AES 256 in swift 4 with CommonCrypto

SHA256-Bridging-Header.h

#import <CommonCrypto/CommonCrypto.h>

SHA256.swift

import Foundation

struct AES256 {
    
    private var key: Data
    private var iv: Data
    
    public init(key: Data, iv: Data) throws {
        guard key.count == kCCKeySizeAES256 else {
            throw Error.badKeyLength
        }
        guard iv.count == kCCBlockSizeAES128 else {
            throw Error.badInputVectorLength
        }
        self.key = key
        self.iv = iv
    }
    
    enum Error: Swift.Error {
        case keyGeneration(status: Int)
        case cryptoFailed(status: CCCryptorStatus)
        case badKeyLength
        case badInputVectorLength
    }

    func encrypt(_ digest: Data) throws -> Data {
        return try crypt(input: digest, operation: CCOperation(kCCEncrypt))
    }
    
    func decrypt(_ encrypted: Data) throws -> Data {
        return try crypt(input: encrypted, operation: CCOperation(kCCDecrypt))
    }
    
    private func crypt(input: Data, operation: CCOperation) throws -> Data {
        var outLength = Int(0)
        var outBytes = [UInt8](repeating: 0, count: input.count + kCCBlockSizeAES128)
        var status: CCCryptorStatus = CCCryptorStatus(kCCSuccess)
        input.withUnsafeBytes { (encryptedBytes: UnsafePointer<UInt8>!) -> () in
            iv.withUnsafeBytes { (ivBytes: UnsafePointer<UInt8>!) in
                key.withUnsafeBytes { (keyBytes: UnsafePointer<UInt8>!) -> () in
                    status = CCCrypt(operation,                     
                                     CCAlgorithm(kCCAlgorithmAES128),            // algorithm
                                     CCOptions(kCCOptionPKCS7Padding),           // options
                                     keyBytes,                                   // key
                                     key.count,                                  // keylength
                                     ivBytes,                                    // iv
                                     encryptedBytes,                             // dataIn
                                     input.count,                                // dataInLength
                                     &outBytes,                                  // dataOut
                                     outBytes.count,                             // dataOutAvailable
                                     &outLength)                                 // dataOutMoved
                }
            }
        }
        guard status == kCCSuccess else {
            throw Error.cryptoFailed(status: status)
        }
        return Data(bytes: UnsafePointer<UInt8>(outBytes), count: outLength)
    }
    
    static func createKey(password: Data, salt: Data) throws -> Data {
        let length = kCCKeySizeAES256
        var status = Int32(0)
        var derivedBytes = [UInt8](repeating: 0, count: length)
        password.withUnsafeBytes { (passwordBytes: UnsafePointer<Int8>!) in
            salt.withUnsafeBytes { (saltBytes: UnsafePointer<UInt8>!) in
                status = CCKeyDerivationPBKDF(CCPBKDFAlgorithm(kCCPBKDF2),                  // algorithm
                                              passwordBytes,                                // password
                                              password.count,                               // passwordLen
                                              saltBytes,                                    // salt
                                              salt.count,                                   // saltLen
                                              CCPseudoRandomAlgorithm(kCCPRFHmacAlgSHA1),   // prf
                                              10000,                                        // rounds
                                              &derivedBytes,                                // derivedKey
                                              length)                                       // derivedKeyLen
            }
        }
        guard status == 0 else {
            throw Error.keyGeneration(status: Int(status))
        }
        return Data(bytes: UnsafePointer<UInt8>(derivedBytes), count: length)
    }
    
    static func randomIv() -> Data {
        return randomData(length: kCCBlockSizeAES128)
    }
    
    static func randomSalt() -> Data {
        return randomData(length: 8)
    }
    
    static func randomData(length: Int) -> Data {
        var data = Data(count: length)
        let status = data.withUnsafeMutableBytes { mutableBytes in
            SecRandomCopyBytes(kSecRandomDefault, length, mutableBytes)
        }
        assert(status == Int32(0))
        return data
    }
}

ViewController.swift

import UIKit

extension Data {
    var hexString: String {
        return map { String(format: "%02hhx", $0) }.joined()
    }
}

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        do {
            let digest = "hello world".data(using: .utf8)!
            let password = "foo"
            let salt = AES256.randomSalt()
            let iv = AES256.randomIv()
            let key = try AES256.createKey(password: password.data(using: .utf8)!, salt: salt)
            let aes = try AES256(key: key, iv: iv)
            let encrypted = try aes.encrypt(digest)
            let decrypted = try aes.decrypt(encrypted)
            
            print("Encrypted: \(encrypted.hexString)")
            print("Decrypted: \(decrypted.hexString)")
            print("Password: \(password)")
            print("Key: \(key.hexString)")
            print("IV: \(iv.hexString)")
            print("Salt: \(salt.hexString)")
            print(" ")
            
            print("#! /bin/sh")
            print("echo \(digest.hexString) | xxd -r -p > digest.txt")
            print("echo \(encrypted.hexString) | xxd -r -p > encrypted.txt")
            print("openssl aes-256-cbc -K \(key.hexString) -iv \(iv.hexString) -e -in digest.txt -out encrypted-openssl.txt")
            print("openssl aes-256-cbc -K \(key.hexString) -iv \(iv.hexString) -d -in encrypted.txt -out decrypted-openssl.txt")
        } catch {
            print("Failed")
            print(error)
        }
    }
}

