Factom & StackBlitzed
Factom
Hey, I’ve been digging into ways to make sure sensitive data never slips out of our client‑side code. Think we could hash out a solid, step‑by‑step approach that keeps the leaks at bay?
StackBlitzed
Sure thing, just keep it tight and don’t let any of that data leak past the edge of the browser. Here’s a quick recipe:
1. **Never store secrets in the code** – drop any API keys, tokens, or passwords out of the repo and into a server‑side env. If it has to go somewhere on the client, use a short‑lived, signed token that expires fast.
2. **Use HTTPS everywhere** – enforce TLS 1.2+ and pin the certificates if you can. Nothing gets past the network layer if it’s all encrypted.
3. **Apply Content‑Security‑Policy (CSP)** – block inline scripts, only allow trusted sources, and use nonce or hash for any needed inline code. That stops XSS which is the usual leak vector.
4. **Minimize exposed data** – send only the fields you need. Strip any PII before it hits the network.
5. **Hash sensitive values before sending** – use a client‑side hash (SHA‑256 is fine) if you need to verify something locally, but don’t rely on it for auth. Keep the salt on the server.
6. **Avoid eval and dynamic imports** – those let attackers inject code. Stick to static imports and well‑known modules.
7. **Audit third‑party libs** – use a lockfile, lock to a known good commit, and keep the old, deprecated libs in a separate folder for nostalgia.
8. **Rate‑limit and detect anomalies** – if a single client is spamming the endpoint, block it.
9. **Test in isolation** – run the app in a sandboxed iframe with strict sandbox attributes, then integrate.
10. **Continuous monitoring** – watch the commit history, set up a simple script that scans for any new strings that look like secrets, and fail the build if it finds one.
That’s the core loop. Throw a couple of unit tests on each boundary, stay caffeine‑fed, and you’ll keep the leaks at bay. Let me know if you want a deeper dive on any step.
Factom
Looks solid, the checklist hits every critical point. If you need deeper guidance on, say, the CSP hash strategy or the server‑side salt management, just let me know which area you want to drill into next.
StackBlitzed
Sure, let’s start with the CSP hash side—tell me which tags or scripts you’re trying to lock down, and we’ll hash it out in the terminal before we hit the deadline.
Factom
The first thing is to list the only inline pieces that actually need to run – usually just a small bootstrap script or a tiny event handler. Anything else should live in a separate .js file that you load with a normal script tag. For the inline parts, you generate a SHA‑256 hash of the exact source text, then put that in the CSP like: script-src 'self' 'sha256‑<base64hash>'; If you have a <style> block that does a few critical styles, hash that too and add it to style-src. Make sure the hash matches the exact characters, including whitespace – that’s why we keep the inline code in a single string. Once you have the hash list, drop it into your policy header, test in the browser console, and you’ll see the errors for anything not matching. If you need help computing the hash for a particular snippet, just paste it in and I can walk you through the command.
StackBlitzed
Got it – just paste the exact inline code block and I’ll run the OpenSSL hash for you right now. In a terminal you’d do something like:
```
echo -n 'your code here' | openssl dgst -sha256 -binary | base64
```
That gives you the Base‑64 string to drop into `script-src 'sha256-…'`. If you want me to run it on your snippet, just drop the text in and I’ll spit out the hash for you.
Factom
Here’s a tiny inline snippet you might keep in a <script> tag that adds a click handler:
document.addEventListener('DOMContentLoaded', function(){ const btn=document.querySelector('#submit'); if(btn){ btn.addEventListener('click', e=>{ e.preventDefault(); console.log('submitted'); }); } });
To hash it, copy exactly the text inside the single quotes—no extra spaces or line breaks—and run the command you mentioned. The resulting base‑64 string is what goes after 'sha256-'. Once you add that to your CSP header and test in a browser, any change to the script will trigger a violation, which gives you immediate feedback. Let me know if you need help adjusting it for your own code.