P6 Stream T: finish BiometricLockScreen + BiometricManager
BiometricPrompt wrapper with 3-strike lockout + NO_HARDWARE bypass. BiometricLockScreen with auto-prompt on mount + PIN fallback after 3 failures. PIN wiring marked TODO for secure-storage follow-up. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Trey T
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package com.tt.honeyDue.security
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import androidx.biometric.BiometricManager as AndroidXBiometricManager
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import androidx.biometric.BiometricPrompt
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import androidx.core.content.ContextCompat
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import androidx.fragment.app.FragmentActivity
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import kotlinx.coroutines.suspendCancellableCoroutine
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import kotlin.coroutines.resume
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/**
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* P6 Stream T — Android biometric authentication wrapper.
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*
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* Thin layer over [androidx.biometric.BiometricPrompt] that exposes a
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* suspend function returning a typed [Result] — parity with iOS
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* LAContext-based unlock in the SwiftUI app.
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*
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* Features:
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* - 3-strike lockout: after [MAX_FAILURES] consecutive failures in a row,
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* the next [authenticate] call returns [Result.TooManyAttempts] WITHOUT
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* showing the system prompt. The caller must drive the fallback (PIN)
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* flow and reset the counter via [reset].
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* - NO_HARDWARE bypass: [canAuthenticate] surfaces whether a prompt can
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* even be shown, so callers can skip the lock screen entirely on
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* devices without biometric hardware.
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*
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* The real [BiometricPrompt] is obtained via [promptFactory] so unit tests
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* can inject a fake that directly invokes the callback. In production the
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* default factory wires the activity + main-thread executor.
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*/
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class BiometricManager(
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private val activity: FragmentActivity,
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private val promptFactory: (BiometricPrompt.AuthenticationCallback) -> Prompter =
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{ callback ->
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val executor = ContextCompat.getMainExecutor(activity)
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val prompt = BiometricPrompt(activity, executor, callback)
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Prompter { info -> prompt.authenticate(info) }
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},
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private val availabilityProbe: () -> Availability = {
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defaultAvailability(activity)
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},
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) {
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/** Allows tests to intercept the [BiometricPrompt.authenticate] call. */
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fun interface Prompter {
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fun show(info: BiometricPrompt.PromptInfo)
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}
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/** High-level outcome returned by [authenticate]. */
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sealed class Result {
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object Success : Result()
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object UserCanceled : Result()
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/** 3+ consecutive failures — caller must switch to PIN fallback. */
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object TooManyAttempts : Result()
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/** Device lacks biometric hardware or enrollment — bypass lock. */
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object NoHardware : Result()
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data class Error(val code: Int, val message: String) : Result()
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}
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/** Result of [canAuthenticate]; drives whether to show the lock screen. */
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enum class Availability {
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NO_HARDWARE,
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NOT_ENROLLED,
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AVAILABLE,
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}
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private var consecutiveFailures: Int = 0
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/** Quick probe — does this device support biometric auth right now? */
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fun canAuthenticate(): Availability = availabilityProbe()
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/** Resets the 3-strike counter — call after a successful fallback. */
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fun reset() {
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consecutiveFailures = 0
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}
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/**
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* Show the biometric prompt and suspend until the user resolves it.
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*
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* Returns [Result.TooManyAttempts] immediately (without showing a
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* prompt) when the 3-strike threshold has been crossed.
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*/
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suspend fun authenticate(
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title: String,
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subtitle: String? = null,
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negativeButtonText: String = "Cancel",
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): Result {
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if (consecutiveFailures >= MAX_FAILURES) {
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return Result.TooManyAttempts
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}
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return suspendCancellableCoroutine { cont ->
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val callback = object : BiometricPrompt.AuthenticationCallback() {
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override fun onAuthenticationSucceeded(
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result: BiometricPrompt.AuthenticationResult
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) {
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consecutiveFailures = 0
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if (cont.isActive) cont.resume(Result.Success)
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}
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override fun onAuthenticationFailed() {
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// Per Android docs, this does NOT dismiss the prompt —
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// the system continues listening. We count the strike
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// but do NOT resume here; resolution comes via
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// onAuthenticationError or onAuthenticationSucceeded.
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consecutiveFailures++
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}
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override fun onAuthenticationError(
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errorCode: Int,
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errString: CharSequence,
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) {
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if (!cont.isActive) return
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val result = when (errorCode) {
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BiometricPrompt.ERROR_USER_CANCELED,
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BiometricPrompt.ERROR_NEGATIVE_BUTTON,
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BiometricPrompt.ERROR_CANCELED -> Result.UserCanceled
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BiometricPrompt.ERROR_HW_NOT_PRESENT,
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BiometricPrompt.ERROR_HW_UNAVAILABLE,
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BiometricPrompt.ERROR_NO_BIOMETRICS -> Result.NoHardware
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BiometricPrompt.ERROR_LOCKOUT,
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BiometricPrompt.ERROR_LOCKOUT_PERMANENT -> {
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consecutiveFailures = MAX_FAILURES
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Result.TooManyAttempts
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}
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else -> Result.Error(errorCode, errString.toString())
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}
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cont.resume(result)
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}
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}
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val info = BiometricPrompt.PromptInfo.Builder()
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.setTitle(title)
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.apply { subtitle?.let(::setSubtitle) }
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.setNegativeButtonText(negativeButtonText)
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.setAllowedAuthenticators(
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AndroidXBiometricManager.Authenticators.BIOMETRIC_STRONG or
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AndroidXBiometricManager.Authenticators.BIOMETRIC_WEAK
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)
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.build()
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promptFactory(callback).show(info)
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}
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}
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/** Test hook — inspect current strike count. */
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internal fun currentFailureCount(): Int = consecutiveFailures
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/** Test hook — seed the strike count (e.g. to simulate prior failures). */
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internal fun seedFailures(count: Int) {
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consecutiveFailures = count
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}
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companion object {
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/** Matches iOS LAContext 3-strike convention. */
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const val MAX_FAILURES: Int = 3
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private fun defaultAvailability(activity: FragmentActivity): Availability {
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val mgr = AndroidXBiometricManager.from(activity)
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return when (
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mgr.canAuthenticate(
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AndroidXBiometricManager.Authenticators.BIOMETRIC_STRONG or
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AndroidXBiometricManager.Authenticators.BIOMETRIC_WEAK
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)
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) {
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AndroidXBiometricManager.BIOMETRIC_SUCCESS -> Availability.AVAILABLE
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AndroidXBiometricManager.BIOMETRIC_ERROR_NONE_ENROLLED -> Availability.NOT_ENROLLED
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AndroidXBiometricManager.BIOMETRIC_ERROR_NO_HARDWARE,
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AndroidXBiometricManager.BIOMETRIC_ERROR_HW_UNAVAILABLE,
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AndroidXBiometricManager.BIOMETRIC_ERROR_UNSUPPORTED -> Availability.NO_HARDWARE
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else -> Availability.NO_HARDWARE
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}
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}
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}
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}
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