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-rw-r--r--.circleci/config.yml4
-rw-r--r--.coveragerc1
-rw-r--r--.gitignore2
-rw-r--r--README.rst11
-rw-r--r--changelog.d/4215.misc1
-rw-r--r--changelog.d/4298.feature1
-rw-r--r--changelog.d/4313.bugfix1
-rw-r--r--changelog.d/4315.feature1
-rw-r--r--changelog.d/4316.bugfix1
-rwxr-xr-xscripts/generate_config67
-rwxr-xr-xsetup.py16
-rw-r--r--synapse/app/__init__.py6
-rwxr-xr-xsynapse/app/homeserver.py3
-rw-r--r--synapse/config/_base.py56
-rw-r--r--synapse/config/database.py5
-rw-r--r--synapse/config/homeserver.py7
-rw-r--r--synapse/config/key.py27
-rw-r--r--synapse/config/logger.py4
-rw-r--r--synapse/config/metrics.py12
-rw-r--r--synapse/config/registration.py11
-rw-r--r--synapse/config/repository.py8
-rw-r--r--synapse/config/server.py75
-rw-r--r--synapse/http/client.py377
-rw-r--r--synapse/http/endpoint.py35
-rw-r--r--synapse/python_dependencies.py228
-rw-r--r--synapse/rest/media/v1/preview_url_resource.py14
-rw-r--r--tests/rest/media/v1/test_url_preview.py424
-rw-r--r--tests/server.py8
-rw-r--r--tox.ini4
29 files changed, 897 insertions, 513 deletions
diff --git a/.circleci/config.yml b/.circleci/config.yml
index d4aafd4b2c..697e6c577f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -13,8 +13,8 @@ jobs:
     machine: true
     steps:
       - checkout
-      - run: docker build -f docker/Dockerfile --label gitsha1=${CIRCLE_SHA1} -t matrixdotorg/synapse:${CIRCLE_SHA1} .
-      - run: docker build -f docker/Dockerfile --label gitsha1=${CIRCLE_SHA1} -t matrixdotorg/synapse:${CIRCLE_SHA1}-py3 --build-arg PYTHON_VERSION=3.6 .
+      - run: docker build -f docker/Dockerfile --label gitsha1=${CIRCLE_SHA1} -t matrixdotorg/synapse:latest .
+      - run: docker build -f docker/Dockerfile --label gitsha1=${CIRCLE_SHA1} -t matrixdotorg/synapse:latest-py3 --build-arg PYTHON_VERSION=3.6 .
       - run: docker login --username $DOCKER_HUB_USERNAME --password $DOCKER_HUB_PASSWORD
       - run: docker push matrixdotorg/synapse:latest
       - run: docker push matrixdotorg/synapse:latest-py3
diff --git a/.coveragerc b/.coveragerc
index ca333961f3..9873a30738 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -9,4 +9,3 @@ source=
 
 [report]
 precision = 2
-ignore_errors = True
diff --git a/.gitignore b/.gitignore
index 1b632646bb..d739595c3a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,7 +59,5 @@ env/
 
 .vscode/
 .ropeproject/
-
 *.deb
-
 /debs
diff --git a/README.rst b/README.rst
index 02b3db1bc6..c4df779ac7 100644
--- a/README.rst
+++ b/README.rst
@@ -86,7 +86,7 @@ Synapse is the reference Python/Twisted Matrix homeserver implementation.
 System requirements:
 
 - POSIX-compliant system (tested on Linux & OS X)
-- Python 3.5, 3.6, or 2.7
+- Python 3.5, 3.6, 3.7, or 2.7
 - At least 1GB of free RAM if you want to join large public rooms like #matrix:matrix.org
 
 Installing from source
@@ -148,7 +148,7 @@ To install the Synapse homeserver run::
     source ~/synapse/env/bin/activate
     pip install --upgrade pip
     pip install --upgrade setuptools
-    pip install matrix-synapse
+    pip install matrix-synapse[all]
 
 This installs Synapse, along with the libraries it uses, into a virtual
 environment under ``~/synapse/env``.  Feel free to pick a different directory
@@ -158,7 +158,7 @@ This Synapse installation can then be later upgraded by using pip again with the
 update flag::
 
     source ~/synapse/env/bin/activate
-    pip install -U matrix-synapse
+    pip install -U matrix-synapse[all]
 
 In case of problems, please see the _`Troubleshooting` section below.
 
@@ -826,8 +826,7 @@ to install using pip and a virtualenv::
 
     virtualenv -p python2.7 env
     source env/bin/activate
-    python -m synapse.python_dependencies | xargs pip install
-    pip install lxml mock
+    python -m pip install -e .[all]
 
 This will run a process of downloading and installing all the needed
 dependencies into a virtual env.
@@ -835,7 +834,7 @@ dependencies into a virtual env.
 Once this is done, you may wish to run Synapse's unit tests, to
 check that everything is installed as it should be::
 
-    PYTHONPATH="." trial tests
+    python -m twisted.trial tests
 
 This should end with a 'PASSED' result::
 
diff --git a/changelog.d/4215.misc b/changelog.d/4215.misc
new file mode 100644
index 0000000000..bb90594836
--- /dev/null
+++ b/changelog.d/4215.misc
@@ -0,0 +1 @@
+Getting URL previews of IP addresses no longer fails on Python 3.
diff --git a/changelog.d/4298.feature b/changelog.d/4298.feature
new file mode 100644
index 0000000000..05ad70fe72
--- /dev/null
+++ b/changelog.d/4298.feature
@@ -0,0 +1 @@
+Synapse can now have its conditional/extra dependencies installed by pip. This functionality can be used by using `pip install matrix-synapse[feature]`, where feature is a comma separated list with the possible values "email.enable_notifs", "ldap3", "postgres", "saml2", "url_preview", and "test". If you want to install all optional dependencies, you can use "all" instead.
diff --git a/changelog.d/4313.bugfix b/changelog.d/4313.bugfix
new file mode 100644
index 0000000000..d10685dd62
--- /dev/null
+++ b/changelog.d/4313.bugfix
@@ -0,0 +1 @@
+Fix indentation in default config
diff --git a/changelog.d/4315.feature b/changelog.d/4315.feature
new file mode 100644
index 0000000000..23e82fd02d
--- /dev/null
+++ b/changelog.d/4315.feature
@@ -0,0 +1 @@
+Add a script to generate a clean config file
diff --git a/changelog.d/4316.bugfix b/changelog.d/4316.bugfix
new file mode 100644
index 0000000000..bd152dc371
--- /dev/null
+++ b/changelog.d/4316.bugfix
@@ -0,0 +1 @@
+Fix synapse:latest docker upload
diff --git a/scripts/generate_config b/scripts/generate_config
new file mode 100755
index 0000000000..61c5f049e8
--- /dev/null
+++ b/scripts/generate_config
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+
+import argparse
+import sys
+
+from synapse.config.homeserver import HomeServerConfig
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--config-dir",
+        default="CONFDIR",
+
+        help="The path where the config files are kept. Used to create filenames for "
+             "things like the log config and the signing key. Default: %(default)s",
+    )
+
+    parser.add_argument(
+        "--data-dir",
+        default="DATADIR",
+        help="The path where the data files are kept. Used to create filenames for "
+             "things like the database and media store. Default: %(default)s",
+    )
+
+    parser.add_argument(
+        "--server-name",
+        default="SERVERNAME",
+        help="The server name. Used to initialise the server_name config param, but also "
+             "used in the names of some of the config files. Default: %(default)s",
+    )
+
+    parser.add_argument(
+        "--report-stats",
+        action="store",
+        help="Whether the generated config reports anonymized usage statistics",
+        choices=["yes", "no"],
+    )
+
+    parser.add_argument(
+        "--generate-secrets",
+        action="store_true",
+        help="Enable generation of new secrets for things like the macaroon_secret_key."
+             "By default, these parameters will be left unset."
+    )
+
+    parser.add_argument(
+        "-o", "--output-file",
+        type=argparse.FileType('w'),
+        default=sys.stdout,
+        help="File to write the configuration to. Default: stdout",
+    )
+
+    args = parser.parse_args()
+
+    report_stats = args.report_stats
+    if report_stats is not None:
+        report_stats = report_stats == "yes"
+
+    conf = HomeServerConfig().generate_config(
+        config_dir_path=args.config_dir,
+        data_dir_path=args.data_dir,
+        server_name=args.server_name,
+        generate_secrets=args.generate_secrets,
+        report_stats=report_stats,
+    )
+
+    args.output_file.write(conf)
diff --git a/setup.py b/setup.py
index 00b69c43f5..55b1b10a77 100755
--- a/setup.py
+++ b/setup.py
@@ -84,13 +84,25 @@ version = exec_file(("synapse", "__init__.py"))["__version__"]
 dependencies = exec_file(("synapse", "python_dependencies.py"))
 long_description = read_file(("README.rst",))
 
