Mobile App Protection via Biometrics

[carlhye]

Problem statement

The mobile application currently lacks biometric authentication, creating a critical security vulnerability. If a user's mobile device is lost, stolen, or accessed by an unauthorized person, that individual gains full control over the home's security system - including the ability to disable alarms, unlock doors, and manipulate other security-critical functions. This impacts all HA users who rely on mobile app control and directly undermines HA's core goal of providing secure, trustworthy home automation.

Scope & Boundaries

In scope

• Biometric authentication (Face ID, fingerprint, or platform equivalent) required on app launch
• Biometric re-authentication after periods of inactivity
• Fallback PIN/password authentication when biometrics unavailable
• Support for both iOS and Android native biometric systems
• User settings to enable/disable biometric protection (with security warnings)

Not in scope

• Multi-factor authentication (MFA) beyond biometrics
• Remote device wipe capabilities
• Biometric authentication for individual device control (only app-level protection)
• Backend authentication changes - this is client-side security only

Foreseen solution

Implement platform-native biometric authentication that triggers when:

• The app is launched from a closed state
• The app returns from background after a defined timeout (e.g., 5 minutes)
• User is about to perform security-critical actions (optional enhanced protection)

The implementation will use native APIs (iOS: LocalAuthentication framework, Android: BiometricPrompt API) with graceful fallback to device PIN/password. Users can configure biometric settings in app preferences, though disabling protection requires acknowledging security implications.

Low-fidelity flow:

App Launch → Biometric Prompt → [Success: Home Screen] / [Failure: Retry or Fallback]
Background Return (>5min) → Re-authentication Required
Settings → Security → Toggle Biometric Lock [ON/OFF with warning]

Community signals

No response

Risks & open questions

• Device compatibility: What happens on older devices without biometric hardware? (Answer: Fallback to PIN/password only)
• User friction: Will mandatory biometric checks frustrate users in emergency situations? (Mitigation: Fast fallback to PIN, timeout configuration) or should the users have the option to not have app authentication, like today?
• Accessibility: Are biometric systems accessible for all users? (Mitigation: Always provide alternative authentication methods)
• UX consistency: How do we handle biometric failures gracefully without blocking legitimate users?
• Technical debt: Does this require significant refactoring of current authentication flow?

Appetite

Small - roughly 1 cycle or less
This is primarily a client-side implementation using well-established platform APIs. Most of the work involves UI integration, state management for authentication status, and testing across device types.

Execution issues

No response

Decision log

Date	Decision	Outcome