Question

我在使用SWIFT 3进行加密和解密时遇到了奇怪的行为我正在使用以下方法来加密和解密一个字符串。虽然加密我生成一个随机盐并将其添加到加密数据的末尾，而在解密时我正从数据中读取IV数据来解密并执行解密操作

internal func cryptography(_ inputData: Data, key: String, operation: CCOperation) -> Data? {

    //prepare the Key
    let keyData: Data!    = key.data(using: String.Encoding.utf8, allowLossyConversion: false)!
    let keyBytes          = keyData.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
        return bytes
    }
    let keyLength        = size_t(kCCKeySizeAES128)

    //Prepare the input data

    //Check whether this is encryption , if so generate a random  IV and append this to the encrypted data
    let ivBuffer:UnsafePointer<UInt8>?
    let dataBytes: UnsafePointer<UInt8>?
    var dataLength :Int? = 0
    var ivData :Data? = nil
    if (operation == CCOperation(kCCEncrypt)){

        ivData = self.generateIV()
        ivBuffer = (ivData == nil) ? nil : ivData!.withUnsafeBytes({ (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
            return bytes
        })
        dataBytes        = inputData.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
            return bytes
        }
        dataLength = Int(inputData.count)
    }
    else{

        //for decryption the last 16 bytes will be the IV so extract it
        var dataToProcess  = inputData
        let rangStart = inputData.count - kCCBlockSizeAES128
        let rangeEnd = rangStart + kCCBlockSizeAES128
        var range = Range(rangStart..<rangeEnd)
        ivData = inputData.subdata(in:range)
        ivBuffer = ivData?.withUnsafeBytes({ (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
            return bytes
        })

        range = Range(0..<rangStart)
        dataToProcess = inputData.subdata(in: range)
        dataBytes        = dataToProcess.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
            return bytes
        }
        dataLength = Int(dataToProcess.count)
    }


    //Calculate buffer details
    var bufferData       = Data(count: Int(dataLength!) + kCCBlockSizeAES128)
    let bufferPointer    = bufferData.withUnsafeMutableBytes { (bytes: UnsafeMutablePointer<UInt8>) -> UnsafeMutablePointer<UInt8> in
        return bytes
    }
    let bufferLength     = size_t(bufferData.count)


    var bytesDecrypted   = Int(0)
    let tst = CCCryptorStatus()
    let cryptStatus = CCCrypt(
        operation,                      // Operation
        CCAlgorithm(kCCAlgorithmAES128),   // Algorithm is AES
        CCOptions(kCCOptionPKCS7Padding), //options
        keyBytes,                       // key data
        keyLength,                      // key length
        ivBuffer,                            // IV buffer
        dataBytes,                      // input data
        dataLength!,                     // input length
        bufferPointer,                  // output buffer
        bufferLength,                   // output buffer length
        &bytesDecrypted)                // output bytes decrypted real length
    if Int32(cryptStatus) == Int32(kCCSuccess) {
        bufferData.count = bytesDecrypted // Adjust buffer size to real bytes




        if (operation == CCOperation(kCCEncrypt)){

            bufferData.append(ivData!)
        }
        return bufferData as Data
    } else {
        print("Error in crypto operation: \(cryptStatus)")
        return nil
    }
}

现在出现了奇怪的行为。我两次调用此方法，首先用于加密，第二次用于解密从前一次调用返回的加密字符串。

现在如果我运行此代码然后加密将成功发生，但解密返回无效数据 - 这里的cryptStatus成功但bytesDecrypted显示为16并且转换此tostring返回nil。

现在奇怪的是，如果我在加密的else部分放置一个断点（即从加密的String中提取IV的方法），即在下面的最后一行，那么如果使用po打印dataToProcess和ivData到console，然后解密正确发生。

//for decryption the last 16 bytes will be the IV so extract it
    var dataToProcess  = inputData
    let rangStart = inputData.count - kCCBlockSizeAES128
    let rangeEnd = rangStart + kCCBlockSizeAES128
    var range = Range(rangStart..<rangeEnd)
    ivData = inputData.subdata(in:range)
    ivBuffer = ivData?.withUnsafeBytes({ (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
        return bytes
    })

    range = Range(0..<rangStart)
    dataToProcess = inputData.subdata(in: range)
    dataBytes        = dataToProcess.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
        return bytes
    }
    dataLength = Int(dataToProcess.count)

对这种奇怪的行为有任何想法。我是否需要进行任何重置或延迟？

Answer 1

您的代码中有什么不好用withUnsafeBytes或withUnsafeMutableBytes的所有这些用法：

    let keyBytes          = keyData.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) -> UnsafePointer<UInt8> in
        return bytes
    }

检查withUnsafeBytes的参考：

withUnsafeBytes(_:)

警告

不应在闭包调用的生命周期之外存储和使用字节指针参数。

（您可以为withUnsafeMutableBytes找到相同的警告。）

withUnsafeBytes或withUnsafeMutableBytes的所有用法都将指针参数置于闭包之外，这可能会导致任何意外行为，包括崩溃。

withUnsafeBytes或withUnsafeMutableBytes的正确用法是这样的：

func cryptography(_ inputData: Data, key: String, operation: CCOperation) -> Data? {

    //prepare the Key
    let keyData = key.data(using: .utf8, allowLossyConversion: false)!
    let keyLength = kCCKeySizeAES128

    //Prepare the input data

    //Check whether this is encryption , if so generate a random  IV and append this to the encrypted data
    let ivData :Data
    let data: Data
    if operation == CCOperation(kCCEncrypt) {
        ivData = self.generateIV()
        data = inputData
    } else {
        //for decryption the last 16 bytes will be the IV so extract it
        let rangStart = inputData.count - kCCBlockSizeAES128
        let rangeEnd = inputData.count
        ivData = inputData.subdata(in: rangStart..<rangeEnd)
        data = inputData.subdata(in: 0..<rangStart)
    }
    let dataLength = data.count

    //Calculate buffer details
    var bufferData       = Data(count: dataLength + kCCBlockSizeAES128)
    let bufferLength     = bufferData.count

    var bytesDecrypted   = 0
    let cryptStatus = keyData.withUnsafeBytes {keyBytes in
        ivData.withUnsafeBytes {ivBuffer in
            data.withUnsafeBytes {dataBytes in
                bufferData.withUnsafeMutableBytes {bufferPointer in
                    CCCrypt(
                        operation,                      // Operation
                        CCAlgorithm(kCCAlgorithmAES128),   // Algorithm is AES
                        CCOptions(kCCOptionPKCS7Padding), //options
                        keyBytes,                       // key data
                        keyLength,                      // key length
                        ivBuffer,                            // IV buffer
                        dataBytes,                      // input data
                        dataLength,                     // input length
                        bufferPointer,                  // output buffer
                        bufferLength,                   // output buffer length
                        &bytesDecrypted)                // output bytes decrypted real length
                }
            }
        }
    }

    if cryptStatus == Int32(kCCSuccess) {
        bufferData.count = bytesDecrypted // Adjust buffer size to real bytes
        if operation == CCOperation(kCCEncrypt) {
            bufferData.append(ivData)
        }
        return bufferData
    } else {
        print("Error in crypto operation: \(cryptStatus)")
        return nil
    }
}

CCCrypt iOS Swift 3中的奇怪行为

1 个答案:

警告