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"
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 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
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 62 def decrypt_and_verify(value) _decrypt(verifier.verify(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.
# File lib/active_support/message_encryptor.rb, line 56 def encrypt_and_sign(value) verifier.generate(_encrypt(value)) end
# File lib/active_support/message_encryptor.rb, line 82 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
# File lib/active_support/message_encryptor.rb, line 68 def _encrypt(value) cipher = new_cipher cipher.encrypt cipher.key = @secret # Rely on OpenSSL for the initialization vector iv = cipher.random_iv encrypted_data = cipher.update(@serializer.dump(value)) encrypted_data << cipher.final [encrypted_data, iv].map {|v| ::Base64.strict_encode64(v)}.join("--") end
# File lib/active_support/message_encryptor.rb, line 98 def new_cipher OpenSSL::Cipher::Cipher.new(@cipher) end
# File lib/active_support/message_encryptor.rb, line 102 def verifier @verifier end