# Copyright 2019 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import base64
import logging
import os
from typing import Any, Awaitable, Callable, Generator, List, Optional, cast
from unittest.mock import Mock, patch

import treq
from netaddr import IPSet
from service_identity import VerificationError
from zope.interface import implementer

from twisted.internet import defer
from twisted.internet._sslverify import ClientTLSOptions, OpenSSLCertificateOptions
from twisted.internet.defer import Deferred
from twisted.internet.endpoints import _WrappingProtocol
from twisted.internet.interfaces import (
    IOpenSSLClientConnectionCreator,
    IProtocolFactory,
)
from twisted.internet.protocol import Factory
from twisted.protocols.tls import TLSMemoryBIOFactory, TLSMemoryBIOProtocol
from twisted.web._newclient import ResponseNeverReceived
from twisted.web.client import Agent
from twisted.web.http import HTTPChannel, Request
from twisted.web.http_headers import Headers
from twisted.web.iweb import IPolicyForHTTPS, IResponse

from synapse.config.homeserver import HomeServerConfig
from synapse.crypto.context_factory import FederationPolicyForHTTPS
from synapse.http.federation.matrix_federation_agent import MatrixFederationAgent
from synapse.http.federation.srv_resolver import Server
from synapse.http.federation.well_known_resolver import (
    WELL_KNOWN_MAX_SIZE,
    WellKnownResolver,
    _cache_period_from_headers,
)
from synapse.logging.context import (
    SENTINEL_CONTEXT,
    LoggingContext,
    LoggingContextOrSentinel,
    current_context,
)
from synapse.types import ISynapseReactor
from synapse.util.caches.ttlcache import TTLCache

from tests import unittest
from tests.http import (
    TestServerTLSConnectionFactory,
    dummy_address,
    get_test_ca_cert_file,
)
from tests.server import FakeTransport, ThreadedMemoryReactorClock
from tests.utils import checked_cast, default_config

logger = logging.getLogger(__name__)


# Once Async Mocks or lambdas are supported this can go away.
def generate_resolve_service(
    result: List[Server],
) -> Callable[[Any], Awaitable[List[Server]]]:
    async def resolve_service(_: Any) -> List[Server]:
        return result

    return resolve_service


class MatrixFederationAgentTests(unittest.TestCase):
    def setUp(self) -> None:
        self.reactor = ThreadedMemoryReactorClock()

        self.mock_resolver = Mock()

        config_dict = default_config("test", parse=False)
        config_dict["federation_custom_ca_list"] = [get_test_ca_cert_file()]

        self._config = config = HomeServerConfig()
        config.parse_config_dict(config_dict, "", "")

        self.tls_factory = FederationPolicyForHTTPS(config)

        self.well_known_cache: TTLCache[bytes, Optional[bytes]] = TTLCache(
            "test_cache", timer=self.reactor.seconds
        )
        self.had_well_known_cache: TTLCache[bytes, bool] = TTLCache(
            "test_cache", timer=self.reactor.seconds
        )
        self.well_known_resolver = WellKnownResolver(
            self.reactor,
            Agent(self.reactor, contextFactory=self.tls_factory),
            b"test-agent",
            well_known_cache=self.well_known_cache,
            had_well_known_cache=self.had_well_known_cache,
        )

    def _make_connection(
        self,
        client_factory: IProtocolFactory,
        ssl: bool = True,
        expected_sni: Optional[bytes] = None,
        tls_sanlist: Optional[List[bytes]] = None,
    ) -> HTTPChannel:
        """Builds a test server, and completes the outgoing client connection
        Args:
            client_factory: the the factory that the
                application is trying to use to make the outbound connection. We will
                invoke it to build the client Protocol

            ssl: If true, we will expect an ssl connection and wrap
                server_factory with a TLSMemoryBIOFactory
                False is set only for when proxy expect http connection.
                Otherwise federation requests use always https.

            expected_sni: the expected SNI value

            tls_sanlist: list of SAN entries for the TLS cert presented by the server.

