使用 EncryptedSharedPreferences 获取 KeyStoreException 和 GeneralSecurityException，我该如何解决？

Question

背景

在我开发的一个应用程序中，我将重要的东西（令牌）存储到 EncryptedSharedPreferences（取自 here 和 here）：

/** a hardware-encrypted based shared preference (for the values).
 * Note that it is a bit slow, so it's better to always use it in a background thread.
 * Also, avoid having it being backed-up in the manifest, as it's hardware based and will become useless: https://stackoverflow.com/a/63795282/878126*/
object SecuredSharedPreferences {
    private var cachedDefaultSharedPreferences: SharedPreferences? = null

    /**warning: using this function can take some time (249 ms on Pixel 4, for example). Very recommended to avoid calling it on UI thread */
    @WorkerThread
    fun getDefaultSecuredSharedPreferences(context: Context): SharedPreferences {
        if (cachedDefaultSharedPreferences != null)
            return cachedDefaultSharedPreferences!!
        synchronized(this) {
            if (cachedDefaultSharedPreferences != null)
                return cachedDefaultSharedPreferences!!
            cachedDefaultSharedPreferences = getSecuredSharedPreferences(context, context.packageName + "_secured_preferences")
        }
        return cachedDefaultSharedPreferences!!
    }

    @WorkerThread
    private fun getSecuredSharedPreferences(context: Context, fileName: String): SharedPreferences {
        val masterKey = MasterKey.Builder(context, MasterKey.DEFAULT_MASTER_KEY_ALIAS).setKeyScheme(MasterKey.KeyScheme.AES256_GCM).build()
        return EncryptedSharedPreferences.create(context, fileName, masterKey,
                EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
                EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
        )
    }
}

分级：

implementation 'androidx.security:security-crypto:1.1.0-alpha03'

问题

我注意到在使用此代码时通过 Crashlytics 报告了 2 个错误（报告为 here）：

1. 第一个是MasterKey.Builder 的GeneralSecurityException 行：

Fatal Exception: java.security.GeneralSecurityException: Keystore operation failed
       at androidx.security.crypto.MasterKeys.generateKey(MasterKeys.java:146)
       at androidx.security.crypto.MasterKeys.getOrCreate(MasterKeys.java:97)
       at androidx.security.crypto.MasterKey$Builder.buildOnM(MasterKey.java:357)
       at androidx.security.crypto.MasterKey$Builder.build(MasterKey.java:314)
...
Caused by java.security.ProviderException: Keystore operation failed
       at android.security.keystore.AndroidKeyStoreKeyGeneratorSpi.engineGenerateKey(AndroidKeyStoreKeyGeneratorSpi.java:372)
       at javax.crypto.KeyGenerator.generateKey(KeyGenerator.java:612)
       at androidx.security.crypto.MasterKeys.generateKey(MasterKeys.java:142)
       at androidx.security.crypto.MasterKeys.getOrCreate(MasterKeys.java:97)
       at androidx.security.crypto.MasterKey$Builder.buildOnM(MasterKey.java:357)
       at androidx.security.crypto.MasterKey$Builder.build(MasterKey.java:314)

1. 第二个出现在KeyStoreException 的EncryptedSharedPreferences.create 行，出现频率更高，用户也更多：

Fatal Exception: java.security.KeyStoreException: the master key android-keystore://_androidx_security_master_key_ exists but is unusable
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.readOrGenerateNewMasterKey(AndroidKeysetManager.java:275)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.build(AndroidKeysetManager.java:236)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:155)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:120)
...
Caused by java.security.UnrecoverableKeyException: Failed to obtain information about key
       at android.security.keystore.AndroidKeyStoreProvider.loadAndroidKeyStoreSecretKeyFromKeystore(AndroidKeyStoreProvider.java:282)
       at android.security.keystore.AndroidKeyStoreSpi.engineGetKey(AndroidKeyStoreSpi.java:98)
       at java.security.KeyStore.getKey(KeyStore.java:825)
       at com.google.crypto.tink.integration.android.AndroidKeystoreAesGcm.<init>(AndroidKeystoreAesGcm.java:58)
       at com.google.crypto.tink.integration.android.AndroidKeystoreKmsClient.getAead(AndroidKeystoreKmsClient.java:164)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.readOrGenerateNewMasterKey(AndroidKeysetManager.java:267)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.build(AndroidKeysetManager.java:236)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:155)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:120)

