feat(QMCv2): Add mapCipher & mflac/mgg key discovery

algo/qmc/cipher.go

@@ -0,0 +1,5 @@
+package qmc
+
+type streamCipher interface {
+	Decrypt(buf []byte, offset int)
+}

algo/qmc/cipher_map.go

@@ -0,0 +1,39 @@
+package qmc
+
+import "errors"
+
+type mapCipher struct {
+	key  []byte
+	box  []byte
+	size int
+}
+
+func NewMapCipher(key []byte) (*mapCipher, error) {
+	if len(key) == 0 {
+		return nil, errors.New("qmc/cipher_map: invalid key size")
+	}
+	c := &mapCipher{key: key, size: len(key)}
+	c.box = make([]byte, c.size)
+	return c, nil
+}
+
+func (c *mapCipher) getMask(offset int) byte {
+	if offset > 0x7FFF {
+		offset %= 0x7FFF
+	}
+	idx := (offset*offset + 71214) % c.size
+	return c.rotate(c.key[idx], byte(idx)&0x7)
+}
+
+func (c *mapCipher) rotate(value byte, bits byte) byte {
+	rotate := (bits + 4) % 8
+	left := value << rotate
+	right := value >> rotate
+	return left | right
+}
+
+func (c *mapCipher) Decrypt(buf []byte, offset int) {
+	for i := 0; i < len(buf); i++ {
+		buf[i] ^= c.getMask(offset + i)
+	}
+}

algo/qmc/cipher_map_test.go

@@ -0,0 +1,40 @@
+package qmc
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func loadTestMapCipherData() ([]byte, []byte, []byte, error) {
+	key, err := os.ReadFile("./testdata/mflac_map_key.bin")
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	raw, err := os.ReadFile("./testdata/mflac_map_raw.bin")
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	target, err := os.ReadFile("./testdata/mflac_map_target.bin")
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	return key, raw, target, nil
+}
+func Test_mapCipher_Decrypt(t *testing.T) {
+	key, raw, target, err := loadTestMapCipherData()
+	if err != nil {
+		t.Fatalf("load testing data failed: %s", err)
+	}
+	t.Run("overall", func(t *testing.T) {
+		c, err := NewMapCipher(key)
+		if err != nil {
+			t.Errorf("init mapCipher failed: %s", err)
+			return
+		}
+		c.Decrypt(raw, 0)
+		if !reflect.DeepEqual(raw, target) {
+			t.Error("overall")
+		}
+	})
+}

algo/qmc/cipher_rc4.go

@@ -17,7 +17,7 @@ type rc4Cipher struct {
 func NewRC4Cipher(key []byte) (*rc4Cipher, error) {
 	n := len(key)
 	if n == 0 {
-		return nil, errors.New("crypto/rc4: invalid key size")
+		return nil, errors.New("qmc/cipher_rc4: invalid key size")
 	}
 
 	var c = rc4Cipher{key: key}
@@ -54,7 +54,7 @@ func (c *rc4Cipher) getHashBase() {
 
 const rc4SegmentSize = 5120
 
-func (c *rc4Cipher) Process(src []byte, offset int) {
+func (c *rc4Cipher) Decrypt(src []byte, offset int) {
 	toProcess := len(src)
 	processed := 0
 	markProcess := func(p int) (finished bool) {

