yiisoft / csrf
Yii CSRF Protection Library
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Requires
- php: ^7.4|^8.0
- ext-hash: *
- psr/http-factory: ^1.0
- psr/http-factory-implementation: 1.0
- psr/http-message: ^1.0|^2.0
- psr/http-message-implementation: 1.0
- psr/http-server-handler: ^1.0
- psr/http-server-middleware: ^1.0
- yiisoft/http: ^1.2
- yiisoft/security: ^1.0
- yiisoft/session: ^1.0|^2.0
- yiisoft/strings: ^2.0
Requires (Dev)
- maglnet/composer-require-checker: ^3.8|^4.2
- nyholm/psr7: ^1.3
- phpunit/phpunit: ^9.5
- rector/rector: ^1.0.0
- roave/infection-static-analysis-plugin: ^1.16
- spatie/phpunit-watcher: ^1.23
- vimeo/psalm: ^4.30|^5.24
- yiisoft/di: ^1.1
README
Yii CSRF Protection Library
The package provides PSR-15 middleware for CSRF protection:
- It supports two algorithms out of the box:
- Synchronizer CSRF token with customizable token generation and storage. By default, it uses random data and session.
- HMAC based token with customizable identity generation. Uses session by default.
- It has ability to apply masking to CSRF token string to make BREACH attack impossible.
Requirements
- PHP 7.4 or higher.
Installation
The package could be installed with Composer:
composer require yiisoft/csrf
General usage
In order to enable CSRF protection you need to add CsrfTokenMiddleware
to your main middleware stack.
In Yii it is done by configuring config/web/application.php
:
return [ Yiisoft\Yii\Http\Application::class => [ '__construct()' => [ 'dispatcher' => DynamicReference::to(static function (Injector $injector) { return ($injector->make(MiddlewareDispatcher::class)) ->withMiddlewares( [ ErrorCatcher::class, SessionMiddleware::class, CsrfTokenMiddleware::class, // <-- add this Router::class, ] ); }), ], ], ];
By default, CSRF token is obtained from _csrf
request body parameter or X-CSRF-Token
header.
You can access currently valid token as a string using CsrfTokenInterface
:
/** @var Yiisoft\Csrf\CsrfTokenInterface $csrfToken */ $csrf = $csrfToken->getValue();
If the token does not pass validation, the response 422 Unprocessable Entity
will be returned.
You can change this behavior by implementing your own request handler:
use Psr\Http\Message\ResponseFactoryInterface; use Psr\Http\Message\ServerRequestInterface; use Psr\Http\Server\RequestHandlerInterface; use Yiisoft\Csrf\CsrfTokenMiddleware; /** * @var Psr\Http\Message\ResponseFactoryInterface $responseFactory * @var Yiisoft\Csrf\CsrfTokenInterface $csrfToken */ $failureHandler = new class ($responseFactory) implements RequestHandlerInterface { private ResponseFactoryInterface $responseFactory; public function __construct(ResponseFactoryInterface $responseFactory) { $this->responseFactory = $responseFactory; } public function handle(ServerRequestInterface $request): ResponseInterface { $response = $this->responseFactory->createResponse(400); $response ->getBody() ->write('Bad request.'); return $response; } }; $middleware = new CsrfTokenMiddleware($responseFactory, $csrfToken, $failureHandler);
CSRF Tokens
In case Yii framework is used along with config plugin, the package is configured automatically to use synchronizer token and masked decorator. You can change that depending on your needs.
Synchronizer CSRF token
Synchronizer CSRF token is a stateful CSRF token that is a unique random string. It is saved in persistent storage available only to the currently logged-in user. The same token is added to a form. When the form is submitted, token that came from the form is compared against the token stored.
SynchronizerCsrfToken
requires implementation of the following interfaces:
CsrfTokenGeneratorInterface
for generating a new CSRF token;CsrfTokenStorageInterface
for persisting a token between requests.
Package provides RandomCsrfTokenGenerator
that generates a random token and
SessionCsrfTokenStorage
that persists a token between requests in a user session.
To learn more about the synchronizer token pattern, check OWASP CSRF cheat sheet.
HMAC based token
HMAC based token is a stateless CSRF token that does not require any storage. The token is a hash from session ID and a timestamp used to prevent replay attacks. The token is added to a form. When the form is submitted, we re-generate the token from the current session ID and a timestamp from the original token. If two hashes match, we check that the timestamp is less than the token lifetime.
HmacCsrfToken
requires implementation of CsrfTokenIdentityGeneratorInterface
for generating an identity.
The package provides SessionCsrfTokenIdentityGenerator
that is using session ID thus making the session a token scope.
Parameters set via the HmacCsrfToken
constructor are:
$secretKey
— shared secret key used to generate the hash;$algorithm
— hash algorithm for message authentication.sha256
,sha384
orsha512
are recommended;$lifetime
— number of seconds that the token is valid for.
To learn more about HMAC based token pattern check OWASP CSRF cheat sheet.
Stub CSRF token
The StubCsrfToken
simply stores and returns a token string. It does not perform any additional validation.
This implementation can be useful when mocking CSRF token behavior during unit testing or when providing
placeholder functionality in temporary solutions.
Masked CSRF token
MaskedCsrfToken
is a decorator for CsrfTokenInterface
that applies masking to a token string.
It makes BREACH attack impossible, so it is safe to use token in HTML to be later passed to
the next request either as a hidden form field or via JavaScript async request.
It is recommended to always use this decorator.
Documentation
If you need help or have a question, the Yii Forum is a good place for that. You may also check out other Yii Community Resources.
License
The Yii CSRF Protection Library is free software. It is released under the terms of the BSD License.
Please see LICENSE
for more information.
Maintained by Yii Software.