Strengthen Your Auth Googles New Session Metadata Claims

Why This Matters for Your Security Posture

Static authentication policies are no longer enough. With phishing and account takeover on the rise, platforms need granular, real-time signals about how and when users authenticate. Google's new session metadata claims—auth_time and amr—provide exactly that, letting you move from rigid rules to dynamic, risk-based access control.

These OIDC standard claims are added to the ID Token your backend receives, giving you insights into the freshness and strength of the user's Google session. Whether your users have personal Gmail accounts or Google Workspace, you can leverage Google's robust authentication infrastructure and make smarter security decisions without rebuilding your entire auth flow.

Breaking Down the New Claims

• auth_time (Authentication Time): Indicates when the user last authenticated with Google. A recent timestamp gives you confidence that the user is actively present, enabling you to enforce session age policies—like requiring re-authentication for sensitive actions after a set period.
• amr (Authentication Methods Reference): Lists the methods used during authentication, such as password (pwd), multi-factor (mfa), hardware key (hwk), software key (swk), phone (tel), or SMS (sms). This tells you the strength of the authentication event.

These claims work across Android, iOS, and web client and server applications, making them versatile for any stack.

Implementing the Claims in Your App

Adding these claims is straightforward if you're already using Sign in with Google with OpenID Connect. You simply request them via the standard OIDC claims parameter in your authentication request. Here's an example:

https://accounts.google.com/o/oauth2/v2/auth?
  response_type=id_token&
  client_id=YOUR_CLIENT_ID&
  scope=openid email profile&
  redirect_uri=https://example.com/user-login&
  nonce=RANDOM_VALUE&
  claims={
    "id_token": {
      "amr": { "essential": true },
      "auth_time": { "essential": true }
    }
  }

After receiving the ID token, your backend can parse the claims and incorporate them into your authorization logic. For a complete implementation guide, check the official Google Identity documentation.

Beyond Static Policies: Use Cases and Caveats

Practical Use Cases

• Step-up Authentication: Use auth_time to trigger additional verification for sensitive operations if the session is stale, even if the Google session is still valid.
• Granular Access Control: Integrate amr into your rules—for example, deny access to admin functions unless mfa or a hardware key (hwk) was used.
• Audit and Compliance: Log amr values to maintain a record of authentication methods for sensitive data access.

Limitations and Considerations

• Verified Apps Only: These claims are available only for verified applications. Ensure your app is verified to access them.
• Context Matters: amr values are not a silver bullet. They indicate the method, not the risk of the device or network. Combine them with other signals like IP reputation and user behavior for a holistic view.
• Token Size: Adding claims increases the ID token size slightly. Be mindful if you're transmitting tokens in URLs.

Next Steps for Your Security Roadmap

Start by experimenting with these claims in a test environment. Map out your sensitive actions and define policies that use auth_time and amr to enforce step-up authentication. As you become comfortable, consider integrating these signals into your broader risk engine.

For a deeper dive into AI-driven security and automation, explore our guide on leveraging AI coding agents responsibly.

Conclusion: Embrace Dynamic Security

Google's new session metadata claims empower you to build more resilient authentication flows. By leveraging auth_time and amr, you can significantly reduce the risk of account takeover and fraudulent activity, while improving user experience by avoiding unnecessary hurdles for legitimate sessions.

Start small, test thoroughly, and gradually expand your policies. Your users—and your security team—will thank you.

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