PWM encrypt/decrypt in Ruby

gistfile1.rb

# This ruby script lets you encrypt and decrypt secrets stored in PwmConfiguration.xml files.
# The secret key consists of the 'createTime' attribute of the root element of the file, concatenated
# with the string StoredConfiguration. You can use this to auto generate compliant PwmConfiguration.xml
# files if you control the createTime.

require 'base64'
require 'openssl'
require 'digest/sha1'

def pwm_cipher
  OpenSSL::Cipher::Cipher.new('AES-128-ECB')
end

def pwm_make_key(key)
  # pwm keeps only the first 16 bytes
  Digest::SHA1.digest(key).byteslice(0..-5)
end

def pwm_encrypt(key, plain)
  aes = pwm_cipher
  aes.encrypt
  aes.key = pwm_make_key(key)
  hex = aes.update(plain) + aes.final
  Base64.urlsafe_encode64(hex)
end

def pwm_decrypt(key, crypt)
  hex = Base64.urlsafe_decode64(crypt)
  aes = pwm_cipher
  aes.decrypt
  aes.key = pwm_make_key(key)
  aes.update(hex) + aes.final
end

# try it: puts pwm_decrypt(somekey, pwm_encrypt(somekey, someplaintext))