Extend spam checker to allow for multiple modules (#7435)

changelog.d/7435.feature

@@ -0,0 +1 @@
+Allow for using more than one spam checker module at once.

docs/sample_config.yaml

@@ -1867,10 +1867,17 @@ password_providers:
 # include_content: true
 
 
-#spam_checker:
-# module: "my_custom_project.SuperSpamChecker"
-# config:
-# example_option: 'things'
+# Spam checkers are third-party modules that can block specific actions
+# of local users, such as creating rooms and registering undesirable
+# usernames, as well as remote users by redacting incoming events.
+#
+spam_checker:
+ #- module: "my_custom_project.SuperSpamChecker"
+ # config:
+ # example_option: 'things'
+ #- module: "some_other_project.BadEventStopper"
+ # config:
+ # example_stop_events_from: ['@bad:example.com']
 
 
 # Uncomment to allow non-server-admin users to create groups on this server

docs/spam_checker.md

@@ -64,23 +64,28 @@ class ExampleSpamChecker:
 Modify the `spam_checker` section of your `homeserver.yaml` in the following
 manner:
 
-`module` should point to the fully qualified Python class that implements your
-custom logic, e.g. `my_module.ExampleSpamChecker`.
+Create a list entry with the keys `module` and `config`.
 
-`config` is a dictionary that gets passed to the spam checker class.
+* `module` should point to the fully qualified Python class that implements your
+ custom logic, e.g. `my_module.ExampleSpamChecker`.
+
+* `config` is a dictionary that gets passed to the spam checker class.
 
 ### Example
 
 This section might look like:
 
 ```yaml
 spam_checker:
- module: my_module.ExampleSpamChecker
- config:
- # Enable or disable a specific option in ExampleSpamChecker.
- my_custom_option: true
+ - module: my_module.ExampleSpamChecker
+  config:
+  # Enable or disable a specific option in ExampleSpamChecker.
+  my_custom_option: true
 ```
 
+More spam checkers can be added in tandem by appending more items to the list. An
+action is blocked when at least one of the configured spam checkers flags it.
+
 ## Examples
 
 The [Mjolnir](https://github.com/matrix-org/mjolnir) project is a full fledged

synapse/config/spam_checker.py

@@ -13,6 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from typing import Any, Dict, List, Tuple
+
+from synapse.config import ConfigError
 from synapse.util.module_loader import load_module
 
 from ._base import Config
@@ -22,16 +25,35 @@ class SpamCheckerConfig(Config):
  section = "spamchecker"
 
  def read_config(self, config, **kwargs):
- self.spam_checker = None
+ self.spam_checkers = [] # type: List[Tuple[Any, Dict]]
+
+ spam_checkers = config.get("spam_checker") or []
+ if isinstance(spam_checkers, dict):
+ # The spam_checker config option used to only support one
+ # spam checker, and thus was simply a dictionary with module
+ # and config keys. Support this old behaviour by checking
+ # to see if the option resolves to a dictionary
+ self.spam_checkers.append(load_module(spam_checkers))
+ elif isinstance(spam_checkers, list):
+ for spam_checker in spam_checkers:
+ if not isinstance(spam_checker, dict):
+ raise ConfigError("spam_checker syntax is incorrect")
 
- provider = config.get("spam_checker", None)
- if provider is not None:
- self.spam_checker = load_module(provider)
+  self.spam_checkers.append(load_module(spam_checker))
+ else:
+ raise ConfigError("spam_checker syntax is incorrect")
 
  def generate_config_section(self, **kwargs):
  return """\
- #spam_checker:
- # module: "my_custom_project.SuperSpamChecker"
- # config:
- # example_option: 'things'
+ # Spam checkers are third-party modules that can block specific actions
+ # of local users, such as creating rooms and registering undesirable
+ # usernames, as well as remote users by redacting incoming events.
+ #
+ spam_checker:
+ #- module: "my_custom_project.SuperSpamChecker"
+ # config:
+ # example_option: 'things'
+ #- module: "some_other_project.BadEventStopper"
+ # config:
+ # example_stop_events_from: ['@bad:example.com']
  """

synapse/events/spamcheck.py

@@ -15,7 +15,7 @@
 # limitations under the License.
 
 import inspect
-from typing import Dict
+from typing import Any, Dict, List
 
 from synapse.spam_checker_api import SpamCheckerApi
 
@@ -26,24 +26,17 @@
 
 class SpamChecker(object):
  def __init__(self, hs: "synapse.server.HomeServer"):
- self.spam_checker = None
+ self.spam_checkers = [] # type: List[Any]
 
