Move the incoming hash filtering logic into sql.js to prevent data races

app/sql.js

@@ -1534,18 +1534,22 @@ async function saveMessage(data, { forceSave } = {}) {
   return toCreate.id;
 }
 
-async function saveSeenMessageHashes(arrayOfHashes) {
+async function saveSeenMessageHashes(incomingHashes) {
   let promise;
+  const hashList = incomingHashes.map(h => h.hash);
+  const dupHashes = await getSeenMessagesByHashList(hashList);
+  const newHashes = incomingHashes.filter(h => !dupHashes.includes(h.hash));
 
   db.serialize(() => {
     promise = Promise.all([
       db.run('BEGIN TRANSACTION;'),
-      ...map(arrayOfHashes, hashData => saveSeenMessageHash(hashData)),
+      ...map(newHashes, hashData => saveSeenMessageHash(hashData)),
       db.run('COMMIT TRANSACTION;'),
     ]);
   });
 
   await promise;
+  return newHashes;
 }
 
 async function saveSeenMessageHash(data) {

js/modules/data.js

@@ -788,7 +788,7 @@ async function cleanSeenMessages() {
 }
 
 async function saveSeenMessageHashes(data) {
-  await channels.saveSeenMessageHashes(_cleanData(data));
+  return channels.saveSeenMessageHashes(_cleanData(data));
 }
 
 async function saveSeenMessageHash(data) {

libtextsecure/http-resources.js

@@ -45,16 +45,13 @@
   const filterIncomingMessages = async function filterIncomingMessages(
     messages
   ) {
-    const incomingHashes = messages.map(m => m.hash);
-    const dupHashes = await window.Signal.Data.getSeenMessagesByHashList(
-      incomingHashes
-    );
-    const newMessages = messages.filter(m => !dupHashes.includes(m.hash));
-    const newHashes = newMessages.map(m => ({
+    const incomingHashes = messages.map(m => ({
       expiresAt: m.expiration,
       hash: m.hash,
     }));
-    await window.Signal.Data.saveSeenMessageHashes(newHashes);
+    let newHashes = await window.Signal.Data.saveSeenMessageHashes(incomingHashes);
+    newHashes = newHashes.map(h => h.hash);
+    const newMessages = messages.filter(m => newHashes.includes(m.hash));
     return newMessages;
   };