Class: Lockbox

Inherits:
Object
  • Object
show all
Defined in:
lib/lockbox/active_storage_extensions.rb,
lib/lockbox.rb,
lib/lockbox/box.rb,
lib/lockbox/model.rb,
lib/lockbox/utils.rb,
lib/lockbox/aes_gcm.rb,
lib/lockbox/railtie.rb,
lib/lockbox/version.rb,
lib/lockbox/encryptor.rb,
lib/lockbox/key_generator.rb,
lib/lockbox/carrier_wave_extensions.rb

Overview

ideally encrypt and decrypt would happen at the blob/service level however, there isn’t really a great place to define encryption settings there instead, we encrypt and decrypt at the attachment level, and we define encryption settings at the model level

Defined Under Namespace

Modules: ActiveStorageExtensions, CarrierWaveExtensions, Model Classes: AES_GCM, Box, DecryptionError, Encryptor, Error, KeyGenerator, PaddingError, Railtie, Utils

Constant Summary collapse

PAD_FIRST_BYTE = 
"\x80".b
PAD_ZERO_BYTE = 
"\x00".b
VERSION = 
"0.2.1"

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(**options) ⇒ Lockbox

Returns a new instance of Lockbox.



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# File 'lib/lockbox.rb', line 73

def initialize(**options)
  options = self.class.default_options.merge(options)
  previous_versions = options.delete(:previous_versions)

  @boxes =
    [Box.new(options)] +
    Array(previous_versions).map { |v| Box.new(v) }
end

Class Attribute Details

.default_options ⇒ Object

Returns the value of attribute default_options.



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# File 'lib/lockbox.rb', line 28

def default_options
  @default_options
end

.master_key ⇒ Object 



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# File 'lib/lockbox.rb', line 33

def self.master_key
  @master_key ||= ENV["LOCKBOX_MASTER_KEY"]
end

Class Method Details

.attribute_key(table:, attribute:, master_key: nil, encode: true) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/lockbox.rb', line 130

def self.attribute_key(table:, attribute:, master_key: nil, encode: true)
  master_key ||= Lockbox.master_key
  raise ArgumentError, "Missing master key" unless master_key

  key = Lockbox::KeyGenerator.new(master_key).attribute_key(table: table, attribute: attribute)
  key = to_hex(key) if encode
  key
end

.generate_key ⇒ Object 



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# File 'lib/lockbox.rb', line 112

def self.generate_key
  SecureRandom.hex(32)
end

.generate_key_pair ⇒ Object 



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# File 'lib/lockbox.rb', line 116

def self.generate_key_pair
  require "rbnacl"
  # encryption and decryption servers exchange public keys
  # this produces smaller ciphertext than sealed box
  alice = RbNaCl::PrivateKey.generate
  bob = RbNaCl::PrivateKey.generate
  # alice is sending message to bob
  # use bob first in both cases to prevent keys being swappable
  {
    encryption_key: to_hex(bob.public_key.to_bytes + alice.to_bytes),
    decryption_key: to_hex(bob.to_bytes + alice.public_key.to_bytes)
  }
end

.migrate(model, restart: false) ⇒ Object 



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# File 'lib/lockbox.rb', line 37

def self.migrate(model, restart: false)
  # get fields
  fields = model.lockbox_attributes.select { |k, v| v[:migrating] }

  # get blind indexes
  blind_indexes = model.respond_to?(:blind_indexes) ? model.blind_indexes.select { |k, v| v[:migrating] } : {}

  # build relation
  relation = model.unscoped

  unless restart
    attributes = fields.map { |_, v| v[:encrypted_attribute] }
    attributes += blind_indexes.map { |_, v| v[:bidx_attribute] }

    attributes.each_with_index do |attribute, i|
      relation =
        if i == 0
          relation.where(attribute => nil)
        else
          relation.or(model.where(attribute => nil))
        end
    end
  end

  # migrate
  relation.find_each do |record|
    fields.each do |k, v|
      record.send("#{v[:attribute]}=", record.send(k)) if restart || !record.send(v[:encrypted_attribute])
    end
    blind_indexes.each do |k, v|
      record.send("compute_#{k}_bidx") if restart || !record.send(v[:bidx_attribute])
    end
    record.save(validate: false) if record.changed?
  end
end

.pad(str, size: 16) ⇒ Object

ISO/IEC 7816-4 same as Libsodium libsodium.gitbook.io/doc/padding apply prior to encryption note: current implementation does not try to minimize side channels

Raises:

  • (ArgumentError) 


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# File 'lib/lockbox.rb', line 152

def self.pad(str, size: 16)
  raise ArgumentError, "Invalid size" if size < 1

  str = str.dup.force_encoding(Encoding::BINARY)

  pad_length = size - 1
  pad_length -= str.bytesize % size

  str << PAD_FIRST_BYTE
  pad_length.times do
    str << PAD_ZERO_BYTE
  end

  str
end

.to_hex(str) ⇒ Object 



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# File 'lib/lockbox.rb', line 139

def self.to_hex(str)
  str.unpack("H*").first
end

.unpad(str, size: 16) ⇒ Object

note: current implementation does not try to minimize side channels

Raises:

  • (ArgumentError) 


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# File 'lib/lockbox.rb', line 170

def self.unpad(str, size: 16)
  raise ArgumentError, "Invalid size" if size < 1

  if str.encoding != Encoding::BINARY
    str = str.dup.force_encoding(Encoding::BINARY)
  end

  i = 1
  while i <= size
    case str[-i]
    when PAD_ZERO_BYTE
      i += 1
    when PAD_FIRST_BYTE
      return str[0..-(i + 1)]
    else
      break
    end
  end

  raise Lockbox::PaddingError, "Invalid padding"
end

Instance Method Details

#decrypt(ciphertext, **options) ⇒ Object 



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# File 'lib/lockbox.rb', line 87

def decrypt(ciphertext, **options)
  ciphertext = check_string(ciphertext, "ciphertext")

  # ensure binary
  if ciphertext.encoding != Encoding::BINARY
    # dup to prevent mutation
    ciphertext = ciphertext.dup.force_encoding(Encoding::BINARY)
  end

  @boxes.each_with_index do |box, i|
    begin
      return box.decrypt(ciphertext, **options)
    rescue => e
      error_classes = [DecryptionError]
      error_classes << RbNaCl::LengthError if defined?(RbNaCl::LengthError)
      error_classes << RbNaCl::CryptoError if defined?(RbNaCl::CryptoError)
      if error_classes.any? { |ec| e.is_a?(ec) }
        raise DecryptionError, "Decryption failed" if i == @boxes.size - 1
      else
        raise e
      end
    end
  end
end

#encrypt(message, **options) ⇒ Object 



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# File 'lib/lockbox.rb', line 82

def encrypt(message, **options)
  message = check_string(message, "message")
  @boxes.first.encrypt(message, **options)
end