Create UnsafeMutablePointer<UInt8> in Swift 3 - swift

Question

I'm updating from Swift 2 to Swift 3 an app for a client and I'm dealing with commonCrypto (yikes!).
I'm trying to convert a DES encryption function but I don't know hoy to replace this piece of code:
let cryptData: NSMutableData! = NSMutableData(length: Int(dataLength) + kCCBlockSizeDES)
let cryptPointer = UnsafeMutablePointer<UInt8>(cryptData.mutableBytes)
What's the right way to get cryptPointer? So far, I'm trying:
var cryptData = Data(count: Int(dataLength) + kCCBlockSizeDES)
let cryptPointer = UnsafeMutablePointer<UInt8>.allocate(capacity: cryptData.count)
cryptData.copyBytes(to: cryptPointer, count: cryptData.count)
But I can't manage to encrypt and decrypt correctly.
Note that I need the pointer var because it's one of the CCCrypt function parameters

Answer 1

(DES is not secure and should not be used in new work; it has been superceed by AES)
Example fragment:
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)
}
}
}
}
Example from sunsetted documentation section:
AES encryption in CBC mode with a random IV (Swift 3+)
The iv is prefixed to the encrypted data
aesCBC128Encrypt will create a random IV and prefixed to the encrypted code.
aesCBC128Decrypt will use the prefixed IV during decryption.
Inputs are the data and key are Data objects. If an encoded form such as Base64 if required convert to and/or from in the calling method.
The key should be exactly 128-bits (16-bytes), 192-bits (24-bytes) or 256-bits (32-bytes) in length. If another key size is used an error will be thrown.
PKCS#7 padding is set by default.
This example requires Common Crypto
It is necessary to have a bridging header to the project:
#import <CommonCrypto/CommonCrypto.h>
Add the Security.framework to the project.
This is example, not production code.
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;
}
Example usage:
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)")
}
Example Output:
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>
Notes:
One typical problem with CBC mode example code is that it leaves the creation and sharing of the random IV to the user. This example includes generation of the IV, prefixed the encrypted data and uses the prefixed IV during decryption. This frees the casual user from the details that are necessary for CBC mode.
For security the encrypted data also should have authentication, this example code does not provide that in order to be small and allow better interoperability for other platforms.
Also missing is key derivation of the key from a password, it is suggested that PBKDF2 be used is text passwords are used as keying material.
For robust production ready multi-platform encryption code see RNCryptor.