From bb9b35cec0605e4bd7922058d77ba5812b4a0197 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrew@amorgan.xyz>
Date: Wed, 8 Mar 2023 16:22:10 +0000
Subject: [PATCH 1/4] Move Spam Checker callbacks to a dedicated file

The next commit updates all the uses of the spam checker (of which there
are quite a few...), hence breaking up the commits.
---
 synapse/module_api/__init__.py                | 33 +++++++++----------
 synapse/module_api/callbacks/__init__.py      | 13 +++++---
 .../callbacks/spamchecker_callbacks.py}       |  3 +-
 synapse/server.py                             |  7 +---
 4 files changed, 27 insertions(+), 29 deletions(-)
 rename synapse/{events/spamcheck.py => module_api/callbacks/spamchecker_callbacks.py} (99%)

diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index 595c23e78d7e..eeafea74d15c 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -44,20 +44,6 @@
     GET_USERS_FOR_STATES_CALLBACK,
     PresenceRouter,
 )
-from synapse.events.spamcheck import (
-    CHECK_EVENT_FOR_SPAM_CALLBACK,
-    CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK,
-    CHECK_REGISTRATION_FOR_SPAM_CALLBACK,
-    CHECK_USERNAME_FOR_SPAM_CALLBACK,
-    SHOULD_DROP_FEDERATED_EVENT_CALLBACK,
-    USER_MAY_CREATE_ROOM_ALIAS_CALLBACK,
-    USER_MAY_CREATE_ROOM_CALLBACK,
-    USER_MAY_INVITE_CALLBACK,
-    USER_MAY_JOIN_ROOM_CALLBACK,
-    USER_MAY_PUBLISH_ROOM_CALLBACK,
-    USER_MAY_SEND_3PID_INVITE_CALLBACK,
-    SpamChecker,
-)
 from synapse.events.third_party_rules import (
     CHECK_CAN_DEACTIVATE_USER_CALLBACK,
     CHECK_CAN_SHUTDOWN_ROOM_CALLBACK,
@@ -105,6 +91,20 @@
     ON_LEGACY_SEND_MAIL_CALLBACK,
     ON_USER_REGISTRATION_CALLBACK,
 )
+from synapse.module_api.callbacks.spamchecker_callbacks import (
+    CHECK_EVENT_FOR_SPAM_CALLBACK,
+    CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK,
+    CHECK_REGISTRATION_FOR_SPAM_CALLBACK,
+    CHECK_USERNAME_FOR_SPAM_CALLBACK,
+    SHOULD_DROP_FEDERATED_EVENT_CALLBACK,
+    USER_MAY_CREATE_ROOM_ALIAS_CALLBACK,
+    USER_MAY_CREATE_ROOM_CALLBACK,
+    USER_MAY_INVITE_CALLBACK,
+    USER_MAY_JOIN_ROOM_CALLBACK,
+    USER_MAY_PUBLISH_ROOM_CALLBACK,
+    USER_MAY_SEND_3PID_INVITE_CALLBACK,
+    SpamCheckerModuleApiCallbacks,
+)
 from synapse.rest.client.login import LoginResponse
 from synapse.storage import DataStore
 from synapse.storage.background_updates import (
@@ -147,7 +147,7 @@
 """
 
 PRESENCE_ALL_USERS = PresenceRouter.ALL_USERS
-NOT_SPAM = SpamChecker.NOT_SPAM
+NOT_SPAM = SpamCheckerModuleApiCallbacks.NOT_SPAM
 
 __all__ = [
     "errors",
@@ -271,7 +271,6 @@ def __init__(self, hs: "HomeServer", auth_handler: AuthHandler) -> None:
         self._public_room_list_manager = PublicRoomListManager(hs)
         self._account_data_manager = AccountDataManager(hs)
 
-        self._spam_checker = hs.get_spam_checker()
         self._third_party_event_rules = hs.get_third_party_event_rules()
         self._password_auth_provider = hs.get_password_auth_provider()
         self._presence_router = hs.get_presence_router()
@@ -305,7 +304,7 @@ def register_spam_checker_callbacks(
 
