Split authenticationValidityDurationSeconds between android and iOS

android/src/main/kotlin/design/codeux/biometric_storage/BiometricStorageFile.kt

@@ -8,11 +8,12 @@ import mu.KotlinLogging
 import java.io.File
 import java.io.IOException
 import javax.crypto.Cipher
+import kotlin.time.Duration
 
 private val logger = KotlinLogging.logger {}
 
 data class InitOptions(
-    val authenticationValidityDurationSeconds: Int = -1,
+    val androidAuthenticationValidityDuration: Duration? = null,
     val authenticationRequired: Boolean = true,
     val androidBiometricOnly: Boolean = true
 )
@@ -44,20 +45,22 @@ class BiometricStorageFile(
             setIsStrongBoxBacked(useStrongBox)
         }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
-            if (options.authenticationValidityDurationSeconds == -1) {
+            if (options.androidAuthenticationValidityDuration == null) {
                 setUserAuthenticationParameters(
                     0,
                     KeyProperties.AUTH_BIOMETRIC_STRONG
                 )
             } else {
                 setUserAuthenticationParameters(
-                    options.authenticationValidityDurationSeconds,
+                    options.androidAuthenticationValidityDuration.inWholeSeconds.toInt(),
                     KeyProperties.AUTH_DEVICE_CREDENTIAL or KeyProperties.AUTH_BIOMETRIC_STRONG
                 )
             }
         } else {
             @Suppress("DEPRECATION")
-            setUserAuthenticationValidityDurationSeconds(options.authenticationValidityDurationSeconds)
+            setUserAuthenticationValidityDurationSeconds(
+                options.androidAuthenticationValidityDuration?.inWholeSeconds?.toInt() ?: -1
+            )
         }
     }
 
@@ -74,8 +77,8 @@ class BiometricStorageFile(
     }
 
     private fun validateOptions() {
-        if (options.authenticationValidityDurationSeconds == -1 && !options.androidBiometricOnly) {
-            throw IllegalArgumentException("when authenticationValidityDurationSeconds is -1, androidBiometricOnly must be true")
+        if (options.androidAuthenticationValidityDuration == null && !options.androidBiometricOnly) {
+            throw IllegalArgumentException("when androidAuthenticationValidityDuration is null, androidBiometricOnly must be true")
         }
     }
 

android/src/main/kotlin/design/codeux/biometric_storage/BiometricStoragePlugin.kt

@@ -22,6 +22,8 @@ import java.io.StringWriter
 import java.util.concurrent.ExecutorService
 import java.util.concurrent.Executors
 import javax.crypto.Cipher
+import kotlin.time.Duration
+import kotlin.time.Duration.Companion.seconds
 
 private val logger = KotlinLogging.logger {}
 
@@ -176,7 +178,7 @@ class BiometricStoragePlugin : FlutterPlugin, ActivityAware, MethodCallHandler {
                     CipherMode.Decrypt -> cipherForDecrypt()
                 }
 
-                val cipher = if (options.authenticationValidityDurationSeconds > -1) {
+                val cipher = if (options.androidAuthenticationValidityDuration != null) {
                     null
                 } else try {
                     cipherForMode()
@@ -222,7 +224,7 @@ class BiometricStoragePlugin : FlutterPlugin, ActivityAware, MethodCallHandler {
 
                     val options = call.argument<Map<String, Any>>("options")?.let { it ->
                         InitOptions(
-                            authenticationValidityDurationSeconds = it["authenticationValidityDurationSeconds"] as Int,
+                            androidAuthenticationValidityDuration = (it["androidAuthenticationValidityDurationSeconds"] as Int?)?.seconds,
                             authenticationRequired = it["authenticationRequired"] as Boolean,
                             androidBiometricOnly = it["androidBiometricOnly"] as Boolean,
                         )
@@ -398,9 +400,9 @@ class BiometricStoragePlugin : FlutterPlugin, ActivityAware, MethodCallHandler {
             promptBuilder.setAllowedAuthenticators(DEVICE_CREDENTIAL or BIOMETRIC_STRONG)
         }
 
