Feature #85: Added Helmet middleware with custom CSP to improve API s…

[jikrana1]

📋 Pull Request — Add Helmet Middleware to Improve API Security

🔗 Related Issue

Closes #85 — [Feature]: Add Helmet Middleware to Improve API Security

✅ Changes Made

• Created a dedicated middleware file: middleware/helmetMiddleware.js to centralize the security configuration.
• Configured helmet with crossOriginEmbedderPolicy: false and a custom Content-Security-Policy to ensure the React/Vite frontend remains fully functional (HMR, WebSockets, assets).
• Imported and registered the middleware in app.js using app.use(helmetMiddleware).

🧪 Testing Checklist

• Server starts successfully without errors.
• Frontend (Vite/React) runs correctly without CSP blocks.
• Existing API routes function correctly.

Summary by CodeRabbit

• New Features
  • Added stronger security protections for the backend by applying security-focused HTTP headers.
  • Updated browser access rules to better support the app’s existing resources and real-time connections.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds the helmet package as a backend dependency, introduces a new middleware module configuring Helmet with a custom content security policy, and registers this middleware in the Express server's global middleware chain.

Changes

Helmet Middleware Integration

Layer / File(s)	Summary
Helmet dependency addition backend/package.json	Adds helmet (^8.2.0) to the dependencies list.
Helmet middleware configuration and wiring backend/src/middleware/helmetMiddleware.js, backend/src/server.js	Creates a configured Helmet instance disabling crossOriginEmbedderPolicy and setting a custom contentSecurityPolicy (scriptSrc, styleSrc, fontSrc, imgSrc, connectSrc), then imports and registers it via app.use(helmetMiddleware) in the Express middleware chain.

Estimated code review effort: 2 (Simple) | ~10 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant ExpressServer
  participant helmetMiddleware

  Client->>ExpressServer: HTTP request
  ExpressServer->>helmetMiddleware: app.use(helmetMiddleware)
  helmetMiddleware-->>ExpressServer: apply security headers (CSP, crossOriginEmbedderPolicy)
  ExpressServer-->>Client: response with security headers

Loading

Possibly related issues

• Add global input sanitization and security headers (express-mongo-sanitize + helmet) as defense-in-depth #79: Adds the same helmet dependency and registers it in backend/src/server.js as global security middleware, directly overlapping this PR's changes.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: adding Helmet middleware with a custom CSP for API security.
Linked Issues check	✅ Passed	The PR adds the helmet dependency, registers the middleware in app initialization, and stays aligned with the issue goals.
Out of Scope Changes check	✅ Passed	The changes are limited to Helmet dependency, middleware setup, and app registration, with no obvious out-of-scope additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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Warning

⚠️ This pull request shows signs of AI-generated slop (redundant_comments, description_diff_mismatch, ai_padded_prose). It has been flagged by CodeRabbit slop detection and should be reviewed carefully.

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@backend/src/middleware/helmetMiddleware.js`:
- Around line 10-14: The CSP in helmetMiddleware currently applies Vite HMR
relaxations in all environments, weakening production security. Update the
helmetMiddleware configuration to branch on NODE_ENV so scriptSrc and connectSrc
only include "'unsafe-inline'", "'unsafe-eval'", and "ws:" during development,
while the production policy stays strict; use the existing helmetMiddleware
setup in backend/src/middleware/helmetMiddleware.js as the place to split the
directives.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c828c26d-2fa9-4b02-8434-7a44cd208091

📥 Commits

Reviewing files that changed from the base of the PR and between 87148ba and 8a5d5ed.

⛔ Files ignored due to path filters (1)

• backend/package-lock.json is excluded by !**/package-lock.json

📒 Files selected for processing (3)

• backend/package.json
• backend/src/middleware/helmetMiddleware.js
• backend/src/server.js

[coderabbitai]

🔒 Security & Privacy | 🟠 Major | ⚡ Quick win

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Verify whether production already sets NODE_ENV and whether additional CSP allowances are required.
rg -n -C2 'NODE_ENV|helmetMiddleware|contentSecurityPolicy|unsafe-eval|unsafe-inline|connectSrc|express\.static|vite' backend package.json

Repository: niharika-mente/ThinkBoard

Length of output: 3556

---

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '\n== package scripts ==\n'
cat package.json 2>/dev/null || true

printf '\n== backend files of interest ==\n'
git ls-files 'backend/src/**' 'frontend/**' | sed -n '1,200p'

printf '\n== helmet middleware ==\n'
cat -n backend/src/middleware/helmetMiddleware.js

printf '\n== server bootstrap around middleware ==\n'
sed -n '1,130p' backend/src/server.js

printf '\n== search for CSP / Vite / HMR env gating ==\n'
rg -n -C2 'helmetMiddleware|contentSecurityPolicy|unsafe-eval|unsafe-inline|connectSrc|crossOriginEmbedderPolicy|NODE_ENV|vite|HMR|hot' backend frontend package.json

Repository: niharika-mente/ThinkBoard

Length of output: 18934

---

Restrict the Vite HMR CSP relaxations to development.
helmetMiddleware is applied in backend/src/server.js for both dev and production, so "'unsafe-inline'", "'unsafe-eval'", and ws: currently weaken the production CSP too. Split these directives by NODE_ENV and keep the stricter policy in prod.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@backend/src/middleware/helmetMiddleware.js` around lines 10 - 14, The CSP in
helmetMiddleware currently applies Vite HMR relaxations in all environments,
weakening production security. Update the helmetMiddleware configuration to
branch on NODE_ENV so scriptSrc and connectSrc only include "'unsafe-inline'",
"'unsafe-eval'", and "ws:" during development, while the production policy stays
strict; use the existing helmetMiddleware setup in
backend/src/middleware/helmetMiddleware.js as the place to split the directives.