        Returns:
            the server Protocol returned by server_factory
        """

        # build the test server
        server_factory = _get_test_protocol_factory()
        if ssl:
            server_factory = _wrap_server_factory_for_tls(server_factory, tls_sanlist)

        server_protocol = server_factory.buildProtocol(dummy_address)
        assert server_protocol is not None
        # now, tell the client protocol factory to build the client protocol (it will be a
        # _WrappingProtocol, around a TLSMemoryBIOProtocol, around an
        # HTTP11ClientProtocol) and wire the output of said protocol up to the server via
        # a FakeTransport.
        #
        # Normally this would be done by the TCP socket code in Twisted, but we are
        # stubbing that out here.
        # NB: we use a checked_cast here to workaround https://github.com/Shoobx/mypy-zope/issues/91)
        client_protocol = checked_cast(
            _WrappingProtocol, client_factory.buildProtocol(dummy_address)
        )
        client_protocol.makeConnection(
            FakeTransport(server_protocol, self.reactor, client_protocol)
        )

        # tell the server protocol to send its stuff back to the client, too
        server_protocol.makeConnection(
            FakeTransport(client_protocol, self.reactor, server_protocol)
        )

        if ssl:
            assert isinstance(server_protocol, TLSMemoryBIOProtocol)
            # fish the test server back out of the server-side TLS protocol.
            http_protocol = server_protocol.wrappedProtocol
            # grab a hold of the TLS connection, in case it gets torn down
            tls_connection = server_protocol._tlsConnection
        else:
            http_protocol = server_protocol
            tls_connection = None

        assert isinstance(http_protocol, HTTPChannel)
        # give the reactor a pump to get the TLS juices flowing (if needed)
        self.reactor.advance(0)

        # check the SNI
        if expected_sni is not None:
            server_name = tls_connection.get_servername()
            self.assertEqual(
                server_name,
                expected_sni,
                f"Expected SNI {expected_sni!s} but got {server_name!s}",
            )

        return http_protocol

    @defer.inlineCallbacks
    def _make_get_request(
        self, uri: bytes
    ) -> Generator["Deferred[object]", object, IResponse]:
        """
        Sends a simple GET request via the agent, and checks its logcontext management
        """
        with LoggingContext("one") as context:
            fetch_d: Deferred[IResponse] = self.agent.request(b"GET", uri)

            # Nothing happened yet
            self.assertNoResult(fetch_d)

            # should have reset logcontext to the sentinel
            _check_logcontext(SENTINEL_CONTEXT)

            fetch_res: IResponse
            try:
                fetch_res = yield fetch_d  # type: ignore[misc, assignment]
                return fetch_res
            except Exception as e:
                logger.info("Fetch of %s failed: %s", uri.decode("ascii"), e)
                raise
            finally:
                _check_logcontext(context)

    def _handle_well_known_connection(
        self,
        client_factory: IProtocolFactory,
        expected_sni: bytes,
        content: bytes,
        response_headers: Optional[dict] = None,
    ) -> HTTPChannel:
        """Handle an outgoing HTTPs connection: wire it up to a server, check that the
        request is for a .well-known, and send the response.

        Args:
            client_factory: outgoing connection
            expected_sni: SNI that we expect the outgoing connection to send
            content: content to send back as the .well-known
        Returns:
            server impl
        """
        # make the connection for .well-known
        well_known_server = self._make_connection(
            client_factory, expected_sni=expected_sni
        )
        # check the .well-known request and send a response
        self.assertEqual(len(well_known_server.requests), 1)
        request = well_known_server.requests[0]
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"user-agent"), [b"test-agent"]
        )
        self._send_well_known_response(request, content, headers=response_headers or {})
        return well_known_server

    def _send_well_known_response(
        self,
        request: Request,
        content: bytes,
        headers: Optional[dict] = None,
    ) -> None:
        """Check that an incoming request looks like a valid .well-known request, and
        send back the response.
        """
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/.well-known/matrix/server")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"testserv"])
        # send back a response
        for k, v in (headers or {}).items():
            request.setHeader(k, v)
        request.write(content)
        request.finish()

        self.reactor.pump((0.1,))

    def _make_agent(self) -> MatrixFederationAgent:
        """
        If a proxy server is set, the MatrixFederationAgent must be created again
        because it is created too early during setUp
        """
        return MatrixFederationAgent(
            reactor=cast(ISynapseReactor, self.reactor),
            tls_client_options_factory=self.tls_factory,
            user_agent=b"test-agent",  # Note that this is unused since _well_known_resolver is provided.
            ip_whitelist=IPSet(),
            ip_blacklist=IPSet(),
            _srv_resolver=self.mock_resolver,
            _well_known_resolver=self.well_known_resolver,
        )

    def test_get(self) -> None:
        """happy-path test of a GET request with an explicit port"""
        self._do_get()

    @patch.dict(
        os.environ,
        {"https_proxy": "proxy.com", "no_proxy": "testserv"},
    )
    def test_get_bypass_proxy(self) -> None:
        """test of a GET request with an explicit port and bypass proxy"""
        self._do_get()

    def _do_get(self) -> None:
        """test of a GET request with an explicit port"""
        self.agent = self._make_agent()

        self.reactor.lookups["testserv"] = "1.2.3.4"
        test_d = self._make_get_request(b"matrix://testserv:8448/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=b"testserv")

