HSTS header in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add the HSTS header in nginx configuration.

Nginx

add_header Strict-Transport-Security "[1]";

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

Amax-age=31536000

Bmax-age=0

Cmax-age=100

Dmax-age=abc

Attempts:

3 left

💡 Hint

Common Mistakes

Using max-age=0 disables HSTS.

Using non-numeric values causes errors.

The max-age directive sets the time in seconds that browsers should remember to only use HTTPS. 31536000 seconds equals 1 year, which is a common recommended value.

2fill in blank

medium

Complete the code to include subdomains in the HSTS policy.

Nginx

add_header Strict-Transport-Security "max-age=31536000; [1]";

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

Ainclude-subdomains

BincludeSubdomain

CincludeSubDomains

Dinclude_subdomains

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the directive or using wrong case.

Using underscores or hyphens instead of camelCase.

The correct directive to include all subdomains in the HSTS policy is includeSubDomains (case sensitive, no spaces).

3fill in blank

hard

Fix the error in the HSTS header to enable preload.

Nginx

add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; [1]";

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

Apreload

Bpre-load

Cpre_load

Dpreload=true

Attempts:

3 left

💡 Hint

Common Mistakes

Adding '=' or other symbols after preload.

Using hyphens or underscores in the directive.

The correct directive to enable HSTS preload is preload without any equals sign or hyphens.

4fill in blank

hard

Fill both blanks to set HSTS with max age and include subdomains.

Nginx

add_header Strict-Transport-Security "[1]; [2]";

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

Amax-age=63072000

BincludeSubDomains

Cmax-age=31536000

DincludeSubdomain

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect max-age values.

Misspelling includeSubDomains.

Use max-age=31536000 for one year and includeSubDomains to cover all subdomains.

5fill in blank

hard

Fill all three blanks to set HSTS with max age, include subdomains, and preload.

Nginx

add_header Strict-Transport-Security "[1]; [2]; [3]";

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

Amax-age=15768000

BincludeSubDomains

Cpreload

Dmax-age=31536000

Attempts:

3 left

💡 Hint

Common Mistakes

Using too short max-age values.

Misspelling preload or includeSubDomains.

The recommended HSTS header includes max-age=31536000 (1 year), includeSubDomains, and preload to enable browser preload lists.

Practice

1. What is the main purpose of the Strict-Transport-Security (HSTS) header in nginx?

easy

A. To force browsers to use HTTPS instead of HTTP for the site

B. To redirect HTTP requests to a different domain

C. To enable caching of static files in the browser

D. To compress responses sent to the client

Solution

1. Step 1: Understand HSTS header purpose

   The HSTS header tells browsers to only use HTTPS for the site, improving security.

2. Step 2: Compare options with HSTS function

   Only To force browsers to use HTTPS instead of HTTP for the site matches this purpose; others describe unrelated features.

3. Final Answer:

   To force browsers to use HTTPS instead of HTTP for the site -> Option A

4. Quick Check:

   HSTS = Force HTTPS [OK]

Hint: HSTS means browsers must use HTTPS always [OK]

Common Mistakes:

• Confusing HSTS with redirects
• Thinking HSTS controls caching
• Assuming HSTS compresses data

2. Which of the following is the correct nginx syntax to add an HSTS header that lasts for 1 year and applies to all subdomains?

easy

A. add_header Strict-Transport-Security max-age=31536000 includeSubDomains always;

B. add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;

C. add_header Strict-Transport-Security "max-age=31536000 includeSubDomains";

D. add_header Strict-Transport-Security max-age=31536000; includeSubDomains always;

Solution

1. Step 1: Check correct syntax for add_header

   The header value must be a quoted string with directives separated by semicolons, and 'always;' ensures it is added on all responses.

2. Step 2: Validate option formatting

   add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always; correctly quotes the value and uses semicolon between directives with 'always;'. Others miss quotes or semicolons or misplace 'always'.

3. Final Answer:

   add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always; -> Option B

4. Quick Check:

   Quotes + semicolon + always = add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always; [OK]

Hint: Use quotes and semicolons inside add_header value [OK]

Common Mistakes:

• Missing quotes around header value
• Forgetting semicolon between directives
• Placing 'always' inside quotes

3. Given this nginx config snippet:

add_header Strict-Transport-Security "max-age=86400; includeSubDomains" always;

What is the effect on browsers visiting the site?

medium

A. Browsers will enforce HTTPS for 1 day on the site and all subdomains

B. Browsers will enforce HTTPS for 1 year on the site only

C. Browsers will ignore the header because max-age is too low

D. Browsers will enforce HTTPS for 1 day on the site only

Solution

1. Step 1: Interpret max-age and includeSubDomains

   max-age=86400 means 86400 seconds = 1 day. includeSubDomains applies to all subdomains.

2. Step 2: Understand browser behavior

   Browsers will enforce HTTPS for 1 day on the site and all its subdomains as per header.

3. Final Answer:

   Browsers will enforce HTTPS for 1 day on the site and all subdomains -> Option A

4. Quick Check:

   86400 seconds = 1 day + includeSubDomains = Browsers will enforce HTTPS for 1 day on the site and all subdomains [OK]

Hint: max-age in seconds; 86400 = 1 day [OK]

Common Mistakes:

• Confusing seconds with days
• Ignoring includeSubDomains effect
• Assuming max-age too low disables HSTS

4. You added this line in nginx:

add_header Strict-Transport-Security max-age=31536000 includeSubDomains always;

Why is the HSTS header not sent to clients?

medium

A. includeSubDomains is not a valid directive

B. The 'always' directive must be inside the quotes

C. max-age value is too large and rejected by nginx

D. The header value is missing quotes, causing syntax error

Solution

1. Step 1: Check syntax for add_header directive

   The header value must be enclosed in quotes. Missing quotes cause nginx to ignore the header.

2. Step 2: Validate other parts

   'always' must be outside quotes, max-age=31536000 is valid, includeSubDomains is valid directive.

3. Final Answer:

   The header value is missing quotes, causing syntax error -> Option D

4. Quick Check:

   Quotes missing = header not sent [OK]

Hint: Always quote header values in add_header [OK]

Common Mistakes:

• Placing 'always' inside quotes
• Not quoting header value
• Misunderstanding valid directives

5. You want to preload your site in browsers' HSTS preload list. Which nginx header configuration is correct to achieve this for 6 months including subdomains?

hard

A. add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;

B. add_header Strict-Transport-Security "max-age=15768000; preload" always;

C. add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload" always;

D. add_header Strict-Transport-Security "max-age=15768000; includeSubDomains" always;

Solution

1. Step 1: Calculate max-age for 6 months

   6 months ≈ 15768000 seconds (6 * 30 * 24 * 3600).

2. Step 2: Include required directives for preload

   Preload requires max-age, includeSubDomains, and preload directive all present.

3. Step 3: Verify syntax correctness

   add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload" always; correctly quotes the value, uses semicolons, includes all directives, and uses 'always;'.

4. Final Answer:

   add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload" always; -> Option C

5. Quick Check:

   Preload + includeSubDomains + 6 months = add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload" always; [OK]

Hint: Preload needs max-age, includeSubDomains, preload keywords [OK]

Common Mistakes:

• Using wrong max-age for 6 months
• Omitting preload directive
• Not quoting header value