Configure Android platform permissions for biometrics
epic-biometric-session-authentication-foundation-task-003 — Add USE_BIOMETRIC and USE_FINGERPRINT permissions to AndroidManifest.xml. Ensure minSdkVersion is compatible with the BiometricPrompt API (API 23+). Verify Android Keystore is accessible by configuring the FlutterSecureStorage Android options with encryptedSharedPreferences enabled.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 1 - 540 tasks
Can start after Tier 0 completes
Implementation Notes
In android/app/src/main/AndroidManifest.xml, add both permission lines inside the
Note: on API 23–27, BiometricPrompt is not available; local_auth falls back to FingerprintManager. The USE_FINGERPRINT permission covers this legacy path. For devices running API 28+, USE_BIOMETRIC is the correct modern permission. Both must be declared to support the full device range.
Testing Requirements
After configuration changes, run flutter build apk --debug and confirm exit code 0. Launch on Android emulator (API 29+ recommended) and verify the app starts without crash. Use the emulator's Extended Controls → Fingerprint panel to simulate a fingerprint scan if testing the auth flow manually. Run flutter analyze to confirm no regressions.
Verify the AndroidManifest.xml using aapt dump permissions on the built APK: run 'flutter build apk --debug && aapt dump permissions build/app/outputs/flutter-apk/app-debug.apk' and confirm both USE_BIOMETRIC and USE_FINGERPRINT appear. No new automated test files are required for this infrastructure task.
iOS Keychain access requires correct entitlement configuration and provisioning profile setup. Misconfigured entitlements cause silent failures in CI/CD and on physical devices, where the plugin appears to work in the simulator but fails at runtime. This can delay foundation delivery and block all downstream epics.
Mitigation & Contingency
Mitigation: Add a dedicated integration test running on a physical iOS device early in the epic. Document required entitlements and provisioning steps in a developer runbook. Validate Keychain access in the CI pipeline using an iOS simulator with correct entitlements enabled.
Contingency: If Keychain entitlements cannot be resolved quickly, temporarily use in-memory storage behind the SecureSessionStorage interface to unblock downstream epics, then resolve the Keychain issue in a hotfix before release.
The Flutter local_auth plugin has a history of breaking API changes between major versions, and its Android implementation depends on BiometricPrompt which behaves differently across Android API levels (23-34). An incompatible plugin version or unexpected Android API behaviour can cause authentication failures on a significant portion of the target device fleet.
Mitigation & Contingency
Mitigation: Pin local_auth to a specific stable version in pubspec.yaml. Test against Android API levels 23, 28, and 33 in the CI matrix. Review the plugin changelog and migration guide before adopting any version bump.
Contingency: If the pinned version proves incompatible with target devices, evaluate flutter_local_auth_android as a replacement or fork the plugin adapter to isolate the breaking surface.
If users upgrade from a version of the app that stored session data in non-encrypted storage (SharedPreferences), a migration path is required. Failing to migrate silently leaves old tokens in plain storage, creating a security gap and potentially causing confusing authentication state on first launch of the new version.
Mitigation & Contingency
Mitigation: Audit existing storage usage across the codebase before writing SecureSessionStorage. If legacy plain storage keys exist, implement a one-time migration routine that reads from SharedPreferences, writes to Keychain/Keystore, and deletes the plain-text entry.
Contingency: If migration is discovered late, ship the migration as a mandatory patch release before the biometric feature is enabled for users, and add a startup check that blocks biometric opt-in until migration is confirmed complete.