编辑：似乎还有更多类型的例外：

1. InvalidProtocolBufferException：

Fatal Exception: com.google.crypto.tink.shaded.protobuf.InvalidProtocolBufferException: Protocol message contained an invalid tag (zero).
       at com.google.crypto.tink.shaded.protobuf.GeneratedMessageLite.parsePartialFrom(GeneratedMessageLite.java:1566)
       at com.google.crypto.tink.shaded.protobuf.GeneratedMessageLite.parseFrom(GeneratedMessageLite.java:1663)
       at com.google.crypto.tink.proto.Keyset.parseFrom(Keyset.java:957)
       at com.google.crypto.tink.integration.android.SharedPrefKeysetReader.read(SharedPrefKeysetReader.java:84)
       at com.google.crypto.tink.CleartextKeysetHandle.read(CleartextKeysetHandle.java:58)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.read(AndroidKeysetManager.java:328)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.readOrGenerateNewKeyset(AndroidKeysetManager.java:287)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.build(AndroidKeysetManager.java:238)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:160)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:120)

4. NullPointerException：

Fatal Exception: java.lang.NullPointerException: Attempt to invoke interface method 'android.security.keymaster.OperationResult android.security.IKeystoreService.begin(android.os.IBinder, java.lang.String, int, boolean, android.security.keymaster.KeymasterArguments, byte[], int)' on a null object reference
       at android.security.KeyStore.begin(KeyStore.java:501)
       at android.security.keystore.AndroidKeyStoreCipherSpiBase.ensureKeystoreOperationInitialized(AndroidKeyStoreCipherSpiBase.java:248)
       at android.security.keystore.AndroidKeyStoreCipherSpiBase.engineInit(AndroidKeyStoreCipherSpiBase.java:109)
       at javax.crypto.Cipher.tryTransformWithProvider(Cipher.java:2977)
       at javax.crypto.Cipher.tryCombinations(Cipher.java:2884)
       at javax.crypto.Cipher$SpiAndProviderUpdater.updateAndGetSpiAndProvider(Cipher.java:2789)
       at javax.crypto.Cipher.chooseProvider(Cipher.java:956)
       at javax.crypto.Cipher.init(Cipher.java:1199)
       at javax.crypto.Cipher.init(Cipher.java:1143)
       at com.google.crypto.tink.integration.android.AndroidKeystoreAesGcm.encryptInternal(AndroidKeystoreAesGcm.java:84)
       at com.google.crypto.tink.integration.android.AndroidKeystoreAesGcm.encrypt(AndroidKeystoreAesGcm.java:72)
       at com.google.crypto.tink.integration.android.AndroidKeystoreKmsClient.validateAead(AndroidKeystoreKmsClient.java:248)
       at com.google.crypto.tink.integration.android.AndroidKeystoreKmsClient.getAead(AndroidKeystoreKmsClient.java:165)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.readOrGenerateNewMasterKey(AndroidKeysetManager.java:267)
       at com.google.crypto.tink.integration.android.AndroidKeysetManager$Builder.build(AndroidKeysetManager.java:236)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:155)
       at androidx.security.crypto.EncryptedSharedPreferences.create(EncryptedSharedPreferences.java:120)

我尝试过的

在互联网上搜索，我发现只有第一个异常 (GeneralSecurityException) 的线索，这可能是自定义 ROM 发生的，因为它们可能无法很好地实现用于加密的硬件密钥。

事实上，查看 Crashlytics 上的设备，查看每个设备的 Android 版本，我发现它们领先于我所看到的支持它们的最新版本。

对于第二个例外，遗憾的是，我找不到任何解释，也没有解决方案。我认为这可能与应用程序的恢复有关，但这很奇怪，因为它经常发生。在reddit（here）上，有人写道，遇到这种异常，他选择了wrap the initialization of EncryptedSharedPreferences with "clear all data if fails" and bite the bullet。还建议它可能与禁用android:allowBackup 有关（确实如此）。

其他的就不知道了。

问题

为什么会出现这些异常？我能对他们做什么？

清除数据是唯一可以做的事情吗？我什至不确定它是否真的有帮助，因为如果我选择拥有它，这意味着每次它即将发生时崩溃报告都会消失......

