Updated Google says security biz MCS Holdings has created unauthorized SSL certificates for some Google-owned websites.
Anyone with these dodgy certificates could, in theory, set up a web server that masquerades as a legit Google site, and redirect people to the fake site by hijacking their DNS. Chrome and the latest Firefox web browsers should detect the interception, and refuse to talk to the server, but other browsers may have continued to the bogus websites none the wiser, allowing passwords, emails, and other details to slip into the wrong hands.
MCS is an intermediate certificate authority based in Egypt. The dodgy Google certificates could be sold to corporate IT departments, allowing admins to intercept and inspect employees' encrypted internet traffic to Google servers while at work. There is no suggestion at this stage that the certificates were used for malicious purposes.
The Google certs were crafted using an intermediate certificate issued by the major Chinese certification authority CNNIC, which is trusted by browsers and operating systems.
If you or I were to create a gmail.com SSL certificate, and plonk it on a website dressed up to look like a Gmail login page, no browser would trust it because it is disconnected from the chain of trust that holds the world of SSL together – the HTTPS connection would be rejected. But in the case of MCS, the Google domain certs were ultimately backed by a trusted authority – CNNIC. It's feared MCS has issued certs for other websites so bosses can snoop on staff; the ease at which bogus certificates can be issued, and perhaps stolen and used in the wild, concerns security experts.
"CNNIC is included in all major root stores and so the mis-issued certificates would be trusted by almost all browsers and operating systems," Google security engineer Adam Langley blogged.
"Chrome on Windows, OS X, and Linux, ChromeOS, and Firefox 33 and greater, would have rejected these certificates because of public-key pinning, although mis-issued certificates for other sites likely exist."
Google spotted the problem on March 20, and alerted the Chinese cert body, which dealt with the issue on March 22 by revoking MCS' intermediate certificate. Google and Firefox-maker Mozilla have instructed their software to reject the dodgy certificates.
"We have no indication of abuse and we are not suggesting that people change passwords or take other action," Langley said. "At this time we are considering what further actions are appropriate." ®
Updated to add
MCS has said in a statement "the reported issue is a human mistake that took place unintentionally through a single PC inside MCS Lab which had been dedicated for testing purposes."