Cleanup/improve other async queries in some client handlers.

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

src/admin/debug/commands.rs

@@ -412,7 +412,9 @@ pub(super) async fn change_log_level(&self, filter: Option<String>, reset: bool)
 			.reload
 			.reload(&new_filter_layer, Some(handles))
 		{
-			| Ok(()) => return self.write_str("Successfully changed log level").await,
+			| Ok(()) => {
+				return self.write_str("Successfully changed log level").await;
+			},
 			| Err(e) => {
 				return Err!("Failed to modify and reload the global tracing log level: {e}");
 			},

src/admin/processor.rs

@@ -94,8 +94,7 @@ async fn process_command(services: Arc<Services>, input: &CommandInput) -> Proce
 
 #[allow(clippy::result_large_err)]
 fn handle_panic(error: &Error, command: &CommandInput) -> ProcessorResult {
-	let link =
-		"Please submit a [bug report](https://forgejo.ellis.link/continuwuation/continuwuity/issues/new). 🥺";
+	let link = "Please submit a [bug report](https://forgejo.ellis.link/continuwuation/continuwuity/issues/new). 🥺";
 	let msg = format!("Panic occurred while processing command:\n```\n{error:#?}\n```\n{link}");
 	let content = RoomMessageEventContent::notice_markdown(msg);
 	error!("Panic while processing command: {error:?}");

src/admin/user/commands.rs

@@ -286,8 +286,9 @@ pub(super) async fn reset_password(&self, username: String, password: Option<Str
 		.set_password(&user_id, Some(new_password.as_str()))
 	{
 		| Err(e) => return Err!("Couldn't reset the password for user {user_id}: {e}"),
-		| Ok(()) =>
-			write!(self, "Successfully reset the password for user {user_id}: `{new_password}`"),
+		| Ok(()) => {
+			write!(self, "Successfully reset the password for user {user_id}: `{new_password}`")
+		},
 	}
 	.await
 }

src/api/client/membership/ban.rs

@@ -0,0 +1,60 @@
+use axum::extract::State;
+use conduwuit::{Err, Result, matrix::pdu::PduBuilder};
+use ruma::{
+	api::client::membership::ban_user,
+	events::room::member::{MembershipState, RoomMemberEventContent},
+};
+
+use crate::Ruma;
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/ban`
+///
+/// Tries to send a ban event into the room.
+pub(crate) async fn ban_user_route(
+	State(services): State<crate::State>,
+	body: Ruma<ban_user::v3::Request>,
+) -> Result<ban_user::v3::Response> {
+	let sender_user = body.sender_user();
+
+	if sender_user == body.user_id {
+		return Err!(Request(Forbidden("You cannot ban yourself.")));
+	}
+
+	if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+
+	let state_lock = services.rooms.state.mutex.lock(&body.room_id).await;
+
+	let current_member_content = services
+		.rooms
+		.state_accessor
+		.get_member(&body.room_id, &body.user_id)
+		.await
+		.unwrap_or_else(|_| RoomMemberEventContent::new(MembershipState::Ban));
+
+	services
+		.rooms
+		.timeline
+		.build_and_append_pdu(
+			PduBuilder::state(body.user_id.to_string(), &RoomMemberEventContent {
+				membership: MembershipState::Ban,
+				reason: body.reason.clone(),
+				displayname: None, // display name may be offensive
+				avatar_url: None,  // avatar may be offensive
+				is_direct: None,
+				join_authorized_via_users_server: None,
+				third_party_invite: None,
+				redact_events: body.redact_events,
+				..current_member_content
+			}),
+			sender_user,
+			&body.room_id,
+			&state_lock,
+		)
+		.await?;
+
+	drop(state_lock);
+
+	Ok(ban_user::v3::Response::new())
+}

src/api/client/membership/forget.rs

@@ -0,0 +1,52 @@
+use axum::extract::State;
+use conduwuit::{Err, Result, is_matching, result::NotFound, utils::FutureBoolExt};
+use futures::pin_mut;
+use ruma::{api::client::membership::forget_room, events::room::member::MembershipState};
+
+use crate::Ruma;
+
+/// # `POST /_matrix/client/v3/rooms/{roomId}/forget`
+///
+/// Forgets about a room.
+///
+/// - If the sender user currently left the room: Stops sender user from
+///   receiving information about the room
+///
+/// Note: Other devices of the user have no way of knowing the room was
+/// forgotten, so this has to be called from every device
+pub(crate) async fn forget_room_route(
+	State(services): State<crate::State>,
+	body: Ruma<forget_room::v3::Request>,
+) -> Result<forget_room::v3::Response> {
+	let user_id = body.sender_user();
+	let room_id = &body.room_id;
+
+	let joined = services.rooms.state_cache.is_joined(user_id, room_id);
+	let knocked = services.rooms.state_cache.is_knocked(user_id, room_id);
+	let invited = services.rooms.state_cache.is_invited(user_id, room_id);
+
+	pin_mut!(joined, knocked, invited);
+	if joined.or(knocked).or(invited).await {
+		return Err!(Request(Unknown("You must leave the room before forgetting it")));
+	}
+
+	let membership = services
+		.rooms
+		.state_accessor
+		.get_member(room_id, user_id)
+		.await;
+
+	if membership.is_not_found() {
+		return Err!(Request(Unknown("No membership event was found, room was never joined")));
+	}
+
+	let non_membership = membership
+		.map(|member| member.membership)
+		.is_ok_and(is_matching!(MembershipState::Leave | MembershipState::Ban));
+
+	if non_membership || services.rooms.state_cache.is_left(user_id, room_id).await {
+		services.rooms.state_cache.forget(room_id, user_id);
+	}
+
+	Ok(forget_room::v3::Response::new())
+}

src/api/client/membership/invite.rs

@@ -0,0 +1,238 @@
+use axum::extract::State;
+use axum_client_ip::InsecureClientIp;
+use conduwuit::{
+	Err, Result, debug_error, err, info,
+	matrix::pdu::{PduBuilder, gen_event_id_canonical_json},
+};
+use futures::{FutureExt, join};
+use ruma::{
+	OwnedServerName, RoomId, UserId,
+	api::{client::membership::invite_user, federation::membership::create_invite},
+	events::room::member::{MembershipState, RoomMemberEventContent},
+};
+use service::Services;
+
+use super::banned_room_check;
+use crate::Ruma;
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/invite`
+///
+/// Tries to send an invite event into the room.
+#[tracing::instrument(skip_all, fields(%client), name = "invite")]
+pub(crate) async fn invite_user_route(
+	State(services): State<crate::State>,
+	InsecureClientIp(client): InsecureClientIp,
+	body: Ruma<invite_user::v3::Request>,
+) -> Result<invite_user::v3::Response> {
+	let sender_user = body.sender_user();
+	if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+
+	if !services.users.is_admin(sender_user).await && services.config.block_non_admin_invites {
+		debug_error!(
+			"User {sender_user} is not an admin and attempted to send an invite to room {}",
+			&body.room_id
+		);
+		return Err!(Request(Forbidden("Invites are not allowed on this server.")));
+	}
+
+	banned_room_check(
+		&services,
+		sender_user,
+		Some(&body.room_id),
+		body.room_id.server_name(),
+		client,
+	)
+	.await?;
+
+	match &body.recipient {
+		| invite_user::v3::InvitationRecipient::UserId { user_id } => {
+			let sender_ignored_recipient = services.users.user_is_ignored(sender_user, user_id);
+			let recipient_ignored_by_sender =
+				services.users.user_is_ignored(user_id, sender_user);
+
+			let (sender_ignored_recipient, recipient_ignored_by_sender) =
+				join!(sender_ignored_recipient, recipient_ignored_by_sender);
+
+			if sender_ignored_recipient {
+				return Ok(invite_user::v3::Response {});
+			}
+
+			if let Ok(target_user_membership) = services
+				.rooms
+				.state_accessor
+				.get_member(&body.room_id, user_id)
+				.await
+			{
+				if target_user_membership.membership == MembershipState::Ban {
+					return Err!(Request(Forbidden("User is banned from this room.")));
+				}
+			}
+
+			if recipient_ignored_by_sender {
+				// silently drop the invite to the recipient if they've been ignored by the
+				// sender, pretend it worked
+				return Ok(invite_user::v3::Response {});
+			}
+
+			invite_helper(
+				&services,
+				sender_user,
+				user_id,
+				&body.room_id,
+				body.reason.clone(),
+				false,
+			)
+			.boxed()
+			.await?;
+
+			Ok(invite_user::v3::Response {})
+		},
+		| _ => {
+			Err!(Request(NotFound("User not found.")))
+		},
+	}
+}
+
+pub(crate) async fn invite_helper(
+	services: &Services,
+	sender_user: &UserId,
+	user_id: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+	is_direct: bool,
+) -> Result {
+	if !services.users.is_admin(sender_user).await && services.config.block_non_admin_invites {
+		info!(
+			"User {sender_user} is not an admin and attempted to send an invite to room \
+			 {room_id}"
+		);
+		return Err!(Request(Forbidden("Invites are not allowed on this server.")));
+	}
+
+	if !services.globals.user_is_local(user_id) {
+		let (pdu, pdu_json, invite_room_state) = {
+			let state_lock = services.rooms.state.mutex.lock(room_id).await;
+
+			let content = RoomMemberEventContent {
+				avatar_url: services.users.avatar_url(user_id).await.ok(),
+				is_direct: Some(is_direct),
+				reason,
+				..RoomMemberEventContent::new(MembershipState::Invite)
+			};
+
+			let (pdu, pdu_json) = services
+				.rooms
+				.timeline
+				.create_hash_and_sign_event(
+					PduBuilder::state(user_id.to_string(), &content),
+					sender_user,
+					room_id,
+					&state_lock,
+				)
+				.await?;
+
+			let invite_room_state = services.rooms.state.summary_stripped(&pdu).await;
+
+			drop(state_lock);
+
+			(pdu, pdu_json, invite_room_state)
+		};
+
+		let room_version_id = services.rooms.state.get_room_version(room_id).await?;
+
+		let response = services
+			.sending
+			.send_federation_request(user_id.server_name(), create_invite::v2::Request {
+				room_id: room_id.to_owned(),
+				event_id: (*pdu.event_id).to_owned(),
+				room_version: room_version_id.clone(),
+				event: services
+					.sending
+					.convert_to_outgoing_federation_event(pdu_json.clone())
+					.await,
+				invite_room_state,
+				via: services
+					.rooms
+					.state_cache
+					.servers_route_via(room_id)
+					.await
+					.ok(),
+			})
+			.await?;
+
+		// We do not add the event_id field to the pdu here because of signature and
+		// hashes checks
+		let (event_id, value) = gen_event_id_canonical_json(&response.event, &room_version_id)
+			.map_err(|e| {
+				err!(Request(BadJson(warn!("Could not convert event to canonical JSON: {e}"))))
+			})?;
+
+		if pdu.event_id != event_id {
+			return Err!(Request(BadJson(warn!(
+				%pdu.event_id, %event_id,
+				"Server {} sent event with wrong event ID",
+				user_id.server_name()
+			))));
+		}
+
+		let origin: OwnedServerName = serde_json::from_value(serde_json::to_value(
+			value
+				.get("origin")
+				.ok_or_else(|| err!(Request(BadJson("Event missing origin field."))))?,
+		)?)
+		.map_err(|e| {
+			err!(Request(BadJson(warn!("Origin field in event is not a valid server name: {e}"))))
+		})?;
+
+		let pdu_id = services
+			.rooms
+			.event_handler
+			.handle_incoming_pdu(&origin, room_id, &event_id, value, true)
+			.boxed()
+			.await?
+			.ok_or_else(|| {
+				err!(Request(InvalidParam("Could not accept incoming PDU as timeline event.")))
+			})?;
+
+		return services.sending.send_pdu_room(room_id, &pdu_id).await;
+	}
+
+	if !services
+		.rooms
+		.state_cache
+		.is_joined(sender_user, room_id)
+		.await
+	{
+		return Err!(Request(Forbidden(
+			"You must be joined in the room you are trying to invite from."
+		)));
+	}
+
+	let state_lock = services.rooms.state.mutex.lock(room_id).await;
+
+	let content = RoomMemberEventContent {
+		displayname: services.users.displayname(user_id).await.ok(),
+		avatar_url: services.users.avatar_url(user_id).await.ok(),
+		blurhash: services.users.blurhash(user_id).await.ok(),
+		is_direct: Some(is_direct),
+		reason,
+		..RoomMemberEventContent::new(MembershipState::Invite)
+	};
+
+	services
+		.rooms
+		.timeline
+		.build_and_append_pdu(
+			PduBuilder::state(user_id.to_string(), &content),
+			sender_user,
+			room_id,
+			&state_lock,
+		)
+		.await?;
+
+	drop(state_lock);
+
+	Ok(())
+}

