HSTS header in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does HSTS stand for and what is its main purpose?

HSTS stands for HTTP Strict Transport Security. Its main purpose is to tell browsers to only connect to a website using HTTPS, improving security by preventing insecure HTTP connections.

beginner

How do you enable HSTS in an nginx server configuration?

You add the header Strict-Transport-Security in the server block for HTTPS, for example: <br>

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

beginner

What does the max-age directive in the HSTS header control?

The max-age directive sets how long (in seconds) the browser should remember to only use HTTPS for the site. For example, max-age=31536000 means 1 year.

intermediate

What is the effect of adding includeSubDomains in the HSTS header?

Adding includeSubDomains tells browsers to apply the HSTS policy to all subdomains of the site, not just the main domain.

intermediate

Why should the HSTS header be sent only over HTTPS connections?

Because HSTS tells browsers to only use HTTPS, sending it over HTTP would be insecure and could allow attackers to intercept or strip the header.

What is the correct nginx directive to add the HSTS header?

A add_header HSTS "max-age=31536000; includeSubDomains";

B set_header Strict-Transport-Security "max-age=31536000; includeSubDomains";

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

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

The correct nginx directive is add_header with the full header name Strict-Transport-Security and the value including max-age and optionally includeSubDomains. The always flag ensures it is added on all responses.

What does the max-age value in the HSTS header represent?

A The number of subdomains to include

B The number of seconds the browser should enforce HTTPS only

C The number of requests allowed over HTTP

D The timeout for HTTPS connections

max-age sets the time in seconds that the browser remembers to only use HTTPS for the site.

Why is it important to include includeSubDomains in the HSTS header?

A To apply HSTS policy to all subdomains as well

B To exclude subdomains from HSTS

C To enable HTTP connections on subdomains

D To disable HTTPS on subdomains

Including includeSubDomains tells browsers to enforce HTTPS on all subdomains, improving overall security.

What happens if you send the HSTS header over an HTTP connection?

A It can be intercepted or stripped by attackers

B It forces the browser to use HTTPS immediately

C It disables HTTPS for the site

D It has no effect

Sending HSTS over HTTP is insecure because attackers can intercept or remove the header, defeating its purpose.

Which of these is a valid HSTS header value?

A "max-age=31536000; excludeSubDomains"

B "max-age=one year; includeSubDomains"

C "max-age=31536000; includeSubDomains"

D "max-age=0; includeSubDomains"

The value must use seconds for max-age and can include includeSubDomains. "one year" is invalid, and excludeSubDomains is not a valid directive.

Explain how to configure the HSTS header in nginx and why it is important.

Think about telling browsers to always use HTTPS and how nginx sends headers.

Describe the risks of not using HSTS on a website that supports HTTPS.

Consider what happens if browsers are allowed to connect over HTTP.