Element-R: pass pickleKey in as raw key for indexeddb encryption

Currently, we pass the `pickleKey` to the rust library for use as a passphrase
for encrypting its crypto store. The Rust libary then passes that passphrase
through 200000 rounds of PBKDF2 to generate an encryption key, which is
(deliberately) slow.

However, the pickleKey is actually 32 bytes of random data (base64-encoded). By
passing the raw key into the rust library, we can therefore save the PBKDF
operation.

Backwards-compatibility with existing sessions is maintained, because if the
rust library discovers that the store was previously encrypted with a key based
on a PBKDF, it will re-base64 and PBKDF the key we provide, thus reconstructing
the right key.

src/Lifecycle.ts

@@ -18,12 +18,12 @@ limitations under the License.
 */
 
 import { ReactNode } from "react";
-import { createClient, MatrixClient, SSOAction, OidcTokenRefresher } from "matrix-js-sdk/src/matrix";
+import { createClient, MatrixClient, SSOAction, OidcTokenRefresher, decodeBase64 } from "matrix-js-sdk/src/matrix";
 import { IEncryptedPayload } from "matrix-js-sdk/src/crypto/aes";
 import { QueryDict } from "matrix-js-sdk/src/utils";
 import { logger } from "matrix-js-sdk/src/logger";
 
-import { IMatrixClientCreds, MatrixClientPeg } from "./MatrixClientPeg";
+import { IMatrixClientCreds, MatrixClientPeg, MatrixClientPegAssignOpts } from "./MatrixClientPeg";
 import { ModuleRunner } from "./modules/ModuleRunner";
 import EventIndexPeg from "./indexing/EventIndexPeg";
 import createMatrixClient from "./utils/createMatrixClient";
@@ -422,6 +422,7 @@ async function onSuccessfulDelegatedAuthLogin(credentials: IMatrixClientCreds):
 }
 
 type TryAgainFunction = () => void;
+
 /**
  * Display a friendly error to the user when token login or OIDC authorization fails
  * @param description error description
@@ -821,7 +822,23 @@ async function doSetLoggedIn(credentials: IMatrixClientCreds, clearStorageEnable
     checkSessionLock();
 
     dis.fire(Action.OnLoggedIn);
-    await startMatrixClient(client, /*startSyncing=*/ !softLogout);
+
+    const clientPegOpts: MatrixClientPegAssignOpts = {};
+    if (credentials.pickleKey) {
+        // The pickleKey, if provided, is probably a base64-encoded 256-bit key, so can be used for the crypto store.
+        if (credentials.pickleKey.length == 43) {
+            clientPegOpts.rustCryptoStoreKey = decodeBase64(credentials.pickleKey);
+        } else {
+            // We have some legacy pickle key. Continue using it as a password.
+            clientPegOpts.rustCryptoStorePassword = credentials.pickleKey;
+        }
+    }
+
+    try {
+        await startMatrixClient(client, /*startSyncing=*/ !softLogout, clientPegOpts);
+    } finally {
+        clientPegOpts.rustCryptoStoreKey?.fill(0);
+    }
 
     return client;
 }
@@ -955,11 +972,16 @@ export function isLoggingOut(): boolean {
 /**
  * Starts the matrix client and all other react-sdk services that
  * listen for events while a session is logged in.
+ *
  * @param client the matrix client to start
- * @param {boolean} startSyncing True (default) to actually start
- * syncing the client.
+ * @param startSyncing - `true` to actually start syncing the client.
+ * @param clientPegOpts - Options to pass through to {@link MatrixClientPeg.start}.
  */
-async function startMatrixClient(client: MatrixClient, startSyncing = true): Promise<void> {
+async function startMatrixClient(
+    client: MatrixClient,
+    startSyncing: boolean,
+    clientPegOpts: MatrixClientPegAssignOpts,
+): Promise<void> {
     logger.log(`Lifecycle: Starting MatrixClient`);
 
