unshackle/tests/remote/unit/test_tunnel.py

"""The reverse tunnel: a server-side SOCKS5 proxy whose connections the client dials and relays."""

from __future__ import annotations

import asyncio
import http.server
import socket
import socketserver
import threading
import time
from typing import Callable, Iterator

import aiohttp
import click
import pytest
import requests
import responses
from aiohttp import web
from multidict import CIMultiDict

from unshackle.core import tunnel
from unshackle.core.api.routes import tunnel as tunnel_route
from unshackle.core.api.routes import tunnel_check
from unshackle.core.proxies.controld import relay
from unshackle.core.tunnel import (
    CHECK_ROUTE,
    OPEN,
    ROUTE,
    TUNNELS,
    TunnelClient,
    connect_proxied,
    connect_public,
    frame,
    is_ip_literal,
    is_local_ip,
    is_public_ip,
    tunnel_proxy,
)


class Hello(http.server.BaseHTTPRequestHandler):
    hits = 0

    def do_GET(self) -> None:
        Hello.hits += 1
        body = b"hello through the tunnel"
        self.send_response(200)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

    def log_message(self, *_: object) -> None:
        pass


@pytest.fixture
def target() -> Iterator[int]:
    server = socketserver.ThreadingTCPServer(("127.0.0.1", 0), Hello)
    threading.Thread(target=server.serve_forever, daemon=True).start()
    yield server.server_address[1]
    server.shutdown()


@pytest.fixture
def server() -> Iterator[str]:
    loop = asyncio.new_event_loop()
    app = web.Application()
    app.router.add_get(ROUTE, tunnel_route)
    app.router.add_get(CHECK_ROUTE, tunnel_check)
    runner = web.AppRunner(app)
    loop.run_until_complete(runner.setup())
    site = web.TCPSite(runner, "127.0.0.1", 0)
    loop.run_until_complete(site.start())
    port = site._server.sockets[0].getsockname()[1]  # type: ignore[union-attr]
    threading.Thread(target=loop.run_forever, daemon=True).start()
    yield f"http://127.0.0.1:{port}"
    asyncio.run_coroutine_threadsafe(tunnel.close_tunnels(app), loop).result(5)
    loop.call_soon_threadsafe(loop.stop)


def test_requests_through_the_tunnel_reach_the_client_side_target(
    server: str, target: int, monkeypatch: pytest.MonkeyPatch
) -> None:
    monkeypatch.setattr(tunnel, "is_public_ip", lambda address: True)  # the test target is on loopback
    monkeypatch.setattr(tunnel, "dialled_itself", lambda writer: False)
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    tunnel_id = client.start()

    proxy = tunnel_proxy(tunnel_id, "alice")
    assert proxy and proxy.startswith(f"socks5h://{tunnel_id}:") and "@127.0.0.1:" in proxy
    for _ in range(3):
        resp = requests.get(f"http://127.0.0.1:{target}/", proxies={"all": proxy}, timeout=10)
        assert resp.text == "hello through the tunnel"
    client.stop()


def test_a_tunnel_is_only_usable_by_its_owner(server: str) -> None:
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    tunnel_id = client.start()
    assert tunnel_proxy(tunnel_id, "mallory") is None
    assert tunnel_proxy("unknown", "alice") is None
    client.stop()


def test_the_client_refuses_a_target_on_its_own_network(server: str, target: int) -> None:
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    proxy = tunnel_proxy(client.start(), "alice")
    with pytest.raises(requests.exceptions.ConnectionError):
        requests.get(f"http://127.0.0.1:{target}/", proxies={"all": proxy}, timeout=10)
    client.stop()


@pytest.mark.parametrize(
    ("address", "public"),
    [
        ("8.8.8.8", True),
        ("127.0.0.1", False),
        ("192.168.1.10", False),
        ("10.0.0.1", False),
        ("::1", False),
        ("198.18.2.36", False),
        ("64:ff9b::c0a8:101", False),
    ],
)
def test_is_public_ip(address: str, public: bool) -> None:
    assert is_public_ip(address) is public


