Enable key backup by default

When we set up cross signing, so the key backup key will be stored
locally along with the cross signing keys until the user sets up
recovery (4s). This will mean that a user can restore their backup
if they log in on a new device as long as they verify with the one
they registered on.

src/components/structures/auth/E2eSetup.tsx

@@ -11,7 +11,7 @@ import { MatrixClient } from "matrix-js-sdk/src/matrix";
 
 import AuthPage from "../../views/auth/AuthPage";
 import CompleteSecurityBody from "../../views/auth/CompleteSecurityBody";
-import CreateCrossSigningDialog from "../../views/dialogs/security/CreateCrossSigningDialog";
+import InitialCryptoSetup from "../../views/dialogs/security/InitialCryptoSetup";
 
 interface IProps {
     matrixClient: MatrixClient;
@@ -25,7 +25,7 @@ export default class E2eSetup extends React.Component<IProps> {
         return (
             <AuthPage>
                 <CompleteSecurityBody>
-                    <CreateCrossSigningDialog
+                    <InitialCryptoSetup
                         matrixClient={this.props.matrixClient}
                         onFinished={this.props.onFinished}
                         accountPassword={this.props.accountPassword}

src/components/views/dialogs/security/InitialCryptoSetup.tsx

@@ -25,14 +25,14 @@ interface Props {
 }
 
 /*
- * Walks the user through the process of creating a cross-signing keys. In most
- * cases, only a spinner is shown, but for more complex auth like SSO, the user
- * may need to complete some steps to proceed.
+ * Walks the user through the process of creating a cross-signing keys and setting
+ * up message key backup. In most cases, only a spinner is shown, but for more
+ * complex auth like SSO, the user may need to complete some steps to proceed.
  */
-const CreateCrossSigningDialog: React.FC<Props> = ({ matrixClient, accountPassword, tokenLogin, onFinished }) => {
+const InitialCryptoSetup: React.FC<Props> = ({ matrixClient, accountPassword, tokenLogin, onFinished }) => {
     const [error, setError] = useState(false);
 
-    const bootstrapCrossSigning = useCallback(async () => {
+    const doSetup = useCallback(async () => {
         const cryptoApi = matrixClient.getCrypto();
         if (!cryptoApi) return;
 
@@ -40,6 +40,12 @@ const CreateCrossSigningDialog: React.FC<Props> = ({ matrixClient, accountPasswo
 
         try {
             await createCrossSigning(matrixClient, tokenLogin, accountPassword);
+
+            const backupInfo = await matrixClient.getKeyBackupVersion();
+            if (backupInfo === null) {
+                await cryptoApi.resetKeyBackup();
+            }
+
             onFinished(true);
         } catch (e) {
             if (tokenLogin) {
@@ -58,8 +64,8 @@ const CreateCrossSigningDialog: React.FC<Props> = ({ matrixClient, accountPasswo
     }, [onFinished]);
 
     useEffect(() => {
-        bootstrapCrossSigning();
-    }, [bootstrapCrossSigning]);
+        doSetup();
+    }, [doSetup]);
 
     let content;
     if (error) {
@@ -69,7 +75,7 @@ const CreateCrossSigningDialog: React.FC<Props> = ({ matrixClient, accountPasswo
                 <div className="mx_Dialog_buttons">
                     <DialogButtons
                         primaryButton={_t("action|retry")}
-                        onPrimaryButtonClick={bootstrapCrossSigning}
+                        onPrimaryButtonClick={doSetup}
                         onCancel={onCancel}
                     />
                 </div>
@@ -96,4 +102,4 @@ const CreateCrossSigningDialog: React.FC<Props> = ({ matrixClient, accountPasswo
     );
 };
 
-export default CreateCrossSigningDialog;
+export default InitialCryptoSetup;