Xamarin.iOS / Akavache - 带有自定义 EncryptionProvider 的加密缓存

Question

我有一个 Xamarin.iOS 应用程序使用 Akavache 来缓存数据并减少对服务器不必要的数据请求的数量。使用 BlobCache.LocalMachine 一切都如预期的那样运行良好，喜欢它。

现在我想确保静态数据已加密。通过研究这个和在线阅读文档，我发现默认实现实际上并没有加密 iOS 上的缓存，我实际上需要提供 IEncryptionProvider 的自定义实现。

我关注了这篇文章：http://kent-boogaart.com/blog/password-protected-encryption-provider-for-akavache

从该线程添加输入：https://github.com/akavache/Akavache/issues/190

最后实现了这个：

    public interface IPasswordProtectedEncryptionProvider : IEncryptionProvider
    {
        void SetPassword(string password);
    }

    public sealed class MyEncryptionProvider : IPasswordProtectedEncryptionProvider
    {
        static readonly byte[] salt = Encoding.ASCII.GetBytes("dVBZMQWyFRcJOIas");
        readonly IScheduler scheduler;
        readonly SymmetricAlgorithm symmetricAlgorithm;
        ICryptoTransform decryptTransform;
        ICryptoTransform encryptTransform;

        public MyEncryptionProvider()
        {
            scheduler = BlobCache.TaskpoolScheduler ?? throw new ArgumentNullException(nameof(scheduler), "Scheduler instance is null");
            symmetricAlgorithm = new RijndaelManaged();
            var securePassword = "kadhaskdhsakhaskjdhaskjdhaskdjashdkjahkfghkjhew";
            SetPassword(securePassword);
        }

        public void SetPassword(string password)
        {
            if(password == null)
               throw new ArgumentNullException(nameof(password), "password can't be null");

            var derived = new Rfc2898DeriveBytes(password, salt);
            var bytesForKey = symmetricAlgorithm.KeySize / 8;
            var bytesForIV = symmetricAlgorithm.BlockSize / 8;
            symmetricAlgorithm.Key = derived.GetBytes(bytesForKey);
            symmetricAlgorithm.IV = derived.GetBytes(bytesForIV);
            decryptTransform = symmetricAlgorithm.CreateDecryptor(symmetricAlgorithm.Key, symmetricAlgorithm.IV);
            encryptTransform = symmetricAlgorithm.CreateEncryptor(symmetricAlgorithm.Key, symmetricAlgorithm.IV);
        }

        public IObservable<byte[]> DecryptBlock(byte[] block)
        {
            if (block == null)
            {
                throw new ArgumentNullException(nameof(block), "block can't be null");
            }

            if (decryptTransform == null)
            {
                return Observable.Throw<byte[]>(new InvalidOperationException("You must call SetPassword first."));
            }

            return Observable.Start(() => InMemoryTransform(block, decryptTransform), scheduler);
        }

        public IObservable<byte[]> EncryptBlock(byte[] block)
        {
            if (block == null)
            {
                throw new ArgumentNullException(nameof(block), "block can't be null");
            }

            if (encryptTransform == null)
            {
                return Observable.Throw<byte[]>(new InvalidOperationException("You must call SetPassword first."));
            }

            return Observable.Start(() => InMemoryTransform(block, encryptTransform), scheduler);
        }

        static byte[] InMemoryTransform(byte[] bytesToTransform, ICryptoTransform transform)
        {
            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, transform, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(bytesToTransform, 0, bytesToTransform.Length);
                }

                return memoryStream.ToArray();
            }
        }
    }

我这样注册这个实现： Locator.CurrentMutable.RegisterConstant(new MyEncryptionProvider(), typeof(IEncryptionProvider)); 在调用 BlobCache.Secure

之前

当我在该安全缓存上使用 .GetOrFetchObject 时，我看到 EncryptBlock 和 DecryptBlock 被调用。到目前为止，一切都很好。

我运行遇到的问题是在尝试反序列化时失败 Newtonsoft:

{Newtonsoft.Json.JsonReaderException: Read past end of current container context. Path ''.
  at Newtonsoft.Json.Bson.BsonReader.ReadNormal () [0x0013c] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.Bson.BsonReader.Read () [0x00033] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.JsonReader.ReadAndAssert () [0x00000] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject (Newtonsoft.Json.JsonReader reader, System.Type objectType, Newtonsoft.Json.Serialization.JsonContract contract, Newtonsoft.Json.Serialization.JsonProperty member, Newtonsoft.Json.Serialization.JsonContainerContract containerContract, Newtonsoft.Json.Serialization.JsonProperty containerMember, System.Object existingValue) [0x000b6] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateValueInternal (Newtonsoft.Json.JsonReader reader, System.Type objectType, Newtonsoft.Json.Serialization.JsonContract contract, Newtonsoft.Json.Serialization.JsonProperty member, Newtonsoft.Json.Serialization.JsonContainerContract containerContract, Newtonsoft.Json.Serialization.JsonProperty containerMember, System.Object existingValue) [0x0006d] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize (Newtonsoft.Json.JsonReader reader, System.Type objectType, System.Boolean checkAdditionalContent) [0x000db] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.JsonSerializer.DeserializeInternal (Newtonsoft.Json.JsonReader reader, System.Type objectType) [0x00053] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.JsonSerializer.Deserialize (Newtonsoft.Json.JsonReader reader, System.Type objectType) [0x00000] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Newtonsoft.Json.JsonSerializer.Deserialize[T] (Newtonsoft.Json.JsonReader reader) [0x00000] in <c19705166c7c4a608e182e859c4de6d2>:0 
  at Akavache.Sqlite3.SQLitePersistentBlobCache.DeserializeObject[T] (System.Byte[] data) [0x00074] in <67aced6c5c1a4c15b03e120d7300429d>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.12.0.20/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151 
  at System.Reactive.PlatformServices.ExceptionServicesImpl.Rethrow (System.Exception exception) [0x00006] in <427ee2007f4d40bb9d3f1fcd73e9b750>:0 
  at System.Reactive.ExceptionHelpers.ThrowIfNotNull (System.Exception exception) [0x0000d] in <ab76b1b1678341d69f8fc2c1f68d0bf5>:0 
  at System.Reactive.Subjects.AsyncSubject`1[T].GetResult () [0x00039]

当使用 BlobCache.LocalMachine 缓存相同的对象时，相同的数据结构成功存储如下：

[
  {
    "Name": "John Smith",
    "Date": "2017-04-03T20:00:00-04:00",
    "Number1": -8820768.6192349959,
    "Number2": -25540081.8275,
    "Number3": -0.0045255076670528034,
    "Number4": 0.0457761358483606,
    "RelatedObjects": [],
    "LastUpdateTime": "2017-04-04T17:36:06.247-04:00"
  }
]

我在这里错过了什么？非常沮丧，真的希望有人看到我没有看到的东西。感谢您的帮助。

Answer 1

借助此 post 中的示例：

我能够解决这个问题，这里的示例解决方案中显示了一个工作示例：https://github.com/dmitrysamuylov/xamarin-ios-akavache-secure-example

希望对以后的人有所帮助

Xamarin.iOS / Akavache - 带有自定义 EncryptionProvider 的加密缓存

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