chore: Clippy fixes

Reviewed-By: Jacob Taylor <jacob@explodie.org>

Cargo.lock

@@ -916,7 +916,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "aws-lc-rs",
  "clap",
@@ -954,7 +954,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_admin"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "assign",
  "clap",
@@ -979,7 +979,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_api"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "assign",
  "async-trait",
@@ -1017,7 +1017,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_build_metadata"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "built",
  "cargo_metadata",
@@ -1025,7 +1025,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_core"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "argon2",
  "arrayvec",
@@ -1091,7 +1091,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_database"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "async-channel",
  "conduwuit_core",
@@ -1112,7 +1112,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_macros"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "cargo_toml",
  "itertools 0.14.0",
@@ -1123,7 +1123,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_router"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "assign",
  "axum",
@@ -1161,7 +1161,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_service"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "askama",
  "assign",
@@ -1211,7 +1211,7 @@ dependencies = [
 
 [[package]]
 name = "conduwuit_web"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "askama",
  "assign",
@@ -4725,7 +4725,7 @@ dependencies = [
 
 [[package]]
 name = "ruminuwuity"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "assign",
  "ruma",
@@ -6828,7 +6828,7 @@ dependencies = [
 
 [[package]]
 name = "xtask"
-version = "0.5.8"
+version = "0.5.9"
 dependencies = [
  "askama",
  "cargo_metadata",

Cargo.toml

@@ -12,7 +12,7 @@ license = "Apache-2.0"
 # See also `rust-toolchain.toml`
 readme = "README.md"
 repository = "https://forgejo.ellis.link/continuwuation/continuwuity"
-version = "0.5.8"
+version = "0.5.9"
 
 [workspace.metadata.crane]
 name = "conduwuit"

changelog.d/1498.doc

@@ -0,0 +1 @@
+Add performance tuning documentation. Contributed by @stratself.

changelog.d/1741.feature

@@ -0,0 +1 @@
+Add `!admin users reject-all-invites` to clean invite spam

docker/Dockerfile

@@ -50,7 +50,7 @@ EOF
 
 # Developer tool versions
 # renovate: datasource=github-releases depName=cargo-bins/cargo-binstall
-ENV BINSTALL_VERSION=1.19.0
+ENV BINSTALL_VERSION=1.19.1
 # renovate: datasource=github-releases depName=psastras/sbom-rs
 ENV CARGO_SBOM_VERSION=0.9.1
 # renovate: datasource=crate depName=lddtree

docker/musl.Dockerfile

@@ -18,7 +18,7 @@ RUN --mount=type=cache,target=/etc/apk/cache apk add \
 
 # Developer tool versions
 # renovate: datasource=github-releases depName=cargo-bins/cargo-binstall
-ENV BINSTALL_VERSION=1.19.0
+ENV BINSTALL_VERSION=1.19.1
 # renovate: datasource=github-releases depName=psastras/sbom-rs
 ENV CARGO_SBOM_VERSION=0.9.1
 # renovate: datasource=crate depName=lddtree

docs/advanced/_meta.json

@@ -8,6 +8,11 @@
         "type": "file",
         "name": "dns",
         "label": "DNS tuning (recommended)"
+    },
+    {
+        "type": "file",
+        "name": "performance",
+        "label": "Performance tuning"
     }
 
 ]

docs/advanced/delegation.mdx

@@ -156,9 +156,11 @@ ### Serving well-known files manually
 
 ## Troubleshooting
 
-Check with the [Matrix Connectivity Tester][federation-tester] to see that it's working.
+Check that other servers can connect to you.
+Here are some tools that can help identify federation issues:
 
-[federation-tester]: https://federationtester.mtrnord.blog/
+- [Matrix Connectivity Tester](https://federationtester.mtrnord.blog/)
+- [Matrix Federation Tester](https://federationtester.matrix.org/)
 
 ### Cannot log in with web clients
 

docs/advanced/performance.mdx

@@ -0,0 +1,135 @@
+# Performance tuning
+
+Continuwuity's default configs are suited for many typical setups and scales appropriately with the size of your hardware. However, there are many scenarios where additional modifications can be made to better utilize your server resources.
+
+This page aims to outline various performance tweaks for Continuwuity and their effects. These adjustments are especially helpful for homeservers that join many large federated rooms or have many users, and it will become increasingly necessary as the Matrix network expands. As always, your mileage may vary according to your setup's specifics. If you have further discussions or recommendations, please share them in the community rooms.
+
+## DNS tuning (recommended)
+
+Please see the dedicated [DNS tuning guide](./dns.mdx).
+
+## Cache capacities
+
+If you have memory to spare, consider increasing the `cache_capacity_modifier` value to a larger number to allow more data to be stored in hot memory. This *significantly* speeds up many intensive operations (such as state resolutions) and decreases CPU usage and disk I/O. Start with a baseline of `cache_capacity_modifier = 2.0` and tune up until you are satisfied with RAM usage.
+
+On the other hand, if your system doesn't have a lot of RAM, consider decreasing the cache capacity modifier to something smaller than `1.0` to avoid low-memory issues (at the cost of higher load on disk/CPU). This recommendation also works if your system has abnormally little RAM compared to the number of CPU cores (for example, 2GB RAM for 12 cores), as cache capacities scale according to number of available cores.
+
+## Disabling some features
+
+You can disable outgoing **typing notifications** and **read markers** to reduce strain on the CPU and network when actively participating in rooms.
+
+```toml
+# disables sending read receipts
+allow_outgoing_read_receipts = false
+# disables sending typing notifications
+allow_outgoing_typing = false
+```
+
+Outgoing presence updates are also considered very expensive and have been disabled by default (`allow_outgoing_presence = false`). For more savings, you may wish to disable _all_ processing of presence entirely.
+
+```toml title=continuwuity.toml
+# disabling presence updates entirely
+allow_local_presence = false
+allow_incoming_presence = false
+allow_outgoing_presence = false
+```
+
+## Tuning database compression
+
+:::warning
+These steps SHOULD be done **before** starting Continuwuity for the first time. While switching database compression midway through is theoretically possible, this has not been tested extensively in the wild.
+:::
+
+### Changing the compression algorithm
+
+For reduced CPU usage at a tradeoff of increased storage space, consider deploying Continuwuity with the faster and less intensive `lz4` algorithm instead of `zstd` for rocksdb, and disable WAL compression entirely:
+
+```toml
+### in continuwuity.toml ###
+rocksdb_compression_algo = "lz4"
+rocksdb_wal_compression = "none"
+```
+
+This tweak can especially be helpful if you have an older or less performant CPU (e.g. a Raspberry Pi) and disk space to spare.
+
+### Increasing bottommost layer compression (`zstd` only)
+
+The bottommost layer of the database usually contains old and read-only data, so it is a suitable place for further compression. In Continuwuity, this is possible by setting `rocksdb_bottommost_compression = true` and tuning `rocksdb_bottommost_compression_level` to a more compact level than the default one used in `rocksdb_compression_level`. This tweak comes at a cost of increased CPU usage, but may prevent your database from growing too large in the long run.
+
+For those using `zstd` compression, the compression level ranges from 1 to 22. An example like this could apply:
+
+```toml
+### in continuwuity.toml ###
+rocksdb_compression_algo = "zstd"
+rocksdb_compression_level = 32767 # magic number, translates to level 3 on zstd
+rocksdb_bottommost_compression = true
+rocksdb_bottommost_compression_level = 9 # level 9 on zstd
+```
+
+For `lz4` users, the default level (`-1`) is already the most compact. You can only further decrease it to favor compression speed over ratio.
+
+Consult these documents for more information on compression tuning and levels:
+
+- [Rocksdb compression documentation][rocksdb-compression]
+- [Rocksdb default compression levels][rocksdb-compression-defaults]
+- [Zstd manual][zstd-manual]
+- [Lz4 manual][lz4-manual]
+
+[rocksdb-compression]: https://github.com/facebook/rocksdb/wiki/Compression
+[rocksdb-compression-defaults]: https://github.com/facebook/rocksdb/blob/main/include/rocksdb/options.h#L208-L217
+[zstd-manual]: https://facebook.github.io/zstd/zstd_manual.html
+[lz4-manual]: https://github.com/lz4/lz4/blob/release/doc/lz4_manual.html
+
+## Other tweaks
+
+### Using UNIX sockets
+
+If your homeserver and reverse proxy live on the same machine, you may wish to expose Continuwuity on a UNIX socket instead of a port. This removes TCP overhead between the two programs.
+
+<details>
+
+<summary>Example config with Caddy</summary>
+
+```toml
+### in continuwuity.toml ###
+
+# `address` and `port` has to be commented out first
+#address = ["127.0.0.1", "::1"]
+#port = 8008
+unix_socket_path = "/run/continuwuity/continuwuity.sock"
+```
+
+```
+### in your Caddyfile ###
+https://matrix.example.com {
+    reverse_proxy unix//run/continuwuity/continuwuity.sock
+
+    # alternatively, use the http2-plaintext protocol
+    # reverse_proxy unix+h2c//run/continuwuity/continuwuity.sock
+}
+```
+
+</details>
+
+### Tuning your trusted servers
+
+:::info Vet your trusted servers!
+Trusted servers are your first point of contact when obtaining public keys from other servers, and they could theoretically impersonate other servers and cause significant harm to your deployment. Please thoroughly verify your trusted servers' credibility before adding them to your configuration.
+:::
+
+Trusted servers are queried sequentially in the order they are listed. If you have multiple trusted servers configured, put the faster ones first:
+
+```toml
+# Example config, using maintainers' recommended homeservers
+trusted_servers = ["codestorm.net","starstruck.systems","unredacted.org","matrix.org"]
+```
+
+Avoid prioritising `matrix.org` as your primary trusted server, as it tends to be quite slow.
+
+Some users have also reported that increasing `trusted_server_batch_size` has helped with faster joins for huge rooms. Start with doubling the default to `2048` until you find a suitable value.
+
+### Enable HTTP/3 on your reverse proxy
+
+Consider enabling the newer **HTTP/3** protocol for inbound connections to Continuwuity. In Caddy HTTP/3 is allowed by default, but you must expose port :443/**udp** on your firewall.
+
+HTTP/3 can vastly improve Client-Server connections especially on unstable networks, as it reduces packet losses and latency from TCP head-of-line blocking, includes workarounds for network switching, and reduces connection establishment handshakes. Continuwuity also includes experimental _outbound_ HTTP/3 support in its Docker images, so connections between Continuwuity servers can benefit from this too.

docs/deploying/generic.mdx

@@ -268,9 +268,13 @@ ## Starting Your Server
 
 ## How do I know it works?
 
-To check if your server can communicate with other homeservers, use the
-[Matrix Federation Tester](https://federationtester.mtrnord.blog/). If you can
-register your account but cannot join federated rooms, check your configuration
+To check if your server can communicate with other homeservers,
+use an external testing tool:
+
+- [Matrix Connectivity Tester](https://federationtester.mtrnord.blog/)
+- [Matrix Federation Tester](https://federationtester.matrix.org/)
+
+If you can register your account but cannot join federated rooms, check your configuration
 and verify that your federation endpoints are opened and forwarded correctly.
 
