Fix loading 'invalid' event from the database (#19816)

Follow on from #19701.

Some Synapse servers may have events in their database that don't pass
the canonical JSON checks. This is bad, but we still want to be able to
load them nonetheless.

changelog.d/19816.misc

@@ -0,0 +1 @@
+Port the python Event classes to Rust.

rust/src/events/utils.rs

@@ -75,15 +75,14 @@ pub fn compute_event_reference_hash(
     redacted_value_mut.remove(UNSIGNED);
     redacted_value_mut.remove(AGE_TS);
 
-    let canonicalization_options = if room_version.strict_canonicaljson {
-        CanonicalizationOptions::strict()
-    } else {
-        CanonicalizationOptions::relaxed()
-    };
-
-    let json =
-        crate::canonical_json::to_string_canonical(&redacted_value_mut, canonicalization_options)
-            .map_err(|err| anyhow::anyhow!(err))?;
+    // We use `CanonicalizationOptions::relaxed()` as we have some events that
+    // have already been accepted with int fields outside the valid range. We
+    // still want to be able to load them and calculate their event ID.
+    let json = crate::canonical_json::to_string_canonical(
+        &redacted_value_mut,
+        CanonicalizationOptions::relaxed(),
+    )
+    .map_err(|err| anyhow::anyhow!(err))?;
 
     let hash = Sha256::digest(json.as_bytes());
 

synapse/storage/databases/main/events_worker.py

@@ -1523,8 +1523,8 @@ class EventsWorkerStore(SQLBaseStore):
                     internal_metadata_dict=internal_metadata,
                     rejected_reason=rejected_reason,
                 )
-            except SynapseError:
-                logger.error("Unable to parse event from database: %s", event_id)
+            except SynapseError as e:
+                logger.error("Unable to parse event from database %s: %s", event_id, e)
                 continue
 
             original_ev.internal_metadata.stream_ordering = row.stream_ordering