Firefox adds protection against rogue SSL certificates

Mozilla has added a defense in its latest version of Firefox that would help prevent hackers from intercepting data intended for major online services.

The feature, known as certificate key pinning, allows online services to specify which SSL/TLS (Secure Sockets Layer/Transport Security Layer) certificates are valid for their services. The certificates are used to verify a site is legitimate and to encrypt data traffic.

The idea is to prevent attacks such as one that affected Google in 2011, targeting Gmail users. A Dutch certificate authority (CA), Diginotar, was either tricked or hacked and issued a valid SSL certificate that would work for a Google domain.

In theory, that allowed the hackers to set up a fake website that looked like Gmail and didn’t trigger a browser warning of an invalid SSL certificate. Security experts have long warned that attacks targeting certificate authorities are a threat.

Certificate pinning would have halted that kind of attack, as Firefox would have known Diginotar shouldn’t have issued a certificate for Google.

In Firefox 32, “if any certificate in the verified certificate chain corresponds to one of the known good (pinned) certificates, Firefox displays the lock icon as normal,” wrote Sid Stamm, senior manager of security and privacy engineering at Mozilla, on a company blog.

“When the root cert for a pinned site does not match one of the known good CAs, Firefox will reject the connection with a pinning error,” he continued.

The “pins” for the certificates of online services have to be encoded into Firefox. Firefox 32, released this week, supports Mozilla sites and Twitter. Later Firefox releases will support certificate pinning for Google sites, Tor, Dropbox and others, according to a project wiki.

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