Google Analytics Content Security Policy

Question

I have the Content Security Policy:

default-src 'none';
style-src 'self';
script-src 'self' https://www.google-analytics.com;
img-src 'self' https://www.google-analytics.com;
connect-src 'self';

On my page I have put the inline GA code into an async script:

<script src="/javascript/ga.js" async></script>

This causes a CSP error:

Refused to load the script 'data:application/javascript;base64,KGZ1bmN0aW9uKCkgewoJLy8gaHR0cHM6Ly9kZXZl…07Cgl9OwoJZ2EucmVtb3ZlID0gbm9vcGZuOwoJd2luZG93W2dhTmFtZV0gPSBnYTsKfSkoKTs=' because it violates the following Content Security Policy directive: "script-src 'self' https://www.google-analytics.com".

Is there any way to serve this script from a JS file, and if not how would I need to change the CSP?

Answer 1

Google Analytics is CSP-compatible. The base64-encoded data: blob OP is seeing is being injected by the uBlock Origin extension. To verify, disable it/try incognito. IIRC, this is due to an "experimental/unbreak" setting in the extension.

Please resist the temptation to whitelist data: in script-src. That would make the policy completely useless for XSS mitigation, since an attacker could just inject <script src="data:text/javascript,alert(1)"></script> to execute Javascript.