forked-synapse/tests/http/federation/test_matrix_federation_agent.py

# -*- coding: utf-8 -*-
# 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 logging
from typing import Optional

from mock import Mock

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.protocol import Factory
from twisted.protocols.tls import TLSMemoryBIOFactory
from twisted.web._newclient import ResponseNeverReceived
from twisted.web.client import Agent
from twisted.web.http import HTTPChannel
from twisted.web.http_headers import Headers
from twisted.web.iweb import IPolicyForHTTPS

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, current_context
from synapse.util.caches.ttlcache import TTLCache

from tests import unittest
from tests.http import TestServerTLSConnectionFactory, get_test_ca_cert_file
from tests.server import FakeTransport, ThreadedMemoryReactorClock
from tests.utils import default_config

logger = logging.getLogger(__name__)

test_server_connection_factory = None


def get_connection_factory():
    # this needs to happen once, but not until we are ready to run the first test
    global test_server_connection_factory
    if test_server_connection_factory is None:
        test_server_connection_factory = TestServerTLSConnectionFactory(
            sanlist=[
                b"DNS:testserv",
                b"DNS:target-server",
                b"DNS:xn--bcher-kva.com",
                b"IP:1.2.3.4",
                b"IP:::1",
            ]
        )
    return test_server_connection_factory


# Once Async Mocks or lambdas are supported this can go away.
def generate_resolve_service(result):
    async def resolve_service(_):
        return result

    return resolve_service


class MatrixFederationAgentTests(unittest.TestCase):
    def setUp(self):
        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("test_cache", timer=self.reactor.seconds)
        self.had_well_known_cache = 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,
        )

        self.agent = MatrixFederationAgent(
            reactor=self.reactor,
            tls_client_options_factory=self.tls_factory,
            user_agent="test-agent",  # Note that this is unused since _well_known_resolver is provided.
            ip_blacklist=IPSet(),
            _srv_resolver=self.mock_resolver,
            _well_known_resolver=self.well_known_resolver,
        )

    def _make_connection(self, client_factory, expected_sni):
        """Builds a test server, and completes the outgoing client connection

        Returns:
            HTTPChannel: the test server
        """

        # build the test server
        server_tls_protocol = _build_test_server(get_connection_factory())

        # 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.
        client_protocol = client_factory.buildProtocol(None)
        client_protocol.makeConnection(
            FakeTransport(server_tls_protocol, self.reactor, client_protocol)
        )

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

        # grab a hold of the TLS connection, in case it gets torn down
        server_tls_connection = server_tls_protocol._tlsConnection

        # fish the test server back out of the server-side TLS protocol.
        http_protocol = server_tls_protocol.wrappedProtocol

        # give the reactor a pump to get the TLS juices flowing.
        self.reactor.pump((0.1,))

        # check the SNI
        server_name = server_tls_connection.get_servername()
        self.assertEqual(
            server_name,
            expected_sni,
            "Expected SNI %s but got %s" % (expected_sni, server_name),
        )

        return http_protocol

    @defer.inlineCallbacks
    def _make_get_request(self, uri):
        """
        Sends a simple GET request via the agent, and checks its logcontext management
        """
        with LoggingContext("one") as context:
            fetch_d = self.agent.request(b"GET", uri)

            # Nothing happened yet
            self.assertNoResult(fetch_d)

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

            try:
                fetch_res = yield fetch_d
                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,
        expected_sni,
        content,
        response_headers: Optional[dict] = None,
    ):
        """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 (IProtocolFactory): outgoing connection
            expected_sni (bytes): SNI that we expect the outgoing connection to send
            content (bytes): content to send back as the .well-known
        Returns:
            HTTPChannel: 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, content, headers: Optional[dict] = 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 test_get(self):
        """
        happy-path test of a GET request with an explicit port
        """
        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('{ "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):
        """
        Test the behaviour when the server name contains an explicit IP (with no port)
        """
        # 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):
        """
        Test the behaviour when the server name contains an explicit IPv6 address
        (with no port)
        """

        # 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):
        """
        Test the behaviour when the server name contains an explicit IPv6 address
        (with explicit port)
        """

        # 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):
        """
        Test the behaviour when the certificate on the server doesn't match the hostname
        """
        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):
        """
        Test the behaviour when the server name contains an explicit IP, but
        the server cert doesn't cover it
        """
        # 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):
        """
        Test the behaviour when the server name has no port, no SRV, and no well-known
        """

        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):
        """Test the behaviour when the .well-known delegates elsewhere"""

        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):
        """Test the behaviour when the server name has no port and no SRV record, but
        the .well-known has a 300 redirect
        """
        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):
        """
        Test the behaviour when the server name has an *invalid* well-known (and no SRV)
        """

        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):
        """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_blacklist=IPSet(),
            _srv_resolver=self.mock_resolver,
            _well_known_resolver=WellKnownResolver(
                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):
        """
        Test the behaviour when there is a single SRV record
        """
        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):
        """Test the behaviour when the .well-known redirects to a place where there
        is a SRV.
        """
        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):
        """test the behaviour when the server name has idna chars in"""

        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):
        """test the behaviour when the target of a SRV record has idna chars"""

        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):
        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):
        """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):
        """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):
        """Test that other SRV results are tried if the first one fails."""
        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):
        # 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):
        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):
    current = current_context()
    if current is not context:
        raise AssertionError("Expected logcontext %s but was %s" % (context, current))


def _build_test_server(connection_creator):
    """Construct a test server

    This builds an HTTP channel, wrapped with a TLSMemoryBIOProtocol

    Args:
        connection_creator (IOpenSSLServerConnectionCreator): thing to build
            SSL connections
        sanlist (list[bytes]): list of the SAN entries for the cert returned
            by the server

    Returns:
        TLSMemoryBIOProtocol
    """
    server_factory = Factory.forProtocol(HTTPChannel)
    # Request.finish expects the factory to have a 'log' method.
    server_factory.log = _log_request

    server_tls_factory = TLSMemoryBIOFactory(
        connection_creator, isClient=False, wrappedFactory=server_factory
    )

    return server_tls_factory.buildProtocol(None)


def _log_request(request):
    """Implements Factory.log, which is expected by Request.finish"""
    logger.info("Completed request %s", 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, port):
        certificateOptions = OpenSSLCertificateOptions()
        return ClientTLSOptions(hostname, certificateOptions.getContext())