-        if (cipher == null || options.authenticationValidityDurationSeconds >= 0) {
-            // if authenticationValidityDurationSeconds is not -1 we can't use a CryptoObject
-            logger.debug { "Authenticating without cipher. ${options.authenticationValidityDurationSeconds}" }
+        if (cipher == null || options.androidAuthenticationValidityDuration != null) {
+            // if androidAuthenticationValidityDuration is not null we can't use a CryptoObject
+            logger.debug { "Authenticating without cipher. ${options.androidAuthenticationValidityDuration}" }
             prompt.authenticate(promptBuilder.build())
         } else {
             prompt.authenticate(promptBuilder.build(), BiometricPrompt.CryptoObject(cipher))

lib/src/biometric_storage.dart

@@ -80,13 +80,45 @@ class AuthException implements Exception {
 
 class StorageFileInitOptions {
   StorageFileInitOptions({
+    Duration? androidAuthenticationValidityDuration,
+    Duration? iosTouchIDAuthenticationAllowableReuseDuration,
+    this.iosTouchIDAuthenticationForceReuseContextDuration,
     this.authenticationValidityDurationSeconds = -1,
     this.authenticationRequired = true,
     this.androidBiometricOnly = true,
-  });
-
+  })  : androidAuthenticationValidityDuration =
+            androidAuthenticationValidityDuration ??
+                (authenticationValidityDurationSeconds <= 0
+                    ? null
+                    : Duration(seconds: authenticationValidityDurationSeconds)),
+        iosTouchIDAuthenticationAllowableReuseDuration =
+            iosTouchIDAuthenticationAllowableReuseDuration ??
+                (authenticationValidityDurationSeconds <= 0
+                    ? null
+                    : Duration(seconds: authenticationValidityDurationSeconds));
+
+  @Deprecated('use androidAuthenticationValidityDuration instead')
   final int authenticationValidityDurationSeconds;
 
+  /// see https://developer.android.com/reference/android/security/keystore/KeyGenParameterSpec.Builder#setUserAuthenticationParameters(int,%20int)
+  final Duration? androidAuthenticationValidityDuration;
+
+  /// see https://developer.apple.com/documentation/localauthentication/lacontext/1622329-touchidauthenticationallowablere
+  /// > If the user unlocks the device using Touch ID within the specified time interval, then authentication for the receiver succeeds automatically, without prompting the user for Touch ID. This bypasses a scenario where the user unlocks the device and then is almost immediately prompted for another fingerprint.
+  /// and https://developer.apple.com/documentation/localauthentication/accessing_keychain_items_with_face_id_or_touch_id
+  /// > Note that this grace period applies specifically to device unlock with Touch ID, not keychain retrieval authentications
+  ///
+  /// If you want to avoid requiring authentication after a successful
+  /// keychain retrieval see [iosTouchIDAuthenticationForceReuseContextDuration]
+  final Duration? iosTouchIDAuthenticationAllowableReuseDuration;
+
+  /// To prevent forcing the user to authenticate again after unlocking once
+  /// we can reuse the `LAContext` object for the given amount of time.
+  /// see https://github.com/authpass/biometric_storage/pull/73
+  /// This is pretty much undocumented behavior, but works similar to
+  /// `androidAuthenticationValidityDuration`.
+  final Duration? iosTouchIDAuthenticationForceReuseContextDuration;
+
   /// Whether an authentication is required. if this is
   /// false NO BIOMETRIC CHECK WILL BE PERFORMED! and the value
   /// will simply be save encrypted. (default: true)
@@ -97,14 +129,20 @@ class StorageFileInitOptions {
   /// On Android < 30 this will always be ignored. (always `true`)
   /// https://github.com/authpass/biometric_storage/issues/12#issuecomment-900358154
   ///
-  /// Also: this **must** be `true` if [authenticationValidityDurationSeconds]
-  /// is `-1`.
+  /// Also: this **must** be `true` if [androidAuthenticationValidityDuration]
+  /// is null.
   /// https://github.com/authpass/biometric_storage/issues/12#issuecomment-902508609
   final bool androidBiometricOnly;
 