+REQUIREMENTS = dependencies['REQUIREMENTS']
+CONDITIONAL_REQUIREMENTS = dependencies['CONDITIONAL_REQUIREMENTS']
+
+# Make `pip install matrix-synapse[all]` install all the optional dependencies.
+ALL_OPTIONAL_REQUIREMENTS = set()
+
+for optional_deps in CONDITIONAL_REQUIREMENTS.values():
+    ALL_OPTIONAL_REQUIREMENTS = set(optional_deps) | ALL_OPTIONAL_REQUIREMENTS
+
+CONDITIONAL_REQUIREMENTS["all"] = list(ALL_OPTIONAL_REQUIREMENTS)
+
+
 setup(
     name="matrix-synapse",
     version=version,
     packages=find_packages(exclude=["tests", "tests.*"]),
     description="Reference homeserver for the Matrix decentralised comms protocol",
-    install_requires=dependencies['requirements'](include_conditional=True).keys(),
-    dependency_links=dependencies["DEPENDENCY_LINKS"].values(),
+    install_requires=REQUIREMENTS,
+    extras_require=CONDITIONAL_REQUIREMENTS,
     include_package_data=True,
     zip_safe=False,
     long_description=long_description,
diff --git a/synapse/app/__init__.py b/synapse/app/__init__.py
index c3afcc573b..233bf43fc8 100644
--- a/synapse/app/__init__.py
+++ b/synapse/app/__init__.py
@@ -22,11 +22,11 @@ sys.dont_write_bytecode = True
 
 try:
     python_dependencies.check_requirements()
-except python_dependencies.MissingRequirementError as e:
+except python_dependencies.DependencyException as e:
     message = "\n".join([
-        "Missing Requirement: %s" % (str(e),),
+        "Missing Requirements: %s" % (", ".join(e.dependencies),),
         "To install run:",
-        "    pip install --upgrade --force \"%s\"" % (e.dependency,),
+        "    pip install --upgrade --force %s" % (" ".join(e.dependencies),),
         "",
     ])
     sys.stderr.writelines(message)
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index f2064f9d0c..f3ac3d19f0 100755
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -322,9 +322,6 @@ def setup(config_options):
 
     synapse.config.logger.setup_logging(config, use_worker_options=False)
 
-    # check any extra requirements we have now we have a config
-    check_requirements(config)
-
     events.USE_FROZEN_DICTS = config.use_frozen_dicts
 
     tls_server_context_factory = context_factory.ServerContextFactory(config)
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 14dae65ea0..fd2d6d52ef 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -135,10 +135,6 @@ class Config(object):
             return file_stream.read()
 
     @staticmethod
-    def default_path(name):
-        return os.path.abspath(os.path.join(os.path.curdir, name))
-
-    @staticmethod
     def read_config_file(file_path):
         with open(file_path) as file_stream:
             return yaml.load(file_stream)
@@ -151,8 +147,39 @@ class Config(object):
         return results
 
     def generate_config(
-        self, config_dir_path, server_name, is_generating_file, report_stats=None
+        self,
+        config_dir_path,
+        data_dir_path,
+        server_name,
+        generate_secrets=False,
+        report_stats=None,
     ):
+        """Build a default configuration file
+
+        This is used both when the user explicitly asks us to generate a config file
+        (eg with --generate_config), and before loading the config at runtime (to give
+        a base which the config files override)
+
+        Args:
+            config_dir_path (str): The path where the config files are kept. Used to
+                create filenames for things like the log config and the signing key.
+
+            data_dir_path (str): The path where the data files are kept. Used to create
+                filenames for things like the database and media store.
+
+            server_name (str): The server name. Used to initialise the server_name
+                config param, but also used in the names of some of the config files.
+
+            generate_secrets (bool): True if we should generate new secrets for things
+                like the macaroon_secret_key. If False, these parameters will be left
+                unset.
+
+            report_stats (bool|None): Initial setting for the report_stats setting.
+                If None, report_stats will be left unset.
+
+        Returns:
+            str: the yaml config file
+        """
         default_config = "# vim:ft=yaml\n"
 
         default_config += "\n\n".join(
@@ -160,15 +187,14 @@ class Config(object):
             for conf in self.invoke_all(
                 "default_config",
                 config_dir_path=config_dir_path,
+                data_dir_path=data_dir_path,
                 server_name=server_name,
-                is_generating_file=is_generating_file,
+                generate_secrets=generate_secrets,
                 report_stats=report_stats,
             )
         )
 
-        config = yaml.load(default_config)
-
-        return default_config, config
+        return default_config
 
     @classmethod
     def load_config(cls, description, argv):
@@ -274,12 +300,14 @@ class Config(object):
                 if not cls.path_exists(config_dir_path):
                     os.makedirs(config_dir_path)
                 with open(config_path, "w") as config_file:
-                    config_str, config = obj.generate_config(
+                    config_str = obj.generate_config(
                         config_dir_path=config_dir_path,
+                        data_dir_path=os.getcwd(),
                         server_name=server_name,
                         report_stats=(config_args.report_stats == "yes"),
-                        is_generating_file=True,
+                        generate_secrets=True,
                     )
+                    config = yaml.load(config_str)
                     obj.invoke_all("generate_files", config)
                     config_file.write(config_str)
                 print(
@@ -350,11 +378,13 @@ class Config(object):
             raise ConfigError(MISSING_SERVER_NAME)
 
         server_name = specified_config["server_name"]
-        _, config = self.generate_config(
+        config_string = self.generate_config(
             config_dir_path=config_dir_path,
+            data_dir_path=os.getcwd(),
             server_name=server_name,
-            is_generating_file=False,
+            generate_secrets=False,
         )
+        config = yaml.load(config_string)
         config.pop("log_config")
         config.update(specified_config)
 
diff --git a/synapse/config/database.py b/synapse/config/database.py
index e915d9d09b..c8890147a6 100644
--- a/synapse/config/database.py
+++ b/synapse/config/database.py
@@ -12,6 +12,7 @@
 # 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 os
 
 from ._base import Config
 
@@ -45,8 +46,8 @@ class DatabaseConfig(Config):
 
         self.set_databasepath(config.get("database_path"))
 
-    def default_config(self, **kwargs):
-        database_path = self.abspath("homeserver.db")
+    def default_config(self, data_dir_path, **kwargs):
+        database_path = os.path.join(data_dir_path, "homeserver.db")
         return """\
         # Database configuration
         database:
diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index 9d740c7a71..5aad062c36 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -53,10 +53,3 @@ class HomeServerConfig(TlsConfig, ServerConfig, DatabaseConfig, LoggingConfig,
                        ServerNoticesConfig, RoomDirectoryConfig,
                        ):
     pass
-
-
-if __name__ == '__main__':
-    import sys
-    sys.stdout.write(
-        HomeServerConfig().generate_config(sys.argv[1], sys.argv[2], True)[0]
-    )
diff --git a/synapse/config/key.py b/synapse/config/key.py
index 279c47bb48..53f48fe2dd 100644
--- a/synapse/config/key.py
+++ b/synapse/config/key.py
@@ -66,26 +66,35 @@ class KeyConfig(Config):
         # falsification of values
         self.form_secret = config.get("form_secret", None)
 
-    def default_config(self, config_dir_path, server_name, is_generating_file=False,
+    def default_config(self, config_dir_path, server_name, generate_secrets=False,
                        **kwargs):
         base_key_name = os.path.join(config_dir_path, server_name)
 
-        if is_generating_file:
-            macaroon_secret_key = random_string_with_symbols(50)
-            form_secret = '"%s"' % random_string_with_symbols(50)
+        if generate_secrets:
+            macaroon_secret_key = 'macaroon_secret_key: "%s"' % (
+                random_string_with_symbols(50),
+            )
+            form_secret = 'form_secret: "%s"' % random_string_with_symbols(50)
         else:
-            macaroon_secret_key = None
-            form_secret = 'null'
+            macaroon_secret_key = "# macaroon_secret_key: <PRIVATE STRING>"
+            form_secret = "# form_secret: <PRIVATE STRING>"
 
         return """\
-        macaroon_secret_key: "%(macaroon_secret_key)s"
+        # a secret which is used to sign access tokens. If none is specified,
+        # the registration_shared_secret is used, if one is given; otherwise,
+        # a secret key is derived from the signing key.
+        #
+        # Note that changing this will invalidate any active access tokens, so
+        # all clients will have to log back in.
+        %(macaroon_secret_key)s
 
         # Used to enable access token expiration.
         expire_access_token: False
 
         # a secret which is used to calculate HMACs for form values, to stop
-        # falsification of values
-        form_secret: %(form_secret)s
+        # falsification of values. Must be specified for the User Consent
+        # forms to work.
+        %(form_secret)s
 
