class ActiveSupport::MessageEncryptor

Parent:: Object

MessageEncryptor is a simple way to encrypt values which get stored somewhere you don't trust.

The cipher text and initialization vector are base64 encoded and returned to you.

This can be used in situations similar to the MessageVerifier, but where you don't want users to be able to determine the value of the payload.

salt  = SecureRandom.random_bytes(64)
key   = ActiveSupport::KeyGenerator.new('password').generate_key(salt) # => "\x89\xE0\x156\xAC..."
crypt = ActiveSupport::MessageEncryptor.new(key)                       # => #<ActiveSupport::MessageEncryptor ...>
encrypted_data = crypt.encrypt_and_sign('my secret data')              # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
crypt.decrypt_and_verify(encrypted_data)                               # => "my secret data"

Constants

OpenSSLCipherError

Public Class Methods

new(secret, *signature_key_or_options) Show source

Initialize a new MessageEncryptor. secret must be at least as long as the cipher key size. For the default 'aes-256-cbc' cipher, this is 256 bits. If you are using a user-entered secret, you can generate a suitable key with OpenSSL::Digest::SHA256.new(user_secret).digest or similar.

Options:

:cipher - Cipher to use. Can be any cipher returned by OpenSSL::Cipher.ciphers. Default is 'aes-256-cbc'.
:serializer - Object serializer to use. Default is Marshal.

# File activesupport/lib/active_support/message_encryptor.rb, line 44
def initialize(secret, *signature_key_or_options)
  options = signature_key_or_options.extract_options!
  sign_secret = signature_key_or_options.first
  @secret = secret
  @sign_secret = sign_secret
  @cipher = options[:cipher] || 'aes-256-cbc'
  @verifier = MessageVerifier.new(@sign_secret || @secret, :serializer => NullSerializer)
  @serializer = options[:serializer] || Marshal
end

Public Instance Methods

decrypt_and_verify(value) Show source

Decrypt and verify a message. We need to verify the message in order to avoid padding attacks. Reference: www.limited-entropy.com/padding-oracle-attacks.

# File activesupport/lib/active_support/message_encryptor.rb, line 62
def decrypt_and_verify(value)
  _decrypt(verifier.verify(value))
end

encrypt_and_sign(value) Show source

Encrypt and sign a message. We need to sign the message in order to avoid padding attacks. Reference: www.limited-entropy.com/padding-oracle-attacks.

# File activesupport/lib/active_support/message_encryptor.rb, line 56
def encrypt_and_sign(value)
  verifier.generate(_encrypt(value))
end