Decrypt Ruby's ActiveSupport::MessageEncryptor on Python 3

decrypt_ruby_MessageEncryptor.py

import hashlib
import base64
from Crypto import Random
from Crypto.Cipher import AES
import rubymarshal.reader
from pbkdf2 import PBKDF2

SECRET = "asdasd"
ITERATIONS = 65536
KEYLENGTH = 32

saltdic = {} # dont generate key again if it exists
def decrypt_secret(encrypted):
	global saltdic
	salt = encrypted.split('.')[0]
	parts = encrypted.split('.')[1].split(b"--")

	if salt not in saltdic:
		key = PBKDF2(SECRET, salt, ITERATIONS).read(KEYLENGTH)
		saltdic[salt] = key

	key = saltdic[salt]

	ciphertext = base64.b64decode(parts[0])
	iv = base64.b64decode(parts[1])
	aes = AES.new(key, AES.MODE_GCM, iv)
	decrypted = aes.decrypt(ciphertext)
	data = rubymarshal.reader.loads(decrypted)
	return data


ruby_encrypted_message = "" # "salt.base64message--base64salt--base64signature"
                            # we dont check for signature

print(decrypt_secret(ruby_encrypted_message)) # plaintext