         ## Signing Keys ##
 
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index 7081868963..f87efecbf8 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -80,9 +80,7 @@ class LoggingConfig(Config):
         self.log_file = self.abspath(config.get("log_file"))
 
     def default_config(self, config_dir_path, server_name, **kwargs):
-        log_config = self.abspath(
-            os.path.join(config_dir_path, server_name + ".log.config")
-        )
+        log_config = os.path.join(config_dir_path, server_name + ".log.config")
         return """
         # A yaml python logging config file
         log_config: "%(log_config)s"
diff --git a/synapse/config/metrics.py b/synapse/config/metrics.py
index 61155c99d0..718c43ae03 100644
--- a/synapse/config/metrics.py
+++ b/synapse/config/metrics.py
@@ -24,10 +24,16 @@ class MetricsConfig(Config):
         self.metrics_bind_host = config.get("metrics_bind_host", "127.0.0.1")
 
     def default_config(self, report_stats=None, **kwargs):
-        suffix = "" if report_stats is None else "report_stats: %(report_stats)s\n"
-        return ("""\
+        res = """\
         ## Metrics ###
 
         # Enable collection and rendering of performance metrics
         enable_metrics: False
-        """ + suffix) % locals()
+        """
+
+        if report_stats is None:
+            res += "# report_stats: true|false\n"
+        else:
+            res += "report_stats: %s\n" % ('true' if report_stats else 'false')
+
+        return res
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index e365f0c30b..6c2b543b8c 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -50,8 +50,13 @@ class RegistrationConfig(Config):
                 raise ConfigError('Invalid auto_join_rooms entry %s' % (room_alias,))
         self.autocreate_auto_join_rooms = config.get("autocreate_auto_join_rooms", True)
 
-    def default_config(self, **kwargs):
-        registration_shared_secret = random_string_with_symbols(50)
+    def default_config(self, generate_secrets=False, **kwargs):
+        if generate_secrets:
+            registration_shared_secret = 'registration_shared_secret: "%s"' % (
+                random_string_with_symbols(50),
+            )
+        else:
+            registration_shared_secret = '# registration_shared_secret: <PRIVATE STRING>'
 
         return """\
         ## Registration ##
@@ -78,7 +83,7 @@ class RegistrationConfig(Config):
 
         # If set, allows registration by anyone who also has the shared
         # secret, even if registration is otherwise disabled.
-        registration_shared_secret: "%(registration_shared_secret)s"
+        %(registration_shared_secret)s
 
         # Set the number of bcrypt rounds used to generate password hash.
         # Larger numbers increase the work factor needed to generate the hash.
diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 06c62ab62c..76e3340a91 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -12,7 +12,7 @@
 # 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 os
 from collections import namedtuple
 
 from synapse.util.module_loader import load_module
@@ -175,9 +175,9 @@ class ContentRepositoryConfig(Config):
                 "url_preview_url_blacklist", ()
             )
 
-    def default_config(self, **kwargs):
-        media_store = self.default_path("media_store")
-        uploads_path = self.default_path("uploads")
+    def default_config(self, data_dir_path, **kwargs):
+        media_store = os.path.join(data_dir_path, "media_store")
+        uploads_path = os.path.join(data_dir_path, "uploads")
         return r"""
         # Directory where uploaded images and attachments are stored.
         media_store_path: "%(media_store)s"
diff --git a/synapse/config/server.py b/synapse/config/server.py
index a9154ad462..120c2b81fc 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import logging
+import os.path
 
 from synapse.http.endpoint import parse_and_validate_server_name
 
@@ -203,7 +204,7 @@ class ServerConfig(Config):
                 ]
             })
 
-    def default_config(self, server_name, **kwargs):
+    def default_config(self, server_name, data_dir_path, **kwargs):
         _, bind_port = parse_and_validate_server_name(server_name)
         if bind_port is not None:
             unsecure_port = bind_port - 400
@@ -211,7 +212,7 @@ class ServerConfig(Config):
             bind_port = 8448
             unsecure_port = 8008
 
-        pid_file = self.abspath("homeserver.pid")
+        pid_file = os.path.join(data_dir_path, "homeserver.pid")
         return """\
         ## Server ##
 
@@ -356,41 +357,41 @@ class ServerConfig(Config):
           #   type: manhole
 
 
-          # Homeserver blocking
-          #
-          # How to reach the server admin, used in ResourceLimitError
-          # admin_contact: 'mailto:admin@server.com'
-          #
-          # Global block config
-          #
-          # hs_disabled: False
-          # hs_disabled_message: 'Human readable reason for why the HS is blocked'
-          # hs_disabled_limit_type: 'error code(str), to help clients decode reason'
-          #
-          # Monthly Active User Blocking
-          #
-          # Enables monthly active user checking
-          # limit_usage_by_mau: False
-          # max_mau_value: 50
-          # mau_trial_days: 2
-          #
-          # If enabled, the metrics for the number of monthly active users will
-          # be populated, however no one will be limited. If limit_usage_by_mau
-          # is true, this is implied to be true.
-          # mau_stats_only: False
-          #
-          # Sometimes the server admin will want to ensure certain accounts are
-          # never blocked by mau checking. These accounts are specified here.
-          #
-          # mau_limit_reserved_threepids:
-          # - medium: 'email'
-          #   address: 'reserved_user@example.com'
-          #
-          # Room searching
-          #
-          # If disabled, new messages will not be indexed for searching and users
-          # will receive errors when searching for messages. Defaults to enabled.
-          # enable_search: true
+        # Homeserver blocking
+        #
+        # How to reach the server admin, used in ResourceLimitError
+        # admin_contact: 'mailto:admin@server.com'
+        #
+        # Global block config
+        #
+        # hs_disabled: False
+        # hs_disabled_message: 'Human readable reason for why the HS is blocked'
+        # hs_disabled_limit_type: 'error code(str), to help clients decode reason'
+        #
+        # Monthly Active User Blocking
+        #
+        # Enables monthly active user checking
+        # limit_usage_by_mau: False
+        # max_mau_value: 50
+        # mau_trial_days: 2
+        #
+        # If enabled, the metrics for the number of monthly active users will
+        # be populated, however no one will be limited. If limit_usage_by_mau
+        # is true, this is implied to be true.
+        # mau_stats_only: False
+        #
+        # Sometimes the server admin will want to ensure certain accounts are
+        # never blocked by mau checking. These accounts are specified here.
+        #
+        # mau_limit_reserved_threepids:
+        # - medium: 'email'
+        #   address: 'reserved_user@example.com'
+        #
+        # Room searching
+        #
+        # If disabled, new messages will not be indexed for searching and users
+        # will receive errors when searching for messages. Defaults to enabled.
+        # enable_search: true
         """ % locals()
 
     def read_arguments(self, args):
diff --git a/synapse/http/client.py b/synapse/http/client.py
index 3d05f83b8c..afcf698b29 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -21,28 +21,25 @@ from six.moves import urllib
 
 import treq
 from canonicaljson import encode_canonical_json, json
+from netaddr import IPAddress
 from prometheus_client import Counter
+from zope.interface import implementer, provider
 
 from OpenSSL import SSL
 from OpenSSL.SSL import VERIFY_NONE
-from twisted.internet import defer, protocol, reactor, ssl
-from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
-from twisted.web._newclient import ResponseDone
-from twisted.web.client import (
-    Agent,
-    BrowserLikeRedirectAgent,
-    ContentDecoderAgent,
-    GzipDecoder,
-    HTTPConnectionPool,
-    PartialDownloadError,
-    readBody,
+from twisted.internet import defer, protocol, ssl
+from twisted.internet.interfaces import (
+    IReactorPluggableNameResolver,
+    IResolutionReceiver,
 )
+from twisted.python.failure import Failure
+from twisted.web._newclient import ResponseDone
+from twisted.web.client import Agent, HTTPConnectionPool, PartialDownloadError, readBody
 from twisted.web.http import PotentialDataLoss
 from twisted.web.http_headers import Headers
 
 from synapse.api.errors import Codes, HttpResponseException, SynapseError
 from synapse.http import cancelled_to_request_timed_out_error, redact_uri
-from synapse.http.endpoint import SpiderEndpoint
 from synapse.util.async_helpers import timeout_deferred
 from synapse.util.caches import CACHE_SIZE_FACTOR
 from synapse.util.logcontext import make_deferred_yieldable
@@ -50,8 +47,125 @@ from synapse.util.logcontext import make_deferred_yieldable
 logger = logging.getLogger(__name__)
 