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"testserv:8448"]
        )
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"user-agent"), [b"test-agent"]
        )
        content = request.content.read()
        self.assertEqual(content, b"")

        # Deferred is still without a result
        self.assertNoResult(test_d)

        # send the headers
        request.responseHeaders.setRawHeaders(b"Content-Type", [b"application/json"])
        request.write("")

        self.reactor.pump((0.1,))

        response = self.successResultOf(test_d)

        # that should give us a Response object
        self.assertEqual(response.code, 200)

        # Send the body
        request.write(b'{ "a": 1 }')
        request.finish()

        self.reactor.pump((0.1,))

        # check it can be read
        json = self.successResultOf(treq.json_content(response))
        self.assertEqual(json, {"a": 1})

    @patch.dict(
        os.environ, {"https_proxy": "http://proxy.com", "no_proxy": "unused.com"}
    )
    def test_get_via_http_proxy(self) -> None:
        """test for federation request through a http proxy"""
        self._do_get_via_proxy(expect_proxy_ssl=False, expected_auth_credentials=None)

    @patch.dict(
        os.environ,
        {"https_proxy": "http://user:pass@proxy.com", "no_proxy": "unused.com"},
    )
    def test_get_via_http_proxy_with_auth(self) -> None:
        """test for federation request through a http proxy with authentication"""
        self._do_get_via_proxy(
            expect_proxy_ssl=False, expected_auth_credentials=b"user:pass"
        )

    @patch.dict(
        os.environ, {"https_proxy": "https://proxy.com", "no_proxy": "unused.com"}
    )
    def test_get_via_https_proxy(self) -> None:
        """test for federation request through a https proxy"""
        self._do_get_via_proxy(expect_proxy_ssl=True, expected_auth_credentials=None)

    @patch.dict(
        os.environ,
        {"https_proxy": "https://user:pass@proxy.com", "no_proxy": "unused.com"},
    )
    def test_get_via_https_proxy_with_auth(self) -> None:
        """test for federation request through a https proxy with authentication"""
        self._do_get_via_proxy(
            expect_proxy_ssl=True, expected_auth_credentials=b"user:pass"
        )

    def _do_get_via_proxy(
        self,
        expect_proxy_ssl: bool = False,
        expected_auth_credentials: Optional[bytes] = None,
    ) -> None:
        """Send a https federation request via an agent and check that it is correctly
            received at the proxy and client. The proxy can use either http or https.
        Args:
            expect_proxy_ssl: True if we expect the request to connect to the proxy via https.
            expected_auth_credentials: credentials we expect to be presented to authenticate at the proxy
        """
        self.agent = self._make_agent()

        self.reactor.lookups["testserv"] = "1.2.3.4"
        self.reactor.lookups["proxy.com"] = "9.9.9.9"
        test_d = self._make_get_request(b"matrix://testserv:8448/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        # make sure we are connecting to the proxy
        self.assertEqual(host, "9.9.9.9")
        self.assertEqual(port, 1080)

        # make a test server to act as the proxy, and wire up the client
        proxy_server = self._make_connection(
            client_factory,
            ssl=expect_proxy_ssl,
            tls_sanlist=[b"DNS:proxy.com"] if expect_proxy_ssl else None,
            expected_sni=b"proxy.com" if expect_proxy_ssl else None,
        )

        assert isinstance(proxy_server, HTTPChannel)

        # now there should be a pending CONNECT request
        self.assertEqual(len(proxy_server.requests), 1)

        request = proxy_server.requests[0]
        self.assertEqual(request.method, b"CONNECT")
        self.assertEqual(request.path, b"testserv:8448")

        # Check whether auth credentials have been supplied to the proxy
        proxy_auth_header_values = request.requestHeaders.getRawHeaders(
            b"Proxy-Authorization"
        )

        if expected_auth_credentials is not None:
            # Compute the correct header value for Proxy-Authorization
            encoded_credentials = base64.b64encode(expected_auth_credentials)
            expected_header_value = b"Basic " + encoded_credentials

            # Validate the header's value
            self.assertIn(expected_header_value, proxy_auth_header_values)
        else:
            # Check that the Proxy-Authorization header has not been supplied to the proxy
            self.assertIsNone(proxy_auth_header_values)

        # tell the proxy server not to close the connection
        proxy_server.persistent = True

        request.finish()

        # now we make another test server to act as the upstream HTTP server.
        server_ssl_protocol = _wrap_server_factory_for_tls(
            _get_test_protocol_factory()
        ).buildProtocol(dummy_address)

        # Tell the HTTP server to send outgoing traffic back via the proxy's transport.
        proxy_server_transport = proxy_server.transport
        assert proxy_server_transport is not None
        server_ssl_protocol.makeConnection(proxy_server_transport)

        # ... and replace the protocol on the proxy's transport with the
        # TLSMemoryBIOProtocol for the test server, so that incoming traffic
        # to the proxy gets sent over to the HTTP(s) server.

