Blocking fingerprinting in browser settings can cause icons not to render or map not to render #8377

kbauhausness · 2019-06-21T19:06:29Z

The browser Brave's "device recognition"/"fingerprinting" blocking blocks anything that attempts to read data out of a canvas to prevent it from being used for browser fingerprinting (see https://browserleaks.com/canvas). This defaults to "block 3rd-party fingerprinting", which can apply when a map is embedded in an external website.

More on Google/Chrome's future plans for anti-fingerprinting functionality here.

mapbox-gl-js version: 1.0.0, any

browser: able to reproduce in Brave, Chrome given anti-fingerprinting settings enabled

Steps to Trigger Behavior

In Brave:

change the setting (under Settings > Shields) to "Block all fingerprinting",
you can reproduce with this simple page:

<!DOCTYPE html>
<html>
    <body>
    <canvas id="canvas" width="100" height="100"></canvas>
    <div id="output"></div>
    <script type="text/javascript">
        var canvas = document.getElementById("canvas");
        var ctx = canvas.getContext("2d");
        ctx.fillStyle = "#FF0000";
        ctx.fillRect(0, 0, 100, 100);
        var imageData = ctx.getImageData(0, 0, 100, 100);
        document.getElementById("output").innerHTML = "getImageData width: " + imageData.width + " height: " + imageData.height;
    </script>
</html>

You'll see that in a normal browser, the expected width and height of 100x100 are seen, but with that setting in Brave, it returns a 0x0 image.
Similarly, setting Brave to "block all fingerprinting" and loading this mapbox map, the error RangeError('out of range destination coordinates for image copy') is thrown and no map is rendered: https://api.mapbox.com/styles/v1/mapbox/streets-v9.html?title=true&access_token=ACCESS_TOKEN#1.1/0/0 .

In Chrome:

install the Chrome extension CanvasFingerprintBlock
load the map https://api.mapbox.com/styles/v1/mapbox/streets-v9.html?title=true&access_token=ACCESS_TOKEN#1.1/0/0
Notice that the map loads, but icons are missing and the following message is shown in the CanvasFingerprintBlock extension:

Link to Demonstration

https://jsbin.com/

Expected Behavior

The map is still rendered / icons are still rendered even when anti-fingerprinting settings are enabled.

Actual Behavior

In Brave with anti-fingerprinting, the map is not rendered. In Chrome with anti-fingerprinting, the icons from the spritesheet are not rendered.

The text was updated successfully, but these errors were encountered:

peterqliu · 2019-06-24T23:03:04Z

Flagging the current getImageData implementation:

mapbox-gl-js/src/util/browser.js

Lines 37 to 47 in 27ac83a

    
           getImageData(img: CanvasImageSource): ImageData { 
        
               const canvas = window.document.createElement('canvas'); 
        
               const context = canvas.getContext('2d'); 
        
               if (!context) { 
        
                   throw new Error('failed to create canvas 2d context'); 
        
               } 
        
               canvas.width = img.width; 
        
               canvas.height = img.height; 
        
               context.drawImage(img, 0, 0, img.width, img.height); 
        
               return context.getImageData(0, 0, img.width, img.height); 
        
           },

May be worth exploring get-pixels's canvas-less, node implementation https://github.com/scijs/get-pixels/blob/master/node-pixels.js

1ec5 · 2019-06-24T23:10:39Z

Is TinySDF also affected? TinySDF is used for rendering ideographic characters using client-side fonts.

https://github.com/mapbox/tiny-sdf/blob/34a06b10e99555a156e4d147ab28fd11da4bd4e0/index.js#L40

ahk · 2019-06-24T23:25:09Z

Is TinySDF also affected?

It looks like it is. It's using the same function of canvas API.

ryanhamley · 2019-06-24T23:38:17Z

It definitely blocks local ideograph generation as well. I just tested it out to be sure.

ryanhamley · 2019-06-27T21:40:32Z

It looks like the ImageData interface may be what we need to avoid this.

Creates an ImageData object from a given Uint8ClampedArray and the size of the image it contains. If no array is given, it creates an image of a black rectangle. Note that this is the most common way to create such an object in workers as createImageData() is not available there.

EDIT: Ooops, misread the description. This won't work.

cc @asheemmamoowala @mourner Is this what you had in mind?

mourner · 2019-06-27T22:07:07Z

@ryanhamley no, that's the whole point of TinySDF — we need to use getImageData to get the data drawn on the canvas with the Canvas text API. It won't work without it. createImageData is only useful for the reverse — generating an array of pixel data that you want drawn on a Canvas.

asheemmamoowala · 2019-06-27T23:06:21Z

According to the docs, createImageBitmap can be used to get the image data out of a <canvas> or HTMLCanvasElement as well. Shouldn't that be able to replace a canvasElem.getImageData() call?

ryanhamley · 2019-06-28T22:00:20Z

I believe after a bit of research that canvas fingerprinting is what's blocking sprites and glyphs. But there's also WebGL fingerprinting and blocking this causes the entire map to render as a white screen. That's why we see a difference between Chrome using the CanvasFingerprintBlock plugin and Brave. When you disable all fingerprinting in Brave, it blocks both Canvas and WebGL fingerprinting.

