feat: add support for windows MAC hex dump (#4122)

* feat: add support for windows MAC hex dump

* test: invalid MAC address length

* fix: typo

* fix: comment

---------

Co-authored-by: Keith Nguyen <[email protected]>

Author: ecigar13

cns/imds/client.go

@@ -9,6 +9,7 @@ import (
 	"net"
 	"net/http"
 	"net/url"
+	"strings"
 
 	"github.com/avast/retry-go/v4"
 	"github.com/pkg/errors"
@@ -45,17 +46,18 @@ func RetryAttempts(attempts uint) ClientOption {
 }
 
 const (
-	vmUniqueIDProperty    = "vmId"
-	imdsComputePath       = "/metadata/instance/compute"
-	imdsNetworkPath       = "/metadata/instance/network"
-	imdsVersionsPath      = "/metadata/versions"
-	imdsDefaultAPIVersion = "api-version=2021-01-01"
-	imdsNCDetailsVersion  = "api-version=2025-07-24"
-	imdsFormatJSON        = "format=json"
-	metadataHeaderKey     = "Metadata"
-	metadataHeaderValue   = "true"
-	defaultRetryAttempts  = 3
-	defaultIMDSEndpoint   = "http://169.254.169.254"
+	vmUniqueIDProperty         = "vmId"
+	imdsComputePath            = "/metadata/instance/compute"
+	imdsNetworkPath            = "/metadata/instance/network"
+	imdsVersionsPath           = "/metadata/versions"
+	imdsDefaultAPIVersion      = "api-version=2021-01-01"
+	imdsNCDetailsVersion       = "api-version=2025-07-24"
+	imdsMACAddressStringLength = 12 // 6 bytes in hex equals 12 characters
+	imdsFormatJSON             = "format=json"
+	metadataHeaderKey          = "Metadata"
+	metadataHeaderValue        = "true"
+	defaultRetryAttempts       = 3
+	defaultIMDSEndpoint        = "http://169.254.169.254"
 )
 
 var (
@@ -218,14 +220,36 @@ func (h *HardwareAddr) UnmarshalJSON(data []byte) error {
 	if err := json.Unmarshal(data, &s); err != nil {
 		return errors.Wrap(err, "failed to unmarshal JSON data")
 	}
-	mac, err := net.ParseMAC(s)
+
+	mac, err := parseMacAddress(s)
 	if err != nil {
 		return errors.Wrap(err, "failed to parse MAC address")
 	}
 	*h = HardwareAddr(mac)
 	return nil
 }
 
+// parseMacAddress is a wrapper around net.ParseMAC to handle Windows MAC address. Windows MAC address is a pure hex
+// dump without delimiter, so we need to add delimiters. This happens when CNS gets MAC address from IMDS.
+func parseMacAddress(s string) (net.HardwareAddr, error) {
+	if !strings.ContainsAny(s, ":-.") && len(s) == imdsMACAddressStringLength {
+		var sb strings.Builder
+		for i := 0; i < len(s); i += 2 {
+			if i > 0 {
+				sb.WriteByte(':')
+			}
+			sb.WriteString(s[i : i+2])
+		}
+		s = sb.String()
+	}
+
+	mac, err := net.ParseMAC(s)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to parse MAC address")
+	}
+	return mac, nil
+}
+
 func (h *HardwareAddr) String() string {
 	return net.HardwareAddr(*h).String()
 }

cns/imds/client_test.go

@@ -111,7 +111,7 @@ func TestGetNetworkInterfaces(t *testing.T) {
             },
             {
                 "interfaceCompartmentID": "",
-                "macAddress": "00:00:5e:00:53:02"
+                "macAddress": "00005e005302"
             }
         ]
     }`)
@@ -160,6 +160,37 @@ func TestGetNetworkInterfaces(t *testing.T) {
 	assert.NotEqual(t, firstMAC.String(), secondMAC.String(), "MAC addresses should be different")
 }
 
+func TestGetNetworkInterfacesInvalidMAC(t *testing.T) {
+	networkInterfaces := []byte(`{
+        "interface": [
+            {
+                "interfaceCompartmentID": "nc-12345-67890",
+                "macAddress": "00005e00530" // incorrect windows MAC address length
+            },
+        ]
+    }`)
+
+	mockIMDSServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		metadataHeader := r.Header.Get("Metadata")
+		assert.Equal(t, "true", metadataHeader)
+
+		assert.Contains(t, r.URL.Path, "/metadata/instance/network")
+
+		w.WriteHeader(http.StatusOK)
+		_, writeErr := w.Write(networkInterfaces)
+		if writeErr != nil {
+			t.Errorf("error writing response: %v", writeErr)
+			return
+		}
+	}))
+	defer mockIMDSServer.Close()
+
+	imdsClient := imds.NewClient(imds.Endpoint(mockIMDSServer.URL))
+	interfaces, err := imdsClient.GetNetworkInterfaces(context.Background())
+	require.Error(t, err, "expected error for invalid MAC address")
+	require.Nil(t, interfaces, "expected nil interfaces on error")
+}
+
 func TestGetNetworkInterfacesInvalidEndpoint(t *testing.T) {
 	imdsClient := imds.NewClient(imds.Endpoint(string([]byte{0x7f})), imds.RetryAttempts(1))
 	_, err := imdsClient.GetNetworkInterfaces(context.Background())