        # See also comment at `_do_https_request_via_proxy`
        # in ../test_proxyagent.py for more details
        if expect_proxy_ssl:
            assert isinstance(proxy_server_transport, TLSMemoryBIOProtocol)
            proxy_server_transport.wrappedProtocol = server_ssl_protocol
        else:
            assert isinstance(proxy_server_transport, FakeTransport)
            client_protocol = proxy_server_transport.other
            c2s_transport = client_protocol.transport
            c2s_transport.other = server_ssl_protocol

        self.reactor.advance(0)

        server_name = server_ssl_protocol._tlsConnection.get_servername()
        expected_sni = b"testserv"
        self.assertEqual(
            server_name,
            expected_sni,
            f"Expected SNI {expected_sni!s} but got {server_name!s}",
        )

        # now there should be a pending request
        http_server = server_ssl_protocol.wrappedProtocol
        assert isinstance(http_server, HTTPChannel)
        self.assertEqual(len(http_server.requests), 1)

        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"testserv:8448"]
        )
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"user-agent"), [b"test-agent"]
        )
        # Check that the destination server DID NOT receive proxy credentials
        self.assertIsNone(request.requestHeaders.getRawHeaders(b"Proxy-Authorization"))
        content = request.content.read()
        self.assertEqual(content, b"")

        # Deferred is still without a result
        self.assertNoResult(test_d)

        # send the headers
        request.responseHeaders.setRawHeaders(b"Content-Type", [b"application/json"])
        request.write("")

        self.reactor.pump((0.1,))

        response = self.successResultOf(test_d)

        # that should give us a Response object
        self.assertEqual(response.code, 200)

        # Send the body
        request.write('{ "a": 1 }'.encode("ascii"))
        request.finish()

        self.reactor.pump((0.1,))

        # check it can be read
        json = self.successResultOf(treq.json_content(response))
        self.assertEqual(json, {"a": 1})

    def test_get_ip_address(self) -> None:
        """
        Test the behaviour when the server name contains an explicit IP (with no port)
        """
        self.agent = self._make_agent()

        # there will be a getaddrinfo on the IP
        self.reactor.lookups["1.2.3.4"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://1.2.3.4/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=None)

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"1.2.3.4"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_get_ipv6_address(self) -> None:
        """
        Test the behaviour when the server name contains an explicit IPv6 address
        (with no port)
        """
        self.agent = self._make_agent()

        # there will be a getaddrinfo on the IP
        self.reactor.lookups["::1"] = "::1"

        test_d = self._make_get_request(b"matrix://[::1]/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "::1")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=None)

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"[::1]"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_get_ipv6_address_with_port(self) -> None:
        """
        Test the behaviour when the server name contains an explicit IPv6 address
        (with explicit port)
        """
        self.agent = self._make_agent()

        # there will be a getaddrinfo on the IP
        self.reactor.lookups["::1"] = "::1"

        test_d = self._make_get_request(b"matrix://[::1]:80/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "::1")
        self.assertEqual(port, 80)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=None)

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"[::1]:80"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_get_hostname_bad_cert(self) -> None:
        """
        Test the behaviour when the certificate on the server doesn't match the hostname
        """
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])
        self.reactor.lookups["testserv1"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://testserv1/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # No SRV record lookup yet
        self.mock_resolver.resolve_service.assert_not_called()

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        # fonx the connection
        client_factory.clientConnectionFailed(None, Exception("nope"))

        # attemptdelay on the hostnameendpoint is 0.3, so takes that long before the
        # .well-known request fails.
        self.reactor.pump((0.4,))

        # now there should be a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.testserv1"
        )

        # we should fall back to a direct connection
        self.assertEqual(len(clients), 2)
        (host, port, client_factory, _timeout, _bindAddress) = clients[1]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=b"testserv1")

