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evoelise
Asked: 2020-04-24 06:52:30 +0800 CST

Google Cloud Services Content Security Policy Issues

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I have a static web site hosted in a bucket that I serve up via the Google Platform.

This site has been running with no problems for about 6 months but over the last month I have had intermittent problems with it not loading style sheets and scripts due to "Content Security" issues - this results in just the text of the main page appearing the browser with no style and no (Javascript based) functionality. By intermittent I mean it works OK for a couple of hours and then it fails for a couple of hours.

There is no "web server" for this service as such as I am just serving up static pages from a bucket - I understand that Google must have their own server that handles this though.

Checking the developer console in the browser I can see the following issues for all stylesheets, scripts and fonts that the web page uses:

Refused to load the stylesheet XXXXXXX because it violates the following Content Security Policy directive: "default-src 'none'". Note that 'style-src-elem' was not explicitly set, so 'default-src' is used as a fallback.

I think I have got my Content Security settings correct:

   <meta http-equiv="Content-Security-Policy" content="
         default-src 'self'; 
         img-src 'self'
            https://syndication.twitter.com;
         font-src 'self'    
            https://use.fontawesome.com
            https://fonts.gstatic.com
            https://fonts.googleapis.com;
         script-src 'self' 'unsafe-inline'
            https://stackpath.bootstrapcdn.com 
            https://connect.facebook.net
            https://platform.twitter.com
            https://code.jquery.com
            https://cdnjs.cloudflare.com; 
         style-src 'self' 'unsafe-inline'
            https://stackpath.bootstrapcdn.com 
            https://use.fontawesome.com 
            https://fonts.googleapis.com;
         frame-src 'self'   
            https://www.facebook.com
            https://connect.facebook.net
            https://platform.twitter.com
            https://www.youtube.com;
   ">

These are the links that fail, each 'external' one includes signing with the imports to ensure that the "real" thing is loaded.

    <!-- Bootstrap core CSS -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous">

    <!-- Font Awesome -->
    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.2.0/css/all.css" integrity="sha384-hWVjflwFxL6sNzntih27bfxkr27PmbbK/iSvJ+a4+0owXq79v+lsFkW54bOGbiDQ" crossorigin="anonymous">

    <!-- Custom fonts for this template -->
    <link href='https://fonts.googleapis.com/css?family=Titillium+Web' rel='stylesheet' type='text/css'>
    <link href='https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800' rel='stylesheet' type='text/css'>

Can anyone see what I am doing wrong or offer any advice on how to get this working consistently?

google-cloud-platform html content-security-policy

1 Answers

  1. As it was suggested in the comment section by @Bruno this issue was already solved in this question. For better usability I'm copy-pasting (with links) two solutions that users confirmed worked;

    Solution 1

    <meta http-equiv="Content-Security-Policy" content="default-src * self blob: data: gap:; style-src * self 'unsafe-inline' blob: data: gap:; script-src * 'self' 'unsafe-eval' 'unsafe-inline' blob: data: gap:; object-src * 'self' blob: data: gap:; img-src * self 'unsafe-inline' blob: data: gap:; connect-src self * 'unsafe-inline' blob: data: gap:; frame-src * self blob: data: gap:;">

    Warning: This exposes the document to many exploits. Here's a detailed explanation about possible security risk and exploitation.

    Solution 2

    To elaborate some more on this, adding

    script-src 'self' http://somedomain 'unsafe-inline' 'unsafe-eval';

    to the meta tag like so,

    <meta http-equiv="Content-Security-Policy" content="default-src 'self' data: gap: https://ssl.gstatic.com 'unsafe-eval'; style-src 'self' 'unsafe-inline'; script-src 'self' https://somedomain.com/ 'unsafe-inline' 'unsafe-eval';  media-src *">

    fixes the error.

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