📌 Subresource Integrity (SRI) Summary

Subresource Integrity (SRI) is a security feature that helps ensure files loaded from third-party sources, such as JavaScript libraries or stylesheets, have not been tampered with. It works by allowing website developers to provide a cryptographic hash of the file they expect to load. When the browser fetches the file, it checks the hash. If the file does not match, the browser refuses to use it. This helps protect users from malicious code being injected into trusted libraries or resources.

🙋🏻‍♂️ Explain Subresource Integrity (SRI) Simply

Imagine you order a new phone online and the shop tells you the exact weight it should be. When it arrives, you weigh it. If the weight is wrong, you know something is off and do not use it. SRI works the same way for website files, checking that what you get is exactly what you expected.

📅 How Can it be used?

Subresource Integrity can be used to secure third-party scripts on your website, preventing compromised files from running.

🗺️ Real World Examples

A web developer links to a popular JavaScript library like jQuery from a CDN. They add an SRI hash to the script tag. If an attacker tries to alter the library on the CDN, the browser detects the change and blocks the script, keeping the website safe.

A company embeds a CSS framework from an external source in its customer portal. By including an SRI attribute with the correct hash, the browser ensures the stylesheet has not been modified before applying it, protecting the site’s appearance and user experience.

✅ FAQ

Subresource Integrity, or SRI, is a way to make sure that files like scripts and stylesheets loaded from other websites have not been changed by anyone with bad intentions. It helps protect both the website and its visitors from harmful code by checking if the file matches a known signature. If something is not right, the browser will block the file, keeping the site safer.

When you use SRI, you add a special code called a hash to your script or link tag. This hash is like a fingerprint for the file. The browser checks the downloaded file against this fingerprint. If everything matches, the file loads as normal. If it does not, the browser will stop the file from running, so only safe files are used.

Yes, you do. If the file you are linking to is updated or changed, its fingerprint will also change. You will need to update the SRI hash in your website code so that the browser knows what to expect. If you forget, the browser will block the file because it thinks something might be wrong.

📚 Categories

• Cybersecurity
• InfoSec
• Network Security

🔗 External Reference Links

Subresource Integrity (SRI) link

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