server_server.rs

use crate::{client_server, utils, ConduitResult, Database, Error, PduEvent, Result, Ruma};
use get_profile_information::v1::ProfileField;
use http::header::{HeaderValue, AUTHORIZATION, HOST};
use log::{debug, error, info, warn};
use regex::Regex;
use rocket::{response::content::Json, State};
use ruma::{
    api::{
        client::error::ErrorKind,
        federation::{
            directory::{get_public_rooms, get_public_rooms_filtered},
            discovery::{
                get_remote_server_keys, get_server_keys,
                get_server_version::v1 as get_server_version, ServerSigningKeys, VerifyKey,
            },
            event::{get_event, get_missing_events, get_room_state_ids},
            query::get_profile_information,
            transactions::send_transaction_message,
        },
        OutgoingRequest,
    },
    directory::{IncomingFilter, IncomingRoomNetwork},
    events::EventType,
    identifiers::{KeyId, KeyName},
    serde::to_canonical_value,
    signatures::{CanonicalJsonObject, CanonicalJsonValue, PublicKeyMap},
    EventId, RoomId, RoomVersionId, ServerName, ServerSigningKeyId, SigningKeyAlgorithm, UserId,
};
use state_res::{Event, EventMap, StateMap};
use std::{
    collections::{BTreeMap, BTreeSet, HashMap},
    convert::TryFrom,
    fmt::Debug,
    future::Future,
    net::{IpAddr, SocketAddr},
    pin::Pin,
    result::Result as StdResult,
    sync::Arc,
    time::{Duration, SystemTime},
};

#[cfg(feature = "conduit_bin")]
use rocket::{get, post, put};

#[tracing::instrument(skip(globals))]
pub async fn send_request<T: OutgoingRequest>(
    globals: &crate::database::globals::Globals,
    destination: &ServerName,
    request: T,
) -> Result<T::IncomingResponse>
where
    T: Debug,
{
    if !globals.allow_federation() {
        return Err(Error::bad_config("Federation is disabled."));
    }

    let maybe_result = globals
        .actual_destination_cache
        .read()
        .unwrap()
        .get(destination)
        .cloned();

    let (actual_destination, host) = if let Some(result) = maybe_result {
        result
    } else {
        let result = find_actual_destination(globals, &destination).await;
        globals
            .actual_destination_cache
            .write()
            .unwrap()
            .insert(Box::<ServerName>::from(destination), result.clone());
        result
    };

    let mut http_request = request
        .try_into_http_request(&actual_destination, Some(""))
        .map_err(|e| {
            warn!("Failed to find destination {}: {}", actual_destination, e);
            Error::BadServerResponse("Invalid destination")
        })?;

    let mut request_map = serde_json::Map::new();

    if !http_request.body().is_empty() {
        request_map.insert(
            "content".to_owned(),
            serde_json::from_slice(http_request.body())
                .expect("body is valid json, we just created it"),
        );
    };

    request_map.insert("method".to_owned(), T::METADATA.method.to_string().into());
    request_map.insert(
        "uri".to_owned(),
        http_request
            .uri()
            .path_and_query()
            .expect("all requests have a path")
            .to_string()
            .into(),
    );
    request_map.insert("origin".to_owned(), globals.server_name().as_str().into());
    request_map.insert("destination".to_owned(), destination.as_str().into());

    let mut request_json =
        serde_json::from_value(request_map.into()).expect("valid JSON is valid BTreeMap");

    ruma::signatures::sign_json(
        globals.server_name().as_str(),
        globals.keypair(),
        &mut request_json,
    )
    .expect("our request json is what ruma expects");

    let request_json: serde_json::Map<String, serde_json::Value> =
        serde_json::from_slice(&serde_json::to_vec(&request_json).unwrap()).unwrap();

    let signatures = request_json["signatures"]
        .as_object()
        .unwrap()
        .values()
        .map(|v| {
            v.as_object()
                .unwrap()
                .iter()
                .map(|(k, v)| (k, v.as_str().unwrap()))
        });

