So, I’m helping vishalfromnashik in another context but, as part of that, I created a Swift wrapper around CommonCrypto’s AES CBC support. I’ve pasted it in below for the benefit of all.
This includes a simple test suite, derived from the one in the CryptoCompatibility sample code (which is my go-to reference for this sort of thing).
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
import Foundation
import CommonCrypto
/// Encrypts data using AES with PKCS#7 padding in CBC mode.
///
/// - note: PKCS#7 padding is also known as PKCS#5 padding.
///
/// - Parameters:
/// - key: The key to encrypt with; must be a supported size (128, 192, 256).
/// - iv: The initialisation vector; must be of size 16.
/// - plaintext: The data to encrypt; the PKCS#7 padding means there are no
/// constraints on its length.
/// - Returns: The encrypted data; it’s length with always be an even multiple of 16.
func QCCAESPadCBCEncrypt(key: [UInt8], iv: [UInt8], plaintext: [UInt8]) throws -> [UInt8] {
// The key size must be 128, 192, or 256.
//
// The IV size must match the block size.
guard
[kCCKeySizeAES128, kCCKeySizeAES192, kCCKeySizeAES256].contains(key.count),
iv.count == kCCBlockSizeAES128
else {
throw QCCError(code: kCCParamError)
}
// Padding can expand the data, so we have to allocate space for that. The
// rule for block cyphers, like AES, is that the padding only adds space on
// encryption (on decryption it can reduce space, obviously, but we don't
// need to account for that) and it will only add at most one block size
// worth of space.
var cyphertext = [UInt8](repeating: 0, count: plaintext.count + kCCBlockSizeAES128)
var cyphertextCount = 0
let err = CCCrypt(
CCOperation(kCCEncrypt),
CCAlgorithm(kCCAlgorithmAES),
CCOptions(kCCOptionPKCS7Padding),
key, key.count,
iv,
plaintext, plaintext.count,
&cyphertext, cyphertext.count,
&cyphertextCount
)
guard err == kCCSuccess else {
throw QCCError(code: err)
}
// The cyphertext can expand by up to one block but it doesn’t always use the full block,
// so trim off any unused bytes.
assert(cyphertextCount <= cyphertext.count)
cyphertext.removeLast(cyphertext.count - cyphertextCount)
assert(cyphertext.count.isMultiple(of: kCCBlockSizeAES128))
return cyphertext
}
/// Decrypts data that was encrypted using AES with PKCS#7 padding in CBC mode.
///
/// - note: PKCS#7 padding is also known as PKCS#5 padding.
///
/// - Parameters:
/// - key: The key to encrypt with; must be a supported size (128, 192, 256).
/// - iv: The initialisation vector; must be of size 16.
/// - cyphertext: The encrypted data; it’s length must be an even multiple of
/// 16.
/// - Returns: The decrypted data.
func QCCAESPadCBCDecrypt(key: [UInt8], iv: [UInt8], cyphertext: [UInt8]) throws -> [UInt8] {
// The key size must be 128, 192, or 256.
//
// The IV size must match the block size.
//
// The ciphertext must be a multiple of the block size.
guard
[kCCKeySizeAES128, kCCKeySizeAES192, kCCKeySizeAES256].contains(key.count),
iv.count == kCCBlockSizeAES128,
cyphertext.count.isMultiple(of: kCCBlockSizeAES128)
else {
throw QCCError(code: kCCParamError)
}
// Padding can expand the data on encryption, but on decryption the data can
// only shrink so we use the cyphertext size as our plaintext size.
var plaintext = [UInt8](repeating: 0, count: cyphertext.count)
var plaintextCount = 0
let err = CCCrypt(
CCOperation(kCCDecrypt),
CCAlgorithm(kCCAlgorithmAES),
CCOptions(kCCOptionPKCS7Padding),
key, key.count,
iv,
cyphertext, cyphertext.count,
&plaintext, plaintext.count,
&plaintextCount
)
guard err == kCCSuccess else {
throw QCCError(code: err)
}
// Trim any unused bytes off the plaintext.
assert(plaintextCount <= plaintext.count)
plaintext.removeLast(plaintext.count - plaintextCount)
return plaintext
}
/// Wraps `CCCryptorStatus` for use in Swift.
struct QCCError: Error {
var code: CCCryptorStatus
}
extension QCCError {
init(code: Int) {
self.init(code: CCCryptorStatus(code))
}
}
func main() {
// This test case was taken from the CryptoCompatibility sample code, and
// specifically the `-testAES256PadCBCEncryption` methods and
// `-testAES256PadCBCDecryption` methods.
