RAPPOR shield study prototype

This is a research prototype built as part of an internship project. See the Mozilla Governance thread for context.

Introduction

This addon is a SHIELD Study that collects the eTLD+1 of the user's homepage and applies RAPPOR, a Differential Privacy algorithm, to encode and obfuscate it. The result is sent in a custom ping with no clientId or environment information.

The purpose of this study is to confirm that we can get representative data, preserving indivudual user privacy, for the Firefox population. Using RAPPOR we collect aggregate data on the most common domain value users set their homepage to (e.g. foo.com) or the value of "about:home".

Addon Behaviour

The addon extracts the eTLD+1 from the value stored in the browser.startup.homepage preference and applies RAPPOR (bug 1379195) to make it anonymous. It can fail if the host is an IP address or is empty when calling Services.eTLD.getBaseDomain. In such case, the study ends. For example, if the value stored in the preference is foo.bar.com the addon applies RAPPOR to bar.com and then sends the anonymized bit field out. Other possiblity is that the user's homepage is about:home or other about: page. In the case of about:home, this is the value we use. In the case of other about: page, the reported value is about:pages.

The algorithm returns two values, the cohort and the encoded input value. This is sent in a custom ping.

The cohort is stored in a preference if more than one value needs to be reported.

Data format

This opt-out ping is sent from the addon when RAPPOR is successfully applied to the extracted eTLD+1 value.

Structure

{
  "type": "shield-study-addon",
  ... common ping data
  },
  "payload": {
    "version": <int> // 3,
    "study_name": <string> // "TelemetryRAPPOR",
    "branch": <string> // "eTLD+1",
    "addon_version": <string> // "1.0.0",
    "shield_version": <string> // "4.0.0",
    "type": <string> // "shield-study-addon",
    "data": {
      "attributes": {
        "cohort": <string> // "6",
        "report": <string> // "180504828f142c0204000004010346c0"
      }
    },
    "testing": false
  },
  ... ping data
}

payload.version

This field contains the version of the payload.

payload.study_name

This field contains the name of the study, as set in Config.jsm.

payload.branch

This field contains the branch of the experiment. In this case, the experiment has only one branch.

payload.addon_version

This field contains the version of the adddon, as set in package.json.

payload.shield_version

This field contains the version of the Shield study addons library.

payload.type

This field contains the type of the payload. In this case, shield-study-addon.

payload.data.attributes.cohort

This field contains the cohort to which a client belongs to.

payload.data.attributes.report

This field contains the RAPPOR value of the user's homepage.

Development

Install

npm install npm run build

At second shell/prompt, watch files for changes to rebuild:

npm run watch

In Firefox:

1. about:debugging > [load temporary addon] > choose dist/addon.xpi
2. tools > Web Developer > Browser Toolbox.

Description of the files

• HomepageStudy.jsm: implements the logic to extract the eTLD+1 from the preference and apply RAPPOR.
• TelemetryRappor.jsm: implements the RAPPOR algorithm and the related utility functions.
• StudyUtils.jsm: miscellaneous SHIELD utils.
• bootstrap.js: contains addon specific boilerplate code.

Description of architecture

This addon is structured as a restartless (bootstrap.js) extension.

During bootstrap.js:startup(data, reason):

1. shieldUtils imports and sets configuration from Config.jsm.
2. Modules are imported.
3. Study is setted up.
4. RAPPOR is executed.
5. boostrap.js waits for requests from HomepageStudy.jsm the that are study related: ["info", "telemetry", "endStudy"].
6. Data is sent to Telemetry.
7. The study ends and the addon is uninstalled.

Simulations

To validate using the simulator, the addon can be set to work in simulation mode:

1. Clone the RAPPOR simulator repository:

git clone https://github.com/Alexrs95/rappor

2. Follow the instructions to install the dependencies.

3. Generate data (You can find the list of possible data distributions in tests/regtest_spec.py:

./regtest.sh gen-values 'zipf1.5-tiny2-sim_final2'

4. Set the option isSimulation to true in addon/Config.jsm.

5. Set the option rapporSimulatorPath to the location of the RAPPOR simulator in addon/Config.jsm.

6. Build the addon with npm run build.

7. Run the addon. In Firefox: about:debugging > [load temporary addon] > choose dist/addon.xpi.

8. Perform the analysis:

./regtest.sh analysis 'r-zipf1.5-tiny2-sim_final2' 1 'python'