
+
+	actualCfg, err := clientBuilder.ClientConfig()
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	matchStringArg("overridden-server-name", actualCfg.ServerName, t)
+	matchStringArg("", actualCfg.TLSClientConfig.CAFile, t)
+	matchByteArg(nil, actualCfg.TLSClientConfig.CAData, t)
+}
+
 func TestMergeContext(t *testing.T) {
 	const namespace = "overridden-namespace"
 
@@ -411,6 +430,7 @@ func TestCreateClean(t *testing.T) {
 	matchStringArg("", clientConfig.APIPath, t)
 	matchBoolArg(config.Clusters["clean"].InsecureSkipTLSVerify, clientConfig.Insecure, t)
 	matchStringArg(config.AuthInfos["clean"].Token, clientConfig.BearerToken, t)
+	matchStringArg(config.Clusters["clean"].TLSServerName, clientConfig.ServerName, t)
 }
 
 func TestCreateCleanWithPrefix(t *testing.T) {
@@ -461,6 +481,7 @@ func TestCreateCleanDefault(t *testing.T) {
 	}
 
 	matchStringArg(config.Clusters["clean"].Server, clientConfig.Host, t)
+	matchStringArg(config.Clusters["clean"].TLSServerName, clientConfig.ServerName, t)
 	matchBoolArg(config.Clusters["clean"].InsecureSkipTLSVerify, clientConfig.Insecure, t)
 	matchStringArg(config.AuthInfos["clean"].Token, clientConfig.BearerToken, t)
 }
@@ -477,6 +498,7 @@ func TestCreateCleanDefaultCluster(t *testing.T) {
 	}
 
 	matchStringArg(config.Clusters["clean"].Server, clientConfig.Host, t)
+	matchStringArg(config.Clusters["clean"].TLSServerName, clientConfig.ServerName, t)
 	matchBoolArg(config.Clusters["clean"].InsecureSkipTLSVerify, clientConfig.Insecure, t)
 	matchStringArg(config.AuthInfos["clean"].Token, clientConfig.BearerToken, t)
 }

staging/src/k8s.io/client-go/tools/clientcmd/overrides.go

@@ -71,6 +71,7 @@ type ClusterOverrideFlags struct {
 	APIVersion            FlagInfo
 	CertificateAuthority  FlagInfo
 	InsecureSkipTLSVerify FlagInfo
+	TLSServerName         FlagInfo
 }
 
 // FlagInfo contains information about how to register a flag.  This struct is useful if you want to provide a way for an extender to
@@ -145,6 +146,7 @@ const (
 	FlagContext          = "context"
 	FlagNamespace        = "namespace"
 	FlagAPIServer        = "server"
+	FlagTLSServerName    = "tls-server-name"
 	FlagInsecure         = "insecure-skip-tls-verify"
 	FlagCertFile         = "client-certificate"
 	FlagKeyFile          = "client-key"
@@ -189,6 +191,7 @@ func RecommendedClusterOverrideFlags(prefix string) ClusterOverrideFlags {
 		APIServer:             FlagInfo{prefix + FlagAPIServer, "", "", "The address and port of the Kubernetes API server"},
 		CertificateAuthority:  FlagInfo{prefix + FlagCAFile, "", "", "Path to a cert file for the certificate authority"},
 		InsecureSkipTLSVerify: FlagInfo{prefix + FlagInsecure, "", "false", "If true, the server's certificate will not be checked for validity. This will make your HTTPS connections insecure"},
+		TLSServerName:         FlagInfo{prefix + FlagTLSServerName, "", "", "If provided, this name will be used to validate server certificate. If this is not provided, hostname used to contact the server is used."},
 	}
 }
 
@@ -226,6 +229,7 @@ func BindClusterFlags(clusterInfo *clientcmdapi.Cluster, flags *pflag.FlagSet, f
 	flagNames.APIServer.BindStringFlag(flags, &clusterInfo.Server)
 	flagNames.CertificateAuthority.BindStringFlag(flags, &clusterInfo.CertificateAuthority)
 	flagNames.InsecureSkipTLSVerify.BindBoolFlag(flags, &clusterInfo.InsecureSkipTLSVerify)
+	flagNames.TLSServerName.BindStringFlag(flags, &clusterInfo.TLSServerName)
 }
 
 // BindFlags is a convenience method to bind the specified flags to their associated variables

staging/src/k8s.io/kubectl/pkg/cmd/config/create_cluster.go

@@ -24,7 +24,6 @@ import (
 	"path/filepath"
 
