Cross-Origin Opener Policy (COOP)
The Cross-Origin Opener Policy is a relatively new security header introduced by the W3C to mitigate the risks associated with the window.opener attribute. This attribute, when exploited, can lead to unauthorized access and manipulation of a website's functionality. By setting the Cross-Origin-Opener-Policy header, a web server can control which domains are allowed to open its windows, effectively limiting potential vulnerabilities.
In Apache, you can configure the COOP header by adding the following lines to your server configuration file (httpd.conf or virtualhost.conf):
Header always set Cross-Origin-Opener-Policy "same-origin"
Header always set Cross-Origin-Opener-Synthetic "true"
The same-origin value ensures that only pages from the same origin can open the protected windows, while Cross-Origin-Opener-Synthetic is set to true to indicate that the policy is enforced synthetically by the browser rather than being a server-side restriction.
Cross-Origin Resource Policy (CORP)
The Cross-Origin Resource Policy, similar to COOP, aims to restrict access to a website's resources from unauthorized origins. This header, however, focuses on controlling CORS (Cross-Origin Resource Sharing) instead of the window.opener attribute. By setting the Cross-Origin-Resource-Policy header, a web server can specify which domains are allowed or denied to access its resources, such as images, scripts, or stylesheets.
To enable the CORP header in Apache, add the following configuration:
Header always set Cross-Origin-Resource-Policy "same-site"
In this example, the policy is set to same-site, which restricts access to resources from only the same-site origin (i.e., the origin of the document making the request).
Strict Transport Security (HSTS)
Strict Transport Security, also known as HSTS (HTTP Strict Transport Security), is a security feature that enforces the use of HTTPS protocol for a website. By default, many browsers will initially connect to a server using HTTP and only switch to HTTPS if the server provides an https URL or includes an http-equiv meta tag in its HTML headers. HSTS bypasses this mechanism by instructing browsers to always use the HTTPS protocol when accessing a website.
In Apache, HSTS can be configured using the Header directive:
Header always set Strict-Transport-Security "max-age=63072000; includeSubDomains; preload"
The max-age parameter specifies the duration of the HSTS policy in seconds (63072000 corresponds to 2 years). The includeSubDomains directive applies the policy to all subdomains as well. Finally, the preload indicator informs browsers to include the website's HSTS policy in their preload list, which helps prevent man-in-the-middle attacks.
X-Frame-Options
The X-Frame-Options header is used to prevent clickjacking attacks, where an attacker embeds a victim's website in an invisible iframe on a malicious page and tricks users into clicking on the fake content. By setting X-Frame-Options to DENY or SAMEORIGIN, a web server can restrict the framing of its pages.
In Apache, configure X-Frame-Options as follows:
Header always set X-Frame-Options "SAMEORIGIN"
This directive ensures that a page can only be framed from the same origin as the page itself. Setting X-Frame-Options to DENY would completely prohibit framing, while ALLOW-FROM https://allowed.origin would allow framing only from the specified trusted origin.
X-Content-Type-Options
X-Content-Type-Options is a security header that helps prevent content sniffing attacks, where a malicious server sends unexpected content types, and the browser, in the absence of explicit content type information, gladly parses it as something else (e.g., HTML when expecting an image).
To enable this header in Apache, add:
Header always set X-Content-Type-Options "nosniff"
The nosniff value instructs the browser to never override the Content-Type header provided by the server, ensuring that the client respects the intended content type.
Referrer Policy
The Referrer-Policy header controls the referrer information sent by the browser when linking to external resources, such as images, stylesheets, or scripts. By default, the browser includes the full URL of the referring page in the Referer header. However, this can lead to privacy concerns, as it reveals the user's browsing history. A web server can dictate the referrer policy using the Referrer-Policy header.
In Apache, configure Referrer Policy as follows:
Header always set Referrer-Policy "no-referrer"
The no-referrer policy tells the browser not to send any referrer information, effectively keeping the user's browsing history private. Other common policies include origin, same-origin, strict-origin, and strict-origin-when-crossorigin.
Conclusion
Apache security headers offer a robust layer of protection against various web application vulnerabilities. By properly configuring headers like Cross-Origin Opener Policy, Cross-Origin Resource Policy, Strict Transport Security, X-Frame-Options, X-Content-Type-Options, and Referrer Policy, web administrators can significantly strengthen their defenses against attacks like clickjacking, cross-site scripting (XSS), and content sniffing.
Remember to carefully evaluate the settings for each header based on your specific website's requirements and potential impacts on functionality. By adopting these best practices and staying up-to-date with the latest security guidelines, you can help ensure the safety and integrity of your online presence.