Calling `initRustCrypto` Causes TypeError

[thecoolwinter]

I'm writing an HTML page and want to enable e2ee. I've read and re-read the docs and some other implementations and I cannot figure out what I'm doing wrong here.

I've defined the following function to set up a matrix client, and initialize the rust crypto module. I haven't included either the store or cryptoStore parameters, as I don't have any legacy data to migrate.

export const initClient = async (session: Session): Promise<MatrixClient> => {
	console.log("Initializing matrix", session);

	const client = createClient({
		baseUrl: session.baseUrl,
		accessToken: session.accessToken,
		userId: session.userId,
		deviceId: session.deviceId,
		timelineSupport: true,
		useAuthorizationHeader: true,
		verificationMethods: ["m.sas.v1"],
	});

	await client.initRustCrypto(); // Throws type error, despite the lack of legacy data

	client.setMaxListeners(50);

	return client;
};

When initRustCrypto is called, it throws the following TypeError:

TypeError: Cannot read properties of undefined (reading 'getMigrationState')
     at _IndexedDBCryptoStore.getMigrationState 

It appears to be being thrown here, which is SUPER odd.

// node_modules/matrix-js-sdk/src/rust-crypto/libolm_migration.ts
  getMigrationState() {
    return this.backend.getMigrationState();
  }

Final thing that's happening is this only happens on a page reload, after successfully signing in and caching the session information. I've verified that I'm passing in the correct userId/deviceId/accessToken on the second sign in attempt.

Even if I pass a legacy crypto store it still hits the error!

	const cryptoStore = new IndexedDBCryptoStore(window.indexedDB, "crypto-store");

	const client = createClient({
		baseUrl: session.baseUrl,
		accessToken: session.accessToken,
		userId: session.userId,
		deviceId: session.deviceId,
		timelineSupport: true,
		cryptoStore: cryptoStore,
		useAuthorizationHeader: true,
		verificationMethods: ["m.sas.v1"],
	});

	await client.initRustCrypto(); // Still throws

[richvdh]

Hrm, right. I think there are two problems here.

The first is that createClient defaults to setting the (legacy) crypto store to IndexedDBCryptoStore when you instantiate matrix-js-sdk via its browser entry point. This is mentioned in https://matrix-org.github.io/matrix-js-sdk/interfaces/matrix.ICreateClientOpts.html#cryptostore, but it's not particularly obvious. Moreover, it doesn't really make sense nowadays: I don't think there's any need for createClient to create a legacy crypto store at all.

The second problem is that IndexedDBCryptoStore isn't being initialised properly, and this.backend isn't being set. I don't really know why not, to be honest. It's supposed to happen in IndexedDBCryptoStore.startup, which should be called fairly early by RustCrypto.initRustCrypto when a legacyCryptoStore is in use. The implementation of that method is so old that it predates the existence of async/await, and is consequently very hard to follow, but I can't see an obvious way for it to complete without setting this.backend. Have you checked the console logs?

One workaround that might work for you is to set cryptoStore: new MemoryCryptoStore() in the arguments to createClient.

[thecoolwinter]

I'm really not sure how it's getting to the failure state either, logs didn't seem to show anything and stepping through the code I wasn't able to pinpoint when IndexedDBCryptoStore.startup was being called with an undefined legacyCryptoStore (in all fairness I'm not the most used to web debugging at the moment so I probably missed something).

I'll take one more look at it and see if I can find it and make a pr.

One workaround that might work for you is to set cryptoStore: new MemoryCryptoStore() in the arguments to createClient.

That worked! Thank you so much!