在 Swift 3 中创建 UnsafeMutablePointer<UInt8>

Question

我正在将客户端应用程序从 Swift 2 更新到 Swift 3，并且我正在处理 commonCrypto（哎呀！）。

我正在尝试转换一个 DES 加密函数，但我不知道如何替换这段代码：

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

获取cryptPointer的正确方法是什么？到目前为止，我正在尝试：

var cryptData = Data(count: Int(dataLength) + kCCBlockSizeDES)
let cryptPointer = UnsafeMutablePointer<UInt8>.allocate(capacity: cryptData.count)
cryptData.copyBytes(to: cryptPointer, count: cryptData.count)

但我无法正确加密和解​​密。

请注意，我需要指针变量，因为它是 CCCrypt 函数参数之一

Answer 1

（DES 不安全，不应在新工作中使用；它已被 AES 取代）

示例片段：

let cryptLength = size_t(data.count + kCCBlockSizeDES)
var cryptData = Data(repeating:0, count:cryptLength)
var numBytesEncrypted :size_t = 0

let keyLength             = size_t(kCCKeySizeDES)
let algoritm: CCAlgorithm = UInt32(kCCAlgorithmDES)
let options:  CCOptions   = UInt32(kCCOptionPKCS7Padding)

let cryptStatus = cryptData.withUnsafeMutableBytes {cryptBytes in
    data.withUnsafeBytes {dataBytes in
        ivData.withUnsafeBytes {ivBytes in
            keyData.withUnsafeBytes {keyBytes in
                CCCrypt(CCOperation(operation),
                        algoritm,
                        options,
                        keyBytes, keyLength,
                        ivBytes,
                        dataBytes, data.count,
                        cryptBytes, cryptLength,
                        &numBytesEncrypted)
            }
        }
    }
}

日落文档部分的示例：

CBC 模式下的 AES 加密，带有随机 IV (Swift 3+)

iv 是加密数据的前缀

aesCBC128Encrypt 将创建一个随机 IV 并作为加密代码的前缀。
aesCBC128Decrypt 将在解密期间使用前缀 IV。

输入是数据，键是数据对象。如果需要在调用方法中转换为和/或从编码形式（如 Base64）。

密钥的长度应为 128 位（16 字节）、192 位（24 字节）或 256 位（32 字节）。如果使用其他密钥大小，则会引发错误。

PKCS#7 padding是默认设置的。

此示例需要 Common Crypto
项目必须有桥接头：
#import <CommonCrypto/CommonCrypto.h>
将Security.framework 添加到项目中。

这是示例，不是生产代码。

enum AESError: Error {
    case KeyError((String, Int))
    case IVError((String, Int))
    case CryptorError((String, Int))
}

// The iv is prefixed to the encrypted data
func aesCBCEncrypt(data:Data, keyData:Data) throws -> Data {
    let keyLength = keyData.count
    let validKeyLengths = [kCCKeySizeAES128, kCCKeySizeAES192, kCCKeySizeAES256]
    if (validKeyLengths.contains(keyLength) == false) {
        throw AESError.KeyError(("Invalid key length", keyLength))
    }

    let ivSize = kCCBlockSizeAES128;
    let cryptLength = size_t(ivSize + data.count + kCCBlockSizeAES128)
    var cryptData = Data(count:cryptLength)

    let status = cryptData.withUnsafeMutableBytes {ivBytes in
        SecRandomCopyBytes(kSecRandomDefault, kCCBlockSizeAES128, ivBytes)
    }
    if (status != 0) {
        throw AESError.IVError(("IV generation failed", Int(status)))
    }

    var numBytesEncrypted :size_t = 0
    let options   = CCOptions(kCCOptionPKCS7Padding)