    for signature_server in signatures {
        for s in signature_server {
            http_request.headers_mut().insert(
                AUTHORIZATION,
                HeaderValue::from_str(&format!(
                    "X-Matrix origin={},key=\"{}\",sig=\"{}\"",
                    globals.server_name(),
                    s.0,
                    s.1
                ))
                .unwrap(),
            );
        }
    }

    http_request
        .headers_mut()
        .insert(HOST, HeaderValue::from_str(&host).unwrap());

    let mut reqwest_request = reqwest::Request::try_from(http_request)
        .expect("all http requests are valid reqwest requests");

    *reqwest_request.timeout_mut() = Some(Duration::from_secs(30));

    let url = reqwest_request.url().clone();
    let reqwest_response = globals.reqwest_client().execute(reqwest_request).await;

    // Because reqwest::Response -> http::Response is complicated:
    match reqwest_response {
        Ok(mut reqwest_response) => {
            let status = reqwest_response.status();
            let mut http_response = http::Response::builder().status(status);
            let headers = http_response.headers_mut().unwrap();

            for (k, v) in reqwest_response.headers_mut().drain() {
                if let Some(key) = k {
                    headers.insert(key, v);
                }
            }

            let status = reqwest_response.status();

            let body = reqwest_response
                .bytes()
                .await
                .unwrap_or_else(|e| {
                    warn!("server error {}", e);
                    Vec::new().into()
                }) // TODO: handle timeout
                .into_iter()
                .collect::<Vec<_>>();

            if status != 200 {
                info!(
                    "Server returned bad response {} {}\n{}\n{:?}",
                    destination,
                    status,
                    url,
                    utils::string_from_bytes(&body)
                );
            }

            let response = T::IncomingResponse::try_from(
                http_response
                    .body(body)
                    .expect("reqwest body is valid http body"),
            );
            response.map_err(|_| {
                info!(
                    "Server returned invalid response bytes {}\n{}",
                    destination, url
                );
                Error::BadServerResponse("Server returned bad response.")
            })
        }
        Err(e) => Err(e.into()),
    }
}

#[tracing::instrument]
fn get_ip_with_port(destination_str: String) -> Option<String> {
    if destination_str.parse::<SocketAddr>().is_ok() {
        Some(destination_str)
    } else if let Ok(ip_addr) = destination_str.parse::<IpAddr>() {
        Some(SocketAddr::new(ip_addr, 8448).to_string())
    } else {
        None
    }
}

#[tracing::instrument]
fn add_port_to_hostname(destination_str: String) -> String {
    match destination_str.find(':') {
        None => destination_str.to_owned() + ":8448",
        Some(_) => destination_str.to_string(),
    }
}

/// Returns: actual_destination, host header
/// Implemented according to the specification at https://matrix.org/docs/spec/server_server/r0.1.4#resolving-server-names
/// Numbers in comments below refer to bullet points in linked section of specification
#[tracing::instrument(skip(globals))]
async fn find_actual_destination(
    globals: &crate::database::globals::Globals,
    destination: &'_ ServerName,
) -> (String, String) {
    let destination_str = destination.as_str().to_owned();
    let mut host = destination_str.clone();
    let actual_destination = "https://".to_owned()
        + &match get_ip_with_port(destination_str.clone()) {
            Some(host_port) => {
                // 1: IP literal with provided or default port
                host_port
            }
            None => {
                if destination_str.find(':').is_some() {
                    // 2: Hostname with included port
                    destination_str
                } else {
                    match request_well_known(globals, &destination.as_str()).await {
                        // 3: A .well-known file is available
                        Some(delegated_hostname) => {
                            host = delegated_hostname.clone();
                            match get_ip_with_port(delegated_hostname.clone()) {
                                Some(host_and_port) => host_and_port, // 3.1: IP literal in .well-known file
                                None => {
                                    if destination_str.find(':').is_some() {
                                        // 3.2: Hostname with port in .well-known file
                                        destination_str
                                    } else {
                                        match query_srv_record(globals, &delegated_hostname).await {
                                            // 3.3: SRV lookup successful
                                            Some(hostname) => hostname,
                                            // 3.4: No SRV records, just use the hostname from .well-known
                                            None => add_port_to_hostname(delegated_hostname),
                                        }
                                    }
                                }
                            }
                        }
                        // 4: No .well-known or an error occured
                        None => {
                            match query_srv_record(globals, &destination_str).await {
                                // 4: SRV record found
                                Some(hostname) => hostname,
                                // 5: No SRV record found
                                None => add_port_to_hostname(destination_str.to_string()),
                            }
                        }
                    }
                }
            }
        };

