97 lines
2.0 KiB
Go
97 lines
2.0 KiB
Go
package qmc
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import (
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"encoding/base64"
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"encoding/binary"
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"errors"
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"github.com/umlock-music/cli/algo/common"
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)
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var (
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ErrQmcFileLength = errors.New("invalid qmc file length")
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ErrQmcKeyDecodeFailed = errors.New("base64 decode qmc key failed")
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ErrQmcKeyLength = errors.New("unexpected decoded qmc key length")
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)
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type Decoder struct {
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file []byte
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maskDetector func(encodedData []byte) (*Key256Mask, error)
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mask *Key256Mask
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audioExt string
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key []byte
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audio []byte
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}
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func NewDefaultDecoder(data []byte) *Decoder {
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return &Decoder{file: data, mask: getDefaultMask()}
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}
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func NewMflac256Decoder(data []byte) *Decoder {
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return &Decoder{file: data, maskDetector: detectMflac256Mask, audioExt: "flac"}
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}
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func NewMgg256Decoder(data []byte) *Decoder {
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return &Decoder{file: data, maskDetector: detectMgg256Mask, audioExt: "ogg"}
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}
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func (d *Decoder) Validate() error {
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if nil != d.mask {
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return nil
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}
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if nil != d.maskDetector {
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if err := d.validateKey(); err != nil {
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return err
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}
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var err error
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d.mask, err = d.maskDetector(d.file)
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return err
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}
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return errors.New("no mask or mask detector found")
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}
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func (d *Decoder) validateKey() error {
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lenData := len(d.file)
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if lenData < 4 {
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return ErrQmcFileLength
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}
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keyLen := binary.LittleEndian.Uint32(d.file[lenData-4:])
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if lenData < int(keyLen+4) {
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return ErrQmcFileLength
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}
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var err error
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d.key, err = base64.StdEncoding.DecodeString(
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string(d.file[lenData-4-int(keyLen) : lenData-4]))
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if err != nil {
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return ErrQmcKeyDecodeFailed
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}
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if len(d.key) != 272 {
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return ErrQmcKeyLength
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}
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d.file = d.file[:lenData-4-int(keyLen)]
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return nil
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}
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func (d *Decoder) Decode() error {
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d.audio = d.mask.Decrypt(d.file)
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return nil
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}
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func (d Decoder) GetCoverImage() []byte {
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return nil
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}
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func (d Decoder) GetAudioData() []byte {
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return d.audio
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}
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func (d Decoder) GetAudioExt() string {
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return d.audioExt
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}
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func (d Decoder) GetMeta() common.Meta {
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return nil
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}
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