also write room key that we create ourselves with RoomKey infrastructure

so all keys are written in one place and the flags are always correct

src/matrix/e2ee/megolm/Encryption.js

@@ -15,12 +15,14 @@ limitations under the License.
 */
 
 import {MEGOLM_ALGORITHM} from "../common.js";
+import {OutboundRoomKey} from "./decryption/RoomKey";
 
 export class Encryption {
-    constructor({pickleKey, olm, account, storage, now, ownDeviceId}) {
+    constructor({pickleKey, olm, account, keyLoader, storage, now, ownDeviceId}) {
         this._pickleKey = pickleKey;
         this._olm = olm;
         this._account = account;
+        this._keyLoader = keyLoader;
         this._storage = storage;
         this._now = now;
         this._ownDeviceId = ownDeviceId;
@@ -64,7 +66,7 @@ export class Encryption {
             let roomKeyMessage;
             try {
                 let sessionEntry = await txn.outboundGroupSessions.get(roomId);
-                roomKeyMessage = this._readOrCreateSession(session, sessionEntry, roomId, encryptionParams, txn);
+                roomKeyMessage = await this._readOrCreateSession(session, sessionEntry, roomId, encryptionParams, txn);
                 if (roomKeyMessage) {
                     this._writeSession(this._now(), session, roomId, txn);
                 }
@@ -79,7 +81,7 @@ export class Encryption {
         }
     }
 
-    _readOrCreateSession(session, sessionEntry, roomId, encryptionParams, txn) {
+    async _readOrCreateSession(session, sessionEntry, roomId, encryptionParams, txn) {
         if (sessionEntry) {
             session.unpickle(this._pickleKey, sessionEntry.session);
         }
@@ -91,7 +93,8 @@ export class Encryption {
             }
             session.create();
             const roomKeyMessage = this._createRoomKeyMessage(session, roomId);
-            this._storeAsInboundSession(session, roomId, txn);
+            const roomKey = new OutboundRoomKey(roomId, session, this._account.identityKeys);
+            await roomKey.write(this._keyLoader, txn);
             return roomKeyMessage;
         }
     }
@@ -123,7 +126,7 @@ export class Encryption {
             let encryptedContent;
             try {
                 let sessionEntry = await txn.outboundGroupSessions.get(roomId);
-                roomKeyMessage = this._readOrCreateSession(session, sessionEntry, roomId, encryptionParams, txn);
+                roomKeyMessage = await this._readOrCreateSession(session, sessionEntry, roomId, encryptionParams, txn);
                 encryptedContent = this._encryptContent(roomId, session, type, content);
                 // update timestamp when a new session is created
                 const createdAt = roomKeyMessage ? this._now() : sessionEntry.createdAt;
@@ -190,26 +193,6 @@ export class Encryption {
             chain_index: session.message_index()
         }
     }
-
-    _storeAsInboundSession(outboundSession, roomId, txn) {
-        const {identityKeys} = this._account;
-        const claimedKeys = {ed25519: identityKeys.ed25519};
-        const session = new this._olm.InboundGroupSession();
-        try {
-            session.create(outboundSession.session_key());
-            const sessionEntry = {
-                roomId,
-                senderKey: identityKeys.curve25519,
-                sessionId: session.session_id(),
-                session: session.pickle(this._pickleKey),
-                claimedKeys,
-            };
-            txn.inboundGroupSessions.set(sessionEntry);
-            return sessionEntry;
-        } finally {
-            session.free();
-        }
-    }
 }
 
 /**

src/matrix/e2ee/megolm/decryption/RoomKey.ts

@@ -155,7 +155,38 @@ class DeviceMessageRoomKey extends IncomingRoomKey {
     loadInto(session) {
         session.create(this.serializationKey);
     }
+}
 
+// a room key we send out ourselves,
+// here adapted to write it as an incoming key
+// as we don't send it to ourself with a to_device msg
+export class OutboundRoomKey extends IncomingRoomKey {
+    private _sessionKey: string;
+
+    constructor(
+        private readonly _roomId: string,
+        private readonly outboundSession: Olm.OutboundGroupSession,
+        private readonly identityKeys: {[algo: string]: string}
+    ) {
+        super();
+        // this is a new key, so always better than what might be in storage, no need to check
+        this.isBetter = true;
+        // cache this, as it is used by key loader to find a matching key and
+        // this calls into WASM so is not just reading a prop
+        this._sessionKey = this.outboundSession.session_key();
+    }
+
+    get roomId(): string { return this._roomId; }
+    get senderKey(): string { return this.identityKeys.curve25519; }
+    get sessionId(): string { return this.outboundSession.session_id(); }
+    get claimedEd25519Key(): string { return this.identityKeys.ed25519; }
+    get serializationKey(): string { return this._sessionKey; }
+    get serializationType(): string { return "create"; }
+    protected get keySource(): KeySource { return KeySource.Outbound; }
+
+    loadInto(session: Olm.InboundGroupSession) {
+        session.create(this.serializationKey);
+    }
 }
 
 class BackupRoomKey extends IncomingRoomKey {

src/matrix/storage/idb/stores/InboundGroupSessionStore.ts

@@ -25,6 +25,7 @@ export enum BackupStatus {
 export enum KeySource {
     DeviceMessage = 1,
     Backup,
+    Outbound
 }
 
 export interface InboundGroupSessionEntry {