 As a quick health check, you can also use these cURL commands:

docs/public/.well-known/continuwuity/announcements

@@ -6,10 +6,10 @@
             "message": "Welcome to Continuwuity! Important announcements about the project will appear here."
         },
         {
-            "id": 12,
-            "mention_room": false,
-            "date": "2026-04-24",
-            "message": "[v0.5.8](https://forgejo.ellis.link/continuwuation/continuwuity/releases/tag/v0.5.8) is out! This is a patch release which fixes a bug in 0.5.7's email support -- upgrade soon if you use that feature."
+            "id": 13,
+            "mention_room": true,
+            "date": "2026-05-08",
+            "message": "[v0.5.9](https://forgejo.ellis.link/continuwuation/continuwuity/releases/tag/v0.5.9) has been released, fixing a few low-severity federation-related vulnerabilities. It is recommended you read the changelog and update as soon as possible. There are no new features or other changes in this release, only related bugfixes. Deployments tracking the main branch should also update to the latest commit."
         }
     ]
 }

src/admin/federation/commands.rs

@@ -102,10 +102,6 @@ pub(super) async fn remote_user_in_rooms(&self, user_id: OwnedUserId) -> Result
 		);
 	}
 
-	if !self.services.users.exists(&user_id).await {
-		return Err!("Remote user does not exist in our database.",);
-	}
-
 	let mut rooms: Vec<(OwnedRoomId, u64, String)> = self
 		.services
 		.rooms

src/admin/user/commands.rs

@@ -4,8 +4,7 @@
 };
 
 use api::client::{
-	full_user_deactivate, join_room_by_id_helper, leave_room, recreate_push_rules_and_return,
-	remote_leave_room,
+	full_user_deactivate, leave_room, recreate_push_rules_and_return, remote_leave_room,
 };
 use conduwuit::{
 	Err, Result, debug_warn, error, info,
@@ -135,17 +134,20 @@ pub(super) async fn create_user(&self, username: String, password: Option<String
 			}
 
 			if let Some(room_server_name) = room.server_name() {
-				match join_room_by_id_helper(
-					self.services,
-					&user_id,
-					&room_id,
-					Some("Automatically joining this room upon registration".to_owned()),
-					&[
-						self.services.globals.server_name().to_owned(),
-						room_server_name.to_owned(),
-					],
-				)
-				.await
+				match self
+					.services
+					.rooms
+					.membership
+					.join_room(
+						&user_id,
+						&room_id,
+						Some("Automatically joining this room upon registration".to_owned()),
+						&[
+							self.services.globals.server_name().to_owned(),
+							room_server_name.to_owned(),
+						],
+					)
+					.await
 				{
 					| Ok(_response) => {
 						info!("Automatically joined room {room} for user {user_id}");
@@ -427,6 +429,82 @@ pub(super) async fn deactivate_all(&self, no_leave_rooms: bool, force: bool) ->
 	.await
 }
 
+#[admin_command]
+pub(super) async fn list_invited_rooms(&self, user_id: String) -> Result {
+	// Validate user id
+	let user_id = parse_local_user_id(self.services, &user_id)?;
+
+	let mut rooms: Vec<((OwnedRoomId, u64, String), Result<OwnedUserId>)> = self
+		.services
+		.rooms
+		.state_cache
+		.rooms_invited(&user_id)
+		.then(async |(room_id, _)| {
+			let sender = self
+				.services
+				.rooms
+				.state_cache
+				.invite_sender(&user_id, &room_id)
+				.await;
+			(get_room_info(self.services, &room_id).await, sender)
+		})
+		.collect()
+		.await;
+
+	if rooms.is_empty() {
+		return Err!("User is not invited to any rooms.");
+	}
+
+	rooms.sort_by_key(|r| r.0.1);
+	rooms.reverse();
+
+	let body = rooms
+		.iter()
+		.map(|((id, members, name), sender)| match sender {
+			| Ok(user_id) =>
+				format!("{id}\tInviter: {user_id}\tMembers: {members}\tName: {name}"),
+			| Err(_) => format!("{id}\tMembers: {members}\tName: {name}"),
+		})
+		.collect::<Vec<_>>()
+		.join("\n");
+
+	self.write_str(&format!("Rooms {user_id} is Invited to ({}):\n```\n{body}\n```", rooms.len()))
+		.await
+}
+
+#[admin_command]
+pub(super) async fn reject_all_invites(&self, user_id: String) -> Result {
+	let user_id = parse_local_user_id(self.services, &user_id)?;
+
+	assert!(
+		self.services.globals.user_is_local(&user_id),
+		"Parsed user_id must be a local user"
+	);
+
+	let fails = self
+		.services
+		.rooms
+		.state_cache
+		.rooms_invited(&user_id)
+		.filter_map(async |(room_id, _)| {
+			match leave_room(self.services, &user_id, &room_id, None).await {
+				| Err(ref e) => {
+					warn!(%user_id, "Failed to leave {room_id}: {e}");
+					Some(())
+				},
+				| Ok(()) => None,
+			}
+		})
+		.count()
+		.await;
+
+	if fails > 0 {
+		return Err!("{fails} invites could not be rejected");
+	}
+
+	self.write_str("Successfully rejected all invites.").await
+}
+
 #[admin_command]
 pub(super) async fn list_joined_rooms(&self, user_id: String) -> Result {
 	// Validate user id
@@ -552,14 +630,12 @@ pub(super) async fn force_join_list_of_local_users(
 	let mut successful_joins: usize = 0;
 
 	for user_id in user_ids {
-		match join_room_by_id_helper(
-			self.services,
-			&user_id,
-			&room_id,
-			Some(String::from(BULK_JOIN_REASON)),
-			&servers,
-		)
-		.await
+		match self
+			.services
+			.rooms
+			.membership
+			.join_room(&user_id, &room_id, Some(String::from(BULK_JOIN_REASON)), &servers)
+			.await
 		{
 			| Ok(_res) => {
 				successful_joins = successful_joins.saturating_add(1);
@@ -635,14 +711,12 @@ pub(super) async fn force_join_all_local_users(
 		.collect::<Vec<_>>()
 		.await
 	{
-		match join_room_by_id_helper(
-			self.services,
-			user_id,
-			&room_id,
-			Some(String::from(BULK_JOIN_REASON)),
-			&servers,
-		)
-		.await
+		match self
+			.services
+			.rooms
+			.membership
+			.join_room(user_id, &room_id, Some(String::from(BULK_JOIN_REASON)), &servers)
+			.await
 		{
 			| Ok(_res) => {
 				successful_joins = successful_joins.saturating_add(1);
@@ -679,7 +753,11 @@ pub(super) async fn force_join_room(
 		self.services.globals.user_is_local(&user_id),
 		"Parsed user_id must be a local user"
 	);
-	join_room_by_id_helper(self.services, &user_id, &room_id, None, &servers).await?;
+	self.services
+		.rooms
+		.membership
+		.join_room(&user_id, &room_id, None, &servers)
+		.await?;
 
 	self.write_str(&format!("{user_id} has been joined to {room_id}."))
 		.await

src/admin/user/mod.rs

@@ -160,6 +160,17 @@ pub enum UserCommand {
 	#[clap(alias = "list")]
 	ListUsers,
 
+	/// Lists all the rooms (local and remote) that the specified user is
+	///   invited to
+	ListInvitedRooms {
+		user_id: String,
+	},
+
+	/// Manually make a user reject all current invites
+	RejectAllInvites {
+		user_id: String,
+	},
+
 	/// Lists all the rooms (local and remote) that the specified user is
 	///   joined in
 	ListJoinedRooms {

src/api/client/account/mod.rs

@@ -26,7 +26,7 @@
 };
 use service::{mailer::messages, uiaa::Identity, users::HashedPassword};
 
-use super::{DEVICE_ID_LENGTH, TOKEN_LENGTH, join_room_by_id_helper};
+use super::{DEVICE_ID_LENGTH, TOKEN_LENGTH};
 use crate::Ruma;
 
 pub(crate) mod register;

src/api/client/account/register.rs

@@ -29,7 +29,7 @@
 use serde_json::value::RawValue;
 use service::{mailer::messages, users::HashedPassword};
 
