(Swift 2) Duplicate PHP's openssl_encrypt and openssl_random_pseudo_bytes

Demonstrates how to duplicate PHP's openssl_encrypt function. (https://www.php.net/manual/en/function.openssl-encrypt.php)

For more information, see https://www.php.net/manual/en/function.openssl-encrypt.php

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // Duplicates thw following PHP script:

    // $text = "This is a test";
    // $passphrase = "my password";
    // $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length("AES-256-CBC"));
    // $crypted = base64_encode($iv.openssl_encrypt($text, "AES-256-CBC", $passphrase, OPENSSL_RAW_DATA, $iv));
    // echo $crypted;

    var success: Bool
    let crypt = CkoCrypt2()

    var text: String? = "This is a test"
    var passphrase: String? = "my password"

    // AES is a block cipher.  The IV size for any block cipher is the size of the block, which is defined by the encryption algorithm. 
    // For AES, the block size is always 16 bytes, regardless of key size (i.e. 128-bits, 192-bits, or 256-bits).
    // Therefore, generate 16 random bytes for the IV.
    crypt.EncodingMode = "base64"
    var ivBase64: String? = crypt.GenRandomBytesENC(16)

    print("Generated IV = \(ivBase64!)")

    // Because we're doing AES-256-CBC, the key length must be 256-bits (i.e. 32 bytes).
    // Given that our passphrase is a us-ascii string that can be shorter or longer than 32-bytes, we need to 
    // somehow transform the passphrase to a 32-byte secret key.  We need to know what openssl_encrypt does.
    // Here's the answer from the openssl_encrypt documentation:
    // 
    // "If the passphrase is shorter than expected, it is silently padded with NUL characters; 
    // if the passphrase is longer than expected, it is silently truncated."

    // OK.... so let's pad or shorten to get a 32-byte key.
    let bdKey = CkoBinData()
    bdKey.AppendString(passphrase, charset: "utf-8")

    var sz: Int = bdKey.NumBytes.intValue
    if sz > 32 {
        bdKey.RemoveChunk(32, numBytes: sz - 32)
    }
    else {
        bdKey.Clear()
        bdKey.AppendPadded(passphrase, charset: "utf-8", padWithSpace: false, fieldLen: 32)
    }

    // Setup for encryption.
    crypt.CryptAlgorithm = "aes"
    crypt.KeyLength = 256
    crypt.SetEncodedIV(ivBase64, encoding: "base64")
    crypt.SetEncodedKey(bdKey.GetEncoded("base64"), encoding: "base64")

    // Encrypt and base64 encode.
    var cipherText64: String? = crypt.EncryptStringENC(text)

    // The PHP code fragment above returns the base64 encoded bytes of the IV and the encrypted text.
    // So let's do that..
    let bd = CkoBinData()
    bd.AppendEncoded(ivBase64, encoding: "base64")
    bd.AppendEncoded(cipherText64, encoding: "base64")
    var result: String? = bd.GetEncoded("base64")

    print("result = \(result!)")

    // Sample output:
    // dN0vS1O0cWi5BbLAAY+NTf7bs3S27xzPf11RkG47sjs=

    // Now let's decrypt from the output...

    // Setup for decryption.
    crypt.CryptAlgorithm = "aes"
    crypt.KeyLength = 256
    crypt.SetEncodedKey(bdKey.GetEncoded("base64"), encoding: "base64")

    let bdResult = CkoBinData()
    bdResult.AppendEncoded(result, encoding: "base64")
    crypt.SetEncodedIV(bdResult.GetEncodedChunk(0, numBytes: 16, encoding: "base64"), encoding: "base64")

    // Remove the IV (first 16 bytes) from the result.
    bdResult.RemoveChunk(0, numBytes: 16)
    success = crypt.DecryptBd(bdResult)
    var originalText: String? = bdResult.GetString("utf-8")

    print("original text = \(originalText!)")

}