Patch for flaw in key Internet protocol

January 15, 2010 by Lin Edwards report
Internet map as of 16th January. Image: Internet Mapping Project, Bell Labs/Lumeta Corporation

( -- A flaw was found in November in a key Internet protocol that encrypts most sensitive online transactions and communications, including credit card and banking transactions. A patch has now been developed by the Internet Engineering Task Force (IETF), but it may take some time to be fully implemented.

The flaw is in the Transport Layer Security (TLS) protocol, which is the IETF term for the Secure Socket Layer (SSL) protocol. SSL/TLS is built into Web servers and browsers to protect sensitive information. The flaw was found by Steve Dispensa and Marsh Ray of an authentication company in Kansas called Phone Factor, and allows an attacker to hijack and insert commands into the start of the encrypted conversation between a web browser and the web server.

The flaw exploits a feature of TLS that allows a to change some parameters of an encrypted session while the session is in progress. This has serious implications, as demonstrated on by one researcher. who demonstrated it could be used to order the server to reveal the victim's password. It could also potentially be used to draw money out of a victim's bank account.

One of the authors of the draft security extension for the protocol, Eric Rescorla, said the flaw in TLS shows how difficult it is to design security protocols to protect communications on the Internet. The flaw could not be exploited without considerable technical knowledge on the part of the attacker, but it is still significant because servers and clients are open to attack even if they have implemented the protocol perfectly.

The IETF has not published its official Request for Comments (RFC) document for the security extension, which is to be known as the TLS renegotiation indication extension, but Ray say the fix is stable and several groups and vendors are working on implementing it.

Deployment of the fix for commercial products that include SSL/TLS will take time because much interoperability testing will be required before vendors can ship it, and it affects a large range of products. As a workaround, most vendors have simply turned off TLS renegotiation, which does not appear to have caused many problems. Some devices, such as printers and webcams will probably never be patched because they are rarely handling critical information that would make a "man-in-the-middle" attack such as this worth worrying about.

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More information: Internet Engineering Task Force:

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3 / 5 (2) Jan 15, 2010
we note that the Diffie-Hellman algorithm also suffers from a risk of a MITM attack, and even though it was fixed with the newer 'Authenticated DH', its STILL not widely implimented/disseminated!!!!
So, how many years will this lil project require!?
not rated yet Jan 15, 2010
As a workaround, most vendors have simply turned off TLS renegotiation, which does not appear to have caused many problems.

Stupid question #68: so why the hell does this feature even exist, if it adds complexity, presents a security risk, yet nobody really uses it for anything worthwhile?

Just get rid of the thing, instead of trying to fix it!
not rated yet Jan 15, 2010
Pink... you are correct that any element of complexity inherently adds a security risk. My guess, not knowing all the details, is this is some old feature that is used for backwards compatibility.
not rated yet Jan 15, 2010

I'd buy the "backwards compatibility" argument, if they didn't state in the article that the feature has been disabled without any major disruption for customers.

Besides, even if there was a backward compatibility concern, for such things there's at least the concept of "deprecation": assert that the feature will go away 5 years from now, so all new devices will omit it while old devices will be retired/replaced by then...

Frankly, in this case it smells to me more like an over-engineered system than anything else. To which my response is always: KISS

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