feat(QMCv2): support static cipher (legacy)

algo/qmc/cipher_static.go

@@ -0,0 +1,57 @@
+package qmc
+
+func NewStaticCipher() *staticCipher {
+	return &defaultStaticCipher
+}
+
+var defaultStaticCipher = staticCipher{}
+
+type staticCipher struct{}
+
+func (c *staticCipher) Decrypt(buf []byte, offset int) {
+	for i := 0; i < len(buf); i++ {
+		buf[i] ^= c.getMask(offset + i)
+	}
+}
+func (c *staticCipher) getMask(offset int) byte {
+	if offset > 0x7FFF {
+		offset %= 0x7FFF
+	}
+	idx := (offset*offset + 27) & 0xff
+	return staticCipherBox[idx]
+}
+
+var staticCipherBox = [...]byte{
+	0x77, 0x48, 0x32, 0x73, 0xDE, 0xF2, 0xC0, 0xC8, //0x00
+	0x95, 0xEC, 0x30, 0xB2, 0x51, 0xC3, 0xE1, 0xA0, //0x08
+	0x9E, 0xE6, 0x9D, 0xCF, 0xFA, 0x7F, 0x14, 0xD1, //0x10
+	0xCE, 0xB8, 0xDC, 0xC3, 0x4A, 0x67, 0x93, 0xD6, //0x18
+	0x28, 0xC2, 0x91, 0x70, 0xCA, 0x8D, 0xA2, 0xA4, //0x20
+	0xF0, 0x08, 0x61, 0x90, 0x7E, 0x6F, 0xA2, 0xE0, //0x28
+	0xEB, 0xAE, 0x3E, 0xB6, 0x67, 0xC7, 0x92, 0xF4, //0x30
+	0x91, 0xB5, 0xF6, 0x6C, 0x5E, 0x84, 0x40, 0xF7, //0x38
+	0xF3, 0x1B, 0x02, 0x7F, 0xD5, 0xAB, 0x41, 0x89, //0x40
+	0x28, 0xF4, 0x25, 0xCC, 0x52, 0x11, 0xAD, 0x43, //0x48
+	0x68, 0xA6, 0x41, 0x8B, 0x84, 0xB5, 0xFF, 0x2C, //0x50
+	0x92, 0x4A, 0x26, 0xD8, 0x47, 0x6A, 0x7C, 0x95, //0x58
+	0x61, 0xCC, 0xE6, 0xCB, 0xBB, 0x3F, 0x47, 0x58, //0x60
+	0x89, 0x75, 0xC3, 0x75, 0xA1, 0xD9, 0xAF, 0xCC, //0x68
+	0x08, 0x73, 0x17, 0xDC, 0xAA, 0x9A, 0xA2, 0x16, //0x70
+	0x41, 0xD8, 0xA2, 0x06, 0xC6, 0x8B, 0xFC, 0x66, //0x78
+	0x34, 0x9F, 0xCF, 0x18, 0x23, 0xA0, 0x0A, 0x74, //0x80
+	0xE7, 0x2B, 0x27, 0x70, 0x92, 0xE9, 0xAF, 0x37, //0x88
+	0xE6, 0x8C, 0xA7, 0xBC, 0x62, 0x65, 0x9C, 0xC2, //0x90
+	0x08, 0xC9, 0x88, 0xB3, 0xF3, 0x43, 0xAC, 0x74, //0x98
+	0x2C, 0x0F, 0xD4, 0xAF, 0xA1, 0xC3, 0x01, 0x64, //0xA0
+	0x95, 0x4E, 0x48, 0x9F, 0xF4, 0x35, 0x78, 0x95, //0xA8
+	0x7A, 0x39, 0xD6, 0x6A, 0xA0, 0x6D, 0x40, 0xE8, //0xB0
+	0x4F, 0xA8, 0xEF, 0x11, 0x1D, 0xF3, 0x1B, 0x3F, //0xB8
+	0x3F, 0x07, 0xDD, 0x6F, 0x5B, 0x19, 0x30, 0x19, //0xC0
+	0xFB, 0xEF, 0x0E, 0x37, 0xF0, 0x0E, 0xCD, 0x16, //0xC8
+	0x49, 0xFE, 0x53, 0x47, 0x13, 0x1A, 0xBD, 0xA4, //0xD0
+	0xF1, 0x40, 0x19, 0x60, 0x0E, 0xED, 0x68, 0x09, //0xD8
+	0x06, 0x5F, 0x4D, 0xCF, 0x3D, 0x1A, 0xFE, 0x20, //0xE0
+	0x77, 0xE4, 0xD9, 0xDA, 0xF9, 0xA4, 0x2B, 0x76, //0xE8
+	0x1C, 0x71, 0xDB, 0x00, 0xBC, 0xFD, 0x0C, 0x6C, //0xF0
+	0xA5, 0x47, 0xF7, 0xF6, 0x00, 0x79, 0x4A, 0x11, //0xF8
+}

algo/qmc/old_qmc.go

@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"encoding/binary"
 	"errors"
+
 	"github.com/unlock-music/cli/algo/common"
 )
 