    (actual_destination, host)
}

#[tracing::instrument(skip(globals))]
async fn query_srv_record(
    globals: &crate::database::globals::Globals,
    hostname: &'_ str,
) -> Option<String> {
    if let Ok(Some(host_port)) = globals
        .dns_resolver()
        .srv_lookup(format!("_matrix._tcp.{}", hostname))
        .await
        .map(|srv| {
            srv.iter().next().map(|result| {
                format!(
                    "{}:{}",
                    result.target().to_string().trim_end_matches('.'),
                    result.port().to_string()
                )
            })
        })
    {
        Some(host_port)
    } else {
        None
    }
}

#[tracing::instrument(skip(globals))]
pub async fn request_well_known(
    globals: &crate::database::globals::Globals,
    destination: &str,
) -> Option<String> {
    let body: serde_json::Value = serde_json::from_str(
        &globals
            .reqwest_client()
            .get(&format!(
                "https://{}/.well-known/matrix/server",
                destination
            ))
            .send()
            .await
            .ok()?
            .text()
            .await
            .ok()?,
    )
    .ok()?;
    Some(body.get("m.server")?.as_str()?.to_owned())
}

#[cfg_attr(feature = "conduit_bin", get("/_matrix/federation/v1/version"))]
#[tracing::instrument(skip(db))]
pub fn get_server_version_route(
    db: State<'_, Database>,
) -> ConduitResult<get_server_version::Response> {
    if !db.globals.allow_federation() {
        return Err(Error::bad_config("Federation is disabled."));
    }

    Ok(get_server_version::Response {
        server: Some(get_server_version::Server {
            name: Some("Conduit".to_owned()),
            version: Some(env!("CARGO_PKG_VERSION").to_owned()),
        }),
    }
    .into())
}

#[cfg_attr(feature = "conduit_bin", get("/_matrix/key/v2/server"))]
#[tracing::instrument(skip(db))]
pub fn get_server_keys_route(db: State<'_, Database>) -> Json<String> {
    if !db.globals.allow_federation() {
        // TODO: Use proper types
        return Json("Federation is disabled.".to_owned());
    }

    let mut verify_keys = BTreeMap::new();
    verify_keys.insert(
        ServerSigningKeyId::try_from(
            format!("ed25519:{}", db.globals.keypair().version()).as_str(),
        )
        .expect("found invalid server signing keys in DB"),
        VerifyKey {
            key: base64::encode_config(db.globals.keypair().public_key(), base64::STANDARD_NO_PAD),
        },
    );
    let mut response = serde_json::from_slice(
        http::Response::try_from(get_server_keys::v2::Response {
            server_key: ServerSigningKeys {
                server_name: db.globals.server_name().to_owned(),
                verify_keys,
                old_verify_keys: BTreeMap::new(),
                signatures: BTreeMap::new(),
                valid_until_ts: SystemTime::now() + Duration::from_secs(60 * 2),
            },
        })
        .unwrap()
        .body(),
    )
    .unwrap();

    ruma::signatures::sign_json(
        db.globals.server_name().as_str(),
        db.globals.keypair(),
        &mut response,
    )
    .unwrap();

    Json(ruma::serde::to_canonical_json_string(&response).expect("JSON is canonical"))
}