         Added in Synapse v1.37.0.
         """
-        return self._spam_checker.register_callbacks(
+        return self._callbacks.spam_checker.register_callbacks(
             check_event_for_spam=check_event_for_spam,
             should_drop_federated_event=should_drop_federated_event,
             user_may_join_room=user_may_join_room,
diff --git a/synapse/module_api/callbacks/__init__.py b/synapse/module_api/callbacks/__init__.py
index 3d977bf6558a..89b5c8d55286 100644
--- a/synapse/module_api/callbacks/__init__.py
+++ b/synapse/module_api/callbacks/__init__.py
@@ -12,11 +12,16 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.module_api.callbacks.account_validity_callbacks import (
-    AccountValidityModuleApiCallbacks,
-)
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+from .account_validity_callbacks import AccountValidityModuleApiCallbacks
+from .spamchecker_callbacks import SpamCheckerModuleApiCallbacks
 
 
 class ModuleApiCallbacks:
-    def __init__(self) -> None:
+    def __init__(self, hs: "HomeServer") -> None:
         self.account_validity = AccountValidityModuleApiCallbacks()
+        self.spam_checker = SpamCheckerModuleApiCallbacks(hs)
diff --git a/synapse/events/spamcheck.py b/synapse/module_api/callbacks/spamchecker_callbacks.py
similarity index 99%
rename from synapse/events/spamcheck.py
rename to synapse/module_api/callbacks/spamchecker_callbacks.py
index 765c15bb5135..4456d1b81eb2 100644
--- a/synapse/events/spamcheck.py
+++ b/synapse/module_api/callbacks/spamchecker_callbacks.py
@@ -286,11 +286,10 @@ def run(*args: Any, **kwargs: Any) -> Awaitable:
         api.register_spam_checker_callbacks(**hooks)
 
 
-class SpamChecker:
+class SpamCheckerModuleApiCallbacks:
     NOT_SPAM: Literal["NOT_SPAM"] = "NOT_SPAM"
 
     def __init__(self, hs: "synapse.server.HomeServer") -> None:
-        self.hs = hs
         self.clock = hs.get_clock()
 
         self._check_event_for_spam_callbacks: List[CHECK_EVENT_FOR_SPAM_CALLBACK] = []
diff --git a/synapse/server.py b/synapse/server.py
index a191c1999347..559724594b89 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -42,7 +42,6 @@
 from synapse.crypto.keyring import Keyring
 from synapse.events.builder import EventBuilderFactory
 from synapse.events.presence_router import PresenceRouter
-from synapse.events.spamcheck import SpamChecker
 from synapse.events.third_party_rules import ThirdPartyEventRules
 from synapse.events.utils import EventClientSerializer
 from synapse.federation.federation_client import FederationClient
@@ -687,10 +686,6 @@ def get_user_directory_handler(self) -> UserDirectoryHandler:
     def get_stats_handler(self) -> StatsHandler:
         return StatsHandler(self)
 
-    @cache_in_self
-    def get_spam_checker(self) -> SpamChecker:
-        return SpamChecker(self)
-
     @cache_in_self
     def get_third_party_event_rules(self) -> ThirdPartyEventRules:
         return ThirdPartyEventRules(self)
@@ -803,7 +798,7 @@ def get_module_api(self) -> ModuleApi:
 
     @cache_in_self
     def get_module_api_callbacks(self) -> ModuleApiCallbacks:
-        return ModuleApiCallbacks()
+        return ModuleApiCallbacks(self)
 
     @cache_in_self
     def get_account_data_handler(self) -> AccountDataHandler:

From 2525210daee5f961de7f3c844451564f5020216d Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrew@amorgan.xyz>
Date: Wed, 8 Mar 2023 16:22:49 +0000
Subject: [PATCH 2/4] Update calling code for the Spam Checker

It's questionable whether `NOT_SPAM` should be defined in
"SpamCheckerModuleApiCallbacks", but putting just that in a separate
class feels a bit silly.

