Fix finalized for SSL protocol hole

Engineers have signed off on a fix for a potentially serious vulnerability in the SSL, or secure sockets layer, protocol that secures email, web transactions and other types of sensitive internet traffic.

The final draft updates the industry-wide specifications for SSL, which is also referred to as TLS, or transport layer security. Now that the Internet Engineering Task Force has approved it for publishing as a formal standard, it will update RFC 5246, the most recent request for comments that maps out the current SSL protocol.

The new protocol overhauls the way SSL-enabled software renegotiates encrypted sessions so it's no longer possible for attackers to inject malicious payloads into encrypted traffic passing between two endpoints. The vulnerability violated one of the core guarantees provided by SSL by making it possible to perform man-in-the-middle attacks that could steal sensitive data or tamper with secure transactions.

Since the flaw was disclosed in November, many software makers have disabled the renegotiation feature in their programs, a tweak that meant their applications were technically not compliant with official specifications laid out in RFCs that govern SSL. The new protocol provides a longer-term fix by restoring renegotiation capabilities without putting SSL sessions at risk.

Putting the new blueprint into place, however, won't be quick.

"Now that the standard is final, people will need to go back to polish up their implementations and make sure they conform exactly to the standard so they function well," said Steve Dispensa, chief technology officer of PhoneFactor, a provider of two-factor authentication services whose researchers first reported the decades-old bug. "There's still quite a bit of work to be done."

After the vulnerability became public knowledge, many people dismissed it as an oddity that had little practical effect because the conditions under which it could be exploited were extremely limited. But within a few weeks, a Turkish grad student showed how it could be used to steal Twitter authentication credentials. Twitter responded by disabling SSL renegotiation on its site.

With the completion of the specification, SSL libraries will have to be updated to implement the changes. Applications that rely on those libraries will then have to be updated. Dispensa said he's in the process of patching the open-source GNU TLS so it's compliant, and he believes OpenSSL already has done so.

PhoneFactor maintains this status page of SSL patches, and the IETF announcement of the new standard is here. ®