machineid.go

// SPDX-FileCopyrightText: Copyright The Lima Authors
// SPDX-License-Identifier: Apache-2.0

package osutil

import (
	"bytes"
	"context"
	"encoding/xml"
	"fmt"
	"io"
	"os"
	"os/exec"
	"runtime"
	"strings"
	"sync"

	"github.com/sirupsen/logrus"
)

var MachineID = sync.OnceValue(func() string {
	x, err := machineID(context.Background())
	if err == nil && x != "" {
		return x
	}
	logrus.WithError(err).Debug("failed to get machine ID, falling back to use hostname instead")
	hostname, err := os.Hostname()
	if err != nil {
		panic(fmt.Errorf("failed to get hostname: %w", err))
	}
	return hostname
})

func machineID(ctx context.Context) (string, error) {
	if runtime.GOOS == "darwin" {
		ioPlatformExpertDeviceCmd := exec.CommandContext(ctx, "/usr/sbin/ioreg", "-a", "-d2", "-c", "IOPlatformExpertDevice")
		ioPlatformExpertDevice, err := ioPlatformExpertDeviceCmd.CombinedOutput()
		if err != nil {
			return "", err
		}
		return parseIOPlatformUUIDFromIOPlatformExpertDevice(bytes.NewReader(ioPlatformExpertDevice))
	}

	candidates := []string{
		"/etc/machine-id",
		"/var/lib/dbus/machine-id",
		// We don't use "/sys/class/dmi/id/product_uuid"
	}
	for _, f := range candidates {
		b, err := os.ReadFile(f)
		if err == nil {
			return strings.TrimSpace(string(b)), nil
		}
	}
	return "", fmt.Errorf("no machine-id found, tried %v", candidates)
}

func parseIOPlatformUUIDFromIOPlatformExpertDevice(r io.Reader) (string, error) {
	d := xml.NewDecoder(r)
	var (
		elem            string
		elemKeyCharData string
	)
	for {
		tok, err := d.Token()
		if err != nil {
			return "", err
		}
		switch v := tok.(type) {
		case xml.StartElement:
			elem = v.Name.Local
		case xml.EndElement:
			elem = ""
			if v.Name.Local != "key" {
				elemKeyCharData = ""
			}
		case xml.CharData:
			if elem == "string" && elemKeyCharData == "IOPlatformUUID" {
				return string(v), nil
			}
			if elem == "key" {
				elemKeyCharData = string(v)
			}
		}
	}
}