-use super::{DEVICE_ID_LENGTH, TOKEN_LENGTH, join_room_by_id_helper};
+use super::{DEVICE_ID_LENGTH, TOKEN_LENGTH};
 use crate::Ruma;
 
 const RANDOM_USER_ID_LENGTH: usize = 10;
@@ -278,15 +278,17 @@ pub(crate) async fn register_route(
 			}
 
 			if let Some(room_server_name) = room.server_name() {
-				match join_room_by_id_helper(
-					&services,
-					&user_id,
-					&room_id,
-					Some("Automatically joining this room upon registration".to_owned()),
-					&[services.globals.server_name().to_owned(), room_server_name.to_owned()],
-				)
-				.boxed()
-				.await
+				match services
+					.rooms
+					.membership
+					.join_room(
+						&user_id,
+						&room_id,
+						Some("Automatically joining this room upon registration".to_owned()),
+						&[services.globals.server_name().to_owned(), room_server_name.to_owned()],
+					)
+					.boxed()
+					.await
 				{
 					| Err(e) => {
 						// don't return this error so we don't fail registrations

src/api/client/membership/join.rs

@@ -1,57 +1,18 @@
-use std::{borrow::Borrow, collections::HashMap, iter::once, sync::Arc};
-
 use axum::extract::State;
 use axum_client_ip::ClientIp;
 use conduwuit::{
-	Err, Result, debug, debug_info, debug_warn, err, error, info, is_true,
-	matrix::{
-		StateKey,
-		event::{gen_event_id, gen_event_id_canonical_json},
-		pdu::{PartialPdu, PduEvent},
-		state_res,
-	},
+	Err, Result, debug,
 	result::FlatOk,
-	trace,
-	utils::{
-		self, shuffle,
-		stream::{IterStream, ReadyExt},
-		to_canonical_object,
-	},
-	warn,
+	utils::{shuffle, stream::IterStream},
 };
-use futures::{FutureExt, StreamExt, TryFutureExt};
+use futures::{FutureExt, StreamExt};
 use ruma::{
-	CanonicalJsonObject, CanonicalJsonValue, OwnedRoomId, OwnedServerName, OwnedUserId, RoomId,
-	RoomVersionId, UserId,
-	api::{
-		client::membership::{join_room_by_id, join_room_by_id_or_alias},
-		error::{ErrorKind, IncompatibleRoomVersionErrorData},
-		federation::{self},
-	},
-	canonical_json::to_canonical_value,
-	events::{
-		StateEventType,
-		room::{
-			join_rules::JoinRule,
-			member::{MembershipState, RoomMemberEventContent},
-		},
-	},
+	OwnedRoomId, OwnedServerName, OwnedUserId, UserId,
+	api::client::membership::{join_room_by_id, join_room_by_id_or_alias},
 };
-use service::{
-	Services,
-	rooms::{
-		state::RoomMutexGuard,
-		state_compressor::{CompressedState, HashSetCompressStateEvent},
-		timeline::pdu_fits,
-	},
-};
-use tokio::join;
 
-use super::{banned_room_check, validate_remote_member_event_stub};
-use crate::{
-	Ruma,
-	server::{select_authorising_user, user_can_perform_restricted_join},
-};
+use super::banned_room_check;
+use crate::Ruma;
 
 /// # `POST /_matrix/client/r0/rooms/{roomId}/join`
 ///
@@ -111,9 +72,14 @@ pub(crate) async fn join_room_by_id_route(
 	shuffle(&mut servers);
 	let servers = deprioritize(servers, &services.config.deprioritize_joins_through_servers);
 
-	join_room_by_id_helper(&services, sender_user, &body.room_id, body.reason.clone(), &servers)
+	let room_id = services
+		.rooms
+		.membership
+		.join_room(sender_user, &body.room_id, body.reason.clone(), &servers)
 		.boxed()
-		.await
+		.await?;
+
+	Ok(join_room_by_id::v3::Response::new(room_id))
 }
 
 /// # `POST /_matrix/client/r0/join/{roomIdOrAlias}`
@@ -226,632 +192,14 @@ pub(crate) async fn join_room_by_id_or_alias_route(
 	};
 
 	let servers = deprioritize(servers, &services.config.deprioritize_joins_through_servers);
-	let join_room_response =
-		join_room_by_id_helper(&services, sender_user, &room_id, body.reason.clone(), &servers)
-			.boxed()
-			.await?;
-
-	Ok(join_room_by_id_or_alias::v3::Response::new(join_room_response.room_id))
-}
-
-pub async fn join_room_by_id_helper(
-	services: &Services,
-	sender_user: &UserId,
-	room_id: &RoomId,
-	reason: Option<String>,
-	servers: &[OwnedServerName],
-) -> Result<join_room_by_id::v3::Response> {
-	let state_lock = services.rooms.state.mutex.lock(room_id).await;
-
-	if services
+	let room_id = services
 		.rooms
-		.state_cache
-		.is_joined(sender_user, room_id)
-		.await
-	{
-		debug_warn!("{sender_user} is already joined in {room_id}");
-		return Ok(join_room_by_id::v3::Response::new(room_id.to_owned()));
-	}
-
-	if let Err(e) = services
-		.antispam
-		.user_may_join_room(
-			sender_user.to_owned(),
-			room_id.to_owned(),
-			services
-				.rooms
-				.state_cache
-				.is_invited(sender_user, room_id)
-				.await,
-		)
-		.await
-	{
-		warn!("Antispam prevented user {} from joining room {}: {}", sender_user, room_id, e);
-		return Err!(Request(Forbidden("You are not allowed to join this room.")));
-	}
-
-	let server_in_room = services
-		.rooms
-		.state_cache
-		.server_in_room(services.globals.server_name(), room_id)
-		.await;
-
-	// Only check our known membership if we're already in the room.
-	// See: https://forgejo.ellis.link/continuwuation/continuwuity/issues/855
-	let membership = if server_in_room {
-		services
-			.rooms
-			.state_accessor
-			.get_member(room_id, sender_user)
-			.await
-	} else {
-		debug!("Ignoring local state for join {room_id}, we aren't in the room yet.");
-		Ok(RoomMemberEventContent::new(MembershipState::Leave))
-	};
-	if let Ok(m) = membership {
-		if m.membership == MembershipState::Ban {
-			debug_warn!("{sender_user} is banned from {room_id} but attempted to join");
-			// TODO: return reason
-			return Err!(Request(Forbidden("You are banned from the room.")));
-		}
-	}
-
-	if !server_in_room && servers.is_empty() {
-		return Err!(Request(NotFound(
-			"No servers were provided to assist in joining the room remotely, and we are not \
-			 already participating in the room."
-		)));
-	}
-
-	if services.antispam.check_all_joins() {
-		if let Err(e) = services
-			.antispam
-			.meowlnir_accept_make_join(room_id.to_owned(), sender_user.to_owned())
-			.await
-		{
-			warn!("Antispam prevented user {} from joining room {}: {}", sender_user, room_id, e);
-			return Err!(Request(Forbidden("Antispam rejected join request.")));
-		}
-	}
-
-	if server_in_room {
-		join_room_by_id_helper_local(services, sender_user, room_id, reason, servers, state_lock)
-			.boxed()
-			.await?;
-	} else {
-		// Ask a remote server if we are not participating in this room
-		join_room_by_id_helper_remote(
-			services,
-			sender_user,
-			room_id,
-			reason,
-			servers,
-			state_lock,
-		)
+		.membership
+		.join_room(sender_user, &room_id, body.reason.clone(), &servers)
 		.boxed()
 		.await?;
-	}
-	Ok(join_room_by_id::v3::Response::new(room_id.to_owned()))
-}
 
