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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
const emptyPage =
getRootDirectory(gTestPath).replace(
"chrome://mochitests/content",
"https://example.com"
) + "empty.html";
/**
* Bug 1816189 - Testing canvas randomization on canvas data extraction in
* workers.
*
* In the test, we create offscreen canvas in workers and test if the extracted
* canvas data is altered because of the canvas randomization.
*/
/**
*
* Spawns a worker in the given browser and sends a callback function to it.
* The result of the callback function is returned as a Promise.
*
* @param {object} browser - The browser context to spawn the worker in.
* @param {Function} fn - The callback function to send to the worker.
* @returns {Promise} A Promise that resolves to the result of the callback function.
*/
function runFunctionInWorker(browser, fn) {
return SpecialPowers.spawn(browser, [fn.toString()], async callback => {
// Create a worker.
let worker = new content.Worker("worker.js");
// Send the callback to the worker.
return new content.Promise(resolve => {
worker.onmessage = e => {
resolve(e.data.result);
};
worker.postMessage({
callback,
});
});
});
}
var TEST_CASES = [
{
name: "CanvasRenderingContext2D.getImageData() with a offscreen canvas",
extractCanvasData: async _ => {
let offscreenCanvas = new OffscreenCanvas(100, 100);
const context = offscreenCanvas.getContext("2d");
// Draw a red rectangle
context.fillStyle = "red";
context.fillRect(0, 0, 100, 100);
const imageData = context.getImageData(0, 0, 100, 100);
const imageDataSecond = context.getImageData(0, 0, 100, 100);
return [imageData.data, imageDataSecond.data];
},
isDataRandomized(data1, data2, isCompareOriginal) {
let diffCnt = compareUint8Arrays(data1, data2);
info(`There are ${diffCnt} bits are different.`);
// The Canvas randomization adds at most 512 bits noise to the image data.
// We compare the image data arrays to see if they are different and the
// difference is within the range.
// If we are compare two randomized arrays, the difference can be doubled.
let expected = isCompareOriginal
? NUM_RANDOMIZED_CANVAS_BITS
: NUM_RANDOMIZED_CANVAS_BITS * 2;
// The number of difference bits should never bigger than the expected
// number. It could be zero if the randomization is disabled.
ok(diffCnt <= expected, "The number of noise bits is expected.");
return diffCnt <= expected && diffCnt > 0;
},
},
{
name: "OffscreenCanvas.convertToBlob() with a 2d context",
extractCanvasData: async _ => {
let offscreenCanvas = new OffscreenCanvas(100, 100);
const context = offscreenCanvas.getContext("2d");
// Draw a red rectangle
context.fillStyle = "red";
context.fillRect(0, 0, 100, 100);
let blob = await offscreenCanvas.convertToBlob();
let data = await new Promise(resolve => {
let fileReader = new FileReader();
fileReader.onload = () => {
resolve(fileReader.result);
};
fileReader.readAsArrayBuffer(blob);
});
let blobSecond = await offscreenCanvas.convertToBlob();
let dataSecond = await new Promise(resolve => {
let fileReader = new FileReader();
fileReader.onload = () => {
resolve(fileReader.result);
};
fileReader.readAsArrayBuffer(blobSecond);
});
return [data, dataSecond];
},
isDataRandomized(data1, data2) {
return compareArrayBuffer(data1, data2);
},
},
{
name: "OffscreenCanvas.convertToBlob() with a webgl context",
extractCanvasData: async _ => {
let offscreenCanvas = new OffscreenCanvas(100, 100);
const context = offscreenCanvas.getContext("webgl");
// Draw a blue rectangle
context.enable(context.SCISSOR_TEST);
context.scissor(0, 150, 150, 150);
context.clearColor(1, 0, 0, 1);
context.clear(context.COLOR_BUFFER_BIT);
context.scissor(150, 150, 300, 150);
context.clearColor(0, 1, 0, 1);
context.clear(context.COLOR_BUFFER_BIT);
context.scissor(0, 0, 150, 150);
context.clearColor(0, 0, 1, 1);
context.clear(context.COLOR_BUFFER_BIT);
let blob = await offscreenCanvas.convertToBlob();
let data = await new Promise(resolve => {
let fileReader = new FileReader();
fileReader.onload = () => {
resolve(fileReader.result);
};
fileReader.readAsArrayBuffer(blob);
});
let blobSecond = await offscreenCanvas.convertToBlob();
let dataSecond = await new Promise(resolve => {
let fileReader = new FileReader();
fileReader.onload = () => {
