Class: ActiveSupport::MessageEncryptor

Inherits:
Object
  • Object
show all
Defined in:
activesupport/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) # => "\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 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 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.


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# File 'activesupport/lib/active_support/message_encryptor.rb', line 47

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

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 'activesupport/lib/active_support/message_encryptor.rb', line 70

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 'activesupport/lib/active_support/message_encryptor.rb', line 65

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 'activesupport/lib/active_support/message_encryptor.rb', line 59

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