-#[tracing::instrument(skip_all, fields(%sender_user, %room_id), name = "join_remote", level = "info")]
-async fn join_room_by_id_helper_remote(
-	services: &Services,
-	sender_user: &UserId,
-	room_id: &RoomId,
-	reason: Option<String>,
-	servers: &[OwnedServerName],
-	state_lock: RoomMutexGuard,
-) -> Result {
-	info!("Joining {room_id} over federation.");
-
-	let (make_join_response, remote_server) =
-		make_join_request(services, sender_user, room_id, servers).await?;
-
-	info!("make_join finished");
-
-	let room_version = make_join_response.room_version.unwrap_or(RoomVersionId::V1);
-	let room_version_rules = room_version
-		.rules()
-		.expect("room version should have defined rules");
-
-	if !services.server.supported_room_version(&room_version) {
-		// How did we get here?
-		return Err!(BadServerResponse("Remote room version {room_version} is not supported"));
-	}
-
-	let mut join_event_stub: CanonicalJsonObject =
-		serde_json::from_str(make_join_response.event.get()).map_err(|e| {
-			err!(BadServerResponse(warn!(
-				"Invalid make_join event json received from server: {e:?}"
-			)))
-		})?;
-
-	let join_authorized_via_users_server = {
-		use RoomVersionId::*;
-		if !matches!(room_version, V1 | V2 | V3 | V4 | V5 | V6 | V7) {
-			join_event_stub
-				.get("content")
-				.map(|s| {
-					s.as_object()?
-						.get("join_authorised_via_users_server")?
-						.as_str()
-				})
-				.and_then(|s| OwnedUserId::try_from(s.unwrap_or_default()).ok())
-		} else {
-			None
-		}
-	};
-
-	join_event_stub.insert(
-		"origin_server_ts".to_owned(),
-		CanonicalJsonValue::Integer(
-			utils::millis_since_unix_epoch()
-				.try_into()
-				.expect("Timestamp is valid js_int value"),
-		),
-	);
-
-	let mut join_content = RoomMemberEventContent::new(MembershipState::Join);
-	join_content.displayname = services.users.displayname(sender_user).await.ok();
-	join_content.avatar_url = services.users.avatar_url(sender_user).await.ok();
-	join_content.blurhash = services.users.blurhash(sender_user).await.ok();
-	join_content.reason = reason;
-	join_content
-		.join_authorized_via_users_server
-		.clone_from(&join_authorized_via_users_server);
-
-	join_event_stub.insert(
-		"content".to_owned(),
-		to_canonical_value(join_content).expect("event is valid, we just created it"),
-	);
-
-	// Remove event id if it exists
-	join_event_stub.remove("event_id");
-
-	// In order to create a compatible ref hash (EventID) the `hashes` field needs
-	// to be present
-	services
-		.server_keys
-		.hash_and_sign_event(&mut join_event_stub, &room_version_rules)?;
-
-	// Generate event id
-	let event_id = gen_event_id(&join_event_stub, &room_version_rules)?;
-
-	// Add event_id back
-	join_event_stub
-		.insert("event_id".to_owned(), CanonicalJsonValue::String(event_id.clone().into()));
-
-	// It has enough fields to be called a proper event now
-	let mut join_event = join_event_stub;
-
-	info!("Asking {remote_server} for send_join in room {room_id}");
-	let send_join_request = federation::membership::create_join_event::v2::Request::new(
-		room_id.to_owned(),
-		event_id.clone(),
-		services
-			.sending
-			.convert_to_outgoing_federation_event(join_event.clone())
-			.await,
-	);
-
-	let send_join_response = match services
-		.sending
-		.send_synapse_request(&remote_server, send_join_request)
-		.await
-	{
-		| Ok(response) => response,
-		| Err(e) => {
-			error!("send_join failed: {e}");
-			return Err(e);
-		},
-	};
-
-	info!("send_join finished");
-
-	if join_authorized_via_users_server.is_some() {
-		if let Some(signed_raw) = &send_join_response.room_state.event {
-			debug_info!(
-				"There is a signed event with join_authorized_via_users_server. This room is \
-				 probably using restricted joins. Adding signature to our event"
-			);
-
-			let (signed_event_id, signed_value) =
-				gen_event_id_canonical_json(signed_raw, &room_version_rules).map_err(|e| {
-					err!(Request(BadJson(warn!(
-						"Could not convert event to canonical JSON: {e}"
-					))))
-				})?;
-
-			if signed_event_id != event_id {
-				return Err!(Request(BadJson(warn!(
-					%signed_event_id, %event_id,
-					"Server {remote_server} sent event with wrong event ID"
-				))));
-			}
-
-			match signed_value["signatures"]
-				.as_object()
-				.ok_or_else(|| {
-					err!(BadServerResponse(warn!(
-						"Server {remote_server} sent invalid signatures type"
-					)))
-				})
-				.and_then(|e| {
-					e.get(remote_server.as_str()).ok_or_else(|| {
-						err!(BadServerResponse(warn!(
-							"Server {remote_server} did not send its signature for a restricted \
-							 room"
-						)))
-					})
-				}) {
-				| Ok(signature) => {
-					join_event
-						.get_mut("signatures")
-						.expect("we created a valid pdu")
-						.as_object_mut()
-						.expect("we created a valid pdu")
-						.insert(remote_server.to_string(), signature.clone());
-				},
-				| Err(e) => {
-					warn!(
-						"Server {remote_server} sent invalid signature in send_join signatures \
-						 for event {signed_value:?}: {e:?}",
-					);
-				},
-			}
-		}
-	}
-
-	services
-		.rooms
-		.short
-		.get_or_create_shortroomid(room_id)
-		.await;
-
-	info!("Parsing join event");
-	let parsed_join_pdu = PduEvent::from_id_val(&event_id, join_event.clone())
-		.map_err(|e| err!(BadServerResponse("Invalid join event PDU: {e:?}")))?;
-
-	info!("Acquiring server signing keys for response events");
-	let resp_events = &send_join_response.room_state;
-	let resp_state = &resp_events.state;
-	let resp_auth = &resp_events.auth_chain;
-	services
-		.server_keys
-		.acquire_events_pubkeys(resp_auth.iter().chain(resp_state.iter()))
-		.await;
-
-	info!("Going through send_join response room_state");
-	let cork = services.db.cork_and_flush();
-	let state = send_join_response
-		.room_state
-		.state
-		.iter()
-		.stream()
-		.then(|pdu| {
-			services
-				.server_keys
-				.validate_and_add_event_id_no_fetch(pdu, &room_version_rules)
-				.inspect_err(|e| {
-					debug_warn!("Could not validate send_join response room_state event: {e:?}");
-				})
-				.inspect(|_| debug!("Completed validating send_join response room_state event"))
-		})
-		.ready_filter_map(Result::ok)
-		.fold(HashMap::new(), |mut state, (event_id, value)| async move {
-			let pdu = match PduEvent::from_id_val(&event_id, value.clone()) {
-				| Ok(pdu) => pdu,
-				| Err(e) => {
-					debug_warn!("Invalid PDU in send_join response: {e:?}: {value:#?}");
-					return state;
-				},
-			};
-			if !pdu_fits(&mut value.clone()) {
-				warn!(
-					"dropping incoming PDU {event_id} in room {room_id} from room join because \
-					 it exceeds 65535 bytes or is otherwise too large."
-				);
-				return state;
-			}
-			services.rooms.outlier.add_pdu_outlier(&event_id, &value);
-			if let Some(state_key) = &pdu.state_key {
-				let shortstatekey = services
-					.rooms
-					.short
-					.get_or_create_shortstatekey(&pdu.kind.to_string().into(), state_key)
-					.await;
-
-				state.insert(shortstatekey, pdu.event_id.clone());
-			}
-			state
-		})
-		.await;
-
-	drop(cork);
-
-	info!("Going through send_join response auth_chain");
-	let cork = services.db.cork_and_flush();
-	send_join_response
-		.room_state
-		.auth_chain
-		.iter()
-		.stream()
-		.then(|pdu| {
-			services
-				.server_keys
-				.validate_and_add_event_id_no_fetch(pdu, &room_version_rules)
-		})
-		.ready_filter_map(Result::ok)
-		.ready_for_each(|(event_id, value)| {
-			trace!(%event_id, "Adding PDU as an outlier from send_join auth_chain");
-			services.rooms.outlier.add_pdu_outlier(&event_id, &value);
-		})
-		.await;
-
-	drop(cork);
-
-	debug!("Running send_join auth check");
-	let fetch_state = &state;
-	let state_fetch = |k: StateEventType, s: StateKey| async move {
-		let shortstatekey = services.rooms.short.get_shortstatekey(&k, &s).await.ok()?;
-
-		let event_id = fetch_state.get(&shortstatekey)?;
-		services.rooms.timeline.get_pdu(event_id).await.ok()
-	};
-
-	let auth_check = state_res::event_auth::auth_check(
-		&room_version.rules().unwrap(),
-		&parsed_join_pdu,
-		None, // TODO: third party invite
-		|k, s| state_fetch(k.clone(), s.into()),
-		&state_fetch(StateEventType::RoomCreate, "".into())
-			.await
-			.expect("create event is missing from send_join auth"),
-	)
-	.await
-	.map_err(|e| err!(Request(Forbidden(warn!("Auth check failed: {e:?}")))))?;
-
-	if !auth_check {
-		return Err!(Request(Forbidden("Auth check failed")));
-	}
-
-	info!("Compressing state from send_join");
-	let compressed: CompressedState = services
-		.rooms
-		.state_compressor
-		.compress_state_events(state.iter().map(|(ssk, eid)| (ssk, eid.borrow())))
-		.collect()
-		.await;
-
-	debug!("Saving compressed state");
-	let HashSetCompressStateEvent {
-		shortstatehash: statehash_before_join,
-		added,
-		removed,
-	} = services
-		.rooms
-		.state_compressor
-		.save_state(room_id, Arc::new(compressed))
-		.await?;
-
-	debug!("Forcing state for new room");
-	services
-		.rooms
-		.state
-		.force_state(room_id, statehash_before_join, added, removed, &state_lock)
-		.await?;
-
-	debug!("Updating joined counts for new room");
-	services
-		.rooms
-		.state_cache
-		.update_joined_count(room_id)
-		.await;
-
-	// We append to state before appending the pdu, so we don't have a moment in
-	// time with the pdu without it's state. This is okay because append_pdu can't
-	// fail.
-	let statehash_after_join = services
-		.rooms
-		.state
-		.append_to_state(&parsed_join_pdu, room_id)
-		.await?;
-
-	info!("Appending new room join event");
-	services
-		.rooms
-		.timeline
-		.append_pdu(
-			&parsed_join_pdu,
-			join_event,
-			once(parsed_join_pdu.event_id.borrow()),
-			&state_lock,
-			room_id,
-		)
-		.await?;
-
-	info!("Setting final room state for new room");
-	// We set the room state after inserting the pdu, so that we never have a moment
-	// in time where events in the current room state do not exist
-	services
-		.rooms
-		.state
-		.set_room_state(room_id, statehash_after_join, &state_lock);
-
-	Ok(())
-}
-
-#[tracing::instrument(skip_all, fields(%sender_user, %room_id), name = "join_local", level = "info")]
-async fn join_room_by_id_helper_local(
-	services: &Services,
-	sender_user: &UserId,
-	room_id: &RoomId,
-	reason: Option<String>,
-	servers: &[OwnedServerName],
-	state_lock: RoomMutexGuard,
-) -> Result {
-	info!("Joining room locally");
-
-	let (room_version, join_rules, is_invited) = join!(
-		services.rooms.state.get_room_version(room_id),
-		services.rooms.state_accessor.get_join_rules(room_id),
-		services.rooms.state_cache.is_invited(sender_user, room_id)
-	);
-
-	let room_version = room_version?;
-	let mut auth_user: Option<OwnedUserId> = None;
-	if !is_invited && matches!(join_rules, JoinRule::Restricted(_) | JoinRule::KnockRestricted(_))
-	{
-		use RoomVersionId::*;
-		if !matches!(room_version, V1 | V2 | V3 | V4 | V5 | V6 | V7) {
-			// This is a restricted room, check if we can complete the join requirements
-			// locally.
-			let needs_auth_user =
-				user_can_perform_restricted_join(services, sender_user, room_id).await;
-			if needs_auth_user.is_ok_and(is_true!()) {
-				// If there was an error or the value is false, we'll try joining over
-				// federation. Since it's Ok(true), we can authorise this locally.
-				// If we can't select a local user, this will remain None, the join will fail,
-				// and we'll fall back to federation.
-				auth_user = select_authorising_user(services, room_id, sender_user, &state_lock)
-					.await
-					.ok();
-			}
-		}
-	}
-
-	let mut content = RoomMemberEventContent::new(MembershipState::Join);
-	content.displayname = services.users.displayname(sender_user).await.ok();
-	content.avatar_url = services.users.avatar_url(sender_user).await.ok();
-	content.blurhash = services.users.blurhash(sender_user).await.ok();
-	content.reason.clone_from(&reason);
-	content.join_authorized_via_users_server = auth_user;
-
-	// Try normal join first
-	let Err(error) = services
-		.rooms
-		.timeline
-		.build_and_append_pdu(
-			PartialPdu::state(sender_user.to_string(), &content),
-			sender_user,
-			Some(room_id),
-			&state_lock,
-		)
-		.await
-	else {
-		info!("Joined room locally");
-		return Ok(());
-	};
-
-	if servers.is_empty() || servers.len() == 1 && services.globals.server_is_ours(&servers[0]) {
-		if !services.rooms.metadata.exists(room_id).await {
-			return Err!(Request(
-				Unknown(
-					"Room was not found locally and no servers were found to help us discover it"
-				),
-				NOT_FOUND
-			));
-		}
-
-		return Err(error);
-	}
-
-	info!(
-		?error,
-		remote_servers = %servers.len(),
-		"Could not join room locally, attempting remote join",
-	);
-	join_room_by_id_helper_remote(services, sender_user, room_id, reason, servers, state_lock)
-		.await
-}
-
-async fn make_join_request(
-	services: &Services,
-	sender_user: &UserId,
-	room_id: &RoomId,
-	servers: &[OwnedServerName],
-) -> Result<(federation::membership::prepare_join_event::v1::Response, OwnedServerName)> {
-	let mut make_join_counter: usize = 1;
-
-	for remote_server in servers {
-		if services.globals.server_is_ours(remote_server) {
-			continue;
-		}
-		info!(
-			"Asking {remote_server} for make_join (attempt {make_join_counter}/{})",
-			servers.len()
-		);
-
-		let mut request = federation::membership::prepare_join_event::v1::Request::new(
-			room_id.to_owned(),
-			sender_user.to_owned(),
-		);
-		request.ver = services.server.supported_room_versions().collect();
-
-		let make_join_response = services
-			.sending
-			.send_federation_request(remote_server, request)
-			.await;
-
-		trace!("make_join response: {:?}", make_join_response);
-		make_join_counter = make_join_counter.saturating_add(1);
-
-		match make_join_response {
-			| Ok(response) => {
-				info!("Received make_join response from {remote_server}");
-				if let Err(e) = validate_remote_member_event_stub(
-					&MembershipState::Join,
-					sender_user,
-					room_id,
-					&to_canonical_object(&response.event)?,
-				) {
-					warn!("make_join response from {remote_server} failed validation: {e}");
-					continue;
-				}
-				return Ok((response, remote_server.clone()));
-			},
-			| Err(e) => match e.kind() {
-				| ErrorKind::UnableToAuthorizeJoin => {
-					info!(
-						"{remote_server} was unable to verify the joining user satisfied \
-						 restricted join requirements: {e}. Will continue trying."
-					);
-				},
-				| ErrorKind::UnableToGrantJoin => {
-					info!(
-						"{remote_server} believes the joining user satisfies restricted join \
-						 rules, but is unable to authorise a join for us. Will continue trying."
-					);
-				},
-				| ErrorKind::IncompatibleRoomVersion(IncompatibleRoomVersionErrorData {
-					room_version,
-					..
-				}) => {
-					warn!(
-						"{remote_server} reports the room we are trying to join is \
-						 v{room_version}, which we do not support."
-					);
-					return Err(e);
-				},
-				| ErrorKind::Forbidden => {
-					warn!("{remote_server} refuses to let us join: {e}.");
-					return Err(e);
-				},
-				| ErrorKind::NotFound => {
-					info!(
-						"{remote_server} does not know about {room_id}: {e}. Will continue \
-						 trying."
-					);
-				},
-				| _ => {
-					info!("{remote_server} failed to make_join: {e}. Will continue trying.");
-				},
-			},
-		}
-	}
-	info!("All {} servers were unable to assist in joining {room_id} :(", servers.len());
-	Err!(BadServerResponse("No server available to assist in joining."))
+	Ok(join_room_by_id_or_alias::v3::Response::new(room_id))
 }
 
