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rails--rails/guides/source/active_record_encryption.md

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**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.**
Active Record Encryption
========================
This guide covers encrypting your database information using Active Record.
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After reading this guide you will know:
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* How to set up database encryption with Active Record.
* How to migrate unencrypted data
* How to make different encryption schemes coexist
* How to use the API
* How to configure the library and how to extend it
--------------------------------------------------------------------------------
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Active Record supports application-level encryption. It works by declaring which attributes should be encrypted and seamlessly encrypting and decrypting them when necessary. The encryption layer is placed between the database and the application. The application will access unencrypted data but the database will store it encrypted.
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## Basic usage
### Setup
First, you need to add some keys to your [rails credentials](/security.html#custom-credentials). Run `bin/rails db:encryption:init` to generate a random key set:
```bash
$ bin/rails db:encryption:init
Add this entry to the credentials of the target environment:
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active_record_encryption:
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primary_key: EGY8WhulUOXixybod7ZWwMIL68R9o5kC
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deterministic_key: aPA5XyALhf75NNnMzaspW7akTfZp0lPY
key_derivation_salt: xEY0dt6TZcAMg52K7O84wYzkjvbA62Hz
```
NOTE: These generated keys and salt are 32 bytes length. If you generate these yourself, the minimum lengths you should use are 12 bytes for the primary key (this will be used to derive the AES 32 bytes key) and 20 bytes for the salt.
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### Declaration of encrypted attributes
Encryptable attributes are defined at the model level. These are regular Active Record attributes backed by a column with the same name.
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```ruby
class Article < ApplicationRecord
encrypts :title
end
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````
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The library will transparently encrypt these attributes before saving them into the database, and will decrypt them when retrieving their values:
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```ruby
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article = Article.create title: "Encrypt it all!"
article.title # => "Encrypt it all!"
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```
But, under the hood, the executed SQL would look like this:
```sql
INSERT INTO `articles` (`title`) VALUES ('{\"p\":\"n7J0/ol+a7DRMeaE\",\"h\":{\"iv\":\"DXZMDWUKfp3bg/Yu\",\"at\":\"X1/YjMHbHD4talgF9dt61A==\"}}')
```
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Encryption takes additional space in the column. You can estimate the worst-case overload in around 250 bytes when the built-in envelope encryption key provider is used. For medium and large text columns this overload is negligible, but for `string` columns of 255 bytes, you should increase their limit accordingly (510 is recommended).
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NOTE: The reason for the additional space are Base 64 encoding and additional metadata stored with the encrypted values.
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### Deterministic and non-deterministic encryption
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By default, Active Record Encryption uses a non-deterministic approach to encryption. This means that encrypting the same content with the same password twice will result in different ciphertexts. This is good for security, since it makes crypto-analysis of encrypted content much harder, but it makes querying the database impossible.
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You can use the `deterministic:` option to generate initialization vectors in a deterministic way, effectively enabling querying encrypted data.
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```ruby
class Author < ApplicationRecord
encrypts :email, deterministic: true
end
Author.find_by_email("some@email.com") # You can query the model normally
```
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The recommendation is using the default (non deterministic) unless you need to query the data.
NOTE: In non-deterministic mode, it uses AES-GCM with a 256-bits key and a random initialization vector. In deterministic mode, it uses AES-GCM too but the initialization vector is generated as a HMAC-SHA-256 digest of the key and contents to encrypt.
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NOTE: You can disable deterministic encryption just by not configuring a `deterministic_key`.
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## Features
### Action Text
You can encrypt action text attributes by passing `encrypted: true` in their declaration.
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```ruby
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class Message < ApplicationRecord
has_rich_text :content, encrypted: true
end
```
NOTE: Passing individual encryption options to action text attributes is not supported yet. It will use non-deterministic encryption with the global encryption options configured.
### Fixtures
You can get Rails fixtures encrypted automatically by adding this option to your `test.rb`:
```ruby
config.active_record.encryption.encrypt_fixtures = true
```
When enabled, all the encryptable attributes will be encrypted according to the encryption settings defined in the model.
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#### Action text fixtures
To encrypt action text fixtures you should place them in `fixtures/action_text/encrypted_rich_texts.yml`.
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### Supported types
`active_record.encryption` will serialize values using the underlying type before encrypting them, but *they must be serializable as strings*. Structured types like `serialized` are supported out of the box.
