(Chilkat2-Python) 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

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS, Solaris

import chilkat2

# 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 = chilkat2.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)

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.
bdKey = chilkat2.BinData()
bdKey.AppendString(passphrase,"utf-8")

sz = bdKey.NumBytes
if (sz > 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 = chilkat2.BinData()
bd.AppendEncoded(ivBase64,"base64")
bd.AppendEncoded(cipherText64,"base64")
result = 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"),"base64")

bdResult = chilkat2.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")

print("original text = " + originalText)