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Fix BackURL redirect with strict or lax session cookie security. #55

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merged 1 commit into from
Jan 24, 2024
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Fix BackURL redirect with strict or lax session cookie security. #55

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10 changes: 10 additions & 0 deletions src/Control/SAMLController.php
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Original file line number Diff line number Diff line change
Expand Up @@ -262,6 +262,16 @@ protected function getRedirect()
return $this->redirect($this->getRequest()->getSession()->get('BackURL'));
}

// In SAMLHelper, we use RelayState to convey BackURL because in a HTTP POST flow
// with lax or strict cookie security the session will not be there for us. RelayState
// will be reflected back in the acs POST request.
// Note if only assertion is signed, RelayState cannot be trusted. Prevent open relay
// as in https://github.com/SAML-Toolkits/php-saml#avoiding-open-redirect-attacks
$relayState = $this->owner->getRequest()->postVar('RelayState');
if ($relayState && Director::is_site_url($relayState)) {
return $this->redirect($relayState);
}

// Spoofing attack, redirect to homepage instead of spoofing url
if ($back && !Director::is_site_url($back)) {
return $this->redirect(Director::absoluteBaseURL());
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3 changes: 2 additions & 1 deletion src/Helpers/SAMLHelper.php
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Expand Up @@ -75,7 +75,8 @@ public function redirect(RequestHandler $requestHandler = null, HTTPRequest $req
$additionalGetQueryParams = $this->getAdditionalGETQueryParameters();

try {
$auth->login(Director::absoluteBaseURL() . 'saml/', $additionalGetQueryParams);
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@mateusz mateusz Jan 10, 2024 •
edited
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By the way, this usage of login's first parameter is wrong, it results in a URL like https://mysite.comsaml/, i.e. it's missing the slash. The bug didn't manifest as an issue, because RelayState isn't used anyway.

// Use RelayState to convey BackURL (will be handled in SAMLController).
$auth->login($backURL, $additionalGetQueryParams);
} catch (Exception $e) {
/** @var LoggerInterface $logger */
$logger = Injector::inst()->get(LoggerInterface::class);
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