gecko-dev/dom/u2f/tests/test_u2f_replaceable.html

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<head>
  <meta charset="utf-8">
  <title>Make sure that pages can define a variable named "u2f" and have it work</title>
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" href="/tests/SimpleTest/test.css"/>
  <script>
    var u2f = 5;
    is(u2f, 5, "Should have allowed reassignment");
    is(Object.getOwnPropertyDescriptor(window, "u2f").value, 5,
       "Should be a value property");
  </script>
</head>
<body>
<p id="display"></p>
<div id="content" style="display: none"></div>
<pre id="test"></pre>
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</html>
Bug 1551282 and bug 1553436. Allow pages to override window.u2f but not the "sign" and "register" properties on the U2F object. r=jcj,smaug There are two related problems this patch is trying to address. The first, and simpler, one is bug 1553436: there are websites that use existing variables and functions named "u2f" and adding a non-replaceable readonly property with that name on Window breaks them. The fix for this is straightforward: mark the property [Replaceable]. The second problem, covered by bug 1551282, involves sites that use the Google U2F polyfill. The relevant parts of that polyfill look like this: 'use strict'; var u2f = u2f \|\| {}; u2f.register = some_function_that_only_works_right_in_Chrome; u2f.sign = some_function_that_only_works_right_in_Chrome; The failure mode for that code before this fix is that the assignment to "u2f" throws because it's a readonly property and we're in strict mode, so any code the page concatenates in the same file after the polyfill does not get run. That's what bug 1551282 is about. The [Replaceable] annotation fixes that issue, because now the polyfill gets the value of window.u2f and then redefines the property (via the [Replaceable] setter) to be a value property with that value. So far, so good. But then we need to prevent the sets of u2f.register and u2f.sign from taking effect, because if they are allowed to happen, the actual sign/register functionality on the page will not work in Firefox. We can't just make the properties readonly, because then the sets will throw due to being in strict mode, and we still have bug 1551282. The proposed fix is to make these accessor properties with a no-op setter, which is exactly what [LenientSetter] gives us. The rest of the patch is just setting up infrastructure for generating the normal bits we would generate if "sign" and "register" were methods and using that to create the JSFunctions at the point when the getter is called. The JSFunctions then get cached on the u2f instance object. Differential Revision: https://phabricator.services.mozilla.com/D32357 --HG-- extra : moz-landing-system : lando 2019-05-24 23:40:59 +03:00			`<!DOCTYPE HTML>`
			`<html>`
			`<head>`
			`<meta charset="utf-8">`
			`<title>Make sure that pages can define a variable named "u2f" and have it work</title>`
			`<script src="/tests/SimpleTest/SimpleTest.js"></script>`
			`<link rel="stylesheet" href="/tests/SimpleTest/test.css"/>`
			`<script>`
			`var u2f = 5;`
			`is(u2f, 5, "Should have allowed reassignment");`
			`is(Object.getOwnPropertyDescriptor(window, "u2f").value, 5,`
			`"Should be a value property");`
			`</script>`
			`</head>`
			`<body>`
			`<p id="display"></p>`
			`<div id="content" style="display: none"></div>`
			`<pre id="test"></pre>`
			`</body>`
			`</html>`