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Generates attr_accessors that encrypt and decrypt attributes
tag: 1.0.4

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README.markdown

attr_encrypted

Generates attr_accessors that encrypt and decrypt attributes transparently

Works with ANY class including ActiveRecord and DataMapper

Installation

gem install shuber-attr_encrypted --source http://gems.github.com

Usage

Basic

Encrypting attributes has never been easier:

class User
  attr_accessor :name
  attr_encrypted :ssn, :key => 'a secret key'

  def load
    # loads the stored data
  end

  def save
    # saves the :name and :encrypted_ssn attributes somewhere (e.g. filesystem, database, etc)
  end
end

@user = User.new
@user.ssn = '123-45-6789'
@user.encrypted_ssn # returns the encrypted version of :ssn
@user.save

@user = User.load
@user.ssn # decrypts :encrypted_ssn and returns '123-45-6789'

Specifying the encrypted attribute name

By default, the encrypted attribute name is encrypted_#{attribute} (e.g. attr_encrypted :email would create an attribute named encrypted_email). You have a couple of options if you want to name your attribute something else.

The :attribute option

You can simply pass the name of the encrypted attribute as the :attribute option:

class User
  attr_encrypted :email, :key => 'a secret key', :attribute => 'email_encrypted'
end

This would generate an attribute named email_encrypted

The :prefix and :suffix options

If you're planning on encrypting a few different attributes and you don't like the encrypted_#{attribute} naming convention then you can specify your own:

class User
  attr_encrypted :email, :credit_card, :ssn, :key => 'a secret key', :prefix => 'secret_', :suffix => '_crypted'
end

This would generate the following attributes: secret_email_crypted, secret_credit_card_crypted, and secret_ssn_crypted.

Encryption keys

Although a :key option may not be required (see custom encryptor below), it has a few special features

Unique keys for each attribute

You can specify unique keys for each attribute if you'd like:

class User
  attr_encrypted :email, :key => 'a secret key'
  attr_encrypted :ssn, :key => 'a different secret key'
end

Symbols representing instance methods as keys

If your class has an instance method that determines the encryption key to use, simply pass a symbol representing it like so:

class User
  attr_encrypted :email, :key => :encryption_key

  def encryption_key
    # does some fancy logic and returns an encryption key
  end
end

Procs as keys

You can pass a proc/lambda object as the :key option as well:

class User
  attr_encrypted :email, :key => proc { |user| ... }
end

Conditional encrypting

There may be times that you want to only encrypt when certain conditions are met. For example maybe you're using rails and you don't want to encrypt attributes when you're in development mode. You can specify conditions like this:

class User < ActiveRecord::Base
  attr_encrypted :email, :key => 'a secret key', :unless => Rails.env.development?
end

You can specify both :if and :unless options. If you pass a symbol representing an instance method then the result of the method will be evaluated. Any objects that respond to :call are evaluated as well.

Custom encryptor

The Huberry::Encryptor class is used by default. You may use your own custom encryptor by specifying the :encryptor, :encrypt_method, and :decrypt_method options

Lets suppose you'd like to use this custom encryptor class:

class SillyEncryptor
  def self.silly_encrypt(options)
    (options[:value] + options[:secret_key]).reverse
  end

  def self.silly_decrypt(options)
    options[:value].reverse.gsub(/#{options[:secret_key]}$/, '')
  end
end

Simply set up your class like so:

class User
  attr_encrypted :email, :secret_key => 'a secret key', :encryptor => SillyEncryptor, :encrypt_method => :silly_encrypt, :decrypt_method => :silly_decrypt
end

Any options that you pass to attr_encrypted will be passed to the encryptor along with the :value option which contains the string to encrypt/decrypt. Notice it uses :secret_key instead of :key.

