Pure Python implementation of SecureStringToBSTR

secure.py

#!/usr/bin/env python3
#
# Pure Python code for PowerShell's SecureStringToBSTR API
#
# @jaydinbas
#

import base64
import binascii
import hashlib

# or Crypto.xxx depending on your system
from Cryptodome.Cipher import AES
from Cryptodome.Util.Padding import unpad

def secure_string_decrypt(key,data):
    _ = data[:32] # not sure, some MD5 probably
    data = data[32:]

    data = base64.b64decode(data).decode("utf16")
    (_,iv,ct) = data.split("|")

    ct = binascii.unhexlify(ct)

    iv = base64.b64decode(iv)
    cipher = AES.new(key=key,iv=iv,mode=AES.MODE_CBC)
    plain = unpad(cipher.decrypt(ct),16)

    return plain.decode("utf16")

# test vectors from
# https://eddiejackson.net/wp/?p=28189

key = bytes([2,3,1,4,54,32,144,23,5,3,1,41,36,31,18,175,6,17,1,9,5,1,76,23])

data = "76492d1116743f0423413b16050a5345MgB8AFoAQgByAHQAWABEAEQAZQBpAFgATgBiAGIAbwBzAEIAZQBKAEIARgBNAHcAPQA9AHwAOABjADMANABmADUAYgA3ADQAZAA1ADMANQA1AGEAMAA3ADgAMwA5AGEAOQBiAGUANwAzADAAYQBmADkAOQA1ADYANAA5ADcAYQA2ADUANwA4AGEANwAwADQANgA4ADEAYgAzADQAMQAyADYAZgA0ADkAMgAyADEAYwAwADAANAA="

print(secure_string_decrypt(key,data))