Add metadata client

builder/azure/chroot/metadata.go

@@ -0,0 +1,71 @@
+package chroot
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+
+	"github.com/hashicorp/go-retryablehttp"
+)
+
+// DefaultMetadataClient is the default instance metadata client for Azure. Replace this variable for testing purposes only
+var DefaultMetadataClient = NewMetadataClient()
+
+// MetadataClient holds methods that Packer uses to get information about the current VM
+type MetadataClient interface {
+	VMResourceID() (string, error)
+}
+
+// metadataClient implements MetadataClient
+type metadataClient struct{}
+
+const imdsURL = "http://169.254.169.254/metadata/instance?api-version=2017-08-01"
+
+// VMResourceID returns the resource ID of the current VM
+func (metadataClient) VMResourceID() (string, error) {
+	wc := retryablehttp.NewClient()
+	wc.RetryMax = 5
+
+	req, err := retryablehttp.NewRequest(http.MethodGet, imdsURL, nil)
+	if err != nil {
+		return "", err
+	}
+	req.Header.Add("Metadata", "true")
+
+	res, err := wc.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer res.Body.Close()
+
+	d, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return "", err
+	}
+
+	var vminfo struct {
+		Compute struct {
+			Name              string
+			ResourceGroupName string
+			SubscriptionID    string
+		}
+	}
+
+	err = json.Unmarshal(d, &vminfo)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("/subscriptions/%s/resourceGroups/%s/providers/Microsoft.Compute/virtualMachines/%s",
+		vminfo.Compute.Name,
+		vminfo.Compute.ResourceGroupName,
+		vminfo.Compute.SubscriptionID,
+	), nil
+
+}
+
+// NewMetadataClient creates a new instance metadata client
+func NewMetadataClient() MetadataClient {
+	return metadataClient{}
+}

builder/azure/chroot/metadata_test.go

@@ -0,0 +1,24 @@
+package chroot
+
+import (
+	"testing"
+
+	"github.com/Azure/go-autorest/autorest/azure"
+
+	"github.com/hashicorp/packer/builder/azure/common"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_MetadataReturnsVMResourceID(t *testing.T) {
+	if !common.IsAzure() {
+		t.Skipf("Not running on Azure, skipping live IMDS test")
+	}
+	mdc := NewMetadataClient()
+	id, err := mdc.VMResourceID()
+	assert.Nil(t, err)
+	assert.NotEqual(t, id, "", "Expected VMResourceID to return non-empty string because we are running on Azure")
+
+	vm, err := azure.ParseResourceID(id)
+	assert.Nil(t, err, "%q is not parsable as an Azure resource id", id)
+	t.Logf("VM: %+v", vm)
+}