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Class: ActiveSupport::MessageEncryptor

Relationships & Source Files
Namespace Children
Exceptions:
InvalidMessage
Inherits: Object
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"

Constant Summary

Class Method Summary

Instance Method Summary

Constructor Details

.new(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.

[ GitHub ] 

  


# 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)  
  



  

    

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


  



  [ GitHub ]


  

  


# 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)  
  



  

    

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.


  



  [ GitHub ]


  

  


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



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.


  



  [ GitHub ]


  

  


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



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