ncmdump-go/ncmcrypt/ncmcrypt.go

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package ncmcrypt
import (
"bytes"
"encoding/base64"
"encoding/binary"
"fmt"
"github.com/bogem/id3v2/v2"
"github.com/go-flac/flacpicture"
"github.com/go-flac/go-flac"
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"github.com/taurusxin/ncmdump-go/utils"
"io"
"net/http"
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"os"
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"path/filepath"
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)
type NcmFormat = string
const (
Mp3 NcmFormat = "mp3"
)
const (
Flac NcmFormat = "flac"
)
type NeteaseCloudMusic struct {
sCoreKey [17]byte
sModifyKey [17]byte
mPng [8]byte
mFilePath string
mDumpFilePath string
mFormat NcmFormat
mImageData []byte
mFileStream *os.File
mKeyBox [256]byte
mMetadata *NeteaseClousMusicMetadata
mAlbumPicUrl string
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}
func (ncm *NeteaseCloudMusic) read(buffer *[]byte, size int) int {
if len(*buffer) < size {
*buffer = make([]byte, size)
}
res, err := ncm.mFileStream.Read(*buffer)
if err != nil {
return 0
}
return res
}
func (ncm *NeteaseCloudMusic) openFile() bool {
file, err := os.Open(ncm.mFilePath)
if err != nil {
return false
}
ncm.mFileStream = file
return true
}
func (ncm *NeteaseCloudMusic) isNcmFile() bool {
header := make([]byte, 4)
// check magic header 4E455443 4D414446
if ncm.read(&header, 4) != 4 {
return false
}
if int(binary.LittleEndian.Uint32(header)) != 0x4E455443 {
return false
}
if ncm.read(&header, 4) != 4 {
return false
}
if int(binary.LittleEndian.Uint32(header)) != 0x4D414446 {
return false
}
return true
}
func (ncm *NeteaseCloudMusic) buildKeyBox(key []byte, keyLen int) {
for i := 0; i < 256; i++ {
ncm.mKeyBox[i] = byte(i)
}
var swap uint8 = 0
var c uint8 = 0
var lastByte uint8 = 0
var keyOffset uint8 = 0
for i := 0; i < 256; i++ {
swap = ncm.mKeyBox[i]
c = (swap + lastByte + key[keyOffset]) & 0xff
keyOffset++
if int(keyOffset) >= keyLen {
keyOffset = 0
}
ncm.mKeyBox[i] = ncm.mKeyBox[c]
ncm.mKeyBox[c] = swap
lastByte = c
}
}
func (ncm *NeteaseCloudMusic) mimeType() string {
if bytes.HasPrefix(ncm.mImageData, ncm.mPng[:]) {
return "image/png"
}
return "image/jpeg"
}
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// Dump encrypted ncm file to normal music file. If `targetDir` is "", the converted file will be saved to the original directory.
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func (ncm *NeteaseCloudMusic) Dump(targetDir string) (bool, error) {
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ncm.mDumpFilePath = ncm.mFilePath
var outputStream *os.File
buffer := make([]byte, 0x8000)
findFormatFlag := false
for {
n := ncm.read(&buffer, len(buffer))
if n == 0 {
break
}
for i := 0; i < n; i++ {
j := (i + 1) & 0xff
buffer[i] ^= ncm.mKeyBox[(ncm.mKeyBox[j]+ncm.mKeyBox[(int(ncm.mKeyBox[j])+j)&0xff])&0xff]
}
if !findFormatFlag {
if buffer[0] == 0x49 && buffer[1] == 0x44 && buffer[2] == 0x33 {
ncm.mFormat = Mp3
ncm.mDumpFilePath = utils.ReplaceExtension(ncm.mDumpFilePath, ".mp3")
} else {
ncm.mFormat = Flac
ncm.mDumpFilePath = utils.ReplaceExtension(ncm.mDumpFilePath, ".flac")
}
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if targetDir != "" { // change save dir
ncm.mDumpFilePath = filepath.Join(targetDir, filepath.Base(ncm.mDumpFilePath))
}
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findFormatFlag = true
output, err := os.Create(ncm.mDumpFilePath)
if err != nil {
return false, fmt.Errorf("create output file failed")
}
outputStream = output
}
outputStream.Write(buffer)
}
outputStream.Close()
return true, nil
}
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// FixMetadata will fix the missing metadata for target music file, the source of the metadata comes from origin ncm file.
