Chore: make hadowsocks2 lib embed

transport/shadowsocks/shadowstream/packet.go

@@ -0,0 +1,79 @@
+package shadowstream
+
+import (
+	"crypto/rand"
+	"errors"
+	"io"
+	"net"
+
+	"github.com/Dreamacro/clash/common/pool"
+)
+
+// ErrShortPacket means the packet is too short to be a valid encrypted packet.
+var ErrShortPacket = errors.New("short packet")
+
+// Pack encrypts plaintext using stream cipher s and a random IV.
+// Returns a slice of dst containing random IV and ciphertext.
+// Ensure len(dst) >= s.IVSize() + len(plaintext).
+func Pack(dst, plaintext []byte, s Cipher) ([]byte, error) {
+	if len(dst) < s.IVSize()+len(plaintext) {
+		return nil, io.ErrShortBuffer
+	}
+	iv := dst[:s.IVSize()]
+	_, err := rand.Read(iv)
+	if err != nil {
+		return nil, err
+	}
+	s.Encrypter(iv).XORKeyStream(dst[len(iv):], plaintext)
+	return dst[:len(iv)+len(plaintext)], nil
+}
+
+// Unpack decrypts pkt using stream cipher s.
+// Returns a slice of dst containing decrypted plaintext.
+func Unpack(dst, pkt []byte, s Cipher) ([]byte, error) {
+	if len(pkt) < s.IVSize() {
+		return nil, ErrShortPacket
+	}
+	if len(dst) < len(pkt)-s.IVSize() {
+		return nil, io.ErrShortBuffer
+	}
+	iv := pkt[:s.IVSize()]
+	s.Decrypter(iv).XORKeyStream(dst, pkt[len(iv):])
+	return dst[:len(pkt)-len(iv)], nil
+}
+
+type PacketConn struct {
+	net.PacketConn
+	Cipher
+}
+
+// NewPacketConn wraps a net.PacketConn with stream cipher encryption/decryption.
+func NewPacketConn(c net.PacketConn, ciph Cipher) *PacketConn {
+	return &PacketConn{PacketConn: c, Cipher: ciph}
+}
+
+const maxPacketSize = 64 * 1024
+
+func (c *PacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
+	buf := pool.Get(maxPacketSize)
+	defer pool.Put(buf)
+	buf, err := Pack(buf, b, c.Cipher)
+	if err != nil {
+		return 0, err
+	}
+	_, err = c.PacketConn.WriteTo(buf, addr)
+	return len(b), err
+}
+
+func (c *PacketConn) ReadFrom(b []byte) (int, net.Addr, error) {
+	n, addr, err := c.PacketConn.ReadFrom(b)
+	if err != nil {
+		return n, addr, err
+	}
+	bb, err := Unpack(b[c.IVSize():], b[:n], c.Cipher)
+	if err != nil {
+		return n, addr, err
+	}
+	copy(b, bb)
+	return len(bb), addr, err
+}