class ActiveSupport::MessageEncryptor

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.

Constants

OpenSSLCipherError

Public Class Methods

new(secret, options = {}) click to toggle source
# File lib/active_support/message_encryptor.rb, line 26
def initialize(secret, options = {})
  unless options.is_a?(Hash)
    ActiveSupport::Deprecation.warn "The second parameter should be an options hash. Use :cipher => 'algorithm' to specify the cipher algorithm."
    options = { :cipher => options }
  end

  @secret = secret
  @cipher = options[:cipher] || 'aes-256-cbc'
  @verifier = MessageVerifier.new(@secret, :serializer => NullSerializer)
  @serializer = options[:serializer] || Marshal
end

Public Instance Methods

decrypt(value) click to toggle source
# File lib/active_support/message_encryptor.rb, line 44
def decrypt(value)
  ActiveSupport::Deprecation.warn "MessageEncryptor#decrypt is deprecated as it is not safe without a signature. "          "Please use MessageEncryptor#decrypt_and_verify instead."
  _decrypt(value)
end
decrypt_and_verify(value) click to toggle 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 lib/active_support/message_encryptor.rb, line 58
def decrypt_and_verify(value)
  _decrypt(verifier.verify(value))
end
encrypt(value) click to toggle source
# File lib/active_support/message_encryptor.rb, line 38
def encrypt(value)
  ActiveSupport::Deprecation.warn "MessageEncryptor#encrypt is deprecated as it is not safe without a signature. "          "Please use MessageEncryptor#encrypt_and_sign instead."
  _encrypt(value)
end
encrypt_and_sign(value) click to toggle 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 lib/active_support/message_encryptor.rb, line 52
def encrypt_and_sign(value)
  verifier.generate(_encrypt(value))
end

Private Instance Methods

_decrypt(encrypted_message) click to toggle source
# File lib/active_support/message_encryptor.rb, line 79
def _decrypt(encrypted_message)
  cipher = new_cipher
  encrypted_data, iv = encrypted_message.split("--").map {|v| ::Base64.decode64(v)}

  cipher.decrypt
  cipher.key = @secret
  cipher.iv  = iv

  decrypted_data = cipher.update(encrypted_data)
  decrypted_data << cipher.final

  @serializer.load(decrypted_data)
rescue OpenSSLCipherError, TypeError
  raise InvalidMessage
end
_encrypt(value) click to toggle source
# File lib/active_support/message_encryptor.rb, line 64
def _encrypt(value)
  cipher = new_cipher
  # Rely on OpenSSL for the initialization vector
  iv = cipher.random_iv

  cipher.encrypt
  cipher.key = @secret
  cipher.iv  = iv

  encrypted_data = cipher.update(@serializer.dump(value))
  encrypted_data << cipher.final

  [encrypted_data, iv].map {|v| ::Base64.strict_encode64(v)}.join("--")
end
new_cipher() click to toggle source
# File lib/active_support/message_encryptor.rb, line 95
def new_cipher
  OpenSSL::Cipher::Cipher.new(@cipher)
end
verifier() click to toggle source
# File lib/active_support/message_encryptor.rb, line 99
def verifier
  @verifier
end