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Chrome exploit catches video just after it's decrypted for video pirates

FOR YEARS HOLLYWOOD has waged a war on piracy, using digital rights management technologies to fight bootleggers who illegally copy movies and distribute them. For just as long, hackers have found ways to bypass these protections. Now two security researchers have found a new way, using a vulnerability in the system Google uses to stream media through its Chrome browser. They say people could exploit the flaw to save illegal copies of movies they stream on Chrome using sites like Netflix or Amazon Prime.

David Livshits from the Cyber Security Research Center at Ben-Gurion University in Israel and Alexandra Mikityuk with Telekom Innovation Laboratories in Berlin, Germany, alerted Google to the problem on May 24th, but Google has yet to issue a patch. The vulnerability exists in the way Google implements the Widevine EME/CDM technology that Chrome uses to stream encrypted video.

The researchers created a proof-of-concept executable file that easily exploits the vulnerability, and produced a brief video to demonstrate it in action.

The investigators aren't saying exactly how the technique works until and unless there's a patch. However, they describe it as relatively simple. It has likely been around ever since Google implemented Widevine in Chrome, they add.

This isn't new, DivX player uses to download videos/movies to one's hard drive when streamed using chrome or safari automatically.

DRM Hole
The problem is with the implementation of a digital management system called Widevine, which Google owns but did not create. It uses encrypted media extensions to allow the content decryption module in your browser to communicate with the content protection systems of Netflix and other streaming services to deliver their encrypted movies to you. EME handles the key or license exchange between the protection systems of content providers and a CDM component in your browser. When you choose a protected movie to play, the CDM sends a license request to the provider through the EME interface and receives a license in return, which allows the CDM to decrypt the video and send it to your browser player to stream the decrypted content.

A good DRM system should protect that decrypted data and only let you stream the content in your browser, but Google’s system lets you copy it as it streams. The point at which you can hijack the decrypted movie is right after the CDM decrypts the film and is passing it to the player for streaming.

Firefox and Opera also use the Widevine CDM, though the researchers haven’t examined those browsers yet. They limited their research to the desktop version of Chrome. Neither Safari nor Internet Explorer use Widevine. Safari uses Apple’s FairPlay CDM, and Microsoft’s Internet Explorer and Edge browsers use Microsoft’s PlayReady CDM. The researchers haven’t examined those CDMs yet.

Source: Wired, Ben-Gurion University (YouTube)

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