by Daniel Peck, Research Scientist
Yesterday reports began to trickle in that Google users in Iran were victim to a man-in-the-middle attack through the use of an illegitimate SSL certificate issued for “*.google.com”. This is the latest in a series of events involving a hacked Certificate Authority, but this time there was clear evidence that the fake certificate was being actively used. Details of the attack and consequences are being written about extensively elsewhere, so we will give a brief overview and link to those directly involved and others with particularly insightful analysis.
The certificate being used was issued by a Dutch certificate authority, DigiNotar. The consequence is that this CA has essentially been given the “death penalty”. Microsoft, Mozilla and Google have removed the DigiNotar root certificate from their chain of trust and certificates signed by them will have no more trust than one you generate yourself. It is good to see that those who have the strongest position when choosing which certificate authorities to trust are doing the right thing here, with a technology that so many people rely on for security, privacy and economic reason a “one strike and you're out” system is appropriate. With each attack similar to this one, we see that the current system of Certificate Authorities is quite open to abuse with the combination of centralized and opaque trust. Compromises of that trust can have severe consequences. The system is clearly broken, and while some are working on replacement solutions, it is what we have to use in the mean time.
Users are advised to remove the DigiNotar root certificate.
Some newer versions of Windows seem to be automatically checking a CRL and therefore are able to provide protection without a software update: “All supported editions of Windows Vista, Windows 7, Windows Server 2008, and Windows Server 2008 R2 use the Microsoft Certificate Trust List to validate the trust of a certificate authority. There is no action required for users of these operating systems because Microsoft has removed the DigiNotar root certificate from the Microsoft Certificate Trust List.”
However older versions of Windows do not provide automatic protection:” Microsoft will release a future update to address this issue for all supported editions of Windows XP and Windows Server 2003.”
The DigiNotar root will be being removed from relevant Barracuda Networks products.
Google Online Security Blog: An Update on Attemped Man-in-the-Middle Attacks
DigiNotar Response: Diginotar Reports Security Incident
Tools/Possible SSL Alternatives for advanced users: