virtualbox: use local VBoxGuestAdditions.iso by default

fixes #1123

builder/virtualbox/common/driver.go

@@ -25,6 +25,9 @@ type Driver interface {
 	// Import a VM
 	Import(string, string, string) error
 
+	// The complete path to the Guest Additions ISO
+	Iso() (string, error)
+
 	// Checks if the VM with the given name is running.
 	IsRunning(string) (bool, error)
 

builder/virtualbox/common/driver_4_2.go

@@ -40,6 +40,35 @@ func (d *VBox42Driver) Delete(name string) error {
 	return d.VBoxManage("unregistervm", name, "--delete")
 }
 
+func (d *VBox42Driver) Iso() (string, error) {
+	var stdout bytes.Buffer
+
+	cmd := exec.Command(d.VBoxManagePath, "list", "systemproperties")
+	cmd.Stdout = &stdout
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+
+	DefaultGuestAdditionsRe := regexp.MustCompile("Default Guest Additions ISO:(.*)")
+
+	for _, line := range strings.Split(stdout.String(), "\n") {
+		// Need to trim off CR character when running in windows
+		line = strings.TrimRight(line, "\r")
+
+		matches := DefaultGuestAdditionsRe.FindStringSubmatch(line)
+		if matches == nil {
+			continue
+		}
+
+		isoname := strings.Trim(matches[1], " \r\n")
+		log.Printf("Found Default Guest Additions ISO: %s", isoname)
+
+		return isoname, nil
+	}
+
+	return "", fmt.Errorf("Cannot find \"Default Guest Additions ISO\" in vboxmanage output")
+}
+
 func (d *VBox42Driver) Import(name, path, opts string) error {
 	args := []string{
 		"import", path,

builder/virtualbox/common/driver_mock.go

@@ -19,6 +19,9 @@ type DriverMock struct {
 	ImportOpts   string
 	ImportErr    error
 
+	IsoCalled bool
+	IsoErr    error
+
 	IsRunningName   string
 	IsRunningReturn bool
 	IsRunningErr    error
@@ -60,6 +63,11 @@ func (d *DriverMock) Import(name, path, opts string) error {
 	return d.ImportErr
 }
 
+func (d *DriverMock) Iso() (string, error) {
+	d.IsoCalled = true
+	return "", d.IsoErr
+}
+
 func (d *DriverMock) IsRunning(name string) (bool, error) {
 	d.Lock()
 	defer d.Unlock()

builder/virtualbox/common/step_download_guest_additions.go

@@ -62,14 +62,7 @@ func (s *StepDownloadGuestAdditions) Run(state multistep.StateBag) multistep.Ste
 	// Use provided version or get it from virtualbox.org
 	var checksum string
 
-	if s.GuestAdditionsSHA256 != "" {
-		checksum = s.GuestAdditionsSHA256
-	} else {
-		checksum, action = s.downloadAdditionsSHA256(state, version, additionsName)
-		if action != multistep.ActionContinue {
-			return action
-		}
-	}
+	checksumType := "sha256"
 
 	// Use the provided source (URL or file path) or generate it
 	url := s.GuestAdditionsURL
@@ -86,11 +79,29 @@ func (s *StepDownloadGuestAdditions) Run(state multistep.StateBag) multistep.Ste
 			return multistep.ActionHalt
 		}
 	} else {
+		url, err = driver.Iso()
+
+		if err == nil {
+			checksumType = "none"
+		} else {
+			ui.Error(err.Error())
 			url = fmt.Sprintf(
 				"http://download.virtualbox.org/virtualbox/%s/%s",
 				version,
 				additionsName)
 		}
+	}
+
+	if checksumType != "none" {
+		if s.GuestAdditionsSHA256 != "" {
+			checksum = s.GuestAdditionsSHA256
+		} else {
+			checksum, action = s.downloadAdditionsSHA256(state, version, additionsName)
+			if action != multistep.ActionContinue {
+				return action
+			}
+		}
+	}
 
 	url, err = common.DownloadableURL(url)
 	if err != nil {
@@ -104,7 +115,7 @@ func (s *StepDownloadGuestAdditions) Run(state multistep.StateBag) multistep.Ste
 
 	downStep := &common.StepDownload{
 		Checksum:     checksum,
-		ChecksumType: "sha256",
+		ChecksumType: checksumType,
 		Description:  "Guest additions",
 		ResultKey:    "guest_additions_path",
 		Url:          []string{url},