It is still re-exported by ModuleApi, which is where modules should
be pulling it from.
---
 synapse/app/_base.py                    |  2 +-
 synapse/federation/federation_base.py   |  6 +++---
 synapse/federation/federation_server.py |  8 +++++---
 synapse/handlers/directory.py           | 14 ++++++++-----
 synapse/handlers/federation.py          |  4 ++--
 synapse/handlers/message.py             | 10 +++++++---
 synapse/handlers/register.py            |  4 ++--
 synapse/handlers/room.py                | 10 +++++++---
 synapse/handlers/room_member.py         | 22 ++++++++++++---------
 synapse/handlers/user_directory.py      |  6 ++++--
 synapse/media/media_storage.py          |  7 +++----
 tests/handlers/test_user_directory.py   |  2 +-
 tests/media/test_media_storage.py       |  2 +-
 tests/rest/client/test_rooms.py         | 26 ++++++++++++++++++-------
 tests/server.py                         |  2 +-
 15 files changed, 78 insertions(+), 47 deletions(-)

diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index f7b866978cca..954402e4d2cc 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -64,7 +64,6 @@
 from synapse.config.server import ListenerConfig, ManholeConfig, TCPListenerConfig
 from synapse.crypto import context_factory
 from synapse.events.presence_router import load_legacy_presence_router
-from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
 from synapse.handlers.auth import load_legacy_password_auth_providers
 from synapse.http.site import SynapseSite
@@ -73,6 +72,7 @@
 from synapse.metrics import install_gc_manager, register_threadpool
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.metrics.jemalloc import setup_jemalloc_stats
+from synapse.module_api.callbacks.spamchecker_callbacks import load_legacy_spam_checkers
 from synapse.types import ISynapseReactor
 from synapse.util import SYNAPSE_VERSION
 from synapse.util.caches.lrucache import setup_expire_lru_cache_entries
diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index 29fae716f589..3df975958da2 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -51,7 +51,7 @@ def __init__(self, hs: "HomeServer"):
 
         self.server_name = hs.hostname
         self.keyring = hs.get_keyring()
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self.store = hs.get_datastores().main
         self._clock = hs.get_clock()
         self._storage_controllers = hs.get_storage_controllers()
@@ -137,9 +137,9 @@ async def _check_sigs_and_hash(
                     )
             return redacted_event
 
-        spam_check = await self.spam_checker.check_event_for_spam(pdu)
+        spam_check = await self._spam_checker_module_callbacks.check_event_for_spam(pdu)
 
-        if spam_check != self.spam_checker.NOT_SPAM:
+        if spam_check != self._spam_checker_module_callbacks.NOT_SPAM:
             logger.warning("Event contains spam, soft-failing %s", pdu.event_id)
             log_kv(
                 {
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 64e99292ec04..d7740eb3b448 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -130,7 +130,7 @@ def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
         self.handler = hs.get_federation_handler()
-        self._spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self._federation_event_handler = hs.get_federation_event_handler()
         self.state = hs.get_state_handler()
         self._event_auth_handler = hs.get_event_auth_handler()
@@ -1129,7 +1129,7 @@ async def _handle_received_pdu(self, origin: str, pdu: EventBase) -> None:
             logger.warning("event id %s: %s", pdu.event_id, e)
             raise FederationError("ERROR", 403, str(e), affected=pdu.event_id)
 
-        if await self._spam_checker.should_drop_federated_event(pdu):
+        if await self._spam_checker_module_callbacks.should_drop_federated_event(pdu):
             logger.warning(
                 "Unstaged federated event contains spam, dropping %s", pdu.event_id
             )
@@ -1174,7 +1174,9 @@ async def _get_next_nonspam_staged_event_for_room(
 
             origin, event = next
 
-            if await self._spam_checker.should_drop_federated_event(event):
+            if await self._spam_checker_module_callbacks.should_drop_federated_event(
+                event
+            ):
                 logger.warning(
                     "Staged federated event contains spam, dropping %s",
                     event.event_id,
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index 1fb23cc9bf51..5e8316e2e511 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -60,7 +60,7 @@ def __init__(self, hs: "HomeServer"):
             "directory", self.on_directory_query
         )
 
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
 
     async def _create_association(
         self,
@@ -145,10 +145,12 @@ async def create_association(
                         403, "You must be in the room to create an alias for it"
                     )
 
