Friday, November 6, 2009

Major SSL Flaw Find Prompts Protocol Update

Via DarkReading -

The Internet Engineering Task Force (IETF) is about to issue a proposed extension to Secure Sockets Layer (SSL) that addresses a major vulnerability in the protocol that was inadvertently disclosed publicly late yesterday -- a flaw that affects browsers, servers, smart cards, VPN products, as well as many lower-profile products that contain the protocol embedded in their firmware.

Marsh Ray, who first discovered the bug in August, has been working with the IETF, vendors including Google and Mozilla, and members of the Industry Consortium for the Advancement of Security on the Internet (ICASI) on a fix since last month. He says he expects the IETF to issue a proposed extension to its specification for SSL, known as Transport Layer Security (TLS) in IETF parlance, as early as today. Software vendors that use SSL can then create patches for the vulnerability.

"The bug results in a set of related attacks that allow a man-in-the-middle to do bad things to your SSL/TLS connection. The [attacker] in the middle is able to inject his own chosen text into what your application believes is an encrypted, secure communications channel," says Ray, a senior software development engineer for PhoneFactor. "This has implications for all protocols that run on top of SSL/TLS, such as HTTPS."


SSL has been under siege during the past year, with the groundbreaking man-in-the-middle hack by researcher Moxie Marlinspike, which dupes a user into thinking he's in an HTTPS session when in reality he has been taken elsewhere by the attacker, as well as Kaminsky's research exposing critical flaws in X.509 certificate technology used in SSL.

But this latest threat resides within the SSL protocol itself and will require fixes to browsers, Web servers, database servers, mail servers, SQL servers, smart cards, and other SSL-based software. "All the [SSL] attacks I've seen [recently] have been around the client or server software, or the way it handles a certificate," Ray says. "What's different with this [bug] is that both the client and server need to be patched to restore the full security guarantees that are expected with TLS."

Marlinspike maintains that the newly found SSL flaw is not earth-shattering. "The sky is not falling," he says. "This was some clever work, and it is interesting for those of us who are into secure protocols, but I have yet to see an example of how this could significantly impact the way that SSL/TLS is commonly deployed in ways that differ from simple CSRF [cross-site request forgery]."


This SSL bug is still pretty new and many questions remain about exactly which software platforms and protocols are vulnerable.

In the coming weeks, as tools, POCs and more research comes to the surface, the community as a whole will have a better picture of the overall threat.

Here are two great blog entries on the new SSL bug...
Understanding the TLS Renegotiation Attack
Thoughts on the TLS Bug

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