http-boot-config/config/prober/prober.go

package prober

import (
	"bytes"
	"errors"
	"fmt"
	"os/exec"
	"regexp"
	"strconv"
	"strings"
)

var efiBootmgrRegexp = regexp.MustCompile(`Boot(?P<id>[0-9A-F]+)\* (?P<name>.+)\t(.+\(.+,.+,(?P<disk_id>[0-9a-f-]+),.+,.+\))/File\((?P<filepath>.+)\)`)
var activeRegexp = regexp.MustCompile(`BootCurrent: (\d+)`)
var bootOrderRegexp = regexp.MustCompile(`BootOrder: ((?:[0-9A-F]{4},?)+)`)

const HTTPBootName = "httpboot.efi"
const HTTPBootLabel = "HTTP_BOOT"
const execPath = "/usr/bin/efibootmgr"

type EfiApp struct {
	ID     int
	Name   string
	Path   string
	DiskID string
	Active bool
}

func efiAppFromBootMgrOutput(rawVal string, activeId int) (app EfiApp, ok bool) {
	match := efiBootmgrRegexp.FindStringSubmatch(rawVal)
	if len(match) == 0 {
		return
	}
	result := make(map[string]string)
	for i, name := range efiBootmgrRegexp.SubexpNames() {
		if i != 0 && name != "" {
			result[name] = match[i]
		}
	}
	id, ok := result["id"]
	if !ok {
		return
	}
	idInt, err := strconv.ParseInt(id, 16, 32)
	if err != nil {
		return app, false
	}
	name, ok := result["name"]
	if !ok {
		return
	}
	filepath, ok := result["filepath"]
	if !ok {
		return
	}
	disk_id, ok := result["disk_id"]
	if !ok {
		return
	}
	return EfiApp{
		ID:     int(idInt),
		Name:   strings.TrimSpace(name),
		Path:   strings.TrimSpace(filepath),
		Active: int(idInt) == activeId,
		DiskID: disk_id,
	}, true
}

func getActiveEFIApp(output string) (int, error) {
	match := activeRegexp.FindStringSubmatch(output)
	if len(match) == 0 {
		return -1, errors.New("no active boot image found")
	}
	strId := match[1]
	id, err := strconv.Atoi(strId)
	if err != nil {
		return -1, err
	}
	return id, nil
}

func GetEFIApps() (apps []EfiApp, err error) {
	cmd := exec.Command("/usr/bin/efibootmgr")
	var out bytes.Buffer
	cmd.Stdout = &out

	err = cmd.Run()
	if err != nil {
		return
	}
	if cmd.ProcessState.ExitCode() != 0 {
		return nil, fmt.Errorf("error running efibootmgr, returncode %d", cmd.ProcessState.ExitCode())
	}

	outStr := out.String()
	activeBootID, err := getActiveEFIApp(outStr)
	if err != nil {
		return
	}

	for _, l := range strings.Split(outStr, "\n") {
		app, ok := efiAppFromBootMgrOutput(l, activeBootID)
		if !ok {
			continue
		}
		apps = append(apps, app)
	}
	return
}

func Installed() (bool, error) {
	apps, err := GetEFIApps()
	if err != nil {
		return false, fmt.Errorf("failed to get list of EFI applications: %w", err)
	}
	for _, a := range apps {
		if a.Name == HTTPBootLabel {
			return true, nil
		}
	}
	return false, nil
}

func getHTTPBoot() (EfiApp, error) {
	apps, err := GetEFIApps()
	if err != nil {
		return EfiApp{}, fmt.Errorf("failed to get installed EFI applications: %w", err)
	}

	for _, a := range apps {
		if a.Name == HTTPBootLabel {
			return a, nil
		}
	}
	return EfiApp{}, errors.New("HTTP_BOOT not found")
}

func IsHTTPBootNext() (present bool, err error) {
	httpBootApp, err := getHTTPBoot()
	if err != nil {
		return false, fmt.Errorf("failed to get HTTP_BOOT config: %w", err)
	}

	cmd := exec.Command("/usr/bin/efibootmgr")
	var out bytes.Buffer
	cmd.Stdout = &out

	err = cmd.Run()
	if err != nil {
		return
	}
	if cmd.ProcessState.ExitCode() != 0 {
		return false, fmt.Errorf("error running efibootmgr, returncode %d", cmd.ProcessState.ExitCode())
	}

	outStr := out.String()
	match := bootOrderRegexp.FindStringSubmatch(outStr)
	if len(match) == 0 {
		return false, errors.New("no boot order found")
	}
	orderedBootOptionsStr := strings.Split(match[1], ",")
	var orderedBootOptionsInt []int
	for _, o := range orderedBootOptionsStr {
		if oInt, convEerr := strconv.ParseInt(o, 16, 32); err != nil {
			return false, fmt.Errorf("invalid value for boot option: %w", convEerr)
		} else {
			orderedBootOptionsInt = append(orderedBootOptionsInt, int(oInt))
		}
	}
	return orderedBootOptionsInt[0] == httpBootApp.ID, nil
}

func Install(path, device string) (err error) {
	partNum := device[len(device)-1:]
	diskDev := device[:len(device)-1]

	cmd := exec.Command(execPath, "--create", "--label", HTTPBootLabel, "--loader", path, "--part", partNum, "--disk", diskDev)
	var errBuf bytes.Buffer
	cmd.Stderr = &errBuf

	err = cmd.Run()
	var exitErr exec.ExitError
	e := &exitErr
	if err != nil && !errors.As(err, &e) {
		return err
	}
	if cmd.ProcessState.ExitCode() != 0 {
		stderr := errBuf.String()
		return fmt.Errorf("error setting variable, returncode %d, stderr %q", cmd.ProcessState.ExitCode(), stderr)
	}
	return nil
}