        # there should be no requests
        self.assertEqual(len(http_server.requests), 0)

        # ... and the request should have failed
        e = self.failureResultOf(test_d, ResponseNeverReceived)
        failure_reason = e.value.reasons[0]
        self.assertIsInstance(failure_reason.value, VerificationError)

    def test_get_ip_address_bad_cert(self) -> None:
        """
        Test the behaviour when the server name contains an explicit IP, but
        the server cert doesn't cover it
        """
        self.agent = self._make_agent()

        # there will be a getaddrinfo on the IP
        self.reactor.lookups["1.2.3.5"] = "1.2.3.5"

        test_d = self._make_get_request(b"matrix://1.2.3.5/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.5")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=None)

        # there should be no requests
        self.assertEqual(len(http_server.requests), 0)

        # ... and the request should have failed
        e = self.failureResultOf(test_d, ResponseNeverReceived)
        failure_reason = e.value.reasons[0]
        self.assertIsInstance(failure_reason.value, VerificationError)

    def test_get_no_srv_no_well_known(self) -> None:
        """
        Test the behaviour when the server name has no port, no SRV, and no well-known
        """
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])
        self.reactor.lookups["testserv"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # No SRV record lookup yet
        self.mock_resolver.resolve_service.assert_not_called()

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        # fonx the connection
        client_factory.clientConnectionFailed(None, Exception("nope"))

        # attemptdelay on the hostnameendpoint is 0.3, so  takes that long before the
        # .well-known request fails.
        self.reactor.pump((0.4,))

        # now there should be a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.testserv"
        )

        # we should fall back to a direct connection
        self.assertEqual(len(clients), 2)
        (host, port, client_factory, _timeout, _bindAddress) = clients[1]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=b"testserv")

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"testserv"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_get_well_known(self) -> None:
        """Test the behaviour when the .well-known delegates elsewhere"""
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])
        self.reactor.lookups["testserv"] = "1.2.3.4"
        self.reactor.lookups["target-server"] = "1::f"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        self._handle_well_known_connection(
            client_factory,
            expected_sni=b"testserv",
            content=b'{ "m.server": "target-server" }',
        )

        # there should be a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.target-server"
        )

        # now we should get a connection to the target server
        self.assertEqual(len(clients), 2)
        (host, port, client_factory, _timeout, _bindAddress) = clients[1]
        self.assertEqual(host, "1::f")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(
            client_factory, expected_sni=b"target-server"
        )

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"target-server"]
        )

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

        self.assertEqual(self.well_known_cache[b"testserv"], b"target-server")

        # check the cache expires
        self.reactor.pump((48 * 3600,))
        self.well_known_cache.expire()
        self.assertNotIn(b"testserv", self.well_known_cache)

    def test_get_well_known_redirect(self) -> None:
        """Test the behaviour when the server name has no port and no SRV record, but
        the .well-known has a 300 redirect
        """
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])
        self.reactor.lookups["testserv"] = "1.2.3.4"
        self.reactor.lookups["target-server"] = "1::f"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop()
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        redirect_server = self._make_connection(
            client_factory, expected_sni=b"testserv"
        )

        # send a 302 redirect
        self.assertEqual(len(redirect_server.requests), 1)
        request = redirect_server.requests[0]
        request.redirect(b"https://testserv/even_better_known")
        request.finish()

        self.reactor.pump((0.1,))

        # now there should be another connection
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop()
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        well_known_server = self._make_connection(
            client_factory, expected_sni=b"testserv"
        )

        self.assertEqual(len(well_known_server.requests), 1, "No request after 302")
        request = well_known_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/even_better_known")
        request.write(b'{ "m.server": "target-server" }')
        request.finish()

        self.reactor.pump((0.1,))

        # there should be a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.target-server"
        )

        # now we should get a connection to the target server
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1::f")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(
            client_factory, expected_sni=b"target-server"
        )

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"target-server"]
        )

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

        self.assertEqual(self.well_known_cache[b"testserv"], b"target-server")

        # check the cache expires
        self.reactor.pump((48 * 3600,))
        self.well_known_cache.expire()
        self.assertNotIn(b"testserv", self.well_known_cache)

    def test_get_invalid_well_known(self) -> None:
        """
        Test the behaviour when the server name has an *invalid* well-known (and no SRV)
        """
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])
        self.reactor.lookups["testserv"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # No SRV record lookup yet
        self.mock_resolver.resolve_service.assert_not_called()

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop()
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        self._handle_well_known_connection(
            client_factory, expected_sni=b"testserv", content=b"NOT JSON"
        )

        # now there should be a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.testserv"
        )

        # we should fall back to a direct connection
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop()
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=b"testserv")

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"testserv"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_get_well_known_unsigned_cert(self) -> None:
        """Test the behaviour when the .well-known server presents a cert
        not signed by a CA
        """

