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# Config Encryption Plugin Spec

## Scope

The encryption plugin type lets Nacos encrypt and decrypt configuration content
without hard-coding one cryptographic algorithm into the config module.

Encrypted config items are identified by the `cipher-{algorithm}-` dataId
prefix. The algorithm part selects an `EncryptionPluginService` whose
`algorithmName()` matches the prefix. Common lifecycle and state rules are
defined by the [Nacos Plugin Spec](plugin-spec.md).

The plugin separates the encryption algorithm from the config domain. The config
domain still owns dataId, group, namespace, history, listener, and publication
semantics according to the [resource model](../design/resource-model-spec.md)
and [HTTP API](../http-api/api-spec.md) contracts.

## Concepts

| Concept | Meaning |
|---------|---------|
| Algorithm name | Stable route key embedded in `cipher-{algorithm}-`. |
| Data key | Per-config key material used to encrypt content. |
| Protected data key | Data key after plugin-specific wrapping or encryption. |
| Cipher dataId | User-visible dataId prefix that declares encrypted content. |

## SPI

Plugins implement `EncryptionPluginService`.

| Method | Requirement |
|--------|-------------|
| `algorithmName()` | Stable algorithm name used for routing. |
| `generateSecretKey()` | Generate a per-config data key or key material. |
| `encrypt(secretKey, content)` | Encrypt plaintext content. |
| `decrypt(secretKey, content)` | Decrypt ciphertext content. |
| `encryptSecretKey(secretKey)` | Protect the stored data key. |
| `decryptSecretKey(secretKey)` | Recover the stored data key. |

The plugin is exposed to the core plugin manager as type `encryption`.

## Java Client Integration

The Java client integrates encryption through the config filter chain. It loads
`IConfigFilter` implementations with Java `ServiceLoader`; the built-in
`ConfigEncryptionFilter` is registered in the client artifact and delegates to
`EncryptionHandler`.

`ConfigEncryptionFilter` behavior:

| Direction | Behavior |
|-----------|----------|
| Publish request | When `dataId` starts with `cipher-{algorithm}-`, encrypt content before transport and set `encryptedDataKey`. |
| Query response | When `dataId` starts with `cipher-{algorithm}-`, decrypt content after receiving ciphertext and `encryptedDataKey`. |

The same `EncryptionPluginService` algorithm name is used on client and server.
If client-side encryption is expected, the client classpath must contain the
matching encryption plugin implementation. If only server-side encryption is
expected, the server may encrypt or decrypt through its own plugin path, but the
client must still preserve `encryptedDataKey` in request and response models.

Client config filters are Java Client SDK extensions. They are not listed or
enabled by the server plugin Admin API, and their order is controlled by
`IConfigFilter#getOrder()`.

## Data Model

Encrypted configs must store the encrypted content and the protected data key.
The config persistence schema contains `encrypted_data_key` for this purpose.
Plain config data keeps `encrypted_data_key` empty. Persistence and dump
boundaries are defined by the
[Persistence And Dump Spec](../design/foundation-persistence-dump-spec.md).

The dataId prefix is part of the user-visible contract:

```text
cipher-{algorithm}-{actualDataId}
```

Example:

```text
cipher-aes-application-dev.yml
```

## Execution Rules

- Client-published encrypted config should be encrypted before transport when a
  matching client-side filter and algorithm plugin are available.
- Console-published encrypted config is processed on the server side.
- Reads must decrypt only when the selected algorithm plugin is available and
  enabled.
- Missing or disabled encryption plugins must fail explicitly rather than
  returning ciphertext as plaintext.
- Non-encrypted config must not be routed to encryption plugins.
- History and dump flows must preserve both ciphertext and protected data key.

The Nacos server repository defines the encryption SPI and routing behavior. An
algorithm implementation is provided by a plugin package on the server and, when
client-side encryption is expected, by a matching client filter.

## Security Requirements

Encryption plugins must not log plaintext, raw keys, or protected key material.
Algorithm names must be stable and lower-case friendly because they appear in
dataIds. Key generation and key wrapping must be deterministic only when the
algorithm explicitly requires it.

Plugins must document:

- cryptographic algorithm and mode;
- key generation source;
- protected data key format;
- whether client-side and server-side encryption are both supported;
- migration behavior when algorithm names or key wrapping formats change.