cli/algo/qmc/mask_key256.go

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2020-12-25 16:49:28 +00:00
package qmc
import (
"bytes"
"errors"
"github.com/umlock-music/cli/internal/logging"
"go.uber.org/zap"
)
var (
ErrFailToMatchMask = errors.New("can not match at least one key")
ErrTestDataLength = errors.New("invalid length of test file")
ErrMaskLength128 = errors.New("incorrect mask length 128")
ErrMaskLength44 = errors.New("incorrect mask length 44")
ErrMaskDecode = errors.New("decode mask-128 to mask-58 failed")
ErrDetectFlacMask = errors.New("can not detect mflac mask")
ErrDetectMggMask = errors.New("can not detect mgg mask")
)
type Key256Mask struct {
matrix []byte // Mask 128
}
func NewKey256FromMask128(mask128 []byte) (*Key256Mask, error) {
if len(mask128) != 128 {
return nil, ErrMaskLength128
}
q := &Key256Mask{matrix: mask128}
return q, nil
}
func NewKey256FromMask44(mask44 []byte) (*Key256Mask, error) {
mask128, err := convertKey256Mask44to128(mask44)
if err != nil {
return nil, err
}
q := &Key256Mask{matrix: mask128}
return q, nil
}
func (q *Key256Mask) getMatrix44() (mask44 []byte, err error) {
if len(q.matrix) != 128 {
return nil, ErrMaskLength128
}
matrix44 := make([]byte, 44)
idx44 := 0
for _, it256 := range key256MappingAll {
if it256 != nil {
it256Len := len(it256)
for i := 1; i < it256Len; i++ {
if q.matrix[it256[0]] != q.matrix[it256[i]] {
return nil, ErrMaskDecode
}
}
q.matrix[idx44] = q.matrix[it256[0]]
idx44++
}
}
return matrix44, nil
}
func (q *Key256Mask) Decrypt(data []byte) []byte {
dst := make([]byte, len(data))
index := -1
maskIdx := -1
for cur := 0; cur < len(data); cur++ {
index++
maskIdx++
if index == 0x8000 || (index > 0x8000 && (index+1)%0x8000 == 0) {
index++
maskIdx++
}
if maskIdx >= 128 {
maskIdx -= 128
}
dst[cur] = data[cur] ^ q.matrix[maskIdx]
}
return dst
}
func convertKey256Mask44to128(mask44 []byte) ([]byte, error) {
if len(mask44) != 44 {
return nil, ErrMaskLength44
}
mask128 := make([]byte, 128)
idx44 := 0
for _, it256 := range key256MappingAll {
if it256 != nil {
for _, idx128 := range it256 {
mask128[idx128] = mask44[idx44]
}
idx44++
}
}
return mask128, nil
}
func getDefaultMask() *Key256Mask {
y, _ := NewKey256FromMask44(defaultKey256Mask44)
return y
}
func detectMflac256Mask(input []byte) (*Key256Mask, error) {
var q *Key256Mask
var rtErr = ErrDetectFlacMask
lenData := len(input)
lenTest := 0x8000
if lenData < 0x8000 {
lenTest = lenData
}
for blockIdx := 0; blockIdx < lenTest; blockIdx += 128 {
var err error
q, err = NewKey256FromMask128(input[blockIdx : blockIdx+128])
if err != nil {
continue
}
if bytes.Equal(headerFlac, q.Decrypt(input[:len(headerFlac)])) {
rtErr = nil
break
}
}
return q, rtErr
}
func detectMgg256Mask(input []byte) (*Key256Mask, error) {
if len(input) < 0x100 {
return nil, ErrTestDataLength
}
matrixConf := make([]map[uint8]uint, 44) //meaning: [idx58][value]confidence
for i := uint(0); i < 44; i++ {
matrixConf[i] = make(map[uint8]uint)
}
page2size := input[0x54] ^ input[0xC] ^ oggPublicHeader1[0xC]
spHeader, spConf := generateOggFullHeader(int(page2size))
lenTest := len(spHeader)
for idx128 := 0; idx128 < lenTest; idx128++ {
confidence := spConf[idx128]
if confidence > 0 {
mask := input[idx128] ^ spHeader[idx128]
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idx44 := key256Mapping128to44[idx128&0x7f] // equals: [idx128 % 128]
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if _, ok2 := matrixConf[idx44][mask]; ok2 {
matrixConf[idx44][mask] += confidence
} else {
matrixConf[idx44][mask] = confidence
}
}
}
matrix := make([]uint8, 44)
var err error
for i := uint(0); i < 44; i++ {
matrix[i], err = decideMgg256MaskItemConf(matrixConf[i])
if err != nil {
return nil, err
}
}
q, err := NewKey256FromMask44(matrix)
if err != nil {
return nil, err
}
if bytes.Equal(headerOgg, q.Decrypt(input[:len(headerOgg)])) {
return q, nil
}
return nil, ErrDetectMggMask
}
func generateOggFullHeader(pageSize int) ([]byte, []uint) {
spec := make([]byte, pageSize+1)
spec[0], spec[1], spec[pageSize] = uint8(pageSize), 0xFF, 0xFF
for i := 2; i < pageSize; i++ {
spec[i] = 0xFF
}
specConf := make([]uint, pageSize+1)
specConf[0], specConf[1], specConf[pageSize] = 6, 0, 0
for i := 2; i < pageSize; i++ {
specConf[i] = 4
}
allConf := append(oggPublicConfidence1, specConf...)
allConf = append(allConf, oggPublicConfidence2...)
allHeader := bytes.Join(
[][]byte{oggPublicHeader1, spec, oggPublicHeader2},
[]byte{},
)
return allHeader, allConf
}
func decideMgg256MaskItemConf(confidence map[uint8]uint) (uint8, error) {
lenConf := len(confidence)
if lenConf == 0 {
return 0xff, ErrFailToMatchMask
} else if lenConf > 1 {
logging.Log().Warn("there are 2 potential value for the mask", zap.Any("confidence", confidence))
}
result := uint8(0)
conf := uint(0)
for idx, item := range confidence {
if item > conf {
result = idx
conf = item
}
}
return result, nil
}