ViewController.txt

Encrypted: 76be70e3e63890e12572bc55ed8f95b1
Decrypted: 68656c6c6f20776f726c64
Password: foo
Key: 848496354b13779568e1ee81f1f73428678f131c3d7501ef9ed99f7a7b4bf70c
IV: 4bb9f6f8bfb7adaad584e032a4cd412f
Salt: eedb0c8de0a9d09f
----
echo 68656c6c6f20776f726c64 | xxd -r -p > digest.txt
echo 76be70e3e63890e12572bc55ed8f95b1 | xxd -r -p > encrypted.txt
openssl aes-256-cbc -K 848496354b13779568e1ee81f1f73428678f131c3d7501ef9ed99f7a7b4bf70c -iv 4bb9f6f8bfb7adaad584e032a4cd412f -e -in digest.txt -out encrypted-openssl.txt
openssl aes-256-cbc -K 848496354b13779568e1ee81f1f73428678f131c3d7501ef9ed99f7a7b4bf70c -iv 4bb9f6f8bfb7adaad584e032a4cd412f -d -in encrypted.txt -out decrypted-openssl.txt

it appears that IV should be hardcoded or saved somewhere, because if I use it as random during the encryption and then try to decrypt the string with a new generated IV it does not work. IV bytes are not being cut.

If you need this for Swift 5

`
import Foundation
import CommonCrypto

struct AES256 {
private var key: Data
private var iv: Data

public init(key: Data, iv: Data) throws {
    guard key.count == kCCKeySizeAES256 else {
        throw Error.badKeyLength
    }
    guard iv.count == kCCBlockSizeAES128 else {
        throw Error.badInputVectorLength
    }
    self.key = key
    self.iv = iv
}

enum Error: Swift.Error {
    case keyGeneration(status: Int)
    case cryptoFailed(status: CCCryptorStatus)
    case badKeyLength
    case badInputVectorLength
}

func encrypt(_ digest: Data) throws -> Data {
    return try crypt(input: digest, operation: CCOperation(kCCEncrypt))
}

func decrypt(_ encrypted: Data) throws -> Data {
    return try crypt(input: encrypted, operation: CCOperation(kCCDecrypt))
}

private func crypt(input: Data, operation: CCOperation) throws -> Data {
    var outLength = Int(0)
    var outBytes = [UInt8](repeating: 0, count: input.count + kCCBlockSizeAES128)
    var status: CCCryptorStatus = CCCryptorStatus(kCCSuccess)
    
    input.withUnsafeBytes { rawBufferPointer in
        let encryptedBytes = rawBufferPointer.baseAddress!
        
        iv.withUnsafeBytes { rawBufferPointer in
            let ivBytes = rawBufferPointer.baseAddress!
            
            key.withUnsafeBytes { rawBufferPointer in
                let keyBytes = rawBufferPointer.baseAddress!
                
                status = CCCrypt(operation,
                                 CCAlgorithm(kCCAlgorithmAES128),            // algorithm
                                 CCOptions(kCCOptionPKCS7Padding),           // options
                                 keyBytes,                                   // key
                                 key.count,                                  // keylength
                                 ivBytes,                                    // iv
                                 encryptedBytes,                             // dataIn
                                 input.count,                                // dataInLength
                                 &outBytes,                                  // dataOut
                                 outBytes.count,                             // dataOutAvailable
                                 &outLength)                                 // dataOutMoved
            }
        }
    }
    
    guard status == kCCSuccess else {
        throw Error.cryptoFailed(status: status)
    }
            
    return Data(bytes: &outBytes, count: outLength)
}

static func createKey(password: Data, salt: Data) throws -> Data {
    let length = kCCKeySizeAES256
    var status = Int32(0)
    var derivedBytes = [UInt8](repeating: 0, count: length)
    
    
    password.withUnsafeBytes { rawBufferPointer in
        let passwordRawBytes = rawBufferPointer.baseAddress!
        let passwordBytes = passwordRawBytes.assumingMemoryBound(to: Int8.self)
        
        salt.withUnsafeBytes { rawBufferPointer in
            let saltRawBytes = rawBufferPointer.baseAddress!
            let saltBytes = saltRawBytes.assumingMemoryBound(to: UInt8.self)
            
            status = CCKeyDerivationPBKDF(CCPBKDFAlgorithm(kCCPBKDF2),                  // algorithm
                                          passwordBytes,                                // password
                                          password.count,                               // passwordLen
                                          saltBytes,                                    // salt
                                          salt.count,                                   // saltLen
                                          CCPseudoRandomAlgorithm(kCCPRFHmacAlgSHA1),   // prf
                                          10000,                                        // rounds
                                          &derivedBytes,                                // derivedKey
                                          length)                                       // derivedKeyLen
        }
    }
    

    guard status == 0 else {
        throw Error.keyGeneration(status: Int(status))
    }
    return Data(bytes: &derivedBytes, count: length)
}

static func randomIv() -> Data {
    return randomData(length: kCCBlockSizeAES128)
}

static func iV() -> Data {
    let arr: [UInt8] = [0,0,1,1,0,0,1,1,0,0,1,1,0,0,1,1]
    return Data(arr)
}

static func randomSalt() -> Data {
    return randomData(length: 8)
}

static func randomData(length: Int) -> Data {
    var data = Data(count: length)
    
    var mutableBytes: UnsafeMutableRawPointer!
    
    data.withUnsafeMutableBytes { rawBufferPointer in
        mutableBytes = rawBufferPointer.baseAddress!
    }
    
    let status = SecRandomCopyBytes(kSecRandomDefault, length, mutableBytes)
    
    assert(status == Int32(0))
    return data
}

}`

very interesting implementation,
could you please publish also the data extension hexString?

How to encrypt image ??

Big question. Lots of good articles on the subject

I used crypto swift but it is slow. any suggestions?