        # we use the same test server as the other tests, but use an agent with
        # the config left to the default, which will not trust it (since the
        # presented cert is signed by a test CA)

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])
        self.reactor.lookups["testserv"] = "1.2.3.4"

        config = default_config("test", parse=True)

        # Build a new agent and WellKnownResolver with a different tls factory
        tls_factory = FederationPolicyForHTTPS(config)
        agent = MatrixFederationAgent(
            reactor=self.reactor,
            tls_client_options_factory=tls_factory,
            user_agent=b"test-agent",  # This is unused since _well_known_resolver is passed below.
            ip_whitelist=IPSet(),
            ip_blacklist=IPSet(),
            _srv_resolver=self.mock_resolver,
            _well_known_resolver=WellKnownResolver(
                cast(ISynapseReactor, self.reactor),
                Agent(self.reactor, contextFactory=tls_factory),
                b"test-agent",
                well_known_cache=self.well_known_cache,
                had_well_known_cache=self.had_well_known_cache,
            ),
        )

        test_d = agent.request(b"GET", b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        http_proto = self._make_connection(client_factory, expected_sni=b"testserv")

        # there should be no requests
        self.assertEqual(len(http_proto.requests), 0)

        # and there should be a SRV lookup instead
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.testserv"
        )

    def test_get_hostname_srv(self) -> None:
        """
        Test the behaviour when there is a single SRV record
        """
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service(
            [Server(host=b"srvtarget", port=8443)]
        )
        self.reactor.lookups["srvtarget"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # the request for a .well-known will have failed with a DNS lookup error.
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.testserv"
        )

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8443)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=b"testserv")

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"testserv"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_get_well_known_srv(self) -> None:
        """Test the behaviour when the .well-known redirects to a place where there
        is a SRV.
        """
        self.agent = self._make_agent()

        self.reactor.lookups["testserv"] = "1.2.3.4"
        self.reactor.lookups["srvtarget"] = "5.6.7.8"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service(
            [Server(host=b"srvtarget", port=8443)]
        )

        self._handle_well_known_connection(
            client_factory,
            expected_sni=b"testserv",
            content=b'{ "m.server": "target-server" }',
        )

        # there should be a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.target-server"
        )

        # now we should get a connection to the target of the SRV record
        self.assertEqual(len(clients), 2)
        (host, port, client_factory, _timeout, _bindAddress) = clients[1]
        self.assertEqual(host, "5.6.7.8")
        self.assertEqual(port, 8443)

        # make a test server, and wire up the client
        http_server = self._make_connection(
            client_factory, expected_sni=b"target-server"
        )

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"target-server"]
        )

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_idna_servername(self) -> None:
        """test the behaviour when the server name has idna chars in"""
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service([])

        # the resolver is always called with the IDNA hostname as a native string.
        self.reactor.lookups["xn--bcher-kva.com"] = "1.2.3.4"

        # this is idna for bücher.com
        test_d = self._make_get_request(b"matrix://xn--bcher-kva.com/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        # No SRV record lookup yet
        self.mock_resolver.resolve_service.assert_not_called()

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        # fonx the connection
        client_factory.clientConnectionFailed(None, Exception("nope"))

        # attemptdelay on the hostnameendpoint is 0.3, so  takes that long before the
        # .well-known request fails.
        self.reactor.pump((0.4,))

        # now there should have been a SRV lookup
        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.xn--bcher-kva.com"
        )

        # We should fall back to port 8448
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 2)
        (host, port, client_factory, _timeout, _bindAddress) = clients[1]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8448)

        # make a test server, and wire up the client
        http_server = self._make_connection(
            client_factory, expected_sni=b"xn--bcher-kva.com"
        )

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"xn--bcher-kva.com"]
        )

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_idna_srv_target(self) -> None:
        """test the behaviour when the target of a SRV record has idna chars"""
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service(
            [Server(host=b"xn--trget-3qa.com", port=8443)]  # târget.com
        )
        self.reactor.lookups["xn--trget-3qa.com"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://xn--bcher-kva.com/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.xn--bcher-kva.com"
        )

        # Make sure treq is trying to connect
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients[0]
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8443)

        # make a test server, and wire up the client
        http_server = self._make_connection(
            client_factory, expected_sni=b"xn--bcher-kva.com"
        )

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(
            request.requestHeaders.getRawHeaders(b"host"), [b"xn--bcher-kva.com"]
        )

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)

    def test_well_known_cache(self) -> None:
        self.reactor.lookups["testserv"] = "1.2.3.4"