@pytest.mark.parametrize(
    ("address", "local"),
    [
        ("8.8.8.8", False),
        ("198.18.2.36", False),
        ("2001:2::1", False),
        ("192.0.0.69", False),
        ("192.0.0.88", False),
        ("127.0.0.1", True),
        ("10.0.0.1", True),
        ("172.16.0.1", True),
        ("192.168.1.1", True),
        ("169.254.169.254", True),
        ("100.64.0.1", True),
        ("192.0.0.1", True),
        ("0.0.0.0", True),
        ("224.0.0.1", True),
        ("::1", True),
        ("fdfe:dcba:9876::1", True),
        ("fe80::1%eth0", True),
        ("::ffff:192.168.1.1", True),
        ("64:ff9b::c0a8:101", True),
        ("64:ff9b::808:808", False),
        ("::", True),
        ("::7f00:1", True),
        ("::ffff:0:7f00:1", True),
        ("64:ff9b:1::c0a8:101", True),
        ("192.0.0.9", True),
        ("192.0.0.10", True),
        ("not-an-address", True),
    ],
)
def test_is_local_ip(address: str, local: bool) -> None:
    assert is_local_ip(address) is local


@pytest.mark.parametrize("address", ["198.18.2.36", "192.0.0.69", "2001:2::1", "8.8.8.8"])
def test_a_name_that_resolves_to_a_non_local_address_is_dialled(monkeypatch: pytest.MonkeyPatch, address: str) -> None:
    async def resolve(self: object, host: str, port: int, **_: object) -> list:
        return [(socket.AF_INET, socket.SOCK_STREAM, 6, "", (address, port))]

    dialled: list[str] = []

    async def open_connection(address: str, port: int) -> tuple:
        dialled.append(address)
        return None, FakeWriter(("10.0.0.2", 50000), (address, port))

    monkeypatch.setattr(asyncio.BaseEventLoop, "getaddrinfo", resolve)
    monkeypatch.setattr(asyncio, "open_connection", open_connection)
    asyncio.run(connect_public("api.example", 443))
    assert dialled == [address]


class FakeWriter:
    def __init__(self, sockname: tuple, peername: tuple) -> None:
        self.extra = {"sockname": sockname, "peername": peername}
        self.closed = False

    def get_extra_info(self, name: str) -> tuple:
        return self.extra[name]

    def close(self) -> None:
        self.closed = True


@pytest.mark.parametrize(
    ("host", "literal"),
    [
        ("8.8.8.8", True),
        ("::1", True),
        ("198.18.1", True),
        ("3323068417", True),
        ("0x7f.1", True),
        ("api.example", False),
    ],
)
def test_is_ip_literal(host: str, literal: bool) -> None:
    assert is_ip_literal(host) is literal


def test_a_dial_that_reaches_the_client_itself_is_refused(monkeypatch: pytest.MonkeyPatch) -> None:
    async def resolve(self: object, host: str, port: int, **_: object) -> list:
        return [(socket.AF_INET, socket.SOCK_STREAM, 6, "", ("198.18.0.1", port))]

    writer = FakeWriter(("198.18.0.1", 50000), ("198.18.0.1", 443))

    async def open_connection(address: str, port: int) -> tuple:
        return None, writer

    monkeypatch.setattr(asyncio.BaseEventLoop, "getaddrinfo", resolve)
    monkeypatch.setattr(asyncio, "open_connection", open_connection)
    with pytest.raises(PermissionError, match="this machine"):
        asyncio.run(connect_public("tun.example", 443))
    assert writer.closed


def test_localhost_is_refused() -> None:
    with pytest.raises(PermissionError):
        asyncio.run(connect_public("localhost", 443))


@pytest.mark.parametrize(
    ("host", "address"),
    [
        ("rebind.example", "192.168.1.1"),
        ("metadata.example", "169.254.169.254"),
        ("nat64.example", "64:ff9b::c0a8:101"),
        ("198.18.0.1", "198.18.0.1"),
        ("192.0.0.69", "192.0.0.69"),
        ("198.18.1", "198.18.0.1"),
        ("3221225541", "192.0.0.69"),
    ],
)
def test_a_target_that_resolves_to_a_local_address_is_refused(
    monkeypatch: pytest.MonkeyPatch, host: str, address: str
) -> None:
    async def resolve(self: object, host: str, port: int, **_: object) -> list:
        return [(socket.AF_INET, socket.SOCK_STREAM, 6, "", (address, port))]

    monkeypatch.setattr(asyncio.BaseEventLoop, "getaddrinfo", resolve)
    with pytest.raises(PermissionError):
        asyncio.run(connect_public(host, 443))


