Add secure storage fallback option

android/app/src/main/java/com/banano/kaliumwallet/LegacyStorage.java

@@ -0,0 +1,21 @@
+package com.banano.kaliumwallet;
+
+import android.util.Base64;
+
+public class LegacyStorage {
+
+    public String getSecret() {
+       return generateEncryptionKey();
+    }
+
+    private String generateEncryptionKey() {
+        if (Vault.getVault().getString(Vault.ENCRYPTION_KEY_NAME, null) == null) {
+        Vault.getVault()
+                .edit()
+                .putString(Vault.ENCRYPTION_KEY_NAME,
+                        Base64.encodeToString(Vault.generateKey(), Base64.DEFAULT))
+                .apply();
+        }
+        return Vault.getVault().getString(Vault.ENCRYPTION_KEY_NAME, null);
+    }
+}

android/app/src/main/java/com/banano/kaliumwallet/MainActivity.java

@@ -28,6 +28,8 @@ public void onMethodCall(MethodCall call, MethodChannel.Result result) {
                       new MigrationStuff().clearLegacyData();
                   } else if (call.method.equals("getLegacyPin")) {
                       result.success(new MigrationStuff().getLegacyPin());
+                  } else if (call.method.equals("getSecret")) {
+                      result.success(new LegacyStorage().getSecret());
                   } else {
                       result.notImplemented();
                   }

android/app/src/main/java/com/banano/kaliumwallet/MultidexApplication.java

@@ -34,10 +34,10 @@ public void onCreate() {
 
         try {
             Vault.initializeVault(this);
+            generateEncryptionKey();
         } catch (Exception e) {
 
         }
-        generateEncryptionKey();
         FlutterMain.startInitialization(this);
     }
 

lib/main.dart

@@ -266,43 +266,59 @@ class SplashState extends State<Splash> with WidgetsBindingObserver {
   }
 
   Future checkLoggedIn() async {
-    // iOS key store is persistent, so if this is first launch then we will clear the keystore
-    bool firstLaunch = await SharedPrefsUtil.inst.getFirstLaunch();
-    if (firstLaunch) {
-      bool migrated = false;
-      if (Platform.isAndroid) {
-        migrated = await _doAndroidMigration();
+    try {
+      // iOS key store is persistent, so if this is first launch then we will clear the keystore
+      bool firstLaunch = await SharedPrefsUtil.inst.getFirstLaunch();
+      if (firstLaunch) {
+        bool migrated = false;
+        if (Platform.isAndroid) {
+          migrated = await _doAndroidMigration();
+        }
+        if (!migrated) {
+          await Vault.inst.deleteAll();
+        }
       }
-      if (!migrated) {
-        await Vault.inst.deleteAll();
+      await SharedPrefsUtil.inst.setFirstLaunch();
+      await SharedPrefsUtil.inst.setFirstLaunch();
+      // See if logged in already
+      bool isLoggedIn = false;
+      var seed = await Vault.inst.getSeed();
+      var pin = await Vault.inst.getPin();
+      // If we have a seed set, but not a pin - or vice versa
+      // Then delete the seed and pin from device and start over.
+      // This would mean user did not complete the intro screen completely.
+      if (seed != null && pin != null) {
+        isLoggedIn = true;
+      } else if (seed != null && pin == null) {
+        await Vault.inst.deleteSeed();
+      } else if (pin != null && seed == null) {
+        await Vault.inst.deletePin();
       }
-    }
-    await SharedPrefsUtil.inst.setFirstLaunch();
-    await SharedPrefsUtil.inst.setFirstLaunch();
-    // See if logged in already
-    bool isLoggedIn = false;
-    var seed = await Vault.inst.getSeed();
-    var pin = await Vault.inst.getPin();
-    // If we have a seed set, but not a pin - or vice versa
-    // Then delete the seed and pin from device and start over.
-    // This would mean user did not complete the intro screen completely.
-    if (seed != null && pin != null) {
-      isLoggedIn = true;
-    } else if (seed != null && pin == null) {
-      await Vault.inst.deleteSeed();
-    } else if (pin != null && seed == null) {
-      await Vault.inst.deletePin();
-    }
 
-    if (isLoggedIn) {
-      if (await SharedPrefsUtil.inst.getLock() || await SharedPrefsUtil.inst.shouldLock()) {
-        Navigator.of(context).pushReplacementNamed('/lock_screen');
+      if (isLoggedIn) {
+        if (await SharedPrefsUtil.inst.getLock() || await SharedPrefsUtil.inst.shouldLock()) {
+          Navigator.of(context).pushReplacementNamed('/lock_screen');
+        } else {
+          await NanoUtil().loginAccount(context);
+          Navigator.of(context).pushReplacementNamed('/home');
+        }
       } else {
-        await NanoUtil().loginAccount(context);
-        Navigator.of(context).pushReplacementNamed('/home');
+        Navigator.of(context).pushReplacementNamed('/intro_welcome');
+      }
+    } catch (e) {
+      /// Fallback secure storage
+      /// A very small percentage of users are encountering issues writing to the
+      /// Android keyStore using the flutter_secure_storage plugin.
+      /// 
+      /// Instead of telling them they are out of luck, this is an automatic "fallback"
+      /// It will generate a 64-byte secret using the native android "bottlerocketstudios" Vault
+      /// This secret is used to encrypt sensitive data and save it in SharedPreferences
+      if (Platform.isAndroid && e.toString().contains("flutter_secure")) {
+        if (!(await SharedPrefsUtil.inst.useLegacyStorage())) {
+          await SharedPrefsUtil.inst.setUseLegacyStorage();
+          checkLoggedIn();
+        }
       }
-    } else {
-      Navigator.of(context).pushReplacementNamed('/intro_welcome');
     }
   }
 

