One-KVM/kvmd/apps/janus/stun.py

import asyncio
import socket
import struct
import secrets
import dataclasses

from typing import Tuple
from typing import Dict
from typing import Optional

from ... import tools
from ... import aiotools

from ...logging import get_logger


# =====
@dataclasses.dataclass(frozen=True)
class StunAddress:
    ip: str
    port: int


@dataclasses.dataclass(frozen=True)
class StunResponse:
    ok: bool
    ext: Optional[StunAddress] = dataclasses.field(default=None)
    src: Optional[StunAddress] = dataclasses.field(default=None)
    changed: Optional[StunAddress] = dataclasses.field(default=None)


class StunNatType:
    BLOCKED = "Blocked"
    OPEN_INTERNET = "Open Internet"
    SYMMETRIC_UDP_FW = "Symmetric UDP Firewall"
    FULL_CONE_NAT = "Full Cone NAT"
    RESTRICTED_NAT = "Restricted NAT"
    RESTRICTED_PORT_NAT = "Restricted Port NAT"
    SYMMETRIC_NAT = "Symmetric NAT"
    CHANGED_ADDR_ERROR = "Error when testing on Changed-IP and Port"


# =====
class Stun:
    # Partially based on https://github.com/JohnVillalovos/pystun

    def __init__(
        self,
        host: str,
        port: int,
        timeout: float,
        retries: int,
        retries_delay: float,
    ) -> None:

        self.host = host
        self.port = port
        self.__timeout = timeout
        self.__retries = retries
        self.__retries_delay = retries_delay

        self.__sock: Optional[socket.socket] = None

    async def get_info(self, src_ip: str, src_port: int) -> Tuple[str, str]:

        (family, _, _, _, addr) = socket.getaddrinfo(src_ip, src_port, type=socket.SOCK_DGRAM)[0]
        try:
            with socket.socket(family, socket.SOCK_DGRAM) as self.__sock:
                self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
                self.__sock.settimeout(self.__timeout)
                self.__sock.bind(addr)
                (nat_type, response) = await self.__get_nat_type(src_ip)
                return (nat_type, (response.ext.ip if response.ext is not None else ""))
        finally:
            self.__sock = None

    async def __get_nat_type(self, src_ip: str) -> Tuple[str, StunResponse]:  # pylint: disable=too-many-return-statements
        first = await self.__make_request("First probe")
        if not first.ok:
            return (StunNatType.BLOCKED, first)

        request = struct.pack(">HHI", 0x0003, 0x0004, 0x00000006)  # Change-Request
        response = await self.__make_request("Change request [ext_ip == src_ip]", request)

        if first.ext is not None and first.ext.ip == src_ip:
            if response.ok:
                return (StunNatType.OPEN_INTERNET, response)
            return (StunNatType.SYMMETRIC_UDP_FW, response)

        if response.ok:
            return (StunNatType.FULL_CONE_NAT, response)

        if first.changed is None:
            raise RuntimeError(f"Changed addr is None: {first}")
        response = await self.__make_request("Change request [ext_ip != src_ip]", b"", *first.changed.ip)
        if not response.ok:
            return (StunNatType.CHANGED_ADDR_ERROR, response)

        if response.ext == first.ext:
            request = struct.pack(">HHI", 0x0003, 0x0004, 0x00000002)
            response = await self.__make_request("Change port", request, first.changed.ip)
            if response.ok:
                return (StunNatType.RESTRICTED_NAT, response)
            return (StunNatType.RESTRICTED_PORT_NAT, response)

        return (StunNatType.SYMMETRIC_NAT, response)

    async def __make_request(self, ctx: str, request: bytes=b"", host: str="", port: int=0) -> StunResponse:
        # TODO: Support IPv6 and RFC 5389
        # The first 4 bytes of the response are the Type (2) and Length (2)
        # The 5th byte is Reserved
        # The 6th byte is the Family: 0x01 = IPv4, 0x02 = IPv6
        # The remaining bytes are the IP address. 32 bits for IPv4 or 128 bits for
        # IPv6.
        # More info at: https://tools.ietf.org/html/rfc3489#section-11.2.1
        # And at: https://tools.ietf.org/html/rfc5389#section-15.1

        (response, error) = (b"", "")
        for _ in range(self.__retries):
            (response, error) = await self.__inner_make_request(request, host, port)
            if not error:
                break
            await asyncio.sleep(self.__retries_delay)
        if error:
            get_logger(0).error("%s: Can't perform STUN request after %d retries; last error: %s",
                                ctx, self.__retries, error)
            return StunResponse(ok=False)

        parsed: Dict[str, StunAddress] = {}
        offset = 0
        remaining = len(response)
        while remaining > 0:
            (attr_type, attr_len) = struct.unpack(">HH", response[offset : offset + 4])  # noqa: E203
            offset += 4
            field = {
                0x0001: "ext",      # MAPPED-ADDRESS
                0x0004: "src",      # SOURCE-ADDRESS
                0x0005: "changed",  # CHANGED-ADDRESS
            }.get(attr_type)
            if field is not None:
                parsed[field] = self.__parse_address(response[offset:])
            offset += attr_len
            remaining -= (4 + attr_len)
        return StunResponse(ok=True, **parsed)

    async def __inner_make_request(self, request: bytes, host: str, port: int) -> Tuple[bytes, str]:
        assert self.__sock is not None

        trans_id = secrets.token_bytes(16)
        request = struct.pack(">HH", 0x0001, len(request)) + trans_id + request  # Bind Request

        try:
            await aiotools.run_async(self.__sock.sendto, request, ((host or self.host), (port or self.port)))
        except Exception as err:
            return (b"", f"Send error: {tools.efmt(err)}")
        try:
            response = (await aiotools.run_async(self.__sock.recvfrom, 2048))[0]
        except Exception as err:
            return (b"", f"Recv error: {tools.efmt(err)}")

        (response_type, payload_len) = struct.unpack(">HH", response[:4])
        if response_type != 0x0101:
            return (b"", f"Invalid response type: {response_type:#06x}")
        if trans_id != response[4:20]:
            return (b"", "Transaction ID mismatch")

        return (response[20 : 20 + payload_len], "")  # noqa: E203

    def __parse_address(self, data: bytes) -> StunAddress:
        family = data[1]
        if family == 1:
            parts = struct.unpack(">HBBBB", data[2:8])
            return StunAddress(
                ip=".".join(map(str, parts[1:])),
                port=parts[0],
            )
        raise RuntimeError(f"Only IPv4 supported; received: {family}")