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

DEFAULT_CIPHER
OpenSSLCipherError

Public Class Methods

key_len(cipher = DEFAULT_CIPHER) Show source

# File activesupport/lib/active_support/message_encryptor.rb, line 70
def self.key_len(cipher = DEFAULT_CIPHER)
  OpenSSL::Cipher.new(cipher).key_len
end

Given a cipher, returns the key length of the cipher to help generate the key of desired size

new(secret, *signature_key_or_options) Show source

# File activesupport/lib/active_support/message_encryptor.rb, line 47
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, digest: options[:digest] || 'SHA1', serializer: NullSerializer)
  @serializer = options[:serializer] || Marshal
end

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'.
:digest - String of digest to use for signing. Default is SHA1.
:serializer - Object serializer to use. Default is Marshal.

Public Instance Methods

decrypt_and_verify(value) Show source

# File activesupport/lib/active_support/message_encryptor.rb, line 65
def decrypt_and_verify(value)
  _decrypt(verifier.verify(value))
end

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.

encrypt_and_sign(value) Show source

# File activesupport/lib/active_support/message_encryptor.rb, line 59
def encrypt_and_sign(value)
  verifier.generate(_encrypt(value))
end

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.