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 sits between the database and the application. The application will access unencrypted data, but the database will store it encrypted.
Active Record Encryption exists to protect sensitive information in your application. A typical example is personally identifiable information from users. But why would you want application-level encryption if you are already encrypting your database at rest?
As an immediate practical benefit, encrypting sensitive attributes adds an additional security layer. For example, if an attacker gained access to your database, a snapshot of it, or your application logs, they wouldn't be able to make sense of the encrypted information. Additionally, encryption can prevent developers from unintentionally exposing users' sensitive data in application logs.
But more importantly, by using Active Record Encryption, you define what constitutes sensitive information in your application at the code level. Active Record Encryption enables granular control of data access in your application and services consuming data from your application. For example, consider auditable Rails consoles that protect encrypted data or check the built-in system to [filter controller params automatically](#filtering-params-named-as-encrypted-columns).
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:
NOTE: These generated values are 32 bytes in 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.
Because Base 64 encoding and metadata are stored with the values, encryption requires extra space in the column. You can estimate the worst-case overload at around 250 bytes when the built-in envelope encryption key provider is used. This overload is negligible for medium and large text columns, but for `string` columns of 255 bytes, you should increase their limit accordingly (510 bytes is recommended).
By default, Active Record Encryption uses a non-deterministic approach to encryption. Non-deterministic, in this context, means that encrypting the same content with the same password twice will result in different ciphertexts. This approach improves security by making crypto-analysis of ciphertexts harder, and querying the database impossible.
NOTE: In non-deterministic mode, Active Record uses AES-GCM with a 256-bits key and a random initialization vector. In deterministic mode, it also uses AES-GCM, but the initialization vector is generated as an HMAC-SHA-256 digest of the key and contents to encrypt.
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`:
`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.
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:
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:
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 option is meant to be used during transition periods** while clear data and encrypted data must coexist. Both are set to `false` by default, which is the recommended goal for any application: errors will be raised when working with unencrypted data.
Changing encryption properties of attributes can break existing data. For example, imagine you want to make a deterministic attribute non-deterministic. If you just change the declaration in the model, reading existing ciphertexts will fail because the encryption method is different now.
* When querying deterministic data, it will add ciphertexts using previous schemes so that queries work seamlessly with data encrypted with different schemes. You must set `config.active_record.encryption.extend_queries = true` to enable this.
Typically, with deterministic encryption, you 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.
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.
To encourage this, deterministic attributes will always use the oldest available encryption scheme by default when multiple encryption schemes are configured. Otherwise, it's your job to ensure encryption properties don't change for these attributes, or the unique indexes won't work.
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 the following to your `application.rb`:
In case you want exclude specific columns from this automatic filtering, add them to `config.active_record.encryption.excluded_from_filter_parameters`.
Because encoding is stored along with the encrypted payload, values encrypted deterministically will force UTF-8 encoding by default. Therefore the same value with a different encoding will result in a different ciphertext when encrypted. You usually want to avoid this to keep queries and uniqueness constraints working, so the library will perform the conversion automatically on your behalf.
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.
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.
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.
You can configure `active_record.encryption.store_key_references` to make `active_record.encryption` store a reference to the encryption key in the encrypted message itself.
Doing so makes for more performant decryption because the system can now locate keys directly instead of trying lists of keys. The price to pay is storage: encrypted data will be a bit bigger.
You can configure Active Record Encryption options 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.
| `support_unencrypted_data` | When true, unencrypted data can be read normally. When false, it will raise errors. 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 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 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) and 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 used to derive root data-encryption keys. The way they are used depends on the key provider configured. It's preferred to configure it via a credential `active_record_encryption.primary_key`. |
| `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`. |
| `forced_encoding_for_deterministic_encryption` | The default encoding for attributes encrypted deterministically. You can disable forced encoding by setting this option to `nil`. It's `Encoding::UTF_8` by default. |
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).
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`.
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).
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.
