algo/qmc/key_dec.go

@@ -0,0 +1,111 @@
+package qmc
+
+import (
+	"encoding/base64"
+	"errors"
+	"math"
+
+	"golang.org/x/crypto/tea"
+)
+
+func simpleMakeKey(salt byte, length int) []byte {
+	keyBuf := make([]byte, length)
+	for i := 0; i < length; i++ {
+		tmp := math.Tan(float64(salt) + float64(i)*0.1)
+		keyBuf[i] = byte(math.Abs(tmp) * 100.0)
+	}
+	return keyBuf
+}
+func DecryptKey(rawKey []byte) ([]byte, error) {
+	rawKeyDec := make([]byte, base64.StdEncoding.DecodedLen(len(rawKey)))
+	_, err := base64.StdEncoding.Decode(rawKeyDec, rawKey)
+	if err != nil {
+		return nil, err
+	}
+
+	simpleKey := simpleMakeKey(106, 8)
+	teaKey := make([]byte, 16)
+	for i := 0; i < 8; i++ {
+		teaKey[i<<1] = simpleKey[i]
+		teaKey[i<<1+1] = rawKeyDec[i]
+	}
+
+	rs, err := decryptTencentTea(rawKeyDec[8:], teaKey)
+	if err != nil {
+		return nil, err
+	}
+	return append(rawKeyDec[:8], rs...), nil
+}
+func decryptTencentTea(inBuf []byte, key []byte) ([]byte, error) {
+	const saltLen = 2
+	const zeroLen = 7
+	if len(inBuf)%8 != 0 {
+		return nil, errors.New("inBuf size not a multiple of the block size")
+	}
+	if len(inBuf) < 16 {
+		return nil, errors.New("inBuf size too small")
+	}
+
+	blk, err := tea.NewCipherWithRounds(key, 32)
+	if err != nil {
+		return nil, err
+	}
+
+	destBuf := make([]byte, 8)
+	blk.Decrypt(destBuf, inBuf)
+	padLen := int(destBuf[0] & 0x7)
+	outLen := len(inBuf) - 1 - padLen - saltLen - zeroLen
+	if padLen+saltLen != 8 {
+		return nil, errors.New("invalid pad len")
+	}
+	out := make([]byte, outLen)
+
+	ivPrev := make([]byte, 8)
+	ivCur := inBuf[:8]
+
+	inBufPos := 8
+
+	destIdx := 1 + padLen
+	cryptBlock := func() {
+		ivPrev = ivCur
+		ivCur = inBuf[inBufPos : inBufPos+8]
+
+		xor8Bytes(destBuf, destBuf, inBuf[inBufPos:inBufPos+8])
+		blk.Decrypt(destBuf, destBuf)
+
+		inBufPos += 8
+		destIdx = 0
+	}
+	for i := 1; i <= saltLen; {
+		if destIdx < 8 {
+			destIdx++
+			i++
+		} else if destIdx == 8 {
+			cryptBlock()
+		}
+	}
+
+	outPos := 0
+	for outPos < outLen {
+		if destIdx < 8 {
+			out[outPos] = destBuf[destIdx] ^ ivPrev[destIdx]
+			destIdx++
+			outPos++
+		} else if destIdx == 8 {
+			cryptBlock()
+		}
+	}
+
+	for i := 1; i <= zeroLen; i++ {
+		if destBuf[destIdx] != ivPrev[destIdx] {
+			return nil, errors.New("zero check failed")
+		}
+	}
+
+	return out, nil
+}
+func xor8Bytes(dst, a, b []byte) {
+	for i := 0; i < 8; i++ {
+		dst[i] = a[i] ^ b[i]
+	}
+}

algo/qmc/key_dec_test.go

@@ -0,0 +1,52 @@
+package qmc
+
+import (
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestSimpleMakeKey(t *testing.T) {
+	expect := []byte{0x69, 0x56, 0x46, 0x38, 0x2b, 0x20, 0x15, 0x0b}
+	t.Run("106,8", func(t *testing.T) {
+		if got := simpleMakeKey(106, 8); !reflect.DeepEqual(got, expect) {
+			t.Errorf("simpleMakeKey() = %v, want %v", got, expect)
+		}
+	})
+}
+
+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
+	}{
+		{
+			"512",
+			rc4Raw,
+			rc4Dec,
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := DecryptKey(tt.rawKey)
+			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]))
+			}
+		})
+	}
+}