- module = None
- config = None
- try:
- module, config = hs.config.spam_checker
- except Exception:
- pass
-
- if module is not None:
+ for module, config in hs.config.spam_checkers:
  # Older spam checkers don't accept the `api` argument, so we
  # try and detect support.
  spam_args = inspect.getfullargspec(module)
  if "api" in spam_args.args:
  api = SpamCheckerApi(hs)
- self.spam_checker = module(config=config, api=api)
+ self.spam_checkers.append(module(config=config, api=api))
  else:
- self.spam_checker = module(config=config)
+ self.spam_checkers.append(module(config=config))
 
  def check_event_for_spam(self, event: "synapse.events.EventBase") -> bool:
  """Checks if a given event is considered "spammy" by this server.
@@ -58,10 +51,11 @@ def check_event_for_spam(self, event: "synapse.events.EventBase") -> bool:
  Returns:
  True if the event is spammy.
  """
- if self.spam_checker is None:
- return False
+ for spam_checker in self.spam_checkers:
+ if spam_checker.check_event_for_spam(event):
+ return True
 
- return self.spam_checker.check_event_for_spam(event)
+ return False
 
  def user_may_invite(
  self, inviter_userid: str, invitee_userid: str, room_id: str
@@ -78,12 +72,14 @@ def user_may_invite(
  Returns:
  True if the user may send an invite, otherwise False
  """
- if self.spam_checker is None:
- return True
+ for spam_checker in self.spam_checkers:
+ if (
+ spam_checker.user_may_invite(inviter_userid, invitee_userid, room_id)
+ is False
+ ):
+ return False
 
- return self.spam_checker.user_may_invite(
- inviter_userid, invitee_userid, room_id
- )
+ return True
 
  def user_may_create_room(self, userid: str) -> bool:
  """Checks if a given user may create a room
@@ -96,10 +92,11 @@ def user_may_create_room(self, userid: str) -> bool:
  Returns:
  True if the user may create a room, otherwise False
  """
- if self.spam_checker is None:
- return True
+ for spam_checker in self.spam_checkers:
+ if spam_checker.user_may_create_room(userid) is False:
+ return False
 
- return self.spam_checker.user_may_create_room(userid)
+ return True
 
  def user_may_create_room_alias(self, userid: str, room_alias: str) -> bool:
  """Checks if a given user may create a room alias
@@ -113,10 +110,11 @@ def user_may_create_room_alias(self, userid: str, room_alias: str) -> bool:
  Returns:
  True if the user may create a room alias, otherwise False
  """
- if self.spam_checker is None:
- return True
+ for spam_checker in self.spam_checkers:
+ if spam_checker.user_may_create_room_alias(userid, room_alias) is False:
+ return False
 
- return self.spam_checker.user_may_create_room_alias(userid, room_alias)
+ return True
 
  def user_may_publish_room(self, userid: str, room_id: str) -> bool:
  """Checks if a given user may publish a room to the directory
@@ -130,10 +128,11 @@ def user_may_publish_room(self, userid: str, room_id: str) -> bool:
  Returns:
  True if the user may publish the room, otherwise False
  """
- if self.spam_checker is None:
- return True
+ for spam_checker in self.spam_checkers:
+ if spam_checker.user_may_publish_room(userid, room_id) is False:
+ return False
 
- return self.spam_checker.user_may_publish_room(userid, room_id)
+ return True
 
  def check_username_for_spam(self, user_profile: Dict[str, str]) -> bool:
  """Checks if a user ID or display name are considered "spammy" by this server.
@@ -150,13 +149,14 @@ def check_username_for_spam(self, user_profile: Dict[str, str]) -> bool:
  Returns:
  True if the user is spammy.
  """
- if self.spam_checker is None:
- return False
-
- # For backwards compatibility, if the method does not exist on the spam checker, fallback to not interfering.
- checker = getattr(self.spam_checker, "check_username_for_spam", None)
- if not checker:
- return False
- # Make a copy of the user profile object to ensure the spam checker
- # cannot modify it.
- return checker(user_profile.copy())
+ for spam_checker in self.spam_checkers:
+ # For backwards compatibility, only run if the method exists on the
+ # spam checker
+ checker = getattr(spam_checker, "check_username_for_spam", None)
+ if checker:
+ # Make a copy of the user profile object to ensure the spam checker
+ # cannot modify it.
+ if checker(user_profile.copy()):
+ return True
+
+ return False

tests/handlers/test_user_directory.py

@@ -185,7 +185,7 @@ def check_username_for_spam(self, user_profile):
  # Allow all users.
  return False
 
- spam_checker.spam_checker = AllowAll()
+ spam_checker.spam_checkers = [AllowAll()]
 
  # The results do not change:
  # We get one search result when searching for user2 by user1.
@@ -198,7 +198,7 @@ def check_username_for_spam(self, user_profile):
  # All users are spammy.
  return True
 
- spam_checker.spam_checker = BlockAll()
+ spam_checker.spam_checkers = [BlockAll()]
 
  # User1 now gets no search results for any of the other users.
  s = self.get_success(self.handler.search_users(u1, "user2", 10))