#[cfg_attr(feature = "conduit_bin", get("/_matrix/key/v2/server/<_>"))]
#[tracing::instrument(skip(db))]
pub fn get_server_keys_deprecated_route(db: State<'_, Database>) -> Json<String> {
    get_server_keys_route(db)
}

#[cfg_attr(
    feature = "conduit_bin",
    post("/_matrix/federation/v1/publicRooms", data = "<body>")
)]
#[tracing::instrument(skip(db, body))]
pub async fn get_public_rooms_filtered_route(
    db: State<'_, Database>,
    body: Ruma<get_public_rooms_filtered::v1::Request<'_>>,
) -> ConduitResult<get_public_rooms_filtered::v1::Response> {
    if !db.globals.allow_federation() {
        return Err(Error::bad_config("Federation is disabled."));
    }

    let response = client_server::get_public_rooms_filtered_helper(
        &db,
        None,
        body.limit,
        body.since.as_deref(),
        &body.filter,
        &body.room_network,
    )
    .await?
    .0;

    Ok(get_public_rooms_filtered::v1::Response {
        chunk: response
            .chunk
            .into_iter()
            .map(|c| {
                // Convert ruma::api::federation::directory::get_public_rooms::v1::PublicRoomsChunk
                // to ruma::api::client::r0::directory::PublicRoomsChunk
                Ok::<_, Error>(
                    serde_json::from_str(
                        &serde_json::to_string(&c)
                            .expect("PublicRoomsChunk::to_string always works"),
                    )
                    .expect("federation and client-server PublicRoomsChunk are the same type"),
                )
            })
            .filter_map(|r| r.ok())
            .collect(),
        prev_batch: response.prev_batch,
        next_batch: response.next_batch,
        total_room_count_estimate: response.total_room_count_estimate,
    }
    .into())
}

#[cfg_attr(
    feature = "conduit_bin",
    get("/_matrix/federation/v1/publicRooms", data = "<body>")
)]
#[tracing::instrument(skip(db, body))]
pub async fn get_public_rooms_route(
    db: State<'_, Database>,
    body: Ruma<get_public_rooms::v1::Request<'_>>,
) -> ConduitResult<get_public_rooms::v1::Response> {
    if !db.globals.allow_federation() {
        return Err(Error::bad_config("Federation is disabled."));
    }

    let response = client_server::get_public_rooms_filtered_helper(
        &db,
        None,
        body.limit,
        body.since.as_deref(),
        &IncomingFilter::default(),
        &IncomingRoomNetwork::Matrix,
    )
    .await?
    .0;

    Ok(get_public_rooms::v1::Response {
        chunk: response
            .chunk
            .into_iter()
            .map(|c| {
                // Convert ruma::api::federation::directory::get_public_rooms::v1::PublicRoomsChunk
                // to ruma::api::client::r0::directory::PublicRoomsChunk
                Ok::<_, Error>(
                    serde_json::from_str(
                        &serde_json::to_string(&c)
                            .expect("PublicRoomsChunk::to_string always works"),
                    )
                    .expect("federation and client-server PublicRoomsChunk are the same type"),
                )
            })
            .filter_map(|r| r.ok())
            .collect(),
        prev_batch: response.prev_batch,
        next_batch: response.next_batch,
        total_room_count_estimate: response.total_room_count_estimate,
    }
    .into())
}

#[cfg_attr(
    feature = "conduit_bin",
    put("/_matrix/federation/v1/send/<_>", data = "<body>")
)]
#[tracing::instrument(skip(db, body))]
pub async fn send_transaction_message_route<'a>(
    db: State<'a, Database>,
    body: Ruma<send_transaction_message::v1::Request<'_>>,
) -> ConduitResult<send_transaction_message::v1::Response> {
    if !db.globals.allow_federation() {
        return Err(Error::bad_config("Federation is disabled."));
    }

    info!("Incoming PDUs: {:?}", &body.pdus);