algo/qmc/qmc_512.go

@@ -0,0 +1,125 @@
+package qmc
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+	"strconv"
+	"strings"
+)
+
+type Mflac0Decoder struct {
+	r io.ReadSeeker
+
+	audioLen   int
+	decodedKey []byte
+	rc4        *rc4Cipher
+	offset     int
+
+	rawMetaExtra1 int
+	rawMetaExtra2 int
+}
+
+func (d *Mflac0Decoder) Read(p []byte) (int, error) {
+	n := len(p)
+	if d.audioLen-d.offset <= 0 {
+		return 0, io.EOF
+	} else if d.audioLen-d.offset < n {
+		n = d.audioLen - d.offset
+	}
+	m, err := d.r.Read(p[:n])
+	if m == 0 {
+		return 0, err
+	}
+
+	d.rc4.Process(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 {
+		return nil, err
+	}
+
+	if len(d.decodedKey) > 300 {
+		var err error
+		d.rc4, err = NewRC4Cipher(d.decodedKey)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		panic("not implement") //todo: impl
+	}
+
+	_, err := d.r.Seek(0, io.SeekStart)
+	if err != nil {
+		return nil, err
+	}
+	return d, nil
+}
+
+func (d *Mflac0Decoder) searchKey() error {
+	if _, err := d.r.Seek(-4, io.SeekEnd); err != nil {
+		return err
+	}
+	buf, err := io.ReadAll(io.LimitReader(d.r, 4))
+	if err != nil {
+		return err
+	}
+	if string(buf) == "QTag" {
+		if err := d.readRawMetaQTag(); err != nil {
+			return err
+		}
+	} // todo: ...
+	return nil
+}
+
+func (d *Mflac0Decoder) readRawMetaQTag() error {
+	// get raw meta data len
+	if _, err := d.r.Seek(-8, io.SeekEnd); err != nil {
+		return err
+	}
+	buf, err := io.ReadAll(io.LimitReader(d.r, 4))
+	if err != nil {
+		return err
+	}
+	rawMetaLen := int64(binary.BigEndian.Uint32(buf))
+
+	// read raw meta data
+	audioLen, err := d.r.Seek(-(8 + rawMetaLen), io.SeekEnd)
+	if err != nil {
+		return err
+	}
+	d.audioLen = int(audioLen)
+	rawMetaData, err := io.ReadAll(io.LimitReader(d.r, 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 = DecryptKey([]byte(items[0]))
+		if err != nil {
+			return err
+		}
+	}
+
+	d.rawMetaExtra1, err = strconv.Atoi(items[1])
+	if err != nil {
+		return err
+	}
+	d.rawMetaExtra2, err = strconv.Atoi(items[2])
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

algo/qmc/qmc_512_test.go

@@ -0,0 +1,48 @@
+package qmc
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"reflect"
+	"testing"
+)
+
+func loadTestDataRC4Mflac0() ([]byte, []byte, error) {
+	encBody, err := os.ReadFile("./testdata/rc4_raw.bin")
+	if err != nil {
+		return nil, nil, err
+	}
+	encSuffix, err := os.ReadFile("./testdata/rc4_suffix_mflac0.bin")
+	if err != nil {
+		return nil, nil, err
+	}
+
+	target, err := os.ReadFile("./testdata/rc4_target.bin")
+	if err != nil {
+		return nil, nil, err
+	}
+	return bytes.Join([][]byte{encBody, encSuffix}, nil), target, nil
+
+}
+func TestMflac0Decoder_Read(t *testing.T) {
+	raw, target, err := loadTestDataRC4Mflac0()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	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.go

