Understanding Strict-Transport-Security (HSTS)

What is Strict-Transport-Security?

The Strict-Transport-Security (HSTS) HTTP response header is a critical security mechanism used to enforce secure connections (HTTPS) between the browser and the server. It helps protect web applications from man-in-the-middle (MITM) attacks and protocol downgrade attacks by ensuring that all communication occurs over HTTPS.

 

How Strict-Transport-Security Works?

1. When a browser receives an HTTP response with the Strict-Transport-Security header, it remembers the directive for a specified duration (max-age).
2. For the specified duration, all subsequent requests to the server are automatically upgraded to HTTPS, even if the user enters http:// in the browser.
3. The browser rejects any attempts to connect to the server using an insecure connection.

 

HSTS Header Syntax

The header is included in the HTTP response as:

 

HSTS Header Directives

1. max-age: Specifies the duration (in seconds) for which the browser should enforce HTTPS.
   For example: max-age=31536000 (1 year)
2. includeSubDomains (optional): Ensures HSTS is applied to all subdomains.
3. preload (optional): Indicates the domain should be preloaded into browsers that maintain an HSTS preload list.

 

Benefits of HSTS

• Prevents Downgrade Attacks: Attackers cannot force a connection over HTTP by downgrading from HTTPS.
• Mitigates MITM Attacks: Ensures the connection is encrypted and authenticated.
• Improves User Trust: Guarantees that users access the website securely.

 

How to Implement HSTS

1. Apache: Add the following line to the .htaccess file or server configuration
   
2. Nginx: Add the following directive to your configuration file
   
3. IIS: Configure the HTTP response headers to include
   

 

References

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security