 /// Moves deprioritized servers (if any) to the back of the list.

src/api/client/membership/knock.rs

@@ -33,12 +33,13 @@
 use service::{
 	Services,
 	rooms::{
+		membership::validate_remote_member_event_stub,
 		state::RoomMutexGuard,
 		state_compressor::{CompressedState, HashSetCompressStateEvent},
 	},
 };
 
-use super::{banned_room_check, join::join_room_by_id_helper, validate_remote_member_event_stub};
+use super::banned_room_check;
 use crate::Ruma;
 
 /// # `POST /_matrix/client/*/knock/{roomIdOrAlias}`
@@ -238,7 +239,10 @@ async fn knock_room_by_id_helper(
 			// join_room_by_id_helper We need to release the lock here and let
 			// join_room_by_id_helper acquire it again
 			drop(state_lock);
-			match join_room_by_id_helper(services, sender_user, room_id, reason.clone(), servers)
+			match services
+				.rooms
+				.membership
+				.join_room(sender_user, room_id, reason.clone(), servers)
 				.await
 			{
 				| Ok(_) => return Ok(knock_room::v3::Response::new(room_id.to_owned())),

src/api/client/membership/leave.rs

@@ -19,9 +19,8 @@
 		room::member::{MembershipState, RoomMemberEventContent},
 	},
 };
-use service::Services;
+use service::{Services, rooms::membership::validate_remote_member_event_stub};
 
-use super::validate_remote_member_event_stub;
 use crate::Ruma;
 
 /// # `POST /_matrix/client/v3/rooms/{roomId}/leave`

src/api/client/membership/mod.rs

@@ -13,16 +13,10 @@
 use axum::extract::State;
 use conduwuit::{Err, Result, warn};
 use futures::{FutureExt, StreamExt};
-use ruma::{
-	CanonicalJsonObject, OwnedRoomId, RoomId, ServerName, UserId,
-	api::client::membership::joined_rooms,
-	events::{
-		StaticEventContent,
-		room::member::{MembershipState, RoomMemberEventContent},
-	},
-};
+use ruma::{OwnedRoomId, RoomId, ServerName, UserId, api::client::membership::joined_rooms};
 use service::Services;
 
+pub use self::leave::{leave_all_rooms, leave_room, remote_leave_room};
 pub(crate) use self::{
 	ban::ban_user_route,
 	forget::forget_room_route,
@@ -34,10 +28,6 @@
 	members::{get_member_events_route, joined_members_route},
 	unban::unban_user_route,
 };
-pub use self::{
-	join::join_room_by_id_helper,
-	leave::{leave_all_rooms, leave_room, remote_leave_room},
-};
 use crate::{Ruma, client::full_user_deactivate};
 
 /// # `POST /_matrix/client/r0/joined_rooms`
@@ -159,80 +149,3 @@ pub(crate) async fn banned_room_check(
 
 	Ok(())
 }
-
-/// Validates that an event returned from a remote server by `/make_*`
-/// actually is a membership event with the expected fields.
-///
-/// Without checking this, the remote server could use the remote membership
-/// mechanism to trick our server into signing arbitrary malicious events.
-pub(crate) fn validate_remote_member_event_stub(
-	membership: &MembershipState,
-	user_id: &UserId,
-	room_id: &RoomId,
-	event_stub: &CanonicalJsonObject,
-) -> Result<()> {
-	let Some(event_type) = event_stub.get("type") else {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with missing type field"
-		));
-	};
-	if event_type != &RoomMemberEventContent::TYPE {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with invalid event type"
-		));
-	}
-
-	let Some(sender) = event_stub.get("sender") else {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with missing sender field"
-		));
-	};
-	if sender != &user_id.as_str() {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with incorrect sender"
-		));
-	}
-
-	let Some(state_key) = event_stub.get("state_key") else {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with missing state_key field"
-		));
-	};
-	if state_key != &user_id.as_str() {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with incorrect state_key"
-		));
-	}
-
-	let Some(event_room_id) = event_stub.get("room_id") else {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with missing room_id field"
-		));
-	};
-	if event_room_id != &room_id.as_str() {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with incorrect room_id"
-		));
-	}
-
-	let Some(content) = event_stub
-		.get("content")
-		.and_then(|content| content.as_object())
-	else {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with missing content field"
-		));
-	};
-	let Some(event_membership) = content.get("membership") else {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with missing membership field"
-		));
-	};
-	if event_membership != &membership.as_str() {
-		return Err!(BadServerResponse(
-			"Remote server returned member event with incorrect membership type"
-		));
-	}
-
-	Ok(())
-}

src/api/client/mod.rs

@@ -58,7 +58,7 @@
 pub(super) use media::*;
 pub(super) use media_legacy::*;
 pub(super) use membership::*;
-pub use membership::{join_room_by_id_helper, leave_all_rooms, leave_room, remote_leave_room};
+pub use membership::{leave_all_rooms, leave_room, remote_leave_room};
 pub(super) use message::*;
 pub(super) use mutual_rooms::*;
 pub(super) use openid::*;

src/core/matrix/state_res/event_auth.rs

@@ -337,8 +337,7 @@ pub async fn auth_check<E, F, Fut>(
 	// If the create event content has the field m.federate set to false and the
 	// sender domain of the event does not match the sender domain of the create
 	// event, reject.
-	if !(room_version.room_id_format == RoomIdFormatVersion::V2)
-		&& !room_create_content.federate
+	if !room_create_content.federate
 		&& room_create_event.sender().server_name() != incoming_event.sender().server_name()
 	{
 		warn!(

