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[Security/Csrf] Trust "Referer" at the same level as "Origin" #59269

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Merged
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Dec 22, 2024
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[Security/Csrf] Trust "Referer" at the same level as "Origin" #59269

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16 changes: 14 additions & 2 deletions src/Symfony/Component/Security/Csrf/SameOriginCsrfTokenManager.php
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Original file line number Diff line number Diff line change
Expand Up @@ -227,9 +227,21 @@ public function onKernelResponse(ResponseEvent $event): void
*/
private function isValidOrigin(Request $request): ?bool
{
$source = $request->headers->get('Origin') ?? $request->headers->get('Referer') ?? 'null';
$target = $request->getSchemeAndHttpHost().'/';
$source = 'null';
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why using a string containing null here instead of an actual null value ?

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The "null" string is a possible value of the Origin header. This saves checking for one more case.
See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Origin#description

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@GromNaN GromNaN Dec 20, 2024 •
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Hum, here you assume that we cannot receive Origin: null and Referer: http://not-the-same-origin.com/. From the doc it seems unlikely to expose the Referer with "privacy sensitive" origin.

Edit: the function will return false while previously that case returned null. Which is safer for this limit case.

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Yep, that's what we should do, isn't it?

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Yes;


return 'null' === $source ? null : str_starts_with($source.'/', $request->getSchemeAndHttpHost().'/');
foreach (['Origin', 'Referer'] as $header) {
if (!$request->headers->has($header)) {
continue;
}
$source = $request->headers->get($header);

if (str_starts_with($source.'/', $target)) {
return true;
}
}

return 'null' === $source ? null : false;
}

/**
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14 changes: 14 additions & 0 deletions src/Symfony/Component/Security/Csrf/Tests/SameOriginCsrfTokenManagerTest.php
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Expand Up @@ -100,6 +100,20 @@ public function testValidOrigin()
$this->assertSame(1 << 8, $request->attributes->get('csrf-token'));
}

public function testValidRefererInvalidOrigin()
{
$request = new Request();
$request->headers->set('Origin', 'http://localhost:1234');
$request->headers->set('Referer', $request->getSchemeAndHttpHost());
$this->requestStack->push($request);

$token = new CsrfToken('test_token', str_repeat('a', 24));

$this->logger->expects($this->once())->method('debug')->with('CSRF validation accepted using origin info.');
$this->assertTrue($this->csrfTokenManager->isTokenValid($token));
$this->assertSame(1 << 8, $request->attributes->get('csrf-token'));
}

public function testValidOriginAfterDoubleSubmit()
{
$session = $this->createMock(Session::class);
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