Proxy: Add Hysteria outbound & transport (version 2, udphop) and Salamander udpmask (#5508)

https://github.com/XTLS/Xray-core/issues/3547#issuecomment-3549896520
https://github.com/XTLS/Xray-core/issues/2635#issuecomment-3570871754

proxy/hysteria/protocol.go

@@ -0,0 +1,204 @@
+package hysteria
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"github.com/apernet/quic-go/quicvarint"
+	"github.com/xtls/xray-core/common/errors"
+)
+
+const (
+	FrameTypeTCPRequest = 0x401
+
+	// Max length values are for preventing DoS attacks
+
+	MaxAddressLength = 2048
+	MaxMessageLength = 2048
+	MaxPaddingLength = 4096
+
+	MaxUDPSize = 4096
+
+	maxVarInt1 = 63
+	maxVarInt2 = 16383
+	maxVarInt4 = 1073741823
+	maxVarInt8 = 4611686018427387903
+)
+
+// TCPRequest format:
+// 0x401 (QUIC varint)
+// Address length (QUIC varint)
+// Address (bytes)
+// Padding length (QUIC varint)
+// Padding (bytes)
+
+func WriteTCPRequest(w io.Writer, addr string) error {
+	padding := tcpRequestPadding.String()
+	paddingLen := len(padding)
+	addrLen := len(addr)
+	sz := int(quicvarint.Len(FrameTypeTCPRequest)) +
+		int(quicvarint.Len(uint64(addrLen))) + addrLen +
+		int(quicvarint.Len(uint64(paddingLen))) + paddingLen
+	buf := make([]byte, sz)
+	i := varintPut(buf, FrameTypeTCPRequest)
+	i += varintPut(buf[i:], uint64(addrLen))
+	i += copy(buf[i:], addr)
+	i += varintPut(buf[i:], uint64(paddingLen))
+	copy(buf[i:], padding)
+	_, err := w.Write(buf)
+	return err
+}
+
+// TCPResponse format:
+// Status (byte, 0=ok, 1=error)
+// Message length (QUIC varint)
+// Message (bytes)
+// Padding length (QUIC varint)
+// Padding (bytes)
+
+func ReadTCPResponse(r io.Reader) (bool, string, error) {
+	var status [1]byte
+	if _, err := io.ReadFull(r, status[:]); err != nil {
+		return false, "", err
+	}
+	bReader := quicvarint.NewReader(r)
+	msgLen, err := quicvarint.Read(bReader)
+	if err != nil {
+		return false, "", err
+	}
+	if msgLen > MaxMessageLength {
+		return false, "", errors.New("invalid message length")
+	}
+	var msgBuf []byte
+	// No message is fine
+	if msgLen > 0 {
+		msgBuf = make([]byte, msgLen)
+		_, err = io.ReadFull(r, msgBuf)
+		if err != nil {
+			return false, "", err
+		}
+	}
+	paddingLen, err := quicvarint.Read(bReader)
+	if err != nil {
+		return false, "", err
+	}
+	if paddingLen > MaxPaddingLength {
+		return false, "", errors.New("invalid padding length")
+	}
+	if paddingLen > 0 {
+		_, err = io.CopyN(io.Discard, r, int64(paddingLen))
+		if err != nil {
+			return false, "", err
+		}
+	}
+	return status[0] == 0, string(msgBuf), nil
+}
+
+// UDPMessage format:
+// Session ID (uint32 BE)
+// Packet ID (uint16 BE)
+// Fragment ID (uint8)
+// Fragment count (uint8)
+// Address length (QUIC varint)
+// Address (bytes)
+// Data...
+
+type UDPMessage struct {
+	SessionID uint32 // 4
+	PacketID  uint16 // 2
+	FragID    uint8  // 1
+	FragCount uint8  // 1
+	Addr      string // varint + bytes
+	Data      []byte
+}
+
+func (m *UDPMessage) HeaderSize() int {
+	lAddr := len(m.Addr)
+	return 4 + 2 + 1 + 1 + int(quicvarint.Len(uint64(lAddr))) + lAddr
+}
+
+func (m *UDPMessage) Size() int {
+	return m.HeaderSize() + len(m.Data)
+}
+
+func (m *UDPMessage) Serialize(buf []byte) int {
+	// Make sure the buffer is big enough
+	if len(buf) < m.Size() {
+		return -1
+	}
+	// binary.BigEndian.PutUint32(buf, m.SessionID)
+	binary.BigEndian.PutUint16(buf[4:], m.PacketID)
+	buf[6] = m.FragID
+	buf[7] = m.FragCount
+	i := varintPut(buf[8:], uint64(len(m.Addr)))
+	i += copy(buf[8+i:], m.Addr)
+	i += copy(buf[8+i:], m.Data)
+	return 8 + i
+}
+
+func ParseUDPMessage(msg []byte) (*UDPMessage, error) {
+	m := &UDPMessage{}
+	buf := bytes.NewBuffer(msg)
+	if err := binary.Read(buf, binary.BigEndian, &m.SessionID); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(buf, binary.BigEndian, &m.PacketID); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(buf, binary.BigEndian, &m.FragID); err != nil {
+		return nil, err
+	}
+	if err := binary.Read(buf, binary.BigEndian, &m.FragCount); err != nil {
+		return nil, err
+	}
+	lAddr, err := quicvarint.Read(buf)
+	if err != nil {
+		return nil, err
+	}
+	if lAddr == 0 || lAddr > MaxMessageLength {
+		return nil, errors.New("invalid address length")
+	}
+	bs := buf.Bytes()
+	if len(bs) <= int(lAddr) {
+		// We use <= instead of < here as we expect at least one byte of data after the address
+		return nil, errors.New("invalid message length")
+	}
+	m.Addr = string(bs[:lAddr])
+	m.Data = bs[lAddr:]
+	return m, nil
+}
+
+// varintPut is like quicvarint.Append, but instead of appending to a slice,
+// it writes to a fixed-size buffer. Returns the number of bytes written.
+func varintPut(b []byte, i uint64) int {
+	if i <= maxVarInt1 {
+		b[0] = uint8(i)
+		return 1
+	}
+	if i <= maxVarInt2 {
+		b[0] = uint8(i>>8) | 0x40
+		b[1] = uint8(i)
+		return 2
+	}
+	if i <= maxVarInt4 {
+		b[0] = uint8(i>>24) | 0x80
+		b[1] = uint8(i >> 16)
+		b[2] = uint8(i >> 8)
+		b[3] = uint8(i)
+		return 4
+	}
+	if i <= maxVarInt8 {
+		b[0] = uint8(i>>56) | 0xc0
+		b[1] = uint8(i >> 48)
+		b[2] = uint8(i >> 40)
+		b[3] = uint8(i >> 32)
+		b[4] = uint8(i >> 24)
+		b[5] = uint8(i >> 16)
+		b[6] = uint8(i >> 8)
+		b[7] = uint8(i)
+		return 8
+	}
+	panic(fmt.Sprintf("%#x doesn't fit into 62 bits", i))
+}