Class: ActiveSupport::KeyGenerator

Inherits:
Object
  • Object
show all
Defined in:
activesupport/lib/active_support/key_generator.rb

Overview

KeyGenerator is a simple wrapper around OpenSSL's implementation of PBKDF2. It can be used to derive a number of keys for various purposes from a given secret. This lets Rails applications have a single secure secret, but avoid reusing that key in multiple incompatible contexts.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(secret, options = {}) ⇒ KeyGenerator

Returns a new instance of KeyGenerator.


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# File 'activesupport/lib/active_support/key_generator.rb', line 26

def initialize(secret, options = {})
  @secret = secret
  # The default iterations are higher than required for our key derivation uses
  # on the off chance someone uses this for password storage
  @iterations = options[:iterations] || 2**16
  # Also allow configuration here so people can use this to build a rotation
  # scheme when switching the digest class.
  @hash_digest_class = options[:hash_digest_class] || self.class.hash_digest_class
end

Class Method Details

.hash_digest_classObject


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# File 'activesupport/lib/active_support/key_generator.rb', line 21

def hash_digest_class
  @hash_digest_class ||= OpenSSL::Digest::SHA1
end

.hash_digest_class=(klass) ⇒ Object


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# File 'activesupport/lib/active_support/key_generator.rb', line 13

def hash_digest_class=(klass)
  if klass.kind_of?(Class) && klass < OpenSSL::Digest
    @hash_digest_class = klass
  else
    raise ArgumentError, "#{klass} is expected to be an OpenSSL::Digest subclass"
  end
end

Instance Method Details

#generate_key(salt, key_size = 64) ⇒ Object

Returns a derived key suitable for use. The default key_size is chosen to be compatible with the default settings of ActiveSupport::MessageVerifier. i.e. OpenSSL::Digest::SHA1#block_length


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# File 'activesupport/lib/active_support/key_generator.rb', line 39

def generate_key(salt, key_size = 64)
  OpenSSL::PKCS5.pbkdf2_hmac(@secret, salt, @iterations, key_size, @hash_digest_class.new)
end