    for edu in &body.edus {
        match serde_json::from_str::<send_transaction_message::v1::Edu>(edu.json().get()) {
            Ok(edu) => match edu.edu_type.as_str() {
                "m.typing" => {
                    if let Some(typing) = edu.content.get("typing") {
                        if typing.as_bool().unwrap_or_default() {
                            db.rooms.edus.typing_add(
                                &UserId::try_from(edu.content["user_id"].as_str().unwrap())
                                    .unwrap(),
                                &RoomId::try_from(edu.content["room_id"].as_str().unwrap())
                                    .unwrap(),
                                3000 + utils::millis_since_unix_epoch(),
                                &db.globals,
                            )?;
                        } else {
                            db.rooms.edus.typing_remove(
                                &UserId::try_from(edu.content["user_id"].as_str().unwrap())
                                    .unwrap(),
                                &RoomId::try_from(edu.content["room_id"].as_str().unwrap())
                                    .unwrap(),
                                &db.globals,
                            )?;
                        }
                    }
                }
                "m.presence" => {}
                "m.receipt" => {}
                "m.device_list_update" => {}
                _ => {}
            },
            Err(_err) => {
                continue;
            }
        }
    }

    let mut resolved_map = BTreeMap::new();

    let pdus_to_resolve = body
        .pdus
        .iter()
        .filter_map(|pdu| {
            // 1. Is a valid event, otherwise it is dropped.
            // Ruma/PduEvent/StateEvent satisfies this
            // We do not add the event_id field to the pdu here because of signature and hashes checks
            let (event_id, value) = match crate::pdu::gen_event_id_canonical_json(pdu) {
                Ok(t) => t,
                Err(_) => {
                    // Event could not be converted to canonical json
                    return None;
                }
            };

            // If we have no idea about this room skip the PDU
            let room_id = match value
                .get("room_id")
                .map(|id| match id {
                    CanonicalJsonValue::String(id) => RoomId::try_from(id.as_str()).ok(),
                    _ => None,
                })
                .flatten()
            {
                Some(id) => id,
                None => {
                    resolved_map.insert(event_id, Err("Event needs a valid RoomId".to_string()));
                    return None;
                }
            };

            // 1. check the server is in the room (optional)
            match db.rooms.exists(&room_id) {
                Ok(true) => {}
                _ => {
                    resolved_map
                        .insert(event_id, Err("Room is unknown to this server".to_string()));
                    return None;
                }
            }

            // If we know of this pdu we don't need to continue processing it
            if let Ok(Some(_)) = db.rooms.get_pdu_id(&event_id) {
                return None;
            }

            Some((event_id, room_id, value))
        })
        .collect::<Vec<_>>();

    // TODO: For RoomVersion6 we must check that Raw<..> is canonical do we anywhere?
    // SPEC:
    // Servers MUST strictly enforce the JSON format specified in the appendices.
    // This translates to a 400 M_BAD_JSON error on most endpoints, or discarding of
    // events over federation. For example, the Federation API's /send endpoint would
    // discard the event whereas the Client Server API's /send/{eventType} endpoint
    // would return a M_BAD_JSON error.
    'main_pdu_loop: for (event_id, _room_id, value) in pdus_to_resolve {
        info!("Working on incoming pdu: {:?}", value);
        let server_name = &body.body.origin;
        let mut pub_key_map = BTreeMap::new();

        // TODO: make this persist but not a DB Tree...
        // This is all the auth_events that have been recursively fetched so they don't have to be
        // deserialized over and over again. This could potentially also be some sort of trie (suffix tree)
        // like structure so that once an auth event is known it would know (using indexes maybe) all of
        // the auth events that it references.
        let mut auth_cache = EventMap::new();

