Jul 19, 20213 min read

HTTP Security Headers: 5 important Security headers for your site

When a user visits a site through his/her browser, the server responds with HTTP Response Headers. These headers tell the browser how to behave during communication with the site. These headers mainly comprise of metadata.

Headers are part of the HTTP specification, defining the metadata of the message in both the HTTP request and response. While the HTTP message body is often meant to be read by the user, metadata is processed exclusively by the web browser and has been included in HTTP protocol since version 1.0.

In request messages, the metadata can hold the following information:

Language of the request
Cookies
Credentials for the website
Cache data

In response messages, the metadata can hold the following information:

Size and type of the content
Cache storage preferences
Server data
Time and date
Credentials to be set by the client

Security headers are HTTP response headers that define whether a set of security precautions should be activated or deactivated on the web browser.

5 Important Security Header for your site:

1. HTTP Strict transport Security (HSTS)

HTTP Strict Transport Security (HSTS) is a web server directive that informs user agents and web browsers how to handle its connection through a response header sent at the very beginning and back to the browser.

This sets the Strict-Transport-Security policy field parameter. It forces those connections over HTTPS encryption, disregarding any script's call to load any resource in that domain over HTTP. HSTS is but one arrow in a bundled sheaf of security settings for your web server or your web hosting service.

Syntax:

Strict-Transport-Security: max-age=<expire-time>

Strict-Transport-Security: max-age=<expire-time>; includeSubDomains

Strict-Transport-Security: max-age=<expire-time>; preload

2. Content Security Policy (CSP)

Content Security Policy presents an extra layer of security against multiple vulnerabilities such as XSS, Clickjacking, Protocol Downgrading and Frame Injection. It appears that CSP will become the most significant tool for client side security in the near future, since it provides a substitute for security headers, such as X-Frame-Options and X-XSS-Protection, that aren’t enabled by default.

Syntax:

Content-Security-Policy: <policy-directive>; <policy-directive>

In CSP, we use a whitelist to define rules. With this approach, we can filter out any resources that do not fit with our rules. All we have to do is to state the resources within the Content-Security-Policy response header:

Content-Security-Policy: script-src 'self' https://apis.google.com

3. Cross Site Scripting Protection (X-XSS)

X-XSS-Protection allows developers to change the behavior of the Reflected XSS (Cross-Site Scripting) security filters. These filters aim to detect dangerous HTML input and either prevent the site from loading or remove potentially malicious scripts.

Reflected XSS is a vulnerability that arises from the evaluation of user input as script code in the page context.

Malicious actions – such as stealing users' cookies, tracking keyboard strokes or mouse moves, or issuing requests on behalf of the user – can all be carried out with the help of XSS. This is how it works.

Consider the following PHP code:

<p>Welcome <?php echo $_GET["name"];?></p>

By passing the following HTML and JavaScript code to the name parameter, the application will embed it unfiltered on the page, which will display a JavaScript alert window on the vulnerable website.

http://www.example.com?name=<script>alert(1);</script>

Syntax:

X-XSS-Protection: 0

X-XSS-Protection: 1

X-XSS-Protection: 1; mode=block

X-XSS-Protection: 1; report=<reporting-uri>

4. X-Frame - Options

In the Orkut era, a spoofing technique called ‘Clickjacking’ was pretty popular. It still is. In this technique, an attacker fools a user into clicking something that isn’t there. For example, a user might think that he’s on the official Orkut website, but something else is running in the background. A user may reveal his/her confidential information in the process.

X-Frame-Options help guard against these kinds of attacks. This is done by disabling the iframes present on the site. In other words, it doesn’t let others embed your content.

Syntax:

X-Frame-Options: DENY

X-Frame-Options: SAMEORIGIN

X-Frame-Options: ALLOW-FROM https://example.com/

5. X-Content - Type Options

This HTTP header is typically used to control the MIME Type Sniffing function in web browsers. MIME Type Sniffing is a content evaluation function used by browsers when the content type is not specified. Basically, if the Content-Type header is blank or missing, the browser 'sniffs' the content and attempts to display the source in the most appropriate way.

However, if used in conjunction with an upload functionality, this sniffing process can pose some risks, so developers should be really careful how to use this header. Below is an example highlighting the security risk.

Syntax: