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<!DOCTYPE HTML>
<html>
<!--
Tor bug
https://trac.torproject.org/projects/tor/ticket/1517
-->
<head>
<meta charset="utf-8">
<title>Test for Tor Bug 1517 and Mozilla Bug 1424341</title>
<script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
<script type="application/javascript" src="/tests/SimpleTest/SpawnTask.js"></script>
<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
</head>
<body>
<a target="_blank" href="https://trac.torproject.org/projects/tor/ticket/1517">Tor Bug 1517</a>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1424341">Mozilla Bug 1424341</a>
<!-- Canvas for testing 'currentTime' -->
<canvas id="test-canvas" width="100" height="100"></canvas>
<!-- The main testing script -->
<script type="application/javascript">
SimpleTest.requestFlakyTimeout("testing JS time-based fingerprinting");
// Prepare for test of AudioContext.currentTime
let audioContext = new AudioContext();
// Prepare for test of CanvasStream.currentTime
let canvas = document.getElementById("test-canvas");
let context = canvas.getContext("2d");
context.fillText("test", 20, 20);
let canvasStream = canvas.captureStream(25);
// Known ways to generate time stamps, in milliseconds
const timeStampCodes = [
"performance.now()",
"new Date().getTime()",
"new Event(\"\").timeStamp",
"new File([], \"\").lastModified",
"new File([], \"\").lastModifiedDate.getTime()",
];
// These are measured in seconds, so we need to scale them up
var timeStampCodesDOM = timeStampCodes.concat([
"audioContext.currentTime * 1000",
"canvasStream.currentTime * 1000",
]);
let isRounded = (x) => {
expectedPrecision = 2;
let rounded = (Math.floor(x / expectedPrecision) * expectedPrecision);
// First we do the perfectly normal check that should work just fine
if (rounded === x || x === 0)
return true;
// When we're diving by non-whole numbers, we may not get perfect
// multiplication/division because of floating points.
// When dealing with ms since epoch, a double's precision is on the order
// of 1/5 of a microsecond, so we use a value a little higher than that as
// our epsilon.
// To be clear, this error is introduced in our re-calculation of 'rounded'
// above in JavaScript.
if (Math.abs(rounded - x + expectedPrecision) < .0005) {
return true;
} else if (Math.abs(rounded - x) < .0005) {
return true;
}
// Then we handle the case where you're sub-millisecond and the timer is not
// We check that the timer is not sub-millisecond by assuming it is not if it
// returns an even number of milliseconds
if (expectedPrecision < 1 && Math.round(x) == x) {
if (Math.round(rounded) == x) {
return true;
}
}
ok(false, "Looming Test Failure, Additional Debugging Info: Expected Precision: " + expectedPrecision + " Measured Value: " + x +
" Rounded Vaue: " + rounded + " Fuzzy1: " + Math.abs(rounded - x + expectedPrecision) +
" Fuzzy 2: " + Math.abs(rounded - x));
return false;
};
// ================================================================================================
// ================================================================================================
function* checkWorker(worker) {
// The child worker will send the results back.
let checkWorkerTimeStamps = () => new Promise(function(resolve) {
let onMessage = function(event) {
worker.removeEventListener("message", onMessage);
let timeStamps = event.data;
for (let i = 0; i < timeStampCodes.length; i++) {
let timeStamp = timeStamps[i];
ok(isRounded(timeStamp),
"'" + timeStampCodes[i] +
"' should be rounded to nearest 2 ms in workers; saw " +
timeStamp);
}
resolve();
};
worker.addEventListener("message", onMessage);
});
// Send the codes to its child worker.
worker.postMessage(timeStampCodes);
// First, check the child's results.
yield checkWorkerTimeStamps();
// Then, check the grandchild's results.
yield checkWorkerTimeStamps();
worker.terminate();
}
add_task(function*() {
let worker = new Worker("worker_child.js");
// Allow ~550 ms to elapse, so we can get non-zero
// time values for all elements.
yield new Promise(resolve => window.setTimeout(resolve, 550));
yield checkWorker(worker);
});
// ================================================================================================
// ================================================================================================
add_task(function*() {
// Loop through each timeStampCode, evaluate it,
// and check if it is rounded
for (let timeStampCode of timeStampCodesDOM) {
let timeStamp = eval(timeStampCode);
ok(isRounded(timeStamp),
"'" + timeStampCode + "' should be rounded to nearest 2ms" +
" saw " + timeStamp);
}
});
</script>
</body>
</html>
|