        // 2. check content hash, redact if doesn't match
        // 3. fetch any missing auth events doing all checks listed here starting at 1. These are not timeline events
        // 4. reject "due to auth events" if can't get all the auth events or some of the auth events are also rejected "due to auth events"
        // 5. reject "due to auth events" if the event doesn't pass auth based on the auth events
        // 7. if not timeline event: stop
        // TODO; 8. fetch any missing prev events doing all checks listed here starting at 1. These are timeline events
        // the events found in step 8 can be authed/resolved and appended to the DB
        let (pdu, previous_create): (Arc<PduEvent>, Option<Arc<PduEvent>>) = match validate_event(
            &db,
            value,
            event_id.clone(),
            &mut pub_key_map,
            server_name,
            // All the auth events gathered will be here
            &mut auth_cache,
        )
        .await
        {
            Ok(pdu) => pdu,
            Err(e) => {
                resolved_map.insert(event_id, Err(e));
                continue;
            }
        };
        debug!("Validated event.");

        // 6. persist the event as an outlier.
        db.rooms.add_pdu_outlier(&pdu)?;
        info!("Added pdu as outlier.");

        // Step 9. fetch missing state by calling /state_ids at backwards extremities doing all
        // the checks in this list starting at 1. These are not timeline events.
        //
        // Step 10. check the auth of the event passes based on the calculated state of the event
        //
        // TODO: if we know the prev_events of the incoming event we can avoid the request and build
        // the state from a known point and resolve if > 1 prev_event
        debug!("Requesting state at event.");
        let (state_at_event, incoming_auth_events): (StateMap<Arc<PduEvent>>, Vec<Arc<PduEvent>>) =
            match db
                .sending
                .send_federation_request(
                    &db.globals,
                    server_name,
                    get_room_state_ids::v1::Request {
                        room_id: pdu.room_id(),
                        event_id: pdu.event_id(),
                    },
                )
                .await
            {
                Ok(res) => {
                    debug!("Fetching state events at event.");
                    let state = match fetch_events(
                        &db,
                        server_name,
                        &mut pub_key_map,
                        &res.pdu_ids,
                        &mut auth_cache,
                    )
                    .await
                    {
                        Ok(state) => state,
                        Err(_) => continue,
                    };

                    // Sanity check: there are no conflicting events in the state we received
                    let mut seen = BTreeSet::new();
                    for ev in &state {
                        // If the key is already present
                        if !seen.insert((&ev.kind, &ev.state_key)) {
                            error!("Server sent us an invalid state");
                            continue;
                        }
                    }

                    let state = state
                        .into_iter()
                        .map(|pdu| ((pdu.kind.clone(), pdu.state_key.clone()), pdu))
                        .collect();

                    let incoming_auth_events = match fetch_events(
                        &db,
                        server_name,
                        &mut pub_key_map,
                        &res.auth_chain_ids,
                        &mut auth_cache,
                    )
                    .await
                    {
                        Ok(state) => state,
                        Err(_) => continue,
                    };

                    debug!("Fetching auth events of state events at event.");
                    (state, incoming_auth_events)
                }
                Err(_) => {
                    resolved_map.insert(
                        pdu.event_id().clone(),
                        Err("Fetching state for event failed".into()),
                    );
                    continue;
                }
            };

        // 10. This is the actual auth check for state at the event
        if !state_res::event_auth::auth_check(
            &RoomVersionId::Version6,
            &pdu,
            previous_create.clone(),
            &state_at_event,
            None, // TODO: third party invite
        )
        .map_err(|_e| Error::Conflict("Auth check failed"))?
        {
            // Event failed auth with state_at
            resolved_map.insert(
                event_id,
                Err("Event has failed auth check with state at the event".into()),
            );
            continue;
        }
        debug!("Auth check succeeded.");
        // End of step 10.

