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| 1 | +<?php |
| 2 | + |
| 3 | +/* |
| 4 | + * This file is part of the Symfony package. |
| 5 | + * |
| 6 | + * (c) Fabien Potencier <fabien@symfony.com> |
| 7 | + * |
| 8 | + * For the full copyright and license information, please view the LICENSE |
| 9 | + * file that was distributed with this source code. |
| 10 | + */ |
| 11 | + |
| 12 | +namespace Symfony\Component\Security\Csrf; |
| 13 | + |
| 14 | +use Psr\Log\LoggerInterface; |
| 15 | +use Symfony\Component\HttpFoundation\Request; |
| 16 | +use Symfony\Component\HttpFoundation\RequestStack; |
| 17 | +use Symfony\Component\HttpFoundation\Response; |
| 18 | +use Symfony\Component\HttpFoundation\Session\Session; |
| 19 | +use Symfony\Component\HttpKernel\Event\ResponseEvent; |
| 20 | + |
| 21 | +/** |
| 22 | + * This CSRF token manager uses a combination of cookie and headers to validate non-persistent tokens. |
| 23 | + * |
| 24 | + * This manager is designed to be stateless and compatible with HTTP-caching. |
| 25 | +
|
| 26 | + * First, we validate the source of the request using the Origin/Referer headers. This relies |
| 27 | + * on the app being able to know its own target origin. Don't miss configuring your reverse proxy to |
| 28 | + * send the X-Forwarded-* / Forwarded headers if you're behind one. |
| 29 | + * |
| 30 | + * Then, we validate the request using a cookie and a custom header. If present, both should contain |
| 31 | + * the same token value. A JavaScript snippet on the client side is responsible performing this |
| 32 | + * double-submission. The token value should be regenerated on every request using a cryptographically |
| 33 | + * secure random generator. |
| 34 | + * |
| 35 | + * If either double-submit or Origin/Referer headers are missing, it typically indicates that |
| 36 | + * JavaScript is disabled on the client side, or that the JavaScript snippet was not properly |
| 37 | + * implemented, or that the Origin/Referer headers were filtered out. |
| 38 | + * |
| 39 | + * Requests lacking both double-submit and origin information are deemed insecure. |
| 40 | + * |
| 41 | + * When a session is found, a behavioral check is added to ensure that the validation method does not |
| 42 | + * downgrade from double-submit to origin checks. This prevents attackers from exploiting potentially |
| 43 | + * less secure validation methods once a more secure method has been confirmed as functional. |
| 44 | + * |
| 45 | + * On HTTPS connections, the cookie is prefixed with "__Host-" to prevent it from being forged on an |
| 46 | + * HTTP channel. On the JS side, the cookie should be set with samesite=strict to strenghen the CSRF |
| 47 | + * protection. The cookie is always cleared on the response to prevent any further use of the token. |
| 48 | + * |
| 49 | + * @author Nicolas Grekas <p@tchwork.com> |
| 50 | + */ |
| 51 | +final class DoubleSubmitCsrfTokenManager implements CsrfTokenManagerInterface |
| 52 | +{ |
| 53 | + public const TOKEN_MIN_LENGTH = 32; |
| 54 | + |
| 55 | + public function __construct( |
| 56 | + private RequestStack $requestStack, |
| 57 | + private ?LoggerInterface $logger = null, |
| 58 | + private string $headerName = 'x-csrf-token', |
| 59 | + ) { |
| 60 | + } |
| 61 | + |
| 62 | + public function getToken(string $tokenId): CsrfToken |
| 63 | + { |
| 64 | + return new CsrfToken($tokenId, $this->headerName); |
| 65 | + } |
| 66 | + |
| 67 | + public function refreshToken(string $tokenId): CsrfToken |
| 68 | + { |
| 69 | + return new CsrfToken($tokenId, $this->headerName); |
| 70 | + } |
| 71 | + |
| 72 | + public function removeToken(string $tokenId): ?string |
| 73 | + { |
| 74 | + return null; |
| 75 | + } |
| 76 | + |
| 77 | + public function isTokenValid(CsrfToken $token): bool |
| 78 | + { |
| 79 | + // This token is not for us |
| 80 | + if ($token->getValue() !== $this->headerName) { |
| 81 | + $this->logger?->debug('CSRF validation failed: Unknown CSRF token.'); |
| 82 | + |
| 83 | + return false; |
| 84 | + } |
| 85 | + |
| 86 | + if (!$request = $this->requestStack->getCurrentRequest()) { |
| 87 | + $this->logger?->debug('CSRF validation failed: No request found.'); |
| 88 | + |
| 89 | + return false; |
| 90 | + } |
| 91 | + |