resolve(fileReader.result);
};
fileReader.readAsArrayBuffer(blobSecond);
});
return [data, dataSecond];
},
isDataRandomized(data1, data2) {
return compareArrayBuffer(data1, data2);
},
},
{
name: "OffscreenCanvas.convertToBlob() with a bitmaprenderer context",
extractCanvasData: async _ => {
let offscreenCanvas = new OffscreenCanvas(100, 100);
const context = offscreenCanvas.getContext("2d");
// Draw a red rectangle
context.fillStyle = "red";
context.fillRect(0, 0, 100, 100);
const bitmapCanvas = new OffscreenCanvas(100, 100);
let bitmap = await createImageBitmap(offscreenCanvas);
const bitmapContext = bitmapCanvas.getContext("bitmaprenderer");
bitmapContext.transferFromImageBitmap(bitmap);
let blob = await bitmapCanvas.convertToBlob();
let data = await new Promise(resolve => {
let fileReader = new FileReader();
fileReader.onload = () => {
resolve(fileReader.result);
};
fileReader.readAsArrayBuffer(blob);
});
let blobSecond = await bitmapCanvas.convertToBlob();
let dataSecond = await new Promise(resolve => {
let fileReader = new FileReader();
fileReader.onload = () => {
resolve(fileReader.result);
};
fileReader.readAsArrayBuffer(blobSecond);
});
return [data, dataSecond];
},
isDataRandomized(data1, data2) {
return compareArrayBuffer(data1, data2);
},
},
];
async function runTest(enabled) {
// Enable/Disable CanvasRandomization by the RFP target overrides.
let RFPOverrides = enabled ? "+CanvasRandomization" : "-CanvasRandomization";
await SpecialPowers.pushPrefEnv({
set: [
["privacy.resistFingerprinting.randomization.enabled", true],
["privacy.fingerprintingProtection", true],
["privacy.fingerprintingProtection.pbmode", true],
["privacy.fingerprintingProtection.overrides", RFPOverrides],
["privacy.resistFingerprinting", false],
],
});
// Open a private window.
let privateWindow = await BrowserTestUtils.openNewBrowserWindow({
private: true,
});
// Open tabs in the normal and private window.
const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, emptyPage);
const privateTab = await BrowserTestUtils.openNewForegroundTab(
privateWindow.gBrowser,
emptyPage
);
for (let test of TEST_CASES) {
info(`Testing ${test.name} in the worker`);
let data = await await runFunctionInWorker(
tab.linkedBrowser,
test.extractCanvasData
);
let result = test.isDataRandomized(data[0], test.originalData);
is(
result,
enabled,
`The image data is ${enabled ? "randomized" : "the same"}.`
);
ok(
!test.isDataRandomized(data[0], data[1]),
"The data of first and second access should be the same."
);
let privateData = await await runFunctionInWorker(
privateTab.linkedBrowser,
test.extractCanvasData
);
// Check if we add noise to canvas data in private windows.
result = test.isDataRandomized(privateData[0], test.originalData, true);
is(
result,
enabled,
`The private image data is ${enabled ? "randomized" : "the same"}.`
);
ok(
!test.isDataRandomized(privateData[0], privateData[1]),
"The data of first and second access should be the same."
);
// Make sure the noises are different between normal window and private
// windows.
result = test.isDataRandomized(privateData[0], data[0]);
is(
result,
enabled,
`The image data between the normal window and the private window are ${
enabled ? "different" : "the same"
}.`
);
}
BrowserTestUtils.removeTab(tab);
BrowserTestUtils.removeTab(privateTab);
await BrowserTestUtils.closeWindow(privateWindow);
}
add_setup(async function () {
// Disable the fingerprinting randomization.
await SpecialPowers.pushPrefEnv({
set: [
["privacy.resistFingerprinting.randomization.enabled", false],
["privacy.fingerprintingProtection", false],
["privacy.fingerprintingProtection.pbmode", false],
["privacy.resistFingerprinting", false],
],
});
// Open a tab for extracting the canvas data in the worker.
const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, emptyPage);
// Extract the original canvas data without random noise.
for (let test of TEST_CASES) {
let data = await runFunctionInWorker(
tab.linkedBrowser,
test.extractCanvasData
);
test.originalData = data[0];
}
BrowserTestUtils.removeTab(tab);
});
add_task(async function run_tests_with_randomization_enabled() {
await runTest(true);
});
add_task(async function run_tests_with_randomization_disabled() {
await runTest(false);
});
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