def local_proxy_ctx(params: dict, typed: set) -> click.Context:
    from click.core import ParameterSource

    ctx = click.Context(click.Command("dl"))
    ctx.params = {"local_proxy": True, **params}
    for key in params:
        ctx.set_parameter_source(key, ParameterSource.COMMANDLINE if key in typed else ParameterSource.DEFAULT_MAP)
    return ctx


def test_local_proxy_works_with_a_typed_proxy_and_no_other_proxy_option() -> None:
    from unshackle.core.proxies.resolve import require_alone_local_proxy

    with pytest.raises(click.UsageError, match="with --proxy-download\\.$"):
        require_alone_local_proxy(
            local_proxy_ctx({"remote": True, "proxy": "us", "proxy_download": "us"}, {"proxy", "proxy_download"})
        )
    ctx = local_proxy_ctx({"remote": True, "proxy": "http://127.0.0.1:8080"}, {"proxy"})
    require_alone_local_proxy(ctx)
    assert ctx.params["proxy"] == "http://127.0.0.1:8080"
    with pytest.raises(click.UsageError, match="needs --remote"):
        require_alone_local_proxy(local_proxy_ctx({"remote": False}, set()))


def test_local_proxy_turns_off_a_proxy_from_the_config_defaults() -> None:
    from unshackle.core.proxies.resolve import require_alone_local_proxy

    ctx = local_proxy_ctx({"remote": True, "proxy": "us", "no_proxy_download": True}, set())
    require_alone_local_proxy(ctx)
    assert ctx.params["proxy"] is None and ctx.params["no_proxy_download"] is False


def test_the_tunnel_port_refuses_a_proxy_uri_without_the_tunnel_credentials(
    server: str, target: int, monkeypatch: pytest.MonkeyPatch
) -> None:
    monkeypatch.setattr(tunnel, "is_public_ip", lambda address: True)
    monkeypatch.setattr(tunnel, "dialled_itself", lambda writer: False)
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    tunnel_id = client.start()
    port = TUNNELS[tunnel_id].port
    for uri in (f"socks5h://127.0.0.1:{port}", f"socks5h://{tunnel_id}:wrong@127.0.0.1:{port}"):
        with pytest.raises(requests.exceptions.ConnectionError):
            requests.get(f"http://127.0.0.1:{target}/", proxies={"all": uri}, timeout=10)
    client.stop()


def test_the_server_never_dials_for_a_client(server: str, target: int) -> None:
    """An OPEN from the client must not make the server connect anywhere: only the client dials."""

    async def send_open() -> None:
        async with aiohttp.ClientSession(headers={"X-Secret-Key": "mallory"}) as http:
            async with http.ws_connect(server + ROUTE) as ws:
                await ws.receive_json()
                await ws.send_bytes(frame(1, OPEN, target.to_bytes(2, "big") + b"127.0.0.1"))

    Hello.hits = 0
    asyncio.run(send_open())
    assert Hello.hits == 0


def test_the_check_route_is_only_for_the_tunnel_owner(server: str) -> None:
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    tunnel_id = client.start()
    resp = requests.get(f"{server}{CHECK_ROUTE}?id={tunnel_id}", headers={"X-Secret-Key": "mallory"}, timeout=10)
    assert resp.status_code == 404
    client.stop()


@pytest.mark.parametrize(
    ("uri", "line"),
    [
        ("socks5://127.0.0.1:1080", "Using a local proxy on port 1080"),
        ("http://localhost:8888", "Using a local proxy on port 8888"),
        ("http://1.2.3.4:8080", "Using explicit Proxy: http://1.2.3.4:8080"),
        ("http://localhost", "Using a local proxy"),
        ("http://127.0.0.1:99999", "Using a local proxy"),
    ],
)
def test_a_local_proxy_logs_only_its_port(uri: str, line: str) -> None:
    from unshackle.core.proxies.resolve import describe_explicit_proxy

    assert describe_explicit_proxy(uri) == line


def test_another_api_key_cannot_reattach_to_a_tunnel(server: str) -> None:
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    tunnel_id = client.start()

    async def reattach() -> None:
        async with aiohttp.ClientSession(headers={"X-Secret-Key": "mallory"}) as http:
            async with http.ws_connect(f"{server}{ROUTE}?id={tunnel_id}"):
                pass

