Check account data type match before storing to DB

src/database/key_value/account_data.rs

@@ -3,6 +3,7 @@ use std::collections::HashMap;
 use ruma::{api::client::error::ErrorKind, RoomId, UserId};
 use serde::Deserialize;
 use serde_json::value::RawValue;
+use tracing::error;
 
 use crate::{
     database::KeyValueDatabase, service, services, utils, Error, Result,
@@ -16,16 +17,6 @@ impl service::account_data::Data for KeyValueDatabase {
         event_type: &str,
         data: &RawValue,
     ) -> Result<()> {
-        // Allowed because we just use this type to validate the schema, and
-        // don't read the fields.
-        #[allow(dead_code)]
-        #[derive(Deserialize)]
-        struct ExtractEventFields<'a> {
-            #[serde(rename = "type")]
-            event_type: &'a str,
-            content: &'a RawValue,
-        }
-
         let mut prefix = room_id
             .map(ToString::to_string)
             .unwrap_or_default()
@@ -44,11 +35,41 @@ impl service::account_data::Data for KeyValueDatabase {
         let mut key = prefix;
         key.extend_from_slice(event_type.as_bytes());
 
-        if serde_json::from_str::<ExtractEventFields<'_>>(data.get()).is_err() {
+        {
-            return Err(Error::BadRequest(
+            #[derive(Deserialize)]
-                ErrorKind::InvalidParam,
+            struct ExtractEventFields<'a> {
-                "Account data doesn't have all required fields.",
+                #[serde(rename = "type")]
-            ));
+                event_type: &'a str,
+                // Allowed because we just use this type to validate the schema
+                // and event type, and don't extract the content.
+                #[allow(dead_code)]
+                content: &'a RawValue,
+            }
+
+            let Ok(ExtractEventFields {
+                event_type: serialised_event_type,
+                ..
+            }) = serde_json::from_str(data.get())
+            else {
+                return Err(Error::BadRequest(
+                    ErrorKind::InvalidParam,
+                    "Account data doesn't have all required fields.",
+                ));
+            };
+
+            if serialised_event_type != event_type {
+                error!(
+                    %user_id,
+                    ?room_id,
+                    event_type,
+                    serialised_event_type,
+                    "Mismatch between discrete and serialised account data event type"
+                );
+                return Err(Error::BadRequest(
+                    ErrorKind::InvalidParam,
+                    "Account data event type mismatch.",
+                ));
+            }
         }
 
         self.roomuserdataid_accountdata