 outgoing_requests_counter = Counter("synapse_http_client_requests", "", ["method"])
-incoming_responses_counter = Counter("synapse_http_client_responses", "",
-                                     ["method", "code"])
+incoming_responses_counter = Counter(
+    "synapse_http_client_responses", "", ["method", "code"]
+)
+
+
+def check_against_blacklist(ip_address, ip_whitelist, ip_blacklist):
+    """
+    Args:
+        ip_address (netaddr.IPAddress)
+        ip_whitelist (netaddr.IPSet)
+        ip_blacklist (netaddr.IPSet)
+    """
+    if ip_address in ip_blacklist:
+        if ip_whitelist is None or ip_address not in ip_whitelist:
+            return True
+    return False
+
+
+class IPBlacklistingResolver(object):
+    """
+    A proxy for reactor.nameResolver which only produces non-blacklisted IP
+    addresses, preventing DNS rebinding attacks on URL preview.
+    """
+
+    def __init__(self, reactor, ip_whitelist, ip_blacklist):
+        """
+        Args:
+            reactor (twisted.internet.reactor)
+            ip_whitelist (netaddr.IPSet)
+            ip_blacklist (netaddr.IPSet)
+        """
+        self._reactor = reactor
+        self._ip_whitelist = ip_whitelist
+        self._ip_blacklist = ip_blacklist
+
+    def resolveHostName(self, recv, hostname, portNumber=0):
+
+        r = recv()
+        d = defer.Deferred()
+        addresses = []
+
+        @provider(IResolutionReceiver)
+        class EndpointReceiver(object):
+            @staticmethod
+            def resolutionBegan(resolutionInProgress):
+                pass
+
+            @staticmethod
+            def addressResolved(address):
+                ip_address = IPAddress(address.host)
+
+                if check_against_blacklist(
+                    ip_address, self._ip_whitelist, self._ip_blacklist
+                ):
+                    logger.info(
+                        "Dropped %s from DNS resolution to %s" % (ip_address, hostname)
+                    )
+                    raise SynapseError(403, "IP address blocked by IP blacklist entry")
+
+                addresses.append(address)
+
+            @staticmethod
+            def resolutionComplete():
+                d.callback(addresses)
+
+        self._reactor.nameResolver.resolveHostName(
+            EndpointReceiver, hostname, portNumber=portNumber
+        )
+
+        def _callback(addrs):
+            r.resolutionBegan(None)
+            for i in addrs:
+                r.addressResolved(i)
+            r.resolutionComplete()
+
+        d.addCallback(_callback)
+
+        return r
+
+
+class BlacklistingAgentWrapper(Agent):
+    """
+    An Agent wrapper which will prevent access to IP addresses being accessed
+    directly (without an IP address lookup).
+    """
+
+    def __init__(self, agent, reactor, ip_whitelist=None, ip_blacklist=None):
+        """
+        Args:
+            agent (twisted.web.client.Agent): The Agent to wrap.
+            reactor (twisted.internet.reactor)
+            ip_whitelist (netaddr.IPSet)
+            ip_blacklist (netaddr.IPSet)
+        """
+        self._agent = agent
+        self._ip_whitelist = ip_whitelist
+        self._ip_blacklist = ip_blacklist
+
+    def request(self, method, uri, headers=None, bodyProducer=None):
+        h = urllib.parse.urlparse(uri.decode('ascii'))
+
+        try:
+            ip_address = IPAddress(h.hostname)
+
+            if check_against_blacklist(
+                ip_address, self._ip_whitelist, self._ip_blacklist
+            ):
+                logger.info(
+                    "Blocking access to %s because of blacklist" % (ip_address,)
+                )
+                e = SynapseError(403, "IP address blocked by IP blacklist entry")
+                return defer.fail(Failure(e))
+        except Exception:
+            # Not an IP
+            pass
+
+        return self._agent.request(
+            method, uri, headers=headers, bodyProducer=bodyProducer
+        )
 
 
 class SimpleHttpClient(object):
@@ -59,14 +173,54 @@ class SimpleHttpClient(object):
     A simple, no-frills HTTP client with methods that wrap up common ways of
     using HTTP in Matrix
     """
-    def __init__(self, hs):
+
+    def __init__(self, hs, treq_args={}, ip_whitelist=None, ip_blacklist=None):
+        """
+        Args:
+            hs (synapse.server.HomeServer)
+            treq_args (dict): Extra keyword arguments to be given to treq.request.
+            ip_blacklist (netaddr.IPSet): The IP addresses that are blacklisted that
+                we may not request.
+            ip_whitelist (netaddr.IPSet): The whitelisted IP addresses, that we can
+               request if it were otherwise caught in a blacklist.
+        """
         self.hs = hs
 
-        pool = HTTPConnectionPool(reactor)
+        self._ip_whitelist = ip_whitelist
+        self._ip_blacklist = ip_blacklist
+        self._extra_treq_args = treq_args
+
+        self.user_agent = hs.version_string
+        self.clock = hs.get_clock()
+        if hs.config.user_agent_suffix:
+            self.user_agent = "%s %s" % (self.user_agent, hs.config.user_agent_suffix)
+
+        self.user_agent = self.user_agent.encode('ascii')
+
+        if self._ip_blacklist:
+            real_reactor = hs.get_reactor()
+            # If we have an IP blacklist, we need to use a DNS resolver which
+            # filters out blacklisted IP addresses, to prevent DNS rebinding.
+            nameResolver = IPBlacklistingResolver(
+                real_reactor, self._ip_whitelist, self._ip_blacklist
+            )
+
+            @implementer(IReactorPluggableNameResolver)
+            class Reactor(object):
+                def __getattr__(_self, attr):
+                    if attr == "nameResolver":
+                        return nameResolver
+                    else:
+                        return getattr(real_reactor, attr)
+
+            self.reactor = Reactor()
+        else:
+            self.reactor = hs.get_reactor()
 
         # the pusher makes lots of concurrent SSL connections to sygnal, and
-        # tends to do so in batches, so we need to allow the pool to keep lots
-        # of idle connections around.
+        # tends to do so in batches, so we need to allow the pool to keep
+        # lots of idle connections around.
+        pool = HTTPConnectionPool(self.reactor)
         pool.maxPersistentPerHost = max((100 * CACHE_SIZE_FACTOR, 5))
         pool.cachedConnectionTimeout = 2 * 60
 
@@ -74,20 +228,35 @@ class SimpleHttpClient(object):
         # BrowserLikePolicyForHTTPS which will do regular cert validation
         # 'like a browser'
         self.agent = Agent(
-            reactor,
+            self.reactor,
             connectTimeout=15,
-            contextFactory=hs.get_http_client_context_factory(),
+            contextFactory=self.hs.get_http_client_context_factory(),
             pool=pool,
         )
-        self.user_agent = hs.version_string
-        self.clock = hs.get_clock()
-        if hs.config.user_agent_suffix:
-            self.user_agent = "%s %s" % (self.user_agent, hs.config.user_agent_suffix,)
 
-        self.user_agent = self.user_agent.encode('ascii')
+        if self._ip_blacklist:
+            # If we have an IP blacklist, we then install the blacklisting Agent
+            # which prevents direct access to IP addresses, that are not caught
+            # by the DNS resolution.
+            self.agent = BlacklistingAgentWrapper(
+                self.agent,
+                self.reactor,
+                ip_whitelist=self._ip_whitelist,
+                ip_blacklist=self._ip_blacklist,
+            )
 
     @defer.inlineCallbacks
     def request(self, method, uri, data=b'', headers=None):
+        """
+        Args:
+            method (str): HTTP method to use.
+            uri (str): URI to query.
+            data (bytes): Data to send in the request body, if applicable.
+            headers (t.w.http_headers.Headers): Request headers.
+
+        Raises:
+            SynapseError: If the IP is blacklisted.
+        """
         # A small wrapper around self.agent.request() so we can easily attach
         # counters to it
         outgoing_requests_counter.labels(method).inc()
@@ -97,25 +266,34 @@ class SimpleHttpClient(object):
 
         try:
             request_deferred = treq.request(
-                method, uri, agent=self.agent, data=data, headers=headers
+                method,
+                uri,
+                agent=self.agent,
+                data=data,
+                headers=headers,
+                **self._extra_treq_args
             )
             request_deferred = timeout_deferred(
-                request_deferred, 60, self.hs.get_reactor(),
+                request_deferred,
+                60,
+                self.hs.get_reactor(),
                 cancelled_to_request_timed_out_error,
             )
             response = yield make_deferred_yieldable(request_deferred)
 
             incoming_responses_counter.labels(method, response.code).inc()
             logger.info(
-                "Received response to  %s %s: %s",
-                method, redact_uri(uri), response.code
+                "Received response to %s %s: %s", method, redact_uri(uri), response.code
             )
             defer.returnValue(response)
         except Exception as e:
             incoming_responses_counter.labels(method, "ERR").inc()
             logger.info(
                 "Error sending request to  %s %s: %s %s",
-                method, redact_uri(uri), type(e).__name__, e.args[0]
+                method,
+                redact_uri(uri),
+                type(e).__name__,
+                e.args[0],
             )
             raise
 
@@ -140,8 +318,9 @@ class SimpleHttpClient(object):
         # TODO: Do we ever want to log message contents?
         logger.debug("post_urlencoded_get_json args: %s", args)
 