src/api/client/membership/join.rs

@@ -0,0 +1,988 @@
+use std::{borrow::Borrow, collections::HashMap, iter::once, sync::Arc};
+
+use axum::extract::State;
+use axum_client_ip::InsecureClientIp;
+use conduwuit::{
+	Err, Result, debug, debug_info, debug_warn, err, error, info,
+	matrix::{
+		StateKey,
+		pdu::{PduBuilder, PduEvent, gen_event_id, gen_event_id_canonical_json},
+		state_res,
+	},
+	result::FlatOk,
+	trace,
+	utils::{
+		self, shuffle,
+		stream::{IterStream, ReadyExt},
+	},
+	warn,
+};
+use futures::{FutureExt, StreamExt};
+use ruma::{
+	CanonicalJsonObject, CanonicalJsonValue, OwnedRoomId, OwnedServerName, OwnedUserId, RoomId,
+	RoomVersionId, UserId,
+	api::{
+		client::{
+			error::ErrorKind,
+			membership::{ThirdPartySigned, join_room_by_id, join_room_by_id_or_alias},
+		},
+		federation::{self},
+	},
+	canonical_json::to_canonical_value,
+	events::{
+		StateEventType,
+		room::{
+			join_rules::{AllowRule, JoinRule, RoomJoinRulesEventContent},
+			member::{MembershipState, RoomMemberEventContent},
+		},
+	},
+};
+use service::{
+	Services,
+	appservice::RegistrationInfo,
+	rooms::{
+		state::RoomMutexGuard,
+		state_compressor::{CompressedState, HashSetCompressStateEvent},
+	},
+};
+
+use super::banned_room_check;
+use crate::Ruma;
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/join`
+///
+/// Tries to join the sender user into a room.
+///
+/// - If the server knowns about this room: creates the join event and does auth
+///   rules locally
+/// - If the server does not know about the room: asks other servers over
+///   federation
+#[tracing::instrument(skip_all, fields(%client), name = "join")]
+pub(crate) async fn join_room_by_id_route(
+	State(services): State<crate::State>,
+	InsecureClientIp(client): InsecureClientIp,
+	body: Ruma<join_room_by_id::v3::Request>,
+) -> Result<join_room_by_id::v3::Response> {
+	let sender_user = body.sender_user();
+	if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+
+	banned_room_check(
+		&services,
+		sender_user,
+		Some(&body.room_id),
+		body.room_id.server_name(),
+		client,
+	)
+	.await?;
+
+	// There is no body.server_name for /roomId/join
+	let mut servers: Vec<_> = services
+		.rooms
+		.state_cache
+		.servers_invite_via(&body.room_id)
+		.map(ToOwned::to_owned)
+		.collect()
+		.await;
+
+	servers.extend(
+		services
+			.rooms
+			.state_cache
+			.invite_state(sender_user, &body.room_id)
+			.await
+			.unwrap_or_default()
+			.iter()
+			.filter_map(|event| event.get_field("sender").ok().flatten())
+			.filter_map(|sender: &str| UserId::parse(sender).ok())
+			.map(|user| user.server_name().to_owned()),
+	);
+
+	if let Some(server) = body.room_id.server_name() {
+		servers.push(server.into());
+	}
+
+	servers.sort_unstable();
+	servers.dedup();
+	shuffle(&mut servers);
+
+	join_room_by_id_helper(
+		&services,
+		sender_user,
+		&body.room_id,
+		body.reason.clone(),
+		&servers,
+		body.third_party_signed.as_ref(),
+		&body.appservice_info,
+	)
+	.boxed()
+	.await
+}
+
+/// # `POST /_matrix/client/r0/join/{roomIdOrAlias}`
+///
+/// Tries to join the sender user into a room.
+///
+/// - If the server knowns about this room: creates the join event and does auth
+///   rules locally
+/// - If the server does not know about the room: use the server name query
+///   param if specified. if not specified, asks other servers over federation
+///   via room alias server name and room ID server name
+#[tracing::instrument(skip_all, fields(%client), name = "join")]
+pub(crate) async fn join_room_by_id_or_alias_route(
+	State(services): State<crate::State>,
+	InsecureClientIp(client): InsecureClientIp,
+	body: Ruma<join_room_by_id_or_alias::v3::Request>,
+) -> Result<join_room_by_id_or_alias::v3::Response> {
+	let sender_user = body.sender_user();
+	let appservice_info = &body.appservice_info;
+	let body = &body.body;
+		if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+
+	let (servers, room_id) = match OwnedRoomId::try_from(body.room_id_or_alias.clone()) {
+		| Ok(room_id) => {
+			banned_room_check(
+				&services,
+				sender_user,
+				Some(&room_id),
+				room_id.server_name(),
+				client,
+			)
+			.boxed()
+			.await?;
+
+			let mut servers = body.via.clone();
+			servers.extend(
+				services
+					.rooms
+					.state_cache
+					.servers_invite_via(&room_id)
+					.map(ToOwned::to_owned)
+					.collect::<Vec<_>>()
+					.await,
+			);
+
+			servers.extend(
+				services
+					.rooms
+					.state_cache
+					.invite_state(sender_user, &room_id)
+					.await
+					.unwrap_or_default()
+					.iter()
+					.filter_map(|event| event.get_field("sender").ok().flatten())
+					.filter_map(|sender: &str| UserId::parse(sender).ok())
+					.map(|user| user.server_name().to_owned()),
+			);
+
+			if let Some(server) = room_id.server_name() {
+				servers.push(server.to_owned());
+			}
+
+			servers.sort_unstable();
+			servers.dedup();
+			shuffle(&mut servers);
+
+			(servers, room_id)
+		},
+		| Err(room_alias) => {
+			let (room_id, mut servers) = services
+				.rooms
+				.alias
+				.resolve_alias(&room_alias, Some(body.via.clone()))
+				.await?;
+
+			banned_room_check(
+				&services,
+				sender_user,
+				Some(&room_id),
+				Some(room_alias.server_name()),
+				client,
+			)
+			.await?;
+
+			let addl_via_servers = services
+				.rooms
+				.state_cache
+				.servers_invite_via(&room_id)
+				.map(ToOwned::to_owned);
+
+			let addl_state_servers = services
+				.rooms
+				.state_cache
+				.invite_state(sender_user, &room_id)
+				.await
+				.unwrap_or_default();
+
+			let mut addl_servers: Vec<_> = addl_state_servers
+				.iter()
+				.map(|event| event.get_field("sender"))
+				.filter_map(FlatOk::flat_ok)
+				.map(|user: &UserId| user.server_name().to_owned())
+				.stream()
+				.chain(addl_via_servers)
+				.collect()
+				.await;
+
+			addl_servers.sort_unstable();
+			addl_servers.dedup();
+			shuffle(&mut addl_servers);
+			servers.append(&mut addl_servers);
+
+			(servers, room_id)
+		},
+	};
+
+	let join_room_response = join_room_by_id_helper(
+		&services,
+		sender_user,
+		&room_id,
+		body.reason.clone(),
+		&servers,
+		body.third_party_signed.as_ref(),
+		appservice_info,
+	)
+	.boxed()
+	.await?;
+
+	Ok(join_room_by_id_or_alias::v3::Response { room_id: 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],
+	third_party_signed: Option<&ThirdPartySigned>,
+	appservice_info: &Option<RegistrationInfo>,
+) -> Result<join_room_by_id::v3::Response> {
+	let state_lock = services.rooms.state.mutex.lock(room_id).await;
+
+	let user_is_guest = services
+		.users
+		.is_deactivated(sender_user)
+		.await
+		.unwrap_or(false)
+		&& appservice_info.is_none();
+
+	if user_is_guest && !services.rooms.state_accessor.guest_can_join(room_id).await {
+		return Err!(Request(Forbidden("Guests are not allowed to join this room")));
+	}
+
+	if 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 { room_id: room_id.into() });
+	}
+
+	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.")));
+		}
+	}
+
+	let local_join = server_in_room
+		|| servers.is_empty()
+		|| (servers.len() == 1 && services.globals.server_is_ours(&servers[0]));
+
+	if local_join {
+		join_room_by_id_helper_local(
+			services,
+			sender_user,
+			room_id,
+			reason,
+			servers,
+			third_party_signed,
+			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,
+			third_party_signed,
+			state_lock,
+		)
+		.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")]
+async fn join_room_by_id_helper_remote(
+	services: &Services,
+	sender_user: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+	servers: &[OwnedServerName],
+	_third_party_signed: Option<&ThirdPartySigned>,
+	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 Some(room_version_id) = make_join_response.room_version else {
+		return Err!(BadServerResponse("Remote room version is not supported by conduwuit"));
+	};
+
+	if !services.server.supported_room_version(&room_version_id) {
+		return Err!(BadServerResponse(
+			"Remote room version {room_version_id} is not supported by conduwuit"
+		));
+	}
+
+	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_id, 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".to_owned(),
+		CanonicalJsonValue::String(services.globals.server_name().as_str().to_owned()),
+	);
+	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"),
+		),
+	);
+	join_event_stub.insert(
+		"content".to_owned(),
+		to_canonical_value(RoomMemberEventContent {
+			displayname: services.users.displayname(sender_user).await.ok(),
+			avatar_url: services.users.avatar_url(sender_user).await.ok(),
+			blurhash: services.users.blurhash(sender_user).await.ok(),
+			reason,
+			join_authorized_via_users_server: join_authorized_via_users_server.clone(),
+			..RoomMemberEventContent::new(MembershipState::Join)
+		})
+		.expect("event is valid, we just created it"),
+	);
+
+	// We keep the "event_id" in the pdu only in v1 or
+	// v2 rooms
+	match room_version_id {
+		| RoomVersionId::V1 | RoomVersionId::V2 => {},
+		| _ => {
+			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_id)?;
+
+	// Generate event id
+	let event_id = gen_event_id(&join_event_stub, &room_version_id)?;
+
+	// 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 {
+		room_id: room_id.to_owned(),
+		event_id: event_id.clone(),
+		omit_members: false,
+		pdu: 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_id).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_id)
+		})
+		.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;
+				},
+			};
+
+			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_id)
+		})
+		.ready_filter_map(Result::ok)
+		.ready_for_each(|(event_id, value)| {
+			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(
+		&state_res::RoomVersion::new(&room_version_id)?,
+		&parsed_join_pdu,
+		None, // TODO: third party invite
+		|k, s| state_fetch(k.clone(), s.into()),
+	)
+	.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?;
+
+	info!("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)
+		.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,
+		)
+		.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")]
+async fn join_room_by_id_helper_local(
+	services: &Services,
+	sender_user: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+	servers: &[OwnedServerName],
+	_third_party_signed: Option<&ThirdPartySigned>,
+	state_lock: RoomMutexGuard,
+) -> Result {
+	debug_info!("We can join locally");
+
+	let join_rules_event_content = services
+		.rooms
+		.state_accessor
+		.room_state_get_content::<RoomJoinRulesEventContent>(
+			room_id,
+			&StateEventType::RoomJoinRules,
+			"",
+		)
+		.await;
+
+	let restriction_rooms = match join_rules_event_content {
+		| Ok(RoomJoinRulesEventContent {
+			join_rule: JoinRule::Restricted(restricted) | JoinRule::KnockRestricted(restricted),
+		}) => restricted
+			.allow
+			.into_iter()
+			.filter_map(|a| match a {
+				| AllowRule::RoomMembership(r) => Some(r.room_id),
+				| _ => None,
+			})
+			.collect(),
+		| _ => Vec::new(),
+	};
+
+	let join_authorized_via_users_server: Option<OwnedUserId> = {
+		if restriction_rooms
+			.iter()
+			.stream()
+			.any(|restriction_room_id| {
+				services
+					.rooms
+					.state_cache
+					.is_joined(sender_user, restriction_room_id)
+			})
+			.await
+		{
+			services
+				.rooms
+				.state_cache
+				.local_users_in_room(room_id)
+				.filter(|user| {
+					services.rooms.state_accessor.user_can_invite(
+						room_id,
+						user,
+						sender_user,
+						&state_lock,
+					)
+				})
+				.boxed()
+				.next()
+				.await
+				.map(ToOwned::to_owned)
+		} else {
+			None
+		}
+	};
+
+	let content = RoomMemberEventContent {
+		displayname: services.users.displayname(sender_user).await.ok(),
+		avatar_url: services.users.avatar_url(sender_user).await.ok(),
+		blurhash: services.users.blurhash(sender_user).await.ok(),
+		reason: reason.clone(),
+		join_authorized_via_users_server,
+		..RoomMemberEventContent::new(MembershipState::Join)
+	};
+
+	// Try normal join first
+	let Err(error) = services
+		.rooms
+		.timeline
+		.build_and_append_pdu(
+			PduBuilder::state(sender_user.to_string(), &content),
+			sender_user,
+			room_id,
+			&state_lock,
+		)
+		.await
+	else {
+		return Ok(());
+	};
+
+	if restriction_rooms.is_empty()
+		&& (servers.is_empty()
+			|| servers.len() == 1 && services.globals.server_is_ours(&servers[0]))
+	{
+		return Err(error);
+	}
+
+	warn!(
+		"We couldn't do the join locally, maybe federation can help to satisfy the restricted \
+		 join requirements"
+	);
+	let Ok((make_join_response, remote_server)) =
+		make_join_request(services, sender_user, room_id, servers).await
+	else {
+		return Err(error);
+	};
+
+	let Some(room_version_id) = make_join_response.room_version else {
+		return Err!(BadServerResponse("Remote room version is not supported by conduwuit"));
+	};
+
+	if !services.server.supported_room_version(&room_version_id) {
+		return Err!(BadServerResponse(
+			"Remote room version {room_version_id} is not supported by conduwuit"
+		));
+	}
+
+	let mut join_event_stub: CanonicalJsonObject =
+		serde_json::from_str(make_join_response.event.get()).map_err(|e| {
+			err!(BadServerResponse("Invalid make_join event json received from server: {e:?}"))
+		})?;
+
+	let join_authorized_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());
+
+	join_event_stub.insert(
+		"origin".to_owned(),
+		CanonicalJsonValue::String(services.globals.server_name().as_str().to_owned()),
+	);
+	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"),
+		),
+	);
+	join_event_stub.insert(
+		"content".to_owned(),
+		to_canonical_value(RoomMemberEventContent {
+			displayname: services.users.displayname(sender_user).await.ok(),
+			avatar_url: services.users.avatar_url(sender_user).await.ok(),
+			blurhash: services.users.blurhash(sender_user).await.ok(),
+			reason,
+			join_authorized_via_users_server,
+			..RoomMemberEventContent::new(MembershipState::Join)
+		})
+		.expect("event is valid, we just created it"),
+	);
+
+	// We keep the "event_id" in the pdu only in v1 or
+	// v2 rooms
+	match room_version_id {
+		| RoomVersionId::V1 | RoomVersionId::V2 => {},
+		| _ => {
+			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_id)?;
+
+	// Generate event id
+	let event_id = gen_event_id(&join_event_stub, &room_version_id)?;
+
+	// 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 join_event = join_event_stub;
+
+	let send_join_response = services
+		.sending
+		.send_synapse_request(
+			&remote_server,
+			federation::membership::create_join_event::v2::Request {
+				room_id: room_id.to_owned(),
+				event_id: event_id.clone(),
+				omit_members: false,
+				pdu: services
+					.sending
+					.convert_to_outgoing_federation_event(join_event.clone())
+					.await,
+			},
+		)
+		.await?;
+
+	if let Some(signed_raw) = send_join_response.room_state.event {
+		let (signed_event_id, signed_value) =
+			gen_event_id_canonical_json(&signed_raw, &room_version_id).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")
+			)));
+		}
+
+		drop(state_lock);
+		services
+			.rooms
+			.event_handler
+			.handle_incoming_pdu(&remote_server, room_id, &signed_event_id, signed_value, true)
+			.boxed()
+			.await?;
+	} else {
+		return Err(error);
+	}
+
+	Ok(())
+}
+
+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_response_and_server =
+		Err!(BadServerResponse("No server available to assist in joining."));
+
+	let mut make_join_counter: usize = 0;
+	let mut incompatible_room_version_count: usize = 0;
+
+	for remote_server in servers {
+		if services.globals.server_is_ours(remote_server) {
+			continue;
+		}
+		info!("Asking {remote_server} for make_join ({make_join_counter})");
+		let make_join_response = services
+			.sending
+			.send_federation_request(
+				remote_server,
+				federation::membership::prepare_join_event::v1::Request {
+					room_id: room_id.to_owned(),
+					user_id: sender_user.to_owned(),
+					ver: services.server.supported_room_versions().collect(),
+				},
+			)
+			.await;
+
+		trace!("make_join response: {:?}", make_join_response);
+		make_join_counter = make_join_counter.saturating_add(1);
+
+		if let Err(ref e) = make_join_response {
+			if matches!(
+				e.kind(),
+				ErrorKind::IncompatibleRoomVersion { .. } | ErrorKind::UnsupportedRoomVersion
+			) {
+				incompatible_room_version_count =
+					incompatible_room_version_count.saturating_add(1);
+			}
+
+			if incompatible_room_version_count > 15 {
+				info!(
+					"15 servers have responded with M_INCOMPATIBLE_ROOM_VERSION or \
+					 M_UNSUPPORTED_ROOM_VERSION, assuming that conduwuit does not support the \
+					 room version {room_id}: {e}"
+				);
+				make_join_response_and_server =
+					Err!(BadServerResponse("Room version is not supported by Conduwuit"));
+				return make_join_response_and_server;
+			}
+
+			if make_join_counter > 40 {
+				warn!(
+					"40 servers failed to provide valid make_join response, assuming no server \
+					 can assist in joining."
+				);
+				make_join_response_and_server =
+					Err!(BadServerResponse("No server available to assist in joining."));
+
+				return make_join_response_and_server;
+			}
+		}
+
+		make_join_response_and_server = make_join_response.map(|r| (r, remote_server.clone()));
+
+		if make_join_response_and_server.is_ok() {
+			break;
+		}
+	}
+
+	make_join_response_and_server
+}