 	"github.com/spf13/cobra"
-
 	"k8s.io/client-go/tools/clientcmd"
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
 	cliflag "k8s.io/component-base/cli/flag"
@@ -37,6 +36,7 @@ type createClusterOptions struct {
 	configAccess          clientcmd.ConfigAccess
 	name                  string
 	server                cliflag.StringFlag
+	tlsServerName         cliflag.StringFlag
 	insecureSkipTLSVerify cliflag.Tristate
 	certificateAuthority  cliflag.StringFlag
 	embedCAData           cliflag.Tristate
@@ -56,15 +56,18 @@ var (
 		kubectl config set-cluster e2e --certificate-authority=~/.kube/e2e/kubernetes.ca.crt
 
 		# Disable cert checking for the dev cluster entry
-		kubectl config set-cluster e2e --insecure-skip-tls-verify=true`)
+		kubectl config set-cluster e2e --insecure-skip-tls-verify=true
+
+		# Set custom TLS server name to use for validation for the e2e cluster entry
+		kubectl config set-cluster e2e --tls-server-name=my-cluster-name`)
 )
 
 // NewCmdConfigSetCluster returns a Command instance for 'config set-cluster' sub command
 func NewCmdConfigSetCluster(out io.Writer, configAccess clientcmd.ConfigAccess) *cobra.Command {
 	options := &createClusterOptions{configAccess: configAccess}
 
 	cmd := &cobra.Command{
-		Use:                   fmt.Sprintf("set-cluster NAME [--%v=server] [--%v=path/to/certificate/authority] [--%v=true]", clientcmd.FlagAPIServer, clientcmd.FlagCAFile, clientcmd.FlagInsecure),
+		Use:                   fmt.Sprintf("set-cluster NAME [--%v=server] [--%v=path/to/certificate/authority] [--%v=true] [--%v=example.com]", clientcmd.FlagAPIServer, clientcmd.FlagCAFile, clientcmd.FlagInsecure, clientcmd.FlagTLSServerName),
 		DisableFlagsInUseLine: true,
 		Short:                 i18n.T("Sets a cluster entry in kubeconfig"),
 		Long:                  createClusterLong,
@@ -79,6 +82,7 @@ func NewCmdConfigSetCluster(out io.Writer, configAccess clientcmd.ConfigAccess)
 	options.insecureSkipTLSVerify.Default(false)
 
 	cmd.Flags().Var(&options.server, clientcmd.FlagAPIServer, clientcmd.FlagAPIServer+" for the cluster entry in kubeconfig")
+	cmd.Flags().Var(&options.tlsServerName, clientcmd.FlagTLSServerName, clientcmd.FlagTLSServerName+" for the cluster entry in kubeconfig")
 	f := cmd.Flags().VarPF(&options.insecureSkipTLSVerify, clientcmd.FlagInsecure, "", clientcmd.FlagInsecure+" for the cluster entry in kubeconfig")
 	f.NoOptDefVal = "true"
 	cmd.Flags().Var(&options.certificateAuthority, clientcmd.FlagCAFile, "Path to "+clientcmd.FlagCAFile+" file for the cluster entry in kubeconfig")
@@ -121,6 +125,9 @@ func (o *createClusterOptions) modifyCluster(existingCluster clientcmdapi.Cluste
 	if o.server.Provided() {
 		modifiedCluster.Server = o.server.Value()
 	}
+	if o.tlsServerName.Provided() {
+		modifiedCluster.TLSServerName = o.tlsServerName.Value()
+	}
 	if o.insecureSkipTLSVerify.Provided() {
 		modifiedCluster.InsecureSkipTLSVerify = o.insecureSkipTLSVerify.Value()
 		// Specifying insecure mode clears any certificate authority

staging/src/k8s.io/kubectl/pkg/cmd/config/create_cluster_test.go

@@ -43,11 +43,12 @@ func TestCreateCluster(t *testing.T) {
 		args:        []string{"my-cluster"},
 		flags: []string{
 			"--server=http://192.168.0.1",
+			"--tls-server-name=my-cluster-name",
 		},
 		expected: `Cluster "my-cluster" set.` + "\n",
 		expectedConfig: clientcmdapi.Config{
 			Clusters: map[string]*clientcmdapi.Cluster{
-				"my-cluster": {Server: "http://192.168.0.1"},
+				"my-cluster": {Server: "http://192.168.0.1", TLSServerName: "my-cluster-name"},
 			},
 		},
 	}
@@ -115,5 +116,8 @@ func (test createClusterTest) run(t *testing.T) {
 		if cluster.Server != test.expectedConfig.Clusters[test.args[0]].Server {
 			t.Errorf("Fail in %q\n expected cluster server %v\n but got %v\n ", test.description, test.expectedConfig.Clusters[test.args[0]].Server, cluster.Server)
 		}
+		if cluster.TLSServerName != test.expectedConfig.Clusters[test.args[0]].TLSServerName {
+			t.Errorf("Fail in %q\n expected cluster TLS server name %v\n but got %v\n ", test.description, test.expectedConfig.Clusters[test.args[0]].TLSServerName, cluster.TLSServerName)
+		}
 	}
 }