@@ -13,7 +14,7 @@ var (
 	ErrQmcKeyLength       = errors.New("unexpected decoded qmc key length")
 )
 
-type Decoder struct {
+type OldDecoder struct {
 	file         []byte
 	maskDetector func(encodedData []byte) (*Key256Mask, error)
 	mask         *Key256Mask
@@ -23,14 +24,14 @@ type Decoder struct {
 }
 
 func NewMflac256Decoder(data []byte) common.Decoder {
-	return &Decoder{file: data, maskDetector: detectMflac256Mask, audioExt: "flac"}
+	return &OldDecoder{file: data, maskDetector: detectMflac256Mask, audioExt: "flac"}
 }
 
 func NewMgg256Decoder(data []byte) common.Decoder {
-	return &Decoder{file: data, maskDetector: detectMgg256Mask, audioExt: "ogg"}
+	return &OldDecoder{file: data, maskDetector: detectMgg256Mask, audioExt: "ogg"}
 }
 
-func (d *Decoder) Validate() error {
+func (d *OldDecoder) Validate() error {
 	if nil != d.mask {
 		return nil
 	}
@@ -45,7 +46,7 @@ func (d *Decoder) Validate() error {
 	return errors.New("no mask or mask detector found")
 }
 
-func (d *Decoder) validateKey() error {
+func (d *OldDecoder) validateKey() error {
 	lenData := len(d.file)
 	if lenData < 4 {
 		return ErrQmcFileLength
@@ -70,33 +71,33 @@ func (d *Decoder) validateKey() error {
 
 }
 
-func (d *Decoder) Decode() error {
+func (d *OldDecoder) Decode() error {
 	d.audio = d.mask.Decrypt(d.file)
 	return nil
 }
 
-func (d Decoder) GetCoverImage() []byte {
+func (d OldDecoder) GetCoverImage() []byte {
 	return nil
 }
 
-func (d Decoder) GetAudioData() []byte {
+func (d OldDecoder) GetAudioData() []byte {
 	return d.audio
 }
 
-func (d Decoder) GetAudioExt() string {
+func (d OldDecoder) GetAudioExt() string {
 	if d.audioExt != "" {
 		return "." + d.audioExt
 	}
 	return ""
 }
 
-func (d Decoder) GetMeta() common.Meta {
+func (d OldDecoder) GetMeta() common.Meta {
 	return nil
 }
 
 func DecoderFuncWithExt(ext string) common.NewDecoderFunc {
 	return func(file []byte) common.Decoder {
-		return &Decoder{file: file, audioExt: ext, mask: getDefaultMask()}
+		return &OldDecoder{file: file, audioExt: ext, mask: getDefaultMask()}
 	}
 }
 

algo/qmc/qmc.go

@@ -6,10 +6,13 @@ import (
 	"io"
 	"strconv"
 	"strings"
+
+	"github.com/unlock-music/cli/algo/common"
 )
 
-type Mflac0Decoder struct {
+type Decoder struct {
 	r       io.ReadSeeker
+	fileExt string
 
 	audioLen   int
 	decodedKey []byte
@@ -20,15 +23,9 @@ type Mflac0Decoder struct {
 	rawMetaExtra2 int
 }
 
-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) {
+// 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) {
 	n := len(p)
 	if d.audioLen-d.offset <= 0 {
 		return 0, io.EOF
@@ -45,25 +42,25 @@ func (d *Mflac0Decoder) readRC4(p []byte) (int, error) {
 	return m, err
 }
 
-func NewMflac0Decoder(r io.ReadSeeker) (*Mflac0Decoder, error) {
-	d := &Mflac0Decoder{r: r}
+func NewDecoder(r io.ReadSeeker) (*Decoder, error) {
+	d := &Decoder{r: r}
 	err := d.searchKey()
 	if err != nil {
 		return nil, err
 	}
 