-            spam_check = await self.spam_checker.user_may_create_room_alias(
-                user_id, room_alias
+            spam_check = (
+                await self._spam_checker_module_callbacks.user_may_create_room_alias(
+                    user_id, room_alias
+                )
             )
-            if spam_check != self.spam_checker.NOT_SPAM:
+            if spam_check != self._spam_checker_module_callbacks.NOT_SPAM:
                 raise AuthError(
                     403,
                     "This user is not permitted to create this alias",
@@ -444,7 +446,9 @@ async def edit_published_room_list(
         """
         user_id = requester.user.to_string()
 
-        spam_check = await self.spam_checker.user_may_publish_room(user_id, room_id)
+        spam_check = await self._spam_checker_module_callbacks.user_may_publish_room(
+            user_id, room_id
+        )
         if spam_check != NOT_SPAM:
             raise AuthError(
                 403,
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 65461a078723..d1a88cc60460 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -141,7 +141,7 @@ def __init__(self, hs: "HomeServer"):
         self.server_name = hs.hostname
         self.keyring = hs.get_keyring()
         self.is_mine_id = hs.is_mine_id
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self.event_creation_handler = hs.get_event_creation_handler()
         self.event_builder_factory = hs.get_event_builder_factory()
         self._event_auth_handler = hs.get_event_auth_handler()
@@ -1042,7 +1042,7 @@ async def on_invite_request(
         if self.hs.config.server.block_non_admin_invites:
             raise SynapseError(403, "This server does not accept room invites")
 
-        spam_check = await self.spam_checker.user_may_invite(
+        spam_check = await self._spam_checker_module_callbacks.user_may_invite(
             event.sender, event.state_key, event.room_id
         )
         if spam_check != NOT_SPAM:
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index a17fe3bf530b..2e964ed37e9a 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -508,7 +508,7 @@ def __init__(self, hs: "HomeServer"):
 
         self._bulk_push_rule_evaluator = hs.get_bulk_push_rule_evaluator()
 
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self.third_party_event_rules: "ThirdPartyEventRules" = (
             self.hs.get_third_party_event_rules()
         )
@@ -1035,8 +1035,12 @@ async def create_and_send_nonmember_event(
                     event.sender,
                 )
 
-                spam_check_result = await self.spam_checker.check_event_for_spam(event)
-                if spam_check_result != self.spam_checker.NOT_SPAM:
+                spam_check_result = (
+                    await self._spam_checker_module_callbacks.check_event_for_spam(
+                        event
+                    )
+                )
+                if spam_check_result != self._spam_checker_module_callbacks.NOT_SPAM:
                     if isinstance(spam_check_result, tuple):
                         try:
                             [code, dict] = spam_check_result
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index c8bf2439afb5..61c4b833bd30 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -110,7 +110,7 @@ def __init__(self, hs: "HomeServer"):
         self._server_notices_mxid = hs.config.servernotices.server_notices_mxid
         self._server_name = hs.hostname
 
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
 
         if hs.config.worker.worker_app:
             self._register_client = ReplicationRegisterServlet.make_client(hs)
@@ -259,7 +259,7 @@ async def register_user(
 
         await self.check_registration_ratelimit(address)
 
-        result = await self.spam_checker.check_registration_for_spam(
+        result = await self._spam_checker_module_callbacks.check_registration_for_spam(
             threepid,
             localpart,
             user_agent_ips or [],
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 2d69cabf43d0..efd9612d90ca 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -106,7 +106,7 @@ def __init__(self, hs: "HomeServer"):
         self.auth_blocking = hs.get_auth_blocking()
         self.clock = hs.get_clock()
         self.hs = hs
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self.event_creation_handler = hs.get_event_creation_handler()
         self.room_member_handler = hs.get_room_member_handler()
         self._event_auth_handler = hs.get_event_auth_handler()
@@ -449,7 +449,9 @@ async def clone_existing_room(
         """
         user_id = requester.user.to_string()
 