src/api/client/membership/kick.rs

@@ -0,0 +1,65 @@
+use axum::extract::State;
+use conduwuit::{Err, Result, matrix::pdu::PduBuilder};
+use ruma::{
+	api::client::membership::kick_user,
+	events::room::member::{MembershipState, RoomMemberEventContent},
+};
+
+use crate::Ruma;
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/kick`
+///
+/// Tries to send a kick event into the room.
+pub(crate) async fn kick_user_route(
+	State(services): State<crate::State>,
+	body: Ruma<kick_user::v3::Request>,
+) -> Result<kick_user::v3::Response> {
+	let sender_user = body.sender_user();
+	if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+	let state_lock = services.rooms.state.mutex.lock(&body.room_id).await;
+
+	let Ok(event) = services
+		.rooms
+		.state_accessor
+		.get_member(&body.room_id, &body.user_id)
+		.await
+	else {
+		// copy synapse's behaviour of returning 200 without any change to the state
+		// instead of erroring on left users
+		return Ok(kick_user::v3::Response::new());
+	};
+
+	if !matches!(
+		event.membership,
+		MembershipState::Invite | MembershipState::Knock | MembershipState::Join,
+	) {
+		return Err!(Request(Forbidden(
+			"Cannot kick a user who is not apart of the room (current membership: {})",
+			event.membership
+		)));
+	}
+
+	services
+		.rooms
+		.timeline
+		.build_and_append_pdu(
+			PduBuilder::state(body.user_id.to_string(), &RoomMemberEventContent {
+				membership: MembershipState::Leave,
+				reason: body.reason.clone(),
+				is_direct: None,
+				join_authorized_via_users_server: None,
+				third_party_invite: None,
+				..event
+			}),
+			sender_user,
+			&body.room_id,
+			&state_lock,
+		)
+		.await?;
+
+	drop(state_lock);
+
+	Ok(kick_user::v3::Response::new())
+}