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If you need to support a custom type, the recommended way is using a [serialized attribute](https://api.rubyonrails.org/classes/ActiveRecord/AttributeMethods/Serialization/ClassMethods.html). The declaration of the serialized attribute should go **before** the encryption declaration:
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```ruby
# GOOD
class Article < ApplicationRecord
serialize :title, Title
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encrypts :title
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end
# WRONG
class Article < ApplicationRecord
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encrypts :title
serialize :title, Title
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end
```
### Ignoring case
You might need to ignore case when querying deterministically encrypted data. There are two options that can help you here.
You can use the `:downcase` option when declaring the encrypted attribute to downcase the content before encryption occurs.
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```ruby
class Person
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encrypts :email_address, deterministic: true, downcase: true
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end
```
When using `:downcase`, the original case is lost. In some situations, you might want to ignore the case only when querying, while also storing the original case. For those situations, you can use the option `:ignore_case`. This requires you to add a new column named `original_<column_name>` to store the content with the case unchanged:
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```ruby
class Label
encrypts :name, deterministic: true, ignore_case: true # the content with the original case will be stored in the column `original_name`
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end
```
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### Support for unencrypted data
To ease migrations of unencrypted data, the library includes the option `config.active_record.encryption.support_unencrypted_data`. When set to `true`:
* Trying to read encrypted attributes that are not encrypted will work normally, without raising any error
* Queries with deterministically-encrypted attributes will include the "clear text" version of them, to support finding both encrypted and unencrypted content. You need to set `config.active_record.encryption.extend_queries = true` to enable this.
**This options is meant to be used in transition periods** while clear data and encrypted data need to coexist. Their value is `false` by default, which is the recommended goal for any application: errors will be raised when working with unencrypted data.
### Support for previous encryption schemes
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Changing encryption properties of attributes can break existing data. For example, imagine you want to make a "deterministic" attribute "not deterministic". If you just change the declaration in the model, reading existing ciphertexts will fail because they are different now.
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To support these situations, you can declare previous encryption schemes that will be used in two scenarios:
* When reading encrypted data, Active Record Encryption will try previous encryption schemes if the current scheme doesn't work.
* When querying deterministic data, it will add ciphertexts using previous schemes to the queries so that queries work seamlessly with data encrypted with different scheme. You need to set `config.active_record.encryption.extend_queries = true` to enable this.
You can configure previous encryption schemes:
* Globally
* On a per-attribute basis
#### Global previous encryption schemes
You can add previous encryption schemes by adding them as list of properties using the `previous` config property in your `application.rb`:
```ruby
config.active_record.encryption.previous = [ { key_provider: MyOldKeyProvider.new } ]
```
#### Per-attribute encryption schemes
Use `:previous` when declaring the attribute:
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```ruby
class Article
encrypts :title, deterministic: true, previous: { deterministic: false }
end
```
#### Encryption schemes and deterministic attributes
When adding previous encryption schemes:
* With **non-deterministic encryption**, new information will always be encrypted with the *newest* (current) encryption scheme.
* With **deterministic encryption**, new information will always be encrypted with the *oldest* encryption scheme by default.
The reason is that, with deterministic encryption, you normally want ciphertexts to remain constant. You can change this behavior by setting `deterministic: { fixed: false }`. In that case, it will use the *newest* encryption scheme for encrypting new data.
### Unique constraints
NOTE: Unique constraints can only be used with data encrypted deterministically.
#### Unique validations
Unique validations are supported normally as long as extended queries are enabled (`config.active_record.encryption.extend_queries = true`).
```ruby
class Person
validates :email_address, uniqueness: true
encrypts :email_address, deterministic: true, downcase: true
end
```
They will also work when combining encrypted and unencrypted data, and when configuring previous encryption schemes.
NOTE: If you want to ignore case make sure to use `downcase:` or `ignore_case:` in the `encrypts` declaration. Using the `case_sensitive:` option in the validation won't work.
#### Unique indexes
To support unique indexes on deterministically-encrypted columns, you need to make sure their ciphertext doesn't ever change.
To encourage this, by default, deterministic attributes will always use the oldest encryption scheme, when multiple encryption schemes are configured. Other than this, it's up to you making sure that encryption properties don't change for these attributes, or the unique indexes won't work.
```ruby
class Person
encrypts :email_address, deterministic: true
end
```
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### Filtering params named as encrypted columns
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By default, encrypted columns are configured to be [automatically filtered in Rails logs](https://guides.rubyonrails.org/action_controller_overview.html#parameters-filtering). You can disable this behavior by adding this to your `application.rb`:
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```ruby
config.active_record.encryption.add_to_filter_parameters = false
```
In case you want exclude specific columns from this automatic filtering, add them to `config.active_record.encryption.excluded_from_filter_parameters`.