lib/model/vault.dart

@@ -1,5 +1,11 @@
+import 'package:flutter/services.dart';
+
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:kalium_wallet_flutter/util/encrypt.dart';
+import 'package:kalium_wallet_flutter/util/sharedprefsutil.dart';
+
 /**
  * Singleton for keystore access methods in android/iOS
  */
@@ -13,17 +19,35 @@ class Vault {
   static const String pinKey = 'fkalium_pin';
   final FlutterSecureStorage secureStorage = new FlutterSecureStorage();
 
+  Future<bool> legacy() async {
+    return await SharedPrefsUtil.inst.useLegacyStorage();
+  }
+
   // Re-usable
   Future<String> _write(String key, String value) async {
-    await secureStorage.write(key:key, value:value);
+    if (await legacy()) {
+      await setEncrypted(key, value);
+    } else {
+      await secureStorage.write(key:key, value:value);
+    }
     return value;
   }
 
   Future<String> _read(String key, {String defaultValue}) async {
+    if (await legacy()) {
+      return await getEncrypted(key);
+    }
     return await secureStorage.read(key:key) ?? defaultValue;
   }
 
   Future<void> deleteAll() async {
+    if (await legacy()) {
+      SharedPreferences prefs = await SharedPreferences.getInstance();
+      await prefs.remove(encryptionKey);
+      await prefs.remove(seedKey);
+      await prefs.remove(pinKey);
+      return;
+    }
     return await secureStorage.deleteAll();
   }
 
@@ -37,6 +61,10 @@ class Vault {
   }
 
   Future<void> deleteSeed() async {
+    if (await legacy()) {
+      SharedPreferences prefs = await SharedPreferences.getInstance();
+      await prefs.remove(seedKey);
+    }
     return await secureStorage.delete(key: seedKey);
   }
 
@@ -49,6 +77,10 @@ class Vault {
   }
 
   Future<void> deleteEncryptionPhrase() async {
+    if (await legacy()) {
+      SharedPreferences prefs = await SharedPreferences.getInstance();
+      await prefs.remove(encryptionKey);
+    }
     return await secureStorage.delete(key: encryptionKey);
   }
 
@@ -61,6 +93,39 @@ class Vault {
   }
 
   Future<void> deletePin() async {
+    if (await legacy()) {
+      SharedPreferences prefs = await SharedPreferences.getInstance();
+      await prefs.remove(pinKey);
+    }
     return await secureStorage.delete(key: pinKey);
   }
+
+  // For encrypted data
+  Future<void> setEncrypted(String key, String value) async {
+    String secret = await getSecret();
+    if (secret == null) return null;
+    // Decrypt and return
+    Salsa20Encryptor encrypter = new Salsa20Encryptor(secret.substring(0, secret.length - 8), secret.substring(secret.length - 8));
+    // Encrypt and save
+    SharedPreferences prefs = await SharedPreferences.getInstance();
+    prefs.setString(key, encrypter.encrypt(value));
+  }
+
+  Future<String> getEncrypted(String key) async {
+    String secret = await getSecret();
+    if (secret == null) return null;
+    // Decrypt and return
+    Salsa20Encryptor encrypter = new Salsa20Encryptor(secret.substring(0, secret.length - 8), secret.substring(secret.length - 8));
+    SharedPreferences prefs = await SharedPreferences.getInstance();
+    String encrypted = prefs.get(key);
+    if (encrypted == null) return null;
+    return encrypter.decrypt(encrypted);
+  }
+
+  static const _channel = const MethodChannel('fappchannel');
+
+  static Future<String> getSecret() async {
+    return await _channel.invokeMethod('getSecret');
+  }
+
 }

lib/util/sharedprefsutil.dart

@@ -37,6 +37,8 @@ class SharedPrefsUtil {
   // For maximum pin attempts
   static const String pin_attempts = 'fkalium_pin_attempts';
   static const String pin_lock_until = 'fkalium_lock_duraton';
+  // For certain keystore incompatible androids
+  static const String use_legacy_storage = 'fkalium_legacy_storage';
 
   // For plain-text data
   Future<void> set(String key, value) async {
@@ -218,6 +220,14 @@ class SharedPrefsUtil {
     return false;
   }
 
+  Future<bool> useLegacyStorage() async {
+    return await get(use_legacy_storage, defaultValue: false);
+  }
+
+  Future<void> setUseLegacyStorage() async {
+    await set(use_legacy_storage, true);
+  }
+
   Future<void> updateLockDate() async {
     int attempts = await getLockAttempts();
     if (attempts >= 20) {

pubspec.yaml

@@ -7,7 +7,7 @@ description: A new Flutter project.
 # Both the version and the builder number may be overridden in flutter
 # build by specifying --build-name and --build-number, respectively.
 # Read more about versioning at semver.org.
-version: 2.0.3+61
+version: 2.0.4+62
 
 environment:
   sdk: ">=2.0.0-dev.68.0 <3.0.0"