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[WIP] Mitigate "mix up" attack #54

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[WIP] Mitigate "mix up" attack #54

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7de2564
Add issuer `iss` as HTTP Query Parameter to redirect URL in OAuth res…
Potherca Nov 24, 2025
c74618f
[@CHECKME] Add issuer `iss` as HTTP Query Parameter to redirect URL i…
Potherca Nov 24, 2025
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49 changes: 46 additions & 3 deletions src/Server.php
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Original file line number Diff line number Diff line change
Expand Up @@ -40,10 +40,12 @@ final public function respondToAccessTokenRequest(Request $request) : Response
$response = $this->response;

try {
return $authorizationServer->respondToAccessTokenRequest($request, $response);
$httpResponse = $authorizationServer->respondToAccessTokenRequest($request, $response);
} catch (OAuthServerException $serverException) {
return $this->createOauthServerExceptionResponse($response, $serverException);
$httpResponse = $this->createOauthServerExceptionResponse($response, $serverException);
}

return $this->addIssuerToRedirectUrl($httpResponse);
}

/**
Expand Down Expand Up @@ -71,7 +73,11 @@ final public function respondToAuthorizationRequest(
// Validate the HTTP request and return an AuthorizationRequest object.
$authRequest = $authorizationServer->validateAuthorizationRequest($request);
} catch (OAuthServerException $serverException) {
return $this->createOauthServerExceptionResponse($response, $serverException);
$httpResponse = $this->createOauthServerExceptionResponse($response, $serverException);
// @CHECKME: Is this a 302 redirect? If so, a `iss` query param should be added to the redirect URL in the Location header
$httpResponse = $this->addIssuerToRedirectUrl($httpResponse);

return $httpResponse;
}

if ($user instanceof UserEntityInterface) {
Expand All @@ -95,6 +101,7 @@ final public function respondToAuthorizationRequest(

// Return the HTTP redirect response
$response = $authorizationServer->completeAuthorizationRequest($authRequest, $response);
$response = $this->addIssuerToRedirectUrl($response);
} else {
// @CHECKME: 404 or throw Exception?
$response = $response->withStatus(404);
Expand Down Expand Up @@ -150,4 +157,40 @@ private function createJsonResponse(Response $response, $json = null) : Response

return $response->withHeader('content-type', 'application/json; charset=UTF-8');
}

/**
* Add `iss` query param to the Location header, if present and not already set.
*
* @see https://www.ietf.org/rfc/rfc9207
*/
private function addIssuerToRedirectUrl(Response $response): Response
{
if ($response->hasHeader('Location')) {
$location = $response->getHeaderLine('Location');

$urlParts = parse_url($location);
$queryParams = [];
if (isset($urlParts['query'])) {
parse_str($urlParts['query'], $queryParams);
}

if ( ! array_key_exists('iss', $queryParams)) {
$issuer = $this->config->getServer()->get(OidcMeta::ISSUER);
$queryParams['iss'] = $issuer;

$urlParts['query'] = http_build_query($queryParams);

$location = vsprintf("%s%s%s?%s", [
isset($urlParts['scheme']) ? $urlParts['scheme'] . '://' : '',
$urlParts['host'] ?? '',
$urlParts['path'] ?? '',
$urlParts['query']
]);

$response = $response->withHeader('Location', $location);
}
}

return $response;
}
}