Add iso builder

This adds a new package for the iso builder run directly on go.
This is extracted from the original elemental-cli and then from the now
build-less kairos-agent

This uses no deps on elemental, only deps are on kairos-agent for the
config stuff mainly.

Signed-off-by: Itxaka <itxaka.garcia@spectrocloud.com>

tools-image/enki/pkg/utils/fs.go

@@ -0,0 +1,223 @@
+package utils
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/kairos-io/enki/pkg/constants"
+	v1 "github.com/kairos-io/kairos-agent/v2/pkg/types/v1"
+	"github.com/twpayne/go-vfs"
+	"github.com/twpayne/go-vfs/vfst"
+)
+
+// MkdirAll directory and all parents if not existing
+func MkdirAll(fs v1.FS, name string, mode os.FileMode) (err error) {
+	if _, isReadOnly := fs.(*vfs.ReadOnlyFS); isReadOnly {
+		return permError("mkdir", name)
+	}
+	if name, err = fs.RawPath(name); err != nil {
+		return &os.PathError{Op: "mkdir", Path: name, Err: err}
+	}
+	return os.MkdirAll(name, mode)
+}
+
+// permError returns an *os.PathError with Err syscall.EPERM.
+func permError(op, path string) error {
+	return &os.PathError{
+		Op:   op,
+		Path: path,
+		Err:  syscall.EPERM,
+	}
+}
+
+// Copies source file to target file using Fs interface
+func CreateDirStructure(fs v1.FS, target string) error {
+	for _, dir := range []string{"/run", "/dev", "/boot", "/usr/local", "/oem"} {
+		err := MkdirAll(fs, filepath.Join(target, dir), constants.DirPerm)
+		if err != nil {
+			return err
+		}
+	}
+	for _, dir := range []string{"/proc", "/sys"} {
+		err := MkdirAll(fs, filepath.Join(target, dir), constants.NoWriteDirPerm)
+		if err != nil {
+			return err
+		}
+	}
+	err := MkdirAll(fs, filepath.Join(target, "/tmp"), constants.DirPerm)
+	if err != nil {
+		return err
+	}
+	// Set /tmp permissions regardless the umask setup
+	err = fs.Chmod(filepath.Join(target, "/tmp"), constants.TempDirPerm)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// TempDir creates a temp file in the virtual fs
+// Took from afero.FS code and adapted
+func TempDir(fs v1.FS, dir, prefix string) (name string, err error) {
+	if dir == "" {
+		dir = os.TempDir()
+	}
+	// This skips adding random stuff to the created temp dir so the temp dir created is predictable for testing
+	if _, isTestFs := fs.(*vfst.TestFS); isTestFs {
+		err = MkdirAll(fs, filepath.Join(dir, prefix), 0700)
+		if err != nil {
+			return "", err
+		}
+		name = filepath.Join(dir, prefix)
+		return
+	}
+	nconflict := 0
+	for i := 0; i < 10000; i++ {
+		try := filepath.Join(dir, prefix+nextRandom())
+		err = MkdirAll(fs, try, 0700)
+		if os.IsExist(err) {
+			if nconflict++; nconflict > 10 {
+				randmu.Lock()
+				rand = reseed()
+				randmu.Unlock()
+			}
+			continue
+		}
+		if err == nil {
+			name = try
+		}
+		break
+	}
+	return
+}
+
+// Random number state.
+// We generate random temporary file names so that there's a good
+// chance the file doesn't exist yet - keeps the number of tries in
+// TempFile to a minimum.
+var rand uint32
+var randmu sync.Mutex
+
+func reseed() uint32 {
+	return uint32(time.Now().UnixNano() + int64(os.Getpid()))
+}
+
+func nextRandom() string {
+	randmu.Lock()
+	r := rand
+	if r == 0 {
+		r = reseed()
+	}
+	r = r*1664525 + 1013904223 // constants from Numerical Recipes
+	rand = r
+	randmu.Unlock()
+	return strconv.Itoa(int(1e9 + r%1e9))[1:]
+}
+
+// CopyFile Copies source file to target file using Fs interface. If target
+// is  directory source is copied into that directory using source name file.
+func CopyFile(fs v1.FS, source string, target string) (err error) {
+	return ConcatFiles(fs, []string{source}, target)
+}
+
+// IsDir check if the path is a dir
+func IsDir(fs v1.FS, path string) (bool, error) {
+	fi, err := fs.Stat(path)
+	if err != nil {
+		return false, err
+	}
+	return fi.IsDir(), nil
+}
+
+// ConcatFiles Copies source files to target file using Fs interface.
+// Source files are concatenated into target file in the given order.
+// If target is a directory source is copied into that directory using
+// 1st source name file.
+func ConcatFiles(fs v1.FS, sources []string, target string) (err error) {
+	if len(sources) == 0 {
+		return fmt.Errorf("Empty sources list")
+	}
+	if dir, _ := IsDir(fs, target); dir {
+		target = filepath.Join(target, filepath.Base(sources[0]))
+	}
+
+	targetFile, err := fs.Create(target)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if err == nil {
+			err = targetFile.Close()
+		} else {
+			_ = fs.Remove(target)
+		}
+	}()
+
+	var sourceFile *os.File
+	for _, source := range sources {
+		sourceFile, err = fs.Open(source)
+		if err != nil {
+			break
+		}
+		_, err = io.Copy(targetFile, sourceFile)
+		if err != nil {
+			break
+		}
+		err = sourceFile.Close()
+		if err != nil {
+			break
+		}
+	}
+
+	return err
+}
+
+// DirSize returns the accumulated size of all files in folder
+func DirSize(fs v1.FS, path string) (int64, error) {
+	var size int64
+	err := vfs.Walk(fs, path, func(_ string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if !info.IsDir() {
+			size += info.Size()
+		}
+		return err
+	})
+	return size, err
+}
+
+// Check if a file or directory exists.
+func Exists(fs v1.FS, path string) (bool, error) {
+	_, err := fs.Stat(path)
+	if err == nil {
+		return true, nil
+	}
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	return false, err
+}
+
+// CalcFileChecksum opens the given file and returns the sha256 checksum of it.
+func CalcFileChecksum(fs v1.FS, fileName string) (string, error) {
+	f, err := fs.Open(fileName)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	h := sha256.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%x", h.Sum(nil)), nil
+}