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class ActiveSupport::MessageEncryptors

Inherits From

Attributes

[RW] transitional

If true, the first two rotation option sets are swapped when building message encryptors. For example, with the following configuration, message encryptors will encrypt messages using serializer: Marshal, url_safe: true, and will able to decrypt messages that were encrypted using any of the three option sets:

encryptors = ActiveSupport::MessageEncryptors.new { ... }
encryptors.rotate(serializer: JSON, url_safe: true)
encryptors.rotate(serializer: Marshal, url_safe: true)
encryptors.rotate(serializer: Marshal, url_safe: false)
encryptors.transitional = true

This can be useful when performing a rolling deploy of an application, wherein servers that have not yet been updated must still be able to decrypt messages from updated servers. In such a scenario, first perform a rolling deploy with the new rotation (e.g. serializer: JSON, url_safe: true) as the first rotation and transitional = true. Then, after all servers have been updated, perform a second rolling deploy with transitional = false.

Public instance methods

[](salt)

Returns a MessageEncryptor configured with a secret derived from the given salt, and options from rotate. MessageEncryptor instances will be memoized, so the same salt will return the same instance.

GitHub

[]=(salt, encryptor)

Overrides a MessageEncryptor instance associated with a given salt.

GitHub

clear_rotations

Clears the list of option sets.

GitHub

initialize(&secret_generator)

Initializes a new instance. secret_generator must accept a salt and a secret_length kwarg, and return a suitable secret (string) or secrets (array of strings). secret_generator may also accept other arbitrary kwargs. If rotate is called with any options matching those kwargs, those options will be passed to secret_generator instead of to the message encryptor.

encryptors = ActiveSupport::MessageEncryptors.new do |salt, secret_length:, base:|
  MySecretGenerator.new(base).generate(salt, secret_length)
end

encryptors.rotate(base: "...")

GitHub

on_rotation(&callback)

Sets a callback to invoke when a message is decrypted using an option set other than the first.

For example, this callback could log each time it is called, and thus indicate whether old option sets are still in use or can be removed from rotation.

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rotate(**options) rotate(&block)

Adds options to the list of option sets. Messages will be encrypted using the first set in the list. When decrypting, however, each set will be tried, in order, until one succeeds.

Notably, the :secret_generator option can specify a different secret generator than the one initially specified. The secret generator must respond to call, accept a salt and a secret_length kwarg, and return a suitable secret (string) or secrets (array of strings). The secret generator may also accept other arbitrary kwargs.

If any options match the kwargs of the operative secret generator, those options will be passed to the secret generator instead of to the message encryptor.

For fine-grained per-salt rotations, a block form is supported. The block will receive the salt, and should return an appropriate options Hash. The block may also return nil to indicate that the rotation does not apply to the given salt. For example:

encryptors = ActiveSupport::MessageEncryptors.new { ... }

encryptors.rotate do |salt|
  case salt
  when :foo
    { serializer: JSON, url_safe: true }
  when :bar
    { serializer: Marshal, url_safe: true }
  end
end

encryptors.rotate(serializer: Marshal, url_safe: false)

# Uses `serializer: JSON, url_safe: true`.
# Falls back to `serializer: Marshal, url_safe: false`.
encryptors[:foo]

# Uses `serializer: Marshal, url_safe: true`.
# Falls back to `serializer: Marshal, url_safe: false`.
encryptors[:bar]

# Uses `serializer: Marshal, url_safe: false`.
encryptors[:baz]

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rotate_defaults

Invokes rotate with the default options.

GitHub

Definition files