cli/algo/qmc/qmc.go

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package qmc
import (
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"bytes"
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"encoding/binary"
"errors"
"io"
"strconv"
"strings"
"github.com/unlock-music/cli/algo/common"
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)
type Decoder struct {
r io.ReadSeeker
fileExt string
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audioLen int
decodedKey []byte
cipher streamCipher
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offset int
rawMetaExtra1 int
rawMetaExtra2 int
}
// Read implements io.Reader, offer the decrypted audio data.
// Validate should call before Read to check if the file is valid.
func (d *Decoder) Read(p []byte) (int, error) {
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n := len(p)
if d.audioLen-d.offset <= 0 {
return 0, io.EOF
} else if d.audioLen-d.offset < n {
n = d.audioLen - d.offset
}
m, err := d.r.Read(p[:n])
if m == 0 {
return 0, err
}
d.cipher.Decrypt(p[:m], d.offset)
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d.offset += m
return m, err
}
func NewDecoder(r io.ReadSeeker) (*Decoder, error) {
d := &Decoder{r: r}
err := d.searchKey()
if err != nil {
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return nil, err
}
if len(d.decodedKey) > 300 {
d.cipher, err = NewRC4Cipher(d.decodedKey)
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if err != nil {
return nil, err
}
} else if len(d.decodedKey) != 0 {
d.cipher, err = NewMapCipher(d.decodedKey)
if err != nil {
return nil, err
}
} else {
d.cipher = NewStaticCipher()
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}
_, err = d.r.Seek(0, io.SeekStart)
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if err != nil {
return nil, err
}
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return d, nil
}
func (d *Decoder) Validate() error {
buf := make([]byte, 16)
if _, err := io.ReadFull(d.r, buf); err != nil {
return err
}
_, err := d.r.Seek(0, io.SeekStart)
if err != nil {
return err
}
d.cipher.Decrypt(buf, 0)
fileExt, ok := common.SniffAll(buf)
if !ok {
return errors.New("detect file type failed")
}
d.fileExt = fileExt
return nil
}
func (d *Decoder) GetFileExt() string {
return d.fileExt
}
func (d *Decoder) searchKey() error {
fileSizeM4, err := d.r.Seek(-4, io.SeekEnd)
if err != nil {
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return err
}
buf, err := io.ReadAll(io.LimitReader(d.r, 4))
if err != nil {
return err
}
if string(buf) == "QTag" {
return d.readRawMetaQTag()
} else if string(buf) == "STag" {
return errors.New("qmc: file with 'STag' suffix doesn't contains media key")
} else {
size := binary.LittleEndian.Uint32(buf)
if size < 0x300 && size != 0 {
return d.readRawKey(int64(size))
}
// try to use default static cipher
d.audioLen = int(fileSizeM4 + 4)
return nil
}
}
func (d *Decoder) readRawKey(rawKeyLen int64) error {
audioLen, err := d.r.Seek(-(4 + rawKeyLen), io.SeekEnd)
if err != nil {
return err
}
d.audioLen = int(audioLen)
rawKeyData, err := io.ReadAll(io.LimitReader(d.r, rawKeyLen))
if err != nil {
return err
}
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// clean suffix NULs
rawKeyData = bytes.TrimRight(rawKeyData, "\x00")
d.decodedKey, err = DecryptKey(rawKeyData)
if err != nil {
return err
}
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return nil
}
func (d *Decoder) readRawMetaQTag() error {
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// get raw meta data len
if _, err := d.r.Seek(-8, io.SeekEnd); err != nil {
return err
}
buf, err := io.ReadAll(io.LimitReader(d.r, 4))
if err != nil {
return err
}
rawMetaLen := int64(binary.BigEndian.Uint32(buf))
// read raw meta data
audioLen, err := d.r.Seek(-(8 + rawMetaLen), io.SeekEnd)
if err != nil {
return err
}
d.audioLen = int(audioLen)
rawMetaData, err := io.ReadAll(io.LimitReader(d.r, rawMetaLen))
if err != nil {
return err
}
items := strings.Split(string(rawMetaData), ",")
if len(items) != 3 {
return errors.New("invalid raw meta data")
}
d.decodedKey, err = DecryptKey([]byte(items[0]))
if err != nil {
return err
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}
d.rawMetaExtra1, err = strconv.Atoi(items[1])
if err != nil {
return err
}
d.rawMetaExtra2, err = strconv.Atoi(items[2])
if err != nil {
return err
}
return nil
}
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//goland:noinspection SpellCheckingInspection
func init() {
supportedExts := []string{
"qmc0", "qmc3", //QQ Music MP3
"qmc2", "qmc4", "qmc6", "qmc8", //QQ Music M4A
"qmcflac", //QQ Music FLAC
"qmcogg", //QQ Music OGG
"tkm", //QQ Music Accompaniment M4A
"bkcmp3", "bkcm4a", "bkcflac", "bkcwav", "bkcape", "bkcogg", "bkcwma", //Moo Music
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"666c6163", //QQ Music Weiyun Flac
"6d7033", //QQ Music Weiyun Mp3
"6f6767", //QQ Music Weiyun Ogg
"6d3461", //QQ Music Weiyun M4a
"776176", //QQ Music Weiyun Wav
"mgg", "mgg1", "mggl", //QQ Music New Ogg
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"mflac", "mflac0", //QQ Music New Flac
}
for _, ext := range supportedExts {
common.RegisterDecoder(ext, false, newCompactDecoder)
}
}
type compactDecoder struct {
decoder *Decoder
createErr error
buf *bytes.Buffer
}
func newCompactDecoder(p []byte) common.Decoder {
r := bytes.NewReader(p)
d, err := NewDecoder(r)
c := compactDecoder{
decoder: d,
createErr: err,
}
return &c
}
func (c *compactDecoder) Validate() error {
if c.createErr != nil {
return c.createErr
}
return c.decoder.Validate()
}
func (c *compactDecoder) Decode() error {
if c.createErr != nil {
return c.createErr
}
c.buf = bytes.NewBuffer(nil)
_, err := io.Copy(c.buf, c.decoder)
return err
}
func (c *compactDecoder) GetCoverImage() []byte {
return nil
}
func (c *compactDecoder) GetAudioData() []byte {
return c.buf.Bytes()
}
func (c *compactDecoder) GetAudioExt() string {
if c.createErr != nil {
return ""
}
return c.decoder.GetFileExt()
}
func (c *compactDecoder) GetMeta() common.Meta {
return nil
}