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How to set up Content Security Policy (CSP) for FTW

This guide describes how to set up CSP for Flex Template for Web (FTW).

According to MDN:

Content Security Policy (CSP) is an added layer of security that helps to detect and mitigate certain types of attacks, including Cross Site Scripting (XSS) and data injection attacks. These attacks are used for everything from data theft to site defacement or distribution of malware.

By default the CSP is disabled in FTW. By turning it on, the default whitelist in server/csp.js works with the all the URLs and tools that come with the application.

Turn on the CSP

The CSP is configured using the REACT_APP_CSP environment variable.

Possible values:

  • not set: disabled
  • REACT_APP_CSP=report: Enabled, but policy violations are only reported
  • REACT_APP_CSP=block: Enabled. Policy violations are reported and requests that violate the policy are blocked

If error logging with Sentry is enabled (See the How to set up Sentry to log errors in FTW guide), the reports are sent to Sentry. Otherwise the reports are just logged in the backend.

Optional: Extend the policy

If you want to whitelist new sources (for example adding a new external analytics service) and keep the CSP enabled, you should add the domains to the white list in server/csp.js.

The easiest way to do this is to first turn on the policy in report mode and then see what policy violations are logged to the browser developer console or to the backend policy violation report URL.

Resources

To understand what CSP is and how browsers work, here are some resources: