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'.
:digest
- String of digest to use
for signing. Default is SHA1
.
:serializer
- Object serializer
to use. Default is Marshal
.
# File lib/active_support/message_encryptor.rb, line 45 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
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 63 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 57 def encrypt_and_sign(value) verifier.generate(_encrypt(value)) end
# File lib/active_support/message_encryptor.rb, line 83 def _decrypt(encrypted_message) cipher = new_cipher encrypted_data, iv = encrypted_message.split("--").map {|v| ::Base64.strict_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, ArgumentError raise InvalidMessage end
# File lib/active_support/message_encryptor.rb, line 69 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 "#{::Base64.strict_encode64 encrypted_data}--#{::Base64.strict_encode64 iv}" end
# File lib/active_support/message_encryptor.rb, line 99 def new_cipher OpenSSL::Cipher::Cipher.new(@cipher) end
# File lib/active_support/message_encryptor.rb, line 103 def verifier @verifier end