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