@@ -0,0 +1,133 @@
+package qmc
+
+import (
+	"errors"
+)
+
+// A rc4Cipher is an instance of RC4 using a particular key.
+type rc4Cipher struct {
+	box    []byte
+	key    []byte
+	hash   uint32
+	boxTmp []byte
+}
+
+// NewRC4Cipher creates and returns a new rc4Cipher. The key argument should be the
+// RC4 key, at least 1 byte and at most 256 bytes.
+func NewRC4Cipher(key []byte) (*rc4Cipher, error) {
+	n := len(key)
+	if n == 0 {
+		return nil, errors.New("crypto/rc4: invalid key size")
+	}
+
+	var c = rc4Cipher{key: key}
+	c.box = make([]byte, n)
+	c.boxTmp = make([]byte, n)
+
+	for i := 0; i < n; i++ {
+		c.box[i] = byte(i)
+	}
+
+	var j = 0
+	for i := 0; i < n; i++ {
+		j = (j + int(c.box[i]) + int(key[i%n])) % n
+		c.box[i], c.box[j] = c.box[j], c.box[i]
+	}
+	c.getHashBase()
+	return &c, nil
+}
+
+func (c *rc4Cipher) getHashBase() {
+	c.hash = 1
+	for i := 0; i < len(c.key); i++ {
+		v := uint32(c.key[i])
+		if v == 0 {
+			continue
+		}
+		nextHash := c.hash * v
+		if nextHash == 0 || nextHash <= c.hash {
+			break
+		}
+		c.hash = nextHash
+	}
+}
+
+const rc4SegmentSize = 5120
+
+func (c *rc4Cipher) Process(src []byte, offset int) {
+	toProcess := len(src)
+	processed := 0
+	markProcess := func(p int) (finished bool) {
+		offset += p
+		toProcess -= p
+		processed += p
+		return toProcess == 0
+	}
+
+	if offset < 128 {
+		blockSize := toProcess
+		if blockSize > 128-offset {
+			blockSize = 128 - offset
+		}
+		c.encFirstSegment(src[:blockSize], offset)
+		if markProcess(blockSize) {
+			return
+		}
+	}
+
+	if offset%rc4SegmentSize != 0 {
+		blockSize := toProcess
+		if blockSize > rc4SegmentSize-offset%rc4SegmentSize {
+			blockSize = rc4SegmentSize - offset%rc4SegmentSize
+		}
+		k := src[processed : processed+blockSize]
+		c.encASegment(k, offset)
+		if markProcess(blockSize) {
+			return
+		}
+	}
+	for toProcess > rc4SegmentSize {
+		c.encASegment(src[processed:processed+rc4SegmentSize], offset)
+		markProcess(rc4SegmentSize)
+	}
+
+	if toProcess > 0 {
+		c.encASegment(src[processed:], offset)
+	}
+}
+func (c *rc4Cipher) encFirstSegment(buf []byte, offset int) {
+	n := len(c.box)
+	for i := 0; i < len(buf); i++ {
+		idx1 := offset + i
+		segmentID := int(c.key[idx1%n])
+		idx2 := int(float64(c.hash) / float64((idx1+1)*segmentID) * 100.0)
+		buf[i] ^= c.key[idx2%n]
+	}
+}
+
+func (c *rc4Cipher) encASegment(buf []byte, offset int) {
+	n := len(c.box)
+	copy(c.boxTmp, c.box)
+
+	segmentID := (offset / rc4SegmentSize) & 0x1FF
+
+	if n <= segmentID {
+		return
+	}
+
+	idx2 := int64(float64(c.hash) /
+		float64((offset/rc4SegmentSize+1)*int(c.key[segmentID])) *
+		100.0)
+	skipLen := int((idx2 & 0x1FF) + int64(offset%rc4SegmentSize))
+
+	j, k := 0, 0
+
+	for i := -skipLen; i < len(buf); i++ {
+		j = (j + 1) % n
+		k = (int(c.boxTmp[j]) + k) % n
+		c.boxTmp[j], c.boxTmp[k] = c.boxTmp[k], c.boxTmp[j]
+		if i >= 0 {
+			buf[i] ^= c.boxTmp[int(c.boxTmp[j])+int(c.boxTmp[k])%n]
+		}
+	}
+}

algo/qmc/rc4_test.go

@@ -0,0 +1,72 @@
+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)")
+		}
+	})
+}

algo/qmc/testdata/rc4_key.bin

@@ -0,0 +1 @@
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

algo/qmc/testdata/rc4_key_raw.bin

@@ -0,0 +1 @@
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