        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        well_known_server = self._handle_well_known_connection(
            client_factory,
            expected_sni=b"testserv",
            response_headers={b"Cache-Control": b"max-age=1000"},
            content=b'{ "m.server": "target-server" }',
        )

        r = self.successResultOf(fetch_d)
        self.assertEqual(r.delegated_server, b"target-server")

        # close the tcp connection
        well_known_server.loseConnection()

        # repeat the request: it should hit the cache
        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )
        r = self.successResultOf(fetch_d)
        self.assertEqual(r.delegated_server, b"target-server")

        # expire the cache
        self.reactor.pump((1000.0,))

        # now it should connect again
        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )

        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        self._handle_well_known_connection(
            client_factory,
            expected_sni=b"testserv",
            content=b'{ "m.server": "other-server" }',
        )

        r = self.successResultOf(fetch_d)
        self.assertEqual(r.delegated_server, b"other-server")

    def test_well_known_cache_with_temp_failure(self) -> None:
        """Test that we refetch well-known before the cache expires, and that
        it ignores transient errors.
        """

        self.reactor.lookups["testserv"] = "1.2.3.4"

        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        well_known_server = self._handle_well_known_connection(
            client_factory,
            expected_sni=b"testserv",
            response_headers={b"Cache-Control": b"max-age=1000"},
            content=b'{ "m.server": "target-server" }',
        )

        r = self.successResultOf(fetch_d)
        self.assertEqual(r.delegated_server, b"target-server")

        # close the tcp connection
        well_known_server.loseConnection()

        # Get close to the cache expiry, this will cause the resolver to do
        # another lookup.
        self.reactor.pump((900.0,))

        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )

        # The resolver may retry a few times, so fonx all requests that come along
        attempts = 0
        while self.reactor.tcpClients:
            clients = self.reactor.tcpClients
            (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)

            attempts += 1

            # fonx the connection attempt, this will be treated as a temporary
            # failure.
            client_factory.clientConnectionFailed(None, Exception("nope"))

            # There's a few sleeps involved, so we have to pump the reactor a
            # bit.
            self.reactor.pump((1.0, 1.0))

        # We expect to see more than one attempt as there was previously a valid
        # well known.
        self.assertGreater(attempts, 1)

        # Resolver should return cached value, despite the lookup failing.
        r = self.successResultOf(fetch_d)
        self.assertEqual(r.delegated_server, b"target-server")

        # Expire both caches and repeat the request
        self.reactor.pump((10000.0,))

        # Repeat the request, this time it should fail if the lookup fails.
        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )

        clients = self.reactor.tcpClients
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        client_factory.clientConnectionFailed(None, Exception("nope"))
        self.reactor.pump((0.4,))

        r = self.successResultOf(fetch_d)
        self.assertEqual(r.delegated_server, None)

    def test_well_known_too_large(self) -> None:
        """A well-known query that returns a result which is too large should be rejected."""
        self.reactor.lookups["testserv"] = "1.2.3.4"

        fetch_d = defer.ensureDeferred(
            self.well_known_resolver.get_well_known(b"testserv")
        )

        # there should be an attempt to connect on port 443 for the .well-known
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 443)

        self._handle_well_known_connection(
            client_factory,
            expected_sni=b"testserv",
            response_headers={b"Cache-Control": b"max-age=1000"},
            content=b'{ "m.server": "' + (b"a" * WELL_KNOWN_MAX_SIZE) + b'" }',
        )

        # The result is successful, but disabled delegation.
        r = self.successResultOf(fetch_d)
        self.assertIsNone(r.delegated_server)

    def test_srv_fallbacks(self) -> None:
        """Test that other SRV results are tried if the first one fails."""
        self.agent = self._make_agent()

        self.mock_resolver.resolve_service.side_effect = generate_resolve_service(
            [
                Server(host=b"target.com", port=8443),
                Server(host=b"target.com", port=8444),
            ]
        )
        self.reactor.lookups["target.com"] = "1.2.3.4"

        test_d = self._make_get_request(b"matrix://testserv/foo/bar")

        # Nothing happened yet
        self.assertNoResult(test_d)

        self.mock_resolver.resolve_service.assert_called_once_with(
            b"_matrix._tcp.testserv"
        )

        # We should see an attempt to connect to the first server
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8443)

        # Fonx the connection
        client_factory.clientConnectionFailed(None, Exception("nope"))

        # There's a 300ms delay in HostnameEndpoint
        self.reactor.pump((0.4,))

        # Hasn't failed yet
        self.assertNoResult(test_d)

        # We shouldnow see an attempt to connect to the second server
        clients = self.reactor.tcpClients
        self.assertEqual(len(clients), 1)
        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
        self.assertEqual(host, "1.2.3.4")
        self.assertEqual(port, 8444)