    with pytest.raises(aiohttp.WSServerHandshakeError) as e:
        asyncio.run(reattach())
    assert e.value.status == 404
    client.stop()


def test_a_request_that_is_not_a_websocket_opens_no_tunnel(server: str) -> None:
    before = len(TUNNELS)
    resp = requests.get(server + ROUTE, headers={"X-Secret-Key": "alice"}, timeout=10)
    assert resp.status_code == 400
    assert len(TUNNELS) == before


def test_a_malformed_frame_still_leaves_the_tunnel_to_expire(server: str) -> None:
    async def send_short_frame() -> str:
        async with aiohttp.ClientSession(headers={"X-Secret-Key": "mallory"}) as http:
            async with http.ws_connect(server + ROUTE) as ws:
                tunnel_id = (await ws.receive_json())["id"]
                await ws.send_bytes(b"\x01")
                await ws.close(code=aiohttp.WSCloseCode.GOING_AWAY)
        return str(tunnel_id)

    tunnel_id = asyncio.run(send_short_frame())
    deadline = time.monotonic() + 5
    while TUNNELS[tunnel_id].expiry is None and time.monotonic() < deadline:
        time.sleep(0.05)
    assert TUNNELS[tunnel_id].expiry is not None


def test_an_api_key_has_a_tunnel_limit(server: str) -> None:
    clients = [TunnelClient(server, {"X-Secret-Key": "bob"}) for _ in range(tunnel.MAX_TUNNELS)]
    for client in clients:
        client.start()
    with pytest.raises(ConnectionError, match="429, the API key already has the maximum number of tunnels open"):
        TunnelClient(server, {"X-Secret-Key": "bob"}).start()
    for client in clients:
        client.stop()


@pytest.mark.parametrize("shared", [True, False])
def test_a_shared_api_key_counts_tunnels_for_each_client(
    server: str, monkeypatch: pytest.MonkeyPatch, shared: bool
) -> None:
    from unshackle.core.config import config

    monkeypatch.setitem(config.serve, "users", {"tier": {"shared": True} if shared else {}})
    first = [TunnelClient(server, {"X-Secret-Key": "tier", "X-Client-Id": "u1"}) for _ in range(tunnel.MAX_TUNNELS)]
    second = TunnelClient(server, {"X-Secret-Key": "tier", "X-Client-Id": "u2"})
    try:
        for client in first:
            client.start()
        if shared:
            second.start()
        else:
            with pytest.raises(ConnectionError, match="maximum number of tunnels"):
                second.start()
        with pytest.raises(ConnectionError, match="maximum number of tunnels"):
            TunnelClient(server, {"X-Secret-Key": "tier", "X-Client-Id": "u1"}).start()
    finally:
        for client in [*first, second]:
            client.stop()


def test_another_client_of_a_shared_api_key_cannot_reattach(server: str, monkeypatch: pytest.MonkeyPatch) -> None:
    from unshackle.core.config import config

    monkeypatch.setitem(config.serve, "users", {"tier": {"shared": True}})
    owner = TunnelClient(server, {"X-Secret-Key": "tier", "X-Client-Id": "u1"})
    tunnel_id = owner.start()
    try:
        resp = requests.get(
            f"{server}{ROUTE}?id={tunnel_id}", headers={"X-Secret-Key": "tier", "X-Client-Id": "u2"}, timeout=10
        )
        assert resp.status_code == 404
    finally:
        owner.stop()


def test_stopping_one_client_leaves_the_other_tunnels_of_its_api_key_open(
    server: str, target: int, monkeypatch: pytest.MonkeyPatch
) -> None:
    monkeypatch.setattr(tunnel, "is_public_ip", lambda address: True)
    monkeypatch.setattr(tunnel, "dialled_itself", lambda writer: False)
    clients = [TunnelClient(server, {"X-Secret-Key": "erin"}) for _ in range(3)]
    stopped, *running = [client.start() for client in clients]
    try:
        clients[0].stop()
        assert wait_until(lambda: stopped not in TUNNELS, 5)
        for tunnel_id in running:
            proxy = tunnel_proxy(tunnel_id, "erin")
            assert proxy
            resp = requests.get(f"http://127.0.0.1:{target}/", proxies={"all": proxy}, timeout=10)
            assert resp.text == "hello through the tunnel"
    finally:
        for client in clients[1:]:
            client.stop()