## Key management
Key management strategies are implemented by key providers. You can configure key providers globally or on a per-attribute basis.
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### Built-in key providers
#### DerivedSecretKeyProvider
A key provider that will serve keys derived from the provided passwords using PBKDF2.
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```ruby
config.active_record.encryption.key_provider = ActiveRecord::Encryption::DerivedSecretKeyProvider.new(["some passwords", "to derive keys from. ", "These should be in", "credentials"])
```
NOTE: By default, `active_record.encryption` configures a `DerivedSecretKeyProvider` with the keys defined in `active_record.encryption.primary_key`.
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#### EnvelopeEncryptionKeyProvider
Implements a simple [envelope encryption](https://docs.aws.amazon.com/kms/latest/developerguide/concepts.html#enveloping) strategy:
- It generates a random key for each data-encryption operation
- It stores the data-key with the data itself, encrypted with a primary key defined in the credential `active_record.encryption.primary_key`.
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You can configure by adding this to your `application.rb`:
```ruby
config.active_record.encryption.key_provider = ActiveRecord::Encryption::EnvelopeEncryptionKeyProvider.new
```
As with other built-in key providers, you can provide a list of primary keys in `active_record.encryption.primary_key`, to implement key-rotation schemes.
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### Custom key providers
For more advanced key-management schemes, you can configure a custom key provider in a initializer:
```ruby
ActiveRecord::Encryption.key_provider = MyKeyProvider.new
```
A key provider must implement this interface:
```ruby
class MyKeyProvider
def encryption_key
end
def decryption_keys(encrypted_message)
end
end
```
Both methods return `ActiveRecord::Encryption::Key` objects:
- `encryption_key` returns the key used for encrypting some content
- `decryption keys` returns a list of potential keys for decrypting a given message
A key can include arbitrary tags that will be stored unencrypted with the message. You can use `ActiveRecord::Encryption::Message#headers` to examine those values when decrypting.
### Model-specific key providers
You can configure a key provider on a per-class basis with the `:key_provider` option:
```ruby
class Article < ApplicationRecord
encrypts :summary, key_provider: ArticleKeyProvider.new
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end
```
### Model-specific keys
You can configure a given key on a per-class basis with the `:key` option:
```ruby
class Article < ApplicationRecord
encrypts :summary, key: "some secret key for article summaries"
end
```
The key will be used internally to derive the key used to encrypt and decrypt the data.
### Rotating keys
`active_record.encryption` can work with lists of keys, to support implementing key-rotation schemes:
- The **first key** will be used for encrypting new content.
- All the keys will be tried when decrypting content, until one works.
```yml
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active_record
encryption:
primary_key:
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- bc17e7b413fd4720716a7633027f8cc4 # Active, encrypts new content
- a1cc4d7b9f420e40a337b9e68c5ecec6 # Previous keys can still decrypt existing content
key_derivation_salt: a3226b97b3b2f8372d1fc6d497a0c0d3
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```
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This enables workflows where you keep a short list of keys, by adding new keys, re-encrypting content and deleting old keys.
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NOTE: Rotating keys is not currently supported for deterministic encryption.
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NOTE: Active Record Encryption doesn't provide automatic management of key rotation processes yet. All the pieces are there, but this hasn't been implemented yet.
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### Storing key references
There is a setting `active_record.encryption.store_key_references` you can use to make `active_record.encryption` store a reference to the encryption key in the encrypted message itself.
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```ruby
config.active_record.encryption.store_key_references = true
```
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This makes for a more performant decryption since, instead of trying lists of keys, the system can now locate keys directly. The price to pay is storage: encrypted data will be a bit bigger in size.
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## API
### Basic API
ActiveRecord encryption is meant to be used declaratively, but it presents an API for advanced usage scenarios.
#### Encrypt and decrypt
```ruby
article.encrypt # encrypt or re-encrypt all the encryptable attributes
article.decrypt # decrypt all the encryptable attributes
```
#### Read ciphertext
```ruby
article.ciphertext_for(:title)
```
#### Check if attribute is encrypted or not
```ruby
article.encrypted_attribute?(:title)
```
## Configuration
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### Configuration options
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You can configure Active Record Encryption options by setting them in your `application.rb` (most common scenario) or in a specific environment config file `config/environments/<env name>.rb` if you want to set them on a per-environment basis.
