基于iOS的NSValueTransformer核心数据加密

Question

我正在试验用核心数据和CommonCrypto加密数据。我正在尝试使用NSValueTransformer来懒惰地加密和解密。

但是，当我现在尝试将加密的数据保存到持久存储协调器时，它失败了。每次我试图将数据保存到数据库时，它都会给我：

-__NSCFString字节:发送到实例的不可识别的选择器

我确信这是某种数据库和NSManagedObject的错配，但我无法弄清楚。我觉得这可能很简单，但我找不到解决办法。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
}

}

为了让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，就不会调用NSValueTransformer。

我将数据库字段标记为可转换类型，并将其命名为: TryHardEncryption。你们知道这是怎么回事吗？

编辑它所涉及的属性是：

@NSManaged var establishmentDescription: String?

当我调试加密和解密函数时，它们都返回一个字符串。

Answer 1

我终于想出来了..。我搞不懂什么类型非常对象必须是什么，我的confused转换器必须返回什么。我没有将值转换成nil转换器中的适当类型，因此我在代码中返回了0。然而，它并没有崩溃的方式，我可以很容易地弄清楚这一点。其次，我将实体列更改为NSObject。在transformedValue方法中返回一个transformedValue对象，在reverseTransformedValue方法中返回一个NSString。实际上，这就是我要做的一切。非常感谢你的帮助。这确实是一个类型错误。

Answer 2

若要帮助任何想要查看更正代码示例的人，请将问题中transformedValue()的返回行替换为：return base64cryptString.dataUsingEncoding(NSUTF8StringEncoding)