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" "io" "ncmdump/utils" "net/http" "os" ) 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 } 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" } func (ncm *NeteaseCloudMusic) Dump() (bool, error) { 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") } 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 } func (ncm *NeteaseCloudMusic) FixMetadata() (bool, error) { 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 } func (ncm *NeteaseCloudMusic) GetDumpFilePath() string { return ncm.mDumpFilePath } 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) 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) } else { // get the album pic from url resp, err := http.Get(ncm.mAlbumPicUrl) if err != nil { } if resp != nil { if resp.StatusCode == http.StatusOK { bodyBytes, err := io.ReadAll(resp.Body) if err != nil { } ncm.mImageData = bodyBytes } } } ncm.mFileStream.Seek(int64(coverFrameLenInt)-int64(coverFrameDataLen), 1) return ncm, nil }