Under Technical Details, Brave says:

Because most browser fingerprinting defense requires disabling web features that are required for many sites to work properly, it is implemented as off-by-default for now (can be turned on in about:preferences globally, or on a per-site basis in the Bravery panel). We will consider turning it on-by-default when we have fingerprinting detection heuristics with a sufficiently-low false positive rate.

You can create an ImageBitmap from a canvas element, but the ImageBitmap instance only has height and width properties; it does not expose the image data the way that canvas.getImageData does (which returns an instance of ImageData).

mourner · 2019-07-01T10:29:29Z

@ryanhamley does this mean that there are no next actions for us here — we just wait for browsers to get better at not blocking essential features when turning on fingerprinting protection, and rely on users not turning it fully on until that time — right?

ryanhamley · 2019-07-01T17:29:09Z

That's what my research is pointing towards @mourner I want to do a bit more testing today before I close this though.

ryanhamley · 2019-07-19T00:13:36Z

I did some fairly extensive research on this issue and there's not really anything we can do about it. Fingerprinting blockers disable functionality that GL JS relies on and there are no alternative ways of making the library work. This is a won't fix issue.

andrewharvey · 2020-01-16T23:16:41Z

In light of the unable to fix here I've opened mapbox/mapbox-gl-supported#25 in case mapbox-gl-supported can detect the potential issue and return false.

peterqliu added the needs investigation 🔍 Issues that require further research (e.g. it's not clear whether it's GL JS or something else) label Jun 24, 2019

asheemmamoowala assigned ryanhamley Jun 28, 2019

ryanhamley closed this as completed Jul 19, 2019

ryanhamley removed the needs investigation 🔍 Issues that require further research (e.g. it's not clear whether it's GL JS or something else) label Jul 19, 2019

ryanhamley mentioned this issue Jan 15, 2020

map within iframe with external domain broken on brave browser #9186

Closed

andrewharvey mentioned this issue Jan 16, 2020

detect Brave browser configurations which break mapbox gl mapbox/mapbox-gl-supported#25

Closed

kkaefer mentioned this issue Feb 25, 2020

Detect fingerprint-blocking browsers mapbox/mapbox-gl-supported#28

Merged

andrewharvey mentioned this issue Apr 19, 2020

Using local webserver with Brave browser throws ajax error, prevents map rendering #9599

Closed

ryanhamley mentioned this issue Mar 29, 2021

maps not working brave browser #10518

Closed

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Blocking fingerprinting in browser settings can cause icons not to render or map not to render #8377

Blocking fingerprinting in browser settings can cause icons not to render or map not to render #8377

kbauhausness commented Jun 21, 2019 •

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peterqliu commented Jun 24, 2019 •

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1ec5 commented Jun 24, 2019

ahk commented Jun 24, 2019

ryanhamley commented Jun 24, 2019

ryanhamley commented Jun 27, 2019 •

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mourner commented Jun 27, 2019

asheemmamoowala commented Jun 27, 2019

ryanhamley commented Jun 28, 2019 •

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mourner commented Jul 1, 2019

ryanhamley commented Jul 1, 2019

ryanhamley commented Jul 19, 2019

andrewharvey commented Jan 16, 2020

Blocking fingerprinting in browser settings can cause icons not to render or map not to render #8377

Blocking fingerprinting in browser settings can cause icons not to render or map not to render #8377

Comments

kbauhausness commented Jun 21, 2019 • edited Loading

Steps to Trigger Behavior

Link to Demonstration

Expected Behavior

Actual Behavior

peterqliu commented Jun 24, 2019 • edited Loading

1ec5 commented Jun 24, 2019

ahk commented Jun 24, 2019

ryanhamley commented Jun 24, 2019

ryanhamley commented Jun 27, 2019 • edited Loading

mourner commented Jun 27, 2019

asheemmamoowala commented Jun 27, 2019

ryanhamley commented Jun 28, 2019 • edited Loading

mourner commented Jul 1, 2019

ryanhamley commented Jul 1, 2019

ryanhamley commented Jul 19, 2019

andrewharvey commented Jan 16, 2020

kbauhausness commented Jun 21, 2019 •

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peterqliu commented Jun 24, 2019 •

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ryanhamley commented Jun 27, 2019 •

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ryanhamley commented Jun 28, 2019 •

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