Vault Rails

Vault is the official Rails plugin for interacting with Vault by HashiCorp.

If you're viewing this README from GitHub on the master branch, know that it may contain unreleased features or different APIs than the most recently released version. Please see the Git tag that corresponds to your version of the Vault Rails plugin for the proper documentation.

Table of Contents

1. Quick Start
2. Advanced Configuration
3. Caveats
4. Development

Quick Start

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1. Add to your Gemfile:

   gem "vault-rails", require: false

   and then run the bundle command to install.

2. Create an initializer:

   require "vault/rails"
   
   Vault::Rails.configure do |vault|
     # Use Vault in transit mode for encrypting and decrypting data. If
     # disabled, vault-rails will encrypt data in-memory using a similar
     # algorithm to Vault. The in-memory store uses a predictable encryption
     # which is great for development and test, but should _never_ be used in
     # production. Default: ENV["VAULT_RAILS_ENABLED"].
     vault.enabled = Rails.env.production?
   
     # The name of the application. All encrypted keys in Vault will be
     # prefixed with this application name. If you change the name of the
     # application, you will need to migrate the encrypted data to the new
     # key namespace. Default: ENV["VAULT_RAILS_APPLICATION"].
     vault.application = "my_app"
   
     # The address of the Vault server. Default: ENV["VAULT_ADDR"].
     vault.address = "https://vault.corp"
   
     # The token to communicate with the Vault server.
     # Default: ENV["VAULT_TOKEN"].
     vault.token = "abcd1234"
   end

   For more customization, such as custom SSL certificates, please see the Vault Ruby documentation.

3. Add Vault to the model you want to encrypt:

   class Person < ActiveRecord::Base
     include Vault::EncryptedModel
     vault_attribute :ssn
   end

   Each attribute you want to encrypt must have a corresponding attribute_encrypted column in the database. For the above example:

   class AddEncryptedSSNToPerson < ActiveRecord::Migration
     add_column :people, :ssn_encrypted, :string
   end

   That is it! The plugin will transparently handle the encryption and decryption of secrets with Vault:

   person = Person.new
   person.ssn = "123-45-6789"
   person.save #=> true
   person.ssn_encrypted #=> "vault:v0:EE3EV8P5hyo9h..."

• Note The unencrypted value will still be saved if the attribute referenced has a corresponding column. (i.e. ssn in the case above)

Advanced Configuration

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The following section details some of the more advanced configuration options for vault-rails. As a general rule, you should try to use vault-rails without these options until absolutely necessary.

Specifying the encrypted column

By default, the name of the encrypted column is #{column}_encrypted. This is customizable by setting the :encrypted_column option when declaring the attribute:

vault_attribute :credit_card,
  encrypted_column: :cc_encrypted

• Note Changing this value for an existing application will make existing values no longer decryptable!
• Note This value cannot be the same name as the vault attribute!

Specifying a custom key

By default, the name of the key in Vault is #{app}_#{table}_#{attribute}. This is customizable by setting the :key option when declaring the attribute:

vault_attribute :credit_card,
  key: "pci-data"

• Note Changing this value for an existing application will make existing values no longer decryptable!

Specifying a context (key derivation)

Vault Transit supports key derivation, which allows the same key to be used for multiple purposes by deriving a new key based on a context value.

The context can be specified as a string, symbol, or proc. Symbols (an instance method on the model) and procs are called for each encryption or decryption request, and should return a string.

• Note Changing the context or context generator for an attribute will make existing values no longer decryptable!

String

With a string, all records will use the same context for this attribute:

vault_attribute :credit_card,
  context: "user-cc"

Symbol

When using a symbol, a method will be called on the record to compute the context:

belongs_to :user

vault_attribute :credit_card,
  context: :encryption_context

def encryption_context
  "user_#{user.id}"
end

Proc

Given a proc, it will be called each time to compute the context:

belongs_to :user

vault_attribute :credit_card,
  context: ->(record) { "user_#{record.user.id}" }

The proc must take a single argument for the record.

Specifying a default value

An attribute can specify a default value, which will be set on initialization (.new) or after loading the value from the database. The default will be set if the value is nil.

vault_attribute :access_level,
  default: "readonly"

vault_attribute :metadata,
  serialize: :json,
  default: {}

Specifying a different Vault path

By default, the path to the transit backend in Vault is transit/. This is customizable by setting the :path option when declaring the attribute:

vault_attribute :credit_card,
  path: "transport"

• Note Changing this value for an existing application will make existing values no longer decryptable!