src/service/rooms/membership/mod.rs

@@ -0,0 +1,934 @@
+use std::{collections::HashMap, sync::Arc};
+
+use conduwuit::{
+	Err, Pdu, Result, Server, debug, debug_info, debug_warn, err, error, info, is_true,
+	matrix::{
+		StateKey,
+		event::{gen_event_id, gen_event_id_canonical_json},
+	},
+	pdu::PartialPdu,
+	state_res, trace,
+	utils::{self, IterStream, ReadyExt, to_canonical_object},
+	warn,
+};
+use database::Database;
+use futures::{FutureExt, StreamExt, TryFutureExt, join};
+use ruma::{
+	CanonicalJsonObject, CanonicalJsonValue, OwnedRoomId, OwnedServerName, OwnedUserId, RoomId,
+	RoomVersionId, UserId,
+	api::{
+		error::{ErrorKind, IncompatibleRoomVersionErrorData},
+		federation,
+	},
+	canonical_json::to_canonical_value,
+	events::{
+		StateEventType, StaticEventContent,
+		room::{
+			join_rules::RoomJoinRulesEventContent,
+			member::{MembershipState, RoomMemberEventContent},
+		},
+	},
+	room::{AllowRule, JoinRule},
+};
+
+use crate::{
+	Dep, antispam, globals,
+	rooms::{
+		metadata, outlier, short,
+		state::{self, RoomMutexGuard},
+		state_accessor, state_cache,
+		state_compressor::{self, CompressedState, HashSetCompressStateEvent},
+		timeline::{self, pdu_fits},
+	},
+	sending, server_keys, users,
+};
+
+pub struct Service {
+	services: Services,
+}
+
+struct Services {
+	server: Arc<Server>,
+	db: Arc<Database>,
+	antispam: Dep<antispam::Service>,
+	globals: Dep<globals::Service>,
+	metadata: Dep<metadata::Service>,
+	outlier: Dep<outlier::Service>,
+	sending: Dep<sending::Service>,
+	server_keys: Dep<server_keys::Service>,
+	short: Dep<short::Service>,
+	state: Dep<state::Service>,
+	state_accessor: Dep<state_accessor::Service>,
+	state_cache: Dep<state_cache::Service>,
+	state_compressor: Dep<state_compressor::Service>,
+	timeline: Dep<timeline::Service>,
+	users: Dep<users::Service>,
+}
+
+impl crate::Service for Service {
+	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
+		Ok(Arc::new(Self {
+			services: Services {
+				server: args.server.clone(),
+				db: args.db.clone(),
+				antispam: args.depend::<antispam::Service>("antispam"),
+				globals: args.depend::<globals::Service>("globals"),
+				metadata: args.depend::<metadata::Service>("metadata"),
+				outlier: args.depend::<outlier::Service>("rooms::outlier"),
+				sending: args.depend::<sending::Service>("sending"),
+				server_keys: args.depend::<server_keys::Service>("server_keys"),
+				short: args.depend::<short::Service>("rooms::short"),
+				state: args.depend::<state::Service>("rooms::state"),
+				state_accessor: args.depend::<state_accessor::Service>("rooms::state_accessor"),
+				state_cache: args.depend::<state_cache::Service>("rooms::state_cache"),
+				state_compressor: args
+					.depend::<state_compressor::Service>("rooms::state_compressor"),
+				timeline: args.depend::<timeline::Service>("rooms::timeline"),
+				users: args.depend::<users::Service>("users"),
+			},
+		}))
+	}
+
+	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
+}
+
+impl Service {
+	/// Join a local user to a room.
+	pub async fn join_room(
+		&self,
+		sender_user: &UserId,
+		room_id: &RoomId,
+		reason: Option<String>,
+		servers: &[OwnedServerName],
+	) -> Result<OwnedRoomId> {
+		assert!(self.services.globals.user_is_local(sender_user), "user should be local");
+
+		let state_lock = self.services.state.mutex.lock(room_id).await;
+
+		if self
+			.services
+			.state_cache
+			.is_joined(sender_user, room_id)
+			.await
+		{
+			debug_warn!("{sender_user} is already joined in {room_id}");
+			return Ok(room_id.to_owned());
+		}
+
+		if let Err(e) = self
+			.services
+			.antispam
+			.user_may_join_room(
+				sender_user.to_owned(),
+				room_id.to_owned(),
+				self.services
+					.state_cache
+					.is_invited(sender_user, room_id)
+					.await,
+			)
+			.await
+		{
+			warn!("Antispam prevented user {} from joining room {}: {}", sender_user, room_id, e);
+			return Err!(Request(Forbidden("You are not allowed to join this room.")));
+		}
+
+		let server_in_room = self
+			.services
+			.state_cache
+			.server_in_room(self.services.globals.server_name(), room_id)
+			.await;
+
+		// Only check our known membership if we're already in the room.
+		// See: https://forgejo.ellis.link/continuwuation/continuwuity/issues/855
+		let membership = if server_in_room {
+			self.services
+				.state_accessor
+				.get_member(room_id, sender_user)
+				.await
+		} else {
+			debug!("Ignoring local state for join {room_id}, we aren't in the room yet.");
+			Ok(RoomMemberEventContent::new(MembershipState::Leave))
+		};
+
+		if let Ok(m) = membership {
+			if m.membership == MembershipState::Ban {
+				debug_warn!("{sender_user} is banned from {room_id} but attempted to join");
+				// TODO: return reason
+				return Err!(Request(Forbidden("You are banned from the room.")));
+			}
+		}
+
+		if !server_in_room && servers.is_empty() {
+			return Err!(Request(NotFound(
+				"No servers were provided to assist in joining the room remotely, and we are \
+				 not already participating in the room."
+			)));
+		}
+
+		if self.services.antispam.check_all_joins() {
+			if let Err(e) = self
+				.services
+				.antispam
+				.meowlnir_accept_make_join(room_id.to_owned(), sender_user.to_owned())
+				.await
+			{
+				warn!(
+					"Antispam prevented user {} from joining room {}: {}",
+					sender_user, room_id, e
+				);
+				return Err!(Request(Forbidden("Antispam rejected join request.")));
+			}
+		}
+
+		if server_in_room {
+			self.join_local_room(sender_user, room_id, reason, servers, state_lock)
+				.boxed()
+				.await?;
+		} else {
+			// Ask a remote server if we are not participating in this room
+			self.join_remote_room(sender_user, room_id, reason, servers, state_lock)
+				.boxed()
+				.await?;
+		}
+
+		Ok(room_id.to_owned())
+	}
+
+	#[tracing::instrument(skip_all, fields(%sender_user, %room_id), name = "join_local", level = "info")]
+	async fn join_local_room(
+		&self,
+		sender_user: &UserId,
+		room_id: &RoomId,
+		reason: Option<String>,
+		servers: &[OwnedServerName],
+		state_lock: RoomMutexGuard,
+	) -> Result {
+		info!("Joining room locally");
+
+		let (room_version, join_rules, is_invited) = join!(
+			self.services.state.get_room_version(room_id),
+			self.services.state_accessor.get_join_rules(room_id),
+			self.services.state_cache.is_invited(sender_user, room_id)
+		);
+
+		let room_version = room_version?;
+		let room_version_rules = room_version.rules().unwrap();
+
+		let mut auth_user: Option<OwnedUserId> = None;
+		if !is_invited
+			&& matches!(join_rules, JoinRule::Restricted(_) | JoinRule::KnockRestricted(_))
+		{
+			if room_version_rules.authorization.restricted_join_rule {
+				// This is a restricted room, check if we can complete the join requirements
+				// locally.
+				let needs_auth_user = self
+					.user_can_perform_restricted_join(sender_user, room_id)
+					.await;
+				if needs_auth_user.is_ok_and(is_true!()) {
+					// If there was an error or the value is false, we'll try joining over
+					// federation. Since it's Ok(true), we can authorise this locally.
+					// If we can't select a local user, this will remain None, the join will fail,
+					// and we'll fall back to federation.
+					auth_user = self
+						.select_authorising_user(room_id, sender_user, &state_lock)
+						.await
+						.ok();
+				}
+			}
+		}
+
+		let mut content = RoomMemberEventContent::new(MembershipState::Join);
+		content.displayname = self.services.users.displayname(sender_user).await.ok();
+		content.avatar_url = self.services.users.avatar_url(sender_user).await.ok();
+		content.blurhash = self.services.users.blurhash(sender_user).await.ok();
+		content.reason.clone_from(&reason);
+		content.join_authorized_via_users_server = auth_user;
+
+		// Try normal join first
+		let Err(error) = self
+			.services
+			.timeline
+			.build_and_append_pdu(
+				PartialPdu::state(sender_user.to_string(), &content),
+				sender_user,
+				Some(room_id),
+				&state_lock,
+			)
+			.await
+		else {
+			info!("Joined room locally");
+			return Ok(());
+		};
+
+		if servers.is_empty()
+			|| servers.len() == 1 && self.services.globals.server_is_ours(&servers[0])
+		{
+			if !self.services.metadata.exists(room_id).await {
+				return Err!(Request(
+					Unknown(
+						"Room was not found locally and no servers were found to help us \
+						 discover it"
+					),
+					NOT_FOUND
+				));
+			}
+
+			return Err(error);
+		}
+
+		info!(
+			?error,
+			remote_servers = %servers.len(),
+			"Could not join room locally, attempting remote join",
+		);
+		self.join_remote_room(sender_user, room_id, reason, servers, state_lock)
+			.await
+	}
+
+	#[tracing::instrument(skip_all, fields(%sender_user, %room_id), name = "join_remote_room", level = "info")]
+	async fn join_remote_room(
+		&self,
+		sender_user: &UserId,
+		room_id: &RoomId,
+		reason: Option<String>,
+		servers: &[OwnedServerName],
+		state_lock: RoomMutexGuard,
+	) -> Result {
+		info!("Joining {room_id} over federation.");
+
+		let (make_join_response, remote_server) = self
+			.make_join_request(sender_user, room_id, servers)
+			.await?;
+
+		info!("make_join finished");
+
+		let room_version = make_join_response.room_version.unwrap_or(RoomVersionId::V1);
+		let room_version_rules = room_version
+			.rules()
+			.expect("room version should have defined rules");
+
+		if !self.services.server.supported_room_version(&room_version) {
+			// How did we get here?
+			return Err!(BadServerResponse(
+				"Remote room version {room_version} is not supported"
+			));
+		}
+
+		let mut join_event_stub: CanonicalJsonObject =
+			serde_json::from_str(make_join_response.event.get()).map_err(|e| {
+				err!(BadServerResponse(warn!(
+					"Invalid make_join event json received from server: {e:?}"
+				)))
+			})?;
+
+		let join_authorized_via_users_server = {
+			if room_version_rules
+				.signatures
+				.check_join_authorised_via_users_server
+			{
+				join_event_stub
+					.get("content")
+					.map(|s| {
+						s.as_object()?
+							.get("join_authorised_via_users_server")?
+							.as_str()
+					})
+					.and_then(|s| OwnedUserId::try_from(s.unwrap_or_default()).ok())
+			} else {
+				None
+			}
+		};
+
+		join_event_stub.insert(
+			"origin_server_ts".to_owned(),
+			CanonicalJsonValue::Integer(
+				utils::millis_since_unix_epoch()
+					.try_into()
+					.expect("Timestamp is valid js_int value"),
+			),
+		);
+
+		let mut join_content = RoomMemberEventContent::new(MembershipState::Join);
+		join_content.displayname = self.services.users.displayname(sender_user).await.ok();
+		join_content.avatar_url = self.services.users.avatar_url(sender_user).await.ok();
+		join_content.blurhash = self.services.users.blurhash(sender_user).await.ok();
+		join_content.reason = reason;
+		join_content
+			.join_authorized_via_users_server
+			.clone_from(&join_authorized_via_users_server);
+
+		join_event_stub.insert(
+			"content".to_owned(),
+			to_canonical_value(join_content).expect("event is valid, we just created it"),
+		);
+
+		// Remove event id if it exists
+		join_event_stub.remove("event_id");
+
+		// In order to create a compatible ref hash (EventID) the `hashes` field needs
+		// to be present
+		self.services
+			.server_keys
+			.hash_and_sign_event(&mut join_event_stub, &room_version_rules)?;
+
+		// Generate event id
+		let event_id = gen_event_id(&join_event_stub, &room_version_rules)?;
+
+		// Add event_id back
+		join_event_stub
+			.insert("event_id".to_owned(), CanonicalJsonValue::String(event_id.clone().into()));
+
+		// It has enough fields to be called a proper event now
+		let mut join_event = join_event_stub;
+
+		info!("Asking {remote_server} for send_join in room {room_id}");
+		let send_join_request = federation::membership::create_join_event::v2::Request::new(
+			room_id.to_owned(),
+			event_id.clone(),
+			self.services
+				.sending
+				.convert_to_outgoing_federation_event(join_event.clone())
+				.await,
+		);
+
+		let send_join_response = match self
+			.services
+			.sending
+			.send_synapse_request(&remote_server, send_join_request)
+			.await
+		{
+			| Ok(response) => response,
+			| Err(e) => {
+				error!("send_join failed: {e}");
+				return Err(e);
+			},
+		};
+
+		info!("send_join finished");
+
+		if join_authorized_via_users_server.is_some() {
+			if let Some(signed_raw) = &send_join_response.room_state.event {
+				debug_info!(
+					"There is a signed event with join_authorized_via_users_server. This room \
+					 is probably using restricted joins. Adding signature to our event"
+				);
+
+				let (signed_event_id, signed_value) =
+					gen_event_id_canonical_json(signed_raw, &room_version_rules).map_err(
+						|e| {
+							err!(Request(BadJson(warn!(
+								"Could not convert event to canonical JSON: {e}"
+							))))
+						},
+					)?;
+
+				if signed_event_id != event_id {
+					return Err!(Request(BadJson(warn!(
+						%signed_event_id, %event_id,
+						"Server {remote_server} sent event with wrong event ID"
+					))));
+				}
+
+				match signed_value["signatures"]
+					.as_object()
+					.ok_or_else(|| {
+						err!(BadServerResponse(warn!(
+							"Server {remote_server} sent invalid signatures type"
+						)))
+					})
+					.and_then(|e| {
+						e.get(remote_server.as_str()).ok_or_else(|| {
+							err!(BadServerResponse(warn!(
+								"Server {remote_server} did not send its signature for a \
+								 restricted room"
+							)))
+						})
+					}) {
+					| Ok(signature) => {
+						join_event
+							.get_mut("signatures")
+							.expect("we created a valid pdu")
+							.as_object_mut()
+							.expect("we created a valid pdu")
+							.insert(remote_server.to_string(), signature.clone());
+					},
+					| Err(e) => {
+						warn!(