//
// <https://developer.apple.com/library/mac/#samplecode/CryptoCompatibility/>
let key: [UInt8] = [
0x0C, 0x10, 0x32, 0x52, 0x03, 0x02, 0xEC, 0x85,
0x37, 0xA4, 0xA8, 0x2C, 0x4E, 0xF7, 0x57, 0x9D,
0x2b, 0x88, 0xe4, 0x30, 0x96, 0x55, 0xeb, 0x40,
0x70, 0x7d, 0xec, 0xdb, 0x14, 0x3e, 0x32, 0x8a,
]
let iv: [UInt8] = [
0xAB, 0x5B, 0xBE, 0xB4, 0x26, 0x01, 0x5D, 0xA7,
0xEE, 0xDC, 0xEE, 0x8B, 0xEE, 0x3D, 0xFF, 0xB7,
]
let plaintext332: [UInt8] = [
0x54, 0x68, 0x65, 0x20, 0x41, 0x70, 0x70, 0x6C,
0x65, 0x20, 0x53, 0x6F, 0x66, 0x74, 0x77, 0x61,
0x72, 0x65, 0x20, 0x69, 0x73, 0x20, 0x70, 0x72,
0x6F, 0x76, 0x69, 0x64, 0x65, 0x64, 0x20, 0x62,
0x79, 0x20, 0x41, 0x70, 0x70, 0x6C, 0x65, 0x20,
0x6F, 0x6E, 0x20, 0x61, 0x6E, 0x20, 0x22, 0x41,
0x53, 0x20, 0x49, 0x53, 0x22, 0x20, 0x62, 0x61,
0x73, 0x69, 0x73, 0x2E, 0x20, 0x41, 0x50, 0x50,
0x4C, 0x45, 0x20, 0x4D, 0x41, 0x4B, 0x45, 0x53,
0x20, 0x4E, 0x4F, 0x20, 0x57, 0x41, 0x52, 0x52,
0x41, 0x4E, 0x54, 0x49, 0x45, 0x53, 0x2C, 0x20,
0x45, 0x58, 0x50, 0x52, 0x45, 0x53, 0x53, 0x20,
0x4F, 0x52, 0x20, 0x49, 0x4D, 0x50, 0x4C, 0x49,
0x45, 0x44, 0x2C, 0x20, 0x49, 0x4E, 0x43, 0x4C,
0x55, 0x44, 0x49, 0x4E, 0x47, 0x20, 0x57, 0x49,
0x54, 0x48, 0x4F, 0x55, 0x54, 0x20, 0x4C, 0x49,
0x4D, 0x49, 0x54, 0x41, 0x54, 0x49, 0x4F, 0x4E,
0x20, 0x54, 0x48, 0x45, 0x20, 0x49, 0x4D, 0x50,
0x4C, 0x49, 0x45, 0x44, 0x20, 0x57, 0x41, 0x52,
0x52, 0x41, 0x4E, 0x54, 0x49, 0x45, 0x53, 0x20,
0x4F, 0x46, 0x20, 0x4E, 0x4F, 0x4E, 0x2D, 0x49,
0x4E, 0x46, 0x52, 0x49, 0x4E, 0x47, 0x45, 0x4D,
0x45, 0x4E, 0x54, 0x2C, 0x20, 0x4D, 0x45, 0x52,
0x43, 0x48, 0x41, 0x4E, 0x54, 0x41, 0x42, 0x49,
0x4C, 0x49, 0x54, 0x59, 0x20, 0x41, 0x4E, 0x44,
0x20, 0x46, 0x49, 0x54, 0x4E, 0x45, 0x53, 0x53,
0x20, 0x46, 0x4F, 0x52, 0x20, 0x41, 0x20, 0x50,
0x41, 0x52, 0x54, 0x49, 0x43, 0x55, 0x4C, 0x41,
0x52, 0x20, 0x50, 0x55, 0x52, 0x50, 0x4F, 0x53,
0x45, 0x2C, 0x20, 0x52, 0x45, 0x47, 0x41, 0x52,
0x44, 0x49, 0x4E, 0x47, 0x20, 0x54, 0x48, 0x45,
0x20, 0x41, 0x50, 0x50, 0x4C, 0x45, 0x20, 0x53,
0x4F, 0x46, 0x54, 0x57, 0x41, 0x52, 0x45, 0x20,
0x4F, 0x52, 0x20, 0x49, 0x54, 0x53, 0x20, 0x55,
0x53, 0x45, 0x20, 0x41, 0x4E, 0x44, 0x20, 0x4F,
0x50, 0x45, 0x52, 0x41, 0x54, 0x49, 0x4F, 0x4E,
0x20, 0x41, 0x4C, 0x4F, 0x4E, 0x45, 0x20, 0x4F,
0x52, 0x20, 0x49, 0x4E, 0x20, 0x43, 0x4F, 0x4D,
0x42, 0x49, 0x4E, 0x41, 0x54, 0x49, 0x4F, 0x4E,
0x20, 0x57, 0x49, 0x54, 0x48, 0x20, 0x59, 0x4F,