Lazy attribute decryption

By default, vault-rails will decrypt a record’s encrypted attributes on that record’s initialization. You can configure an encrypted model to decrypt attributes lazily, which will prevent communication with Vault until an encrypted attribute’s getter method is called, at which point all of the record’s encrypted attributes will be decrypted. This is useful if you do not always need access to encrypted attributes. For example:

class Person < ActiveRecord::Base
  include Vault::EncryptedModel
  vault_lazy_decrypt!

  vault_attribute :ssn
end

# Without vault_lazy_decrypt:
person = Person.find(id) # Vault communication happens here
person.ssn
# => "123-45-6789"

# With vault_lazy_decrypt:
person = Person.find(id)
person.ssn # Vault communication happens here
# => "123-45-6789"

Single, lazy attribute decryption

By default, vault-rails will decrypt all encrypted attributes on that record’s initialization on a class by class basis. You can configure an encrypted model to decrypt attributes lazily and and individually. This will prevent vault from loading all vault_attributes defined on a class the moment one attribute is requested.

class Person < ActiveRecord::Base
  include Vault::EncryptedModel
  vault_lazy_decrypt!
  vault_single_decrypt!

  vault_attribute :ssn
  vault_attribute :email
end

# Without vault_single_decrypt:
person = Person.find(id) # Vault communication happens here
person.ssn # Vault communication happens here, fetches both ssn and email
# => "123-45-6789"

# With vault_single_decrypt:
person = Person.find(id)
person.ssn # Vault communication happens here, fetches only ssn
# => "123-45-6789"
person.email # Vault communication happens here, fetches only email
# => "[email protected]"

Serialization

By default, all values are assumed to be "text" fields in the database. Sometimes it is beneficial for your application to work with a more flexible data structure (such as a Hash or Array). Vault-rails can automatically serialize and deserialize these structures for you:

vault_attribute :details,
  serialize: :json,
  default: {}

It is recommended to set a default matching type that you're serializing.

• Note You can view the source for the exact serialization and deserialization options, but they are intentionally not customizable and cannot be used for a full object marshal/unmarshal.

Custom Serializers

For customized solutions, you can also pass a module to the :serializer key. This module must have the following API:

module MySerializer
  # @param [String, nil] raw
  # @return [String, nil]
  def self.encode(raw); end

  # @param [String, nil] raw
  # @return [String, nil]
  def self.decode(raw); end
end

Your class must account for nil and "empty" values if necessary. Then specify the class as the serializer:

vault_attribute :details,
  serialize: MySerializer

• Note It is possible to encode and decode entire Ruby objects using a custom serializer. Please do not do that. You will have a bad time.

Custom encoding/decoding

If a custom serializer seems too heavy, you can declare an :encode and :decode proc when declaring the attribute. Both options must be given:

vault_attribute :address,
  encode: ->(raw) { raw.to_s.upcase },
  decode: ->(raw) { raw.to_s }

• Note Changing the algorithm for encoding/decoding for an existing application will probably make the application crash when attempting to retrieve existing values!

Caveats

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Mounting/Creating Keys in Vault

The Vault Rails plugin does not automatically mount a backend. It is assumed the proper backend is mounted and accessible by the given token. You can mount a transit backend like this:

$ vault mount transit

If you are running Vault 0.2.0 or later, the Vault Rails plugin will automatically create keys in the transit backend if it has permission. Here is an example policy to grant permissions:

# Allow renewal of leases for secrets
path "sys/renew/*" {
  policy = "write"
}

# Allow renewal of token leases
path "auth/token/renew/*" {
  policy = "write"
}

path "transit/encrypt/myapp_*" {
  policy = "write"
}

path "transit/decrypt/myapp_*" {
  policy = "write"
}

Note that you will need to have an out-of-band process to renew your Vault token.

For lower versions of Vault, the Vault Rails plugin does not automatically create transit keys in Vault. Instead, you should create keys for each column you plan to encrypt using a different policy, out-of-band from the Rails application. For example:

$ vault write transit/keys/<key> create=1

Unless customized, the name of the key will always be:

<app>_<table>_<column>

So for the example above, the key would be:

my_app_people_ssn

Searching Encrypted Attributes

Because each column is uniquely encrypted, it is not possible to search for a particular plain-text value. For example, if the ssn attribute is encrypted, the following will NOT work:

Person.where(ssn: "123-45-6789")

This is because the database is unaware of the plain-text data (which is part of the security model).

Development

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1. Clone the project on GitHub
2. Create a feature branch
3. Submit a Pull Request

Important Notes:

• All new features must include test coverage. At a bare minimum, Unit tests are required. It is preferred if you include acceptance tests as well.
• The tests must be be idempotent. The HTTP calls made during a test should be able to be run over and over.
• Tests are order independent. The default RSpec configuration randomizes the test order, so this should not be a problem.