fetch and verify keys on olm call signalling message

src/matrix/DeviceMessageHandler.js

@@ -38,7 +38,6 @@ export class DeviceMessageHandler {
 
     async prepareSync(toDeviceEvents, lock, txn, log) {
         log.set("messageTypes", countBy(toDeviceEvents, e => e.type));
-        this._handleUnencryptedCallEvents(toDeviceEvents, log);
         const encryptedEvents = toDeviceEvents.filter(e => e.type === "m.room.encrypted");
         if (!this._olmDecryption) {
             log.log("can't decrypt, encryption not enabled", log.level.Warn);
@@ -54,20 +53,6 @@ export class DeviceMessageHandler {
             }
             const newRoomKeys = this._megolmDecryption.roomKeysFromDeviceMessages(olmDecryptChanges.results, log);
             
-            // const callMessages = olmDecryptChanges.results.filter(dr => this._callHandler.handlesDeviceMessageEventType(dr.event?.type));
-            // // load devices by sender key
-            // await Promise.all(callMessages.map(async dr => {
-            //     dr.setDevice(await this._getDevice(dr.senderCurve25519Key, txn));
-            // }));
-            // // TODO: pass this in the prep and run it in afterSync or afterSyncComplete (as callHandler can send events as well)?
-            // for (const dr of callMessages) {
-            //     if (dr.device) {
-            //         this._callHandler.handleDeviceMessage(dr.event, dr.device.userId, dr.device.deviceId, log);
-            //     } else {
-            //         console.error("could not deliver message because don't have device for sender key", dr.event);
-            //     }
-            // }
-            
             // TODO: somehow include rooms that received a call to_device message in the sync state?
             // or have updates flow through event emitter?
             // well, we don't really need to update the room other then when a call starts or stops
@@ -76,33 +61,42 @@ export class DeviceMessageHandler {
         }
     }
 
-    _handleUnencryptedCallEvents(toDeviceEvents, log) {
-        const callMessages = toDeviceEvents.filter(e => this._callHandler.handlesDeviceMessageEventType(e.type));
-        for (const event of callMessages) {
-            const userId = event.sender;
-            const deviceId = event.content.device_id;
-            this._callHandler.handleDeviceMessage(event, userId, deviceId, log);
-        }
-    }
-
     /** check that prep is not undefined before calling this */
     async writeSync(prep, txn) {
         // write olm changes
         prep.olmDecryptChanges.write(txn);
         const didWriteValues = await Promise.all(prep.newRoomKeys.map(key => this._megolmDecryption.writeRoomKey(key, txn)));
-        return didWriteValues.some(didWrite => !!didWrite);
+        const hasNewRoomKeys = didWriteValues.some(didWrite => !!didWrite);
+        return {
+            hasNewRoomKeys,
+            decryptionResults: prep.olmDecryptChanges.results
+        };
     }
 
-
-    async _getDevice(senderKey, txn) {
-        let device = this._senderDeviceCache.get(senderKey);
-        if (!device) {
-            device = await txn.deviceIdentities.getByCurve25519Key(senderKey);
-            if (device) {
-                this._senderDeviceCache.set(device);
-            }
+    async afterSyncCompleted(decryptionResults, deviceTracker, hsApi, log) {
+        // if we don't have a device, we need to fetch the device keys the message claims
+        // and check the keys, and we should only do network requests during
+        // sync processing in the afterSyncCompleted step.
+        const callMessages = decryptionResults.filter(dr => this._callHandler.handlesDeviceMessageEventType(dr.event?.type));
+        if (callMessages.length) {
+            await log.wrap("process call signalling messages", async log => {
+                for (const dr of callMessages) {
+                    // serialize device loading, so subsequent messages for the same device take advantage of the cache
+                    const device = await deviceTracker.deviceForId(dr.event.sender, dr.event.content.device_id, hsApi, log);
+                    dr.setDevice(device);
+                    if (dr.isVerified) {
+                        this._callHandler.handleDeviceMessage(dr.event, dr.userId, dr.deviceId, log);
+                    } else {
+                        log.log({
+                            l: "could not verify olm fingerprint key matches, ignoring",
+                            ed25519Key: dr.device.ed25519Key,
+                            claimedEd25519Key: dr.claimedEd25519Key,
+                            deviceId, userId,
+                        });
+                    }
+                }
+            });
         }
-        return device;
     }
 }
 

src/matrix/Session.js

@@ -685,7 +685,9 @@ export class Session {
     async writeSync(syncResponse, syncFilterId, preparation, txn, log) {
         const changes = {
             syncInfo: null,
-            e2eeAccountChanges: null
+            e2eeAccountChanges: null,
+            hasNewRoomKeys: false,
+            deviceMessageDecryptionResults: null,
         };
         const syncToken = syncResponse.next_batch;
         if (syncToken !== this.syncToken) {
@@ -706,7 +708,9 @@ export class Session {
         }
 
         if (preparation) {
-            changes.hasNewRoomKeys = await log.wrap("deviceMsgs", log => this._deviceMessageHandler.writeSync(preparation, txn, log));
+            const {hasNewRoomKeys, decryptionResults} = await log.wrap("deviceMsgs", log => this._deviceMessageHandler.writeSync(preparation, txn, log));
+            changes.hasNewRoomKeys = hasNewRoomKeys;
+            changes.deviceMessageDecryptionResults = decryptionResults;
         }
 
         // store account data
@@ -747,6 +751,9 @@ export class Session {
         if (changes.hasNewRoomKeys) {
             this._keyBackup.get()?.flush(log);
         }
+        if (changes.deviceMessageDecryptionResults) {
+            await this._deviceMessageHandler.afterSyncCompleted(changes.deviceMessageDecryptionResults, this._deviceTracker, this._hsApi, log);
+        }
     }
 
     _tryReplaceRoomBeingCreated(roomId, log) {

src/matrix/Sync.js

@@ -160,7 +160,7 @@ export class Sync {
         const isCatchupSync = this._status.get() === SyncStatus.CatchupSync;
         const sessionPromise = (async () => {
             try {
-                await log.wrap("session", log => this._session.afterSyncCompleted(sessionChanges, isCatchupSync, log), log.level.Detail);
+                await log.wrap("session", log => this._session.afterSyncCompleted(sessionChanges, isCatchupSync, log));
             } catch (err) {} // error is logged, but don't fail sessionPromise
         })();
 

src/matrix/e2ee/README.md

@@ -41,5 +41,8 @@ Runs before any room.prepareSync, so the new room keys can be passed to each roo
         - e2ee account
             - generate more otks if needed
             - upload new otks if needed or device keys if not uploaded before
+        - device message handler:
+            - fetch keys we don't know about yet for (call) to_device messages identity
+            - pass signalling messages to call handler
     - rooms
         - share new room keys if needed