0x55, 0x52, 0x20, 0x50, 0x52, 0x4F, 0x44, 0x55,
0x43, 0x54, 0x53, 0x2E
]
let cyphertextAES256CBC332: [UInt8] = [
0xDD, 0x7B, 0x23, 0x4D, 0x67, 0x05, 0xFE, 0xBF,
0x28, 0x8D, 0x45, 0xFD, 0x93, 0x78, 0x6C, 0xEB,
0x20, 0x22, 0xD8, 0x24, 0x89, 0x88, 0xAD, 0x1F,
0x1C, 0x9E, 0x7E, 0x61, 0x6A, 0xE6, 0x4E, 0x79,
0xA2, 0x47, 0x1B, 0xA3, 0x7C, 0xFE, 0x51, 0xED,
0xF1, 0xEB, 0x9F, 0x5E, 0x01, 0x9B, 0x47, 0x30,
0xD7, 0x2F, 0x87, 0x22, 0xDF, 0xA9, 0xEB, 0x1F,
0x5C, 0xA3, 0x5F, 0xEA, 0x18, 0xDE, 0x2D, 0x18,
0x08, 0x48, 0x8C, 0x84, 0xBC, 0xE9, 0x83, 0xA7,
0x4E, 0x48, 0x92, 0xBB, 0x76, 0xA7, 0x9C, 0x71,
0x27, 0x8B, 0x40, 0x82, 0x2E, 0xC3, 0xC5, 0x92,
0xA5, 0x9F, 0x87, 0xC3, 0x90, 0xF2, 0x8E, 0x75,
0xCB, 0xDB, 0x94, 0xC1, 0xBF, 0xC6, 0x60, 0xC7,
0x6A, 0xBA, 0xAA, 0x35, 0x26, 0xB0, 0xE3, 0x49,
0xCA, 0x26, 0x39, 0x72, 0xEB, 0x89, 0x01, 0x9F,
0xC9, 0x44, 0x67, 0x74, 0x1F, 0xCD, 0xBA, 0x2C,
0xB1, 0x95, 0x99, 0xFE, 0x1C, 0xDA, 0x4D, 0xE7,
0x32, 0x6B, 0xE8, 0xCE, 0x66, 0x0F, 0xD3, 0x8E,
0x25, 0x17, 0x82, 0x5A, 0x9C, 0x21, 0xA2, 0x28,
0xF0, 0x71, 0x99, 0xD8, 0x4A, 0x5A, 0x58, 0x80,
0x94, 0x36, 0x9A, 0x7F, 0xA5, 0xFA, 0xC1, 0x6E,
0xA7, 0x04, 0x68, 0xF5, 0x2E, 0x38, 0x73, 0x01,
0xF4, 0x99, 0xF8, 0x48, 0x12, 0x53, 0xCF, 0x06,
0x67, 0x0B, 0x07, 0xF2, 0x45, 0x3A, 0xEE, 0xD7,
0x2B, 0x45, 0x03, 0xE7, 0x50, 0x1D, 0x52, 0xD8,
0xFA, 0x73, 0xC6, 0xBE, 0x79, 0x65, 0x01, 0x11,
0x81, 0x0B, 0x94, 0x0E, 0xA4, 0x96, 0x20, 0xC9,
0x60, 0xBE, 0xB4, 0xEA, 0x1F, 0xCC, 0xC4, 0x22,
0x6A, 0xE6, 0x52, 0xDE, 0x62, 0x25, 0x61, 0xCF,
0xE1, 0x2D, 0x1C, 0x0B, 0x65, 0xD3, 0xC3, 0x08,
0xEE, 0x00, 0x5B, 0x61, 0x06, 0x72, 0xAA, 0xB6,
0x2F, 0x3D, 0xC7, 0x23, 0xAE, 0xF7, 0xA7, 0xC3,
0xA9, 0x7E, 0xBF, 0xC7, 0xF0, 0x3B, 0x68, 0xB6,
0xEB, 0x22, 0xA2, 0x8E, 0x70, 0xE3, 0xD3, 0x27,
0x83, 0xDB, 0x1C, 0xD2, 0x48, 0x3C, 0xEE, 0x63,
0x36, 0xAA, 0x9D, 0xD7, 0x2D, 0x24, 0x7C, 0xD2,
0x22, 0x1E, 0xFB, 0x42, 0xE4, 0x4F, 0xA7, 0x48,
0xB2, 0x3F, 0xB6, 0xD3, 0x25, 0xAD, 0x93, 0x72,
0x02, 0x8F, 0x0E, 0x70, 0x57, 0xF4, 0x74, 0xC9,
0x2D, 0x1E, 0xEB, 0xC6, 0x4A, 0x78, 0x21, 0x33,
0x4F, 0x2A, 0x41, 0x44, 0xD1, 0xC9, 0x45, 0x13,
0x5A, 0x0D, 0x64, 0x4E, 0xD6, 0xF5, 0x54, 0x9E,
]
let cyphertext = try! QCCAESPadCBCEncrypt(key: key, iv: iv, plaintext: plaintext332)
assert(cyphertext == cyphertextAES256CBC332)
let plaintext = try! QCCAESPadCBCDecrypt(key: key, iv: iv, cyphertext: cyphertext)
assert(plaintext == plaintext332)
print("Success!")
}
main()
