From f58bd1e498c39ed1c9f625d71753bbcdd26c7300 Mon Sep 17 00:00:00 2001
From: David Baker <dave@matrix.org>
Date: Mon, 4 Jul 2022 20:05:25 +0100
Subject: [PATCH] Add config option for e2e group call signalling

---
 src/client.ts      | 19 +++++++++++++++++++
 src/webrtc/call.ts | 36 +++++++++++++++++++++++-------------
 2 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/src/client.ts b/src/client.ts
index 32e05e97260..3deed4e9262 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -346,6 +346,12 @@ export interface ICreateClientOpts {
      */
     fallbackICEServerAllowed?: boolean;
 
+    /**
+     * If true, to-device signalling for group calls will be encrypted
+     * with Olm. Default: true.
+     */
+    useE2eForGroupCall?: boolean;
+
     cryptoCallbacks?: ICryptoCallbacks;
 }
 
@@ -954,6 +960,8 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
     protected sessionId: string;
     protected pendingEventEncryption = new Map<string, Promise<void>>();
 
+    private useE2eForGroupCall = true;
+
     constructor(opts: IMatrixClientCreateOpts) {
         super();
 
@@ -1044,6 +1052,8 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         this.supportsCallTransfer = opts.supportsCallTransfer || false;
         this.fallbackICEServerAllowed = opts.fallbackICEServerAllowed || false;
 
+        if (opts.useE2eForGroupCall !== undefined) this.useE2eForGroupCall = opts.useE2eForGroupCall;
+
         // List of which rooms have encryption enabled: separate from crypto because
         // we still want to know which rooms are encrypted even if crypto is disabled:
         // we don't want to start sending unencrypted events to them.
@@ -1499,6 +1509,15 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         this.supportsCallTransfer = support;
     }
 
+    /**
+     * Returns true if to-device signalling for group calls will be encrypted with Olm.
+     * If false, it will be sent unencrypted.
+     * @returns boolean Whether group call signalling will be encrypted
+     */
+    public getUseE2eForGroupCall(): boolean {
+        return this.useE2eForGroupCall;
+    }
+
     /**
      * Creates a new call.
      * The place*Call methods on the returned call can be used to actually place a call
diff --git a/src/webrtc/call.ts b/src/webrtc/call.ts
index b79b9c62157..f56d5342fdc 100644
--- a/src/webrtc/call.ts
+++ b/src/webrtc/call.ts
@@ -525,6 +525,7 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
 
     private async initOpponentCrypto() {
         if (!this.opponentDeviceId) return;
+        if (!this.client.getUseE2eForGroupCall()) return;
 
         const userId = this.invitee || this.getOpponentMember().userId;
         const deviceInfoMap = await this.client.crypto.deviceList.downloadKeys([userId], false);
@@ -2144,21 +2145,30 @@ export class MatrixCall extends TypedEventEmitter<CallEvent, CallEventHandlerMap
                 },
             });
 
-            const payload = {
-                type: eventType,
-                content: {
-                    ...realContent,
-                    device_id: this.client.deviceId,
-                    sender_session_id: this.client.getSessionId(),
-                    dest_session_id: this.opponentSessionId,
-                    seq: toDeviceSeq,
-                },
+            const content = {
+                ...realContent,
+                device_id: this.client.deviceId,
+                sender_session_id: this.client.getSessionId(),
+                dest_session_id: this.opponentSessionId,
+                seq: toDeviceSeq,
             };
+
             const userId = this.invitee || this.getOpponentMember().userId;
-            return this.client.crypto.encryptAndSendToDevices([{
-                userId,
-                deviceInfo: this.opponentDeviceInfo,
-            }], payload);
+            if (this.client.getUseE2eForGroupCall()) {
+                return this.client.crypto.encryptAndSendToDevices([{
+                    userId,
+                    deviceInfo: this.opponentDeviceInfo,
+                }], {
+                    type: eventType,
+                    content,
+                });
+            } else {
+                return this.client.sendToDevice(eventType, {
+                    [userId]: {
+                        [this.opponentDeviceId]: content,
+                    },
+                });
+            }
         } else {
             this.emit(CallEvent.SendVoipEvent, {
                 type: "sendEvent",