Fixing the incoming events algorithm (review with time)

src/database/rooms.rs

@@ -150,7 +150,7 @@ impl Rooms {
         }
     }
 
-    /// Returns the last state hash key added to the db.
+    /// Returns the state hash for this pdu.
     pub fn pdu_state_hash(&self, pdu_id: &[u8]) -> Result<Option<StateHashId>> {
         Ok(self.pduid_statehash.get(pdu_id)?)
     }

src/server_server.rs

@@ -5,6 +5,7 @@ use log::{error, info, warn};
 use rocket::{get, post, put, response::content::Json, State};
 use ruma::{
     api::{
+        client::r0::state,
         federation::{
             directory::{get_public_rooms, get_public_rooms_filtered},
             discovery::{
@@ -590,6 +591,8 @@ pub async fn send_transaction_message_route<'a>(
                 continue;
             }
         };
+
+        // 1. check the server is in the room (optional)
         if !db.rooms.exists(&room_id)? {
             resolved_map.insert(event_id, Err("Room is unknown to this server".to_string()));
             continue;
@@ -634,14 +637,13 @@ pub async fn send_transaction_message_route<'a>(
         // the auth events that it references.
         let mut auth_cache = EventMap::new();
 
-        // 1. check the server is in the room (optional)
         // 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
-        // 6. persist this event as an outlier
         // 7. if not timeline event: stop
-        let pdu = match validate_event(
+        // 8. fetch any missing prev events doing all checks listed here starting at 1. These are timeline events
+        let (pdu, previous) = match validate_event(
             &db,
             value,
             event_id.clone(),
@@ -659,59 +661,16 @@ pub async fn send_transaction_message_route<'a>(
             }
         };
 
-        let pdu = Arc::new(pdu.clone());
-        // Fetch any unknown prev_events or retrieve them from the DB
-        let previous = match fetch_events(
-            &db,
-            server_name,
-            &pub_key_map,
-            &pdu.prev_events,
-            &mut auth_cache,
-        )
-        .await
-        {
-            Ok(mut evs) if evs.len() == 1 => Some(evs.remove(0)),
-            _ => None,
+        let single_prev = if previous.len() == 1 {
+            previous.first().cloned()
+        } else {
+            None
         };
 
-        // [auth_cache] At this point we have the auth chain of the incoming event.
-        let mut event_map: state_res::EventMap<Arc<PduEvent>> = auth_cache
-            .iter()
-            .map(|(k, v)| (k.clone(), v.clone()))
-            .collect();
+        // 6. persist the event as an outlier.
+        db.rooms.append_pdu_outlier(pdu.event_id(), &pdu)?;
 
-        // Check that the event passes auth based on the auth_events
-        let is_authed = state_res::event_auth::auth_check(
-            &RoomVersionId::Version6,
-            &pdu,
-            previous.clone(),
-            &pdu.auth_events
-                .iter()
-                .map(|id| {
-                    auth_cache
-                        .get(id)
-                        .map(|pdu| ((pdu.kind(), pdu.state_key()), pdu.clone()))
-                        .ok_or_else(|| {
-                            Error::Conflict(
-                                "Auth event not found, event failed recursive auth checks.",
-                            )
-                        })
-                })
-                .collect::<Result<BTreeMap<_, _>>>()?,
-            None, // TODO: third party invite
-        )
-        .map_err(|_e| Error::Conflict("Auth check failed"))?;
-
-        if !is_authed {
-            resolved_map.insert(
-                pdu.event_id().clone(),
-                Err("Event has failed auth check with auth events".into()),
-            );
-            continue;
-        }
-        // End of step 4.
-
-        // Step 5. event passes auth based on state at the event
+        // Step 10. check the auth of the event passes based on the calculated state of the event
         let (state_at_event, incoming_auth_events): (StateMap<Arc<PduEvent>>, Vec<Arc<PduEvent>>) =
             match db
                 .sending
@@ -757,9 +716,7 @@ pub async fn send_transaction_message_route<'a>(
                             &res.auth_chain_ids,
                             &mut auth_cache,
                         )
-                        .await?
-                        .into_iter()
-                        .collect(),
+                        .await?,
                     )
                 }
                 Err(_) => {
@@ -771,10 +728,11 @@ pub async fn send_transaction_message_route<'a>(
                 }
             };
 