src/api/client/membership/knock.rs

@@ -0,0 +1,767 @@
+use std::{borrow::Borrow, collections::HashMap, iter::once, sync::Arc};
+
+use axum::extract::State;
+use axum_client_ip::InsecureClientIp;
+use conduwuit::{
+	Err, Result, debug, debug_info, debug_warn, err, info,
+	matrix::pdu::{PduBuilder, PduEvent, gen_event_id},
+	result::FlatOk,
+	trace,
+	utils::{self, shuffle, stream::IterStream},
+	warn,
+};
+use futures::{FutureExt, StreamExt};
+use ruma::{
+	CanonicalJsonObject, CanonicalJsonValue, OwnedEventId, OwnedRoomId, OwnedServerName, RoomId,
+	RoomVersionId, UserId,
+	api::{
+		client::knock::knock_room,
+		federation::{self},
+	},
+	canonical_json::to_canonical_value,
+	events::{
+		StateEventType,
+		room::{
+			join_rules::{AllowRule, JoinRule},
+			member::{MembershipState, RoomMemberEventContent},
+		},
+	},
+};
+use service::{
+	Services,
+	rooms::{
+		state::RoomMutexGuard,
+		state_compressor::{CompressedState, HashSetCompressStateEvent},
+	},
+};
+
+use super::{banned_room_check, join::join_room_by_id_helper};
+use crate::Ruma;
+
+/// # `POST /_matrix/client/*/knock/{roomIdOrAlias}`
+///
+/// Tries to knock the room to ask permission to join for the sender user.
+#[tracing::instrument(skip_all, fields(%client), name = "knock")]
+pub(crate) async fn knock_room_route(
+	State(services): State<crate::State>,
+	InsecureClientIp(client): InsecureClientIp,
+	body: Ruma<knock_room::v3::Request>,
+) -> Result<knock_room::v3::Response> {
+	let sender_user = body.sender_user();
+	let body = &body.body;
+	if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+
+	let (servers, room_id) = match OwnedRoomId::try_from(body.room_id_or_alias.clone()) {
+		| Ok(room_id) => {
+			banned_room_check(
+				&services,
+				sender_user,
+				Some(&room_id),
+				room_id.server_name(),
+				client,
+			)
+			.await?;
+
+			let mut servers = body.via.clone();
+			servers.extend(
+				services
+					.rooms
+					.state_cache
+					.servers_invite_via(&room_id)
+					.map(ToOwned::to_owned)
+					.collect::<Vec<_>>()
+					.await,
+			);
+
+			servers.extend(
+				services
+					.rooms
+					.state_cache
+					.invite_state(sender_user, &room_id)
+					.await
+					.unwrap_or_default()
+					.iter()
+					.filter_map(|event| event.get_field("sender").ok().flatten())
+					.filter_map(|sender: &str| UserId::parse(sender).ok())
+					.map(|user| user.server_name().to_owned()),
+			);
+
+			if let Some(server) = room_id.server_name() {
+				servers.push(server.to_owned());
+			}
+
+			servers.sort_unstable();
+			servers.dedup();
+			shuffle(&mut servers);
+
+			(servers, room_id)
+		},
+		| Err(room_alias) => {
+			let (room_id, mut servers) = services
+				.rooms
+				.alias
+				.resolve_alias(&room_alias, Some(body.via.clone()))
+				.await?;
+
+			banned_room_check(
+				&services,
+				sender_user,
+				Some(&room_id),
+				Some(room_alias.server_name()),
+				client,
+			)
+			.await?;
+
+			let addl_via_servers = services
+				.rooms
+				.state_cache
+				.servers_invite_via(&room_id)
+				.map(ToOwned::to_owned);
+
+			let addl_state_servers = services
+				.rooms
+				.state_cache
+				.invite_state(sender_user, &room_id)
+				.await
+				.unwrap_or_default();
+
+			let mut addl_servers: Vec<_> = addl_state_servers
+				.iter()
+				.map(|event| event.get_field("sender"))
+				.filter_map(FlatOk::flat_ok)
+				.map(|user: &UserId| user.server_name().to_owned())
+				.stream()
+				.chain(addl_via_servers)
+				.collect()
+				.await;
+
+			addl_servers.sort_unstable();
+			addl_servers.dedup();
+			shuffle(&mut addl_servers);
+			servers.append(&mut addl_servers);
+
+			(servers, room_id)
+		},
+	};
+
+	knock_room_by_id_helper(&services, sender_user, &room_id, body.reason.clone(), &servers)
+		.boxed()
+		.await
+}
+
+async fn knock_room_by_id_helper(
+	services: &Services,
+	sender_user: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+	servers: &[OwnedServerName],
+) -> Result<knock_room::v3::Response> {
+	let state_lock = services.rooms.state.mutex.lock(room_id).await;
+
+	if services
+		.rooms
+		.state_cache
+		.is_invited(sender_user, room_id)
+		.await
+	{
+		debug_warn!("{sender_user} is already invited in {room_id} but attempted to knock");
+		return Err!(Request(Forbidden(
+			"You cannot knock on a room you are already invited/accepted to."
+		)));
+	}
+
+	if services
+		.rooms
+		.state_cache
+		.is_joined(sender_user, room_id)
+		.await
+	{
+		debug_warn!("{sender_user} is already joined in {room_id} but attempted to knock");
+		return Err!(Request(Forbidden("You cannot knock on a room you are already joined in.")));
+	}
+
+	if services
+		.rooms
+		.state_cache
+		.is_knocked(sender_user, room_id)
+		.await
+	{
+		debug_warn!("{sender_user} is already knocked in {room_id}");
+		return Ok(knock_room::v3::Response { room_id: room_id.into() });
+	}
+
+	if let Ok(membership) = services
+		.rooms
+		.state_accessor
+		.get_member(room_id, sender_user)
+		.await
+	{
+		if membership.membership == MembershipState::Ban {
+			debug_warn!("{sender_user} is banned from {room_id} but attempted to knock");
+			return Err!(Request(Forbidden("You cannot knock on a room you are banned from.")));
+		}
+	}
+
+	// For knock_restricted rooms, check if the user meets the restricted conditions
+	// If they do, attempt to join instead of knock
+	// This is not mentioned in the spec, but should be allowable (we're allowed to
+	// auto-join invites to knocked rooms)
+	let join_rule = services.rooms.state_accessor.get_join_rules(room_id).await;
+
+	if let JoinRule::KnockRestricted(restricted) = &join_rule {
+		let restriction_rooms: Vec<_> = restricted
+			.allow
+			.iter()
+			.filter_map(|a| match a {
+				| AllowRule::RoomMembership(r) => Some(&r.room_id),
+				| _ => None,
+			})
+			.collect();
+
+		// Check if the user is in any of the allowed rooms
+		let mut user_meets_restrictions = false;
+		for restriction_room_id in &restriction_rooms {
+			if services
+				.rooms
+				.state_cache
+				.is_joined(sender_user, restriction_room_id)
+				.await
+			{
+				user_meets_restrictions = true;
+				break;
+			}
+		}
+
+		// If the user meets the restrictions, try joining instead
+		if user_meets_restrictions {
+			debug_info!(
+				"{sender_user} meets the restricted criteria in knock_restricted room \
+				 {room_id}, attempting to join instead of knock"
+			);
+			// For this case, we need to drop the state lock and get a new one in
+			// 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,
+				None,
+				&None,
+			)
+			.await
+			{
+				| Ok(_) => return Ok(knock_room::v3::Response::new(room_id.to_owned())),
+				| Err(e) => {
+					debug_warn!(
+						"Failed to convert knock to join for {sender_user} in {room_id}: {e:?}"
+					);
+					// Get a new state lock for the remaining knock logic
+					let new_state_lock = services.rooms.state.mutex.lock(room_id).await;
+
+					let server_in_room = services
+						.rooms
+						.state_cache
+						.server_in_room(services.globals.server_name(), room_id)
+						.await;
+
+					let local_knock = server_in_room
+						|| servers.is_empty()
+						|| (servers.len() == 1 && services.globals.server_is_ours(&servers[0]));
+
+					if local_knock {
+						knock_room_helper_local(
+							services,
+							sender_user,
+							room_id,
+							reason,
+							servers,
+							new_state_lock,
+						)
+						.boxed()
+						.await?;
+					} else {
+						knock_room_helper_remote(
+							services,
+							sender_user,
+							room_id,
+							reason,
+							servers,
+							new_state_lock,
+						)
+						.boxed()
+						.await?;
+					}
+
+					return Ok(knock_room::v3::Response::new(room_id.to_owned()));
+				},
+			}
+		}
+	} else if !matches!(join_rule, JoinRule::Knock | JoinRule::KnockRestricted(_)) {
+		debug_warn!(
+			"{sender_user} attempted to knock on room {room_id} but its join rule is \
+			 {join_rule:?}, not knock or knock_restricted"
+		);
+	}
+
+	let server_in_room = services
+		.rooms
+		.state_cache
+		.server_in_room(services.globals.server_name(), room_id)
+		.await;
+
+	let local_knock = server_in_room
+		|| servers.is_empty()
+		|| (servers.len() == 1 && services.globals.server_is_ours(&servers[0]));
+
+	if local_knock {
+		knock_room_helper_local(services, sender_user, room_id, reason, servers, state_lock)
+			.boxed()
+			.await?;
+	} else {
+		knock_room_helper_remote(services, sender_user, room_id, reason, servers, state_lock)
+			.boxed()
+			.await?;
+	}
+
+	Ok(knock_room::v3::Response::new(room_id.to_owned()))
+}
+
+async fn knock_room_helper_local(
+	services: &Services,
+	sender_user: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+	servers: &[OwnedServerName],
+	state_lock: RoomMutexGuard,
+) -> Result {
+	debug_info!("We can knock locally");
+
+	let room_version_id = services.rooms.state.get_room_version(room_id).await?;
+
+	if matches!(
+		room_version_id,
+		RoomVersionId::V1
+			| RoomVersionId::V2
+			| RoomVersionId::V3
+			| RoomVersionId::V4
+			| RoomVersionId::V5
+			| RoomVersionId::V6
+	) {
+		return Err!(Request(Forbidden("This room does not support knocking.")));
+	}
+
+	let content = RoomMemberEventContent {
+		displayname: services.users.displayname(sender_user).await.ok(),
+		avatar_url: services.users.avatar_url(sender_user).await.ok(),
+		blurhash: services.users.blurhash(sender_user).await.ok(),
+		reason: reason.clone(),
+		..RoomMemberEventContent::new(MembershipState::Knock)
+	};
+
+	// Try normal knock first
+	let Err(error) = services
+		.rooms
+		.timeline
+		.build_and_append_pdu(
+			PduBuilder::state(sender_user.to_string(), &content),
+			sender_user,
+			room_id,
+			&state_lock,
+		)
+		.await
+	else {
+		return Ok(());
+	};
+
+	if servers.is_empty() || (servers.len() == 1 && services.globals.server_is_ours(&servers[0]))
+	{
+		return Err(error);
+	}
+
+	warn!("We couldn't do the knock locally, maybe federation can help to satisfy the knock");
+
+	let (make_knock_response, remote_server) =
+		make_knock_request(services, sender_user, room_id, servers).await?;