-        query_bytes = urllib.parse.urlencode(
-            encode_urlencode_args(args), True).encode("utf8")
+        query_bytes = urllib.parse.urlencode(encode_urlencode_args(args), True).encode(
+            "utf8"
+        )
 
         actual_headers = {
             b"Content-Type": [b"application/x-www-form-urlencoded"],
@@ -151,10 +330,7 @@ class SimpleHttpClient(object):
             actual_headers.update(headers)
 
         response = yield self.request(
-            "POST",
-            uri,
-            headers=Headers(actual_headers),
-            data=query_bytes
+            "POST", uri, headers=Headers(actual_headers), data=query_bytes
         )
 
         if 200 <= response.code < 300:
@@ -193,10 +369,7 @@ class SimpleHttpClient(object):
             actual_headers.update(headers)
 
         response = yield self.request(
-            "POST",
-            uri,
-            headers=Headers(actual_headers),
-            data=json_str
+            "POST", uri, headers=Headers(actual_headers), data=json_str
         )
 
         body = yield make_deferred_yieldable(readBody(response))
@@ -264,10 +437,7 @@ class SimpleHttpClient(object):
             actual_headers.update(headers)
 
         response = yield self.request(
-            "PUT",
-            uri,
-            headers=Headers(actual_headers),
-            data=json_str
+            "PUT", uri, headers=Headers(actual_headers), data=json_str
         )
 
         body = yield make_deferred_yieldable(readBody(response))
@@ -299,17 +469,11 @@ class SimpleHttpClient(object):
             query_bytes = urllib.parse.urlencode(args, True)
             uri = "%s?%s" % (uri, query_bytes)
 
-        actual_headers = {
-            b"User-Agent": [self.user_agent],
-        }
+        actual_headers = {b"User-Agent": [self.user_agent]}
         if headers:
             actual_headers.update(headers)
 
-        response = yield self.request(
-            "GET",
-            uri,
-            headers=Headers(actual_headers),
-        )
+        response = yield self.request("GET", uri, headers=Headers(actual_headers))
 
         body = yield make_deferred_yieldable(readBody(response))
 
@@ -334,22 +498,18 @@ class SimpleHttpClient(object):
             headers, absolute URI of the response and HTTP response code.
         """
 
-        actual_headers = {
-            b"User-Agent": [self.user_agent],
-        }
+        actual_headers = {b"User-Agent": [self.user_agent]}
         if headers:
             actual_headers.update(headers)
 
-        response = yield self.request(
-            "GET",
-            url,
-            headers=Headers(actual_headers),
-        )
+        response = yield self.request("GET", url, headers=Headers(actual_headers))
 
         resp_headers = dict(response.headers.getAllRawHeaders())
 
-        if (b'Content-Length' in resp_headers and
-                int(resp_headers[b'Content-Length']) > max_size):
+        if (
+            b'Content-Length' in resp_headers
+            and int(resp_headers[b'Content-Length'][0]) > max_size
+        ):
             logger.warn("Requested URL is too large > %r bytes" % (self.max_size,))
             raise SynapseError(
                 502,
@@ -359,26 +519,20 @@ class SimpleHttpClient(object):
 
         if response.code > 299:
             logger.warn("Got %d when downloading %s" % (response.code, url))
-            raise SynapseError(
-                502,
-                "Got error %d" % (response.code,),
-                Codes.UNKNOWN,
-            )
+            raise SynapseError(502, "Got error %d" % (response.code,), Codes.UNKNOWN)
 
         # TODO: if our Content-Type is HTML or something, just read the first
         # N bytes into RAM rather than saving it all to disk only to read it
         # straight back in again
 
         try:
-            length = yield make_deferred_yieldable(_readBodyToFile(
-                response, output_stream, max_size,
-            ))
+            length = yield make_deferred_yieldable(
+                _readBodyToFile(response, output_stream, max_size)
+            )
         except Exception as e:
             logger.exception("Failed to download body")
             raise SynapseError(
-                502,
-                ("Failed to download remote body: %s" % e),
-                Codes.UNKNOWN,
+                502, ("Failed to download remote body: %s" % e), Codes.UNKNOWN
             )
 
         defer.returnValue(
@@ -387,13 +541,14 @@ class SimpleHttpClient(object):
                 resp_headers,
                 response.request.absoluteURI.decode('ascii'),
                 response.code,
-            ),
+            )
         )
 
 
 # XXX: FIXME: This is horribly copy-pasted from matrixfederationclient.
 # The two should be factored out.
 
+
 class _ReadBodyToFileProtocol(protocol.Protocol):
     def __init__(self, stream, deferred, max_size):
         self.stream = stream
@@ -405,11 +560,13 @@ class _ReadBodyToFileProtocol(protocol.Protocol):
         self.stream.write(data)
         self.length += len(data)
         if self.max_size is not None and self.length >= self.max_size:
-            self.deferred.errback(SynapseError(
-                502,
-                "Requested file is too large > %r bytes" % (self.max_size,),
-                Codes.TOO_LARGE,
-            ))
+            self.deferred.errback(
+                SynapseError(
+                    502,
+                    "Requested file is too large > %r bytes" % (self.max_size,),
+                    Codes.TOO_LARGE,
+                )
+            )
             self.deferred = defer.Deferred()
             self.transport.loseConnection()
 
@@ -427,6 +584,7 @@ class _ReadBodyToFileProtocol(protocol.Protocol):
 # XXX: FIXME: This is horribly copy-pasted from matrixfederationclient.
 # The two should be factored out.
 
+
 def _readBodyToFile(response, stream, max_size):
     d = defer.Deferred()
     response.deliverBody(_ReadBodyToFileProtocol(stream, d, max_size))
@@ -449,10 +607,12 @@ class CaptchaServerHttpClient(SimpleHttpClient):
             "POST",
             url,
             data=query_bytes,
-            headers=Headers({
-                b"Content-Type": [b"application/x-www-form-urlencoded"],
-                b"User-Agent": [self.user_agent],
-            })
+            headers=Headers(
+                {
+                    b"Content-Type": [b"application/x-www-form-urlencoded"],
+                    b"User-Agent": [self.user_agent],
+                }
+            ),
         )
 
         try:
@@ -463,57 +623,6 @@ class CaptchaServerHttpClient(SimpleHttpClient):
             defer.returnValue(e.response)
 
 
-class SpiderEndpointFactory(object):
-    def __init__(self, hs):
-        self.blacklist = hs.config.url_preview_ip_range_blacklist
-        self.whitelist = hs.config.url_preview_ip_range_whitelist
-        self.policyForHTTPS = hs.get_http_client_context_factory()
-
-    def endpointForURI(self, uri):
-        logger.info("Getting endpoint for %s", uri.toBytes())
-
-        if uri.scheme == b"http":
-            endpoint_factory = HostnameEndpoint
-        elif uri.scheme == b"https":
-            tlsCreator = self.policyForHTTPS.creatorForNetloc(uri.host, uri.port)
-
-            def endpoint_factory(reactor, host, port, **kw):
-                return wrapClientTLS(
-                    tlsCreator,
-                    HostnameEndpoint(reactor, host, port, **kw))
-        else:
-            logger.warn("Can't get endpoint for unrecognised scheme %s", uri.scheme)
-            return None
-        return SpiderEndpoint(
-            reactor, uri.host, uri.port, self.blacklist, self.whitelist,
-            endpoint=endpoint_factory, endpoint_kw_args=dict(timeout=15),
-        )
-
-
-class SpiderHttpClient(SimpleHttpClient):
-    """
-    Separate HTTP client for spidering arbitrary URLs.
-    Special in that it follows retries and has a UA that looks
-    like a browser.
-
-    used by the preview_url endpoint in the content repo.
-    """
-    def __init__(self, hs):
-        SimpleHttpClient.__init__(self, hs)
-        # clobber the base class's agent and UA:
-        self.agent = ContentDecoderAgent(
-            BrowserLikeRedirectAgent(
-                Agent.usingEndpointFactory(
-                    reactor,
-                    SpiderEndpointFactory(hs)
-                )
-            ), [(b'gzip', GzipDecoder)]
-        )
-        # We could look like Chrome:
-        # self.user_agent = ("Mozilla/5.0 (%s) (KHTML, like Gecko)
-        #                   Chrome Safari" % hs.version_string)
-
-
 def encode_urlencode_args(args):
     return {k: encode_urlencode_arg(v) for k, v in args.items()}
 
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index 91025037a3..f86a0b624e 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -218,41 +218,6 @@ class _WrappedConnection(object):
         return d
 
 
-class SpiderEndpoint(object):
-    """An endpoint which refuses to connect to blacklisted IP addresses
-    Implements twisted.internet.interfaces.IStreamClientEndpoint.
-    """
-    def __init__(self, reactor, host, port, blacklist, whitelist,
-                 endpoint=HostnameEndpoint, endpoint_kw_args={}):
-        self.reactor = reactor
-        self.host = host
-        self.port = port
-        self.blacklist = blacklist
-        self.whitelist = whitelist
-        self.endpoint = endpoint
-        self.endpoint_kw_args = endpoint_kw_args
-
-    @defer.inlineCallbacks
-    def connect(self, protocolFactory):
-        address = yield self.reactor.resolve(self.host)
-
-        from netaddr import IPAddress
-        ip_address = IPAddress(address)
-
-        if ip_address in self.blacklist:
-            if self.whitelist is None or ip_address not in self.whitelist:
-                raise ConnectError(
-                    "Refusing to spider blacklisted IP address %s" % address
-                )
-
-        logger.info("Connecting to %s:%s", address, self.port)
-        endpoint = self.endpoint(
-            self.reactor, address, self.port, **self.endpoint_kw_args
-        )
-        connection = yield endpoint.connect(protocolFactory)
-        defer.returnValue(connection)
-
-
 class SRVClientEndpoint(object):
     """An endpoint which looks up SRV records for a service.
     Cycles through the list of servers starting with each call to connect
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 72a92cc462..2c65ef5856 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -15,175 +15,121 @@
 # limitations under the License.
 
