CSP Evaluator Core Library

Introduction

Please note: this is not an official Google product.

CSP Evaluator allows developers and security experts to check if a Content Security Policy (CSP) serves as a strong mitigation against cross-site scripting attacks. It assists with the process of reviewing CSP policies, and helps identify subtle CSP bypasses which undermine the value of a policy. CSP Evaluator checks are based on a large-scale study and are aimed to help developers to harden their CSP and improve the security of their applications. This tool (also available as a Chrome extension) is provided only for the convenience of developers and Google provides no guarantees or warranties for this tool.

CSP Evaluator comes with a built-in list of common CSP whitelist bypasses which reduce the security of a policy. This list only contains popular bypasses and is by no means complete.

The CSP Evaluator library + frontend is deployed here: https://csp-evaluator.withgoogle.com/

Build Prerequisites

These instructions have been tested with the following software:

java >= 1.7 — for running the Closure Compiler
ant — for building CSP-Evaluator dependencies
git
curl
a web server
a browser with HTML5 support

CSP Evaluator Setup

These instructions assume a working directory of the repository root.

CSP Evaluator includes an easy-to-use setup script called do.sh. It supports the following commands:

Setup: ./do.sh {install_deps|check_deps}
Build: ./do.sh {build|build_templates} [debug]
Cleanup: ./do.sh {clean|clean_deps}

Build

To build CSP Evaluator, run the following commands:

./do.sh install_deps
./do.sh build

Local Demo Server

To run the demo locally, you can use the Python SimpleHTTPServer:

cd build
python -m SimpleHTTPServer 9000
Navigate to http://localhost:9000/demo.html in your browser

Example usage

If you don't want to make any customization you can also just embed the compiled JS (build/evaluator_binary.js) and evaluate CSP like this:

<html>
  <div id="csp_widget"></div>
  <script src="/evaluator_binary.js"></script>
  <script>
    var rawCsp = "script-src data: https://www.google.com;";
    var parser = new csp.CspParser(rawCsp);
    var evaluator = new csp.CspEvaluator(parser.csp, csp.Version.CSP3);
    var findings = evaluator.evaluate();
    var widget = new csp.ui.Widget(parser.csp, findings, csp.Version.CSP3);
  </script>
</html>

zigoo0 / csp-evaluator