Yahoo leaks private key, allows anyone to build Yahoo-signed Chrome extensions

Yahoo accidentally leaked the private key that was used to digitally sign its new Axis extension for Google Chrome

Yahoo was forced to release a new version of its Axis extension for Google Chrome after the original one contained a private key that allowed anyone to digitally sign extensions in Yahoo's name.

Axis is a new search and browsing tool from Yahoo that was released on Wednesday. It is available for desktop computers, as an extension for Google Chrome, Mozilla Firefox, Internet Explorer and Safari, as well as for iOS devices, as a stand-alone app.

However, while looking at the source code for the Google Chrome Axis extension, hacker and security blogger Nik Cubrilovic discovered a serious security flaw -- the package included the private cryptographic key used by Yahoo to sign the extension.

"With access to the private certificate file [private key] a malicious attacker is able to create a forged extension that Chrome will authenticate as being from Yahoo," Nik Cubrilovic said in a blog post on Thursday.

Google Chrome extensions come packed as CRX files, which are essentially digitally signed ZIP-format archives.

Every CRX file contains a public key that's part of a private-public key pair unique to its creator. The private key is used to sign the extension, while the public key is used by the browser to verify the signature's authenticity.

Since private keys allow developers to digitally sign new extensions or update their old ones, they should always be kept secret.

In order to prove the implications of the private key leak, Cubrilovic created a proof-of-concept Chrome extension that displays an alert on every visited website and signed it with Yahoo's private key.

An attacker can push a Yahoo-signed malicious extension to a browser that has the Axis extension installed, by using techniques like DNS spoofing, Cubrilovic said.

Google Chrome automatically checks for extension updates by querying update URLs specified by developers. If attackers can forge the DNS (domain name system) responses received by the browser, they can force it to install a rogue digitally signed extension update from a server under their control.

Yahoo confirmed the security issue. "We worked quickly to resolve the issue and have issued a new Chrome plug-in," a Yahoo spokeswoman said via email. "Users who downloaded Yahoo! Axis on Chrome between the hours of 6-9 p.m. Pacific Time on May 23, 2012, are encouraged to uninstall the previous version and reinstall the new version at axis.yahoo.com."

Join the PC World newsletter!

Error: Please check your email address.

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Essentials

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

Budget

Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?