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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"
Namespace
Methods
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Constants
OpenSSLCipherError = OpenSSL::Cipher::CipherError
 
Class Public methods
new(secret, *signature_key_or_options)

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
Instance Public methods
decrypt_and_verify(value)

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)

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