+        // 10. This is the actual auth check for state at the event
         if !state_res::event_auth::auth_check(
             &RoomVersionId::Version6,
             &pdu,
-            previous.clone(),
+            single_prev.clone(),
             &state_at_event,
             None, // TODO: third party invite
         )
@@ -787,10 +745,34 @@ pub async fn send_transaction_message_route<'a>(
             );
             continue;
         }
-        // End of step 5.
+        // 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,
+            single_prev.clone(),
+            &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()),
+            );
+        };
 
         // Gather the forward extremities and resolve
-        let fork_states = match forward_extremity_ids(
+        let fork_states = match forward_extremities(
             &db,
             &pdu,
             server_name,
@@ -806,7 +788,9 @@ pub async fn send_transaction_message_route<'a>(
             }
         };
 
-        // Step 6. event passes auth based on state of all forks and current room state
+        // 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()
@@ -852,6 +836,7 @@ pub async fn send_transaction_message_route<'a>(
             }
             info!("{} event's were not in the auth_cache", number_fetches);
 
+            let mut event_map = EventMap::new();
             // Add everything we will need to event_map
             event_map.extend(
                 auth_events
@@ -904,7 +889,7 @@ pub async fn send_transaction_message_route<'a>(
         if !state_res::event_auth::auth_check(
             &RoomVersionId::Version6,
             &pdu,
-            previous,
+            single_prev,
             &state_at_forks,
             None,
         )
@@ -925,14 +910,19 @@ pub async fn send_transaction_message_route<'a>(
     Ok(dbg!(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. Passes signature checks, otherwise event is dropped.
-/// 3. Passes hash checks, otherwise it is redacted before being processed further.
-/// 4. Passes auth_chain collection (we can gather the events that auth this event recursively).
-/// 5. Once the event has passed all checks it can be added as an outlier to the DB.
+/// 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
 fn validate_event<'a>(
     db: &'a Database,
     value: CanonicalJsonObject,
@@ -940,9 +930,24 @@ fn validate_event<'a>(
     pub_key_map: &'a PublicKeyMap,
     origin: &'a ServerName,
     auth_cache: &'a mut EventMap<Arc<PduEvent>>,
-) -> Pin<Box<dyn Future<Output = StdResult<PduEvent, String>> + 'a + Send>> {
+) -> AsyncRecursiveResult<'a, (Arc<PduEvent>, Vec<Arc<PduEvent>>)> {
     Box::pin(async move {
-        let mut val = signature_and_hash_check(&pub_key_map, value)?;
+        let mut val =
+            match ruma::signatures::verify_event(pub_key_map, &value, &RoomVersionId::Version6) {
+                Ok(ver) => {
+                    if let ruma::signatures::Verified::Signatures = ver {
+                        match ruma::signatures::redact(&value, &RoomVersionId::Version6) {
+                            Ok(obj) => obj,
+                            Err(_) => return Err("Redaction failed".to_string()),
+                        }
+                    } else {
+                        value
+                    }
+                }
+                Err(_e) => {
+                    return Err("Signature verification failed".to_string());
+                }
+            };
 
         // Now that we have checked the signature and hashes we can add the eventID and convert
         // to our PduEvent type also finally verifying the first step listed above
@@ -959,11 +964,42 @@ fn validate_event<'a>(
             .await
             .map_err(|_| "Event failed auth chain check".to_string())?;
 
-        db.rooms
-            .append_pdu_outlier(pdu.event_id(), &pdu)
+        let pdu = Arc::new(pdu.clone());
+
+        // 8. fetch any missing prev events doing all checks listed here starting at 1. These are timeline events
+        let previous = fetch_events(&db, origin, &pub_key_map, &pdu.prev_events, auth_cache)
+            .await
             .map_err(|e| e.to_string())?;
 
