Search Console’s Shared Array Buffer warnings: Clarifying a new cross-origin isolation security policy

After Spectre forced a multiyear security blackout on the functionality until new security criteria were in place, Android Chrome 88 and desktop Chrome 91, as well as Firefox 79+, now implement SharedArrayBuffers again.

As we fight hackers attempting to steal company secrets, web-facing pages have become a battleground for information security. Modern websites frequently make use of resources from multiple sources (domain). Vulnerabilities may arise as a result of this. Webmasters have a growing range of alternatives from browser makers, including guidelines for handling “security concerns that influence new features. As pressure rises around security concerns that affect new features. cross-origin” resources to aid in the prevention of data leaks.

Security measures

You may be familiar with rel=” no opener,”. A method of ensuring that outbound actions on a page are hypertext links and form elements. Such as links that open another site in a new browser tab, would not allow Javascript on an external page to access an internal page via the Window. opener attribute. Consider opening a new tab after clicking a link. The original page was covertly switched to one containing phishing lures when you closed the new tab. The opener feature allows attackers to modify the original tab’s URLs.

 

“I would never connect to a page that does that!” you might be thinking. We don’t have time to check out source code because we frequently link out to a lot of pages at SEL. We don’t have to because we use rel=”no opener.” Browser makers provide sophisticated security features so that we may lock things down in a variety of ways to avoid being susceptible to assaults like this.

 

The Cross-Origin-Resource-Sharing (CORS) HTTP response header may have been mentioned. When you don’t have control over your web server, this is more difficult to manage.CORS (Access-Control-Allow-*) values will restrict access to a list of domains you specify. When you use CORS and include analytics, advertisements, and other third-party script resources on your page, those that aren’t specifically on an allow list will be blocked, resulting in browser console error messages.

Spectre meltdown

When things get too hot, it’s safer for browser developers to disable a function entirely. That’s exactly what happened with Shared Array Buffers. A few years ago when it was disabled by default six months after its introduction and until a solution was proposed and agreed upon by consensus lately. The problem was that a proof of concept post was published which demonstrated a “side-channel” vulnerability accessing kernel memory, a more serious problem than URL switching.

 

In a nutshell, a large set of CPUs are vulnerable to Spectre side-channel attacks by virtue of performance-boosting “speculative execution” of low-level code with access to hardware resources. Speculative execution anticipates instructions and rushes to carry them out before they arrive. That would be fantastic if it didn’t use a kernel-mode process! The vulnerability is caused by programme code being executed in kernel mode rather than user mode.

SharedArrayBuffers API commands can fool speculative execution into allowing malware-infected page access to normally protected kernel memory. This includes all of your other pages, not only those launched by following a link from one to another but any page open in your browser. It can also be duped into handing up passwords, encryption keys, and personally identifiable information to be used in other attacks.

 

Consider bookmarking a personal banking page with your account information open. Then viewing a page that unfortunately contains the vulnerability on its own. Any page on the banking page, as well as any other page, can be retrieved by an attacker. Information leaked as a result of such an assault can include highly sensitive, personally identifying information that can lead to identity theft and enable targeted attacks on companies, including government systems.

Return of Shared Array Buffers

After a new security policy mitigated the danger of access to private memory, Google’s Android Chrome 88 and desktop Chrome 91, as well as Firefox 79+, have all reintroduced SharedArrayBuffers. Any resource that isn’t explicitly listed in your “allowed” list will be blocked. Since the functionality was turned off by default, JavaScript APIs that used it are now triggering blocking actions when they had previously failed silently.

WebGLRenderingContext, for example, implements SharedArrayBuffers, which failed quietly during the blackout. Because the security settings to handle it are so new, few developers are aware of it. The unexpected appearance of notifications in Google Search Console can take us off guard as complaints of blocking actions mount up at Google.

Implementing the new security policy

There has never been a better time to start working on a CORS policy. Third-party resources are already causing enough mayhem without a security strategy in place, let alone the possibility of exposing your secrets. Only include third-party resources on a page that you intend to use. To reduce your risk, you should always “distrust by default” all resources. Then, as few domains, as you can get away with, white-list them.

Some Content Delivery Networks (CDNs) allow you to update response headers on the fly if you don’t operate your own web server. It’s a simple issue of adding field names and values, one directive per line, in either case. The SEO expert can leverage a conversation sparked by a site evaluation report to raise concerns about third-party resource inclusions, allowing them to compile a more refined list for the host’s web server administrator.

Cross-origin isolation

The use of SharedArrayBuffers necessitates a secure environment in which one or more response header directives are used to restrict access. The strategy in question is known as cross-origin isolation. You’ll need to add two new page headers, COOP and COEP, to set up Cross-Origin Isolation (as depicted below). Which function in conjunction with one or more other security headers, such as CORS and or CORP, to deliver your white-listed cross-origin domains alone or in combination.

Cross-Origin-Opener-Policy: same-origin

Cross-Origin-Embedder-Policy: require-corp

Have you seen the policy on Openers? In order for one page to access the Window. opener attribute of another, the same-origin value necessitates matching domains. Because the HTTP response header policy will prohibit external access to the Window. In the opener, you can safely create external “tab-opening” _blank target links without rel=”no opener.”

Using reports for debugging

You can use the Chrome reporting API to collect statistics for actions that violate certain security regulations. It’s the same one that Google employs. Google may warn you if a large number of blocking events are triggered by your web pages. As is the case if you use Google Search Console. A Chrome-specific Report-To page header field can also be utilised to send data to your own repository separately.

During development, it’s significantly easier to just verify the boolean state of the experimental WindowWorkerGlobalScope API’s crossOriginIsolated property. As a result, you’ll be able to address these concerns straight from your development workflow.

if(crossOriginIsolated) {

// Post SharedArrayBuffer

console.log(“CrossOriginIsolation: true”)

} else {

// Do something else

console.log(“CrossOriginIsolation: false”)

}

Why we care

Given that failing security policies currently result in alerts in Lighthouse, Search Console, and error messages in browser consoles. We need to know the specifics in order to provide recommendations. When we’re doing our own web development. We want to have precise information ready so that we may lead or oversee the deployment of a patch as part of our work.

For further technical knowledge, attend SMX’s SEO for Developers Workshop. Which is designed to provide a forum for discussing challenges that are specific to search engine optimization practitioners. We illustrate what SEO-savvy web developers do in situations like these in a live-code workshop setting. Information security is crucial, as proven by SharedArrayBuffers, cookie policy changes, and a slew of other issues that are most certainly right around the corner.

Postscript.

On Friday, March 19th, Google published a clarification on this message.

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