是否与android:allowBackup被禁用有关？

Answer 1

在使用 Jetpack Security EncryptedSharedPreferences（甚至是稳定的）之前请注意这个活动故障，它主要来自外来设备 - https://issuetracker.google.com/issues/176215143?pli=1

唯一肮脏的解决方法是 - https://github.com/google/tink/issues/535#issuecomment-912661574

一旦找到友好的解决方案，我会更新答案。这是解决方法-

/**
 * A builder for creating an encrypted shared preference class.
 */
private const val KEYSTORE_PROVIDER = "AndroidKeyStore"
private const val SHARED_PREFS_FILENAME = "TVPrefs"

@KoinApiExtension
class EncryptedSharedPreferenceBuilder(var context: Context) : KoinComponent {
    private val reporter: Reporter by inject()

    private val masterKeyAlias =
        MasterKey.Builder(context).setKeyScheme(MasterKey.KeyScheme.AES256_GCM).build()

    fun build(): SharedPreferences {
        return try {
            createSharedPreferences()
        } catch (gsException: GeneralSecurityException) {
            reporter.logException(gsException)
            Timber.d("EncryptedSharedPref: Error occurred while create shared pref=$gsException")
            // There's not much point in keeping data you can't decrypt anymore,
            // delete & re-create; user has to start from scratch
            deleteSharedPreferences()
            createSharedPreferences()
        }
    }

    private fun createSharedPreferences() = EncryptedSharedPreferences.create(
        context,
        SHARED_PREFS_FILENAME,
        masterKeyAlias,
        EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
        EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
    )

    // Clearing getSharedPreferences using default Preference wrapper.
    // This is to work around any key-mismatches that may happen.
    fun clearSharedPreference() {
        context.getSharedPreferences(SHARED_PREFS_FILENAME, Context.MODE_PRIVATE).edit().clear()
            .apply()
    }

    // Workaround [https://github.com/google/tink/issues/535#issuecomment-912170221]
    // Issue Tracker - https://issuetracker.google.com/issues/176215143?pli=1
    private fun deleteSharedPreferences() {
        try {
            val sharedPrefsFile =
                File("${context.filesDir.parent}/shared_prefs/$SHARED_PREFS_FILENAME.xml")

            // Clear the encrypted prefs
            clearSharedPreference()

            // Delete the encrypted prefs file
            if (sharedPrefsFile.exists()) {
                val deleted = sharedPrefsFile.delete()
                Timber.d("EncryptedSharedPref: Shared pref file deleted=$deleted; path=${sharedPrefsFile.absolutePath}")
            } else {
                Timber.d("EncryptedSharedPref: Shared pref file non-existent; path=${sharedPrefsFile.absolutePath}")
            }

            // Delete the master key
            val keyStore = KeyStore.getInstance(KEYSTORE_PROVIDER)
            keyStore.load(null)
            keyStore.deleteEntry(MasterKey.DEFAULT_MASTER_KEY_ALIAS)
        } catch (e: Exception) {
            Timber.d("EncryptedSharedPref:  Error occurred while trying to reset shared pref=$e")
        }
    }
}

Answer 2

我认为您关于android:allowBackup=false 是罪魁祸首的直觉是正确的。我遇到了类似的问题（当 allowBackup 设置为 false 时，加密的共享首选项在应用更新时引发错误）。在我的情况下，我设法通过安装、登录（设置加密首选项）然后更新到更新版本的应用程序并尝试读取首选项来重现。我最终通过删除 android:allowBackup=false

解决了这个问题