-	if len(d.decodedKey) == 0 {
-		return nil, errors.New("invalid decoded key")
-	} else if len(d.decodedKey) > 300 {
+	if len(d.decodedKey) > 300 {
 		d.cipher, err = NewRC4Cipher(d.decodedKey)
 		if err != nil {
 			return nil, err
 		}
-	} else {
+	} else if len(d.decodedKey) != 0 {
 		d.cipher, err = NewMapCipher(d.decodedKey)
 		if err != nil {
 			return nil, err
 		}
+	} else {
+		d.cipher = NewStaticCipher()
 	}
 
 	_, err = d.r.Seek(0, io.SeekStart)
@@ -74,8 +71,32 @@ func NewMflac0Decoder(r io.ReadSeeker) (*Mflac0Decoder, error) {
 	return d, nil
 }
 
-func (d *Mflac0Decoder) searchKey() error {
-	if _, err := d.r.Seek(-4, io.SeekEnd); err != 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 {
 		return err
 	}
 	buf, err := io.ReadAll(io.LimitReader(d.r, 4))
@@ -88,17 +109,18 @@ func (d *Mflac0Decoder) searchKey() error {
 		}
 	} else {
 		size := binary.LittleEndian.Uint32(buf)
-		if size < 0x300 {
+		if size < 0x300 && size != 0 {
 			return d.readRawKey(int64(size))
 		} else {
-			// todo: try to use fixed key
-			panic("not impl")
+			// try to use default static cipher
+			d.audioLen = int(fileSizeM4 + 4)
+			return nil
 		}
 	}
 	return nil
 }
 
-func (d *Mflac0Decoder) readRawKey(rawKeyLen int64) error {
+func (d *Decoder) readRawKey(rawKeyLen int64) error {
 	audioLen, err := d.r.Seek(-(4 + rawKeyLen), io.SeekEnd)
 	if err != nil {
 		return err
@@ -118,7 +140,7 @@ func (d *Mflac0Decoder) readRawKey(rawKeyLen int64) error {
 	return nil
 }
 
-func (d *Mflac0Decoder) readRawMetaQTag() error {
+func (d *Decoder) readRawMetaQTag() error {
 	// get raw meta data len
 	if _, err := d.r.Seek(-8, io.SeekEnd); err != nil {
 		return err

algo/qmc/qmc_test.go

@@ -29,23 +29,24 @@ func loadTestDataQmcDecoder(filename string) ([]byte, []byte, error) {
 func TestMflac0Decoder_Read(t *testing.T) {
 	tests := []struct {
 		name    string
-		filename string
 		wantErr bool
 	}{
-		{"mflac0_rc4(512)", "mflac0_rc4", false},
-		{"mflac_map(256)", "mflac_map", false},
+		{"mflac0_rc4", false},
+		{"mflac_map", false},
+		{"qmc0_static", false},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			raw, target, err := loadTestDataQmcDecoder(tt.filename)
+			raw, target, err := loadTestDataQmcDecoder(tt.name)
 			if err != nil {
 				t.Fatal(err)
 			}
 
-			d, err := NewMflac0Decoder(bytes.NewReader(raw))
+			d, err := NewDecoder(bytes.NewReader(raw))
 			if err != nil {
 				t.Error(err)
+				return
 			}
 			buf := make([]byte, len(target))
 			if _, err := io.ReadFull(d, buf); err != nil {
@@ -59,3 +60,37 @@ func TestMflac0Decoder_Read(t *testing.T) {
 	}
 
 }
+
+func TestMflac0Decoder_Validate(t *testing.T) {
+	tests := []struct {
+		name    string
+		fileExt string
+		wantErr bool
+	}{
+		{"mflac0_rc4", ".flac", false},
+		{"mflac_map", ".flac", false},
+		{"qmc0_static", ".mp3", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			raw, _, err := loadTestDataQmcDecoder(tt.name)
+			if err != nil {
+				t.Fatal(err)
+			}
+			d, err := NewDecoder(bytes.NewReader(raw))
+			if err != nil {
+				t.Error(err)
+				return
+			}
+
+			if err := d.Validate(); err != nil {
+				t.Errorf("read bytes from decoder error = %v", err)
+				return
+			}
+			if tt.fileExt != d.GetFileExt() {
+				t.Errorf("Decrypt() got = %v, want %v", d.GetFileExt(), tt.fileExt)
+			}
+		})
+	}
+}