(Visual FoxPro) 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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loCrypt
LOCAL lcText
LOCAL lcPassphrase
LOCAL lcIvBase64
LOCAL loBdKey
LOCAL lnSz
LOCAL lcCipherText64
LOCAL loBd
LOCAL lcResult
LOCAL loBdResult
LOCAL lcOriginalText

* 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;

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Crypt2')
loCrypt = CreateObject('Chilkat.Crypt2')

lcText = "This is a test"
lcPassphrase = "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.
loCrypt.EncodingMode = "base64"
lcIvBase64 = loCrypt.GenRandomBytesENC(16)

? "Generated IV = " + lcIvBase64

* 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.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdKey = CreateObject('Chilkat.BinData')
loBdKey.AppendString(lcPassphrase,"utf-8")

lnSz = loBdKey.NumBytes
IF (lnSz > 32) THEN
    loBdKey.RemoveChunk(32,lnSz - 32)
ELSE
    loBdKey.Clear()
    loBdKey.AppendPadded(lcPassphrase,"utf-8",0,32)
ENDIF

* Setup for encryption.
loCrypt.CryptAlgorithm = "aes"
loCrypt.KeyLength = 256
loCrypt.SetEncodedIV(lcIvBase64,"base64")
loCrypt.SetEncodedKey(loBdKey.GetEncoded("base64"),"base64")

* Encrypt and base64 encode.
lcCipherText64 = loCrypt.EncryptStringENC(lcText)

* The PHP code fragment above returns the base64 encoded bytes of the IV and the encrypted text.
* So let's do that..
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBd = CreateObject('Chilkat.BinData')
loBd.AppendEncoded(lcIvBase64,"base64")
loBd.AppendEncoded(lcCipherText64,"base64")
lcResult = loBd.GetEncoded("base64")

? "result = " + lcResult

* Sample output:
* dN0vS1O0cWi5BbLAAY+NTf7bs3S27xzPf11RkG47sjs=

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

* Setup for decryption.
loCrypt.CryptAlgorithm = "aes"
loCrypt.KeyLength = 256
loCrypt.SetEncodedKey(loBdKey.GetEncoded("base64"),"base64")

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdResult = CreateObject('Chilkat.BinData')
loBdResult.AppendEncoded(lcResult,"base64")
loCrypt.SetEncodedIV(loBdResult.GetEncodedChunk(0,16,"base64"),"base64")

* Remove the IV (first 16 bytes) from the result.
loBdResult.RemoveChunk(0,16)
lnSuccess = loCrypt.DecryptBd(loBdResult)
lcOriginalText = loBdResult.GetString("utf-8")

? "original text = " + lcOriginalText

RELEASE loCrypt
RELEASE loBdKey
RELEASE loBd
RELEASE loBdResult