android - EncryptedSharedPreferences isUserAuthenticationRequired 无法正常工作

Question

我正在使用 EncryptedSharedPreferences 来存储加密数据。

val biometricManager = BiometricManager.from(this)
val hasFingerprint = biometricManager.canAuthenticate() == BiometricManager.BIOMETRIC_SUCCESS

val advanceSpec = KeyGenParameterSpec.Builder(
    "master_key",
    KeyProperties.PURPOSE_ENCRYPT or KeyProperties.PURPOSE_DECRYPT
).apply {
    setBlockModes(KeyProperties.BLOCK_MODE_GCM)
    setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_NONE)
    setKeySize(256)
    if(hasFingerprint){
        setUserAuthenticationRequired(true)
        setUserAuthenticationValidityDurationSeconds(1)
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N){
            setInvalidatedByBiometricEnrollment(false)
        }
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.P){
            setIsStrongBoxBacked(true)
            setUserConfirmationRequired(true)
        }
    }
}.build()

val masterKey = MasterKeys.getOrCreate(advanceSpec)
val preferences = EncryptedSharedPreferences.create(
    "TestPreferences",
    masterKey,
    applicationContext,
    EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
    EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
)

实际上，我错过了 BiometricPrompt 部分。我以为打电话 setUserAuthenticationRequired(true)将自动处理验证用户。但我们必须自己展示 BiometricPrompt。 isUserAuthenticationRequired only 确保只有在用户获得授权时才会激活 key 。

val biometricPrompt = BiometricPrompt(
            activity,
            ContextCompat.getMainExecutor(activity),
            object: BiometricPrompt.AuthenticationCallback() {
                override fun onAuthenticationSucceeded(result: BiometricPrompt.AuthenticationResult) {
                    super.onAuthenticationSucceeded(result)
                    createSharedPreferences()
                }
            }
        )

        biometricPrompt.authenticate(promptInfo)

但有个问题。它只在创建 EncryptedSharedPreferences 时抛出 UserNotAuthenticatedException .之后，我们可以根据需要执行读写操作。它没有考虑 setUserAuthenticationValidityDurationSeconds(1) .

Answer 1

我找到了 1 秒后不需要身份验证的原因。这是因为，一旦启动了加密共享首选项，它就会加载用于加密和解密内存中数据的 key ，然后这些 key 用于访问文件中的数据。你可以阅读里面的代码EncryptedSharedPreference类(class)。这是很明显的。

KeysetHandle daeadKeysetHandle = new AndroidKeysetManager.Builder()
                .withKeyTemplate(prefKeyEncryptionScheme.getKeyTemplate())
                .withSharedPref(context, KEY_KEYSET_ALIAS, fileName)
                .withMasterKeyUri(KEYSTORE_PATH_URI + masterKeyAlias)
                .build().getKeysetHandle();
        KeysetHandle aeadKeysetHandle = new AndroidKeysetManager.Builder()
                .withKeyTemplate(prefValueEncryptionScheme.getKeyTemplate())
                .withSharedPref(context, VALUE_KEYSET_ALIAS, fileName)
                .withMasterKeyUri(KEYSTORE_PATH_URI + masterKeyAlias)
                .build().getKeysetHandle();

        DeterministicAead daead = daeadKeysetHandle.getPrimitive(DeterministicAead.class);
        Aead aead = aeadKeysetHandle.getPrimitive(Aead.class);

        return new EncryptedSharedPreferences(fileName, masterKeyAlias,
                context.getSharedPreferences(fileName, Context.MODE_PRIVATE), aead, daead);