-        spam_check = await self.spam_checker.user_may_create_room(user_id)
+        spam_check = await self._spam_checker_module_callbacks.user_may_create_room(
+            user_id
+        )
         if spam_check != NOT_SPAM:
             raise SynapseError(
                 403,
@@ -761,7 +763,9 @@ async def create_room(
                 )
 
         if not is_requester_admin:
-            spam_check = await self.spam_checker.user_may_create_room(user_id)
+            spam_check = await self._spam_checker_module_callbacks.user_may_create_room(
+                user_id
+            )
             if spam_check != NOT_SPAM:
                 raise SynapseError(
                     403,
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 1d8b0aee6ff7..ec317e60239a 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -96,7 +96,7 @@ def __init__(self, hs: "HomeServer"):
         self.member_as_limiter = Linearizer(max_count=10, name="member_as_limiter")
 
         self.clock = hs.get_clock()
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self.third_party_event_rules = hs.get_third_party_event_rules()
         self._server_notices_mxid = self.config.servernotices.server_notices_mxid
         self._enable_lookup = hs.config.registration.enable_3pid_lookup
@@ -806,7 +806,7 @@ async def update_membership_locked(
                     )
                     block_invite_result = (Codes.FORBIDDEN, {})
 
-                spam_check = await self.spam_checker.user_may_invite(
+                spam_check = await self._spam_checker_module_callbacks.user_may_invite(
                     requester.user.to_string(), target_id, room_id
                 )
                 if spam_check != NOT_SPAM:
@@ -940,8 +940,10 @@ async def update_membership_locked(
                 # a room then they're allowed to join it.
                 and not new_room
             ):
-                spam_check = await self.spam_checker.user_may_join_room(
-                    target.to_string(), room_id, is_invited=inviter is not None
+                spam_check = (
+                    await self._spam_checker_module_callbacks.user_may_join_room(
+                        target.to_string(), room_id, is_invited=inviter is not None
+                    )
                 )
                 if spam_check != NOT_SPAM:
                     raise SynapseError(
@@ -1550,11 +1552,13 @@ async def do_3pid_invite(
             )
         else:
             # Check if the spamchecker(s) allow this invite to go through.
-            spam_check = await self.spam_checker.user_may_send_3pid_invite(
-                inviter_userid=requester.user.to_string(),
-                medium=medium,
-                address=address,
-                room_id=room_id,
+            spam_check = (
+                await self._spam_checker_module_callbacks.user_may_send_3pid_invite(
+                    inviter_userid=requester.user.to_string(),
+                    medium=medium,
+                    address=address,
+                    room_id=room_id,
+                )
             )
             if spam_check != NOT_SPAM:
                 raise SynapseError(
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index 28a92d41d6fc..05197edc9546 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -94,7 +94,7 @@ def __init__(self, hs: "HomeServer"):
         self.is_mine_id = hs.is_mine_id
         self.update_user_directory = hs.config.worker.should_update_user_directory
         self.search_all_users = hs.config.userdirectory.user_directory_search_all_users
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self._hs = hs
 
         # The current position in the current_state_delta stream
@@ -149,7 +149,9 @@ async def search_users(
         # Remove any spammy users from the results.
         non_spammy_users = []
         for user in results["results"]:
-            if not await self.spam_checker.check_username_for_spam(user):
+            if not await self._spam_checker_module_callbacks.check_username_for_spam(
+                user
+            ):
                 non_spammy_users.append(user)
         results["results"] = non_spammy_users
 
diff --git a/synapse/media/media_storage.py b/synapse/media/media_storage.py
index a7e22a91e115..a819d954070a 100644
--- a/synapse/media/media_storage.py
+++ b/synapse/media/media_storage.py
@@ -36,7 +36,6 @@
 from twisted.internet.interfaces import IConsumer
 from twisted.protocols.basic import FileSender
 
-import synapse
 from synapse.api.errors import NotFoundError
 from synapse.logging.context import defer_to_thread, make_deferred_yieldable
 from synapse.util import Clock
@@ -74,7 +73,7 @@ def __init__(
         self.local_media_directory = local_media_directory
         self.filepaths = filepaths
         self.storage_providers = storage_providers
-        self.spam_checker = hs.get_spam_checker()
+        self._spam_checker_module_callbacks = hs.get_module_api_callbacks().spam_checker
         self.clock = hs.get_clock()
 
     async def store_file(self, source: IO, file_info: FileInfo) -> str:
@@ -145,10 +144,10 @@ async def finish() -> None:
                     f.flush()
                     f.close()
 