     // dispatch this before starting the matrix client: it's used
@@ -990,10 +1012,10 @@ async function startMatrixClient(client: MatrixClient, startSyncing = true): Pro
         // index (e.g. the FilePanel), therefore initialize the event index
         // before the client.
         await EventIndexPeg.init();
-        await MatrixClientPeg.start();
+        await MatrixClientPeg.start(clientPegOpts);
     } else {
         logger.warn("Caller requested only auxiliary services be started");
-        await MatrixClientPeg.assign();
+        await MatrixClientPeg.assign(clientPegOpts);
     }
 
     checkSessionLock();

src/MatrixClientPeg.ts

@@ -66,6 +66,27 @@ export interface IMatrixClientCreds {
     freshLogin?: boolean;
 }
 
+export interface MatrixClientPegAssignOpts {
+    /**
+     * If we are using Rust crypto, a key with which to encrypt the indexeddb.
+     *
+     * If provided, it must be exactly 32 bytes of data. If both this and
+     * {@link MatrixClientPegAssignOpts.rustCryptoStorePassword} are undefined,
+     * the store will be unencrypted.
+     */
+    rustCryptoStoreKey?: Uint8Array;
+
+    /**
+     * If we are using Rust crypto, a password which will be used to derive a key to encrypt the store with.
+     *
+     * An alternative to {@link MatrixClientPegAssignOpts.rustCryptoStoreKey}. Ignored if `rustCryptoStoreKey` is set.
+     *
+     * Deriving a key from a password is (deliberately) a slow operation, so prefer to pass a `rustCryptoStoreKey`
+     * directly where possible.
+     */
+    rustCryptoStorePassword?: string;
+}
+
 /**
  * Holds the current instance of the `MatrixClient` to use across the codebase.
  * Looking for an `MatrixClient`? Just look for the `MatrixClientPeg` on the peg
@@ -103,14 +124,14 @@ export interface IMatrixClientPeg {
     unset(): void;
 
     /**
-     * Prepare the MatrixClient for use, including initialising the store and crypto, but do not start it
+     * Prepare the MatrixClient for use, including initialising the store and crypto, but do not start it.
      */
-    assign(): Promise<IStartClientOpts>;
+    assign(opts?: MatrixClientPegAssignOpts): Promise<IStartClientOpts>;
 
     /**
-     * Prepare the MatrixClient for use, including initialising the store and crypto, and start it
+     * Prepare the MatrixClient for use, including initialising the store and crypto, and start it.
      */
-    start(): Promise<void>;
+    start(opts?: MatrixClientPegAssignOpts): Promise<void>;
 
     /**
      * If we've registered a user ID we set this to the ID of the
@@ -257,7 +278,10 @@ class MatrixClientPegClass implements IMatrixClientPeg {
         PlatformPeg.get()?.reload();
     };
 
-    public async assign(): Promise<IStartClientOpts> {
+    /**
+     * Implementation of {@link IMatrixClientPeg.assign}.
+     */
+    public async assign(assignOpts: MatrixClientPegAssignOpts = {}): Promise<IStartClientOpts> {
         if (!this.matrixClient) {
             throw new Error("createClient must be called first");
         }
@@ -284,7 +308,7 @@ class MatrixClientPegClass implements IMatrixClientPeg {
 
         // try to initialise e2e on the new client
         if (!SettingsStore.getValue("lowBandwidth")) {
-            await this.initClientCrypto();
+            await this.initClientCrypto(assignOpts.rustCryptoStoreKey, assignOpts.rustCryptoStorePassword);
         }
 
         const opts = utils.deepCopy(this.opts);
@@ -310,8 +334,16 @@ class MatrixClientPegClass implements IMatrixClientPeg {
 