@pytest.mark.parametrize(
    ("value", "seconds"),
    [
        ("5", 5),
        ("0", 1),
        (None, None),
        ("", None),
        ("\u00b2", None),
        ("9" * 5000, None),
        ("Wed, 21 Oct 2026 07:28:00 GMT", None),
    ],
    ids=["seconds", "zero", "absent", "empty", "superscript", "huge", "http-date"],
)
def test_parse_retry_after(value: str | None, seconds: int | None) -> None:
    assert tunnel.parse_retry_after(value) == seconds


def test_a_client_that_exits_frees_its_tunnel_at_once(server: str) -> None:
    async def open_then_leave() -> str:
        async with aiohttp.ClientSession(headers={"X-Secret-Key": "dave"}) as http:
            async with http.ws_connect(server + ROUTE) as ws:
                return str((await ws.receive_json())["id"])

    tunnel_id = asyncio.run(open_then_leave())
    assert wait_until(lambda: tunnel_id not in TUNNELS, 5)


@pytest.mark.parametrize(
    ("status", "headers", "reason"),
    [
        (429, {"Retry-After": "120"}, "HTTP 429, the API key is over its hourly request limit, retry in 120s"),
        (429, {"retry-after": "120"}, "HTTP 429, the API key is over its hourly request limit, retry in 120s"),
        (429, {}, "HTTP 429, the API key already has the maximum number of tunnels open"),
        (404, None, "HTTP 404"),
    ],
)
def test_a_refused_tunnel_names_the_reason(status: int, headers: dict[str, str] | None, reason: str) -> None:
    error = aiohttp.WSServerHandshakeError(None, (), status=status, headers=CIMultiDict(headers or {}))  # type: ignore[arg-type]
    assert tunnel.refusal(error) == reason


def test_a_connection_that_stops_reading_is_dropped() -> None:
    sent: list = []

    class FakeWS:
        closed = False

        async def send_bytes(self, data: bytes) -> None:
            sent.append(data)

    async def flood() -> tunnel.Link:
        link = tunnel.Link(FakeWS())
        link.streams[7] = tunnel.new_queue()
        for _ in range(tunnel.BACKLOG + 5):
            await link.feed(7, b"x")
        return link

    link = asyncio.run(flood())
    assert 7 not in link.streams
    assert sent == [frame(7, tunnel.CLOSE)]


def test_a_download_job_refuses_a_tunnel_proxy(monkeypatch: pytest.MonkeyPatch) -> None:
    from unshackle.core.api import handlers
    from unshackle.core.api.errors import APIError

    monkeypatch.setattr(handlers, "server_cdm_allowed", lambda request, service: True)
    monkeypatch.setattr(handlers, "server_cdm_max_height", lambda request, service: None)
    with pytest.raises(APIError, match="tunnel"):
        handlers.enforce_download_gates({"service": "EXAMPLE", "proxy": "tunnel:abc"}, None)


@responses.activate
def test_a_server_error_after_the_tunnel_closed_names_the_tunnel() -> None:
    from types import SimpleNamespace

    from unshackle.core.remote_service import RemoteClient, RemoteError

    responses.add(
        responses.GET,
        "http://srv:8786/api/session/x/titles",
        json={"status": "error", "error_code": "SERVICE_ERROR", "message": "proxy refused"},
        status=422,
    )
    client = RemoteClient("http://srv:8786", "")
    client.tunnel = SimpleNamespace(lost=True)  # type: ignore[assignment]
    with pytest.raises(RemoteError) as e:
        client.get("/api/session/x/titles")
    assert e.value.kind == "TUNNEL_CLOSED"


def spy_links(monkeypatch: pytest.MonkeyPatch) -> list:
    """Record every Link the client makes, so a test can look at its open streams."""
    links: list = []

    class SpyLink(tunnel.Link):
        def __init__(self, ws: object) -> None:
            super().__init__(ws)
            links.append(self)

    monkeypatch.setattr(tunnel, "Link", SpyLink)
    return links


def wait_until(check: "Callable[[], bool]", seconds: float = 3) -> bool:
    deadline = time.monotonic() + seconds
    while not check() and time.monotonic() < deadline:
        time.sleep(0.05)
    return check()


