Fix key format on the wire to be base64

src/matrix-utils.ts

@@ -28,6 +28,7 @@ import {
   GroupCallIntent,
   GroupCallType,
 } from "matrix-js-sdk/src/webrtc/groupCall";
+import { secureRandomBase64 } from "matrix-js-sdk/src/randomstring";
 
 import type { MatrixClient } from "matrix-js-sdk/src/client";
 import type { Room } from "matrix-js-sdk/src/models/room";
@@ -73,23 +74,6 @@ function waitForSync(client: MatrixClient): Promise<void> {
   });
 }
 
-function secureRandomString(entropyBytes: number): string {
-  const key = new Uint8Array(entropyBytes);
-  crypto.getRandomValues(key);
-  // encode to base64url as this value goes into URLs
-  // base64url is just base64 with thw two non-alphanum characters swapped out for
-  // ones that can be put in a URL without encoding. Browser JS has a native impl
-  // for base64 encoding but only a string (there isn't one that takes a UInt8Array
-  // yet) so just use the built-in one and convert, replace the chars and strip the
-  // padding from the end (otherwise we'd need to pull in another dependency).
-  return btoa(
-    key.reduce((acc, current) => acc + String.fromCharCode(current), ""),
-  )
-    .replace("+", "-")
-    .replace("/", "_")
-    .replace(/=*$/, "");
-}
-
 /**
  * Initialises and returns a new standalone Matrix Client.
  * If true is passed for the 'restore' parameter, a check will be made
@@ -363,7 +347,7 @@ export async function createRoom(
 
   let password;
   if (e2ee) {
-    password = secureRandomString(16);
+    password = secureRandomBase64(16);
     setLocalStorageItem(
       getRoomSharedKeyLocalStorageKey(result.room_id),
       password,