Use non-deprecated method of re-processing MatrixRTCSession keys (#2646)

* Handle case of encryption key for an index to be undefined

As per https://github.com/matrix-org/matrix-js-sdk/pull/4423 the key can be undefined and so we should handle this rather than waiting for SubtleCrypto.importKey() to fail.

* Use release version of matrix-js-sdk

Diff is baa6d13506...v34.7.0

* Use RTCSession. reemitEncryptionKeys()

* Add some test coverage whilst we are here

* Add some test coverage whilst we are here

* Lint

src/e2ee/matrixKeyProvider.test.ts

@@ -0,0 +1,72 @@
+/*
+Copyright 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only
+Please see LICENSE in the repository root for full details.
+*/
+
+import { describe, expect, test, vi } from "vitest";
+import {
+  MatrixRTCSession,
+  MatrixRTCSessionEvent,
+} from "matrix-js-sdk/src/matrixrtc";
+import { KeyProviderEvent } from "livekit-client";
+
+import { MatrixKeyProvider } from "./matrixKeyProvider";
+
+function mockRTCSession(): MatrixRTCSession {
+  return {
+    on: vi.fn(),
+    off: vi.fn(),
+    reemitEncryptionKeys: vi.fn(),
+  } as unknown as MatrixRTCSession;
+}
+
+describe("matrixKeyProvider", () => {
+  test("initializes", () => {
+    const keyProvider = new MatrixKeyProvider();
+    expect(keyProvider).toBeTruthy();
+  });
+
+  test("listens for key requests and emits existing keys", () => {
+    const keyProvider = new MatrixKeyProvider();
+
+    const session = mockRTCSession();
+
+    keyProvider.setRTCSession(session);
+
+    expect(session.on).toHaveBeenCalledWith(
+      MatrixRTCSessionEvent.EncryptionKeyChanged,
+      expect.any(Function),
+    );
+    expect(session.off).not.toHaveBeenCalled();
+  });
+
+  test("stops listening when session changes", () => {
+    const keyProvider = new MatrixKeyProvider();
+
+    const session1 = mockRTCSession();
+    const session2 = mockRTCSession();
+
+    keyProvider.setRTCSession(session1);
+    expect(session1.off).not.toHaveBeenCalled();
+
+    keyProvider.setRTCSession(session2);
+    expect(session1.off).toHaveBeenCalledWith(
+      MatrixRTCSessionEvent.EncryptionKeyChanged,
+      expect.any(Function),
+    );
+  });
+
+  test("emits existing keys", () => {
+    const keyProvider = new MatrixKeyProvider();
+    const setKeyListener = vi.fn();
+    keyProvider.on(KeyProviderEvent.SetKey, setKeyListener);
+
+    const session = mockRTCSession();
+
+    keyProvider.setRTCSession(session);
+
+    expect(session.reemitEncryptionKeys).toHaveBeenCalled();
+  });
+});

src/e2ee/matrixKeyProvider.ts

@@ -35,15 +35,8 @@ export class MatrixKeyProvider extends BaseKeyProvider {
     );
 
     // The new session could be aware of keys of which the old session wasn't,
-    // so emit a key changed event.
-    for (const [
-      participant,
-      encryptionKeys,
-    ] of this.rtcSession.getEncryptionKeys()) {
-      for (const [index, encryptionKey] of encryptionKeys.entries()) {
-        this.onEncryptionKeyChanged(encryptionKey, index, participant);
-      }
-    }
+    // so emit key changed events
+    this.rtcSession.reemitEncryptionKeys();
   }
 
   private onEncryptionKeyChanged = (