Do not wrap Kubernetes Address in brackets (#4363)

Signed-off-by: maksim.nabokikh <max.nabokih@gmail.com>

storage/kubernetes/client.go

@@ -32,6 +32,17 @@ import (
 	"github.com/dexidp/dex/storage/kubernetes/k8sapi"
 )
 
+const (
+	serviceAccountPath          = "/var/run/secrets/kubernetes.io/serviceaccount/"
+	serviceAccountTokenPath     = serviceAccountPath + "token"
+	serviceAccountCAPath        = serviceAccountPath + "ca.crt"
+	serviceAccountNamespacePath = serviceAccountPath + "namespace"
+
+	kubernetesServiceHostENV  = "KUBERNETES_SERVICE_HOST"
+	kubernetesServicePortENV  = "KUBERNETES_SERVICE_PORT"
+	kubernetesPodNamespaceENV = "KUBERNETES_POD_NAMESPACE"
+)
+
 type client struct {
 	client    *http.Client
 	baseURL   string
@@ -508,33 +519,35 @@ func getInClusterConfigNamespace(token, namespaceENV, namespacePath string) (str
 	return "", fmt.Errorf("%v: trying to get namespace from file: %v", err, fileErr)
 }
 
-func inClusterConfig() (k8sapi.Cluster, k8sapi.AuthInfo, string, error) {
-	const (
-		serviceAccountPath          = "/var/run/secrets/kubernetes.io/serviceaccount/"
-		serviceAccountTokenPath     = serviceAccountPath + "token"
-		serviceAccountCAPath        = serviceAccountPath + "ca.crt"
-		serviceAccountNamespacePath = serviceAccountPath + "namespace"
-
-		kubernetesServiceHostENV  = "KUBERNETES_SERVICE_HOST"
-		kubernetesServicePortENV  = "KUBERNETES_SERVICE_PORT"
-		kubernetesPodNamespaceENV = "KUBERNETES_POD_NAMESPACE"
-	)
-
-	host, port := os.Getenv(kubernetesServiceHostENV), os.Getenv(kubernetesServicePortENV)
+func getInClusterConnectOptions(host, port string) (k8sapi.Cluster, error) {
 	if len(host) == 0 || len(port) == 0 {
-		return k8sapi.Cluster{}, k8sapi.AuthInfo{}, "", fmt.Errorf(
+		return k8sapi.Cluster{}, fmt.Errorf(
 			"unable to load in-cluster configuration, %s and %s must be defined",
 			kubernetesServiceHostENV,
 			kubernetesServicePortENV,
 		)
 	}
+
 	// we need to wrap IPv6 addresses in square brackets
-	// IPv4 also works with square brackets
-	host = "[" + host + "]"
+	// IPv4 used to work with square brackets, but it was fixed in the latest Go versions
+	// https://github.com/golang/go/issues/75712
+	ipAddr := net.ParseIP(host)
+	if ipAddr != nil && ipAddr.To4() == nil {
+		host = "[" + host + "]"
+	}
+
 	cluster := k8sapi.Cluster{
 		Server:               "https://" + host + ":" + port,
 		CertificateAuthority: serviceAccountCAPath,
 	}
+	return cluster, nil
+}
+
+func inClusterConfig() (k8sapi.Cluster, k8sapi.AuthInfo, string, error) {
+	cluster, err := getInClusterConnectOptions(os.Getenv(kubernetesServiceHostENV), os.Getenv(kubernetesServicePortENV))
+	if err != nil {
+		return cluster, k8sapi.AuthInfo{}, "", err
+	}
 
 	token, err := os.ReadFile(serviceAccountTokenPath)
 	if err != nil {

storage/kubernetes/client_test.go

@@ -11,6 +11,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/dexidp/dex/storage/kubernetes/k8sapi"
@@ -216,6 +217,63 @@ func TestGetClusterConfigNamespace(t *testing.T) {
 	}
 }
 
+func TestGetInClusterConnectOptions(t *testing.T) {
+	type testCase struct {
+		name        string
+		host        string
+		port        string
+		expectedURL string
+		expectError bool
+	}
+
+	testCases := []testCase{
+		{
+			name:        "valid IPv4",
+			host:        "10.1.1.1",
+			port:        "443",
+			expectedURL: "https://10.1.1.1:443",
+		},
+		{
+			name:        "valid IPv6",
+			host:        "fd00::1",
+			port:        "8443",
+			expectedURL: "https://[fd00::1]:8443",
+		},
+		{
+			name:        "valid DNS name",
+			host:        "kubernetes.default.svc",
+			port:        "443",
+			expectedURL: "https://kubernetes.default.svc:443",
+		},
+		{
+			name:        "empty host",
+			host:        "",
+			port:        "443",
+			expectError: true,
+		},
+		{
+			name:        "empty port",
+			host:        "127.0.0.1",
+			port:        "",
+			expectError: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			cluster, err := getInClusterConnectOptions(tc.host, tc.port)
+
+			if tc.expectError {
+				assert.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+			assert.Equal(t, tc.expectedURL, cluster.Server)
+			assert.Equal(t, "/var/run/secrets/kubernetes.io/serviceaccount/ca.crt", cluster.CertificateAuthority)
+		})
+	}
+}
+
 const serviceAccountToken = "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.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.KViBpPwCiBwxDvAjYUUXoVvLVwqV011aLlYQpNtX12Bh8M-QAFch-3RWlo_SR00bcdFg_nZo9JKACYlF_jHMEsf__PaYms9r7vEaSg0jPfkqnL2WXZktzQRyLBr0n-bxeUrbwIWsKOAC0DfFB5nM8XoXljRmq8yAx8BAdmQp7MIFb4EOV9nYthhua6pjzYyaFSiDiYTjw7HtXOvoL8oepodJ3-37pUKS8vdBvnvUoqC4M1YAhkO5L36JF6KV_RfmG8GPEdNQfXotHcsR-3jKi1n8S5l7Xd-rhrGOhSGQizH3dORzo9GvBAhYeqbq1O-NLzm2EQUiMQayIUx7o4g3Kw"
 
 // The following program was used to generate the example token. Since we don't want to