README.md
<p align="center">
<a href="https://github.com/fnando/attr_keyring/actions?query=workflow%3ATests"><img src="https://github.com/fnando/attr_keyring/workflows/Tests/badge.svg" alt="Tests"></a>
<a href="https://codeclimate.com/github/fnando/attr_keyring"><img src="https://codeclimate.com/github/fnando/attr_keyring/badges/gpa.svg" alt="Code Climate"></a>
<a href="https://rubygems.org/gems/attr_keyring"><img src="https://img.shields.io/gem/v/attr_keyring.svg" alt="Gem"></a>
<a href="https://rubygems.org/gems/attr_keyring"><img src="https://img.shields.io/gem/dt/attr_keyring.svg" alt="Gem"></a>
</p>
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), and can read
encrypted messages if you encode them in base64 (e.g.
`Base64.strict_encode64(encrypted_by_attr_vault)`).
## 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
### Basic usage
```ruby
gem "attr_keyring"
require "keyring"
keyring = Keyring.new(
{"1" => "uDiMcWVNTuz//naQ88sOcN+E40CyBRGzGTT7OkoBS6M="},
digest_salt: "<custom salt>"
)
# STEP 1: Encrypt message using latest encryption key.
encrypted, keyring_id, digest = keyring.encrypt("super secret")
puts "🔒 #{encrypted}"
puts "🔑 #{keyring_id}"
puts "🔎 #{digest}"
# STEP 2: Decrypted message using encryption key defined by keyring id.
decrypted = keyring.decrypt(encrypted, keyring_id)
puts "✉️ #{decrypted}"
```
#### Change encryption algorithm
You can choose between `AES-128-CBC`, `AES-192-CBC` and `AES-256-CBC`. By
default, `AES-128-CBC` will be used.
To specify the encryption algorithm, set the `encryption` option. The following
example uses `AES-256-CBC`.
```ruby
keyring = Keyring.new(
"1" => "uDiMcWVNTuz//naQ88sOcN+E40CyBRGzGTT7OkoBS6M=",
encryptor: Keyring::Encryptor::AES::AES256CBC,
digest_salt: "<custom salt>"
)
```
### Configuration
As far as database schema goes:
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 column must follow the name `encrypted_<column name>`.
3. Optionally, you can also have a `<column name>_digest` to help with searching
(see Lookup section below).
As far as model configuration goes, they're pretty similar, as you can see
below:
#### ActiveRecord
From Rails 5+, ActiveRecord models now inherit from `ApplicationRecord` instead.
This is how you set it up:
```ruby
class ApplicationRecord < ActiveRecord::Base
self.abstract_class = true
include AttrKeyring.active_record
end
```
#### Sequel
Sequel doesn't have an abstract model class (but it could), so you can set up
the model class directly like the following:
```ruby
class User < Sequel::Model
include AttrKeyring.sequel
end
```
### Defining encrypted attributes
To set up your model, you have to define the keyring (set of encryption keys)
and the attributes that will be encrypted. Both ActiveRecord and Sequel have the
same API, so the examples below work for both ORMs.
```ruby
class User < ApplicationRecord
attr_keyring ENV["USER_KEYRING"],
digest_salt: "<custom salt>"
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"
)
user.email
#=> john@example.com
user.keyring_id
#=> 1
user.encrypted_email
#=> WG8Epo0ABz0Z1X5gX7kttc98w9Ei59B5uXGK36Zin9G0VqbxX3naOWOm4RI6w6Uu
```
If you want to store a hash, you can use the `encoder:` option.
```ruby
class User < ApplicationRecord
attr_keyring ENV["USER_KEYRING"],
digest_salt: "<custom salt>"
attr_encrypt :data, encoder: JSON
end
```
An encoder is just an object that responds to the methods `dump(data)` and
`parse(data)`, just like the `JSON` interface. Alternatively, you can use
`AttrKeyring::Encoders::JSON`, which returns hashes with symbolized keys.
### Encryption
By default, AES-128-CBC is the algorithm used for encryption. This algorithm
uses 16 bytes keys, but you're required to use a key that's double the size
because half of that keys will be used to generate the HMAC. The first 16 bytes
will be used as the encryption key, and the last 16 bytes will be used to
generate the HMAC.
Using random data base64-encoded is the recommended way. You can easily generate
keys by using the following command:
```console
$ dd if=/dev/urandom bs=32 count=1 2>/dev/null | openssl base64 -A
qUjOJFgZsZbTICsN0TMkKqUvSgObYxnkHDsazTqE5tM=
```
Include the result of this command in the `value` section of the key description
in the keyring. Half this key is used for encryption, and half for the HMAC.
#### Key size
The key size depends on the algorithm being used. The key size should be double
the size as half of it is used for HMAC computation.
- `aes-128-cbc`: 16 bytes (encryption) + 16 bytes (HMAC).
- `aes-192-cbc`: 24 bytes (encryption) + 24 bytes (HMAC).
- `aes-256-cbc`: 32 bytes (encryption) + 32 bytes (HMAC).
#### 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
`base64(hmac(unencrypted iv + encrypted message) + unencrypted iv + encrypted message)`
as the final message. 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 HMAC is 32-bytes long and
the IV is 16-bytes long.
### 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": "uDiMcWVNTuz//naQ88sOcN+E40CyBRGzGTT7OkoBS6M=",
"2": "VN8UXRVMNbIh9FWEFVde0q7GUA1SGOie1+FgAKlNYHc="
}
```
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), digest_salt: "<custom salt>"`
- `attr_keyring JSON.parse(File.read(keyring_file)), digest_salt: "<custom salt>"`.
### Lookup
One tricky aspect of encryption is looking up records by known secret. E.g.,
```ruby
User.where(email: "john@example.com")
```
is trivial with plain text fields, but impossible with the model defined as
above.
If a column `<attribute>_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. You don't have to use a hashing salt, but it's highly recommended; this
way you can avoid leaking your users' info via rainbow tables.
```ruby
User.where(email: User.keyring.digest("john@example.com")).first
```
### 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
```
### What if I don't use ActiveRecord/Sequel?
You can also leverage the encryption mechanism of `attr_keyring` totally
decoupled from ActiveRecord/Sequel. First, make sure you load `keyring` instead.
Then you can create a keyring to encrypt/decrypt strings, without even touching
the database.
```ruby
require "keyring"
keyring = Keyring.new(
{"1" => "QSXyoiRDPoJmfkJUZ4hJeQ=="},
digest_salt: "<custom salt>"
)
encrypted, keyring_id, digest = keyring.encrypt("super secret")
puts encrypted
#=> encrypted: +mOWmIWKMV01nCm076OBnzgPGhWAZqNs8Etaad/0s3I=
puts keyring_id
#=> 1
puts digest
#=> e24fe0dea7f9abe8cbb192702578715079689a3e
decrypted = keyring.decrypt(encrypted, keyring_id)
puts decrypted
#=> super secret
```
### Exchange data with Node.js
If you use Node.js, you may be interested in
<https://github.com/fnando/keyring-node>, which is able to read and write
messages using the same format.
## 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/main/CODE_OF_CONDUCT.md).