 import logging
-from distutils.version import LooseVersion
+
+from pkg_resources import DistributionNotFound, VersionConflict, get_distribution
 
 logger = logging.getLogger(__name__)
 
-# this dict maps from python package name to a list of modules we expect it to
-# provide.
-#
-# the key is a "requirement specifier", as used as a parameter to `pip
-# install`[1], or an `install_requires` argument to `setuptools.setup` [2].
+
+# REQUIREMENTS is a simple list of requirement specifiers[1], and must be
+# installed. It is passed to setup() as install_requires in setup.py.
 #
-# the value is a sequence of strings; each entry should be the name of the
-# python module, optionally followed by a version assertion which can be either
-# ">=<ver>" or "==<ver>".
+# CONDITIONAL_REQUIREMENTS is the optional dependencies, represented as a dict
+# of lists. The dict key is the optional dependency name and can be passed to
+# pip when installing. The list is a series of requirement specifiers[1] to be
+# installed when that optional dependency requirement is specified. It is passed
+# to setup() as extras_require in setup.py
 #
 # [1] https://pip.pypa.io/en/stable/reference/pip_install/#requirement-specifiers.
-# [2] https://setuptools.readthedocs.io/en/latest/setuptools.html#declaring-dependencies
-REQUIREMENTS = {
-    "jsonschema>=2.5.1": ["jsonschema>=2.5.1"],
-    "frozendict>=1": ["frozendict"],
-    "unpaddedbase64>=1.1.0": ["unpaddedbase64>=1.1.0"],
-    "canonicaljson>=1.1.3": ["canonicaljson>=1.1.3"],
-    "signedjson>=1.0.0": ["signedjson>=1.0.0"],
-    "pynacl>=1.2.1": ["nacl>=1.2.1", "nacl.bindings"],
-    "service_identity>=16.0.0": ["service_identity>=16.0.0"],
-    "Twisted>=17.1.0": ["twisted>=17.1.0"],
-    "treq>=15.1": ["treq>=15.1"],
 
+REQUIREMENTS = [
+    "jsonschema>=2.5.1",
+    "frozendict>=1",
+    "unpaddedbase64>=1.1.0",
+    "canonicaljson>=1.1.3",
+    "signedjson>=1.0.0",
+    "pynacl>=1.2.1",
+    "service_identity>=16.0.0",
+    "Twisted>=17.1.0",
+    "treq>=15.1",
     # Twisted has required pyopenssl 16.0 since about Twisted 16.6.
-    "pyopenssl>=16.0.0": ["OpenSSL>=16.0.0"],
-
-    "pyyaml>=3.11": ["yaml"],
-    "pyasn1>=0.1.9": ["pyasn1"],
-    "pyasn1-modules>=0.0.7": ["pyasn1_modules"],
-    "daemonize>=2.3.1": ["daemonize"],
-    "bcrypt>=3.1.0": ["bcrypt>=3.1.0"],
-    "pillow>=3.1.2": ["PIL"],
-    "sortedcontainers>=1.4.4": ["sortedcontainers"],
-    "psutil>=2.0.0": ["psutil>=2.0.0"],
-    "pymacaroons-pynacl>=0.9.3": ["pymacaroons"],
-    "msgpack-python>=0.4.2": ["msgpack"],
-    "phonenumbers>=8.2.0": ["phonenumbers"],
-    "six>=1.10": ["six"],
-
+    "pyopenssl>=16.0.0",
+    "pyyaml>=3.11",
+    "pyasn1>=0.1.9",
+    "pyasn1-modules>=0.0.7",
+    "daemonize>=2.3.1",
+    "bcrypt>=3.1.0",
+    "pillow>=3.1.2",
+    "sortedcontainers>=1.4.4",
+    "psutil>=2.0.0",
+    "pymacaroons-pynacl>=0.9.3",
+    "msgpack-python>=0.4.2",
+    "phonenumbers>=8.2.0",
+    "six>=1.10",
     # prometheus_client 0.4.0 changed the format of counter metrics
     # (cf https://github.com/matrix-org/synapse/issues/4001)
-    "prometheus_client>=0.0.18,<0.4.0": ["prometheus_client"],
-
+    "prometheus_client>=0.0.18,<0.4.0",
     # we use attr.s(slots), which arrived in 16.0.0
-    "attrs>=16.0.0": ["attr>=16.0.0"],
-    "netaddr>=0.7.18": ["netaddr"],
-}
+    "attrs>=16.0.0",
+    "netaddr>=0.7.18",
+]
 
 CONDITIONAL_REQUIREMENTS = {
-    "email.enable_notifs": {
-        "Jinja2>=2.8": ["Jinja2>=2.8"],
-        "bleach>=1.4.2": ["bleach>=1.4.2"],
-    },
-    "matrix-synapse-ldap3": {
-        "matrix-synapse-ldap3>=0.1": ["ldap_auth_provider"],
-    },
-    "postgres": {
-        "psycopg2>=2.6": ["psycopg2"]
-    },
-    "saml2": {
-        "pysaml2>=4.5.0": ["saml2"],
-    },
+    "email.enable_notifs": ["Jinja2>=2.8", "bleach>=1.4.2"],
+    "matrix-synapse-ldap3": ["matrix-synapse-ldap3>=0.1"],
+    "postgres": ["psycopg2>=2.6"],
+    "saml2": ["pysaml2>=4.5.0"],
+    "url_preview": ["lxml>=3.5.0"],
+    "test": ["mock>=2.0"],
 }
 
 
-def requirements(config=None, include_conditional=False):
-    reqs = REQUIREMENTS.copy()
-    if include_conditional:
-        for _, req in CONDITIONAL_REQUIREMENTS.items():
-            reqs.update(req)
-    return reqs
+def list_requirements():
+    deps = set(REQUIREMENTS)
+    for opt in CONDITIONAL_REQUIREMENTS.values():
+        deps = set(opt) | deps
 
+    return list(deps)
 
-def github_link(project, version, egg):
-    return "https://github.com/%s/tarball/%s/#egg=%s" % (project, version, egg)
 
+class DependencyException(Exception):
+    @property
+    def dependencies(self):
+        for i in self.args[0]:
+            yield '"' + i + '"'
 
-DEPENDENCY_LINKS = {
-}
 
+def check_requirements(_get_distribution=get_distribution):
+
+    deps_needed = []
+    errors = []
 
-class MissingRequirementError(Exception):
-    def __init__(self, message, module_name, dependency):
-        super(MissingRequirementError, self).__init__(message)
-        self.module_name = module_name
-        self.dependency = dependency
-
-
-def check_requirements(config=None):
-    """Checks that all the modules needed by synapse have been correctly
-    installed and are at the correct version"""
-    for dependency, module_requirements in (
-            requirements(config, include_conditional=False).items()):
-        for module_requirement in module_requirements:
-            if ">=" in module_requirement:
-                module_name, required_version = module_requirement.split(">=")
-                version_test = ">="
-            elif "==" in module_requirement:
-                module_name, required_version = module_requirement.split("==")
-                version_test = "=="
-            else:
-                module_name = module_requirement
-                version_test = None
-
-            try:
-                module = __import__(module_name)
-            except ImportError:
-                logging.exception(
-                    "Can't import %r which is part of %r",
-                    module_name, dependency
-                )
-                raise MissingRequirementError(
-                    "Can't import %r which is part of %r"
-                    % (module_name, dependency), module_name, dependency
-                )
-            version = getattr(module, "__version__", None)
-            file_path = getattr(module, "__file__", None)
-            logger.info(
-                "Using %r version %r from %r to satisfy %r",
-                module_name, version, file_path, dependency
+    # Check the base dependencies exist -- they all must be installed.
+    for dependency in REQUIREMENTS:
+        try:
+            _get_distribution(dependency)
+        except VersionConflict as e:
+            deps_needed.append(dependency)
+            errors.append(
+                "Needed %s, got %s==%s"
+                % (dependency, e.dist.project_name, e.dist.version)
             )
+        except DistributionNotFound:
+            deps_needed.append(dependency)
+            errors.append("Needed %s but it was not installed" % (dependency,))
 
