android: fix crash on restoring from backup (#1350)

* Restoring app's data from backup tools will still allow to enter passphrase instead of just crashing

(cherry picked from commit 256243dc8c)

* corrections

Co-authored-by: Avently <7953703+avently@users.noreply.github.com>

apps/android/app/src/main/java/chat/simplex/app/views/usersettings/Cryptor.kt

@@ -3,6 +3,9 @@ package chat.simplex.app.views.usersettings
 import android.annotation.SuppressLint
 import android.security.keystore.KeyGenParameterSpec
 import android.security.keystore.KeyProperties
+import chat.simplex.app.R
+import chat.simplex.app.views.helpers.AlertManager
+import chat.simplex.app.views.helpers.generalGetString
 import java.security.KeyStore
 import javax.crypto.*
 import javax.crypto.spec.GCMParameterSpec
@@ -10,11 +13,24 @@ import javax.crypto.spec.GCMParameterSpec
 @SuppressLint("ObsoleteSdkInt")
 internal class Cryptor {
   private var keyStore: KeyStore = KeyStore.getInstance("AndroidKeyStore").apply { load(null) }
+  private var warningShown = false
 
-  fun decryptData(data: ByteArray, iv: ByteArray, alias: String): String {
+  fun decryptData(data: ByteArray, iv: ByteArray, alias: String): String? {
+    val secretKey = getSecretKey(alias)
+    if (secretKey == null) {
+      if (!warningShown) {
+        // Repeated calls will not show the alert again
+        warningShown = true
+        AlertManager.shared.showAlertMsg(
+          title = generalGetString(R.string.wrong_passphrase),
+          text = generalGetString(R.string.restore_passphrase_not_found_desc)
+        )
+      }
+      return null
+    }
     val cipher: Cipher = Cipher.getInstance(TRANSFORMATION)
     val spec = GCMParameterSpec(128, iv)
-    cipher.init(Cipher.DECRYPT_MODE, getSecretKey(alias), spec)
+    cipher.init(Cipher.DECRYPT_MODE, secretKey, spec)
     return String(cipher.doFinal(data))
   }
 
@@ -29,7 +45,7 @@ internal class Cryptor {
     keyStore.deleteEntry(alias)
   }
 
-  private fun createSecretKey(alias: String): SecretKey {
+  private fun createSecretKey(alias: String): SecretKey? {
     if (keyStore.containsAlias(alias)) return getSecretKey(alias)
     val keyGenerator: KeyGenerator = KeyGenerator.getInstance(KEY_ALGORITHM, "AndroidKeyStore")
     keyGenerator.init(
@@ -41,8 +57,8 @@ internal class Cryptor {
     return keyGenerator.generateKey()
   }
 
-  private fun getSecretKey(alias: String): SecretKey {
-    return (keyStore.getEntry(alias, null) as KeyStore.SecretKeyEntry).secretKey
+  private fun getSecretKey(alias: String): SecretKey? {
+    return (keyStore.getEntry(alias, null) as? KeyStore.SecretKeyEntry)?.secretKey
   }
 
   companion object {

apps/android/app/src/main/res/values-de/strings.xml

@@ -682,6 +682,7 @@
   <string name="restore_database_alert_desc">Bitte geben Sie das vorherige Passwort ein, nachdem Sie die Datenbanksicherung wiederhergestellt haben. Diese Aktion kann nicht rückgängig gemacht werden.</string>
   <string name="restore_database_alert_confirm">Wiederherstellen</string>
   <string name="database_restore_error">Fehler bei der Wiederherstellung der Datenbank</string>
+  <string name="restore_passphrase_not_found_desc">***Passphrase not found in Keystore, please enter it manually. This may have happened if you restored the app\'s data using a backup tool. If it\'s not the case, please, contact developers.</string>
 
   <!-- ChatModel.chatRunning interactions -->
   <string name="chat_is_stopped_indication">Chat wurde beendet</string>

apps/android/app/src/main/res/values-ru/strings.xml

@@ -682,6 +682,7 @@
     <string name="restore_database_alert_desc">Введите предыдущий пароль после восстановления резервной копии. Это действие нельзя отменить.</string>
     <string name="restore_database_alert_confirm">Восстановить</string>
     <string name="database_restore_error">Ошибка при восстановлении базы данных</string>
+    <string name="restore_passphrase_not_found_desc">Пароль не найден в Keystore, пожалуйста, введите его вручную. Это могло произойти, если вы восстановили данные приложения с помощью инструмента резервного копирования. Если это не так, пожалуйста, свяжитесь с разработчиками.</string>
 
     <!-- ChatModel.chatRunning interactions -->
     <string name="chat_is_stopped_indication">Чат остановлен</string>

apps/android/app/src/main/res/values/strings.xml

@@ -682,6 +682,7 @@
   <string name="restore_database_alert_desc">Please enter the previous password after restoring database backup. This action can not be undone.</string>
   <string name="restore_database_alert_confirm">Restore</string>
   <string name="database_restore_error">Restore database error</string>
+  <string name="restore_passphrase_not_found_desc">Passphrase not found in Keystore, please enter it manually. This may have happened if you restored the app\'s data using a backup tool. If it\'s not the case, please, contact developers.</string>
 
   <!-- ChatModel.chatRunning interactions -->
   <string name="chat_is_stopped_indication">Chat is stopped</string>