feat: add two factor auth (#643)

Add two factor authentication for users who wish to enhance the security of their accounts.

packages/lib/server-only/2fa/get-backup-code.ts

@@ -0,0 +1,38 @@
+import { z } from 'zod';
+
+import { User } from '@documenso/prisma/client';
+
+import { DOCUMENSO_ENCRYPTION_KEY } from '../../constants/crypto';
+import { symmetricDecrypt } from '../../universal/crypto';
+
+interface GetBackupCodesOptions {
+  user: User;
+}
+
+const ZBackupCodeSchema = z.array(z.string());
+
+export const getBackupCodes = ({ user }: GetBackupCodesOptions) => {
+  const key = DOCUMENSO_ENCRYPTION_KEY;
+
+  if (!user.twoFactorEnabled) {
+    throw new Error('User has not enabled 2FA');
+  }
+
+  if (!user.twoFactorBackupCodes) {
+    throw new Error('User has no backup codes');
+  }
+
+  const secret = Buffer.from(symmetricDecrypt({ key, data: user.twoFactorBackupCodes })).toString(
+    'utf-8',
+  );
+
+  const data = JSON.parse(secret);
+
+  const result = ZBackupCodeSchema.safeParse(data);
+
+  if (result.success) {
+    return result.data;
+  }
+
+  return null;
+};