Custom algorithms

The default Huberry::Encryptor uses the standard ruby OpenSSL library. It's default algorithm is aes-256-cbc. You can modify this by passing the :algorithm option to the attr_encrypted call like so:

class User
  attr_encrypted :email, :key => 'a secret key', :algorithm => 'bf'
end

Run openssl list-cipher-commands to view a list of algorithms supported on your platform. See http://github.com/shuber/encryptor for more information.

aes-128-cbc
aes-128-ecb
aes-192-cbc
aes-192-ecb
aes-256-cbc
aes-256-ecb
base64
bf
bf-cbc
bf-cfb
bf-ecb
bf-ofb
cast
cast-cbc
cast5-cbc
cast5-cfb
cast5-ecb
cast5-ofb
des
des-cbc
des-cfb
des-ecb
des-ede
des-ede-cbc
des-ede-cfb
des-ede-ofb
des-ede3
des-ede3-cbc
des-ede3-cfb
des-ede3-ofb
des-ofb
des3
desx
idea
idea-cbc
idea-cfb
idea-ecb
idea-ofb
rc2
rc2-40-cbc
rc2-64-cbc
rc2-cbc
rc2-cfb
rc2-ecb
rc2-ofb
rc4
rc4-40

Default options

Let's imagine that you have a few attributes that you want to encrypt with different keys, but you don't like the encrypted_#{attribute} naming convention. Instead of having to define your class like this:

class User
  attr_encrypted :email, :key => 'a secret key', :prefix => '', :suffix => '_crypted'
  attr_encrypted :ssn, :key => 'a different secret key', :prefix => '', :suffix => '_crypted'
  attr_encrypted :credit_card, :key => 'another secret key', :prefix => '', :suffix => '_crypted'
end

You can simply define some default options like so:

class User
  attr_encrypted_options.merge!(:prefix => '', :suffix => '_crypted')
  attr_encrypted :email, :key => 'a secret key'
  attr_encrypted :ssn, :key => 'a different secret key'
  attr_encrypted :credit_card, :key => 'another secret key'
end

This should help keep your classes clean and DRY.

Encoding

You're probably going to be storing your encrypted attributes somehow (e.g. filesystem, database, etc) and may run into some issues trying to store a weird encrypted string. I've had this problem myself using MySQL. You can simply pass the :encode option to automatically encode/decode when encrypting/decrypting.

class User
  attr_encrypted :email, :key => 'some secret key', :encode => true
end

The default encoding is m* (base64). You can change this by setting :encode => 'some encoding'. See Array#pack for more encoding options.

Marshaling

You may want to encrypt objects other than strings (e.g. hashes, arrays, etc). If this is the case, simply pass the :marshal option to automatically marshal when encrypting/decrypting.

class User
  attr_encrypted :credentials, :key => 'some secret key', :marshal => true
end

Encrypt/decrypt attribute methods

If you use the same key to encrypt every record (per attribute) like this:

class User
  attr_encrypted :email, :key => 'a secret key'
end

Then you'll have these two class methods available for each attribute: User.encrypt_email(email_to_encrypt) and User.decrypt_email(email_to_decrypt). This can be useful when you're using ActiveRecord (see below).

DataMapper

For your convenience, the :encode and :marshal options are set to true by default since you'll be storing everything in a database.

ActiveRecord

If you're using this gem with ActiveRecord, you get a few extra features:

Default options

Just like the default options for DataMapper, the :encode and :marshal options are set to true by default since you'll be storing everything in a database.

Dynamic find_by_ and scoped_by_ methods

Let's say you'd like to encrypt your user's email addresses, but you also need a way for them to login. Simply set up your class like so:

class User < ActiveRecord::Base
  attr_encrypted :email, :key => 'a secret key'
  attr_encrypted :password, :key => 'some other secret key'
end

You can now lookup and login users like so:

User.find_by_email_and_password('test@example.com', 'testing')

The call to find_by_email_and_password is intercepted and modified to find_by_encrypted_email_and_encrypted_password('ENCRYPTED EMAIL', 'ENCRYPTED PASSWORD'). The dynamic scope methods like scoped_by_email_and_password work the same way.

NOTE: This only works if all records are encrypted with the same encryption key (per attribute).

Contact

Problems, comments, and suggestions all welcome: shuber@huberry.com

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