-                    spam_check = await self.spam_checker.check_media_file_for_spam(
+                    spam_check = await self._spam_checker_module_callbacks.check_media_file_for_spam(
                         ReadableFileWrapper(self.clock, fname), file_info
                     )
-                    if spam_check != synapse.module_api.NOT_SPAM:
+                    if spam_check != self._spam_checker_module_callbacks.NOT_SPAM:
                         logger.info("Blocking media due to spam checker")
                         # Note that we'll delete the stored media, due to the
                         # try/except below. The media also won't be stored in
diff --git a/tests/handlers/test_user_directory.py b/tests/handlers/test_user_directory.py
index da4d24082648..15a7dc681854 100644
--- a/tests/handlers/test_user_directory.py
+++ b/tests/handlers/test_user_directory.py
@@ -792,7 +792,7 @@ async def allow_all(user_profile: UserProfile) -> bool:
             return False
 
         # Configure a spam checker that does not filter any users.
-        spam_checker = self.hs.get_spam_checker()
+        spam_checker = self.hs.get_module_api_callbacks().spam_checker
         spam_checker._check_username_for_spam_callbacks = [allow_all]
 
         # The results do not change:
diff --git a/tests/media/test_media_storage.py b/tests/media/test_media_storage.py
index 870047d0f250..f0f2da65db0b 100644
--- a/tests/media/test_media_storage.py
+++ b/tests/media/test_media_storage.py
@@ -31,7 +31,6 @@
 
 from synapse.api.errors import Codes
 from synapse.events import EventBase
-from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.http.types import QueryParams
 from synapse.logging.context import make_deferred_yieldable
 from synapse.media._base import FileInfo
@@ -39,6 +38,7 @@
 from synapse.media.media_storage import MediaStorage, ReadableFileWrapper
 from synapse.media.storage_provider import FileStorageProviderBackend
 from synapse.module_api import ModuleApi
+from synapse.module_api.callbacks.spamchecker_callbacks import load_legacy_spam_checkers
 from synapse.rest import admin
 from synapse.rest.client import login
 from synapse.server import HomeServer
diff --git a/tests/rest/client/test_rooms.py b/tests/rest/client/test_rooms.py
index a4900703c415..4d39c89f6f19 100644
--- a/tests/rest/client/test_rooms.py
+++ b/tests/rest/client/test_rooms.py
@@ -814,7 +814,9 @@ async def user_may_join_room(
             return False
 
         join_mock = Mock(side_effect=user_may_join_room)
-        self.hs.get_spam_checker()._user_may_join_room_callbacks.append(join_mock)
+        self.hs.get_module_api_callbacks().spam_checker._user_may_join_room_callbacks.append(
+            join_mock
+        )
 
         channel = self.make_request(
             "POST",
@@ -840,7 +842,9 @@ async def user_may_join_room_codes(
             return Codes.CONSENT_NOT_GIVEN
 
         join_mock = Mock(side_effect=user_may_join_room_codes)
-        self.hs.get_spam_checker()._user_may_join_room_callbacks.append(join_mock)
+        self.hs.get_module_api_callbacks().spam_checker._user_may_join_room_callbacks.append(
+            join_mock
+        )
 
         channel = self.make_request(
             "POST",
@@ -1162,7 +1166,9 @@ async def user_may_join_room(
         # `spec` argument is needed for this function mock to have `__qualname__`, which
         # is needed for `Measure` metrics buried in SpamChecker.
         callback_mock = Mock(side_effect=user_may_join_room, spec=lambda *x: None)
-        self.hs.get_spam_checker()._user_may_join_room_callbacks.append(callback_mock)
+        self.hs.get_module_api_callbacks().spam_checker._user_may_join_room_callbacks.append(
+            callback_mock
+        )
 
         # Join a first room, without being invited to it.
         self.helper.join(self.room1, self.user2, tok=self.tok2)
@@ -1227,7 +1233,9 @@ async def user_may_join_room(
         # `spec` argument is needed for this function mock to have `__qualname__`, which
         # is needed for `Measure` metrics buried in SpamChecker.
         callback_mock = Mock(side_effect=user_may_join_room, spec=lambda *x: None)
-        self.hs.get_spam_checker()._user_may_join_room_callbacks.append(callback_mock)
+        self.hs.get_module_api_callbacks().spam_checker._user_may_join_room_callbacks.append(
+            callback_mock
+        )
 
