decode session

decode_session.rb

key_generator = ActiveSupport::KeyGenerator.new(
  Rails.application.config.secret_key_base, 
  iterations: 1000)

secret = key_generator.generate_key(
  Rails.application.config
  .action_dispatch
  .encrypted_cookie_salt)

salt = key_generator.generate_key(
  Rails.application.config
  .action_dispatch
  .encrypted_signed_cookie_salt)

encryptor = ActiveSupport::MessageEncryptor.new(
  secret[
    0, 
    ActiveSupport::MessageEncryptor.key_len
    ], 
  salt, serializer: JSON)

session_data 
  = encryptor.decrypt_and_verify(COOKIE_VALUE)