Tracking user with browser' fingerprint

Posted on | In

Single-browser

state of the art

Paper

Beauty and the Beast: Diverting modern web browsers to build unique browser fingerprints

Website

AmIUnique

Features

Attribute Source Function or Example
User agent HTTP header “Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36”
Accept HTTP header “text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8””text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,/;q=0.8”
Content encoding HTTP header “gzip, deflate, sdch, br”
Content language HTTP header “en-US,en;q=0.8”
List of plugins JavaScript navigator.plugins
Platform JavaScript navigator.platform
Cookies enabled JavaScript navigator.cookieEnabled
Do not track JavaScript navigator.doNotTrack
Timezone JavaScript new Date().getTimezoneOffset()
Screen resolution and depth JavaScript screen.width/height/colordepth
Use of local/session storage JavaScript localStorage/sessionStorage
Canvas JavaScript
WebGL Vendor JavaScript canvas.getContext(“…”)code 1
WebGL Render JavaScript canvas.getContext(“…”)code 1
Use of Adblock JavaScript Detect Adblock
List of fonts Sinde-channel List 1 in Cookieless Monstercode 2
List of fonts Flash flash.text.Font.enumerateFonts(true)
Screen resolution Flash flash.system.Capabilities.screenResolutionX/Y
Platform Flash flash.system.Capabilities.os
Language Flash flash.system.Capabilities.language

code 1

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var ctx = canvas.getContext("webgl") || canvas.getContext("experimental-webgl");
if(ctx.getSupportedExtensions().indexOf("WEBGL_debug_renderer_info") >= 0) {
    webGLVendor = ctx.getParameter(ctx.getExtension('WEBGL_debug_renderer_info').UNMASKED_VENDOR_WEBGL);
    webGLRenderer = ctx.getParameter(ctx.getExtension('WEBGL_debug_renderer_info').UNMASKED_RENDERER_WEBGL);
} else {
    webGLVendor = "Not supported";
    webGLRenderer = "Not supported";
}

code 2

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function get_text_dimensions(font){
  h = document.getElementsByTagName("BODY")[0];
  d = document.createElement("DIV");
  s = document.createElement("SPAN");
  d.appendChild(s);
  d.style.fontFamily = font;
  s.style.fontFamily = font;
  s.style.fontSize = "72px";
  s.innerHTML = "font_detection";
  h.appendChild(d);
  textWidth = s.offsetWidth;
  textHeight = s.offsetHeight;
  h.removeChild(d);
  return [textWidth, textHeight];
}

How to detect a specific Chrome extension is installed from regular HTML page

Each submitted extension on Chrome store has a special number.

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function detectExtension(extensionId, callback) {
    var img;
    img = new Image();
    img.src = "chrome-extension://" + extensionId + "/resources/icon_16.png";
    img.onload = function() {
        callback(true);
    };
    img.onerror = function() {
        callback(false);
    };

Cross-browser

Paper

(Cross-)Browser Fingerprinting via OS and Hardware Level Features

Website

UNIQUEMACHINE

Weakness

  • Small size of the training data
    Only 3,615 fingerprints from 1,903 users within three months.
  • WebGL tasks need a significant time overhead.

Contribution

  • AmIUnique considered WebGL is “too brittle and unreliable”. Because they select a random WebGL task and does not restrict many variables, such as texture, transparency, light, canvas size and anti-aliasing.
  • Some differences between rendering results are very subtle, i.e., with one or two pixel variance.
  • WebGL rendering is a combination of software and hardware in which the hardware contributes more than the software. The uniqueness of software rendering is definitely much lower than the one of hardware rendering but still not zero.

Features

Screen resolution
  • problem: The resolution changes in Firefox and IE when the user zooms in or out the web page.
  • method:
    • Detect the zoom levels based on the size of a div tag and the device pixel ratio, and then adjust the screen resolution correspondingly.
    • The ratio between screen width and height, which does not change with the zoom level.
  • addition:
    • availHeight, availWidth, availLeft, availTop, and screenOrientation.
    • Users may open different browser in different screens which have different resolutions.
Number of CPU virtual cores
  • method: navigator.hardwareConcurrency
  • addition: Safari will cut the number available cores to Web Workers by half.
AudioContext

Peak values and their corresponding frequencies are relatively stable across browsers.

