Title: Hash Empty Error with MSAL React Authentication in Mobile Browsers

Tags: react, msal, azure, authentication, mobile-browsers

Body:

I'm using the Microsoft Authentication Library (MSAL) with a React Single Page Application (SPA) configured for Azure Entra ID, following the official documentation here.

I have set up two authentication methods: loginRedirect and loginPopup. While the desktop browser login works reliably, I'm facing unpredictable login issues on mobile browsers. Sometimes, users can log in successfully, but often they encounter problems.

Issue:

I discovered that the root cause was a hash_empty_error occurring on mobile. My routing logic involved using PublicRoute and PrivateRoute components for protected routes, which redirected users to your_frontend_url+'/login' when not authorized. This routing setup was inadvertently clearing my hash value, leading to session storage being cleared and users becoming unauthorized after several login attempts.

To resolve this, I started using window.location.hash and window.location.pathname to check the authentication state correctly.

Original PrivateRoute Component:

import { AuthenticatedTemplate, useMsal } from "@azure/msal-react";
import PropTypes from "prop-types";
import { Navigate } from "react-router-dom";

export const PrivateRoute = ({ element }) => {
  const { accounts } = useMsal();
  const isAuthenticated = accounts && accounts.length > 0;

  if (isAuthenticated) {
    return <AuthenticatedTemplate>{element}</AuthenticatedTemplate>;
  } else {
    return <Navigate to="/login" />;
  }
};

PrivateRoute.propTypes = {
  element: PropTypes.element.isRequired,
};

Updated PrivateRoute Component:

import Loading from "@assets/Loading";
import { AuthenticatedTemplate, useMsal } from "@azure/msal-react";
import PropTypes from "prop-types";
import { Navigate } from "react-router-dom";

export const PrivateRoute = ({ element }) => {
  const { accounts, inProgress } = useMsal();
  const isAuthenticated = accounts && accounts.length > 0;
  const hashValue = window.location.hash;

  if (inProgress === "login" || inProgress === "handleRedirect") {
    return (
      <div className="h-[100dvh] w-full flex flex-col justify-center items-center gap-4">
        <Loading height={10} />
        <p>Login in progress ...</p>
      </div>
    );
  }

  if (isAuthenticated || (window.location.pathname === "/" && hashValue !== "")) {
    return <AuthenticatedTemplate>{element}</AuthenticatedTemplate>;
  } else {
    return <Navigate to="/login" />;
  }
};

PrivateRoute.propTypes = {
  element: PropTypes.element.isRequired,
};

Question:

While this update seems to mitigate the issue, I would like to know if there are any best practices or alternative approaches to handle this type of authentication flow more reliably, especially for mobile browsers. Any insights or experiences would be greatly appreciated!

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