-            if version_test == ">=":
-                if version is None:
-                    raise MissingRequirementError(
-                        "Version of %r isn't set as __version__ of module %r"
-                        % (dependency, module_name), module_name, dependency
-                    )
-                if LooseVersion(version) < LooseVersion(required_version):
-                    raise MissingRequirementError(
-                        "Version of %r in %r is too old. %r < %r"
-                        % (dependency, file_path, version, required_version),
-                        module_name, dependency
-                    )
-            elif version_test == "==":
-                if version is None:
-                    raise MissingRequirementError(
-                        "Version of %r isn't set as __version__ of module %r"
-                        % (dependency, module_name), module_name, dependency
-                    )
-                if LooseVersion(version) != LooseVersion(required_version):
-                    raise MissingRequirementError(
-                        "Unexpected version of %r in %r. %r != %r"
-                        % (dependency, file_path, version, required_version),
-                        module_name, dependency
-                    )
+    # Check the optional dependencies are up to date. We allow them to not be
+    # installed.
+    OPTS = sum(CONDITIONAL_REQUIREMENTS.values(), [])
 
+    for dependency in OPTS:
+        try:
+            _get_distribution(dependency)
+        except VersionConflict:
+            deps_needed.append(dependency)
+            errors.append("Needed %s but it was not installed" % (dependency,))
+        except DistributionNotFound:
+            # If it's not found, we don't care
+            pass
 
-def list_requirements():
-    result = []
-    linked = []
-    for link in DEPENDENCY_LINKS.values():
-        egg = link.split("#egg=")[1]
-        linked.append(egg.split('-')[0])
-        result.append(link)
-    for requirement in requirements(include_conditional=True):
-        is_linked = False
-        for link in linked:
-            if requirement.replace('-', '_').startswith(link):
-                is_linked = True
-        if not is_linked:
-            result.append(requirement)
-    return result
+    if deps_needed:
+        for e in errors:
+            logging.exception(e)
+
+        raise DependencyException(deps_needed)
 
 
 if __name__ == "__main__":
     import sys
+
     sys.stdout.writelines(req + "\n" for req in list_requirements())
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index d0ecf241b6..ba3ab1d37d 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -35,7 +35,7 @@ from twisted.web.resource import Resource
 from twisted.web.server import NOT_DONE_YET
 
 from synapse.api.errors import Codes, SynapseError
-from synapse.http.client import SpiderHttpClient
+from synapse.http.client import SimpleHttpClient
 from synapse.http.server import (
     respond_with_json,
     respond_with_json_bytes,
@@ -69,7 +69,12 @@ class PreviewUrlResource(Resource):
         self.max_spider_size = hs.config.max_spider_size
         self.server_name = hs.hostname
         self.store = hs.get_datastore()
-        self.client = SpiderHttpClient(hs)
+        self.client = SimpleHttpClient(
+            hs,
+            treq_args={"browser_like_redirects": True},
+            ip_whitelist=hs.config.url_preview_ip_range_whitelist,
+            ip_blacklist=hs.config.url_preview_ip_range_blacklist,
+        )
         self.media_repo = media_repo
         self.primary_base_path = media_repo.primary_base_path
         self.media_storage = media_storage
@@ -318,6 +323,11 @@ class PreviewUrlResource(Resource):
                 length, headers, uri, code = yield self.client.get_file(
                     url, output_stream=f, max_size=self.max_spider_size,
                 )
+            except SynapseError:
+                # Pass SynapseErrors through directly, so that the servlet
+                # handler will return a SynapseError to the client instead of
+                # blank data or a 500.
+                raise
             except Exception as e:
                 # FIXME: pass through 404s and other error messages nicely
                 logger.warn("Error downloading %s: %r", url, e)
diff --git a/tests/rest/media/v1/test_url_preview.py b/tests/rest/media/v1/test_url_preview.py
index c62f71b44a..650ce95a6f 100644
--- a/tests/rest/media/v1/test_url_preview.py
+++ b/tests/rest/media/v1/test_url_preview.py
@@ -15,21 +15,55 @@
 
 import os
 
-from mock import Mock
+import attr
+from netaddr import IPSet
 
-from twisted.internet.defer import Deferred
+from twisted.internet._resolver import HostResolution
+from twisted.internet.address import IPv4Address, IPv6Address
+from twisted.internet.error import DNSLookupError
+from twisted.python.failure import Failure
+from twisted.test.proto_helpers import AccumulatingProtocol
+from twisted.web._newclient import ResponseDone
 
 from synapse.config.repository import MediaStorageProviderConfig
-from synapse.util.logcontext import make_deferred_yieldable
 from synapse.util.module_loader import load_module
 
 from tests import unittest
+from tests.server import FakeTransport
+
+
+@attr.s
+class FakeResponse(object):
+    version = attr.ib()
+    code = attr.ib()
+    phrase = attr.ib()
+    headers = attr.ib()
+    body = attr.ib()
+    absoluteURI = attr.ib()
+
+    @property
+    def request(self):
+        @attr.s
+        class FakeTransport(object):
+            absoluteURI = self.absoluteURI
+
+        return FakeTransport()
+
+    def deliverBody(self, protocol):
+        protocol.dataReceived(self.body)
+        protocol.connectionLost(Failure(ResponseDone()))
 
 
 class URLPreviewTests(unittest.HomeserverTestCase):
 
     hijack_auth = True
     user_id = "@test:user"
+    end_content = (
+        b'<html><head>'
+        b'<meta property="og:title" content="~matrix~" />'
+        b'<meta property="og:description" content="hi" />'
+        b'</head></html>'
+    )
 
     def make_homeserver(self, reactor, clock):
 
@@ -39,6 +73,15 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         config = self.default_config()
         config.url_preview_enabled = True
         config.max_spider_size = 9999999
+        config.url_preview_ip_range_blacklist = IPSet(
+            (
+                "192.168.1.1",
+                "1.0.0.0/8",
+                "3fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff",
+                "2001:800::/21",
+            )
+        )
+        config.url_preview_ip_range_whitelist = IPSet(("1.1.1.1",))
         config.url_preview_url_blacklist = []
         config.media_store_path = self.storage_path
 
@@ -62,63 +105,50 @@ class URLPreviewTests(unittest.HomeserverTestCase):
 
     def prepare(self, reactor, clock, hs):
 
-        self.fetches = []
+        self.media_repo = hs.get_media_repository_resource()
+        self.preview_url = self.media_repo.children[b'preview_url']
 
-        def get_file(url, output_stream, max_size):
-            """
-            Returns tuple[int,dict,str,int] of file length, response headers,
-            absolute URI, and response code.
-            """
+        self.lookups = {}
 
-            def write_to(r):
-                data, response = r
-                output_stream.write(data)
-                return response
+        class Resolver(object):
+            def resolveHostName(
+                _self,
+                resolutionReceiver,
+                hostName,
+                portNumber=0,
+                addressTypes=None,
+                transportSemantics='TCP',
+            ):
 
-            d = Deferred()
-            d.addCallback(write_to)
-            self.fetches.append((d, url))
-            return make_deferred_yieldable(d)
+                resolution = HostResolution(hostName)
+                resolutionReceiver.resolutionBegan(resolution)
+                if hostName not in self.lookups:
+                    raise DNSLookupError("OH NO")
 
-        client = Mock()
-        client.get_file = get_file
+                for i in self.lookups[hostName]:
+                    resolutionReceiver.addressResolved(i[0]('TCP', i[1], portNumber))
+                resolutionReceiver.resolutionComplete()
+                return resolutionReceiver
 
-        self.media_repo = hs.get_media_repository_resource()
-        preview_url = self.media_repo.children[b'preview_url']
-        preview_url.client = client
-        self.preview_url = preview_url
+        self.reactor.nameResolver = Resolver()
 
     def test_cache_returns_correct_type(self):
+        self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
 
         request, channel = self.make_request(
-            "GET", "url_preview?url=matrix.org", shorthand=False
+            "GET", "url_preview?url=http://matrix.org", shorthand=False
         )
         request.render(self.preview_url)
         self.pump()
 
-        # We've made one fetch
-        self.assertEqual(len(self.fetches), 1)
-
-        end_content = (
-            b'<html><head>'
-            b'<meta property="og:title" content="~matrix~" />'
-            b'<meta property="og:description" content="hi" />'
-            b'</head></html>'
-        )
-
-        self.fetches[0][0].callback(
-            (
-                end_content,
-                (
-                    len(end_content),
-                    {
-                        b"Content-Length": [b"%d" % (len(end_content))],
-                        b"Content-Type": [b'text/html; charset="utf8"'],
-                    },
-                    "https://example.com",
-                    200,
-                ),
-            )
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\nContent-Type: text/html\r\n\r\n"
+            % (len(self.end_content),)
+            + self.end_content
         )
 
         self.pump()
@@ -129,14 +159,11 @@ class URLPreviewTests(unittest.HomeserverTestCase):
 
         # Check the cache returns the correct response
         request, channel = self.make_request(
-            "GET", "url_preview?url=matrix.org", shorthand=False
+            "GET", "url_preview?url=http://matrix.org", shorthand=False
         )
         request.render(self.preview_url)
         self.pump()
 
