BiometricAuthenticator: rework logic and bugs

Otherwise there's a frameworks bug that causes the fragment's activity
to become null.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

ui/src/main/java/com/wireguard/android/fragment/TunnelEditorFragment.kt

@@ -4,6 +4,7 @@
  */
 package com.wireguard.android.fragment
 
+import android.app.Activity
 import android.content.Context
 import android.os.Bundle
 import android.text.InputType
@@ -83,7 +84,7 @@ class TunnelEditorFragment : BaseFragment(), AppExclusionListener {
     }
 
     override fun onDestroyView() {
-        requireActivity().window.clearFlags(WindowManager.LayoutParams.FLAG_SECURE)
+        activity?.window?.clearFlags(WindowManager.LayoutParams.FLAG_SECURE)
         binding = null
         super.onDestroyView()
     }
@@ -106,7 +107,7 @@ class TunnelEditorFragment : BaseFragment(), AppExclusionListener {
                     InputMethodManager.HIDE_NOT_ALWAYS)
         }
         // Tell the activity to finish itself or go back to the detail view.
-        requireActivity().runOnUiThread {
+        activity.runOnUiThread {
             // TODO(smaeul): Remove this hack when fixing the Config ViewModel
             // The selected tunnel has to actually change, but we have to remember this one.
             val savedTunnel = tunnel
@@ -228,13 +229,17 @@ class TunnelEditorFragment : BaseFragment(), AppExclusionListener {
         super.onViewStateRestored(savedInstanceState)
     }
 
+    private var showingAuthenticator = false
+
     fun onKeyClick(view: View) = onKeyFocusChange(view, true)
 
     fun onKeyFocusChange(view: View, isFocused: Boolean) {
-        if (!isFocused) return
+        if (!isFocused || showingAuthenticator) return
         val edit = view as? EditText ?: return
         if (!haveShownKeys && edit.text.isNotEmpty()) {
-            BiometricAuthenticator.authenticate(R.string.biometric_prompt_private_key_title, requireActivity()) {
+            showingAuthenticator = true
+            BiometricAuthenticator.authenticate(R.string.biometric_prompt_private_key_title, this) {
+                showingAuthenticator = false
                 when (it) {
                     is BiometricAuthenticator.Result.Success, is BiometricAuthenticator.Result.HardwareUnavailableOrDisabled -> {
                         haveShownKeys = true
@@ -255,7 +260,7 @@ class TunnelEditorFragment : BaseFragment(), AppExclusionListener {
     }
 
     private fun showPrivateKey(edit: EditText) {
-        requireActivity().window.addFlags(WindowManager.LayoutParams.FLAG_SECURE)
+        activity?.window?.addFlags(WindowManager.LayoutParams.FLAG_SECURE)
         edit.inputType = InputType.TYPE_TEXT_FLAG_NO_SUGGESTIONS or InputType.TYPE_TEXT_VARIATION_VISIBLE_PASSWORD
     }
 

ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.kt

@@ -83,7 +83,8 @@ class ZipExporterPreference(context: Context, attrs: AttributeSet?) : Preference
 
     override fun onClick() {
         val prefActivity = FragmentUtils.getPrefActivity(this)
-        BiometricAuthenticator.authenticate(R.string.biometric_prompt_zip_exporter_title, prefActivity) {
+        val fragment = prefActivity.supportFragmentManager.fragments.first()
+        BiometricAuthenticator.authenticate(R.string.biometric_prompt_zip_exporter_title, fragment) {
             when (it) {
                 // When we have successful authentication, or when there is no biometric hardware available.
                 is BiometricAuthenticator.Result.Success, is BiometricAuthenticator.Result.HardwareUnavailableOrDisabled -> {

ui/src/main/java/com/wireguard/android/util/BiometricAuthenticator.kt

@@ -5,15 +5,21 @@
 
 package com.wireguard.android.util
 
+import android.annotation.SuppressLint
+import android.app.KeyguardManager
+import android.content.Context
+import android.os.Build
 import android.os.Handler
 import android.util.Log
 import androidx.annotation.StringRes
 import androidx.biometric.BiometricConstants
 import androidx.biometric.BiometricManager
 import androidx.biometric.BiometricPrompt
-import androidx.fragment.app.FragmentActivity
+import androidx.core.content.getSystemService
+import androidx.fragment.app.Fragment
 import com.wireguard.android.R
 
+
 object BiometricAuthenticator {
     private const val TAG = "WireGuard/BiometricAuthenticator"
     private val handler = Handler()
@@ -25,12 +31,25 @@ object BiometricAuthenticator {
         object Cancelled : Result()
     }
 
+    @SuppressLint("PrivateApi")
+    private fun isPinEnabled(context: Context): Boolean {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
+            return context.getSystemService<KeyguardManager>()!!.isDeviceSecure
+        return try {
+            val lockUtilsClass = Class.forName("com.android.internal.widget.LockPatternUtils")
+            val lockUtils = lockUtilsClass.getConstructor(Context::class.java).newInstance(context)
+            val method = lockUtilsClass.getMethod("isLockScreenDisabled")
+            !(method.invoke(lockUtils) as Boolean)
+        } catch (e: Exception) {
+            false
+        }
+    }
+
     fun authenticate(
             @StringRes dialogTitleRes: Int,
-            fragmentActivity: FragmentActivity,
+            fragment: Fragment,
             callback: (Result) -> Unit
     ) {
-        val biometricManager = BiometricManager.from(fragmentActivity)
         val authCallback = object : BiometricPrompt.AuthenticationCallback() {
             override fun onAuthenticationError(errorCode: Int, errString: CharSequence) {
                 super.onAuthenticationError(errorCode, errString)
@@ -44,13 +63,13 @@ object BiometricAuthenticator {
                     BiometricConstants.ERROR_NO_BIOMETRICS, BiometricConstants.ERROR_NO_DEVICE_CREDENTIAL -> {
                         Result.HardwareUnavailableOrDisabled
                     }
-                    else -> Result.Failure(errorCode, fragmentActivity.getString(R.string.biometric_auth_error_reason, errString))
+                    else -> Result.Failure(errorCode, fragment.getString(R.string.biometric_auth_error_reason, errString))
                 })
             }
 
             override fun onAuthenticationFailed() {
                 super.onAuthenticationFailed()
-                callback(Result.Failure(null, fragmentActivity.getString(R.string.biometric_auth_error)))
+                callback(Result.Failure(null, fragment.getString(R.string.biometric_auth_error)))
             }
 
             override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
@@ -58,13 +77,12 @@ object BiometricAuthenticator {
                 callback(Result.Success(result.cryptoObject))
             }
         }
-        val biometricPrompt = BiometricPrompt(fragmentActivity, { handler.post(it) }, authCallback)
+        val biometricPrompt = BiometricPrompt(fragment, { handler.post(it) }, authCallback)
         val promptInfo = BiometricPrompt.PromptInfo.Builder()
-                .setTitle(fragmentActivity.getString(dialogTitleRes))
+                .setTitle(fragment.getString(dialogTitleRes))
                 .setDeviceCredentialAllowed(true)
                 .build()
-
+        if (BiometricManager.from(fragment.requireContext()).canAuthenticate() == BiometricManager.BIOMETRIC_SUCCESS || isPinEnabled(fragment.requireContext())) {
-        if (biometricManager.canAuthenticate() == BiometricManager.BIOMETRIC_SUCCESS) {
             biometricPrompt.authenticate(promptInfo)
         } else {
             callback(Result.HardwareUnavailableOrDisabled)