def test_a_dial_the_server_gave_up_on_is_dropped_by_the_client(
    server: str, target: int, monkeypatch: pytest.MonkeyPatch
) -> None:
    """When the server times out an OPEN, the client must not keep the connection it makes later."""
    monkeypatch.setattr(tunnel, "is_public_ip", lambda address: True)
    monkeypatch.setattr(tunnel, "dialled_itself", lambda writer: False)
    monkeypatch.setattr(tunnel, "OPEN_TIMEOUT", 0.3)
    real_connect = tunnel.connect_public

    async def slow_connect(host: str, port: int) -> tuple:
        await asyncio.sleep(1)
        return await real_connect(host, port)

    monkeypatch.setattr(tunnel, "connect_public", slow_connect)
    links = spy_links(monkeypatch)
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    proxy = tunnel_proxy(client.start(), "alice")
    with pytest.raises(requests.exceptions.ConnectionError):
        requests.get(f"http://127.0.0.1:{target}/", proxies={"all": proxy}, timeout=10)
    assert wait_until(lambda: not links[-1].streams and not client.relays)
    client.stop()


def socks5_connect(proxy: str, host: bytes) -> int:
    """Send one SOCKS5 CONNECT for ``host`` with the credentials in ``proxy`` and return the reply code."""
    from urllib.parse import urlsplit

    parts = urlsplit(proxy)
    user, password = (parts.username or "").encode(), (parts.password or "").encode()
    with socket.create_connection(("127.0.0.1", parts.port or 0), timeout=10) as sock:
        sock.sendall(b"\x05\x01\x02")
        assert sock.recv(2) == b"\x05\x02"
        sock.sendall(b"\x01" + bytes([len(user)]) + user + bytes([len(password)]) + password)
        assert sock.recv(2) == b"\x01\x00"
        sock.sendall(b"\x05\x01\x00\x03" + bytes([len(host)]) + host + (443).to_bytes(2, "big"))
        return sock.recv(10)[1]


def test_a_hostname_the_resolver_rejects_closes_its_stream(server: str, monkeypatch: pytest.MonkeyPatch) -> None:
    async def resolve(self: object, host: str, port: int, **_: object) -> list:
        host.encode("idna")  # as socket.getaddrinfo does, so a long label raises UnicodeError
        return []

    monkeypatch.setattr(asyncio.BaseEventLoop, "getaddrinfo", resolve)
    monkeypatch.setattr(tunnel, "OPEN_TIMEOUT", 1)
    links = spy_links(monkeypatch)
    client = TunnelClient(server, {"X-Secret-Key": "alice"})
    proxy = tunnel_proxy(client.start(), "alice")
    assert proxy
    assert socks5_connect(proxy, b"a" * 64 + b".example") == 5
    assert wait_until(lambda: not links[-1].streams)
    client.stop()


def test_a_failed_start_leaves_no_thread_behind() -> None:
    silent = socket.socket()
    silent.bind(("127.0.0.1", 0))
    silent.listen()
    try:
        client = TunnelClient(f"http://127.0.0.1:{silent.getsockname()[1]}", {"X-Secret-Key": "alice"})
        with pytest.raises(ConnectionError, match="timed out"):
            client.start(timeout=0.5)
        assert not client.thread.is_alive()
    finally:
        silent.close()


class ExitProxy(socketserver.BaseRequestHandler):
    """An exit proxy on this machine: takes one HTTP CONNECT or SOCKS5 CONNECT and pipes it to the test target."""

    server: ExitServer

    def handle(self) -> None:
        sock, seen = self.request, self.server.seen
        stream = sock.makefile("rb")
        if stream.peek(1)[:1] == b"\x05":
            stream.read(stream.read(2)[1])
            sock.sendall(b"\x05\x02")
            stream.read(1)
            user = stream.read(stream.read(1)[0])
            seen.append(user + b":" + stream.read(stream.read(1)[0]))
            sock.sendall(b"\x01\x00")
            address_type = stream.read(4)[3]
            seen.append(stream.read(stream.read(1)[0] if address_type == 3 else 4 if address_type == 1 else 16))
            stream.read(2)
            sock.sendall(b"\x05\x00\x00\x01" + bytes(6))
        else:
            head = b""
            while not head.endswith(b"\r\n\r\n"):
                head += stream.readline()
            seen.append(head)
            sock.sendall(b"HTTP/1.1 " + self.server.status + b"\r\n\r\n")
            if not self.server.status.startswith(b"200"):
                return
        upstream = socket.create_connection(("127.0.0.1", self.server.target))
        threading.Thread(target=relay, args=(upstream, sock), daemon=True).start()
        relay(sock, upstream)


class ExitServer(socketserver.ThreadingTCPServer):
    daemon_threads = True
    seen: list[bytes]
    status: bytes
    target: int


