feat(go): Port full Ananta private server to Go architecture

pkg/crypto/chacha8/chacha8.go

@@ -0,0 +1,114 @@
+package chacha8
+
+import (
+	"encoding/binary"
+	"errors"
+	"math/bits"
+)
+
+// NetEase 4229938 UXChaCha8 stream cipher.
+// Uses custom Sigma constants differing from standard ChaCha.
+const (
+	Sigma0 uint32 = 0x60707865
+	Sigma1 uint32 = 0x3321646e
+	Sigma2 uint32 = 0x79622d32
+	Sigma3 uint32 = 0x6b206e74
+)
+
+type UxChaCha8 struct {
+	state        [16]uint32
+	keystream    [64]byte
+	keystreamPos int
+}
+
+func New(key []byte, nonce []byte) (*UxChaCha8, error) {
+	if len(key) != 32 {
+		return nil, errors.New("UXChaCha8 key must be 32 bytes")
+	}
+	if len(nonce) != 12 {
+		return nil, errors.New("UXChaCha8 nonce must be 12 bytes")
+	}
+
+	c := &UxChaCha8{
+		keystreamPos: 64,
+	}
+
+	c.state[0] = Sigma0
+	c.state[1] = Sigma1
+	c.state[2] = Sigma2
+	c.state[3] = Sigma3
+
+	for i := 0; i < 8; i++ {
+		c.state[4+i] = binary.LittleEndian.Uint32(key[i*4 : (i+1)*4])
+	}
+
+	c.state[12] = 0
+	c.state[13] = binary.LittleEndian.Uint32(nonce[0:4])
+	c.state[14] = binary.LittleEndian.Uint32(nonce[4:8])
+	c.state[15] = binary.LittleEndian.Uint32(nonce[8:12])
+
+	return c, nil
+}
+
+func (c *UxChaCha8) XorInPlace(data []byte) {
+	offset := 0
+	for offset < len(data) {
+		if c.keystreamPos == 64 {
+			c.generateBlock()
+			c.keystreamPos = 0
+		}
+
+		take := 64 - c.keystreamPos
+		if len(data)-offset < take {
+			take = len(data) - offset
+		}
+
+		for i := 0; i < take; i++ {
+			data[offset+i] ^= c.keystream[c.keystreamPos+i]
+		}
+
+		offset += take
+		c.keystreamPos += take
+	}
+}
+
+func (c *UxChaCha8) generateBlock() {
+	var x [16]uint32
+	copy(x[:], c.state[:])
+
+	for i := 0; i < 4; i++ {
+		quarterRound(&x[0], &x[4], &x[8], &x[12])
+		quarterRound(&x[1], &x[5], &x[9], &x[13])
+		quarterRound(&x[2], &x[6], &x[10], &x[14])
+		quarterRound(&x[3], &x[7], &x[11], &x[15])
+
+		quarterRound(&x[0], &x[5], &x[10], &x[15])
+		quarterRound(&x[1], &x[6], &x[11], &x[12])
+		quarterRound(&x[2], &x[7], &x[8], &x[13])
+		quarterRound(&x[3], &x[4], &x[9], &x[14])
+	}
+
+	for i := 0; i < 16; i++ {
+		binary.LittleEndian.PutUint32(c.keystream[i*4:(i+1)*4], x[i]+c.state[i])
+	}
+
+	c.state[12]++
+}
+
+func quarterRound(a, b, c, d *uint32) {
+	*a += *b
+	*d ^= *a
+	*d = bits.RotateLeft32(*d, 16)
+
+	*c += *d
+	*b ^= *c
+	*b = bits.RotateLeft32(*b, 12)
+
+	*a += *b
+	*d ^= *a
+	*d = bits.RotateLeft32(*d, 8)
+
+	*c += *d
+	*b ^= *c
+	*b = bits.RotateLeft32(*b, 7)
+}

pkg/crypto/chacha8/chacha8_test.go

@@ -0,0 +1,41 @@
+package chacha8
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestChaCha8Roundtrip(t *testing.T) {
+	key := make([]byte, 32)
+	for i := range key {
+		key[i] = byte(i + 1)
+	}
+	nonce := make([]byte, 12)
+	for i := range nonce {
+		nonce[i] = byte(i + 0x10)
+	}
+
+	c1, err := New(key, nonce)
+	if err != nil {
+		t.Fatalf("New failed: %v", err)
+	}
+
+	c2, err := New(key, nonce)
+	if err != nil {
+		t.Fatalf("New failed: %v", err)
+	}
+
+	original := []byte("Hello, Ananta NetEase UXChaCha8 stream cipher verification!")
+	data := make([]byte, len(original))
+	copy(data, original)
+
+	c1.XorInPlace(data)
+	if bytes.Equal(data, original) {
+		t.Errorf("Ciphertext equals plaintext")
+	}
+
+	c2.XorInPlace(data)
+	if !bytes.Equal(data, original) {
+		t.Errorf("Decrypted data != original: got %q, want %q", data, original)
+	}
+}