+
+	info!("make_knock finished");
+
+	let room_version_id = make_knock_response.room_version;
+
+	if !services.server.supported_room_version(&room_version_id) {
+		return Err!(BadServerResponse(
+			"Remote room version {room_version_id} is not supported by conduwuit"
+		));
+	}
+
+	let mut knock_event_stub = serde_json::from_str::<CanonicalJsonObject>(
+		make_knock_response.event.get(),
+	)
+	.map_err(|e| {
+		err!(BadServerResponse("Invalid make_knock event json received from server: {e:?}"))
+	})?;
+
+	knock_event_stub.insert(
+		"origin".to_owned(),
+		CanonicalJsonValue::String(services.globals.server_name().as_str().to_owned()),
+	);
+	knock_event_stub.insert(
+		"origin_server_ts".to_owned(),
+		CanonicalJsonValue::Integer(
+			utils::millis_since_unix_epoch()
+				.try_into()
+				.expect("Timestamp is valid js_int value"),
+		),
+	);
+	knock_event_stub.insert(
+		"content".to_owned(),
+		to_canonical_value(RoomMemberEventContent {
+			displayname: services.users.displayname(sender_user).await.ok(),
+			avatar_url: services.users.avatar_url(sender_user).await.ok(),
+			blurhash: services.users.blurhash(sender_user).await.ok(),
+			reason,
+			..RoomMemberEventContent::new(MembershipState::Knock)
+		})
+		.expect("event is valid, we just created it"),
+	);
+
+	// In order to create a compatible ref hash (EventID) the `hashes` field needs
+	// to be present
+	services
+		.server_keys
+		.hash_and_sign_event(&mut knock_event_stub, &room_version_id)?;
+
+	// Generate event id
+	let event_id = gen_event_id(&knock_event_stub, &room_version_id)?;
+
+	// Add event_id
+	knock_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 knock_event = knock_event_stub;
+
+	info!("Asking {remote_server} for send_knock in room {room_id}");
+	let send_knock_request = federation::knock::send_knock::v1::Request {
+		room_id: room_id.to_owned(),
+		event_id: event_id.clone(),
+		pdu: services
+			.sending
+			.convert_to_outgoing_federation_event(knock_event.clone())
+			.await,
+	};
+
+	let send_knock_response = services
+		.sending
+		.send_federation_request(&remote_server, send_knock_request)
+		.await?;
+
+	info!("send_knock finished");
+
+	services
+		.rooms
+		.short
+		.get_or_create_shortroomid(room_id)
+		.await;
+
+	info!("Parsing knock event");
+
+	let parsed_knock_pdu = PduEvent::from_id_val(&event_id, knock_event.clone())
+		.map_err(|e| err!(BadServerResponse("Invalid knock event PDU: {e:?}")))?;
+
+	info!("Updating membership locally to knock state with provided stripped state events");
+	services
+		.rooms
+		.state_cache
+		.update_membership(
+			room_id,
+			sender_user,
+			parsed_knock_pdu
+				.get_content::<RoomMemberEventContent>()
+				.expect("we just created this"),
+			sender_user,
+			Some(send_knock_response.knock_room_state),
+			None,
+			false,
+		)
+		.await?;
+
+	info!("Appending room knock event locally");
+	services
+		.rooms
+		.timeline
+		.append_pdu(
+			&parsed_knock_pdu,
+			knock_event,
+			once(parsed_knock_pdu.event_id.borrow()),
+			&state_lock,
+		)
+		.await?;
+
+	Ok(())
+}
+
+async fn knock_room_helper_remote(
+	services: &Services,
+	sender_user: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+	servers: &[OwnedServerName],
+	state_lock: RoomMutexGuard,
+) -> Result {
+	info!("Knocking {room_id} over federation.");
+
+	let (make_knock_response, remote_server) =
+		make_knock_request(services, sender_user, room_id, servers).await?;
+
+	info!("make_knock finished");
+
+	let room_version_id = make_knock_response.room_version;
+
+	if !services.server.supported_room_version(&room_version_id) {
+		return Err!(BadServerResponse(
+			"Remote room version {room_version_id} is not supported by conduwuit"
+		));
+	}
+
+	let mut knock_event_stub: CanonicalJsonObject =
+		serde_json::from_str(make_knock_response.event.get()).map_err(|e| {
+			err!(BadServerResponse("Invalid make_knock event json received from server: {e:?}"))
+		})?;
+
+	knock_event_stub.insert(
+		"origin".to_owned(),
+		CanonicalJsonValue::String(services.globals.server_name().as_str().to_owned()),
+	);
+	knock_event_stub.insert(
+		"origin_server_ts".to_owned(),
+		CanonicalJsonValue::Integer(
+			utils::millis_since_unix_epoch()
+				.try_into()
+				.expect("Timestamp is valid js_int value"),
+		),
+	);
+	knock_event_stub.insert(
+		"content".to_owned(),
+		to_canonical_value(RoomMemberEventContent {
+			displayname: services.users.displayname(sender_user).await.ok(),
+			avatar_url: services.users.avatar_url(sender_user).await.ok(),
+			blurhash: services.users.blurhash(sender_user).await.ok(),
+			reason,
+			..RoomMemberEventContent::new(MembershipState::Knock)
+		})
+		.expect("event is valid, we just created it"),
+	);
+
+	// In order to create a compatible ref hash (EventID) the `hashes` field needs
+	// to be present
+	services
+		.server_keys
+		.hash_and_sign_event(&mut knock_event_stub, &room_version_id)?;
+
+	// Generate event id
+	let event_id = gen_event_id(&knock_event_stub, &room_version_id)?;
+
+	// Add event_id
+	knock_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 knock_event = knock_event_stub;
+
+	info!("Asking {remote_server} for send_knock in room {room_id}");
+	let send_knock_request = federation::knock::send_knock::v1::Request {
+		room_id: room_id.to_owned(),
+		event_id: event_id.clone(),
+		pdu: services
+			.sending
+			.convert_to_outgoing_federation_event(knock_event.clone())
+			.await,
+	};
+
+	let send_knock_response = services
+		.sending
+		.send_federation_request(&remote_server, send_knock_request)
+		.await?;
+
+	info!("send_knock finished");
+
+	services
+		.rooms
+		.short
+		.get_or_create_shortroomid(room_id)
+		.await;
+
+	info!("Parsing knock event");
+	let parsed_knock_pdu = PduEvent::from_id_val(&event_id, knock_event.clone())
+		.map_err(|e| err!(BadServerResponse("Invalid knock event PDU: {e:?}")))?;
+
+	info!("Going through send_knock response knock state events");
+	let state = send_knock_response
+		.knock_room_state
+		.iter()
+		.map(|event| serde_json::from_str::<CanonicalJsonObject>(event.clone().into_json().get()))
+		.filter_map(Result::ok);
+
+	let mut state_map: HashMap<u64, OwnedEventId> = HashMap::new();
+
+	for event in state {
+		let Some(state_key) = event.get("state_key") else {
+			debug_warn!("send_knock stripped state event missing state_key: {event:?}");
+			continue;
+		};
+		let Some(event_type) = event.get("type") else {
+			debug_warn!("send_knock stripped state event missing event type: {event:?}");
+			continue;
+		};
+
+		let Ok(state_key) = serde_json::from_value::<String>(state_key.clone().into()) else {
+			debug_warn!("send_knock stripped state event has invalid state_key: {event:?}");
+			continue;
+		};
+		let Ok(event_type) = serde_json::from_value::<StateEventType>(event_type.clone().into())
+		else {
+			debug_warn!("send_knock stripped state event has invalid event type: {event:?}");
+			continue;
+		};
+
+		let event_id = gen_event_id(&event, &room_version_id)?;
+		let shortstatekey = services
+			.rooms
+			.short
+			.get_or_create_shortstatekey(&event_type, &state_key)
+			.await;
+
+		services.rooms.outlier.add_pdu_outlier(&event_id, &event);
+		state_map.insert(shortstatekey, event_id.clone());
+	}
+
+	info!("Compressing state from send_knock");
+	let compressed: CompressedState = services
+		.rooms
+		.state_compressor
+		.compress_state_events(state_map.iter().map(|(ssk, eid)| (ssk, eid.borrow())))
+		.collect()
+		.await;
+
+	debug!("Saving compressed state");
+	let HashSetCompressStateEvent {
+		shortstatehash: statehash_before_knock,
+		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_knock, added, removed, &state_lock)
+		.await?;
+
+	let statehash_after_knock = services
+		.rooms
+		.state
+		.append_to_state(&parsed_knock_pdu)
+		.await?;
+
+	info!("Updating membership locally to knock state with provided stripped state events");
+	services
+		.rooms
+		.state_cache
+		.update_membership(
+			room_id,
+			sender_user,
+			parsed_knock_pdu
+				.get_content::<RoomMemberEventContent>()
+				.expect("we just created this"),
+			sender_user,
+			Some(send_knock_response.knock_room_state),
+			None,
+			false,
+		)
+		.await?;
+
+	info!("Appending room knock event locally");
+	services
+		.rooms
+		.timeline
+		.append_pdu(
+			&parsed_knock_pdu,
+			knock_event,
+			once(parsed_knock_pdu.event_id.borrow()),
+			&state_lock,
+		)
+		.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_knock, &state_lock);
+
+	Ok(())
+}
+
+async fn make_knock_request(
+	services: &Services,
+	sender_user: &UserId,
+	room_id: &RoomId,
+	servers: &[OwnedServerName],
+) -> Result<(federation::knock::create_knock_event_template::v1::Response, OwnedServerName)> {
+	let mut make_knock_response_and_server =
+		Err!(BadServerResponse("No server available to assist in knocking."));
+
+	let mut make_knock_counter: usize = 0;
+
+	for remote_server in servers {
+		if services.globals.server_is_ours(remote_server) {
+			continue;
+		}
+
+		info!("Asking {remote_server} for make_knock ({make_knock_counter})");
+
+		let make_knock_response = services
+			.sending
+			.send_federation_request(
+				remote_server,
+				federation::knock::create_knock_event_template::v1::Request {
+					room_id: room_id.to_owned(),
+					user_id: sender_user.to_owned(),
+					ver: services.server.supported_room_versions().collect(),
+				},
+			)
+			.await;
+
+		trace!("make_knock response: {make_knock_response:?}");
+		make_knock_counter = make_knock_counter.saturating_add(1);
+
+		make_knock_response_and_server = make_knock_response.map(|r| (r, remote_server.clone()));
+
+		if make_knock_response_and_server.is_ok() {
+			break;
+		}
+
+		if make_knock_counter > 40 {
+			warn!(
+				"50 servers failed to provide valid make_knock response, assuming no server can \
+				 assist in knocking."
+			);
+			make_knock_response_and_server =
+				Err!(BadServerResponse("No server available to assist in knocking."));
+
+			return make_knock_response_and_server;
+		}
+	}
+
+	make_knock_response_and_server
+}