@pytest.fixture
def exit_proxy(target: int) -> Iterator[ExitServer]:
    proxy = ExitServer(("127.0.0.1", 0), ExitProxy)
    proxy.seen, proxy.status, proxy.target = [], b"200 Connection established", target
    threading.Thread(target=proxy.serve_forever, daemon=True).start()
    yield proxy
    proxy.shutdown()


@pytest.mark.parametrize("scheme", ["http", "socks5h"])
def test_the_tunnel_dials_through_an_exit_proxy_with_its_login(
    server: str, exit_proxy: ExitServer, scheme: str
) -> None:
    port = exit_proxy.server_address[1]
    client = TunnelClient(server, {"X-Secret-Key": "alice"}, f"{scheme}://us%40er:p%3Ass@127.0.0.1:{port}")
    proxy = tunnel_proxy(client.start(), "alice")
    resp = requests.get("http://hello.example/", proxies={"all": proxy}, timeout=10)
    client.stop()

    assert resp.text == "hello through the tunnel"
    if scheme == "http":
        assert exit_proxy.seen[0].startswith(b"CONNECT hello.example:80 HTTP/1.1\r\n")
        assert b"Proxy-Authorization: Basic dXNAZXI6cDpzcw==\r\n" in exit_proxy.seen[0]
    else:
        assert exit_proxy.seen == [b"us@er:p:ss", b"hello.example"]


@pytest.mark.parametrize(
    ("host", "address"),
    [
        ("127.0.0.1", None),
        ("::1", None),
        ("10.1", None),
        ("localhost", None),
        ("printer.localhost.", None),
        ("bad.example\r\nX-Injected: 1", None),
        ("bad example", None),
        ("rebind.example", "192.168.1.1"),
        ("metadata.example", "169.254.169.254"),
    ],
)
def test_the_exit_proxy_never_carries_a_local_or_malformed_target(
    monkeypatch: pytest.MonkeyPatch, exit_proxy: ExitServer, host: str, address: str | None
) -> None:
    async def resolve(self: object, host: str, port: int, **_: object) -> list:
        return [(socket.AF_INET, socket.SOCK_STREAM, 6, "", (address, port))]

    if address:
        monkeypatch.setattr(asyncio.BaseEventLoop, "getaddrinfo", resolve)
    with pytest.raises(PermissionError):
        asyncio.run(connect_proxied(f"http://127.0.0.1:{exit_proxy.server_address[1]}", host, 80))
    assert exit_proxy.seen == []


def test_a_refused_connect_fails_and_never_dials_direct(
    server: str, target: int, exit_proxy: ExitServer, monkeypatch: pytest.MonkeyPatch
) -> None:
    monkeypatch.setattr(tunnel, "is_public_ip", lambda address: True)  # so a direct dial to the target would work
    monkeypatch.setattr(tunnel, "dialled_itself", lambda writer: False)
    exit_proxy.status = b"407 Proxy Authentication Required"
    hits = Hello.hits
    client = TunnelClient(server, {"X-Secret-Key": "alice"}, f"http://127.0.0.1:{exit_proxy.server_address[1]}")
    proxy = tunnel_proxy(client.start(), "alice")
    with pytest.raises(requests.exceptions.ConnectionError):
        requests.get(f"http://127.0.0.1:{target}/", proxies={"all": proxy}, timeout=10)
    client.stop()
    assert len(exit_proxy.seen) == 1 and Hello.hits == hits
    with pytest.raises(OSError, match="407"):
        asyncio.run(connect_proxied(f"http://127.0.0.1:{exit_proxy.server_address[1]}", "hello.example", 80))


def test_a_proxy_the_tunnel_cannot_dial_through_is_refused_at_start() -> None:
    from unshackle.core.remote_service import start_tunnel

    with pytest.raises(click.ClickException, match="cannot use a socks4 proxy"):
        start_tunnel(None, "socks4://127.0.0.1:1080")  # type: ignore[arg-type]