    let cryptStatus = cryptData.withUnsafeMutableBytes {cryptBytes in
        data.withUnsafeBytes {dataBytes in
            keyData.withUnsafeBytes {keyBytes in
                CCCrypt(CCOperation(kCCEncrypt),
                        CCAlgorithm(kCCAlgorithmAES),
                        options,
                        keyBytes, keyLength,
                        cryptBytes,
                        dataBytes, data.count,
                        cryptBytes+kCCBlockSizeAES128, cryptLength,
                        &numBytesEncrypted)
            }
        }
    }

    if UInt32(cryptStatus) == UInt32(kCCSuccess) {
        cryptData.count = numBytesEncrypted + ivSize
    }
    else {
        throw AESError.CryptorError(("Encryption failed", Int(cryptStatus)))
    }

    return cryptData;
}

// The iv is prefixed to the encrypted data
func aesCBCDecrypt(data:Data, keyData:Data) throws -> Data? {
    let keyLength = keyData.count
    let validKeyLengths = [kCCKeySizeAES128, kCCKeySizeAES192, kCCKeySizeAES256]
    if (validKeyLengths.contains(keyLength) == false) {
        throw AESError.KeyError(("Invalid key length", keyLength))
    }

    let ivSize = kCCBlockSizeAES128;
    let clearLength = size_t(data.count - ivSize)
    var clearData = Data(count:clearLength)

    var numBytesDecrypted :size_t = 0
    let options   = CCOptions(kCCOptionPKCS7Padding)

    let cryptStatus = clearData.withUnsafeMutableBytes {cryptBytes in
        data.withUnsafeBytes {dataBytes in
            keyData.withUnsafeBytes {keyBytes in
                CCCrypt(CCOperation(kCCDecrypt),
                        CCAlgorithm(kCCAlgorithmAES128),
                        options,
                        keyBytes, keyLength,
                        dataBytes,
                        dataBytes+kCCBlockSizeAES128, clearLength,
                        cryptBytes, clearLength,
                        &numBytesDecrypted)
            }
        }
    }

    if UInt32(cryptStatus) == UInt32(kCCSuccess) {
        clearData.count = numBytesDecrypted
    }
    else {
        throw AESError.CryptorError(("Decryption failed", Int(cryptStatus)))
    }

    return clearData;
}

示例用法：

let clearData = "clearData0123456".data(using:String.Encoding.utf8)!
let keyData   = "keyData890123456".data(using:String.Encoding.utf8)!
print("clearData:   \(clearData as NSData)")
print("keyData:     \(keyData as NSData)")

var cryptData :Data?
do {
    cryptData = try aesCBCEncrypt(data:clearData, keyData:keyData)
    print("cryptData:   \(cryptData! as NSData)")
}
catch (let status) {
    print("Error aesCBCEncrypt: \(status)")
}

let decryptData :Data?
do {
    let decryptData = try aesCBCDecrypt(data:cryptData!, keyData:keyData)
    print("decryptData: \(decryptData! as NSData)")
}
catch (let status) {
    print("Error aesCBCDecrypt: \(status)")
}

示例输出：

clearData:   <636c6561 72446174 61303132 33343536>
keyData:     <6b657944 61746138 39303132 33343536>
cryptData:   <92c57393 f454d959 5a4d158f 6e1cd3e7 77986ee9 b2970f49 2bafcf1a 8ee9d51a bde49c31 d7780256 71837a61 60fa4be0>
decryptData: <636c6561 72446174 61303132 33343536>

注意事项：
CBC 模式示例代码的一个典型问题是，它将随机 IV 的创建和共享留给用户。此示例包括生成 IV、为加密数据添加前缀并在解密期间使用前缀 IV。这将临时用户从CBC mode 所需的详细信息中解放出来。

为了安全起见，加密数据也应该具有身份验证，此示例代码不提供此功能，以便更小并允许与其他平台更好的互操作性。

还缺少从密码中导出密钥的密钥，建议使用PBKDF2，将文本密码用作密钥材料。

有关强大的生产就绪多平台加密代码，请参阅RNCryptor。