algo/qmc/cipher_rc4_test.go

@@ -0,0 +1,90 @@
+package qmc
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func loadTestRC4CipherData() ([]byte, []byte, []byte, error) {
+	key, err := os.ReadFile("./testdata/mflac0_rc4_key.bin")
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	raw, err := os.ReadFile("./testdata/mflac0_rc4_raw.bin")
+	if err != nil {
+		return nil, nil, nil, err
+	}
+	target, err := os.ReadFile("./testdata/mflac0_rc4_target.bin")
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	return key, raw, target, nil
+}
+func Test_rc4Cipher_Decrypt(t *testing.T) {
+	key, raw, target, err := loadTestRC4CipherData()
+	if err != nil {
+		t.Fatalf("load testing data failed: %s", err)
+	}
+	t.Run("overall", func(t *testing.T) {
+		c, err := NewRC4Cipher(key)
+		if err != nil {
+			t.Errorf("init rc4Cipher failed: %s", err)
+			return
+		}
+		c.Decrypt(raw, 0)
+		if !reflect.DeepEqual(raw, target) {
+			t.Error("overall")
+		}
+	})
+
+}
+
+func Test_rc4Cipher_encFirstSegment(t *testing.T) {
+	key, raw, target, err := loadTestRC4CipherData()
+	if err != nil {
+		t.Fatalf("load testing data failed: %s", err)
+	}
+	t.Run("first-block(0~128)", func(t *testing.T) {
+		c, err := NewRC4Cipher(key)
+		if err != nil {
+			t.Errorf("init rc4Cipher failed: %s", err)
+			return
+		}
+		c.Decrypt(raw[:128], 0)
+		if !reflect.DeepEqual(raw[:128], target[:128]) {
+			t.Error("first-block(0~128)")
+		}
+	})
+}
+
+func Test_rc4Cipher_encASegment(t *testing.T) {
+	key, raw, target, err := loadTestRC4CipherData()
+	if err != nil {
+		t.Fatalf("load testing data failed: %s", err)
+	}
+
+	t.Run("align-block(128~5120)", func(t *testing.T) {
+		c, err := NewRC4Cipher(key)
+		if err != nil {
+			t.Errorf("init rc4Cipher failed: %s", err)
+			return
+		}
+		c.Decrypt(raw[128:5120], 128)
+		if !reflect.DeepEqual(raw[128:5120], target[128:5120]) {
+			t.Error("align-block(128~5120)")
+		}
+	})
+	t.Run("simple-block(5120~10240)", func(t *testing.T) {
+		c, err := NewRC4Cipher(key)
+		if err != nil {
+			t.Errorf("init rc4Cipher failed: %s", err)
+			return
+		}
+		c.Decrypt(raw[5120:10240], 5120)
+		if !reflect.DeepEqual(raw[5120:10240], target[5120:10240]) {
+			t.Error("align-block(128~5120)")
+		}
+	})
+}

algo/qmc/key_dec.go

@@ -18,10 +18,14 @@ func simpleMakeKey(salt byte, length int) []byte {
 }
 func DecryptKey(rawKey []byte) ([]byte, error) {
 	rawKeyDec := make([]byte, base64.StdEncoding.DecodedLen(len(rawKey)))
-	_, err := base64.StdEncoding.Decode(rawKeyDec, rawKey)
+	n, err := base64.StdEncoding.Decode(rawKeyDec, rawKey)
 	if err != nil {
 		return nil, err
 	}
+	if n < 16 {
+		return nil, errors.New("key length is too short")
+	}
+	rawKeyDec = rawKeyDec[:n]
 
 	simpleKey := simpleMakeKey(106, 8)
 	teaKey := make([]byte, 16)

algo/qmc/key_dec_test.go

@@ -1,6 +1,7 @@
 package qmc
 
 import (
+	"fmt"
 	"os"
 	"reflect"
 	"testing"
@@ -14,38 +15,41 @@ func TestSimpleMakeKey(t *testing.T) {
 		}
 	})
 }
-
+func loadDecryptKeyData(name string) ([]byte, []byte, error) {
+	keyRaw, err := os.ReadFile(fmt.Sprintf("./testdata/%s_key_raw.bin", name))
+	if err != nil {
+		return nil, nil, err
+	}
+	keyDec, err := os.ReadFile(fmt.Sprintf("./testdata/%s_key.bin", name))
+	if err != nil {
+		return nil, nil, err
+	}
+	return keyRaw, keyDec, nil
+}
 func TestDecryptKey(t *testing.T) {
-	rc4Raw, err := os.ReadFile("./testdata/rc4_key_raw.bin")
-	if err != nil {
-		t.Error(err)
-	}
-	rc4Dec, err := os.ReadFile("./testdata/rc4_key.bin")
-	if err != nil {
-		t.Error(err)
-	}
+
 	tests := []struct {
-		name    string
-		rawKey  []byte
-		want    []byte
-		wantErr bool
+		name     string
+		filename string
+		wantErr  bool
 	}{
-		{
-			"512",
-			rc4Raw,
-			rc4Dec,
-			false,
-		},
+		{"mflac0_rc4(512)", "mflac0_rc4", false},
+		{"mflac_map(256)", "mflac_map", false},
 	}
 	for _, tt := range tests {
+		raw, want, err := loadDecryptKeyData(tt.filename)
+		if err != nil {
+			t.Fatalf("load test data failed: %s", err)
+		}
 		t.Run(tt.name, func(t *testing.T) {
-			got, err := DecryptKey(tt.rawKey)
+			got, err := DecryptKey(raw)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("DecryptKey() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
-			if !reflect.DeepEqual(got, tt.want) {
-				t.Errorf("DecryptKey() got = %v..., want %v...", string(got[:32]), string(tt.want[:32]))
+			if !reflect.DeepEqual(got, want) {
+				t.Errorf("DecryptKey() got = %v..., want %v...",
+					string(got[:32]), string(want[:32]))
 			}
 		})
 	}

