(PowerShell) 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 .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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;

$crypt = New-Object Chilkat.Crypt2

$text = "This is a test"
$passphrase = "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"
$ivBase64 = $crypt.GenRandomBytesENC(16)

$("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.
$bdKey = New-Object Chilkat.BinData
$bdKey.AppendString($passphrase,"utf-8")

$sz = $bdKey.NumBytes
if ($sz -gt 32) {
    $bdKey.RemoveChunk(32,$sz - 32)
}
else {
    $bdKey.Clear()
    $bdKey.AppendPadded($passphrase,"utf-8",$false,32)
}

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

# Encrypt and base64 encode.
$cipherText64 = $crypt.EncryptStringENC($text)

# The PHP code fragment above returns the base64 encoded bytes of the IV and the encrypted text.
# So let's do that..
$bd = New-Object Chilkat.BinData
$bd.AppendEncoded($ivBase64,"base64")
$bd.AppendEncoded($cipherText64,"base64")
$result = $bd.GetEncoded("base64")

$("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"),"base64")

$bdResult = New-Object Chilkat.BinData
$bdResult.AppendEncoded($result,"base64")
$crypt.SetEncodedIV($bdResult.GetEncodedChunk(0,16,"base64"),"base64")

# Remove the IV (first 16 bytes) from the result.
$bdResult.RemoveChunk(0,16)
$success = $crypt.DecryptBd($bdResult)
$originalText = $bdResult.GetString("utf-8")

$("original text = " + $originalText)