Helmet for security headers in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import Helmet in a Node.js Express app.

Node.js

const express = require('express');
const helmet = require('[1]');
const app = express();

Drag options to blanks, or click blank then click option'

Abody-parser

Bhelmet

Ccors

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'helmet' in the require statement.

Forgetting to import Helmet before using it.

The helmet package is imported by requiring 'helmet'. This allows you to use Helmet middleware in your Express app.

2fill in blank

medium

Complete the code to use Helmet middleware in the Express app.

Node.js

const express = require('express');
const helmet = require('helmet');
const app = express();

app.[1](helmet());

Drag options to blanks, or click blank then click option'

Ause

Blisten

Cget

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using app.listen() instead of app.use().

Trying to use app.get() or app.post() for middleware.

Use app.use() to add Helmet as middleware so it runs on every request.

3fill in blank

hard

Fix the error in the code to set a custom Content Security Policy with Helmet.

Node.js

const helmet = require('helmet');

app.use(helmet.contentSecurityPolicy({
  directives: {
    defaultSrc: [[1]],
  }
}));

Drag options to blanks, or click blank then click option'

A'none'

Bself

C'self'

Dnone

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted self which causes syntax errors.

Using 'none' without quotes which is invalid.

The directive values must be strings with quotes, like 'self', to be valid in Helmet's Content Security Policy.

4fill in blank

hard

Fill both blanks to disable the Cross-Origin Embedder Policy and Cross-Origin Opener Policy in Helmet.

Node.js

app.use(helmet({
  crossOriginEmbedderPolicy: [1],
  crossOriginOpenerPolicy: [2]
}));

Drag options to blanks, or click blank then click option'

Afalse

Btrue

Cnull

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using true instead of false enables the feature.

Using null or undefined does not disable the feature.

Setting these options to false disables those specific security policies in Helmet.

5fill in blank

hard

Fill all three blanks to create a Helmet middleware that sets a custom Referrer Policy and enables DNS Prefetch Control.

Node.js

app.use(helmet({
  referrerPolicy: { policy: '[1]' },
  dnsPrefetchControl: { allow: [2] },
  frameguard: { action: '[3]' }
}));

Drag options to blanks, or click blank then click option'

Ano-referrer

Btrue

Cdeny

Dorigin

Attempts:

3 left

💡 Hint

Common Mistakes

Using false for dnsPrefetchControl.allow disables it instead of enabling.

Using incorrect strings for referrerPolicy or frameguard action.

Setting referrerPolicy to 'no-referrer' hides referrer info. Setting dnsPrefetchControl allow to true enables it. Setting frameguard action to 'deny' blocks framing.

Practice

1. What is the main purpose of using helmet in a Node.js Express application?

easy

A. To serve static files like images and CSS

B. To improve the app's database performance

C. To add security headers that protect the app from common web attacks

D. To handle user authentication and sessions

Solution

1. Step 1: Understand Helmet's role

   Helmet is a middleware that adds HTTP headers to improve security.

2. Step 2: Identify its main function

   It protects against attacks like cross-site scripting by setting headers.

3. Final Answer:

   To add security headers that protect the app from common web attacks -> Option C

4. Quick Check:

   Helmet = Security headers [OK]

Hint: Helmet adds security headers, not database or auth [OK]

Common Mistakes:

• Thinking Helmet manages authentication
• Confusing Helmet with static file serving
• Assuming Helmet improves database speed

2. Which of the following is the correct way to use Helmet in an Express app?

easy

A. import helmet from 'helmet'; app.use(helmet());

B. import helmet from 'helmet'; app.use(helmet);

C. const helmet = require('helmet'); app.use(helmet);

D. const helmet = require('helmet'); app.use(helmet());

Solution

1. Step 1: Check import syntax for modern Node.js

   Using ES modules, import helmet from 'helmet' is correct, but in CommonJS require syntax is used differently.

2. Step 2: Use helmet as middleware function

   Helmet must be called as a function: helmet() inside app.use().

3. Final Answer:

   const helmet = require('helmet'); app.use(helmet()); -> Option D

4. Quick Check:

   Require + call helmet() = correct usage [OK]

Hint: Remember to call helmet() when using app.use [OK]

Common Mistakes:

• Forgetting to call helmet() as a function
• Using require without calling helmet()
• Mixing import and require syntax incorrectly

3. Given this Express app code snippet, what HTTP header will Helmet add by default?

import express from 'express';
import helmet from 'helmet';
const app = express();
app.use(helmet());
app.get('/', (req, res) => res.send('Hello'));
app.listen(3000);

medium

A. Content-Security-Policy

B. X-DNS-Prefetch-Control

C. X-Powered-By

D. Strict-Transport-Security

Solution

1. Step 1: Recall Helmet default headers

   Helmet disables 'X-Powered-By' and adds several security headers by default.

2. Step 2: Identify which header Helmet sets by default

   Among options, 'X-DNS-Prefetch-Control' is one of the default headers Helmet adds.

3. Final Answer:

   X-DNS-Prefetch-Control -> Option B

4. Quick Check:

   Helmet default header = X-DNS-Prefetch-Control [OK]

Hint: Helmet adds X-DNS-Prefetch-Control by default [OK]

Common Mistakes:

• Assuming Content-Security-Policy is always set by default
• Thinking X-Powered-By header is added instead of removed
• Confusing Strict-Transport-Security which needs HTTPS setup

4. What is wrong with this Helmet usage in an Express app?

import helmet from 'helmet';
app.use(helmet);

medium

A. Helmet middleware is not called as a function

B. Helmet is not imported correctly

C. Helmet should be used after route definitions

D. Helmet requires additional configuration to work

Solution

1. Step 1: Check how helmet is used in app.use

   Helmet must be called as a function: helmet() not just helmet.

2. Step 2: Identify the error in middleware usage

   Using app.use(helmet) passes the function itself, not the middleware it returns.

3. Final Answer:

   Helmet middleware is not called as a function -> Option A

4. Quick Check:

   Call helmet() to use middleware [OK]

Hint: Always call helmet() in app.use [OK]

Common Mistakes:

• Passing helmet without parentheses
• Importing helmet incorrectly
• Placing helmet after routes (should be before)

5. You want to disable the contentSecurityPolicy header in Helmet but keep all other default headers. Which code snippet correctly does this?

hard

A. app.use(helmet({ contentSecurityPolicy: false }));

B. app.use(helmet.contentSecurityPolicy(false));

C. app.use(helmet.disable('contentSecurityPolicy'));

D. app.use(helmet({ disable: ['contentSecurityPolicy'] }));

Solution

1. Step 1: Understand Helmet configuration object

   Helmet accepts an options object where you can disable specific headers by setting them to false.

2. Step 2: Identify correct syntax to disable contentSecurityPolicy

   Setting contentSecurityPolicy: false inside helmet() disables only that header.

3. Final Answer:

   app.use(helmet({ contentSecurityPolicy: false })); -> Option A

4. Quick Check:

   Disable header by setting false in options [OK]

Hint: Use helmet({ contentSecurityPolicy: false }) to disable it [OK]

Common Mistakes:

• Trying to call helmet.contentSecurityPolicy as a function
• Using non-existent disable method
• Passing disable array instead of options object