algo/qmc/qmc_512.go

@@ -13,7 +13,7 @@ type Mflac0Decoder struct {
 
 	audioLen   int
 	decodedKey []byte
-	rc4        *rc4Cipher
+	cipher     streamCipher
 	offset     int
 
 	rawMetaExtra1 int
@@ -21,6 +21,14 @@ type Mflac0Decoder struct {
 }
 
 func (d *Mflac0Decoder) Read(p []byte) (int, error) {
+	if d.cipher != nil {
+		return d.readRC4(p)
+	} else {
+		panic("not impl")
+		//return d.readPlain(p)
+	}
+}
+func (d *Mflac0Decoder) readRC4(p []byte) (int, error) {
 	n := len(p)
 	if d.audioLen-d.offset <= 0 {
 		return 0, io.EOF
@@ -32,32 +40,37 @@ func (d *Mflac0Decoder) Read(p []byte) (int, error) {
 		return 0, err
 	}
 
-	d.rc4.Process(p[:m], d.offset)
+	d.cipher.Decrypt(p[:m], d.offset)
 	d.offset += m
 	return m, err
-
 }
 
 func NewMflac0Decoder(r io.ReadSeeker) (*Mflac0Decoder, error) {
 	d := &Mflac0Decoder{r: r}
-	if err := d.searchKey(); err != nil {
+	err := d.searchKey()
+	if err != nil {
 		return nil, err
 	}
 
-	if len(d.decodedKey) > 300 {
-		var err error
-		d.rc4, err = NewRC4Cipher(d.decodedKey)
+	if len(d.decodedKey) == 0 {
+		return nil, errors.New("invalid decoded key")
+	} else if len(d.decodedKey) > 300 {
+		d.cipher, err = NewRC4Cipher(d.decodedKey)
 		if err != nil {
 			return nil, err
 		}
 	} else {
-		panic("not implement") //todo: impl
+		d.cipher, err = NewMapCipher(d.decodedKey)
+		if err != nil {
+			return nil, err
+		}
 	}
 
-	_, err := d.r.Seek(0, io.SeekStart)
+	_, err = d.r.Seek(0, io.SeekStart)
 	if err != nil {
 		return nil, err
 	}
+
 	return d, nil
 }
 
@@ -73,7 +86,35 @@ func (d *Mflac0Decoder) searchKey() error {
 		if err := d.readRawMetaQTag(); err != nil {
 			return err
 		}
-	} // todo: ...
+	} else {
+		size := binary.LittleEndian.Uint32(buf)
+		if size < 0x300 {
+			return d.readRawKey(int64(size))
+		} else {
+			// todo: try to use fixed key
+			panic("not impl")
+		}
+	}
+	return nil
+}
+
+func (d *Mflac0Decoder) 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
+	}
+
+	d.decodedKey, err = DecryptKey(rawKeyData)
+	if err != nil {
+		return err
+	}
+
 	return nil
 }
 
@@ -104,12 +145,9 @@ func (d *Mflac0Decoder) readRawMetaQTag() error {
 		return errors.New("invalid raw meta data")
 	}
 
-	{
-
-		d.decodedKey, err = DecryptKey([]byte(items[0]))
-		if err != nil {
-			return err
-		}
+	d.decodedKey, err = DecryptKey([]byte(items[0]))
+	if err != nil {
+		return err
 	}
 
 	d.rawMetaExtra1, err = strconv.Atoi(items[1])

algo/qmc/qmc_512_test.go

@@ -2,23 +2,24 @@ package qmc
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"os"
 	"reflect"
 	"testing"
 )
 
-func loadTestDataRC4Mflac0() ([]byte, []byte, error) {
-	encBody, err := os.ReadFile("./testdata/rc4_raw.bin")
+func loadTestDataQmcDecoder(filename string) ([]byte, []byte, error) {
+	encBody, err := os.ReadFile(fmt.Sprintf("./testdata/%s_raw.bin", filename))
 	if err != nil {
 		return nil, nil, err
 	}
-	encSuffix, err := os.ReadFile("./testdata/rc4_suffix_mflac0.bin")
+	encSuffix, err := os.ReadFile(fmt.Sprintf("./testdata/%s_suffix.bin", filename))
 	if err != nil {
 		return nil, nil, err
 	}
 