        // 12. check if the event passes auth based on the "current state" of the room, if not "soft fail" it
        let current_state = db
            .rooms
            .room_state_full(pdu.room_id())?
            .into_iter()
            .map(|(k, v)| ((k.0, Some(k.1)), Arc::new(v)))
            .collect();

        if !state_res::event_auth::auth_check(
            &RoomVersionId::Version6,
            &pdu,
            previous_create,
            &current_state,
            None,
        )
        .map_err(|_e| Error::Conflict("Auth check failed"))?
        {
            // Soft fail, we add the event as an outlier.
            resolved_map.insert(
                pdu.event_id().clone(),
                Err("Event has been soft failed".into()),
            );
            continue;
        };
        debug!("Auth check with current state succeeded.");

        // Step 11. Ensure that the state is derived from the previous current state (i.e. we calculated by doing state res
        // where one of the inputs was a previously trusted set of state, don't just trust a set of state we got from a remote)
        //
        // calculate_forward_extremities takes care of adding the current state if not already in the state sets
        // it also calculates the new pdu leaves for the `roomid_pduleaves` DB Tree.
        let extremities = match calculate_forward_extremities(&db, &pdu).await {
            Ok(fork_ids) => {
                debug!("Calculated new forward extremities: {:?}", fork_ids);
                fork_ids
            }
            Err(_) => {
                resolved_map.insert(event_id, Err("Failed to gather forward extremities".into()));
                continue;
            }
        };

        // This will create the state after any state snapshot it builds
        // So current_state will have the incoming event inserted to it
        let mut fork_states = match build_forward_extremity_snapshots(
            &db,
            pdu.clone(),
            server_name,
            current_state,
            &extremities,
            &pub_key_map,
            &mut auth_cache,
        )
        .await
        {
            Ok(states) => states,
            Err(_) => {
                resolved_map.insert(event_id, Err("Failed to gather forward extremities".into()));
                continue;
            }
        };

        // Make this the state after.
        let mut state_after = state_at_event.clone();
        state_after.insert((pdu.kind(), pdu.state_key()), pdu.clone());
        // Add the incoming event to the mix of state snapshots
        // Since we are using a BTreeSet (yea this may be overkill) we guarantee unique state sets
        fork_states.insert(state_after.clone());

        let fork_states = fork_states.into_iter().collect::<Vec<_>>();

        let mut update_state = false;
        // 13. start state-res with all previous forward extremities minus the ones that are in
        // the prev_events of this event plus the new one created by this event and use
        // the result as the new room state
        let state_at_forks = if fork_states.is_empty() {
            // State is empty
            Default::default()
        } else if fork_states.len() == 1 {
            fork_states[0].clone()
        } else {
            // We do need to force an update to this rooms state
            update_state = true;

            let mut auth_events = vec![];
            for map in &fork_states {
                let mut state_auth = vec![];
                for auth_id in map.values().flat_map(|pdu| &pdu.auth_events) {
                    match fetch_events(
                        &db,
                        server_name,
                        &mut pub_key_map,
                        &[auth_id.clone()],
                        &mut auth_cache,
                    )
                    .await
                    {
                        // This should always contain exactly one element when Ok
                        Ok(events) => state_auth.push(events[0].clone()),
                        Err(e) => {
                            debug!("Event was not present: {}", e);
                        }
                    }
                }
                auth_events.push(state_auth);
            }

            // Add everything we will need to event_map
            auth_cache.extend(
                auth_events
                    .iter()
                    .map(|pdus| pdus.iter().map(|pdu| (pdu.event_id().clone(), pdu.clone())))
                    .flatten(),
            );
            auth_cache.extend(
                incoming_auth_events
                    .into_iter()
                    .map(|pdu| (pdu.event_id().clone(), pdu)),
            );
            auth_cache.extend(
                state_after
                    .into_iter()
                    .map(|(_, pdu)| (pdu.event_id().clone(), pdu)),
            );

            let res = match state_res::StateResolution::resolve(
                pdu.room_id(),
                &RoomVersionId::Version6,
                &fork_states
                    .into_iter()
                    .map(|map| {
                        map.into_iter()
                            .map(|(k, v)| (k, v.event_id.clone()))
                            .collect::<StateMap<_>>()
                    })
                    .collect::<Vec<_>>(),
                auth_events
                    .into_iter()
                    .map(|pdus| pdus.into_iter().map(|pdu| pdu.event_id().clone()).collect())
                    .collect(),
                &mut auth_cache,
            ) {
                Ok(res) => res,
                Err(_) => {
                    resolved_map.insert(
                        pdu.event_id().clone(),
                        Err("State resolution failed, either an event could not be found or deserialization".into()),
                    );
                    continue 'main_pdu_loop;
                }
            };

