State-reset and security mitigations.

Upgrade Ruma to present.

The following are intentionally benign for activation in a later commit:

- Hydra backports not default.
- Room version 12 not default.
- Room version 12 not listed as stable.

Do not enable them manually or you can brick your database.

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/rooms/state_accessor/mod.rs

@@ -6,6 +6,7 @@ mod user_can;
 use std::sync::Arc;
 
 use async_trait::async_trait;
+use futures::{FutureExt, TryFutureExt, future::try_join};
 use ruma::{
 	EventEncryptionAlgorithm, JsOption, OwnedRoomAliasId, RoomId, UserId,
 	events::{
@@ -20,12 +21,16 @@ use ruma::{
 			join_rules::{JoinRule, RoomJoinRulesEventContent},
 			member::RoomMemberEventContent,
 			name::RoomNameEventContent,
+			power_levels::{RoomPowerLevels, RoomPowerLevelsEventContent},
 			topic::RoomTopicEventContent,
 		},
 	},
 	room::RoomType,
 };
-use tuwunel_core::{Result, err};
+use tuwunel_core::{
+	Result, err,
+	matrix::{Event, room_version, state_res::events::RoomCreateEvent},
+};
 use tuwunel_database::Map;
 
 use crate::{Dep, rooms};
@@ -69,6 +74,31 @@ impl crate::Service for Service {
 }
 
 impl Service {
+	/// Gets the effective power levels of a room, regardless of if there is an
+	/// `m.rooms.power_levels` state.
+	pub async fn get_power_levels(&self, room_id: &RoomId) -> Result<RoomPowerLevels> {
+		let create = self.get_create(room_id);
+		let power_levels = self
+			.room_state_get_content(room_id, &StateEventType::RoomPowerLevels, "")
+			.map_ok(|c: RoomPowerLevelsEventContent| c)
+			.map(Result::ok)
+			.map(Ok);
+
+		let (create, power_levels) = try_join(create, power_levels).await?;
+
+		let room_version = create.room_version()?;
+		let rules = room_version::rules(&room_version)?;
+		let creators = create.creators(&rules.authorization)?;
+
+		Ok(RoomPowerLevels::new(power_levels.into(), &rules.authorization, creators))
+	}
+
+	pub async fn get_create(&self, room_id: &RoomId) -> Result<RoomCreateEvent<impl Event>> {
+		self.room_state_get(room_id, &StateEventType::RoomCreate, "")
+			.await
+			.map(RoomCreateEvent::new)
+	}
+
 	pub async fn get_name(&self, room_id: &RoomId) -> Result<String> {
 		self.room_state_get_content(room_id, &StateEventType::RoomName, "")
 			.await

src/service/rooms/state_accessor/state.rs

@@ -321,7 +321,9 @@ pub fn state_full(
 	shortstatehash: ShortStateHash,
 ) -> impl Stream<Item = ((StateEventType, StateKey), impl Event)> + Send + '_ {
 	self.state_full_pdus(shortstatehash)
-		.ready_filter_map(|pdu| Some(((pdu.kind().clone().into(), pdu.state_key()?.into()), pdu)))
+		.ready_filter_map(|pdu| {
+			Some(((pdu.kind().to_cow_str().into(), pdu.state_key()?.into()), pdu))
+		})
 }
 
 #[implement(super::Service)]

src/service/rooms/state_accessor/user_can.rs

@@ -5,7 +5,6 @@ use ruma::{
 		room::{
 			history_visibility::{HistoryVisibility, RoomHistoryVisibilityEventContent},
 			member::{MembershipState, RoomMemberEventContent},
-			power_levels::{RoomPowerLevels, RoomPowerLevelsEventContent},
 		},
 	},
 };
@@ -44,28 +43,18 @@ pub async fn user_can_redact(
 		)));
 	}
 
-	match self
-		.room_state_get_content::<RoomPowerLevelsEventContent>(
-			room_id,
-			&StateEventType::RoomPowerLevels,
-			"",
-		)
-		.await
-	{
-		| Ok(pl_event_content) => {
-			let pl_event: RoomPowerLevels = pl_event_content.into();
-			Ok(pl_event.user_can_redact_event_of_other(sender)
-				|| pl_event.user_can_redact_own_event(sender)
-					&& match redacting_event {
-						| Ok(redacting_event) =>
-							if federation {
-								redacting_event.sender().server_name() == sender.server_name()
-							} else {
-								redacting_event.sender() == sender
-							},
-						| _ => false,
-					})
-		},
+	match self.get_power_levels(room_id).await {
+		| Ok(power_levels) => Ok(power_levels.user_can_redact_event_of_other(sender)
+			|| power_levels.user_can_redact_own_event(sender)
+				&& match redacting_event {
+					| Ok(redacting_event) =>
+						if federation {
+							redacting_event.sender().server_name() == sender.server_name()
+						} else {
+							redacting_event.sender() == sender
+						},
+					| _ => false,
+				}),
 		| _ => {
 			// Falling back on m.room.create to judge power level
 			match self