init: dec-music 项目初始化

decrypt/qmc/qmc.go

@@ -0,0 +1,198 @@
+package qmc
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"runtime"
+	"strings"
+
+	"jsuse.com/dev/dec-music/decrypt"
+	"jsuse.com/dev/dec-music/internal/sniff"
+	"jsuse.com/dev/dec-music/log"
+)
+
+type decoder struct {
+	raw    io.ReadSeeker
+	params *decrypt.DecoderParams
+
+	audio    io.Reader
+	audioLen int
+	offset   int
+
+	decodedKey []byte
+	cipher     decrypt.StreamDecoder
+
+	logger *log.Logger
+}
+
+func newDecoder(p *decrypt.DecoderParams) decrypt.Decoder {
+	return &decoder{raw: p.Reader, params: p, logger: p.Logger}
+}
+
+func (d *decoder) Read(p []byte) (int, error) {
+	n, err := d.audio.Read(p)
+	if n > 0 {
+		d.cipher.Decrypt(p[:n], d.offset)
+		d.offset += n
+	}
+	return n, err
+}
+
+func (d *decoder) Validate() error {
+	if err := d.searchKey(); err != nil {
+		return err
+	}
+
+	var err error
+	if len(d.decodedKey) > 300 {
+		d.cipher, err = newRC4Cipher(d.decodedKey)
+	} else if len(d.decodedKey) != 0 {
+		d.cipher, err = newMapCipher(d.decodedKey)
+	} else {
+		d.cipher = newStaticCipher()
+	}
+	if err != nil {
+		return err
+	}
+
+	if err := d.validateDecode(); err != nil {
+		return err
+	}
+
+	if _, err := d.raw.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+	d.audio = io.LimitReader(d.raw, int64(d.audioLen))
+	return nil
+}
+
+func (d *decoder) validateDecode() error {
+	if _, err := d.raw.Seek(0, io.SeekStart); err != nil {
+		return fmt.Errorf("qmc seek to start: %w", err)
+	}
+
+	buf := make([]byte, 64)
+	if _, err := io.ReadFull(d.raw, buf); err != nil {
+		return fmt.Errorf("qmc read header: %w", err)
+	}
+
+	d.cipher.Decrypt(buf, 0)
+	if _, ok := sniff.AudioExtension(buf); !ok {
+		return errors.New("qmc: detect file type failed")
+	}
+	return nil
+}
+
+func (d *decoder) searchKey() (err error) {
+	fileSizeM4, err := d.raw.Seek(-4, io.SeekEnd)
+	if err != nil {
+		return err
+	}
+	fileSize := int(fileSizeM4) + 4
+
+	if runtime.GOOS == "darwin" && !strings.HasPrefix(d.params.Extension, ".qmc") {
+		d.decodedKey, err = readKeyFromMMKV(d.params.FilePath, d.logger)
+		if err == nil {
+			d.audioLen = fileSize
+			return nil
+		}
+		if d.logger != nil {
+			d.logger.Warn("read key from mmkv failed:", err)
+		}
+	}
+
+	suffixBuf := make([]byte, 4)
+	if _, err := io.ReadFull(d.raw, suffixBuf); err != nil {
+		return err
+	}
+
+	switch string(suffixBuf) {
+	case "QTag":
+		return d.readRawMetaQTag()
+	case "STag":
+		return errors.New("qmc: file with 'STag' suffix doesn't contains media key")
+	case "cex\x00":
+		footer, err := newMusicExTag(d.raw)
+		if err != nil {
+			return err
+		}
+		d.audioLen = fileSize - int(footer.tagSize)
+		d.decodedKey, err = readKeyFromMMKVCustom(footer.mediaFileName)
+		return err
+	default:
+		size := binary.LittleEndian.Uint32(suffixBuf)
+		if size <= 0xFFFF && size != 0 {
+			return d.readRawKey(int64(size))
+		}
+		d.audioLen = fileSize
+		return nil
+	}
+}
+
+func (d *decoder) readRawKey(rawKeyLen int64) error {
+	audioLen, err := d.raw.Seek(-(4 + rawKeyLen), io.SeekEnd)
+	if err != nil {
+		return err
+	}
+	d.audioLen = int(audioLen)
+
+	rawKeyData, err := io.ReadAll(io.LimitReader(d.raw, rawKeyLen))
+	if err != nil {
+		return err
+	}
+	rawKeyData = bytes.TrimRight(rawKeyData, "\x00")
+
+	d.decodedKey, err = deriveKey(rawKeyData)
+	return err
+}
+
+func (d *decoder) readRawMetaQTag() error {
+	if _, err := d.raw.Seek(-8, io.SeekEnd); err != nil {
+		return err
+	}
+	buf, err := io.ReadAll(io.LimitReader(d.raw, 4))
+	if err != nil {
+		return err
+	}
+	rawMetaLen := int64(binary.BigEndian.Uint32(buf))
+
+	audioLen, err := d.raw.Seek(-(8 + rawMetaLen), io.SeekEnd)
+	if err != nil {
+		return err
+	}
+	d.audioLen = int(audioLen)
+	rawMetaData, err := io.ReadAll(io.LimitReader(d.raw, 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 = deriveKey([]byte(items[0]))
+	return err
+}
+
+func init() {
+	supportedExts := []string{
+		"qmc0", "qmc3", "qmc2", "qmc4", "qmc6", "qmc8",
+		"qmcflac", "qmcogg", "tkm",
+		"bkcmp3", "bkcm4a", "bkcflac", "bkcwav", "bkcape", "bkcogg", "bkcwma",
+		"666c6163", "6d7033", "6f6767", "6d3461", "776176", "mmp4",
+	}
+	for _, ext := range supportedExts {
+		decrypt.RegisterDecoder(ext, false , newDecoder)
+	}
+
+	for _, ext := range []string{"mgg", "mflac"} {
+		decrypt.RegisterDecoder(ext, false , newDecoder)
+		for _, suffix := range []string{"0", "1", "a", "h", "l"} {
+			decrypt.RegisterDecoder(ext+suffix, false , newDecoder)
+		}
+	}
+}