iOS 核心数据加密使用 NSValueTransformer

Question

我正在尝试使用 Core Data 和 CommonCrypto 加密数据。我正在尝试使用 NSValueTransformer 来延迟加密和解密。

但是，当我现在尝试将加密数据保存到持久性存储协调器时，它失败了。每次我尝试将我的数据保存到数据库时，它都会给我:

-[__NSCFString bytes]: unrecognized selector sent to instance

我确定这是某种数据库和 NSManagedObject 不匹配，但我无法弄清楚。我觉得这可能很简单，但我找不到解决方案。我的代码:

NSValueTransformer

class TryHardEncryption: NSValueTransformer {

override class func transformedValueClass() -> AnyClass {
    return NSString.self
}

override class func allowsReverseTransformation() -> Bool {
    return true
}


override func reverseTransformedValue(value: AnyObject?) -> AnyObject? {
    if let message = value as? NSString {
        let keyString        = "12345678901234567890123456789012"
        let keyData: NSData! = (keyString as NSString).dataUsingEncoding(NSUTF8StringEncoding) as NSData!
        let keyBytes         = UnsafeMutablePointer<Void>(keyData.bytes)
        print("keyLength   = \(keyData.length), keyData   = \(keyData)")

        let data: NSData! = (message as NSString).dataUsingEncoding(NSUTF8StringEncoding) as NSData!
        let dataLength    = size_t(data.length)
        let dataBytes     = UnsafeMutablePointer<Void>(data.bytes)
        print("dataLength  = \(dataLength), data      = \(data)")

        let cryptData    = NSMutableData(length: Int(dataLength) + kCCBlockSizeAES128)
        let cryptPointer = UnsafeMutablePointer<Void>(cryptData!.mutableBytes)
        let cryptLength  = size_t(cryptData!.length)

        let keyLength              = size_t(kCCKeySizeAES256)
        let operation: CCOperation = UInt32(kCCDecrypt)
        let algoritm:  CCAlgorithm = UInt32(kCCAlgorithmAES128)
        let options:   CCOptions   = UInt32(kCCOptionPKCS7Padding + kCCOptionECBMode)

        var numBytesEncrypted :size_t = 0

        let cryptStatus = CCCrypt(operation,
            algoritm,
            options,
            keyBytes, keyLength,
            nil,
            dataBytes, dataLength,
            cryptPointer, cryptLength,
            &numBytesEncrypted)

        if UInt32(cryptStatus) == UInt32(kCCSuccess) {
            //  let x: UInt = numBytesEncrypted
            cryptData!.length = Int(numBytesEncrypted)
            print("DecryptcryptLength = \(numBytesEncrypted), Decrypt = \(cryptData)")

            // Not all data is a UTF-8 string so Base64 is used
            let base64cryptString = cryptData!.base64EncodedStringWithOptions(.Encoding64CharacterLineLength)
            print("base64DecryptString = \(base64cryptString)")
            print( "utf8 actual string = \(NSString(data: cryptData!, encoding: NSUTF8StringEncoding))");
            return base64cryptString
        } else {
            print("Error: \(cryptStatus)")
        }
    }
    return nil
}

override func transformedValue(value: AnyObject?) -> AnyObject? {
    if let message = value as? NSString {
        let keyString        = "12345678901234567890123456789012"
        let keyData: NSData! = (keyString as NSString).dataUsingEncoding(NSUTF8StringEncoding) as NSData!
        let keyBytes         = UnsafePointer<UInt8>(keyData.bytes)
        print("keyLength   = \(keyData.length), keyData   = \(keyData)")

        let data: NSData! = message.dataUsingEncoding(NSUTF8StringEncoding) as NSData!
        let dataLength    = Int(data.length)
        let dataBytes     = UnsafePointer<UInt8>(data.bytes)
        print("dataLength  = \(dataLength), data      = \(data)")

        let cryptData    = NSMutableData(length: Int(dataLength) + kCCBlockSizeAES128)!
        let cryptPointer = UnsafeMutablePointer<UInt8>(cryptData.mutableBytes)
        let cryptLength  = size_t(cryptData.length)

        let keyLength              = size_t(kCCKeySizeAES256)
        let operation: CCOperation = UInt32(kCCEncrypt)
        let algoritm:  CCAlgorithm = UInt32(kCCAlgorithmAES128)
        let options:   CCOptions   = UInt32(kCCOptionECBMode + kCCOptionPKCS7Padding)

        var numBytesEncrypted :size_t = 0

        let cryptStatus = CCCrypt(operation,
            algoritm,
            options,
            keyBytes, keyLength,
            nil,
            dataBytes, dataLength,
            cryptPointer, cryptLength,
            &numBytesEncrypted)

        if UInt32(cryptStatus) == UInt32(kCCSuccess) {
            cryptData.length = Int(numBytesEncrypted)
            print("cryptLength = \(numBytesEncrypted), cryptData = \(cryptData)")

            // Not all data is a UTF-8 string so Base64 is used
            let base64cryptString = cryptData.base64EncodedStringWithOptions(.Encoding64CharacterLineLength)
            print("base64cryptString = \(base64cryptString)")
            return NSString(string: base64cryptString) as NSObject

        } else {
            print("Error: \(cryptStatus)")
        }
    }
    return nil
}

}

要让 NSValueTransformer 工作，我必须做的是:

let transformer: TryHardEncryption = TryHardEncryption()
    NSValueTransformer.setValueTransformer(transformer, forName: "TryHardEncryption")

如果没有上面的代码，NSValueTransformer 就不会被调用。

我已将数据库字段标记为可转换类型并将其命名为:TryHardEncryption。你们知道这里出了什么问题吗？

编辑它涉及的属性是:

@NSManaged var establishmentDescription: String?

当我调试它们时，加密和解密函数都返回一个字符串。

Answer 1

我终于弄明白了……我对每个对象必须是什么类型以及我的 nsvaluetransformer 必须返回什么感到困惑。我没有在 nsvaluetransformer 中将值转换为正确的类型，因此我在代码中返回了 nil。然而，它并没有以我很容易弄清楚的方式崩溃。其次，我将实体列改回 NSObject。在 transformedValue 方法中返回一个 NSData 对象，在 reverseTransformedValue 方法中返回一个 NSString。这实际上是我需要让它工作的全部。非常感谢你的帮助。这确实是一个类型错误。