YesWiki has Unauthenticated Server-Side Request Forgery via ActivityPub `Signature.keyId`

Summary

The POST /api/forms/{formId}/actor/inbox route - exposed publicly with acl:"public" - accepts an HTTP Signature header whose keyId parameter is a URL. HttpSignatureService::verifySignature() parses the header and immediately makes a server-side HTTP GET to that URL, before any cryptographic verification or URL validation. An unauthenticated remote attacker can therefore make YesWiki issue arbitrary outbound HTTP requests to any host the server can reach - internal services, cloud-metadata endpoints (169.254.169.254), intranet-only admin panels, etc. - and read enough back via timing and error-message oracles to scan ports, enumerate services, and (on a real cloud instance) reach IAM metadata.

The only deployment-side precondition is that ActivityPub be enabled on at least one Bazar form (bn_activitypub_enable = '1').

Details

Affected component

• File: tools/bazar/services/HttpSignatureService.php
• Method: HttpSignatureService::verifySignature(Request $request)
• Sink: line 96
• Route: tools/bazar/controllers/ApiController.php line 125 — @Route("/api/forms/{formId}/actor/inbox", methods={"POST"}, options={"acl":{"public"}})

// tools/bazar/services/HttpSignatureService.php  (v4.6.5 = origin/doryphore-dev HEAD,
// lines 83–100)
public function verifySignature(Request $request) {
    if (!$request->headers->has('Signature')) {
        throw new Exception('No signature');
    }

    $sigConf = parse_ini_string(
        strtr($request->headers->get('Signature'), ["," => "\n"])           // (a) attacker controls every field
    );

    if (!isset($sigConf['keyId'],$sigConf['algorithm'],$sigConf['headers'],$sigConf['signature'])) {
        throw new Exception('Malformed signature');
    }

    $response = $this->httpClient->request('GET', $sigConf['keyId'], [    // (b) SINK — no validation,
        'headers' => [ 'Accept' => 'application/ld+json']                 //     no allowlist, no scheme
    ]);                                                                  //     pinning, no IP filtering
    ...
}

The inbox controller calls verifySignature() before running any cryptography:

// tools/bazar/controllers/ApiController.php  (lines 125–145)
/** @Route("/api/forms/{formId}/actor/inbox", methods={"POST"}, options={"acl":{"public"}}) */
public function postFormActorInbox($formId, Request $request)
{
    $activityPubService   = $this->getService(ActivityPubService::class);
    $httpSignatureService = $this->getService(HttpSignatureService::class);

    $form = $this->getService(BazarListService::class)->getForms(['idtypeannonce' => $formId])[$formId];

    if ($activityPubService->isEnabled($form)) {
        $activity = json_decode($request->getContent(), true);

        $httpSignatureService->verifySignature($request);     // <-- SSRF fires here
        $activityPubService->processActivity($activity, $form);
        return new ApiResponse(null, Response::HTTP_OK, …);
    } else {
        throw new NotFoundHttpException();
    }
}