List of fonts
  • problem: Not all fonts are cross-browser fingerprintable because some fonts are web specific and provided by browsers.
Line, curve and anti-aliasing

There are many existing algorithms for anti-aliasing, such as first-principles approach, signal processing approach, and mipmapping, which make anti-aliasing fingerprintable.

Vertex shader and fragment shader

Algorithm differs from one graphic card to another, making texture fingerprintable.

  • Varyings: Provide an interface between Vertex and Fragment Shader. The interpolation algorithm varies in different computer graphics cards.
  • Textures: Give a setting of mapping between vertexes and texture, a fragment shader calculates the color of each pixel based on the texture.
Transparency via Alpha Channel

Because some graphics cards adopt discrete alpha values, some jumps may be observed in the changes of transparency effects.

Image encoding and decoding

Different algorithms may uncover different information during decompression. Both DataURL and JPEG formats are unstable across different browsers, because these formats are with loss and implemented differently in multiple browsers and the server side as well.

  • problem: a single-browser feature, and cannot be used for cross-browser
Installed writing scripts (languages)

A browser with a particular language installed will display the language correctly, and otherwise show several boxes.

WebGL tasks

The size of the canvas is 256×256. The axes of the canvas are defined as follows. [0, 0, 0] is the middle of the canvas, where x-axis is the horizontal line that increases to the right, y-axis is the vertical line that increases to the bottom, and z-axis increases when moving far from the screen. An ambient light with the power of [R: 0.3, G: 0.3, B: 0.3] on a scale of 1 is present, and a camera is placed at the location of [0, 0, -7].

  • Task (a): Texture
    Randomly-generated texture rather than a regular will have more fingerprintable features.

  • Task (b): Varyings

  • Task (b’) Anti-aliasing + Varyings

  • Task (c) Camera（缩小立方体，减少了差异）
    Camera moved to a new location of [-1, -4, 10]

  • Task (d) Lines and curves

  • Task (d’) Anti-aliasing +Anti-aliasing + Lines and curves

  • Task (e) Multi-models
    信息熵比Task a就大了0.01

  • Task (f) Light
    a diffuse, point white light. The power of the light is 2 for each primary color, and the light source is located at [3.0, -4.0, -2.0].
    模型是彩色的，单色光可能会减少一些细微的差异。光照太弱不能照亮模型，太强会让所有都变成白色。位置是随机的。
    信息熵比Task a就大了一点点

  • Task (g) Light and models
    the interaction of a single, diffuse, point light and two models, because one model may create a shadow on another when illuminated by a point light.
    信息熵比Task f就大了一点点信息熵就大了0.03

  • Task (h) Specular Light
    test the effects of a diffuse point light with another color and a specular point light on two models.
    信息熵比Task e大了0.9（f比e大了0.01）

  • Task (h’) Anti-aliasing + Specular Light

  • Task (h”) Anti-aliasing + Specular Light + Rotation
    信息熵减小，稳定性增加，转了一面，信息变少了

  • Task (i) Two Textures（差了，第一层纹理是精心挑选的）
    Add another texture on the multi-models in Task e.

  • Task (j) Alpha

    • many GPUs do not accept smaller steps
    • the Suzanne and sofa models are positioned so that they are partially overlapped
      增加alpha的值，趋势是信息熵变大，但是有反反复复的回滚，原因是software rendering引起的

  • Task (k) Complex lights
    因为有5000多个模型，光的反射又互相影响，所以效果拔群

  • Task (k’) Anti-aliasing + Complex lights

  • Task (l) Clipping plane
    贡献不大

  • Task (m) Cubemap texture + Fresnel effect
    比较好，信息多cube map

  • Task (n) DDS textures
    微软那一套，一些浏览器不支持

  • Task (o) PVR textures
    只支持苹果设备

  • Task (p) Float textures
    比较好，信息多depth

  • Task (q) Video (Animating Textures)
    single-browser的效果好。decoding video is a combination of the browser, the driver, and sometimes the hardware as well.

  • Task (r) Writing Scripts

To be continued