src/api/client/membership/leave.rs

@@ -0,0 +1,386 @@
+use std::collections::HashSet;
+
+use axum::extract::State;
+use conduwuit::{
+	Err, Result, debug_info, debug_warn, err,
+	matrix::pdu::{PduBuilder, gen_event_id},
+	utils::{self, FutureBoolExt, future::ReadyEqExt},
+	warn,
+};
+use futures::{FutureExt, StreamExt, TryFutureExt, pin_mut};
+use ruma::{
+	CanonicalJsonObject, CanonicalJsonValue, OwnedServerName, RoomId, RoomVersionId, UserId,
+	api::{
+		client::membership::leave_room,
+		federation::{self},
+	},
+	events::{
+		StateEventType,
+		room::member::{MembershipState, RoomMemberEventContent},
+	},
+};
+use service::Services;
+
+use crate::Ruma;
+
+/// # `POST /_matrix/client/v3/rooms/{roomId}/leave`
+///
+/// Tries to leave the sender user from a room.
+///
+/// - This should always work if the user is currently joined.
+pub(crate) async fn leave_room_route(
+	State(services): State<crate::State>,
+	body: Ruma<leave_room::v3::Request>,
+) -> Result<leave_room::v3::Response> {
+	leave_room(&services, body.sender_user(), &body.room_id, body.reason.clone())
+		.boxed()
+		.await
+		.map(|()| leave_room::v3::Response::new())
+}
+
+// Make a user leave all their joined rooms, rescinds knocks, forgets all rooms,
+// and ignores errors
+pub async fn leave_all_rooms(services: &Services, user_id: &UserId) {
+	let rooms_joined = services
+		.rooms
+		.state_cache
+		.rooms_joined(user_id)
+		.map(ToOwned::to_owned);
+
+	let rooms_invited = services
+		.rooms
+		.state_cache
+		.rooms_invited(user_id)
+		.map(|(r, _)| r);
+
+	let rooms_knocked = services
+		.rooms
+		.state_cache
+		.rooms_knocked(user_id)
+		.map(|(r, _)| r);
+
+	let all_rooms: Vec<_> = rooms_joined
+		.chain(rooms_invited)
+		.chain(rooms_knocked)
+		.collect()
+		.await;
+
+	for room_id in all_rooms {
+		// ignore errors
+		if let Err(e) = leave_room(services, user_id, &room_id, None).boxed().await {
+			warn!(%user_id, "Failed to leave {room_id} remotely: {e}");
+		}
+
+		services.rooms.state_cache.forget(&room_id, user_id);
+	}
+}
+
+pub async fn leave_room(
+	services: &Services,
+	user_id: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+) -> Result {
+	let default_member_content = RoomMemberEventContent {
+		membership: MembershipState::Leave,
+		reason: reason.clone(),
+		join_authorized_via_users_server: None,
+		is_direct: None,
+		avatar_url: None,
+		displayname: None,
+		third_party_invite: None,
+		blurhash: None,
+		redact_events: None,
+	};
+
+	let is_banned = services.rooms.metadata.is_banned(room_id);
+	let is_disabled = services.rooms.metadata.is_disabled(room_id);
+
+	pin_mut!(is_banned, is_disabled);
+	if is_banned.or(is_disabled).await {
+		// the room is banned/disabled, the room must be rejected locally since we
+		// cant/dont want to federate with this server
+		services
+			.rooms
+			.state_cache
+			.update_membership(
+				room_id,
+				user_id,
+				default_member_content,
+				user_id,
+				None,
+				None,
+				true,
+			)
+			.await?;
+
+		return Ok(());
+	}
+
+	let dont_have_room = services
+		.rooms
+		.state_cache
+		.server_in_room(services.globals.server_name(), room_id)
+		.eq(&false);
+
+	let not_knocked = services
+		.rooms
+		.state_cache
+		.is_knocked(user_id, room_id)
+		.eq(&false);
+
+	// Ask a remote server if we don't have this room and are not knocking on it
+	if dont_have_room.and(not_knocked).await {
+		if let Err(e) = remote_leave_room(services, user_id, room_id, reason.clone())
+			.boxed()
+			.await
+		{
+			warn!(%user_id, "Failed to leave room {room_id} remotely: {e}");
+			// Don't tell the client about this error
+		}
+
+		let last_state = services
+			.rooms
+			.state_cache
+			.invite_state(user_id, room_id)
+			.or_else(|_| services.rooms.state_cache.knock_state(user_id, room_id))
+			.or_else(|_| services.rooms.state_cache.left_state(user_id, room_id))
+			.await
+			.ok();
+
+		// We always drop the invite, we can't rely on other servers
+		services
+			.rooms
+			.state_cache
+			.update_membership(
+				room_id,
+				user_id,
+				default_member_content,
+				user_id,
+				last_state,
+				None,
+				true,
+			)
+			.await?;
+	} else {
+		let state_lock = services.rooms.state.mutex.lock(room_id).await;
+
+		let Ok(event) = services
+			.rooms
+			.state_accessor
+			.room_state_get_content::<RoomMemberEventContent>(
+				room_id,
+				&StateEventType::RoomMember,
+				user_id.as_str(),
+			)
+			.await
+		else {
+			debug_warn!(
+				"Trying to leave a room you are not a member of, marking room as left locally."
+			);
+
+			return services
+				.rooms
+				.state_cache
+				.update_membership(
+					room_id,
+					user_id,
+					default_member_content,
+					user_id,
+					None,
+					None,
+					true,
+				)
+				.await;
+		};
+
+		services
+			.rooms
+			.timeline
+			.build_and_append_pdu(
+				PduBuilder::state(user_id.to_string(), &RoomMemberEventContent {
+					membership: MembershipState::Leave,
+					reason,
+					join_authorized_via_users_server: None,
+					is_direct: None,
+					..event
+				}),
+				user_id,
+				room_id,
+				&state_lock,
+			)
+			.await?;
+	}
+
+	Ok(())
+}
+
+async fn remote_leave_room(
+	services: &Services,
+	user_id: &UserId,
+	room_id: &RoomId,
+	reason: Option<String>,
+) -> Result<()> {
+	let mut make_leave_response_and_server =
+		Err!(BadServerResponse("No remote server available to assist in leaving {room_id}."));
+
+	let mut servers: HashSet<OwnedServerName> = services
+		.rooms
+		.state_cache
+		.servers_invite_via(room_id)
+		.map(ToOwned::to_owned)
+		.collect()
+		.await;
+
+	match services
+		.rooms
+		.state_cache
+		.invite_state(user_id, room_id)
+		.await
+	{
+		| Ok(invite_state) => {
+			servers.extend(
+				invite_state
+					.iter()
+					.filter_map(|event| event.get_field("sender").ok().flatten())
+					.filter_map(|sender: &str| UserId::parse(sender).ok())
+					.map(|user| user.server_name().to_owned()),
+			);
+		},
+		| _ => {
+			match services
+				.rooms
+				.state_cache
+				.knock_state(user_id, room_id)
+				.await
+			{
+				| Ok(knock_state) => {
+					servers.extend(
+						knock_state
+							.iter()
+							.filter_map(|event| event.get_field("sender").ok().flatten())
+							.filter_map(|sender: &str| UserId::parse(sender).ok())
+							.filter_map(|sender| {
+								if !services.globals.user_is_local(sender) {
+									Some(sender.server_name().to_owned())
+								} else {
+									None
+								}
+							}),
+					);
+				},
+				| _ => {},
+			}
+		},
+	}
+
+	if let Some(room_id_server_name) = room_id.server_name() {
+		servers.insert(room_id_server_name.to_owned());
+	}
+
+	debug_info!("servers in remote_leave_room: {servers:?}");
+
+	for remote_server in servers {
+		let make_leave_response = services
+			.sending
+			.send_federation_request(
+				&remote_server,
+				federation::membership::prepare_leave_event::v1::Request {
+					room_id: room_id.to_owned(),
+					user_id: user_id.to_owned(),
+				},
+			)
+			.await;
+
+		make_leave_response_and_server = make_leave_response.map(|r| (r, remote_server));
+
+		if make_leave_response_and_server.is_ok() {
+			break;
+		}
+	}
+
+	let (make_leave_response, remote_server) = make_leave_response_and_server?;
+
+	let Some(room_version_id) = make_leave_response.room_version else {
+		return Err!(BadServerResponse(warn!(
+			"No room version was returned by {remote_server} for {room_id}, room version is \
+			 likely not supported by conduwuit"
+		)));
+	};
+
+	if !services.server.supported_room_version(&room_version_id) {
+		return Err!(BadServerResponse(warn!(
+			"Remote room version {room_version_id} for {room_id} is not supported by conduwuit",
+		)));
+	}
+
+	let mut leave_event_stub = serde_json::from_str::<CanonicalJsonObject>(
+		make_leave_response.event.get(),
+	)
+	.map_err(|e| {
+		err!(BadServerResponse(warn!(
+			"Invalid make_leave event json received from {remote_server} for {room_id}: {e:?}"
+		)))
+	})?;
+
+	// TODO: Is origin needed?
+	leave_event_stub.insert(
+		"origin".to_owned(),
+		CanonicalJsonValue::String(services.globals.server_name().as_str().to_owned()),
+	);
+	leave_event_stub.insert(
+		"origin_server_ts".to_owned(),
+		CanonicalJsonValue::Integer(
+			utils::millis_since_unix_epoch()
+				.try_into()
+				.expect("Timestamp is valid js_int value"),
+		),
+	);
+	// Inject the reason key into the event content dict if it exists
+	if let Some(reason) = reason {
+		if let Some(CanonicalJsonValue::Object(content)) = leave_event_stub.get_mut("content") {
+			content.insert("reason".to_owned(), CanonicalJsonValue::String(reason));
+		}
+	}
+
+	// room v3 and above removed the "event_id" field from remote PDU format
+	match room_version_id {
+		| RoomVersionId::V1 | RoomVersionId::V2 => {},
+		| _ => {
+			leave_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 leave_event_stub, &room_version_id)?;
+
+	// Generate event id
+	let event_id = gen_event_id(&leave_event_stub, &room_version_id)?;
+
+	// Add event_id back
+	leave_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 leave_event = leave_event_stub;
+
+	services
+		.sending
+		.send_federation_request(
+			&remote_server,
+			federation::membership::create_leave_event::v2::Request {
+				room_id: room_id.to_owned(),
+				event_id,
+				pdu: services
+					.sending
+					.convert_to_outgoing_federation_event(leave_event.clone())
+					.await,
+			},
+		)
+		.await?;
+
+	Ok(())
+}