        # make a test server, and wire up the client
        http_server = self._make_connection(client_factory, expected_sni=b"testserv")

        self.assertEqual(len(http_server.requests), 1)
        request = http_server.requests[0]
        self.assertEqual(request.method, b"GET")
        self.assertEqual(request.path, b"/foo/bar")
        self.assertEqual(request.requestHeaders.getRawHeaders(b"host"), [b"testserv"])

        # finish the request
        request.finish()
        self.reactor.pump((0.1,))
        self.successResultOf(test_d)


class TestCachePeriodFromHeaders(unittest.TestCase):
    def test_cache_control(self) -> None:
        # uppercase
        self.assertEqual(
            _cache_period_from_headers(
                Headers({b"Cache-Control": [b"foo, Max-Age = 100, bar"]})
            ),
            100,
        )

        # missing value
        self.assertIsNone(
            _cache_period_from_headers(Headers({b"Cache-Control": [b"max-age=, bar"]}))
        )

        # hackernews: bogus due to semicolon
        self.assertIsNone(
            _cache_period_from_headers(
                Headers({b"Cache-Control": [b"private; max-age=0"]})
            )
        )

        # github
        self.assertEqual(
            _cache_period_from_headers(
                Headers({b"Cache-Control": [b"max-age=0, private, must-revalidate"]})
            ),
            0,
        )

        # google
        self.assertEqual(
            _cache_period_from_headers(
                Headers({b"cache-control": [b"private, max-age=0"]})
            ),
            0,
        )

    def test_expires(self) -> None:
        self.assertEqual(
            _cache_period_from_headers(
                Headers({b"Expires": [b"Wed, 30 Jan 2019 07:35:33 GMT"]}),
                time_now=lambda: 1548833700,
            ),
            33,
        )

        # cache-control overrides expires
        self.assertEqual(
            _cache_period_from_headers(
                Headers(
                    {
                        b"cache-control": [b"max-age=10"],
                        b"Expires": [b"Wed, 30 Jan 2019 07:35:33 GMT"],
                    }
                ),
                time_now=lambda: 1548833700,
            ),
            10,
        )

        # invalid expires means immediate expiry
        self.assertEqual(_cache_period_from_headers(Headers({b"Expires": [b"0"]})), 0)


def _check_logcontext(context: LoggingContextOrSentinel) -> None:
    current = current_context()
    if current is not context:
        raise AssertionError("Expected logcontext %s but was %s" % (context, current))


def _wrap_server_factory_for_tls(
    factory: IProtocolFactory, sanlist: Optional[List[bytes]] = None
) -> TLSMemoryBIOFactory:
    """Wrap an existing Protocol Factory with a test TLSMemoryBIOFactory
    The resultant factory will create a TLS server which presents a certificate
    signed by our test CA, valid for the domains in `sanlist`
    Args:
        factory: protocol factory to wrap
        sanlist: list of domains the cert should be valid for
    Returns:
        interfaces.IProtocolFactory
    """
    if sanlist is None:
        sanlist = [
            b"DNS:testserv",
            b"DNS:target-server",
            b"DNS:xn--bcher-kva.com",
            b"IP:1.2.3.4",
            b"IP:::1",
        ]

    connection_creator = TestServerTLSConnectionFactory(sanlist=sanlist)
    return TLSMemoryBIOFactory(
        connection_creator, isClient=False, wrappedFactory=factory
    )


def _get_test_protocol_factory() -> IProtocolFactory:
    """Get a protocol Factory which will build an HTTPChannel
    Returns:
        interfaces.IProtocolFactory
    """
    server_factory = Factory.forProtocol(HTTPChannel)

    # Request.finish expects the factory to have a 'log' method.
    server_factory.log = _log_request

    return server_factory


def _log_request(request: str) -> None:
    """Implements Factory.log, which is expected by Request.finish"""
    logger.info(f"Completed request {request}")


@implementer(IPolicyForHTTPS)
class TrustingTLSPolicyForHTTPS:
    """An IPolicyForHTTPS which checks that the certificate belongs to the
    right server, but doesn't check the certificate chain."""

    def creatorForNetloc(
        self, hostname: bytes, port: int
    ) -> IOpenSSLClientConnectionCreator:
        certificateOptions = OpenSSLCertificateOptions()
        return ClientTLSOptions(hostname, certificateOptions.getContext())