Builder, Remix, CSP

Technical Questions
1

I’m getting the following with a simple “hello world” builder.io page on our Remix/Hydrogen website:

Refused to execute inline script because it violates the following Content Security Policy directive: "script-src ‘self’ […]. Either the ‘unsafe-inline’ keyword, a hash (‘sha256-…’), or a nonce (‘nonce-…’) is required to enable inline execution.

Is there a way to make this (and any CSP-related-) error go away without adding any unsafe directives to our CSP? This is a show stopper for us.

Thanks!

2

Hey @contrebande welcome to Builder forum.

Handling Content Security Policy (CSP) issues while integrating Builder.io on websites such as Remix or Hydrogen can indeed be challenging, especially as you want to avoid the use of unsafe-inline directives for security reasons. Instead, you can make use of nonces, hashes, or strictly controlled script-src policies to manage CSP issues.

Below are some strategies and steps to handle CSP issues in a secure manner without compromising the security of your website:

1. Use Nonces

A nonce (number used once) is a random value that you generate on the server side and include in your CSP policy. You then add this nonce to script tags to whitelist them.

Steps to Use Nonces

  1. Generate a Nonce: Generate a secure random nonce on the server side for each request.
  2. Include the Nonce in CSP: Add the generated nonce to your CSP header.
  3. Add the Nonce to Script Tags: Add the nonce attribute to your inline script tags.

Example Implementation in a Remix/Hydrogen Website

Server-Side

In your server-side code, generate a nonce and include it in your response headers:

import crypto from 'crypto';
import { Response } from 'node-fetch';

// Function to generate a secure nonce
const generateNonce = () => crypto.randomBytes(16).toString('base64');

// Middleware to inject CSP policy with nonce
app.use((req, res, next) => {
  const nonce = generateNonce();
  res.locals.nonce = nonce; // Pass nonce to the response locals

  res.setHeader("Content-Security-Policy", 
    `script-src 'self' 'nonce-${nonce}';`); // Set the CSP header with the nonce

  next();
});

In Your Remix/Hydrogen Component

Use the nonce in your component to allow the inline script to run:

<script nonce={nonce}>
  console.log('Hello, world!');
</script>

Ensure that the nonce value is being correctly passed to your component and used in the script tags.

2. Use Hashes

Another approach is to use hashes. Instead of generating a nonce for each request, you pre-compute a hash based on the content of the script.

Steps to Use Hashes

  1. Compute the SHA-256 Hash: Compute the SHA-256 hash of the script content.
  2. Include the Hash in CSP: Add the hashed value to your CSP header.
  3. Ensure the Script Content Matches: The script content must match the hashed value that’s specified in the CSP.

Example Implementation for Using Hashes

First, calculate the hash of your inline script content:

echo -n "console.log('Hello, world!');" | openssl dgst -sha256 -binary | openssl base64

This command returns the hash value.

Next, include this hash in your CSP policy:

res.setHeader("Content-Security-Policy",  
  "script-src 'self' 'sha256-<hashed-value>';");

Replace <hashed-value> with the hash computed.

Example of Adding a Script Tag

<script>
  console.log('Hello, world!');
</script>

Ensure that the hashed value in the CSP matches the content of the script exactly.

Conclusion

By using either nonces or hashes, you can allow inline scripts to run without resorting to unsafe-inline, thus maintaining a strong CSP for security.

Summary Steps:

  1. Generate a Nonce/Hash: Generate a secure nonce for each request or compute a hash for the static script content.
  2. Include in CSP Header: Add the nonce/hash to the CSP headers.
  3. Modify Script Tags: Include the nonce/hash in the appropriate script tags.

This way, you maintain the security integrity of your site while leveraging the flexibility Builder.io offers. For more advanced handling, referring to Builder.io’s documentation and community forums can also be highly beneficial.