         # Join a first room, without being invited to it.
         self.helper.join(self.room1, self.user2, tok=self.tok2)
@@ -1643,7 +1651,7 @@ async def check_event_for_spam(
 
         spam_checker = SpamCheck()
 
-        self.hs.get_spam_checker()._check_event_for_spam_callbacks.append(
+        self.hs.get_module_api_callbacks().spam_checker._check_event_for_spam_callbacks.append(
             spam_checker.check_event_for_spam
         )
 
@@ -3381,7 +3389,9 @@ def test_threepid_invite_spamcheck_deprecated(self) -> None:
         # `spec` argument is needed for this function mock to have `__qualname__`, which
         # is needed for `Measure` metrics buried in SpamChecker.
         mock = Mock(return_value=make_awaitable(True), spec=lambda *x: None)
-        self.hs.get_spam_checker()._user_may_send_3pid_invite_callbacks.append(mock)
+        self.hs.get_module_api_callbacks().spam_checker._user_may_send_3pid_invite_callbacks.append(
+            mock
+        )
 
         # Send a 3PID invite into the room and check that it succeeded.
         email_to_invite = "teresa@example.com"
@@ -3446,7 +3456,9 @@ def test_threepid_invite_spamcheck(self) -> None:
             return_value=make_awaitable(synapse.module_api.NOT_SPAM),
             spec=lambda *x: None,
         )
-        self.hs.get_spam_checker()._user_may_send_3pid_invite_callbacks.append(mock)
+        self.hs.get_module_api_callbacks().spam_checker._user_may_send_3pid_invite_callbacks.append(
+            mock
+        )
 
         # Send a 3PID invite into the room and check that it succeeded.
         email_to_invite = "teresa@example.com"
diff --git a/tests/server.py b/tests/server.py
index b52ff1c4632c..a49dc90e3272 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -73,11 +73,11 @@
 from synapse.config.database import DatabaseConnectionConfig
 from synapse.config.homeserver import HomeServerConfig
 from synapse.events.presence_router import load_legacy_presence_router
-from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
 from synapse.handlers.auth import load_legacy_password_auth_providers
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import ContextResourceUsage
+from synapse.module_api.callbacks.spamchecker_callbacks import load_legacy_spam_checkers
 from synapse.server import HomeServer
 from synapse.storage import DataStore
 from synapse.storage.database import LoggingDatabaseConnection

From ad7e74d3a3ddfad75c77ba6dbc16c9185ed9a664 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrew@amorgan.xyz>
Date: Mon, 17 Apr 2023 11:25:48 -0600
Subject: [PATCH 3/4] changelog

---
 changelog.d/15453.misc | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/15453.misc

diff --git a/changelog.d/15453.misc b/changelog.d/15453.misc
new file mode 100644
index 000000000000..9981606c3226
--- /dev/null
+++ b/changelog.d/15453.misc
@@ -0,0 +1 @@
+Move various module API callback registration methods to a dedicated class.
\ No newline at end of file

From 75d3024ef0e503a0921d4bf7a651abafc45dce96 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrew@amorgan.xyz>
Date: Mon, 17 Apr 2023 18:21:14 -0600
Subject: [PATCH 4/4] make relative imports absolute

---
 synapse/module_api/callbacks/__init__.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/synapse/module_api/callbacks/__init__.py b/synapse/module_api/callbacks/__init__.py
index 89b5c8d55286..5cdb2c003a7c 100644
--- a/synapse/module_api/callbacks/__init__.py
+++ b/synapse/module_api/callbacks/__init__.py
@@ -17,8 +17,12 @@
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
-from .account_validity_callbacks import AccountValidityModuleApiCallbacks
-from .spamchecker_callbacks import SpamCheckerModuleApiCallbacks
+from synapse.module_api.callbacks.account_validity_callbacks import (
+    AccountValidityModuleApiCallbacks,
+)
+from synapse.module_api.callbacks.spamchecker_callbacks import (
+    SpamCheckerModuleApiCallbacks,
+)
 
 
 class ModuleApiCallbacks: