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110 lines
4.6 KiB
Markdown
110 lines
4.6 KiB
Markdown
Authentication
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==============
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Unlike Web applications, RESTful APIs should be stateless, which means sessions or cookies should not
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be used. Therefore, each request should come with some sort of authentication credentials because
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the user authentication status may not be maintained by sessions or cookies. A common practice is
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to send a secret access token with each request to authenticate the user. Since an access token
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can be used to uniquely identify and authenticate a user, **the API requests should always be sent
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via HTTPS to prevent from man-in-the-middle (MitM) attacks**.
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There are different ways to send an access token:
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* [HTTP Basic Auth](http://en.wikipedia.org/wiki/Basic_access_authentication): the access token
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is sent as the username. This is should only be used when an access token can be safely stored
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on the API consumer side. For example, the API consumer is a program running on a server.
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* Query parameter: the access token is sent as a query parameter in the API URL, e.g.,
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`https://example.com/users?access-token=xxxxxxxx`. Because most Web servers will keep query
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parameters in server logs, this approach should be mainly used to serve `JSONP` requests which
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cannot use HTTP headers to send access tokens.
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* [OAuth 2](http://oauth.net/2/): the access token is obtained by the consumer from an authorization
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server and sent to the API server via [HTTP Bearer Tokens](http://tools.ietf.org/html/rfc6750),
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according to the OAuth2 protocol.
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Yii supports all of the above authentication methods. You can also easily create new authentication methods.
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To enable authentication for your APIs, do the following two steps:
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1. Specify which authentication methods you plan to use by configuring the `authenticator` behavior
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in your REST controller classes.
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2. Implement [[yii\web\IdentityInterface::findIdentityByAccessToken()]] in your [[yii\web\User::identityClass|user identity class]].
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For example, to use HTTP Basic Auth, you may configure `authenticator` as follows,
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```php
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use yii\filters\auth\HttpBasicAuth;
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public function behaviors()
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{
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$behaviors = parent::behaviors();
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$behaviors['authenticator'] = [
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'class' => HttpBasicAuth::className(),
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];
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return $behaviors;
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}
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```
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If you want to support all three authentication methods explained above, you can use `CompositeAuth` like the following,
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```php
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use yii\filters\auth\CompositeAuth;
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use yii\filters\auth\HttpBasicAuth;
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use yii\filters\auth\HttpBearerAuth;
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use yii\filters\auth\QueryParamAuth;
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public function behaviors()
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{
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$behaviors = parent::behaviors();
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$behaviors['authenticator'] = [
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'class' => CompositeAuth::className(),
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'authMethods' => [
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HttpBasicAuth::className(),
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HttpBearerAuth::className(),
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QueryParamAuth::className(),
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],
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];
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return $behaviors;
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}
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```
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Each element in `authMethods` should be an auth method class name or a configuration array.
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Implementation of `findIdentityByAccessToken()` is application specific. For example, in simple scenarios
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when each user can only have one access token, you may store the access token in an `access_token` column
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in the user table. The method can then be readily implemented in the `User` class as follows,
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```php
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use yii\db\ActiveRecord;
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use yii\web\IdentityInterface;
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class User extends ActiveRecord implements IdentityInterface
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{
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public static function findIdentityByAccessToken($token, $type = null)
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{
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return static::findOne(['access_token' => $token]);
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}
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}
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```
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After authentication is enabled as described above, for every API request, the requested controller
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will try to authenticate the user in its `beforeAction()` step.
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If authentication succeeds, the controller will perform other checks (such as rate limiting, authorization)
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and then run the action. The authenticated user identity information can be retrieved via `Yii::$app->user->identity`.
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If authentication fails, a response with HTTP status 401 will be sent back together with other appropriate headers
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(such as a `WWW-Authenticate` header for HTTP Basic Auth).
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## Authorization <a name="authorization"></a>
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After a user is authenticated, you probably want to check if he or she has the permission to perform the requested
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action for the requested resource. This process is called *authorization* which is covered in detail in
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the [Authorization section](authorization.md).
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If your controllers extend from [[yii\rest\ActiveController]], you may override
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the [[yii\rest\Controller::checkAccess()|checkAccess()]] method to perform authorization check. The method
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will be called by the built-in actions provided by [[yii\rest\ActiveController]].
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