-	target, err := os.ReadFile("./testdata/rc4_target.bin")
+	target, err := os.ReadFile(fmt.Sprintf("./testdata/%s_target.bin", filename))
 	if err != nil {
 		return nil, nil, err
 	}
@@ -26,23 +27,35 @@ func loadTestDataRC4Mflac0() ([]byte, []byte, error) {
 
 }
 func TestMflac0Decoder_Read(t *testing.T) {
-	raw, target, err := loadTestDataRC4Mflac0()
-	if err != nil {
-		t.Fatal(err)
+	tests := []struct {
+		name     string
+		filename string
+		wantErr  bool
+	}{
+		{"mflac0_rc4(512)", "mflac0_rc4", false},
+		{"mflac_map(256)", "mflac_map", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			raw, target, err := loadTestDataQmcDecoder(tt.filename)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			d, err := NewMflac0Decoder(bytes.NewReader(raw))
+			if err != nil {
+				t.Error(err)
+			}
+			buf := make([]byte, len(target))
+			if _, err := io.ReadFull(d, buf); err != nil {
+				t.Errorf("read bytes from decoder error = %v", err)
+				return
+			}
+			if !reflect.DeepEqual(buf, target) {
+				t.Errorf("Decrypt() got = %v, want %v", buf[:32], target[:32])
+			}
+		})
 	}
 
-	t.Run("mflac0-file", func(t *testing.T) {
-		d, err := NewMflac0Decoder(bytes.NewReader(raw))
-		if err != nil {
-			t.Error(err)
-		}
-		buf := make([]byte, len(target))
-		if _, err := io.ReadFull(d, buf); err != nil {
-			t.Errorf("read bytes from decoder error = %v", err)
-			return
-		}
-		if !reflect.DeepEqual(buf, target) {
-			t.Errorf("Process() got = %v, want %v", buf[:32], target[:32])
-		}
-	})
 }

algo/qmc/rc4_test.go

@@ -1,72 +0,0 @@
-package qmc
-
-import (
-	"os"
-	"reflect"
-	"testing"
-)
-
-func loadTestData() (*rc4Cipher, []byte, []byte, error) {
-	key, err := os.ReadFile("./testdata/rc4_key.bin")
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	raw, err := os.ReadFile("./testdata/rc4_raw.bin")
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	target, err := os.ReadFile("./testdata/rc4_target.bin")
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	c, err := NewRC4Cipher(key)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	return c, raw, target, nil
-}
-func Test_rc4Cipher_Process(t *testing.T) {
-	c, raw, target, err := loadTestData()
-	if err != nil {
-		t.Errorf("load testing data failed: %s", err)
-	}
-	t.Run("overall", func(t *testing.T) {
-		c.Process(raw, 0)
-		if !reflect.DeepEqual(raw, target) {
-			t.Error("overall")
-		}
-	})
-
-}
-
-func Test_rc4Cipher_encFirstSegment(t *testing.T) {
-	c, raw, target, err := loadTestData()
-	if err != nil {
-		t.Errorf("load testing data failed: %s", err)
-	}
-	t.Run("first-block(0~128)", func(t *testing.T) {
-		c.Process(raw[:128], 0)
-		if !reflect.DeepEqual(raw[:128], target[:128]) {
-			t.Error("first-block(0~128)")
-		}
-	})
-}
-
-func Test_rc4Cipher_encASegment(t *testing.T) {
-	c, raw, target, err := loadTestData()
-	if err != nil {
-		t.Errorf("load testing data failed: %s", err)
-	}
-	t.Run("align-block(128~5120)", func(t *testing.T) {
-		c.Process(raw[128:5120], 128)
-		if !reflect.DeepEqual(raw[128:5120], target[128:5120]) {
-			t.Error("align-block(128~5120)")
-		}
-	})
-	t.Run("simple-block(5120~10240)", func(t *testing.T) {
-		c.Process(raw[5120:10240], 5120)
-		if !reflect.DeepEqual(raw[5120:10240], target[5120:10240]) {
-			t.Error("align-block(128~5120)")
-		}
-	})
-}