continuwuity/src/api/server/make_knock.rs

use axum::extract::State;
use conduit::Err;
use ruma::{
	api::{client::error::ErrorKind, federation::knock::create_knock_event_template},
	events::room::member::{MembershipState, RoomMemberEventContent},
	RoomVersionId,
};
use serde_json::value::to_raw_value;
use tracing::warn;
use RoomVersionId::*;

use crate::{service::pdu::PduBuilder, Error, Result, Ruma};

/// # `GET /_matrix/federation/v1/make_knock/{roomId}/{userId}`
///
/// Creates a knock template.
pub(crate) async fn create_knock_event_template_route(
	State(services): State<crate::State>, body: Ruma<create_knock_event_template::v1::Request>,
) -> Result<create_knock_event_template::v1::Response> {
	if !services.rooms.metadata.exists(&body.room_id).await {
		return Err(Error::BadRequest(ErrorKind::NotFound, "Room is unknown to this server."));
	}

	if body.user_id.server_name() != body.origin() {
		return Err(Error::BadRequest(
			ErrorKind::InvalidParam,
			"Not allowed to knock on behalf of another server/user",
		));
	}

	// ACL check origin server
	services
		.rooms
		.event_handler
		.acl_check(body.origin(), &body.room_id)
		.await?;

	if services
		.globals
		.config
		.forbidden_remote_server_names
		.contains(body.origin())
	{
		warn!(
			"Server {} for remote user {} tried knocking room ID {} which has a server name that is globally \
			 forbidden. Rejecting.",
			body.origin(),
			&body.user_id,
			&body.room_id,
		);
		return Err!(Request(Forbidden("Server is banned on this homeserver.")));
	}

	if let Some(server) = body.room_id.server_name() {
		if services
			.globals
			.config
			.forbidden_remote_server_names
			.contains(&server.to_owned())
		{
			return Err!(Request(Forbidden("Server is banned on this homeserver.")));
		}
	}

	let room_version_id = services.rooms.state.get_room_version(&body.room_id).await?;

	if matches!(room_version_id, V1 | V2 | V3 | V4 | V5 | V6) {
		return Err(Error::BadRequest(
			ErrorKind::IncompatibleRoomVersion {
				room_version: room_version_id,
			},
			"Room version does not support knocking.",
		));
	}

	if !body.ver.contains(&room_version_id) {
		return Err(Error::BadRequest(
			ErrorKind::IncompatibleRoomVersion {
				room_version: room_version_id,
			},
			"Your homeserver does not support the features required to knock on this room.",
		));
	}

	let state_lock = services.rooms.state.mutex.lock(&body.room_id).await;

	let (_pdu, mut pdu_json) = services
		.rooms
		.timeline
		.create_hash_and_sign_event(
			PduBuilder::state(body.user_id.to_string(), &RoomMemberEventContent::new(MembershipState::Knock)),
			&body.user_id,
			&body.room_id,
			&state_lock,
		)
		.await?;

	drop(state_lock);

	// room v3 and above removed the "event_id" field from remote PDU format
	super::maybe_strip_event_id(&mut pdu_json, &room_version_id)?;

	Ok(create_knock_event_template::v1::Response {
		room_version: room_version_id,
		event: to_raw_value(&pdu_json).expect("CanonicalJson can be serialized to JSON"),
	})
}