DaffyLib

This gem is a caching encryptor which improves performance when encrypting/decrypting large amounts of data. It will keep a plaintext key cached for a given amount of time, as well as provide partitioning to allow entire rows to be encrypted with the same key. Keys are uniquely identified by a pair of a partition guid and an encryption epoch.

Add this line to your application's Gemfile:

gem 'daffy_lib'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install daffy_lib

We illustrate usage of this library with an example. Suppose we have classes User and User::Attribute where attributes belong to users and have values that need to be encrypted. We wish for User to be the partition provider for User::Attribute.

The User class will need to include DaffyLib::PartitionProvider and implement the method provider_partition_guid which returns an identifier, for instance a user's guid.

The User::Attribute class will need to include DaffyLib::PartitionProvider as well as include DaffyLib::HasEncryptedAttributes. It will need to declare partition_provider :user.

There are default implementations of generate_partition_guid which returns the linked User's guid, as well as a generate_encryption_epoch method which defines the encryption epoch, which are the following.

def generate_partition_guid
  return partition_guid if partition_guid.present?

  self.partition_guid = provider_partition_guid
end

def generate_encryption_epoch
  return encryption_epoch if encryption_epoch.present?

  self.encryption_epoch = DaffyLib::KeyManagementService.encryption_key_epoch(Time.now)
end

These work for the general case of a model with encrypted attributes that has a partition provider other than itself, and for an encryption epoch period of 1 year. They can be overriden if necessary.

Now suppose the User::Attributes has a values field to be encrypted. One declares

attr_encrypted :values, encryptor: ZtCachingEncryptor, encrypt_method: :zt_encrypt, decrypt_method: :zt_decrypt,
                        encode: true, partition_guid: proc { |object| object.generate_partition_guid },
                        encryption_epoch: proc { |object| object.generate_encryption_epoch }, expires_in: 5.minutes

where the expires_in field denotes how long a plaintext key should be kept in cache.

Note further that a class can be its own partition provider; i.e. if User itself had encrypted attributes, all the steps above for User::Attributes apply, except there is no need to declare partition_provider, and the recommended implementation for generate_partition_guid is to return (or create) the guid of the User.

There are partial rake tasks to assist with the necessary database migrations included.

Run rake db:migrate:add_encryption_keys_table to generate the migration file to add the encryption keys table. Add the following lines for indexing to the generated file.

t.index [:guid], name: :index_encryption_keys_on_guid, unique: true
t.index [:partition_guid, :key_epoch], name: :index_encryption_keys, unique: true

Next, run rake db:migrate:add_encryption_fields['modelname'] to add the partition_guid and encryption_epoch columns to each model.

Run rake generate_encryption_attributes['modelname','limit'] to populate existing records of each model with the encryption attributes. The limit specifies the maximum number of records updated per execution; a limit of 0 means no limit.

Finally, once existing records have been populated, it is advisable to perform a final migration to set partition_guid and encryption_epoch columns to mandatory.

Development on this project should occur on separate feature branches and pull requests should be submitted. When submitting a pull request, the pull request comment template should be filled out as much as possible to ensure a quick review and increase the likelihood of the pull request being accepted.

This application requires:

• Ruby version: 2.7.1

Ruby 2.7.1 and greater requires OpenSSL 1.1+. To link to Homebrew's upgraded version of OpenSSL, add the following to your bash profile

export RUBY_CONFIGURE_OPTS="--with-openssl-dir=$(brew --prefix openssl@1.1)"

If you do not have Ruby installed, it is recommended you use ruby-install and chruby to manage Ruby versions.

brew install ruby-install chruby
ruby-install ruby 2.7.1

Add the following lines to ~/.bash_profile:

source /usr/local/opt/chruby/share/chruby/chruby.sh
source /usr/local/opt/chruby/share/chruby/auto.sh

Set Ruby version to 2.7.1:

source ~/.bash_profile
chruby 2.7.1

Bug reports and pull requests are welcome on GitHub at https://github.com/Zetatango/daffy_lib.