N.B.: attr_keyring is *not* for encrypting passwords--for that, you should use something like [bcrypt](https://github.com/codahale/bcrypt-ruby). It's meant for encrypting sensitive data you will need to access in plain text (e.g. storing OAuth token from users). Passwords do not fall in that category.
This library is heavily inspired by [attr_vault](https://github.com/uhoh-itsmaciek/attr_vault) but it's not a direct port and same keys won't work here without some manual intervention.
## Installation
Add this line to your application's Gemfile:
```ruby
gem "attr_keyring"
```
And then execute:
$ bundle
Or install it yourself as:
$ gem install attr_keyring
## Usage
### Model Configuration
#### Migration
1. You'll need a column to track the key that was used for encryption; by default it's called `keyring_id`.
2. Every encrypted columns must follow the name `encrypted_`.
3. Optionally, you can also have a `_digest` to help with searching (see Lookup section below).
The following example shows how to create a column `twitter_oauth_token` without the digest, and another one called `social_security_number` with the digest column.
```ruby
class CreateUsers < ActiveRecord::Migration[5.2]
def change
create_table :users do |t|
t.citext :email, null: false
t.timestamps
# The following columns are used for encryption.
t.binary :encrypted_twitter_oauth_token
t.binary :encrypted_social_security_number
t.text :social_security_number_digest
t.integer :keyring_id
end
add_index :users, :email, unique: true
add_index :users, :social_security_number_digest, unique: true
end
end
```
#### ActiveRecord
```ruby
class ApplicationRecord < ActiveRecord::Base
self.abstract_class = true
include AttrKeyring
end
class User < ApplicationRecord
attr_keyring ENV["USER_KEYRING"]
attr_encrypt :twitter_oauth_token, :social_security_number
end
```
The code above will encrypt your columns with the current key. If you're updating a record, then the column will be migrated to the latest key available.
You can use the model as you would normally do.
```ruby
user = User.create(
email: "john@example.com",
twitter_oauth_token: "TOKEN",
social_security_number: "SSN"
)
user.twitter_oauth_token
#=> TOKEN
user.keyring_id
#=> 1
user.encrypted_twitter_oauth_token
#=> "\xF0\xFD\xE3\x98\x98\xBBBp\xCCV45\x17\xA8\xF2r\x99\xC8W\xB2i\xD0;\xC2>7[\xF0R\xAC\x00s\x8F\x82QW{\x0F\x01\x88\x86\x03w\x0E\xCBJ\xC6q"
```
### Encryption
By default, AES-128-CBC is the algorithm used for encryption. This algorithm uses 16 bytes keys. Using 16-bytes of random data base64-encoded is the recommended way. You can easily generate keys by using the following command:
```console
$ dd if=/dev/urandom bs=16 count=1 2>/dev/null | openssl base64
```
Include the result of this in the `value` section of the key description in the keyring.
You can also use AES-256-CBC, which uses 32-bytes keys. To specify the encryptor when defining the keyring, use `encryptor: AttrKeyring::Encryptor::AES256CBC`.
```ruby
class User < ApplicationRecord
attr_keyring ENV["USER_KEYRING"],
encryptor: AttrKeyring::Encryptor::AES256CBC
end
```
To generate keys, use `bs=32` instead.
```console
$ dd if=/dev/urandom bs=32 count=1 2>/dev/null | openssl base64
```
#### About the encrypted message
Initialization vectors (IV) should be unpredictable and unique; ideally, they will be cryptographically random. They do not have to be secret: IVs are typically just added to ciphertext messages unencrypted. It may sound contradictory that something has to be unpredictable and unique, but does not have to be secret; it is important to remember that an attacker must not be able to predict ahead of time what a given IV will be.
With that in mind, attr_keyring uses `unencrypted iv + encrypted message` as the value of `encrypted_`. If you're planning to migrate from other encryption mechanisms or read encrypted values from the database without using attr_keyring, make sure you account for this. The IV length can be retrieved by `OpenSSL::Cipher#iv_len`, e.g. `OpenSSL::Cipher.new("AES-128-CBC").iv_len`.
### Keyring
Keys are managed through a keyring--a short JSON document describing your encryption keys. The keyring must be a JSON object mapping numeric ids of the keys to the key values. A keyring must have at least one key. For example:
```json
{
"1": "QSXyoiRDPoJmfkJUZ4hJeQ==",
"2": "r6AfOeilPDJomFsiOXLdfQ=="
}
```
The `id` is used to track which key encrypted which piece of data; a key with a larger id is assumed to be newer. The value is the actual bytes of the encryption key.
#### Dynamically loading keyring
If you're using Rails 5.2+, you can use credentials to define your keyring. Your `credentials.yml` must be define like the following:
```yaml
user_keyring:
1: "QSXyoiRDPoJmfkJUZ4hJeQ=="
2: "r6AfOeilPDJomFsiOXLdfQ=="
```
Then you can setup your model by using `attr_keyring Rails.application.credentials.user_keyring`.
Other possibilities (e.g. the keyring file is provided by configuration management):
- `attr_keyring YAML.load_file(keyring_file)`
- `attr_keyring JSON.parse(File.read(keyring_file))`.
### Lookup
One tricky aspect of encryption is looking up records by known secret. E.g.,
```ruby
User.where(twitter_oauth_token: "241F596D-79FF-4C08-921A-A19E533B4F52")
```
is trivial with plain text fields, but impossible with the model defined as above.
If add a column `_digest` exists, then a SHA1 digest from the value will be saved. This will allow you to lookup by that value instead and add unique indexes.
```ruby
User.where(twitter_oauth_token_digest: Digest::SHA1.hexdigest("241F596D-79FF-4C08-921A-A19E533B4F52"))
```
### Key Rotation
Because attr_keyring uses a keyring, with access to multiple keys at once, key rotation is fairly straightforward: if you add a key to the keyring with a higher id than any other key, that key will automatically be used for encryption when records are either created or updated. Any keys that are no longer in use can be safely removed from the keyring.
To check if an existing key with id `123` is still in use, run:
```ruby
# For a large dataset, you may want to index the `keyring_id` column.
User.where(keyring_id: 123).empty?
```
You may not want to wait for records to be updated (e.g. key leaking). In that case, you can rollout a key rotation:
```ruby
User.where(keyring_id: 1234).find_each do |user|
user.keyring_rotate!
end
```
## Development
After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake test` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
## Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/fnando/attr_keyring. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.
## License
The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).
## Icon
Icon made by [Icongeek26](https://www.flaticon.com/authors/icongeek26) from [Flaticon](https://www.flaticon.com/) is licensed by Creative Commons BY 3.0.
## Code of Conduct
Everyone interacting in the attr_keyring project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the [code of conduct](https://github.com/fnando/attr_keyring/blob/master/CODE_OF_CONDUCT.md).