            let mut resolved = BTreeMap::new();
            for (k, id) in res {
                // We should know of the event but just incase
                let pdu = match auth_cache.get(&id) {
                    Some(pdu) => pdu.clone(),
                    None => {
                        error!("Event was not present in auth_cache {}", id);
                        resolved_map.insert(
                            event_id.clone(),
                            Err("Event was not present in auth cache".into()),
                        );
                        continue 'main_pdu_loop;
                    }
                };
                resolved.insert(k, pdu);
            }
            resolved
        };

        // Now that the event has passed all auth it is added into the timeline.
        // We use the `state_at_event` instead of `state_after` so we accurately
        // represent the state for this event.
        append_incoming_pdu(&db, &pdu, &extremities, &state_at_event)?;
        info!("Appended incoming pdu.");

        // Set the new room state to the resolved state
        update_resolved_state(
            &db,
            pdu.room_id(),
            if update_state {
                Some(state_at_forks)
            } else {
                None
            },
        )?;
        debug!("Updated resolved state");

        // Event has passed all auth/stateres checks
    }

    if !resolved_map.is_empty() {
        warn!("These PDU's failed {:?}", resolved_map);
    }

    Ok(send_transaction_message::v1::Response { pdus: resolved_map }.into())
}

/// An async function that can recursively calls itself.
type AsyncRecursiveResult<'a, T> = Pin<Box<dyn Future<Output = StdResult<T, String>> + 'a + Send>>;

/// TODO: don't add as outlier if event is fetched as a result of gathering auth_events
/// Validate any event that is given to us by another server.
///
/// 1. Is a valid event, otherwise it is dropped (PduEvent deserialization satisfies this).
/// 2. check content hash, redact if doesn't match
/// 3. fetch any missing auth events doing all checks listed here starting at 1. These are not timeline events
/// 4. reject "due to auth events" if can't get all the auth events or some of the auth events are also rejected "due to auth events"
/// 5. reject "due to auth events" if the event doesn't pass auth based on the auth events
/// 7. if not timeline event: stop
/// 8. fetch any missing prev events doing all checks listed here starting at 1. These are timeline events
#[tracing::instrument(skip(db, pub_key_map, auth_cache))]
fn validate_event<'a>(
    db: &'a Database,
    value: CanonicalJsonObject,
    event_id: EventId,
    pub_key_map: &'a mut PublicKeyMap,
    origin: &'a ServerName,
    auth_cache: &'a mut EventMap<Arc<PduEvent>>,
) -> AsyncRecursiveResult<'a, (Arc<PduEvent>, Option<Arc<PduEvent>>)> {
    Box::pin(async move {
        for (signature_server, signature) in match value
            .get("signatures")
            .ok_or_else(|| "No signatures in server response pdu.".to_string())?
        {
            CanonicalJsonValue::Object(map) => map,
            _ => return Err("Invalid signatures object in server response pdu.".to_string()),
        } {
            let signature_object = match signature {
                CanonicalJsonValue::Object(map) => map,
                _ => {
                    return Err(
                        "Invalid signatures content object in server response pdu.".to_string()
                    )
                }
            };

            let signature_ids = signature_object.keys().collect::<Vec<_>>();

            debug!("Fetching signing keys for {}", signature_server);
            let keys = match fetch_signing_keys(
                &db,
                &Box::<ServerName>::try_from(&**signature_server).map_err(|_| {
                    "Invalid servername in signatures of server response pdu.".to_string()
                })?,
                signature_ids,
            )
            .await
            {
                Ok(keys) => keys,
                Err(_) => {
                    return Err(
                        "Signature verification failed: Could not fetch signing key.".to_string(),