121 lines
3.6 KiB
Python
121 lines
3.6 KiB
Python
"""SagerNet UDP over TCP v2 帧编解码。
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UoT 只负责把 UDP 数据报装入已有的可靠 TCP 字节流；外层连接仍由
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HTTP CONNECT + TLS 建立。此模块不依赖 sing-box。
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"""
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from __future__ import annotations
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import ipaddress
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import socket
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import struct
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from dataclasses import dataclass
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MAGIC_ADDRESS = "sp.v2.udp-over-tcp.arpa"
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MAX_DATAGRAM = 65535
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@dataclass(frozen=True)
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class Address:
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host: str
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port: int
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def encode_address(host: str, port: int) -> bytes:
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host = str(host).strip()
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if not 0 <= int(port) <= 65535:
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raise ValueError("端口超出范围")
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try:
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addr = ipaddress.ip_address(host)
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except ValueError:
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raw = host.encode("idna")
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if not 1 <= len(raw) <= 255:
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raise ValueError("域名长度超出 UoT 限制")
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return b"\x02" + bytes([len(raw)]) + raw + struct.pack("!H", int(port))
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if addr.version == 4:
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return b"\x00" + addr.packed + struct.pack("!H", int(port))
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return b"\x01" + addr.packed + struct.pack("!H", int(port))
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def decode_address(data: bytes, offset: int = 0) -> tuple[Address, int]:
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if offset >= len(data):
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raise ValueError("UoT 地址头不完整")
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atyp = data[offset]
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offset += 1
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if atyp == 0:
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size = 4
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elif atyp == 1:
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size = 16
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elif atyp == 2:
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if offset >= len(data):
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raise ValueError("UoT 域名长度缺失")
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size = data[offset]
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offset += 1
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else:
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raise ValueError(f"未知 UoT 地址类型: {atyp}")
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end = offset + size
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if end + 2 > len(data):
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raise ValueError("UoT 地址头不完整")
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raw = data[offset:end]
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port = struct.unpack("!H", data[end:end + 2])[0]
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if atyp == 0:
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host = str(ipaddress.IPv4Address(raw))
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elif atyp == 1:
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host = str(ipaddress.IPv6Address(raw))
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else:
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host = raw.decode("idna")
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return Address(host, port), end + 2
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def encode_request(is_connect: bool, destination: Address) -> bytes:
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return (b"\x01" if is_connect else b"\x00") + encode_address(
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destination.host, destination.port
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)
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def encode_connect_frame(payload: bytes) -> bytes:
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if len(payload) > MAX_DATAGRAM:
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raise ValueError("UoT 数据报超过 65535 字节")
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return struct.pack("!H", len(payload)) + payload
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def encode_datagram_frame(destination: Address, payload: bytes) -> bytes:
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if len(payload) > MAX_DATAGRAM:
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raise ValueError("UoT 数据报超过 65535 字节")
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return encode_address(destination.host, destination.port) + struct.pack("!H", len(payload)) + payload
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def read_exact(stream, size: int) -> bytes:
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chunks = []
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remaining = size
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while remaining:
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chunk = stream.recv(remaining)
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if not chunk:
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raise ConnectionError("UoT TCP 流已关闭")
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chunks.append(chunk)
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remaining -= len(chunk)
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return b"".join(chunks)
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def read_connect_frame(stream) -> bytes:
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size = struct.unpack("!H", read_exact(stream, 2))[0]
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return read_exact(stream, size)
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def read_datagram_frame(stream) -> tuple[Address, bytes]:
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# 地址是变长的，只能先读 ATYP，再按类型补齐。
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head = read_exact(stream, 1)
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atyp = head[0]
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if atyp == 0:
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rest = read_exact(stream, 6)
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elif atyp == 1:
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rest = read_exact(stream, 18)
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elif atyp == 2:
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length = read_exact(stream, 1)
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rest = length + read_exact(stream, length[0] + 2)
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else:
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raise ValueError(f"未知 UoT 地址类型: {atyp}")
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address, _ = decode_address(head + rest)
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size = struct.unpack("!H", read_exact(stream, 2))[0]
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return address, read_exact(stream, size)
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