iframe 如何删除自己的沙盒？

Question

我正在使用同源 iframe 加载外部小部件（tlk.io 通过跨源脚本加载）。我正在尝试为 iframe/widget 提供尽可能低的权限，以将其与我的应用程序隔离。

MDN 给出以下警告：

Notes about sandboxing:

When the embedded document has the same origin as the embedding page, it is strongly discouraged to use both allow-scripts and allow-same-origin, as that lets the embedded document remove the sandbox attribute — making it no more secure than not using the sandbox attribute at all.

Firefox devtools 向我显示此警告：

An iframe which has both allow-scripts and allow-same-origin for its sandbox attribute can remove its sandboxing.

我的问题是：在这种情况下 (sandbox="allow-same-origin allow-scripts") iframe 如何删除其沙箱？什么 js 代码会执行此操作？

在 iframe 中，我尝试查看 window.opener，但它是空的。 window.parent 不是指父级（编辑：不正确，我错误地使用了 devtools）。我无法从 iframe 本身找到对 «iframe» 的引用...

Answer 1

您将自己暴露给 DOM iframe 操纵。

有了这两个沙盒属性，没有什么可以阻止嵌入式框架用新的 iframe 替换自己。具有任何权限的 iframe 启用。

index.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>Bad Sandboxing</title>
  </head>
  <body>
    <p>This is here to space out iframe</p>
    <iframe
      src="malicious_child.html"
      sandbox="allow-same-origin allow-scripts"
      id="mountPoint"
    >
    </iframe>
    <p>This is here to space out iframe</p>
  </body>
</html>

malicious_child.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Child</title>
</head>
<body>
<script type="text/javascript">
    document.body.innerText = "Loaded into a frame.";

    let parent = window.parent;
    let oldIframe = parent.document.getElementById("mountPoint");
    if (oldIframe != null) {
        // Build a new iframe to replace the old one.
        let newIframe = parent.document.createElement("iframe");
        newIframe.setAttribute("src", "malicious_child.html");
        newIframe.setAttribute("id", "maliciousFrame");
        // Replace Old iFrame
        oldIframe.replaceWith(newIframe);
    } else {
        // When new frame is mounted you will see this alert
        alert(
            "This should not happen since the original iframe did not have 'allow-modals'."
        );
    }
</script>
</body>
</html>

这是一个 Code Sanbox 的设置。

iframe 如何删除自己的沙盒？

How can an iframe remove its own sandboxing?

javascript

browser

iframe

dom