src/api/client/membership/members.rs

@@ -0,0 +1,147 @@
+use axum::extract::State;
+use conduwuit::{
+	Err, Event, Result, at,
+	matrix::pdu::PduEvent,
+	utils::{
+		future::TryExtExt,
+		stream::{BroadbandExt, ReadyExt},
+	},
+};
+use futures::{StreamExt, future::join};
+use ruma::{
+	api::client::membership::{
+		get_member_events::{self, v3::MembershipEventFilter},
+		joined_members::{self, v3::RoomMember},
+	},
+	events::{
+		StateEventType,
+		room::member::{MembershipState, RoomMemberEventContent},
+	},
+};
+
+use crate::Ruma;
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/members`
+///
+/// Lists all joined users in a room (TODO: at a specific point in time, with a
+/// specific membership).
+///
+/// - Only works if the user is currently joined
+pub(crate) async fn get_member_events_route(
+	State(services): State<crate::State>,
+	body: Ruma<get_member_events::v3::Request>,
+) -> Result<get_member_events::v3::Response> {
+	let sender_user = body.sender_user();
+	let membership = body.membership.as_ref();
+	let not_membership = body.not_membership.as_ref();
+
+	if !services
+		.rooms
+		.state_accessor
+		.user_can_see_state_events(sender_user, &body.room_id)
+		.await
+	{
+		return Err!(Request(Forbidden("You don't have permission to view this room.")));
+	}
+
+	Ok(get_member_events::v3::Response {
+		chunk: services
+			.rooms
+			.state_accessor
+			.room_state_full(&body.room_id)
+			.ready_filter_map(Result::ok)
+			.ready_filter(|((ty, _), _)| *ty == StateEventType::RoomMember)
+			.map(at!(1))
+			.ready_filter_map(|pdu| membership_filter(pdu, membership, not_membership))
+			.map(Event::into_format)
+			.collect()
+			.await,
+	})
+}
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/joined_members`
+///
+/// Lists all members of a room.
+///
+/// - The sender user must be in the room
+/// - TODO: An appservice just needs a puppet joined
+pub(crate) async fn joined_members_route(
+	State(services): State<crate::State>,
+	body: Ruma<joined_members::v3::Request>,
+) -> Result<joined_members::v3::Response> {
+	if !services
+		.rooms
+		.state_accessor
+		.user_can_see_state_events(body.sender_user(), &body.room_id)
+		.await
+	{
+		return Err!(Request(Forbidden("You don't have permission to view this room.")));
+	}
+
+	Ok(joined_members::v3::Response {
+		joined: services
+			.rooms
+			.state_cache
+			.room_members(&body.room_id)
+			.map(ToOwned::to_owned)
+			.broad_then(|user_id| async move {
+				let (display_name, avatar_url) = join(
+					services.users.displayname(&user_id).ok(),
+					services.users.avatar_url(&user_id).ok(),
+				)
+				.await;
+
+				(user_id, RoomMember { display_name, avatar_url })
+			})
+			.collect()
+			.await,
+	})
+}
+
+fn membership_filter(
+	pdu: PduEvent,
+	for_membership: Option<&MembershipEventFilter>,
+	not_membership: Option<&MembershipEventFilter>,
+) -> Option<PduEvent> {
+	let membership_state_filter = match for_membership {
+		| Some(MembershipEventFilter::Ban) => MembershipState::Ban,
+		| Some(MembershipEventFilter::Invite) => MembershipState::Invite,
+		| Some(MembershipEventFilter::Knock) => MembershipState::Knock,
+		| Some(MembershipEventFilter::Leave) => MembershipState::Leave,
+		| Some(_) | None => MembershipState::Join,
+	};
+
+	let not_membership_state_filter = match not_membership {
+		| Some(MembershipEventFilter::Ban) => MembershipState::Ban,
+		| Some(MembershipEventFilter::Invite) => MembershipState::Invite,
+		| Some(MembershipEventFilter::Join) => MembershipState::Join,
+		| Some(MembershipEventFilter::Knock) => MembershipState::Knock,
+		| Some(_) | None => MembershipState::Leave,
+	};
+
+	let evt_membership = pdu.get_content::<RoomMemberEventContent>().ok()?.membership;
+
+	if for_membership.is_some() && not_membership.is_some() {
+		if membership_state_filter != evt_membership
+			|| not_membership_state_filter == evt_membership
+		{
+			None
+		} else {
+			Some(pdu)
+		}
+	} else if for_membership.is_some() && not_membership.is_none() {
+		if membership_state_filter != evt_membership {
+			None
+		} else {
+			Some(pdu)
+		}
+	} else if not_membership.is_some() && for_membership.is_none() {
+		if not_membership_state_filter == evt_membership {
+			None
+		} else {
+			Some(pdu)
+		}
+	} else {
+		Some(pdu)
+	}
+}

