Merge pull request #6015 from matrix-org/erikj/ratelimit_admin_redaction

Allow use of different ratelimits for admin redactions.

2 files changed, 53 insertions, 12 deletions

diff --git a/synapse/handlers/_base.py b/synapse/handlers/_base.py
index c29c78bd65..d15c6282fb 100644
--- a/synapse/handlers/_base.py
+++ b/synapse/handlers/_base.py
@@ -45,6 +45,7 @@ class BaseHandler(object):
         self.state_handler = hs.get_state_handler()
         self.distributor = hs.get_distributor()
         self.ratelimiter = hs.get_ratelimiter()
+        self.admin_redaction_ratelimiter = hs.get_admin_redaction_ratelimiter()
         self.clock = hs.get_clock()
         self.hs = hs
 
@@ -53,7 +54,7 @@ class BaseHandler(object):
         self.event_builder_factory = hs.get_event_builder_factory()
 
     @defer.inlineCallbacks
-    def ratelimit(self, requester, update=True):
+    def ratelimit(self, requester, update=True, is_admin_redaction=False):
         """Ratelimits requests.
 
         Args:
@@ -62,6 +63,9 @@ class BaseHandler(object):
                 Set to False when doing multiple checks for one request (e.g.
                 to check up front if we would reject the request), and set to
                 True for the last call for a given request.
+            is_admin_redaction (bool): Whether this is a room admin/moderator
+                redacting an event. If so then we may apply different
+                ratelimits depending on config.
 
         Raises:
             LimitExceededError if the request should be ratelimited
@@ -90,16 +94,33 @@ class BaseHandler(object):
             messages_per_second = override.messages_per_second
             burst_count = override.burst_count
         else:
-            messages_per_second = self.hs.config.rc_message.per_second
-            burst_count = self.hs.config.rc_message.burst_count
-
-        allowed, time_allowed = self.ratelimiter.can_do_action(
-            user_id,
-            time_now,
-            rate_hz=messages_per_second,
-            burst_count=burst_count,
-            update=update,
-        )
+            # We default to different values if this is an admin redaction and
+            # the config is set
+            if is_admin_redaction and self.hs.config.rc_admin_redaction:
+                messages_per_second = self.hs.config.rc_admin_redaction.per_second
+                burst_count = self.hs.config.rc_admin_redaction.burst_count
+            else:
+                messages_per_second = self.hs.config.rc_message.per_second
+                burst_count = self.hs.config.rc_message.burst_count
+
+        if is_admin_redaction and self.hs.config.rc_admin_redaction:
+            # If we have separate config for admin redactions we use a separate
+            # ratelimiter
+            allowed, time_allowed = self.admin_redaction_ratelimiter.can_do_action(
+                user_id,
+                time_now,
+                rate_hz=messages_per_second,
+                burst_count=burst_count,
+                update=update,
+            )
+        else:
+            allowed, time_allowed = self.ratelimiter.can_do_action(
+                user_id,
+                time_now,
+                rate_hz=messages_per_second,
+                burst_count=burst_count,
+                update=update,
+            )
         if not allowed:
             raise LimitExceededError(
                 retry_after_ms=int(1000 * (time_allowed - time_now))
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 111f7c7e2f..1f8272784e 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -729,7 +729,27 @@ class EventCreationHandler(object):
         assert not self.config.worker_app
 
         if ratelimit:
-            yield self.base_handler.ratelimit(requester)
+            # We check if this is a room admin redacting an event so that we
+            # can apply different ratelimiting. We do this by simply checking
+            # it's not a self-redaction (to avoid having to look up whether the
+            # user is actually admin or not).
+            is_admin_redaction = False
+            if event.type == EventTypes.Redaction:
+                original_event = yield self.store.get_event(
+                    event.redacts,
+                    check_redacted=False,
+                    get_prev_content=False,
+                    allow_rejected=False,
+                    allow_none=True,
+                )
+
+                is_admin_redaction = (
+                    original_event and event.sender != original_event.sender
+                )
+
+            yield self.base_handler.ratelimit(
+                requester, is_admin_redaction=is_admin_redaction
+            )
 
         yield self.base_handler.maybe_kick_guest_users(event, context)