Support TLS Server Name overrides in kubeconfig file

Signed-off-by: Suresh Kumar Ponnusamy <suresh.ponnusamy@freshworks.com>

Kubernetes-commit: 37c81ed79ac6836bce4b96f888aa407dc18d747c

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"`

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"`

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
 }
 

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)
 }

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