refactor: use kgm crypto from parakeet-rs

chore: update deps

algo/kgm/kgm.go

@@ -2,27 +2,24 @@ package kgm
 
 import (
 	"bytes"
-	"encoding/binary"
-	"errors"
+	"fmt"
+	"io"
 
 	"github.com/unlock-music/cli/algo/common"
 )
 
-var (
-	vprHeader = []byte{
-		0x05, 0x28, 0xBC, 0x96, 0xE9, 0xE4, 0x5A, 0x43,
-		0x91, 0xAA, 0xBD, 0xD0, 0x7A, 0xF5, 0x36, 0x31}
-	kgmHeader = []byte{
-		0x7C, 0xD5, 0x32, 0xEB, 0x86, 0x02, 0x7F, 0x4B,
-		0xA8, 0xAF, 0xA6, 0x8E, 0x0F, 0xFF, 0x99, 0x14}
-	ErrKgmMagicHeader = errors.New("kgm/vpr magic header not matched")
-)
-
 type Decoder struct {
-	file     []byte
-	key      []byte
-	maskFunc func(int) byte
-	audio    []byte
+	header      Header
+	initializer kgmCryptoInitializer
+
+	file  []byte
+	audio []byte
+}
+
+type kgmCryptoInitializer func(header *Header, body io.Reader) (io.Reader, error)
+
+var kgmCryptoInitializers = map[uint32]kgmCryptoInitializer{
+	3: newKgmCryptoV3,
 }
 
 func NewDecoder(file []byte) common.Decoder {
@@ -44,31 +41,34 @@ func (d *Decoder) GetMeta() common.Meta {
 }
 
 func (d *Decoder) Validate() error {
-	if bytes.Equal(kgmHeader, d.file[:len(kgmHeader)]) {
-		d.maskFunc = getKgmMask
-	} else if bytes.Equal(vprHeader, d.file[:len(vprHeader)]) {
-		d.maskFunc = getVprMask
-	} else {
-		return ErrKgmMagicHeader
+	if err := d.header.FromBytes(d.file); err != nil {
+		return err
+	}
+	// TODO; validate crypto version
+
+	var ok bool
+	d.initializer, ok = kgmCryptoInitializers[d.header.CryptoVersion]
+	if !ok {
+		return fmt.Errorf("kgm: unsupported crypto version %d", d.header.CryptoVersion)
 	}
 
-	d.key = d.file[0x1c:0x2c]
-	d.key = append(d.key, 0x00)
-	_ = d.file[0x2c:0x3c] //todo: key2
 	return nil
 }
 
 func (d *Decoder) Decode() error {
-	headerLen := binary.LittleEndian.Uint32(d.file[0x10:0x14])
-	d.audio = d.file[headerLen:]
+	d.audio = d.file[d.header.AudioOffset:]
 
-	for i := 0; i < len(d.audio); i++ {
-		med8 := d.audio[i] ^ d.key[i%17] ^ d.maskFunc(i)
-		d.audio[i] = med8 ^ (med8&0xf)<<4
+	r, err := d.initializer(&d.header, bytes.NewReader(d.audio))
+	if err != nil {
+		return fmt.Errorf("kgm: failed to initialize crypto: %w", err)
+	}
+	d.audio, err = io.ReadAll(r)
+	if err != nil {
+		return fmt.Errorf("kgm: failed to decrypt audio: %w", err)
 	}
-
 	return nil
 }
+
 func init() {
 	// Kugou
 	common.RegisterDecoder("kgm", false, NewDecoder)