Handling Fluid IP Addresses in CSP Settings for NestJS Backend with Helmet

Backend
1

Help! CSP and Dynamic IPs Are Giving Me a Headache

I’m building a web app with React and NestJS. My backend uses Helmet for Content Security Policy stuff. Here’s the problem: I need to connect to an API on a scanner that keeps changing its IP address. The scanner’s current IP is stored in my database.

Right now, my Helmet setup in NestJS looks like this:

app.use(
  helmet({
    contentSecurityPolicy: {
      directives: {
        'connect-src': ["'self'", '123.45.67.89'], // Hard-coded IP
        // other directives...
      }
    }
  })
)

But this doesn’t work when the scanner’s IP changes. I get errors like:

Refused to connect to 'http://98.76.54.32/api/scan' because it violates CSP

I’ve tried setting CSP in the frontend, but the backend seems to override it. I’m stuck!

How can I make this work with changing IPs? Is it okay to use wildcards in CSP? What’s the best way to keep things secure but flexible?

Thanks for any help you can offer!

2

Have you considered implementing a middleware solution? You could create a custom middleware that fetches the current scanner IP from your database before each request. This middleware could then dynamically update the CSP headers with the correct IP.

Here’s a basic approach:

  1. Create a middleware function that retrieves the IP.
  2. Use app.use() to apply this middleware before your Helmet configuration.
  3. Modify your Helmet setup to use a function for the ‘connect-src’ directive.

This way, you’re always using the most up-to-date IP without compromising security. It’s more efficient than updating on every request and avoids potential race conditions. Just ensure you have a reliable method to update the database when the scanner’s IP changes.

3

yo, that’s a tricky one! maybe u could try using environment variables for the IP? like, set it when ur app starts up and update it whenever the scanner IP changes. then use that variable in ur helmet config. might be worth a shot. good luck!

4

hmmm, interesting problem! have you considered using a reverse proxy or api gateway? that could help mask the changing IPs behind a consistent domain. or maybe you could update the CSP dynamically on each request based on the current IP in your database? just brainstorming here, curious what others think?