   Map<String, dynamic> toJson() => <String, dynamic>{
         'authenticationValidityDurationSeconds':
             authenticationValidityDurationSeconds,
+        'androidAuthenticationValidityDurationSeconds':
+            androidAuthenticationValidityDuration?.inSeconds,
+        'iosTouchIDAuthenticationAllowableReuseDurationSeconds':
+            iosTouchIDAuthenticationAllowableReuseDuration?.inSeconds,
+        'iosTouchIDAuthenticationForceReuseContextDurationSeconds':
+            iosTouchIDAuthenticationForceReuseContextDuration?.inSeconds,
         'authenticationRequired': authenticationRequired,
         'androidBiometricOnly': androidBiometricOnly,
       };

macos/Classes/BiometricStorageImpl.swift

@@ -14,10 +14,12 @@ struct StorageMethodCall {
 
 class InitOptions {
   init(params: [String: Any]) {
-    authenticationValidityDurationSeconds = params["authenticationValidityDurationSeconds"] as? Int
+    iosTouchIDAuthenticationAllowableReuseDuration = params["iosTouchIDAuthenticationAllowableReuseDurationSeconds"] as? Int
+    iosTouchIDAuthenticationForceReuseContextDuration = params["iosTouchIDAuthenticationForceReuseContextDurationSeconds"] as? Int
     authenticationRequired = params["authenticationRequired"] as? Bool
   }
-  let authenticationValidityDurationSeconds: Int!
+  let iosTouchIDAuthenticationAllowableReuseDuration: Int?
+  let iosTouchIDAuthenticationForceReuseContextDuration: Int?
   let authenticationRequired: Bool!
 }
 
@@ -148,23 +150,41 @@ class BiometricStorageImpl {
   }
 }
 
+typealias StoredContext = (context: LAContext, expireAt: Date)
+
 class BiometricStorageFile {
   private let name: String
   private let initOptions: InitOptions
-  private var context: LAContext { get {
-    let context = LAContext()
-    if (initOptions.authenticationRequired) {
-      if initOptions.authenticationValidityDurationSeconds > 0 {
-        if #available(OSX 10.12, *) {
-          context.touchIDAuthenticationAllowableReuseDuration = Double(initOptions.authenticationValidityDurationSeconds)
+  private var _context: StoredContext?
+  private var context: LAContext {
+    get {
+      if let context = _context {
+        if context.expireAt.timeIntervalSinceNow < 0 {
+          // already expired.
+          _context = nil
         } else {
-          // Fallback on earlier versions
-          hpdebug("Pre OSX 10.12 no touchIDAuthenticationAllowableReuseDuration available. ignoring.")
+          return context.context
         }
       }
+
+      let context = LAContext()
+      if (initOptions.authenticationRequired) {
+        if let duration = initOptions.iosTouchIDAuthenticationAllowableReuseDuration {
+          if #available(OSX 10.12, *) {
+            context.touchIDAuthenticationAllowableReuseDuration = Double(duration)
+          } else {
+            // Fallback on earlier versions
+            hpdebug("Pre OSX 10.12 no touchIDAuthenticationAllowableReuseDuration available. ignoring.")
+          }
+        }
+
+        if let duration = initOptions.iosTouchIDAuthenticationForceReuseContextDuration {
+          _context = (context: context, expireAt: Date(timeIntervalSinceNow: Double(duration)))
+        }
+      }
+      return context
     }
-    return context
-  } }
+  }
   private let storageError: StorageError
 
   init(name: String, initOptions: InitOptions, storageError: @escaping StorageError) {