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package main
import (
type luksHeader struct {
Magic [6]uint8
Version uint16
CipherName [32]byte
CipherMode [32]byte
HashSpec [32]uint8
PayloadOffset uint32
KeyBytes uint32
MkDigest [20]byte
MkDigestSalt [32]byte
MkDigestIter uint32
UUID [40]byte
var errNotFound = errors.New("not found")
func probeLUKS(r io.ReadSeeker) (string, error) {
if _, err := r.Seek(0, io.SeekStart); err != nil {
return "", err
var hdr luksHeader
if err := binary.Read(r, binary.LittleEndian, &hdr); err != nil {
return "", err
wantMagic := append([]byte("LUKS"), 0xba, 0xbe)
if !bytes.Equal(hdr.Magic[:], wantMagic) {
return "", errNotFound
return string(hdr.UUID[:bytes.IndexByte(hdr.UUID[:], 0)]), nil
func blkid(r io.ReadSeeker) (string, error) {
uuid, err := probeLUKS(r)
if err != nil && err != errNotFound {
return "", err
if err == nil {
return uuid, nil
// probe ext4
const extSuperblockOffset = 0x400
if _, err := r.Seek(extSuperblockOffset, io.SeekStart); err != nil {
return "", err
var sb ext2SuperBlock
if err := binary.Read(r, binary.LittleEndian, &sb); err != nil {
return "", err
if sb.Magic != 0xef53 {
return "", fmt.Errorf("no ext4 superblock found")
buf := sb.UUID
return fmt.Sprintf(
buf[0], buf[1], buf[2], buf[3],
buf[4], buf[5],
buf[6], buf[7],
buf[8], buf[9],
buf[10], buf[11], buf[12], buf[13], buf[14], buf[15]), nil
type ext2SuperBlock struct {
InodesCount uint32
BlocksCount uint32
ReservedBlocksCount uint32
FreeBlocksCount uint32
FreeInodesCount uint32
FirstDataBlock uint32
LogBlockSize uint32
LogFragSize int32
BlocksPerGroup uint32
FragsPerGroup uint32
InodesPerGroup uint32
Mtime uint32
Wtime uint32
MountCount uint16
MaxMountCount int16
Magic uint16
State uint16
Errors uint16
MinorRevLevel uint16
LastCheck uint32
CheckInterval uint32
CreatorOS uint32
RevLevel uint32
DefResuid uint16
DefResgid uint16
FirstIno uint32
InodeSize uint16
BlockGroupNr uint16
FeatureCompat uint32
FeatureIncompat uint32
FeatureRoCompat uint32
UUID [16]uint8
// remaining fields elided (irrelevant for probing)
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