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All the config options are namespaced in `active_record.encryption.config`. For example:
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```ruby
config.active_record.encryption.key_provider = ActiveRecord::Encryption::EnvelopeEncryptionKeyProvider.new
config.active_record.encryption.store_key_references = true
config.active_record.encryption.extend_queries = true
```
The available config options are:
| Key | Value |
| ------------------------------------------------------------ | ------------------------------------------------------------ |
| `support_unencrypted_data` | When true, unencrypted data can be read normally. When false, it will raise. Default: false. |
| `extend_queries` | When true, queries referencing deterministically encrypted attributes will be modified to include additional values if needed. Those additional values will be the clean version of the value, when `support_unencrypted_data` is true) and values encrypted with previous encryption schemes if any (as provided with the `previous:` option). Default: false (experimental). |
| `encrypt_fixtures` | When true, encryptable attributes in fixtures will be automatically encrypted when those are loaded. Default: false. |
| `store_key_references` | When true, a reference to the encryption key is stored in the headers of the encrypted message. This makes for a faster decryption when multiple keys are in use. Default: false. |
| `add_to_filter_parameters` | When true, encrypted attribute names are added automatically to the [list of filtered params](https://guides.rubyonrails.org/configuring.html#rails-general-configuration) that won't be shown in logs. Default: true. |
| `excluded_from_filter_parameters` | You can configure a list of params that won't be filtered out when `add_to_filter_parameters` is true. Default: []. |
| `validate_column_size` | Adds a validation based on the column size. This is recommended to prevent storing huge values using highly compressible payloads. Default: true. |
| `primary_key` | The key or lists of keys that is used to derive root data-encryption keys. They way they are used depends on the key provider configured. It's preferred to configure it via a credential `active_record_encryption.primary_key`. |
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| `deterministic_key` | The key or list of keys used for deterministic encryption. It's preferred to configure it via a credential `active_record_encryption.deterministic_key`. |
| `key_derivation_salt` | The salt used when deriving keys. It's preferred to configure it via a credential `active_record_encryption.key_derivation_salt`. |
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NOTE: It's recommended to use Rails built-in credentials support to store keys. If you prefer to set them manually via config properties, make sure you don't commit them with your code (e.g: use environment variables).
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### Encryption contexts
An encryption context defines the encryption components that are used in a given moment. There is a default encryption context based on your global configuration, but you can configure a custom context for a given attribute or when running a specific block of code.
NOTE: Encryption contexts are a flexible but advanced configuration mechanism. Most users should not have to care about them.
The main components of encryption contexts are:
* `encryptor`: exposes the internal API for encrypting and decrypting data. It interacts with a `key_provider` to build encrypted messages and deal with their serialization. The encryption/decryption itself is done by the `cipher` and the serialization by `message_serializer`.
* `cipher` the encryption algorithm itself (Aes 256 GCM)
* `key_provider` serves encryption and decryption keys.
* `message_serializer`: serializes and deserializes encrypted payloads (`Message`).
NOTE: If you decide to build your own `message_serializer`, It's important to use safe mechanisms that can't deserialize arbitrary objects. A common supported scenario is encrypting existing unencrypted data. An attacker can leverage this to enter a tampered payload before encryption takes place and perform RCE attacks. This means custom serializers should avoid `Marshal`, `YAML.load` (use `YAML.safe_load` instead) or `JSON.load` (use `JSON.parse` instead).
#### Global encryption context
The global encryption context is the one used by default and is configured as other configuration properties in your `application.rb` or environment config files.
```ruby
config.active_record.encryption.key_provider = ActiveRecord::Encryption::EnvelopeEncryptionKeyProvider.new
config.active_record_encryption.encryptor = MyEncryptor.new
```
#### Per-attribute encryption contexts
You can override encryption context params by passing them in the attribute declaration:
```ruby
class Attribute
encrypts :title, encryptor: MyAttributeEncryptor.new
end
```
#### Encryption context when running a block of code
You can use `ActiveRecord::Encryption.with_encryption_context` to set an encryption context for a given block of code:
```ruby
ActiveRecord::Encryption.with_encryption_context(encryptor: ActiveRecord::Encryption::NullEncryptor.new) do
...
end
```
#### Built-in encryption contexts
##### Disable encryption
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You can run code without encryption:
```ruby
ActiveRecord::Encryption.without_encryption do
...
end
```
This means that reading encrypted text will return the ciphertext and saved content will be stored unencrypted.
##### Protect encrypted data
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You can run code without encryption but preventing overwriting encrypted content:
```ruby
ActiveRecord::Encryption.protecting_encrypted_data do
...
end
```
This can be handy if you want to protect encrypted data while still letting someone run arbitrary code against it (e.g: in a Rails console).