Google has launched a vulnerability scanner that only targets two web application flaws by hammering them in a multi-stage attack. While it misses many bugs, the result for developers may be cheaper manual security reviews.
Vulnerability scanners aren’t new, but Google says it’s Cloud Security Scanner is a little different than others. First, the new beta service will miss many of OWASP’s top 10 web application vulnerabilities and it’s designed to do so. It’s also got an emphasis on avoiding false-positives, so may gloss over possible flaws. But that’s exactly what it's meant to do since it is aimed at finding as many of the most common flaws in a web application as possible in the least amount of time.
The only two bugs it targets are cross-site scripting (XXS) flaws and mixed content scripts, which Google argues are the most common App Engine developers face.
“It crawls your application, following all links within the scope of your starting URLs, and attempts to exercise as many user inputs and event handlers as possible,” Google explains.
The new service comes with numerous caveats. The scan may miss sections of an application and Google also warns its actions“may lead to undesirable results”. For example, it may trigger a large number of test emails in an email sign-up page or start posting test strings as comments on a blog application that allows public comments.
Also, the service only supports App Engine instances but not App Engine managed virtual machines, Google Compute Engine or other resources.
But the chief design goals for the scanner were to create an easy to use tool that detects the most common web flaws, as well as support the scanning of HTML5, JavaScript-heavy web applications.
Rob Mann, a Google security engineering manager explained that the scanner cherry picks the best features from using an emulated browser, which is fast but misses certain actions, versus using a real browser, which is slow but more comprehensive.
The answer lies in a probe, followed by a double-pass attack that fires up “a botnet of hundreds of virtual Chrome workers” from its Google Compute Engine that hit the site. .
“First, the scanner makes a high speed pass, crawling, and parsing the HTML. It then executes a slow and thorough full-page render to find the more complex sections of your site,” said Mann,
“While faster than a real browser crawl, this process is still too slow. So we scale horizontally. Using Google Compute Engine, we dynamically create a botnet of hundreds of virtual Chrome workers to scan your site. Don’t worry, each scan is limited to 20 requests per second or lower.”
“Then we attack your site (again, don’t worry)! When testing for XSS, we use a completely benign payload that relies on Chrome DevTools to execute the debugger. Once the debugger fires, we know we have JavaScript code execution, so false positives are (almost) non-existent.”
The scan however is only meant to complement existing secure design and deployment processes. But it may also make it cheaper for developers when they hire a security pro after a quick clean up.
Read more: Relax, that bogus-looking Windows 7 update was a Microsoft stuff-up
This article is brought to you by Enex TestLab, content directors for CSO Australia.
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