Class: ActiveSupport::MessageEncryptor

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

Overview

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, 32) # => "\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"

Defined Under Namespace

Modules: NullSerializer, NullVerifier Classes: InvalidMessage

Constant Summary collapse

DEFAULT_CIPHER = 
"aes-256-cbc"
OpenSSLCipherError = 
OpenSSL::Cipher::CipherError

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(secret, *signature_key_or_options) ⇒ MessageEncryptor

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 by using ActiveSupport::KeyGenerator or a similar key derivation function.

First additional parameter is used as the signature key for MessageVerifier. This allows you to specify keys to encrypt and sign data.

ActiveSupport::MessageEncryptor.new('secret', 'signature_secret')

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. Ignored when using an AEAD cipher like ‘aes-256-gcm’.

  • :serializer - Object serializer to use. Default is Marshal.



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# File 'lib/active_support/message_encryptor.rb', line 64

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] || DEFAULT_CIPHER
  @digest = options[:digest] || "SHA1" unless aead_mode?
  @verifier = resolve_verifier
  @serializer = options[:serializer] || Marshal
end

Class Method Details

.key_len(cipher = DEFAULT_CIPHER) ⇒ Object

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



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# File 'lib/active_support/message_encryptor.rb', line 88

def self.key_len(cipher = DEFAULT_CIPHER)
  OpenSSL::Cipher.new(cipher).key_len
end

Instance Method Details

#decrypt_and_verify(value) ⇒ Object

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.



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# File 'lib/active_support/message_encryptor.rb', line 83

def decrypt_and_verify(value)
  _decrypt(verifier.verify(value))
end

#encrypt_and_sign(value) ⇒ Object

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.



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# File 'lib/active_support/message_encryptor.rb', line 77

def encrypt_and_sign(value)
  verifier.generate(_encrypt(value))
end