-        # Only one fetch, still, since we'll lean on the cache
-        self.assertEqual(len(self.fetches), 1)
-
         # Check the cache response has the same content
         self.assertEqual(channel.code, 200)
         self.assertEqual(
@@ -144,20 +171,17 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         )
 
         # Clear the in-memory cache
-        self.assertIn("matrix.org", self.preview_url._cache)
-        self.preview_url._cache.pop("matrix.org")
-        self.assertNotIn("matrix.org", self.preview_url._cache)
+        self.assertIn("http://matrix.org", self.preview_url._cache)
+        self.preview_url._cache.pop("http://matrix.org")
+        self.assertNotIn("http://matrix.org", self.preview_url._cache)
 
         # Check the database cache returns the correct response
         request, channel = self.make_request(
-            "GET", "url_preview?url=matrix.org", shorthand=False
+            "GET", "url_preview?url=http://matrix.org", shorthand=False
         )
         request.render(self.preview_url)
         self.pump()
 
-        # Only one fetch, still, since we'll lean on the cache
-        self.assertEqual(len(self.fetches), 1)
-
         # Check the cache response has the same content
         self.assertEqual(channel.code, 200)
         self.assertEqual(
@@ -165,78 +189,282 @@ class URLPreviewTests(unittest.HomeserverTestCase):
         )
 
     def test_non_ascii_preview_httpequiv(self):
+        self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
+
+        end_content = (
+            b'<html><head>'
+            b'<meta http-equiv="Content-Type" content="text/html; charset=windows-1251"/>'
+            b'<meta property="og:title" content="\xe4\xea\xe0" />'
+            b'<meta property="og:description" content="hi" />'
+            b'</head></html>'
+        )
 
         request, channel = self.make_request(
-            "GET", "url_preview?url=matrix.org", shorthand=False
+            "GET", "url_preview?url=http://matrix.org", shorthand=False
         )
         request.render(self.preview_url)
         self.pump()
 
-        # We've made one fetch
-        self.assertEqual(len(self.fetches), 1)
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b"Content-Type: text/html; charset=\"utf8\"\r\n\r\n"
+            )
+            % (len(end_content),)
+            + end_content
+        )
+
+        self.pump()
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(channel.json_body["og:title"], u"\u0434\u043a\u0430")
+
+    def test_non_ascii_preview_content_type(self):
+        self.lookups["matrix.org"] = [(IPv4Address, "8.8.8.8")]
 
         end_content = (
             b'<html><head>'
-            b'<meta http-equiv="Content-Type" content="text/html; charset=windows-1251"/>'
             b'<meta property="og:title" content="\xe4\xea\xe0" />'
             b'<meta property="og:description" content="hi" />'
             b'</head></html>'
         )
 
-        self.fetches[0][0].callback(
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://matrix.org", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
             (
-                end_content,
-                (
-                    len(end_content),
-                    {
-                        b"Content-Length": [b"%d" % (len(end_content))],
-                        # This charset=utf-8 should be ignored, because the
-                        # document has a meta tag overriding it.
-                        b"Content-Type": [b'text/html; charset="utf8"'],
-                    },
-                    "https://example.com",
-                    200,
-                ),
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b"Content-Type: text/html; charset=\"windows-1251\"\r\n\r\n"
             )
+            % (len(end_content),)
+            + end_content
         )
 
         self.pump()
         self.assertEqual(channel.code, 200)
         self.assertEqual(channel.json_body["og:title"], u"\u0434\u043a\u0430")
 
-    def test_non_ascii_preview_content_type(self):
+    def test_ipaddr(self):
+        """
+        IP addresses can be previewed directly.
+        """
+        self.lookups["example.com"] = [(IPv4Address, "8.8.8.8")]
 
         request, channel = self.make_request(
-            "GET", "url_preview?url=matrix.org", shorthand=False
+            "GET", "url_preview?url=http://example.com", shorthand=False
         )
         request.render(self.preview_url)
         self.pump()
 
-        # We've made one fetch
-        self.assertEqual(len(self.fetches), 1)
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\nContent-Type: text/html\r\n\r\n"
+            % (len(self.end_content),)
+            + self.end_content
+        )
 
-        end_content = (
-            b'<html><head>'
-            b'<meta property="og:title" content="\xe4\xea\xe0" />'
-            b'<meta property="og:description" content="hi" />'
-            b'</head></html>'
+        self.pump()
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            channel.json_body, {"og:title": "~matrix~", "og:description": "hi"}
         )
 
-        self.fetches[0][0].callback(
-            (
-                end_content,
-                (
-                    len(end_content),
-                    {
-                        b"Content-Length": [b"%d" % (len(end_content))],
-                        b"Content-Type": [b'text/html; charset="windows-1251"'],
-                    },
-                    "https://example.com",
-                    200,
-                ),
-            )
+    def test_blacklisted_ip_specific(self):
+        """
+        Blacklisted IP addresses, found via DNS, are not spidered.
+        """
+        self.lookups["example.com"] = [(IPv4Address, "192.168.1.1")]
+
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://example.com", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        # No requests made.
+        self.assertEqual(len(self.reactor.tcpClients), 0)
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
+
+    def test_blacklisted_ip_range(self):
+        """
+        Blacklisted IP ranges, IPs found over DNS, are not spidered.
+        """
+        self.lookups["example.com"] = [(IPv4Address, "1.1.1.2")]
+
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://example.com", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
+
+    def test_blacklisted_ip_specific_direct(self):
+        """
+        Blacklisted IP addresses, accessed directly, are not spidered.
+        """
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://192.168.1.1", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        # No requests made.
+        self.assertEqual(len(self.reactor.tcpClients), 0)
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
+
+    def test_blacklisted_ip_range_direct(self):
+        """
+        Blacklisted IP ranges, accessed directly, are not spidered.
+        """
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://1.1.1.2", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
+
+    def test_blacklisted_ip_range_whitelisted_ip(self):
+        """
+        Blacklisted but then subsequently whitelisted IP addresses can be
+        spidered.
+        """
+        self.lookups["example.com"] = [(IPv4Address, "1.1.1.1")]
+
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://example.com", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+
+        client.dataReceived(
+            b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\nContent-Type: text/html\r\n\r\n"
+            % (len(self.end_content),)
+            + self.end_content
         )
 
         self.pump()
         self.assertEqual(channel.code, 200)
-        self.assertEqual(channel.json_body["og:title"], u"\u0434\u043a\u0430")
+        self.assertEqual(
+            channel.json_body, {"og:title": "~matrix~", "og:description": "hi"}
+        )
+
+    def test_blacklisted_ip_with_external_ip(self):
+        """
+        If a hostname resolves a blacklisted IP, even if there's a
+        non-blacklisted one, it will be rejected.
+        """
+        # Hardcode the URL resolving to the IP we want.
+        self.lookups[u"example.com"] = [
+            (IPv4Address, "1.1.1.2"),
+            (IPv4Address, "8.8.8.8"),
+        ]
+
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://example.com", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
+
+    def test_blacklisted_ipv6_specific(self):
+        """
+        Blacklisted IP addresses, found via DNS, are not spidered.
+        """
+        self.lookups["example.com"] = [
+            (IPv6Address, "3fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
+        ]
+
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://example.com", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        # No requests made.
+        self.assertEqual(len(self.reactor.tcpClients), 0)
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
+
+    def test_blacklisted_ipv6_range(self):
+        """
+        Blacklisted IP ranges, IPs found over DNS, are not spidered.
+        """
+        self.lookups["example.com"] = [(IPv6Address, "2001:800::1")]
+
+        request, channel = self.make_request(
+            "GET", "url_preview?url=http://example.com", shorthand=False
+        )
+        request.render(self.preview_url)
+        self.pump()
+
+        self.assertEqual(channel.code, 403)
+        self.assertEqual(
+            channel.json_body,
+            {
+                'errcode': 'M_UNKNOWN',
+                'error': 'IP address blocked by IP blacklist entry',
+            },
+        )
diff --git a/tests/server.py b/tests/server.py
index ceec2f2d4e..db43fa0db8 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -383,8 +383,16 @@ class FakeTransport(object):
         self.disconnecting = True
 
     def pauseProducing(self):
+        if not self.producer:
+            return
+
         self.producer.pauseProducing()
 
+    def resumeProducing(self):
+        if not self.producer:
+            return
+        self.producer.resumeProducing()
+
     def unregisterProducer(self):
         if not self.producer:
             return
diff --git a/tox.ini b/tox.ini
index f5f07cb690..a0f5486829 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,9 +9,6 @@ deps =
     junitxml
     coverage
 
-    # needed by some of the tests
-    lxml
-
     # cyptography 2.2 requires setuptools >= 18.5
     #
     # older versions of virtualenv (?) give us a virtualenv with the same
@@ -33,6 +30,7 @@ setenv =
 [testenv]
 deps =
     {[base]deps}
+extras = all
 
 whitelist_externals =
     sh