+							"Server {remote_server} sent invalid signature in send_join \
+							 signatures for event {signed_value:?}: {e:?}",
+						);
+					},
+				}
+			}
+		}
+
+		self.services.short.get_or_create_shortroomid(room_id).await;
+
+		info!("Parsing join event");
+		let parsed_join_pdu = Pdu::from_id_val(&event_id, join_event.clone())
+			.map_err(|e| err!(BadServerResponse("Invalid join event PDU: {e:?}")))?;
+
+		info!("Acquiring server signing keys for response events");
+		let resp_events = &send_join_response.room_state;
+		let resp_state = &resp_events.state;
+		let resp_auth = &resp_events.auth_chain;
+		self.services
+			.server_keys
+			.acquire_events_pubkeys(resp_auth.iter().chain(resp_state.iter()))
+			.await;
+
+		info!("Going through send_join response room_state");
+		let cork = self.services.db.cork_and_flush();
+		let state = send_join_response
+			.room_state
+			.state
+			.iter()
+			.stream()
+			.then(|pdu| {
+				self.services
+					.server_keys
+					.validate_and_add_event_id_no_fetch(pdu, &room_version_rules)
+					.inspect_err(|e| {
+						debug_warn!(
+							"Could not validate send_join response room_state event: {e:?}"
+						);
+					})
+					.inspect(|_| {
+						debug!("Completed validating send_join response room_state event");
+					})
+			})
+			.ready_filter_map(Result::ok)
+			.fold(HashMap::new(), |mut state, (event_id, value)| async move {
+				let pdu = match Pdu::from_id_val(&event_id, value.clone()) {
+					| Ok(pdu) => pdu,
+					| Err(e) => {
+						debug_warn!("Invalid PDU in send_join response: {e:?}: {value:#?}");
+						return state;
+					},
+				};
+				if !pdu_fits(&mut value.clone()) {
+					warn!(
+						"dropping incoming PDU {event_id} in room {room_id} from room join \
+						 because it exceeds 65535 bytes or is otherwise too large."
+					);
+					return state;
+				}
+				self.services.outlier.add_pdu_outlier(&event_id, &value);
+				if let Some(state_key) = &pdu.state_key {
+					let shortstatekey = self
+						.services
+						.short
+						.get_or_create_shortstatekey(&pdu.kind.to_string().into(), state_key)
+						.await;
+
+					state.insert(shortstatekey, pdu.event_id.clone());
+				}
+				state
+			})
+			.await;
+
+		drop(cork);
+
+		info!("Going through send_join response auth_chain");
+		let cork = self.services.db.cork_and_flush();
+		send_join_response
+			.room_state
+			.auth_chain
+			.iter()
+			.stream()
+			.then(|pdu| {
+				self.services
+					.server_keys
+					.validate_and_add_event_id_no_fetch(pdu, &room_version_rules)
+			})
+			.ready_filter_map(Result::ok)
+			.ready_for_each(|(event_id, value)| {
+				trace!(%event_id, "Adding PDU as an outlier from send_join auth_chain");
+				self.services.outlier.add_pdu_outlier(&event_id, &value);
+			})
+			.await;
+
+		drop(cork);
+
+		debug!("Running send_join auth check");
+		let fetch_state = &state;
+		let state_fetch = |k: StateEventType, s: StateKey| async move {
+			let shortstatekey = self.services.short.get_shortstatekey(&k, &s).await.ok()?;
+
+			let event_id = fetch_state.get(&shortstatekey)?;
+			self.services.timeline.get_pdu(event_id).await.ok()
+		};
+
+		let auth_check = state_res::event_auth::auth_check(
+			&room_version.rules().unwrap(),
+			&parsed_join_pdu,
+			None, // TODO: third party invite
+			|k, s| state_fetch(k.clone(), s.into()),
+			&state_fetch(StateEventType::RoomCreate, "".into())
+				.await
+				.expect("create event is missing from send_join auth"),
+		)
+		.await
+		.map_err(|e| err!(Request(Forbidden(warn!("Auth check failed: {e:?}")))))?;
+
+		if !auth_check {
+			return Err!(Request(Forbidden("Auth check failed")));
+		}
+
+		info!("Compressing state from send_join");
+		let compressed: CompressedState = self
+			.services
+			.state_compressor
+			.compress_state_events(state.iter().map(|(ssk, eid)| (ssk, eid.as_ref())))
+			.collect()
+			.await;
+
+		debug!("Saving compressed state");
+		let HashSetCompressStateEvent {
+			shortstatehash: statehash_before_join,
+			added,
+			removed,
+		} = self
+			.services
+			.state_compressor
+			.save_state(room_id, Arc::new(compressed))
+			.await?;
+
+		debug!("Forcing state for new room");
+		self.services
+			.state
+			.force_state(room_id, statehash_before_join, added, removed, &state_lock)
+			.await?;
+
+		debug!("Updating joined counts for new room");
+		self.services.state_cache.update_joined_count(room_id).await;
+
+		// We append to state before appending the pdu, so we don't have a moment in
+		// time with the pdu without it's state. This is okay because append_pdu can't
+		// fail.
+		let statehash_after_join = self
+			.services
+			.state
+			.append_to_state(&parsed_join_pdu, room_id)
+			.await?;
+
+		info!("Appending new room join event");
+		self.services
+			.timeline
+			.append_pdu(
+				&parsed_join_pdu,
+				join_event,
+				std::iter::once(parsed_join_pdu.event_id.as_ref()),
+				&state_lock,
+				room_id,
+			)
+			.await?;
+
+		info!("Setting final room state for new room");
+		// We set the room state after inserting the pdu, so that we never have a moment
+		// in time where events in the current room state do not exist
+		self.services
+			.state
+			.set_room_state(room_id, statehash_after_join, &state_lock);
+
+		Ok(())
+	}
+
+	async fn make_join_request(
+		&self,
+		sender_user: &UserId,
+		room_id: &RoomId,
+		servers: &[OwnedServerName],
+	) -> Result<(federation::membership::prepare_join_event::v1::Response, OwnedServerName)> {
+		let mut make_join_counter: usize = 1;
+
+		for remote_server in servers {
+			if self.services.globals.server_is_ours(remote_server) {
+				continue;
+			}
+			info!(
+				"Asking {remote_server} for make_join (attempt {make_join_counter}/{})",
+				servers.len()
+			);
+
+			let mut request = federation::membership::prepare_join_event::v1::Request::new(
+				room_id.to_owned(),
+				sender_user.to_owned(),
+			);
+			request.ver = self.services.server.supported_room_versions().collect();
+
+			let make_join_response = self
+				.services
+				.sending
+				.send_federation_request(remote_server, request)
+				.await;
+
+			trace!("make_join response: {:?}", make_join_response);
+			make_join_counter = make_join_counter.saturating_add(1);
+
+			match make_join_response {
+				| Ok(response) => {
+					info!("Received make_join response from {remote_server}");
+					if let Err(e) = validate_remote_member_event_stub(
+						&MembershipState::Join,
+						sender_user,
+						room_id,
+						&to_canonical_object(&response.event)?,
+					) {
+						warn!("make_join response from {remote_server} failed validation: {e}");
+						continue;
+					}
+					return Ok((response, remote_server.clone()));
+				},
+				| Err(e) => match e.kind() {
+					| ErrorKind::UnableToAuthorizeJoin => {
+						info!(
+							"{remote_server} was unable to verify the joining user satisfied \
+							 restricted join requirements: {e}. Will continue trying."
+						);
+					},
+					| ErrorKind::UnableToGrantJoin => {
+						info!(
+							"{remote_server} believes the joining user satisfies restricted \
+							 join rules, but is unable to authorise a join for us. Will \
+							 continue trying."
+						);
+					},
+					| ErrorKind::IncompatibleRoomVersion(IncompatibleRoomVersionErrorData {
+						room_version,
+						..
+					}) => {
+						warn!(
+							"{remote_server} reports the room we are trying to join is \
+							 v{room_version}, which we do not support."
+						);
+						return Err(e);
+					},
+					| ErrorKind::Forbidden => {
+						warn!("{remote_server} refuses to let us join: {e}.");
+						return Err(e);
+					},
+					| ErrorKind::NotFound => {
+						info!(
+							"{remote_server} does not know about {room_id}: {e}. Will continue \
+							 trying."
+						);
+					},
+					| _ => {
+						info!("{remote_server} failed to make_join: {e}. Will continue trying.");
+					},
+				},
+			}
+		}
+		info!("All {} servers were unable to assist in joining {room_id} :(", servers.len());
+		Err!(BadServerResponse("No server available to assist in joining."))
+	}
+
+	/// Attempts to find a user who is able to issue an invite in the target
+	/// room.
+	pub async fn select_authorising_user<'a>(
+		&self,
+		room_id: &'a RoomId,
+		user_id: &'a UserId,
+		state_lock: &'a RoomMutexGuard,
+	) -> Result<OwnedUserId> {
+		let candidates = self.services.state_cache.local_users_in_room(room_id);
+
+		let mut candidates = std::pin::pin!(candidates);
+
+		while let Some(candidate) = candidates.next().await {
+			if self
+				.services
+				.state_accessor
+				.user_can_invite(room_id, &candidate, user_id, state_lock)
+				.await
+			{
+				return Ok(candidate);
+			}
+		}
+
+		Err!(Request(UnableToGrantJoin(
+			"No user on this server is able to assist in joining."
+		)))
+	}
+
+	/// Checks whether the given user can join the given room via a restricted
+	/// join.
+	pub(crate) async fn user_can_perform_restricted_join(
+		&self,
+		user_id: &UserId,
+		room_id: &RoomId,
+	) -> Result<bool> {
+		let Ok(join_rules_event_content) = self
+			.services
+			.state_accessor
+			.room_state_get_content::<RoomJoinRulesEventContent>(
+				room_id,
+				&StateEventType::RoomJoinRules,
+				"",
+			)
+			.await
+		else {
+			// No join rules means there's nothing to authorise (defaults to invite)
+			return Ok(false);
+		};
+
+		let (JoinRule::Restricted(r) | JoinRule::KnockRestricted(r)) =
+			join_rules_event_content.join_rule
+		else {
+			// This is not a restricted room
+			return Ok(false);
+		};
+
+		if r.allow.is_empty() {
+			// This will never be authorisable, return forbidden.
+			return Err!(Request(Forbidden("You are not invited to this room.")));
+		}
+
+		let mut could_satisfy = true;
+		for allow_rule in &r.allow {
+			match allow_rule {
+				| AllowRule::RoomMembership(membership) => {
+					if !self
+						.services
+						.state_cache
+						.server_in_room(self.services.globals.server_name(), &membership.room_id)
+						.await
+					{
+						// Since we can't check this room, mark could_satisfy as false
+						// so that we can return M_UNABLE_TO_AUTHORIZE_JOIN later.
+						could_satisfy = false;
+						continue;
+					}
+
+					if self
+						.services
+						.state_cache
+						.is_joined(user_id, &membership.room_id)
+						.await
+					{
+						debug!(
+							"User {} is allowed to join room {} via membership in room {}",
+							user_id, room_id, membership.room_id
+						);
+						return Ok(true);
+					}
+				},
+				| other if other.rule_type() == "fi.mau.spam_checker" =>
+					return match self
+						.services
+						.antispam
+						.meowlnir_accept_make_join(room_id.to_owned(), user_id.to_owned())
+						.await
+					{
+						| Ok(()) => Ok(true),
+						| Err(_) => Err!(Request(Forbidden("Antispam rejected join request."))),
+					},
+				| _ => {
+					// We don't recognise this join rule, so we cannot satisfy the request.
+					could_satisfy = false;
+					debug_info!(
+						"Unsupported allow rule in restricted join for room {}: {:?}",
+						room_id,
+						allow_rule
+					);
+				},
+			}
+		}
+
+		if could_satisfy {
+			// We were able to check all the restrictions and can be certain that the
+			// prospective member is not permitted to join.
+			Err!(Request(Forbidden(
+				"You do not belong to any of the rooms or spaces required to join this room."
+			)))
+		} else {
+			// We were unable to check all the restrictions. This usually means we aren't in
+			// one of the rooms this one is restricted to, ergo can't check its state for
+			// the user's membership, and consequently the user *might* be able to join if
+			// they ask another server.
+			Err!(Request(UnableToAuthorizeJoin(
+				"You do not belong to any of the recognised rooms or spaces required to join \
+				 this room, but this server is unable to verify every requirement. You may be \
+				 able to join via another server."
+			)))
+		}
+	}
+}
+
+/// Validates that an event returned from a remote server by `/make_*`
+/// actually is a membership event with the expected fields.
+///
+/// Without checking this, the remote server could use the remote membership
+/// mechanism to trick our server into signing arbitrary malicious events.
+pub fn validate_remote_member_event_stub(
+	membership: &MembershipState,
+	user_id: &UserId,
+	room_id: &RoomId,
+	event_stub: &CanonicalJsonObject,
+) -> Result<()> {
+	let Some(event_type) = event_stub.get("type") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing type field"
+		));
+	};
+	if event_type != &RoomMemberEventContent::TYPE {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with invalid event type"
+		));
+	}
+
+	let Some(sender) = event_stub.get("sender") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing sender field"
+		));
+	};
+	if sender != &user_id.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect sender"
+		));
+	}
+
+	let Some(state_key) = event_stub.get("state_key") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing state_key field"
+		));
+	};
+	if state_key != &user_id.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect state_key"
+		));
+	}
+
+	let Some(event_room_id) = event_stub.get("room_id") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing room_id field"
+		));
+	};
+	if event_room_id != &room_id.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect room_id"
+		));
+	}
+
+	let Some(content) = event_stub
+		.get("content")
+		.and_then(|content| content.as_object())
+	else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing content field"
+		));
+	};
+	let Some(event_membership) = content.get("membership") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing membership field"
+		));
+	};
+	if event_membership != &membership.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect membership type"
+		));
+	}
+
+	Ok(())
+}

