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Chameleon

Browser fingerprinting protection for everybody.

Chameleon is a Chrome privacy extension that :star2: detects fingerprinting-like activity, and :sparkles: protects against fingerprinting, currently by making Chrome look like Tor Browser.

:warning: WARNING :warning:

Chameleon is pre-alpha, developer-only software.

Please note that while Chameleon detects the use of canvas fingerprinting, Chameleon does not yet protect against it. See the coverage table below for more on Chameleon's current status.

The next step for Chameleon is to block scripts from loading based on their use of fingerprinting techniques, of which canvas fingerprinting is one. This work is in progress now (enabled by tying code execution to originating scripts in 25d7a5).

Detection

Chameleon detects font enumeration and intercepts accesses of fingerprinting-associated JavaScript objects like Window.navigator.

The number over Chameleon's button counts the number of suspected fingerprinters on the current page.

Protection

Since Tor users are supposed to all look alike, Chameleon attempts to blend in by altering request headers and JavaScript properties to match Tor Browser's values.

To start with, Chameleon covers Panopticlick's fingerprinting set, with more complete coverage in the works.

Chrome without Chameleon:

"before" screenshot

Chrome with Chameleon:

"after" screenshot

Tor Browser:

Tor Browser screenshot

Installation

To manually load Chameleon in Chrome, check out (or download and unzip) this repository, go to chrome://extensions/ in Chrome, make sure the "Developer mode" checkbox is checked, click on "Load unpacked extension..." and select the chrome folder inside your Chameleon folder.

To update manually loaded Chameleon, update your checkout, visit chrome://extensions and click on the "Reload" link right under Chameleon's entry.

You could also generate an installable CRX package. See below for details. To install from a CRX package, drag and drop the package file onto the chrome://extensions page.

Development setup

  1. npm install to install dev dependencies.
  2. npm run lint to check JS code for common errors/formatting issues.
  3. npm run watch to monitor extension sources for changes and regenerate extension JS bundles as needed. Leave this process running in a terminal as you work on the extension. Note that you still have to reload Chameleon in Chrome from the chrome://extensions page whenever you update Chameleon's injected script or background page.
  4. npm run dist to generate an installable CRX package. This requires having the signing key in ~/.ssh/chameleon.pem. To get a key, visit chrome://extensions/ in Chrome and click on the "Pack extension..." button to generate a CRX manually.

CSS sprites were generated with ZeroSprites.

Coverage

Fingerprinting techniqueDetectionProtectionNotes
Request header valuesdetection not possible in a browser extension?
window.navigator valuespartial protection (not all Firefox-specific Navigator properties added, Chrome-specific properties not yet removed)
window.navigator enumerationdetection only: object enumeration order differs between browsers
window.screen values
Date/time queriespartial protection (need to adjust the entire timezone, not just getTimezoneOffset)
Font enumerationunable to override fontFamily getters/setters on the CSSStyleDeclaration prototype in Chrome; needs more investigation
System color enumerationdetection planned, protection seems to run into the same issue as font enumeration
CSS media queriesneeds investigation
Canvas image data extractionprotection impeded by image rendering differences between Chrome and Firefox, but this is only a problem if we are trying to match Tor Browser.
WebGL?detection needs more work, protection needs investigation
Request header ordering/checksum, window.navigator checksum, checksumming in generalneeds investigation
Flash/Java-driven queriesplugins need to be switched to click-to-play by default
Third-party cookiesneed to disable by default
JS/rendering engine differencesTor Browser masquerading showstopper ...
Packet inspection/clock skew (?)not possible in a browser extension

Roadmap

Code license

Mozilla Public License Version 2.0