-        Ok(pdu)
+        // Check that the event passes auth based on the auth_events
+        let is_authed = state_res::event_auth::auth_check(
+            &RoomVersionId::Version6,
+            &pdu,
+            if previous.len() == 1 {
+                previous.first().cloned()
+            } else {
+                None
+            },
+            &pdu.auth_events
+                .iter()
+                .map(|id| {
+                    auth_cache
+                        .get(id)
+                        .map(|pdu| ((pdu.kind(), pdu.state_key()), pdu.clone()))
+                        .ok_or_else(|| {
+                            "Auth event not found, event failed recursive auth checks.".to_string()
+                        })
+                })
+                .collect::<StdResult<BTreeMap<_, _>, _>>()?,
+            None, // TODO: third party invite
+        )
+        .map_err(|_e| "Auth check failed".to_string())?;
+
+        if !is_authed {
+            return Err("Event has failed auth check with auth events".to_string());
+        }
+
+        Ok((pdu, previous))
     })
 }
 
@@ -990,7 +1026,10 @@ async fn fetch_check_auth_events(
 
         let ev = fetch_events(db, origin, key_map, &[ev_id.clone()], auth_cache)
             .await
-            .map(|mut vec| vec.remove(0))?;
+            .map(|mut vec| {
+                vec.pop()
+                    .ok_or_else(|| Error::Conflict("Event was not found in fetch_events"))
+            })??;
 
         stack.extend(ev.auth_events());
         auth_cache.insert(ev.event_id().clone(), ev);
@@ -1028,11 +1067,12 @@ async fn fetch_events(
                 {
                     Ok(res) => {
                         let (event_id, value) = crate::pdu::gen_event_id_canonical_json(&res.pdu);
-                        let pdu = validate_event(db, value, event_id, key_map, origin, auth_cache)
-                            .await
-                            .map_err(|_| Error::Conflict("Authentication of event failed"))?;
+                        let (pdu, _) =
+                            validate_event(db, value, event_id, key_map, origin, auth_cache)
+                                .await
+                                .map_err(|_| Error::Conflict("Authentication of event failed"))?;
 
-                        Arc::new(pdu)
+                        pdu
                     }
                     Err(_) => return Err(Error::BadServerResponse("Failed to fetch event")),
                 },
@@ -1063,31 +1103,11 @@ async fn fetch_signing_keys(
     }
 }
 
-fn signature_and_hash_check(
-    pub_key_map: &ruma::signatures::PublicKeyMap,
-    value: CanonicalJsonObject,
-) -> std::result::Result<CanonicalJsonObject, String> {
-    Ok(
-        match ruma::signatures::verify_event(pub_key_map, &value, &RoomVersionId::Version6) {
-            Ok(ver) => {
-                if let ruma::signatures::Verified::Signatures = ver {
-                    error!("CONTENT HASH FAILED");
-                    match ruma::signatures::redact(&value, &RoomVersionId::Version6) {
-                        Ok(obj) => obj,
-                        Err(_) => return Err("Redaction failed".to_string()),
-                    }
-                } else {
-                    value
-                }
-            }
-            Err(_e) => {
-                return Err("Signature verification failed".to_string());
-            }
-        },
-    )
-}
-
-async fn forward_extremity_ids(
+/// Gather all state snapshots needed to resolve the current state of the room.
+///
+/// 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)
+async fn forward_extremities(
     db: &Database,
     pdu: &PduEvent,
     origin: &ServerName,
@@ -1102,6 +1122,8 @@ async fn forward_extremity_ids(
         }
     }
 
+    let current_hash = db.rooms.current_state_hash(pdu.room_id())?;
+    let mut includes_current_state = false;
     let mut fork_states = vec![];
     for id in &current_leaves {
         if let Some(id) = db.rooms.get_pdu_id(id)? {
@@ -1109,6 +1131,10 @@ async fn forward_extremity_ids(
                 .rooms
                 .pdu_state_hash(&id)?
                 .expect("found pdu with no statehash");
+
+            if current_hash.as_ref() == Some(&state_hash) {
+                includes_current_state = true;
+            }
             let state = db
                 .rooms
                 .state_full(&pdu.room_id, &state_hash)?
@@ -1144,6 +1170,17 @@ async fn forward_extremity_ids(
         }
     }
 
+    // This guarantees that our current room state is included
+    if !includes_current_state && current_hash.is_some() {
+        fork_states.push(
+            db.rooms
+                .state_full(pdu.room_id(), current_hash.as_ref().unwrap())?
+                .into_iter()
+                .map(|(k, v)| ((k.0, Some(k.1)), Arc::new(v)))
+                .collect(),
+        )
+    }
+
     Ok(fork_states)
 }