     /**
      * Attempt to initialize the crypto layer on a newly-created MatrixClient
+     *
+     * @param rustCryptoStoreKey - If we are using Rust crypto, a key with which to encrypt the indexeddb.
+     *   If provided, it must be exactly 32 bytes of data. If both this and `rustCryptoStorePassword` are
+     *   undefined, the store will be unencrypted.
+     *
+     * @param rustCryptoStorePassword - An alternative to `rustCryptoStoreKey`. Ignored if `rustCryptoStoreKey` is set.
+     *    A password which will be used to derive a key to encrypt the store with. Deriving a key from a password is
+     *    (deliberately) a slow operation, so prefer to pass a `rustCryptoStoreKey` directly where possible.
      */
-    private async initClientCrypto(): Promise<void> {
+    private async initClientCrypto(rustCryptoStoreKey?: Uint8Array, rustCryptoStorePassword?: string): Promise<void> {
         if (!this.matrixClient) {
             throw new Error("createClient must be called first");
         }
@@ -347,7 +379,13 @@ class MatrixClientPegClass implements IMatrixClientPeg {
 
         // Now we can initialise the right crypto impl.
         if (useRustCrypto) {
-            await this.matrixClient.initRustCrypto();
+            if (!rustCryptoStoreKey && !rustCryptoStorePassword) {
+                logger.error("Warning! Not using an encryption key for rust crypto store.");
+            }
+            await this.matrixClient.initRustCrypto({
+                storageKey: rustCryptoStoreKey,
+                storagePassword: rustCryptoStorePassword,
+            });
 
             StorageManager.setCryptoInitialised(true);
             // TODO: device dehydration and whathaveyou
@@ -376,8 +414,11 @@ class MatrixClientPegClass implements IMatrixClientPeg {
         }
     }
 
-    public async start(): Promise<void> {
-        const opts = await this.assign();
+    /**
+     * Implementation of {@link IMatrixClientPeg.start}.
+     */
+    public async start(assignOpts?: MatrixClientPegAssignOpts): Promise<void> {
+        const opts = await this.assign(assignOpts);
 
         logger.log(`MatrixClientPeg: really starting MatrixClient`);
         await this.matrixClient!.startClient(opts);

test/MatrixClientPeg-test.ts

@@ -217,7 +217,7 @@ describe("MatrixClientPeg", () => {
                 testPeg.safeGet().store.on = emitter.on.bind(emitter);
                 const platform: any = { reload: jest.fn() };
                 PlatformPeg.set(platform);
-                await testPeg.assign();
+                await testPeg.assign({});
                 emitter.emit("closed" as any);
                 expect(platform.reload).toHaveBeenCalled();
             });
@@ -229,7 +229,7 @@ describe("MatrixClientPeg", () => {
                 PlatformPeg.set(platform);
                 testPeg.safeGet().store.on = emitter.on.bind(emitter);
                 const spy = jest.spyOn(Modal, "createDialog");
-                await testPeg.assign();
+                await testPeg.assign({});
                 emitter.emit("closed" as any);
                 expect(spy).toHaveBeenCalled();
             });
@@ -243,9 +243,10 @@ describe("MatrixClientPeg", () => {
             const mockInitCrypto = jest.spyOn(testPeg.safeGet(), "initCrypto").mockResolvedValue(undefined);
             const mockInitRustCrypto = jest.spyOn(testPeg.safeGet(), "initRustCrypto").mockResolvedValue(undefined);
 
-            await testPeg.start();
+            const cryptoStoreKey = new Uint8Array([1, 2, 3, 4]);
+            await testPeg.start(cryptoStoreKey);
             expect(mockInitCrypto).not.toHaveBeenCalled();
-            expect(mockInitRustCrypto).toHaveBeenCalledTimes(1);
+            expect(mockInitRustCrypto).toHaveBeenCalledWith({ storageKey: cryptoStoreKey });
 
             // we should have stashed the setting in the settings store
             expect(mockSetValue).toHaveBeenCalledWith("feature_rust_crypto", null, SettingLevel.DEVICE, true);
@@ -271,7 +272,7 @@ describe("MatrixClientPeg", () => {
 
             await testPeg.start();
             expect(mockInitCrypto).toHaveBeenCalled();
-            expect(mockInitRustCrypto).not.toHaveBeenCalledTimes(1);
+            expect(mockInitRustCrypto).not.toHaveBeenCalled();
 
             // we should have stashed the setting in the settings store
             expect(mockSetValue).toHaveBeenCalledWith("feature_rust_crypto", null, SettingLevel.DEVICE, false);