// Since NeteaseCloudMusic version 3.0, the album cover image is no longer embedded in the ncm file. If the parameter is true, it means downloading the image from the NetEase server and embedding it into the target music file (network connection required)
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func (ncm *NeteaseCloudMusic) FixMetadata(fetchAlbumImageFromRemote bool) (bool, error) {
if fetchAlbumImageFromRemote {
// get the album pic from url
resp, err := http.Get(ncm.mAlbumPicUrl)
if err != nil {
return false, err
}
if resp != nil {
if resp.StatusCode == http.StatusOK {
bodyBytes, err := io.ReadAll(resp.Body)
if err != nil {
return false, err
}
ncm.mImageData = bodyBytes
}
}
}
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if ncm.mFormat == Mp3 {
audioFile, err := id3v2.Open(ncm.mDumpFilePath, id3v2.Options{Parse: true})
if err != nil {
return false, err
}
defer audioFile.Close()
audioFile.SetTitle(ncm.mMetadata.mName)
audioFile.SetArtist(ncm.mMetadata.mArtist)
audioFile.SetAlbum(ncm.mMetadata.mAlbum)
if len(ncm.mImageData) > 0 {
pic := id3v2.PictureFrame{
Encoding: id3v2.EncodingUTF8,
MimeType: ncm.mimeType(),
PictureType: id3v2.PTFrontCover,
Description: "",
Picture: ncm.mImageData,
}
audioFile.AddAttachedPicture(pic)
}
err = audioFile.Save()
if err != nil {
return false, err
}
} else if ncm.mFormat == Flac {
audioFile, err := flac.ParseFile(ncm.mDumpFilePath)
if err != nil {
return false, err
}
if len(ncm.mImageData) > 0 {
pic, err := flacpicture.NewFromImageData(flacpicture.PictureTypeFrontCover, "",
ncm.mImageData, ncm.mimeType())
if err != nil {
return false, err
}
pictureMeta := pic.Marshal()
audioFile.Meta = append(audioFile.Meta, &pictureMeta)
}
generalMeta := &flac.MetaDataBlock{
Type: flac.VorbisComment,
Data: []byte(fmt.Sprintf("title=%s\nartist=%s\nalbum=%s", ncm.mMetadata.mName, ncm.mMetadata.mArtist, ncm.mMetadata.mAlbum)),
}
audioFile.Meta = append(audioFile.Meta, generalMeta)
err = audioFile.Save(ncm.mDumpFilePath)
if err != nil {
return false, err
}
}
return true, nil
}
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// GetDumpFilePath returns the absolute path of dumped music file
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func (ncm *NeteaseCloudMusic) GetDumpFilePath() string {
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path, err := filepath.Abs(ncm.mDumpFilePath)
if err != nil {
return ncm.mDumpFilePath
}
return path
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}
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// NewNeteaseCloudMusic returns a new NeteaseCloudMusic instance, if the format of the file is incorrect, the error will be returned.
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func NewNeteaseCloudMusic(filePath string) (*NeteaseCloudMusic, error) {
ncm := &NeteaseCloudMusic{
sCoreKey: [17]byte{0x68, 0x7A, 0x48, 0x52, 0x41, 0x6D, 0x73, 0x6F, 0x35, 0x6B, 0x49, 0x6E, 0x62, 0x61, 0x78, 0x57, 0},
sModifyKey: [17]byte{0x23, 0x31, 0x34, 0x6C, 0x6A, 0x6B, 0x5F, 0x21, 0x5C, 0x5D, 0x26, 0x30, 0x55, 0x3C, 0x27, 0x28, 0},
mPng: [8]byte{0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A},
mFilePath: filePath,
}
if !ncm.openFile() {
return nil, fmt.Errorf("open file failed")
}
if !ncm.isNcmFile() {
return nil, fmt.Errorf("not a ncm file")
}
// actually this 2 bytes is the version, now we just skip it
if _, err := ncm.mFileStream.Seek(2, 1); err != nil {
return nil, fmt.Errorf("seek version failed")
}
// the length of the RC4 key, encrypted by AES128
n := make([]byte, 4)
if ncm.read(&n, len(n)) != 4 {
return nil, fmt.Errorf("read key len failed")
}
keyLen := int(binary.LittleEndian.Uint32(n))
keydata := make([]byte, keyLen)
ncm.read(&keydata, keyLen)
for i := range keydata {
keydata[i] ^= 0x64
}
mKeyData, err := utils.AesEcbDecrypt(ncm.sCoreKey[:16], keydata)
if err != nil {
return nil, fmt.Errorf("decrypt key failed")
}
// build the key box
ncm.buildKeyBox(mKeyData[17:], len(mKeyData)-17)
if ncm.read(&n, len(n)) != 4 {
return nil, fmt.Errorf("read metadata len failed")
}
metadataLen := int(binary.LittleEndian.Uint32(n))
if metadataLen <= 0 {
// process meta here
ncm.mMetadata = nil
} else {
// read metadata
modifyData := make([]byte, metadataLen)
ncm.read(&modifyData, metadataLen)
for i := range modifyData {
modifyData[i] ^= 0x63
}
// escape `163 key(Don't modify):`
swapModifyData := string(modifyData[22:])
modifyOutData, err := base64.StdEncoding.DecodeString(swapModifyData)
if err != nil {
panic("base64 decode modify data failed")
}
modifyDecryptData, err := utils.AesEcbDecrypt(ncm.sModifyKey[:16], modifyOutData)
if err != nil {
panic("decrypt modify data failed")
}
// escape `music:`
mMetadataString := string(modifyDecryptData[6:])
// extract the album pic url
ncm.mAlbumPicUrl = GetAlbumPicUrl(mMetadataString)
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ncm.mMetadata = NewNeteaseCloudMusicMetadata(mMetadataString)
}
// skip the 5 bytes gap
if _, err := ncm.mFileStream.Seek(5, 1); err != nil {
return nil, fmt.Errorf("seek gap failed")
}
// read the cover frame
coverFrameLen := make([]byte, 4)
if ncm.read(&coverFrameLen, len(coverFrameLen)) != 4 {
return nil, fmt.Errorf("read cover frame len failed")
}
if ncm.read(&n, len(n)) != 4 {
return nil, fmt.Errorf("read cover frame data len failed")
}
coverFrameLenInt := int(binary.LittleEndian.Uint32(coverFrameLen))
coverFrameDataLen := int(binary.LittleEndian.Uint32(n))
if coverFrameDataLen > 0 {
ncm.read(&ncm.mImageData, coverFrameDataLen)
}
ncm.mFileStream.Seek(int64(coverFrameLenInt)-int64(coverFrameDataLen), 1)
return ncm, nil
}