Validate CSP from Command Line

By  on  

The content security policy spec has been an amazing front-end security tool to help prevent XSS and other types of attacks. I'd go as far to say that every site should implement as specific CSP as possible. If you aren't familiar with CSPs, here's a quick example:

Content-Security-Policy: default-src 'self'; img-src *; media-src media1.com media2.com; script-src userscripts.example.com

If a linked resource or content on the page doesn't pass a given CSP rule, it wont be loaded. Of course getting a massive site to pass one CSP is difficult -- just ask Facebook:

Browsers provide you CSP error and warning information in the web console but that doesn't help developers prevent issues before a push to production. Enter seespee -- a Node.js utility that allows you to validate CSPs from command line!

To get the CSP directives for a given page, you simply run seespee with a URL:

seespee https://davidwalsh.name/demo/csp-example.php

/*
Content-Security-Policy:
  default-src 'self';
  frame-ancestors 'self';
  frame-src 'none';
  img-src 'none';
  media-src 'self' *.example.com;
  object-src 'none';
  report-uri https://example.com/violationReportForCSP.php;
  script-src 'self' 'unsafe-inline' cdnjs.cloudflare.com;
  style-src 'self' 'unsafe-inline';
*/

If you'd like to validate that a given page's CSP passes, which you could do during build or in CI, add the --validate flag:

seespee https://davidwalsh.name/demo/csp-example.php --validate

/*
✘ ERROR: Validation failed: The Content-Security-Policy does not whitelist the following resources:
            script-src cdnjs.cloudflare.com;
              https://cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7/html5shiv.js
*/

If the validation step returns a non-zero status, you know CSP has failed and thus the patch shouldn't be merged.

You can also use seespee from within your Node.js scripts:

var seespee = require('seespee');
seespee('https://davidwalsh.name/demo/csp-example.php').then(function(result) {
  console.log(result.contentSecurityPolicy);
  // default-src \'none\'; style-src https://assets-cdn.github.com; ...
});

Having a utility like seespee, and not needing to manually check in the browser, is so useful. A solid CSP can be difficult to create but even harder to maintain as the site changes. Use seespee and CI to prevent unwanted CSP and site fails!

Recent Features

  • By
    Designing for Simplicity

    Before we get started, it's worth me spending a brief moment introducing myself to you. My name is Mark (or @integralist if Twitter happens to be your communication tool of choice) and I currently work for BBC News in London England as a principal engineer/tech...

  • By
    CSS 3D Folding Animation

    Google Plus provides loads of inspiration for front-end developers, especially when it comes to the CSS and JavaScript wonders they create. Last year I duplicated their incredible PhotoStack effect with both MooTools and pure CSS; this time I'm going to duplicate...

Incredible Demos

  • By
    Create a Simple News Scroller Using MooTools, Part I:  The Basics

    News scroller have been around forever on the internet. Why? Because they're usually classy and effective. Over the next few weeks, we'll be taking a simple scroller and making it into a flexible, portable class. We have to crawl before we...

  • By
    Image Data URIs with PHP

    If you troll page markup like me, you've no doubt seen the use of data URI's within image src attributes. Instead of providing a traditional address to the image, the image file data is base64-encoded and stuffed within the src attribute. Doing so saves...

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!