Class: Rack::Protection::EncryptedCookie

Inherits:
Session::Abstract::Persisted
  • Object
show all
Defined in:
lib/rack/protection/encrypted_cookie.rb

Overview

Rack::Protection::EncryptedCookie provides simple cookie based session management. By default, the session is a Ruby Hash stored as base64 encoded marshalled data set to :key (default: rack.session). The object that encodes the session data is configurable and must respond to encode and decode. Both methods must take a string and return a string.

When the secret key is set, cookie data is checked for data integrity. The old_secret key is also accepted and allows graceful secret rotation. A legacy_hmac_secret is also accepted and is used to upgrade existing sessions to the new encryption scheme.

There is also a legacy_hmac_coder option which can be set if a non-default coder was used for legacy session cookies.

Example:

use Rack::Protection::EncryptedCookie,
                           :key => 'rack.session',
                           :domain => 'foo.com',
                           :path => '/',
                           :expire_after => 2592000,
                           :secret => 'change_me',
                           :old_secret => 'old_secret'

All parameters are optional.

Example using legacy HMAC options

Rack::Protection:EncryptedCookie.new(application, {
  # The secret used for legacy HMAC cookies
  legacy_hmac_secret: 'legacy secret',
  # legacy_hmac_coder will default to Rack::Protection::EncryptedCookie::Base64::Marshal
  legacy_hmac_coder: Rack::Protection::EncryptedCookie::Identity.new,
  # legacy_hmac will default to OpenSSL::Digest::SHA1
  legacy_hmac: OpenSSL::Digest::SHA256
})

Example of a cookie with no encoding:

Rack::Protection::EncryptedCookie.new(application, {
  :coder => Rack::Protection::EncryptedCookie::Identity.new
})

Example of a cookie with custom encoding:

Rack::Protection::EncryptedCookie.new(application, {
  :coder => Class.new {
    def encode(str); str.reverse; end
    def decode(str); str.reverse; end
  }.new
})

Defined Under Namespace

Classes: Base64, Identity, Marshal

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(app, options = {}) ⇒ EncryptedCookie

Returns a new instance of EncryptedCookie.



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# File 'lib/rack/protection/encrypted_cookie.rb', line 143

def initialize(app, options = {})
  # Assume keys are hex strings and convert them to raw byte strings for
  # actual key material
  @secrets = options.values_at(:secret, :old_secret).compact.map do |secret|
    [secret].pack('H*')
  end

  warn <<-MSG unless secure?(options)
  SECURITY WARNING: No secret option provided to Rack::Protection::EncryptedCookie.
  This poses a security threat. It is strongly recommended that you
  provide a secret to prevent exploits that may be possible from crafted
  cookies. This will not be supported in future versions of Rack, and
  future versions will even invalidate your existing user cookies.

  Called from: #{caller[0]}.
  MSG

  warn <<-MSG if @secrets.first && @secrets.first.length < 32
  SECURITY WARNING: Your secret is not long enough. It must be at least
  32 bytes long and securely random. To generate such a key for use
  you can run the following command:

  ruby -rsecurerandom -e 'p SecureRandom.hex(32)'

  Called from: #{caller[0]}.
  MSG

  if options.key?(:legacy_hmac_secret)
    @legacy_hmac = options.fetch(:legacy_hmac, OpenSSL::Digest::SHA1)

    # Multiply the :digest_length: by 2 because this value is the length of
    # the digest in bytes but session digest strings are encoded as hex
    # strings
    @legacy_hmac_length = @legacy_hmac.new.digest_length * 2
    @legacy_hmac_secret = options[:legacy_hmac_secret]
    @legacy_hmac_coder  = (options[:legacy_hmac_coder] ||= Base64::Marshal.new)
  else
    @legacy_hmac = false
  end

  # If encryption is used we can just use a default Marshal encoder
  # without Base64 encoding the results.
  #
  # If no encryption is used, rely on the previous default (Base64::Marshal)
  @coder = (options[:coder] ||= (@secrets.any? ? Marshal.new : Base64::Marshal.new))

  super(app, options.merge!(cookie_only: true))
end

Instance Attribute Details

#coder ⇒ Object (readonly)

Returns the value of attribute coder.



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# File 'lib/rack/protection/encrypted_cookie.rb', line 141

def coder
  @coder
end