src/api/client/membership/mod.rs

@@ -0,0 +1,156 @@
+mod ban;
+mod forget;
+mod invite;
+mod join;
+mod kick;
+mod knock;
+mod leave;
+mod members;
+mod unban;
+
+use std::net::IpAddr;
+
+use axum::extract::State;
+use conduwuit::{Err, Result, warn};
+use futures::{FutureExt, StreamExt};
+use ruma::{OwnedRoomId, RoomId, ServerName, UserId, api::client::membership::joined_rooms};
+use service::Services;
+
+pub(crate) use self::{
+	ban::ban_user_route,
+	forget::forget_room_route,
+	invite::{invite_helper, invite_user_route},
+	join::{join_room_by_id_or_alias_route, join_room_by_id_route},
+	kick::kick_user_route,
+	knock::knock_room_route,
+	leave::leave_room_route,
+	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},
+};
+use crate::{Ruma, client::full_user_deactivate};
+
+/// # `POST /_matrix/client/r0/joined_rooms`
+///
+/// Lists all rooms the user has joined.
+pub(crate) async fn joined_rooms_route(
+	State(services): State<crate::State>,
+	body: Ruma<joined_rooms::v3::Request>,
+) -> Result<joined_rooms::v3::Response> {
+	Ok(joined_rooms::v3::Response {
+		joined_rooms: services
+			.rooms
+			.state_cache
+			.rooms_joined(body.sender_user())
+			.map(ToOwned::to_owned)
+			.collect()
+			.await,
+	})
+}
+
+/// Checks if the room is banned in any way possible and the sender user is not
+/// an admin.
+///
+/// Performs automatic deactivation if `auto_deactivate_banned_room_attempts` is
+/// enabled
+#[tracing::instrument(skip(services))]
+pub(crate) async fn banned_room_check(
+	services: &Services,
+	user_id: &UserId,
+	room_id: Option<&RoomId>,
+	server_name: Option<&ServerName>,
+	client_ip: IpAddr,
+) -> Result {
+	if services.users.is_admin(user_id).await {
+		return Ok(());
+	}
+
+	if let Some(room_id) = room_id {
+		if services.rooms.metadata.is_banned(room_id).await
+			|| services
+				.moderation
+				.is_remote_server_forbidden(room_id.server_name().expect("legacy room mxid"))
+		{
+			warn!(
+				"User {user_id} who is not an admin attempted to send an invite for or \
+				 attempted to join a banned room or banned room server name: {room_id}"
+			);
+
+			if services.server.config.auto_deactivate_banned_room_attempts {
+				warn!(
+					"Automatically deactivating user {user_id} due to attempted banned room join"
+				);
+
+				if services.server.config.admin_room_notices {
+					services
+						.admin
+						.send_text(&format!(
+							"Automatically deactivating user {user_id} due to attempted banned \
+							 room join from IP {client_ip}"
+						))
+						.await;
+				}
+
+				let all_joined_rooms: Vec<OwnedRoomId> = services
+					.rooms
+					.state_cache
+					.rooms_joined(user_id)
+					.map(Into::into)
+					.collect()
+					.await;
+
+				full_user_deactivate(services, user_id, &all_joined_rooms)
+					.boxed()
+					.await?;
+			}
+
+			return Err!(Request(Forbidden("This room is banned on this homeserver.")));
+		}
+	} else if let Some(server_name) = server_name {
+		if services
+			.config
+			.forbidden_remote_server_names
+			.is_match(server_name.host())
+		{
+			warn!(
+				"User {user_id} who is not an admin tried joining a room which has the server \
+				 name {server_name} that is globally forbidden. Rejecting.",
+			);
+
+			if services.server.config.auto_deactivate_banned_room_attempts {
+				warn!(
+					"Automatically deactivating user {user_id} due to attempted banned room join"
+				);
+
+				if services.server.config.admin_room_notices {
+					services
+						.admin
+						.send_text(&format!(
+							"Automatically deactivating user {user_id} due to attempted banned \
+							 room join from IP {client_ip}"
+						))
+						.await;
+				}
+
+				let all_joined_rooms: Vec<OwnedRoomId> = services
+					.rooms
+					.state_cache
+					.rooms_joined(user_id)
+					.map(Into::into)
+					.collect()
+					.await;
+
+				full_user_deactivate(services, user_id, &all_joined_rooms)
+					.boxed()
+					.await?;
+			}
+
+			return Err!(Request(Forbidden("This remote server is banned on this homeserver.")));
+		}
+	}
+
+	Ok(())
+}

src/api/client/membership/unban.rs

@@ -0,0 +1,58 @@
+use axum::extract::State;
+use conduwuit::{Err, Result, matrix::pdu::PduBuilder};
+use ruma::{
+	api::client::membership::unban_user,
+	events::room::member::{MembershipState, RoomMemberEventContent},
+};
+
+use crate::Ruma;
+
+/// # `POST /_matrix/client/r0/rooms/{roomId}/unban`
+///
+/// Tries to send an unban event into the room.
+pub(crate) async fn unban_user_route(
+	State(services): State<crate::State>,
+	body: Ruma<unban_user::v3::Request>,
+) -> Result<unban_user::v3::Response> {
+	let sender_user = body.sender_user();
+	if services.users.is_suspended(sender_user).await? {
+		return Err!(Request(UserSuspended("You cannot perform this action while suspended.")));
+	}
+	let state_lock = services.rooms.state.mutex.lock(&body.room_id).await;
+
+	let current_member_content = services
+		.rooms
+		.state_accessor
+		.get_member(&body.room_id, &body.user_id)
+		.await
+		.unwrap_or_else(|_| RoomMemberEventContent::new(MembershipState::Leave));
+
+	if current_member_content.membership != MembershipState::Ban {
+		return Err!(Request(Forbidden(
+			"Cannot unban a user who is not banned (current membership: {})",
+			current_member_content.membership
+		)));
+	}
+
+	services
+		.rooms
+		.timeline
+		.build_and_append_pdu(
+			PduBuilder::state(body.user_id.to_string(), &RoomMemberEventContent {
+				membership: MembershipState::Leave,
+				reason: body.reason.clone(),
+				join_authorized_via_users_server: None,
+				third_party_invite: None,
+				is_direct: None,
+				..current_member_content
+			}),
+			sender_user,
+			&body.room_id,
+			&state_lock,
+		)
+		.await?;
+
+	drop(state_lock);
+
+	Ok(unban_user::v3::Response::new())
+}

src/api/client/profile.rs

@@ -4,11 +4,14 @@ use axum::extract::State;
 use conduwuit::{
 	Err, Result,
 	matrix::pdu::PduBuilder,
-	utils::{IterStream, stream::TryIgnore},
+	utils::{IterStream, future::TryExtExt, stream::TryIgnore},
 	warn,
 };
 use conduwuit_service::Services;
-use futures::{StreamExt, TryStreamExt, future::join3};
+use futures::{
+	StreamExt, TryStreamExt,
+	future::{join, join3, join4},
+};
 use ruma::{
 	OwnedMxcUri, OwnedRoomId, UserId,
 	api::{
@@ -214,10 +217,13 @@ pub(crate) async fn get_avatar_url_route(
 		return Err!(Request(NotFound("Profile was not found.")));
 	}
 
-	Ok(get_avatar_url::v3::Response {
-		avatar_url: services.users.avatar_url(&body.user_id).await.ok(),
-		blurhash: services.users.blurhash(&body.user_id).await.ok(),
-	})
+	let (avatar_url, blurhash) = join(
+		services.users.avatar_url(&body.user_id).ok(),
+		services.users.blurhash(&body.user_id).ok(),
+	)
+	.await;
+
+	Ok(get_avatar_url::v3::Response { avatar_url, blurhash })
 }
 
 /// # `GET /_matrix/client/v3/profile/{userId}`
@@ -297,11 +303,19 @@ pub(crate) async fn get_profile_route(
 	custom_profile_fields.remove("us.cloke.msc4175.tz");
 	custom_profile_fields.remove("m.tz");
 
+	let (avatar_url, blurhash, displayname, tz) = join4(
+		services.users.avatar_url(&body.user_id).ok(),
+		services.users.blurhash(&body.user_id).ok(),
+		services.users.displayname(&body.user_id).ok(),
+		services.users.timezone(&body.user_id).ok(),
+	)
+	.await;
+
 	Ok(get_profile::v3::Response {
-		avatar_url: services.users.avatar_url(&body.user_id).await.ok(),
-		blurhash: services.users.blurhash(&body.user_id).await.ok(),
-		displayname: services.users.displayname(&body.user_id).await.ok(),
-		tz: services.users.timezone(&body.user_id).await.ok(),
+		avatar_url,
+		blurhash,
+		displayname,
+		tz,
 		custom_profile_fields,
 	})
 }
@@ -313,16 +327,12 @@ pub async fn update_displayname(
 	all_joined_rooms: &[OwnedRoomId],
 ) {
 	let (current_avatar_url, current_blurhash, current_displayname) = join3(
-		services.users.avatar_url(user_id),
-		services.users.blurhash(user_id),
-		services.users.displayname(user_id),
+		services.users.avatar_url(user_id).ok(),
+		services.users.blurhash(user_id).ok(),
+		services.users.displayname(user_id).ok(),
 	)
 	.await;
 
-	let current_avatar_url = current_avatar_url.ok();
-	let current_blurhash = current_blurhash.ok();
-	let current_displayname = current_displayname.ok();
-
 	if displayname == current_displayname {
 		return;
 	}
@@ -366,16 +376,12 @@ pub async fn update_avatar_url(
 	all_joined_rooms: &[OwnedRoomId],
 ) {
 	let (current_avatar_url, current_blurhash, current_displayname) = join3(
-		services.users.avatar_url(user_id),
-		services.users.blurhash(user_id),
-		services.users.displayname(user_id),
+		services.users.avatar_url(user_id).ok(),
+		services.users.blurhash(user_id).ok(),
+		services.users.displayname(user_id).ok(),
 	)
 	.await;
 
-	let current_avatar_url = current_avatar_url.ok();
-	let current_blurhash = current_blurhash.ok();
-	let current_displayname = current_displayname.ok();
-
 	if current_avatar_url == avatar_url && current_blurhash == blurhash {
 		return;
 	}

src/api/client/room/initial_sync.rs

@@ -1,9 +1,9 @@
 use axum::extract::State;
 use conduwuit::{
 	Err, Event, Result, at,
-	utils::{BoolExt, stream::TryTools},
+	utils::{BoolExt, future::TryExtExt, stream::TryTools},
 };
-use futures::TryStreamExt;
+use futures::{FutureExt, TryStreamExt, future::try_join4};
 use ruma::api::client::room::initial_sync::v3::{PaginationChunk, Request, Response};
 
 use crate::Ruma;
@@ -25,22 +25,31 @@ pub(crate) async fn room_initial_sync_route(
 		return Err!(Request(Forbidden("No room preview available.")));
 	}
 
-	let limit = LIMIT_MAX;
-	let events: Vec<_> = services
+	let membership = services
 		.rooms
-		.timeline
-		.pdus_rev(None, room_id, None)
-		.try_take(limit)
-		.try_collect()
-		.await?;
+		.state_cache
+		.user_membership(body.sender_user(), room_id)
+		.map(Ok);
 
-	let state: Vec<_> = services
+	let visibility = services.rooms.directory.visibility(room_id).map(Ok);
+
+	let state = services
 		.rooms
 		.state_accessor
 		.room_state_full_pdus(room_id)
 		.map_ok(Event::into_format)
-		.try_collect()
-		.await?;
+		.try_collect::<Vec<_>>();
+
+	let limit = LIMIT_MAX;
+	let events = services
+		.rooms
+		.timeline
+		.pdus_rev(None, room_id, None)
+		.try_take(limit)
+		.try_collect::<Vec<_>>();
+
+	let (membership, visibility, state, events) =
+		try_join4(membership, visibility, state, events).await?;
 
 	let messages = PaginationChunk {
 		start: events.last().map(at!(0)).as_ref().map(ToString::to_string),
@@ -64,11 +73,7 @@ pub(crate) async fn room_initial_sync_route(
 		account_data: None,
 		state: state.into(),
 		messages: messages.chunk.is_empty().or_some(messages),
-		visibility: services.rooms.directory.visibility(room_id).await.into(),
-		membership: services
-			.rooms
-			.state_cache
-			.user_membership(body.sender_user(), room_id)
-			.await,
+		visibility: visibility.into(),
+		membership,
 	})
 }