Support for Ruby 2.4.x - key must be 32 bytes

[scottwater]

Trying to generate a scoped key on Ruby 2.4.1 both with gem versions 0.9.3 and 0.9.7:

keen (0.9.7) lib/keen/aes_helper_old.rb:27:in key=' keen (0.9.7) lib/keen/aes_helper_old.rb:27:in aes256_encrypt'
keen (0.9.7) lib/keen/scoped_key.rb:33:in `encrypt!'

Here is code you can use to generate the exception:

master_key = ENV['KEEN_MASTER_KEY']
filters = {user_id: 1}
keen_filters = filters.map {|k,v| {property_name: k, operator: 'eq', property_value: v}}
Keen::ScopedKey.new(master_key, { filters: keen_filters, allowed_operations: [ "read" ]}).encrypt!

Also, my master key is exactly 32 characters long. If I were to use it to something like 'x' it no longer throws the exception.

[scottwater]

Digging through the code, it looks like if the key is 32 characters long, it shouldn't be padded.

This works for me: https://gist.github.com/scottwater/ebe6fd1df2955cae336cc957ff28ca20

It sounds like previous versions of Ruby's SSL support truncated keys greater than 32 characters. So the extra padding applied in AESHelperOld was simply stripped out. (see: attr-encrypted/encryptor#26)

The monkey patch above works locally for me in both Ruby 2.3.3 and Ruby 2.4.2