src/service/rooms/mod.rs

@@ -3,6 +3,7 @@
 pub mod directory;
 pub mod event_handler;
 pub mod lazy_loading;
+pub mod membership;
 pub mod metadata;
 pub mod outlier;
 pub mod pdu_metadata;
@@ -27,6 +28,7 @@ pub struct Service {
 	pub directory: Arc<directory::Service>,
 	pub event_handler: Arc<event_handler::Service>,
 	pub lazy_loading: Arc<lazy_loading::Service>,
+	pub membership: Arc<membership::Service>,
 	pub metadata: Arc<metadata::Service>,
 	pub outlier: Arc<outlier::Service>,
 	pub pdu_metadata: Arc<pdu_metadata::Service>,

src/service/services.rs

@@ -95,6 +95,7 @@ macro_rules! build {
 				directory: build!(rooms::directory::Service),
 				event_handler: build!(rooms::event_handler::Service),
 				lazy_loading: build!(rooms::lazy_loading::Service),
+				membership: build!(rooms::membership::Service),
 				metadata: build!(rooms::metadata::Service),
 				outlier: build!(rooms::outlier::Service),
 				pdu_metadata: build!(rooms::pdu_metadata::Service),

src/service/users/mod.rs

@@ -255,10 +255,12 @@ pub async fn lock_account(&self, user_id: &UserId, locking_user: &UserId) {
 
 	pub async fn unlock_account(&self, user_id: &UserId) { self.db.userid_lock.remove(user_id); }
 
-	/// Check if a user has an account on this homeserver.
+	/// Check if the provided user ID belongs to an existing (possibly
+	/// deactivated) account on this homeserver.
 	#[inline]
 	pub async fn exists(&self, user_id: &UserId) -> bool {
-		self.db.userid_password.get(user_id).await.is_ok()
+		self.services.globals.user_is_local(user_id)
+			&& self.db.userid_password.get(user_id).await.is_ok()
 	}
 
 	/// Check if account is deactivated