| 92 | + if (false === $isValidOrigin = $this->isValidOrigin($request)) { |
| 93 | + $this->logger?->debug('CSRF validation failed: Origin doesn\'t match.'); |
| 94 | + |
| 95 | + return false; |
| 96 | + } |
| 97 | + |
| 98 | + if ($this->isValidDoubleSubmit($request)) { |
| 99 | + // Mark the request as validated using double-submit info |
| 100 | + $request->attributes->set($this->headerName, 'double-submit'); |
| 101 | + $this->logger?->debug('CSRF validation accepted using double-submit info.'); |
| 102 | + |
| 103 | + return true; |
| 104 | + } |
| 105 | + |
| 106 | + // Opportunistically lookup at the session for a previous CSRF validation strategy |
| 107 | + $session = $request->hasPreviousSession() ? $request->getSession() : null; |
| 108 | + $usageIndexValue = $session instanceof Session ? $usageIndexReference = &$session->getUsageIndex() : 0; |
| 109 | + $usageIndexReference = \PHP_INT_MIN; |
| 110 | + $csrfProtection = $session?->get($this->headerName); |
| 111 | + $usageIndexReference = $usageIndexValue; |
| 112 | + |
| 113 | + // If a previous request was validated using double-submit info, stick to it |
| 114 | + if ('double-submit' === $csrfProtection) { |
| 115 | + $this->logger?->debug('CSRF validation failed: double-submit info was used in a previous request but didn\'t pass this time.'); |
| 116 | + |
| 117 | + return false; |
| 118 | + } |
| 119 | + |
| 120 | + // If a previous request was validated using origin info, stick to it |
| 121 | + if ('origin' === $csrfProtection && null === $isValidOrigin) { |
| 122 | + $this->logger?->debug('CSRF validation failed: origin info was used in a previous request but didn\'t pass this time.'); |
| 123 | + |
| 124 | + return false; |
| 125 | + } |
| 126 | + |
| 127 | + if (true === $isValidOrigin) { |
| 128 | + // Mark the request as validated using origin info |
| 129 | + $request->attributes->set($this->headerName, 'origin'); |
| 130 | + $this->logger?->debug('CSRF validation accepted using origin info.'); |
| 131 | + |
| 132 | + return true; |
| 133 | + } |
| 134 | + |
| 135 | + $this->logger?->debug('CSRF validation failed: double-submit and origin info not found.'); |
| 136 | + |
| 137 | + return false; |
| 138 | + } |
| 139 | + |
| 140 | + public function clearCookie(Request $request, Response $response): void |
| 141 | + { |
| 142 | + $cookieName = ($request->isSecure() ? '__Host-' : '').$this->headerName; |
| 143 | + |
| 144 | + if ($request->cookies->has($cookieName)) { |
| 145 | + $response->headers->clearCookie($cookieName, '/', null, $request->isSecure(), false, 'strict'); |
| 146 | + } |
| 147 | + } |
| 148 | + |
| 149 | + public function persistStrategy(Request $request): void |
| 150 | + { |
| 151 | + if ($request->hasSession(true) && $request->attributes->has($this->headerName)) { |
| 152 | + $request->getSession()->set($this->headerName, $request->attributes->get($this->headerName)); |
| 153 | + } |
| 154 | + } |
| 155 | + |
| 156 | + public function onKernelResponse(ResponseEvent $event): void |
| 157 | + { |
| 158 | + if (!$event->isMainRequest()) { |
| 159 | + return; |
| 160 | + } |
| 161 | + |
| 162 | + $this->clearCookie($event->getRequest(), $event->getResponse()); |
| 163 | + $this->persistStrategy($event->getRequest()); |
| 164 | + } |
| 165 | + |
| 166 | + /** |
| 167 | + * @return bool|null Whether the origin is valid, null if missing |
| 168 | + */ |
| 169 | + private function isValidOrigin(Request $request): ?bool |
| 170 | + { |
| 171 | + $source = $request->headers->get('Origin') ?? $request->headers->get('Referer') ?? 'null'; |
| 172 | + |
| 173 | + return 'null' === $source ? null : str_starts_with($source.'/', $request->getScheme().'://'.$request->getHttpHost().'/'); |
| 174 | + } |
| 175 | + |
| 176 | + private function isValidDoubleSubmit(Request $request): bool |
| 177 | + { |
| 178 | + $token = $request->headers->get($this->headerName); |
| 179 | + |
| 180 | + if (!\is_string($token) || \strlen($token) < self::TOKEN_MIN_LENGTH) { |
| 181 | + return false; |
| 182 | + } |
| 183 | + |
| 184 | + $cookieName = ($request->isSecure() ? '__Host-' : '').$this->headerName; |
| 185 | + |
| 186 | + return $request->cookies->get($cookieName) === $token; |
| 187 | + } |
| 188 | +} |
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